GB1586188A - Creation of Inventions and Patents with Artificial Intelligence

GB1586188A – Optical system
– Google Patents

GB1586188A – Optical system
– Google Patents
Optical system

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Publication number
GB1586188A

GB1586188A
GB21576/77A
GB2157677A
GB1586188A
GB 1586188 A
GB1586188 A
GB 1586188A
GB 21576/77 A
GB21576/77 A
GB 21576/77A
GB 2157677 A
GB2157677 A
GB 2157677A
GB 1586188 A
GB1586188 A
GB 1586188A
Authority
GB
United Kingdom
Prior art keywords
optical system
lens
base plane
zone
zones
Prior art date
1977-05-23
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)

Expired

Application number
GB21576/77A
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)

Koninklijke Philips NV

Original Assignee
Philips Gloeilampenfabrieken NV
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
1977-05-23
Filing date
1977-05-23
Publication date
1981-03-18

1977-05-23
Application filed by Philips Gloeilampenfabrieken NV
filed
Critical
Philips Gloeilampenfabrieken NV

1977-05-23
Priority to GB21576/77A
priority
Critical
patent/GB1586188A/en

1981-03-18
Publication of GB1586188A
publication
Critical
patent/GB1586188A/en

Status
Expired
legal-status
Critical
Current

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Classifications

G—PHYSICS

G02—OPTICS

G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings

G02B6/24—Coupling light guides

G02B6/42—Coupling light guides with opto-electronic elements

G02B6/4298—Coupling light guides with opto-electronic elements coupling with non-coherent light sources and/or radiation detectors, e.g. lamps, incandescent bulbs, scintillation chambers

G—PHYSICS

G02—OPTICS

G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

G02B3/00—Simple or compound lenses

G02B3/10—Bifocal lenses; Multifocal lenses

G—PHYSICS

G02—OPTICS

G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings

G02B6/24—Coupling light guides

G02B6/42—Coupling light guides with opto-electronic elements

G02B6/4201—Packages, e.g. shape, construction, internal or external details

G02B6/4204—Packages, e.g. shape, construction, internal or external details the coupling comprising intermediate optical elements, e.g. lenses, holograms

G02B6/4206—Optical features

H—ELECTRICITY

H01—ELECTRIC ELEMENTS

H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10

H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00

H01L2224/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, “first-level” interconnects; Manufacturing methods related thereto

H01L2224/42—Wire connectors; Manufacturing methods related thereto

H01L2224/47—Structure, shape, material or disposition of the wire connectors after the connecting process

H01L2224/48—Structure, shape, material or disposition of the wire connectors after the connecting process of an individual wire connector

H01L2224/481—Disposition

H01L2224/48151—Connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive

H01L2224/48221—Connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive the body and the item being stacked

H01L2224/48245—Connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive the body and the item being stacked the item being metallic

H01L2224/48247—Connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive the body and the item being stacked the item being metallic connecting the wire to a bond pad of the item

H—ELECTRICITY

H01—ELECTRIC ELEMENTS

H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10

H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00

H01L2924/15—Details of package parts other than the semiconductor or other solid state devices to be connected

H01L2924/181—Encapsulation

H—ELECTRICITY

H01—ELECTRIC ELEMENTS

H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10

H01L33/00—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof

H01L33/48—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor body packages

H01L33/52—Encapsulations

H01L33/54—Encapsulations having a particular shape

Description

(54) OPTICAL SYSTEM
(71) We, N.V. PHILIPS’ GLOEILAMPENFABRIEKEN, a limited liability Company, organised and established under the laws of the Kingdom of the Netherlands, of Emmasingel 29, Eindhoven, the Netherlands, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:
The invention relates to an optical system comprising a dome-shaped lens for modifying the multi-directional emission distribution of a light source located substantially in the central area of a notional base plane of the lens, into a distribution exhibiting a comparatively high axial intensity. The notional base plane of the lens is herein defined as a notional reference plane transverse to the lens axis, and having at least its central portion so located with respect to the lens that light emanating from said central portion can pass without being deviated by refraction between the base plane and the domed surface of the lens.
The invention more particularly relates to a small optical system which is adapted to co-operate with a light-emitting diode, so as to constitute a unitary assembly which can be used for remote control of, in particular, a television receiver.
Light-emitting diodes are generally provided with a magnifying and/or diffusing optical system, made of one or several plastics materials with indices of refraction between 1.4 and 1.6, which optical system at the same time provides mechanical protection.
Such optical systems are often simply hemispherical, the light-emitting crystal being placed in the median area of a base plane which passes through and occupies the vicinity of the centre of the hemisphere. In this case the linear magnification is small and the light-emission distribution is hardly any more concentrated than in the absence of the optical system.
However, most of the light emitted by the crystal emerges from the optical system, regardless of the emission angle (except for the part of the light which is absorbed by the material of the optical system); indeed, the angle of incidence on the surface separating said optical system and the medium at the outside is always smaller than the critical angle, even for the marginal rays which are emitted from the periphery of the crystal and by the edge of said crystal, which rays are remote from the principal axis of the optical system.
If it is desired to increase the linear magnification and to make the light beam more directional so that it has a greater axial range, the crystal has to be moved away from the hemispherical refracting surface, i.e. shifted along the principal axis in the direction of the object focus; the linear magnification, the directivity, and the axial range will all increase as the crystal is moved away from the centre of curvature of the hemisphere. In practice this is realized by elongating the refractive part of the optical system bounded by the hemispherical surface, by a coaxial cylindrical portion, preferably having the same radius as the other portion, in whose base plane, i.e. of the cylindrical portion, the crystal is then arranged.
This solution has the advantage of being simple and enables the unitary character of the assembly to be maintained. The assembly thus formed, however, has the drawback of exhibiting dead emission angles for which the light intensity, if not zero, is at least substantially attenuated. If the spherical emission surface of such an assembly (provided with a multidirectional emission crystal which emits through its face and through its edge, and with a transparent optical system which leaves the crystal visible) is observed from different angles with respect to the optical axis, three distinct zones are distinguishable starting from the apex, which is situated on the axis, to one side at approximately 90″ from said axis: a first zone in which the light intensity is substantial; subsequently, upwards from a given angle and varying from one assembly to another inaccordance with the physical and geometric characteristics of the relevant assembly, a zone of quasi-extinction – i.e. the dead-angle zone – in which the crystal is no longer visible or is only partly visible; and next, as the angle of observation becomes substantial, again a light zone, this light emerging from the side walls of the cylindrical part of the optical system.
The dead angle zone corresponds to light rays which after leaving the crystal are incident on the surface of the optical system at an angle which is greater than the critical angle, are consequently totally internally reflected and cannot emerge in the direction of the dead zone.
It will be evident that these are the light rays issuing from the periphery of the crystal which hit the surface of the hemisphere at the greatest angle of incidence and which consequently are totally internally reflected first.
In practice this reflection corresponds to an apparent reduction of the emission area of the crystal, which is soon perceivable when the device is observed obliquely relative to its principal axis. The Applicant has for example measured that for an assembly which comprises an emission crystal with a surface area which is equal to substantially 1/100 of the surface area of the base of a plano-convex optical system made from a material with an index of refraction of n = 1.53, which system comprises a cylindrical portion of approximately 1.9 mm height on which a hemispherical portion is superimposed having a radius of curvature of approximately 2.5 mm, the crystal became less visible as soon as the hemisphere was observed at an angle of approximately 22 relative to the principal axis of the optical system.
Only 5 5 % of the light energy emitted by the crystal can emerge from this assembly.
The reflection loss, to which inevitably further losses resulting from aberrations are added, is generally inefficient, particularly when an assembly is to be devised which is suitable for use in a remote control arrangement. In a remote control arrangement it is desirable to have the longest possible range along the axis and around the axis, but preferably also to have a range which is significant at a sufficiently large angle relative to said axis; thus in forming the control beam, the directivity should not be made too great so that medium distance control can be relatively non-critical to enable control to be possible over a relatively wide angle. Of course, it is also necessary to have sufficient luminous energy under all circumstances.
The problem of remote control by means of light-emitting diodes, is therefore particularly difficult to solve because, owing to the low luminous power of such sources, it is necessary to derive the utmost efficiency from the optical system associated with the source, i.e. to reduce or eliminate unwanted total internal reflection without increasing the aberrations. This problem becomes even more difficult to solve in the case of sources whose lateral emission is substantial relative to the axial emission. Therefore, an attempt has been made to use those light-emitting sources which radiate the greatest total amount of luminous energy, such as diodes of the epitaxial type which emit not only from their faces but also from their edges, rather than diffused diodes whose emission surface is generally located in a limited region within the effective surface of the crystal.
It is an object of the invention to provide an optical system which can concentrate the emission of a light-emitting diode which emits both from the front and from the edges, the shape of said optical system being arranged so as to reduce or minimize those internal reflections which are liable to restrict the available amount of directly emitted luminous flux, and to reduce aberrations.
It is a further object of the invention to devise an assembly in which a light source is associated with an optical system of which at least a part causes the light rays to converge; in which assembly emission losses resulting from total internal reflection at the boundary of said system can be substantially reduced.
According to the invention there is provided an optical system comprising a dome-shaped
lens for modifying the multi-directional light distribution of a light source located substantially in the central area of the notional base plane (as herein defined) of the lens to provide a light distribution exhibiting a relatively high intensity in the direction of the axis of the lens compared with the intensity provided by said source in the absence of said lens, wherein the outer refractive boundary surface of said lens is formed so that, viewed axially from its apex towards said base plane, it comprises a central spherical dome whose centre of curvature is situated between said apex and the said central area of said base plane, which merges into at least one distinct spherically curved annular zone whose centre of spherical curvature is situated between that of said spherical dome and said central area of said base plane, the arrangement being such that in directions increasingly angularly displaced from the axis of the lens, the intensity of the light emitted via said spherically curved annular zone or zones decreases smoothly in a predetermined manner without abruptly falling to a low value except at the outer edge of the or the outer said spherically curved annular zone.
Preferably, an optical system in accordance with the invention – except for said spherical dome – is bounded by a plurality of consecutive spherically curved annular zones whose
centres of spherical curvature are each situated, between that of the preceding zone, reck oned from the apex of said optical system towards said notional base plane.
Thus, in a device embodying the invention, the optical system is constituted by consecutive sections of spherically curved annular zones whose respective radii of spherical curvature increase from its apex towards said base plane.
Such a device has the advantage of substantially reducing loss of light owing to total internal reflection at the boundary wall of the optical system, in comparison with the substantial loss found with prior art converging optical systems of a similar type, consituted as previously described by a hemispherical block which is extended by means of a cylindrical coaxial portion.
Let us consider – for an optical system in accordance with the prior art – a ray which leaves the source at an angle8 measured relative to the axis of revolution of the optical system, and which is incident from within the refractive medium on the surface of the hemisphere at an angle which is equal to the critical angle. This ray, together with all the rays whose angle of emergence from the source is less than or equal to H, will leave the optical system. A ray whose angle of emergence from the source is greater than 8 will be totally internally reflected.
An optical system in accordance with the invention is made such that at the point of incidence of the last-mentioned ray the shape of the refracting boundary of said optical system-is modified – so that its centre of spherical curvature is located nearer to the source than the centre of curvature the spherical front portion. i.e. the radius of curvature of the further portion is made greater than the initial radius of curvature – in such a way that the angle of incidence again becomes less than the critical angle. The ray can then leave the system. All the rays whose angle of emergence lies between 0 and a + will also leave, where H + a is the angle of emergence from the source of those rays, for the further spherically curved annular zone under consideration, which are incident on said zone at the critical angle. For angles greater than 8 + , said further spherically curved annular zone should be replaced by yet another spherically curved annular zone with a greater radius of curvature, whose centre of curvature is located still nearer to the source.
Thus, step by step, by the addition of consecutive spherically curved annular zones, the entire bundle of rays emitted by the source can be covered, with a minimum risk of reflection losses, by converging said rays to a greater or lesser extent.
A light-emitting crystal, observed through a transparent optical system in accordance with the invention, can be made always visible over its entire area, regardless of the angle of observation. This is the result of the addition of progressively less spherically curved annular zones to the cylindrical apex portion of a hemispherical-cylindrical system derived from the prior art. In order to improve the convergence of the marginal rays this substitution may even be completed so that no cylindrical portion remains at all. However, in certain cases this results in the cross-section of the optical system at the location of its base plane, being less than that at a location situated between this base plane and the apex of said optical system. If the optical system is to be made by moulding only, without any subsequent machining, it is evident that removal from the mould may present problems in that case and may at least necessitate the use of a mould consisting of several parts.
In practice, in order to avoid any problems during removal from the mould, the shape of the optical system is preferably designed so that starting from its apex, it comprises a spherical dome surrounded by a series of spherically curved annular zones, and finally a portion of relatively short axial length with a cylindrical geometry ie. substantially shorter in proportion than in prior-art optical systems with the same linear magnification.
The progressive increase in the radius of spherical curvature of the respective zones of an optical system in accordance with the invention, necessarily results in a reduction in the linear magnification and a reduced convergence, which become more marked as the angle of emergence of the rays from the source increases. This arrangement however, meets the requirement that the greater part of the light emitted by the crystal can leave the device and also that aberrations can be reduced, which is necessary in particular for providing an assembly that can be used satisfactorily for remote control.
The presence of a spherical dome at the apex of the optical system ensures that in the axial region a range is obtained equal to that of the devices of the hemispherical-cylindrical type of the prior art, with the same radius of curvature and the same distance between the source and the centre of curvature, for the hemisphere in the case of the prior art and for the spherical dome in the device in accordance with the invention. However, in the case of prior-art devices, owing to the presence of dead angles, the emission is highly directional, which renders control rather critical regardless of the distance from the apparatus to be controlled.
By contrast, an optical system in accordance with the invention allows a progressively decreasing amount of emission to occur for directions away from the axis enabling a controlled operational range to be provided for all directions as desired, the luminous intensity emitted by the optical system decreasing according as the angular distance from the axis increases. This is advantageous because if control at the maximum range (axially) remains relatively directional, control at medium and short distances becomes less critical, and the amount of luminous intensity directed at an angle to the axis may then suffice to ensure the desired control.
In respect of aberrations – mainly owing to the fact that the source is not a point source calculations and experience reveal both for a “hemispherical-cylindrical” system comprising the prior art and for an optical system in accordance with the invention, that these occur, for a given direction of emission from the source, beyond a certain value of the radius of curvature of the optical system in this direction, which value is reached sooner according as the emission angle is more divergent. This can form an advantage in favour of a device in accordance with the invention since, by varying the radius of curvature and location of the centre of curvature of parts of the optical system, aberrations can thereby’be reduced, except in the axial region with a large spacing of the centre of curvature from the source, said high value of this spacing resulting from the necessity to obtain a satisfactory range for remote control.
It is to be noted that the use of an optical system whose shape is in accordance with the characteristic features of the invention, does not exclude the simultaneous use of a reflecting surface disposed behind and at the side of the semiconductor crystal forming the associated source; if desired, such a reflecting surface can enable a better focussing of the marginal rays to be obtained, which rays leave the source at an angle of emergence of approximately 90″ and which are mainly directed towards the cylindrical portion of the optical system.
Embodiments of the invention will now be described by way of example, with reference to the accompanying drawings, of which:
Fig. 1 schematically shows the structure of an optical system in accordance with the invention, in longitudinal axial section,
Fig. 2 is a diagram of an optical system in accordance with the invention in which the parameters are indicated which enable the different radii of curvature of this optical system to be calculated,
Fig. 3, which shows the paths of some light rays issuing from a marginal point of the source, demonstrates the significance of an optical system in accordance with the invention in respect of the reduction of reflection losses,
Fig. 4 is a composite graph which represents the increase in angular magnification concentration of light due spherical refraction as a function of the angle of emission from the source in an optical system in accordance with the invention, and which also illustrates the shape of curves relating to the onset of internal reflection and to aberration, and
Fig. 5 is a longitudinal axial section which shows schematically an example of an assembly of a light-emitting diode and an optical system in accordance with the invention, which assembly can be used in an optical transmitting device for the remote control of a television set.
The assembly shown in Fig. 1 essentially consists of a convex optical system 1, in the form of a dome-shaped lens which is optically coupled to a light source 2. The optical system 1 is rotationally symmetrical about the axis I-I. The source 2 is located substantially in the median area of the base plane 3 of the optical system 1.
In accordance with the invention, said optical system 1, viewed from its apex 4 towards its base plane 3, is first bounded by a spherical dome 10 whose centre of curvature C10 is situated on the axis I-I between said apex and the source 2, which spherical dome merges with an adjoining spherically curved annular zone whose centre of spherical curvature Cn is situated between the centre C10 and the source 2. In the example of Fig. 1, three spherically curved annular zones 11, 12 and 13 are shown, which in that order follow the spherical dome 10, whose centres of spherical curvature, in accordance with the invention, are situated at C11 between the centre C10 and the source 2 for the zone 11, at C12 between the centre C11 of the preceding zone 11 and the source 2 for the zone 12, and at C13 between the centre C12 and the source 2 for the zone 13.
In order to clarify the structure of an optical system in accordance with the invention, spaces have been left in Fig. 1, which separate the spherical dome 10 and the spherically curved annular zone 11 and the spherically curved annular zones 11, 12 and 13 from one another. It will be evident that the shape of the optical system is intended to be continuous, i.e. so that each part continues from the boundary of the adjacent part(s).
In a slightly different embodiment of an opitcal system in accordance with the invention which facilitates the manufacture by moulding, the part of the optical system disposed between the base plane 3 and the plane defined by the line II-II parallel to said base plane 3 and passing through the centre of curvature C13 has been replaced by a part with a cylindrical geometry bounded by the dashed line 5, substantially parallel to the axis I-I; this is in order to ensure that the surface area of the base plane 3 is at least equal to that of the section of the optical system at II-II and that a single-piece mould can be used.
As the centres of curvature C11, C12, C13 are each disposed nearer the source 2, and as each part of the profile merges with the preceding part without abrupt transitions, i.e. without steps such as are to be found, for example, in a Fresnel type lens, it can be seen that the consecutive radii of curvature R10, R11, R12, R13 increase in length, which results in a reduction of the linear magnification and of the convergence after the transition from the spherical dome 10 to the spherically curved annular zone 11 and subsequently after each transition from one spherically curved annular zone to the next. There is also a corresponding decrease in the amount of angular concentration of light from one zone to the next, which value may be defined, for one direction of emission reckoned from the source 2, as the ratio between the luminous intensities in said direction when the source is provided with a said optical system and when said system is removed.
For an optical system with a spherical shape, the linear magnification and the angular concentration of light from a source which is caused by the system, vary in the same sense, and can be represented by the ratios of the distance x separating the source from the centre of curvature and the radius of curvature R of the spherical refracting surface of the optical system.
Thus, with an optical system in accordance with the invention as described with reference to Fig. 1 a maximum amount of angular concentration is obtained on the axis I-I and in the angular cone which spans the spherical dome, and this degree of concentration will decrease in a lateral direction, going from one zone to the next zone of the optical system, and will become low, and finally almost zero, i.e. no concentration with respect to the source itself, for highly diverging angles of emission relative to said axis I-I.
The optical system of Fig. 1 only comprises three spherically curved annular zones, but it will be evident that it may comprise more zones provided that the zones are not thereby made so small as to loose their individual identity. Each of the radii R11, Rl2, R13, … Rn of the consecutive spherically curved annular zones, is calculated with respect to the initially selected radius R10 of the spherical dome, after choosing suitable values for the ratios x11 X12 x13 xn
R11 R12 R13 Rn
which correspond to the amounts of angular concentration of light chosen for the emission angles Oii, 812, 013, … On from the source.
The choice of the different ratios
x11/R11 x12/R12 x13/R13 ..xn/Rn, depends on the modification of the emission distribution of the actual source to be achieved by the addition of the optical system and, as will be described hereinafter, to reduce or avoid the effects of total internal reflection.
The following calculation, in which the parameters correspond to those shown in Fig. 2, reveals how the various radii R11, R12, R13, … Rn of an optical system in accordance with the invention are calculated.
Given a part of the optical system which is limited to a spherical dome 10 and to two spherically curved annular zones 11 and 12, M and N denote the transitions between these three parts of the profile, which parts have centres of curvature C10, C11 and C12 respectively.
S-C10; S-C11; and S-C12; represent the respective distances x10, x11 and x12 from the source to each of the centres of curvature. C10-M; (C11-M) = (C11 – N); C12 – N; respectively correspond to radii of curvature R l o, R11, R 12, of the parts 10, 11 and 12 of the optical system.
The point H is the perpendicular projection of the point M onto the axis of revolution of the optical system; the point P is the perpendicular projection of the point C11 on the line SN.
The radius R10, the distance X10 and the angle 10, which define the geometry of the spherical dome 10, are initially specifically chosen to give the required dimensions which the optical system should have and the required magnification in the axial region. From the three given parameters R10, x10, and PlO, the inner radius MH of the annular zone 11 is calculated.
The position of the centre of spherical curvature C11 of said spherically curved annular zone 11, is determined by an iterative calculation which initially assumes a value x11. The calculation given hereinafter provides a corresponding value R11 which results in a corresponding value of the ratio x11/R11, which by reselection of X11 is caused to approach a value chosen from a function relating the angular concentration x/R to be provided by the spherically curved annular zone 11 for a given source angle #11 (e.g. as given by the curve A in Figure 4).
Let us consider the right-angled triangle C11MH.
C11M = R11 = J MH2 + C11H2 (1)
Furthermore:
MH = C10M.sin 10 = R10 .sin 10
and, selecting a value for x11,
C11H = C10H + C11C10 = R10 .cos 10 + (x10-x11).
Inserting the values found above for MH and C11H in expression (1), yields:
R11 = # (R10 .sin 10)2 + (R10.cos 10)2 + (x10-x11)2+ @ 2R10(x10-x11)cos 10
and, as sin2 10 + cos2 10 = 1,
R11 = R102+(x10-x11)2+2R10(x10-x11)cos 10
A similar iterative calculation enables the value of the radius of spherical curvature R12 of the zone 12 to be determined as a function of R11, xll, x12 (whose value, in the same @ way as that of xl0 and xl, is the result of a choice) and P11. Only the value of the angle P11 is still
unknown. The simple calculation given below enables this value of 11 to be obtained.
It follows that:
11 = i11 + #11 (triangle SC11N).
On the one hand:
C11P C11P
sin i11 = (2)
C11N R11 On the other hand:
C11P C11P
sin #11 = (3)
SC11 x11
Equating the values of C11P found from (2) and (3), yields:
C11P = R11.sin i11 = x.11.sin #11 so that:
sin i11 = x11/R11. sin #11. x11 and R11 are known #11 is chosen. It can for example be decided that the angle at the location of the source S between two consecutive spherically by curved annular zones should be 2″, or 5 , or any value chosen as a function of the precision required for the shape of the final emission diagram provided that the zones retain their individual identity and, in the limiting situation, the onset of total internal reflection is avoided.
Thus, ill is known, which is derived from the value of sin ill, and consequently P11 is known.
The radii of spherical curvature of the consecutive spherically curved annular zones can thus be determined iteratively, the general expression for the radius of spherical curvature being:

in which expression:
– Rn is the radius of spherical curvature of the zone (zone n) preceding the zone (zone n + 1) whose radius of spherical curvature Rn+l is to be determined,
– xn and Xn+l represent the respective distances from the source to the centres of spherical curvature of the zone n and n +1, and, -Pn is the angle formed between the axis of revolution of the lens and a straight line passing through the centre of spherical curvature of the zone n and constituting the boundary between the zones n and n +1.
Once the values of the radii of spherical curvature of the different parts of the optical system have been determined, all the distances can be calculated between the surfaces of said optical system and the median area of the source, which are required for the subsequent production process.
In the schematic representation of an optical system in accordance with the invention in
Fig. 3, which system is made of a materi
In general, an optical system in accordance with the invention may alternatively include spherically curved annular zones whose number and dimensions correspond to a regular sub-division of a cone-shaped distribution whose apex is located at the source, or by spherically curved annular zones of different angular extent, provided that the zones retain their individual identity.
The graph in Fig. 4 is by way of example and in general illustrates for an embodiment of the invention the shapes of various functions. Curve A indicates a design trend function relating the desired ratio x at a corresponding angle 0 for an embodiment of the invention; curve B indicates the angle (horizontal axis) of onset of total internal reflection for corresponding values w shown vertically; and curve C indicates the amount of aberration on an arbitrary vertical scale, caused at different values of the angle 8 (horizontal scale) for an optical system in accordance with the invention having an 2 trend function as shown by Curve A.
On the horizontal axis the values of the light emission cone (half-angle B) in degrees are plotted, starting from a source which is supposed to be small relative to the optical system and which is substantially completely included in the base plane of said optical system.
On the vertical axis the values of different ratios of a, namely; X x12 X13 x k
R11, R12, R13, n n+l defined hereinbefore, are indicated to which the values of the angular concentration of emitted light are related: the ratio 1 corresponds to a distance between the centre of curvature of the part of the optical system under consideration and the source equal to the value of the radius of curvature R of the corresponding spherical surface in this case the spherical dome; the ratios smaller than and the ratios greater than 1 respectively correspond to distances between the various centres of curvature and the source which are smaller and greater than the corresponding value of the radius of curvature R. Ratios greater than 1 merely illustrate the trend of curve B in this case.
The shape of the reflection curve B is perfectly straightforward: as the source is moved farther from the centre of curvature (i.e. as the ratios is increases), the extent of the angular cone of light rays which are not totally internally, reflected becomes smaller. Indeed, for a light ray other than an axial ray, the angle of incidence on the refracting boundary of the optical system tends to increase as the source is located further from the apex of said optical system.
The shape of the aberration curve C is more complex: the aberration factor increases rapidly from 0 to 15-20″, and subsequently decreases and falls off regularly down to 90″.
The high aberration factor in the region near the axis, which is inevitable, is both due to the fact that the source is not a point source and that both the magnification and the degree of angular concentration is high in this region. Reducing the surface of the source generally also means a reduction of the amount of light emitted. Reducing the magnification causes a reduction of the light range. It is evident that when a low power source is available, such as a light-emitting diode, and remote control is to be effected with such a source over a range of for example up to some twenty metres, it is necessary that in the axial region the radios should be sufficiently high even if this entails accepting a rather high aberration factor in this region.
The curves B and C, in accordance with a general scheme, represent the reflections and aberrations. It will be apparent that depending on the specific properties of optical systems in accordance with the invention, the calculated values may differ substantially from those indicated by way of non-limitative example on the graph in Fig. 4.
If reflections are to be avoided, and whenever possible also aberrations are to be reduced (ie. on the graph, above an emission angle of 10 to 150), the curve A (from which curve the desired values of the ratios are to be read wherefrom the apopropriate spherical radius of the optical system may be calculated for any angle of emission 8 in accordance with the method set out hereinbefore) should be situated completely to the left of the curve B. The path of the curve A is a function of the difference between the light distribution of the source alone and the desired distribution of the source optical-system assembly.
The design of an optical system in accordance with the invention, which is for example intended for remote control of a television set, by means of the luminous flux supplied by a light-emitting diode. should largely be effected in accordance with the following method:
-Determining the curve of the consecutive ratios x of the different parts of the optical system on the basis of the difference between the light distribution of the source alone and the desired distribution. for example in steps of 5 degrees, from 0 to 900.
-Calculating the different radii of curvature corresponding to the various ratios RX in accordance with the previously indicated method of calculation and thus determining an initial profile of the optical system.
-Correcting this profile exactly so as to avoid reflections and aberrations, (e.g. by considerations of the kind illustrated by Figure 3).
-modifying the profile thus obtained in accordance with the requirements of the mechanical design, in particular in respect of the possibility of removal from the mould, and applying the necessary minor corrections.
In this way the Applicant has realized a light emitting assembly suitable for use in the remote control of a television set by means of gallium-arsenide light-emitting diodes which emit infra-red light, which assembly enables the set to be controlled from any point within an area of 20 m length and 10 m width, the television set being placed along one of the short sides of this area. The geometry of this assembly is given hereinafter so as to complete the following brief description with reference to the schematic diagram shown in Fig. 5 in which the individual discrete spherically curved annular zones are not shown.
The optical system can be realized in accordance with a first embodiment, as a moulded capsule 50 whose part having a profile in accordance with the invention as generally described with reference to Figures 1, 2 and 3, is the upper portion 51 which is disposed above the horizontal plane corresponding to the axis XX. The optical system is a solid of revolution about the axis YY.
The semiconductor crystal of the light-emitting diode 52 is disposed at the intersection of the axes XX and YY; its active surface, which faces the top 53 of the optical system, is coplanar with the horizontal plane defined by the axis XX. In known manner and in accordance with a method which has been described previously by the Applicant in the
French Patent Specification no. 2,165,151, this crystal is electrically connected to a conductor 54A on which it rests, and to the lateral conductor 54B by the connecting wire 55. The part 51 of the capsule 50 below the axis XX takes the form of a cylindrical annular skirt 56 in which the conductors 54A and 54B are disposed.
The volume 57 inside the capsule 50 is filled, in known manner, after the crystal has been brought in position, with a solidifiable transpartent substance with suitable optical properties.
Inside the upper part 51 of the capsule 50, above and around the axial area where the crystal 52 is located, a small chamber 58 is formed. This chamber serves to facilitate the exact alignment of the crystal 52 and also to accommodate the connecting wire 55.
The chamber 58 has a hemispherical shape and is centred relative to the crystal 52. Such a shape has been chosen because it allows all the light rays issuing from the crystal 52 in the capsule 50 to pass through any point of its surface, regardless of the index of refraction of the intermediate medium filling said chamber 58.
The capsule 50 is made by moulding, for example of a polycarbonate substance. The volume 57 and the adjoining chamber 58 are filled with a thermosetting resin whose index of refraction is chosen to be substantially equal to that of the substance of which the capsule 50 is made. Allowance is to be made for the presence in the optical system of two transparent media with indices of refraction which differ slightly when the profile of said optical system is determined.
In accordance with a second embodiment of a source/optical-system assembly having an outer profile in accordance with the invention as generally described with reference to
Figures 1, 2 and 3, the total volume corresponding to the capsule 50 and to the volumes 57 and 58, can be formed in a single moulding operation in a mould of suitable shape, which is sufficiently hollow to enable the crystal 52 and the ends of the conductors 54A and 54B to be introduced into it. This embodiment is more critical in respect of the accuracy of positioning of the crystal 52. However, it has the advantage that only one transparent medium Is employed, which facilitates the calculation of the profile of the optical system.
By way of example, the following table gives the general dimensional characteristics of the optical system in accordance with the invention, which is used, as described hereinbefore, for a light-emitter in the remote control of a television receiver in an area of 20 m x 10 m. The optical system has been made, in accordance with the second embodiment described above of a polycarbonate with an index of refraction n = 1.53. The crystal 52 occupies an average width of 0.450 mm (the thickness of this crystal is 0.2 mm) on a base plane in accordance with
XX having a diameter of 4.9 mm. The maximum height of the optical system (distance between the axis XX and the apex 53) is 3.98 mm.
The table gives the polar coordinates of the general form of the optical system, defined in steps of 5 , by the value p in mm, of the distance between the centre of the crystal and the periphery of the optical system, as a function of the angle of emission 0 which varies from 0 to 90″.
P H mm degrees
3.98 0
3.98 2
3.965 5
3.92 10
3.85 15 3.76 20
3.64 25
3.52 30
3.39 35
3.26 40
3.13 45
3.00 50
2.88 55
2.77 60
2.68 65
2.60 70
2.53 75
2.48 80
2.46 85
2.45 90
With such an optical system the emission diagram light distribution is such that a television receiver can be controlled at 22 m through a very small angle, to 21.3 m through an angle of 10 , to 18m through an angle of 30 , to 15 m through 50 , to 10 m through 105 , to 5 m through 145″. It can be seen that down from a distance of 15 m control is only slightly directional and therefore very convenient.
In this respect it is to be noted that the optical system in accordance with the invention in the example in which it is used for controlling a television set as described, has the advantage that no reflecting surface is necessary, which simplifies making the assembly. However, it is evident that the use of a reflecting surface is entirely conceivable, both for use in the case of remote control or for other uses, without giving rise to any other technical problems than normally associated therewith. In the example mentioned with reference to Fig. 5, it suffices for example to interpose a cap of suitable height and shape between the crystal 52 and the conductor 54A, which functions as a reflecting surface; it is alternatively possible to machine the upper part of the conductor 54A in such a way that the desired geometry is obtained, provided that the cross-section of said conductor is sufficient relative to that of the crystal 52.
Furthermore, the use of optical systems in accordance with the invention is not limited to remote control only. Generally speaking, they may be used in any control or signalling device and therefore be associated with light-emitting diodes emitting different visible or non-visible radiation. For the envisaged application the optical systems may be either transparent or made of materials which promote the diffusion of light.

Claims (15)

WHAT WE CLAIM IS:

1. An optical system comprising a dome-shaped lens for modifying the multi-directional light distribution of a light source located substantially in the central area of the notional base plane (as hereinbefore defined) of the lens to provide a light distribution exhibiting a relatively high intensity in the direction of the axis of the lens compared with the intensity provided by said source in the absence of said lens, wherein the outer refractive boundary surface of said lens is formed so that, viewed axially from its apex towards said base plane, it comprises a central spherical dome whose centre of curvature is situated between said apex and the said central area of said base plane, which merges into at least one distinct spherically curved annular zone whose centre of spherical curvature is situated between that of said spherical dome and said central area of said base plane, the arrangement being such that in directions increasingly angularly displaced from the axis of the lens, the intensity of the light emitted via said spherically curved annular zone or zones decreases smoothly in a predetermined manner without abruptly falling to a low value except at the outer edge of the or the outer said spherically curved annular zone.

2. An optical system as claimed in Claim 1, including a plurality of consecutive said distinct spherically curved annular zones whose centres of spherical curvature are each situated between that of the preceding zone and the base plane, reckoned from the apex of said optical system towards said notional base plane.

3. An optical system as claimed in Claim 2, wherein the angular extents of said annular zones – defined in a plane of longitudinal section of said lens, which plane passes through the apex of said system and the central point of said notional base plane, by the angular separation of those lines joining the limiting points of respective said zones to said median point – are the same for all said zones.

4. An optical system as claimed in Claim 2, wherein the angular extents of said annular zones, measured as defined in Claim 3, are different for at least two of said annular zones.

5. An optical system as claimed in any one of the preceding Claims, formed so that it is bounded in this order, from its apex towards said notional base plane, by a spherical dome, at least one spherically curved annular zone and a section with the geometry of a cylindrical surface.

6. An optical system as claimed in any one of the preceding Claims, wherein the radii of spherical curvature and the angular extents of said annular zones – measured as defined in
Claim 3 – are such, that the light rays emanating from the said central area of said base plane, which are incident on the surfaces of said dome and said annular zones, are incident at angles which at the most are equal to the critical angle, which critical angle is determined by the ratio of the values of the indices of refraction of the medium of which the lens is formed and the medium outside the boundary surface of said lens.

7. An optical system as claimed in any one of the preceding Claims, wherein the radii of spherical curvature of the consecutive annular zones, are given by the expression:

in which expression:
– Rn is the radius of spherical curvature of the zone (zone n) preceding that zone (n + 1 whose radius of spherical curvature Rn+l is to be determined,
– xn and Xn+l represent the respective distances to the said central area from the centres of spherical curvature of the zones n and n +1, and
– ssn is the angle formed between the axis of revolution of the lens and a straight line passing through the centre of spherical curvature of the zone n and constituting the boundary between the zones n and n + 1.

8. An optical system comprising a dome-shaped lens, substantially as herein described with reference to Figures 1, 2 and 3 of the accompanying drawings.

9. The combination of an optical system as claimed in any one of the preceding Claims and a light source located substantially in said central area of said notional base plane of the lens and arranged to direct light into said lens.

10. The combination claimed in Claim 9, further including a reflecting surface which extends behind said notional base plane and the light source relative to the apex of said lens, and laterally relative to said central area thereof and to said light source.

11. The combination as claimed in Claim 9 or 10, wherein said optical system takes the form of a profiled cap of a first transparent substance, which bounds an internal hemispherical volume in whose central region said light source is arranged and which contains a second transparent substance.

12. The combination as claimed in Claim 9 or 10, wherein said optical system is entirely made of the same transparent material.

13. The combination as claimed in any one of Claims 9 to 12, wherein said optical system includes a material with diffusing properties.

14. The combination of an optical system comprising a dome-shaped lens and a light source, substantially as herein described with reference to Figures 1, 2, 3 and 5 of the accompanying drawings.

15. An optical remote control system for controlling a television set, including the combination claimed in any one of Claims 9 to 14, in which said light source comprises a light-emitting diode.

GB21576/77A
1977-05-23
1977-05-23
Optical system

Expired

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(en)

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Optical system

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Cited By (5)

* Cited by examiner, † Cited by third party

Publication number
Priority date
Publication date
Assignee
Title

WO1985003781A1
(en)

1984-02-16
1985-08-29
Hughes Aircraft Company
Hyperhemispherical radiation system

FR2699292A1
(en)

1992-12-15
1994-06-17
France Telecom

Method for the preparation by multiple lensing of an optical fiber for optimum coupling with a phototransducer and optical system obtained.

FR2760098A1
(en)

1997-02-27
1998-08-28
Marc Leveille
Luminosity improver for electroluminescent light sources

WO2002007228A1
(en)

2000-07-19
2002-01-24
Qinetiq Limited
Light emitting diode with lens

WO2006136965A2
(en)

2005-06-23
2006-12-28
Koninklijke Philips Electronics N.V.
A light-emitting device and method for its design

1977

1977-05-23
GB
GB21576/77A
patent/GB1586188A/en
not_active
Expired

Cited By (8)

* Cited by examiner, † Cited by third party

Publication number
Priority date
Publication date
Assignee
Title

WO1985003781A1
(en)

1984-02-16
1985-08-29
Hughes Aircraft Company
Hyperhemispherical radiation system

FR2699292A1
(en)

1992-12-15
1994-06-17
France Telecom

Method for the preparation by multiple lensing of an optical fiber for optimum coupling with a phototransducer and optical system obtained.

EP0603041A1
(en)

1992-12-15
1994-06-22
France Telecom
Preparation of optical fibre end face with multiple lens for optimum coupling

US5402510A
(en)

1992-12-15
1995-03-28
France Telecom
Method of preparing an optical fiber with multiple lenses to optimize coupling with a phototransducer, and an optical system obtained thereby

FR2760098A1
(en)

1997-02-27
1998-08-28
Marc Leveille
Luminosity improver for electroluminescent light sources

WO2002007228A1
(en)

2000-07-19
2002-01-24
Qinetiq Limited
Light emitting diode with lens

WO2006136965A2
(en)

2005-06-23
2006-12-28
Koninklijke Philips Electronics N.V.
A light-emitting device and method for its design

WO2006136965A3
(en)

2005-06-23
2007-10-25
Koninkl Philips Electronics Nv
A light-emitting device and method for its design

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