KR0155771B1 - Parallel ray illuminator - Google Patents

Abstract

A parallel light illumination device mainly used for a projector using liquid crystal elements such as PDLC is disclosed.

The parallel light illuminating device includes a light source 32, an elliptical reflector 30 which converts an optical path so that the light emitted from the light source 32 is directed in one direction about the optical axis 1, and the elliptical reflector ( A collimating lens 36 is provided in order to form the same optical axis 1 as that of 30) and to be reflected by the ellipsoidal reflector 30 to convert the light through the focal point F2 into parallel light. Due to the geometric characteristics of the light source 32, light having a predetermined height around the optical center 1 reflected by the ellipsoidal reflector 32 has a lower luminance portion 42 than the surrounding area, which is a dark area. In order to remove the non-uniform area which exists by this brightness | luminance part 42, the conical beam compressor 5 of the hollow cone shape was provided in the exit surface of the collimating lens 36 quickly. The beam compressor 50 reduces the width of the entire light in the direction of the optical axis 1 while maintaining the parallel of the light incident in parallel upon exit. Therefore, the dark area 42 is removed by the width between the incident surface 51 and the exit surface 52 of the beam compressor 50, the inclination with respect to the optical axis 1, and the refractive index. Parallel light having a distribution can be derived.

Description

Parallel light illuminator

(A) and (b) of FIG. 1 are schematic diagrams showing a conventional parallel light illuminator.

(A) of FIG. 2 is a schematic diagram which shows the parallel light illuminating device which concerns on this invention, (b) is sectional drawing which shows the beam compressor employ | adopted in this invention.

Figure 3 is a schematic diagram showing the flow of light emitted through the parallel light illumination apparatus according to the present invention.

* Explanation of symbols for main parts of the drawings

30: elliptical reflector 32: light source

34: aperture stop 36: collimating lens

40: outgoing light of uniform brightness 42: outgoing light of low brightness

50: beam compressor 60: stopper

70: uniformly emitted light

The present invention relates to a parallel light illumination device for obtaining a uniform and parallel output light, and in particular, to improve the problem of lowering the brightness of the center of the reflector according to the geometric position of the light source to be used in a display such as a liquid crystal projector A parallel light illuminator for emitting parallel light.

In general, the parallel light illuminator is used to provide only parallel light so as to transmit an image provided by the electrical characteristics of the liquid crystal device employed in the liquid crystal projector, etc., and because the screen size of the liquid crystal projector is small, the uniformity of the incident parallel light is large. It didn't matter.

1 shows a conventional parallel light illuminator. Referring to this drawing, the structure, function, and problems of a conventional parallel light illuminator will be described.

Light source 12 using an arc discharge, xenon or halogen lamp, etc. to generate and emit light by the applied electricity, and an elliptical reflector that changes the light path so that the emitted light emitted from the light source 12 faces a predetermined direction ( 10) and a collimating center of which is located at the same optical axis 1 as the optical axis 1 of the ellipsoidal reflector 10 and converts light changed in one direction by the ellipsoidal reflector 10 to parallel light. A lens 16 is provided to form the parallel light illuminator.

The ellipsoidal reflector 10 has a first focal point F1 and a second focal point F2, and the light source 12 is emitted from the light source 12 with its center approximately positioned at the first focal point F1, and the elliptical reflector 10 The light whose optical path is modified by) is collected at the second focus F2. The focus of the collimating lens 16 is located at the second focal point F2 in order to convert this light into parallel light.

The light source 12 has a predetermined size that cannot be precisely positioned at the first focal point F1, and light is reflected and output by the ellipsoid reflector 10 because optical aberration exists in the ellipsoid reflector 10. It is impossible to pass the second focal point F2 correctly. The optical axis 1 is centered around the second focal point F2 in order to prevent the light reflected by the other path from passing through the second focal point F2 and entering the collimating lens 16 and obstructing the output of parallel light. An aperture stop 14 having a predetermined hole was provided. Relatively parallel parallel light can be derived by removing the stray light passing through the second focal point F2 through the aperture stop 14.

In the projector using a conventional liquid crystal device, the size of the screen for providing an image is not very large as compared with the case of using a cathode ray tube, so that the uniformity of the light emitted from the lighting device is not a problem. There was an interest in preventing.

The conventional parallel light illuminator is shown in the portion 20 having a relatively uniform light distribution around a predetermined angle around the output optical axis 1 according to the geometry of the light source and the coupling position to the elliptical reflector as shown. In contrast, dark portions 22 having lower luminance are formed. Referring to (b) of FIG. 1, when the amount of light emitted from the angle of α with respect to the light source 12 is analyzed, the angle α is close to zero when the angle α is parallel to the optical axis 1. When it is increased and perpendicular to the optical axis 1, the amount of emitted light is maximized. Therefore, a dark portion 22 having a low luminance as mentioned above inevitably exists.

Such non-uniform amount of light distribution has emerged as a problem in providing high definition and high quality images when the size of the screen used in the projector using the liquid crystal element is increased.

Therefore, the present invention has been made in order to overcome the problems described above, it is an object of the parallel light emitted from the parallel light illumination device to have a uniform light amount distribution.

The present invention to achieve the above object,

A light source, an elliptical reflector positioned to surround the rear surface of the light source so that the light emitted from the light source faces one direction, and a collimating lens positioned on the path of the light reflected by the ellipsoidal reflector to convert into parallel light In the parallel light lighting apparatus provided with,

A beam compressor is provided on the exit surface of the collimating lens to emit uniform parallel light by compensating light emitted with low luminance due to the geometry and position of the light source among the light reflected by the ellipsoidal reflector. .

Hereinafter, with reference to the accompanying drawings will be described an embodiment of the present invention;

(A) of FIG. 2 is a schematic diagram showing a parallel light illuminator according to the present invention, and (b) is a schematic diagram showing a beam compressor employed in the parallel light illuminator of the present invention and an optical path deflected and deformed by the beam compressor. to be.

According to the present invention, the light source 32 generates and emits light, the ellipsoidal mirror 30 which guides the light emitted from the light source 32 in one direction, and the ellipsoidal mirror 30 is reflected by the optical axis 1. A collimating lens 36 for converting light emitted to the center into parallel light is provided on the same optical axis 1 of the optical axis 1 of the ellipsoidal reflector 30.

The ellipsoidal reflector 30 has a first focal point F1 and a second focal point F2, and the center of the light source 32 is positioned at the first focal point F1, and the second focal point F2 is the collimating lens 36. Matches the work focus. Therefore, in theory, all the light emitted from the light source 32 located at the first focal point F1 converges to the second focal point F2 and becomes parallel light through the collimating lens 36. However, since the aberration of the elliptical reflector 30, the collimating lens 36, and the light source 32 are not precisely positioned at the first focal point F1, light that does not pass through the second focal point F2 is generated. The light is provided with an aperture stop 34 having a hole having a predetermined diameter around the second focal point F2 to block the incident to the collimating lens 36. According to the geometry of the light source 32 and the coupling position of the ellipsoidal reflector 30, as described with reference to FIG. There is an area 42. Non-uniform light is included in the parallel light emitted by the dark region 42. As a means for compensating for the non-uniform light, a beam compressor 50 is provided on the exit surface of the collimating lens.

The beam compressor 50 allows the parallel light incident through the collimating lens 36 to be emitted in parallel without converging or diverging, and to reduce the width of the light beam passing through the collimating lens 36 to be emitted. It has an empty cone shape, and its vertex is directed toward the collimating lens 36, and the optical axis 1 coincides with the optical axis 1 of the collimating lens 36. Of course, the conical outer circumferential surface 51 and the inner circumferential surface 52 are parallel and inclined at an acute angle θ with respect to the optical axis 1.

Referring to (b) of FIG. 2, the relationship between the light entering and exiting the beam compressor 50 will be described in detail.

The beam compressor 50 has its incidence plane and the outgoing plane inclined by the angle θ with respect to the optical axis 1, and the shortest distance between the incidence plane 51 and the exit plane 52 is uniform at t. In addition, the refractive index of the medium is n, and light incident in parallel with the optical axis 1 at a height h through the collimating lens 36 is angled at 90 ° to the normal direction of the incident surface 51. θ is achieved. In addition, since the refractive index in air is 1, when the refractive angle is θ 'with respect to the normal plane direction with respect to the incident surface 51,

By Snell's law Θ 'can be represented by other known constants θ and n.

Accordingly, the height h 'of the light passing through the beam compressor 50 is calculated using Snell's law and the trigonometric function when the incident light is h, as follows.

Therefore, assuming that the diameter of the light having low luminance caused by the geometrical characteristics of the light source 32 and incident by the collimating lens 36 into the parallel light by being deformed into parallel light is ø, in the optical axis 1 The height of light having this low luminance is? / 2. H 'must be zero when the height of the low luminance light is ø / 2 to remove light from the dark portion 42 passing through this height area and refracting out light having a uniform distribution around it into the area. do.

In other words, If the relation is satisfied, the dark region passing through the center of the beam compressor 50 disappears.

Since ø is a value according to the size and structure of the light source, the dark area may be designed to disappear by adjusting the width t or the inclination angle θ of the incident surface 51 and the exit surface 52 of the beam compressor 50. Can be.

3 is a schematic view showing another embodiment of a parallel light illuminator according to the present invention. Another embodiment will be described in detail with reference to this drawing.

A beam compressor 50 as described with reference to FIG. 2 is provided adjacent to the exit surface of the collimating lens 38. In addition, a stopper is formed on the incident surface of the collimating lens 37 to exclude a low luminance portion, which is a dark region incident by the structural feature of the light source, from being affected by the beam compressor 50. 60). The stopper 60 essentially blocks the incident light of low luminance to prevent mutual interference with light of uniform distribution.

In addition, the collimating lens may be designed as a composite lens of thin lenses 37 and 38 to prevent aberration. An example of the data of each of the optical systems used in the parallel light illuminator thus designed is illustrated in the following table.

S1, S2, S3, S4, S5, S6, S7, and S8 used in this table are the elliptical reflector 30, the aperture stop 34, the collimating lens 37, 38 and the beam compressor 50, respectively. The reflective surface or the entrance / exit surface is shown.

In addition, the shape of the beam compressor is the optical axis so that the output light width is reduced compared to the incident light width in the optical axis direction to remove the dark portion while maintaining parallel beams in addition to the hollow conical lens shown in FIG. 2 and FIG. It may be provided with two convex lenses in which mutual focus is located at the same position on (1). Of course, the diameter of the convex lens on the light source side of the two convex lenses is larger than that of the other convex lenses.

The beam compressor may be implemented through other means not mentioned above.

It is a very useful invention that can be used as a lighting device such as a liquid crystal projector using PDLC by not only providing parallel light by employing the beam compressor as described above but also emitting uniform light.

Claims (9)

A light source; An elliptical reflector positioned to surround a rear surface of the light source such that the light emitted from the light source faces one direction; A collimating lens having a collimating lens positioned on a path of light reflected by the ellipsoidal reflector and converted into parallel light, wherein the collimating lens is disposed so as to face an exit surface of the collimating lens, and at the collimating lens side. A beam compressor for refracting the incident parallel light in the optical axis direction and keeping the compressed light in parallel; and having low luminance due to the geometry and position of the light source among the light beams reflected by the ellipsoidal reflector. Parallel light illumination device, characterized in that to output the uniform parallel light by compensating the emitted light. The parallel light illuminator of claim 1, wherein the light source is positioned at a first focal point F1 of the ellipsoidal reflector and converges reflected light at a second focal point F2. The collimating lens of claim 1, wherein the collimating lens has one focal point at the same point as the second focal point F2 of the ellipsoidal reflector such that the light emitted through the collimating lens becomes parallel light. Lighting equipment. The aperture stop of claim 1, further comprising: an aperture stop having a hole having a predetermined diameter formed on the optical axis such that only light reflected by the ellipsoidal mirror from the light emitted from the light source and formed within a predetermined diameter of the second focal point F2 is passed. Parallel light illuminator, characterized in that. The parallel light illuminator of claim 1, wherein the collimating lens comprises a plurality of composite lenses for aberration correction. The parallel light illuminator of claim 1, further comprising a stopper configured to block light in a region having low luminance due to the geometry and position of the light source at a central portion of the incident surface of the collimating lens. The parallel light illumination device according to claim 1, wherein the beam compressor is a hollow conical lens having an incidence plane and an outgoing plane inclined by a predetermined angle with respect to the optical axis and parallel to each other. 8. The light beam of claim 7, wherein the width of the dark region of the incident light is ø, and the beam compressor has its incidence plane and its exit plane inclined by an angle of θ with respect to the optical axis, and the shortest distance between the entrance plane and the exit plane is t. , When the refractive index is n, Parallel light illuminator, characterized in that to satisfy. The collimating lens of claim 1, wherein the beam compressor has the same focus on the same optical axis as the collimating lens so that parallel light emitted from the collimating lens is refracted and compressed in the optical axis direction while maintaining parallelism. A parallel light illuminator comprising a combination of two convex lenses whose diameters of adjacent convex lenses are larger than the diameters of other convex lenses.