JP4005726B2 - Projection display lighting device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a projection display using a light source and a light modulation element, and more particularly to an illumination device for a projection display using an optical semiconductor element as the light source.
[0002]
[Prior art]
Conventionally, mercury lamps and metal halide lamps obtained by adding halide compounds to the lamps have been mainly used as light sources for projection displays. These light sources realize a high luminous efficiency of 50 to 80 [lm / W] and a small interelectrode distance (arc length) of about 1 mm, and optical using a fly-eye lens as shown in FIG. The current situation is that it occupies the market almost as a lighting device.
[0003]
In FIG. 14A, 1 is a light source (lamp), 2 is a reflector, 3 is a UV filter, 4 is an IR filter, 5 and 6 are a first fly eye element and a second fly eye element constituting a fly eye lens. It is. Light emitted from the light source 1 is emitted to the dichroic mirrors 8, 9, and 10 through the fly-eye lens elements 5 and 6 and the lens 7. The light reflected by the dichroic mirror 8 enters, for example, a blue (B) liquid crystal panel (spatial modulation element) 13 via the mirror 11 and the lens 12. The blue optical image emitted from the liquid crystal panel 13 is combined with an optical image of another color by the combining prism 14 and enters the projection lens 15.
[0004]
The light transmitted through the dichroic mirror 8 is reflected by the dichroic mirror 9 and enters the liquid crystal panel 17 for green (G) through the lens 16. The green optical image emitted from the liquid crystal panel 17 enters the combining prism 14.
[0005]
The light transmitted through the dichroic mirror 9 enters the dichroic mirror 10 through the lenses 18 and 19. The light reflected by the dichroic mirror 10 enters, for example, a red (R) liquid crystal panel 23 via the lens 20, the mirror 21, and the lens 22. The red optical image emitted from the liquid crystal panel 23 enters the combining prism 14. The full color optical image emitted from the projection lens 15 is projected on the projection screen.
[0006]
In the apparatus described above, the light source by the lamp contains a lot of unnecessary light as shown in FIG. 14B, and these are shown in the UV filter 3 and the IR filter 4 which are shown in the current projection display in which the three primary color spectroscopic driving is general. Alternatively, it is removed using an optical filter such as dichroic mirror 8, 9, 10 or the like. As a result, it includes not only the cost increase due to the increase in parts, but also factors that cause various problems due to stray light or heat generation in the light shielding portion.
[0007]
In addition, there were many problems related to the basic problem of the lamp, such as slow rise of brightness after lighting, short life, use of mercury (environmental problem), and high voltage required at startup.
[0008]
[Problems to be solved by the invention]
An optical semiconductor element such as an LED can be given as a new light source candidate that changes to these. An optical semiconductor element can solve most of the above problems, but for example, an InGaAlP (red) LED 1 element usually has a forward voltage of about 2 V with a standard of use of 20 mA, so the light source power is only 0.04 W. Obviously, a large number of light sources for projection displays are required. Furthermore, these semiconductor elements have the disadvantage that the light diffusion angle is large and the refractive index of the semiconductor crystal is high, so that the transmission efficiency into the atmosphere is poor. For this reason, the directivity and the light extraction efficiency are improved by providing a reflector on the opposite side of the irradiation surface and covering the surface with a resin having a lens shape, as seen in a normal single LED lamp structure.
[0009]
However, when trying to obtain a configuration like conventional illumination with such a configuration, the shape of the LED reflector that satisfies the NA (numerical aperture) of the fly-eye lens and sufficiently covers the light distribution characteristics of the optical semiconductor element is large. Therefore, the arrangement pitch of each component is inevitably increased. Therefore, the light source shape and fly-eye lens in the case where a large number of the above-described single LED lamps are arranged are lengthened. As a result, not only the system becomes large and expensive, but also when the liquid crystal is used as a light valve, for example, the illumination angle The image quality such as contrast decreases due to the influence of the viewing angle and the like, and it is very difficult to construct an optical system with high light collection efficiency including the projection lens. Therefore, at present, such an optical system has not been realized. In addition, since the light source itself having such a configuration requires a lot of processing and accuracy, it has to be very expensive compared to the conventional lamp light source.
[0010]
Of course, it is conceivable to directly irradiate a light source with the above light distribution characteristics improvement processing just before these light valves, but the variation between optical semiconductor elements exists not only in the brightness but also in the emission wavelength Therefore, if division and superimposition are not performed, defects such as color unevenness and brightness unevenness, including partial brightness deterioration and astigmatism due to defects, individual aging variations, etc., appear, and high-quality projection display construction There was no groundbreaking optical means to hinder and comprehensively improve them.
[0011]
SUMMARY OF THE INVENTION Accordingly, the present invention has been made to devise means for avoiding the above-described problems using a surface light source such as an optical semiconductor element, and to provide an inexpensive and high-quality illumination device for a projection display.
[0012]
[Means for Solving the Problems]
  The present invention has a light diffusion type surface light source, the surface light source is opposed to an irradiation surface or a display surface, and more than a cross section of a space between the surface light source and the irradiation surface or the display surface. The surface light source is a structure having a kaleidoscope that surrounds a space formed from the vicinity of the outer periphery of the surface light source and the outer periphery of the irradiation surface or display surface with a reflecting mirror. Both polarizations having a size ratio of a half of a similar shape in a predetermined direction to an irradiation surface or a display surface, and performing light separation and phase rotation processing in the predetermined direction in the vicinity of the surface light source of the kaleidoscope F is a projection lens that projects light from the irradiation surface or display surface, where a is the size of the surface light source in the predetermined direction and a is the size of the irradiation surface or display surface. About values
F = b / (4a)
Size a of the surface light source in a direction orthogonal to the arbitrary direction ' The size of the irradiation surface or display surface in the same direction is b ' F = b for the F value of the projection lens that projects the light from the irradiation surface or the display surface ' / (2a ' ) Is satisfied.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0014]
First, main characteristic parts of the present invention will be described. That is, an optical semiconductor element in a wafer state that does not require special processing of the optical semiconductor light source is used as a surface light source with an area smaller than the illumination field and an equal aspect ratio. The space between is surrounded by a simple kaleidoscope. Then, the illumination means of the optical device that achieves the best light utilization efficiency with the highest F value, that is, the lowest cost projection lens specification is provided. Furthermore, by presenting various conditions such as an illumination distance for avoiding problems caused by the surface light source, conditions for achieving the minimum necessary illumination quality at the lowest cost are also presented.
[0015]
At the same time, the light source is simply covered with an intermediate medium having a refractive index larger than 1, thereby helping to match the refractive index of the semiconductor crystal and improving the internal reflectivity and the critical angle. In addition, it is possible to provide an inexpensive, high-efficiency, high-quality optical device by providing the optimum illumination means even when both polarized light needs to be used or when there are significant conditions in the light source divergence angle. It is possible to provide.
[0016]
Hereinafter, the necessity and structure principle of the structure according to the present invention will be specifically described.
[0017]
  FIG. 1 (a) shows the present invention.PremiseIt is an embodiment. 31 is a surface light source, and 32 is an illumination field. The space around the surface light source 31 and the surrounding of the illumination field 32 is surrounded by, for example, a mirror (guide scope) 33. However, if the purpose is satisfied, either a state filled with resin or a configuration with a prism may be used.
[0018]
Here, for the sake of simplicity, the illumination field 32 is assumed to be a rectangle having an arbitrary aspect ratio, and only the illumination optical unit is shown in a monochromatic configuration.
[0019]
  The surface light source 31 is, for example, a red LED light source aggregate, and has a shape that is smaller in both vertical and horizontal dimensions than the illumination field 32. When the effective outer peripheral end of the surface light source 31 and the effective outer peripheral end of the illumination field 32 are surrounded by the mirrors 33a, 33b, 33c, and 33d without a gap and viewed from the central observation section “P” of the illumination field 32, the surface light source 31 The mirror images by the mirrors 33a, 33b, 33c, and 33d are shown in the figure.1As shown in FIG. 5B, the light source is observed as an ellipsoidal light source having a radius determined by the dimensional ratio between the illumination field 32 and the surface light source 31.
[0020]
That is, light emitted from a plurality of arbitrary emission angles from all LEDs of the surface light source 31 reaches the observation point “P” of the illumination field 32, and the distance between the surface light source 31 and the illumination field 32 is sufficient. If the projection system (projection lens system) 34 is provided with a divergence angle equal to or greater than the maximum illumination light by the light source mirror image as the F value, a highly efficient and uniform projection optical device can be obtained. FIG. 1C shows the state of diffusion of the emitted light from one LED of the surface light source 31.
[0021]
The F value achieved by the projection system (projection lens) 34 does not necessarily need to cover the entire range, the light source emits light in a completely diffused state, and reflection loss due to the mirrors 33a, 33b, 33c, and 33d is almost all. This effect is noticeable only when there is not.
[0022]
As described above, the basis of the present invention is that the surface light source 31 has a small shape in any cross-sectional direction of the illumination field 32 (irradiation surface or display surface), and the vicinity of the outer periphery of the surface light source 31 and the irradiation field 32. Mirrors 33a, 33b, 33c, and 33d that surround an arbitrary space formed from the outer periphery of the mirror with a reflecting mirror, that is, a kaleidoscope (kaleidoscope) 33 structure. That is, the kaleidoscope 33 is configured by the upper and lower and left and right mirrors 33a, 33b, 33c, and 33d.
[0023]
FIG. 2 shows the basic concept of the above-described apparatus. For the sake of simplicity, the embodiment is based on a single color configuration, the surface light source 31 and the illumination field 32 are arranged symmetrically with respect to the optical axis, and the figure shows a two-dimensional display of a cross section including the light source.
[0024]
The size of the surface light source 31 is “a”, the size of the illumination field 32 is “b”, and the distance between the surface light source 31 to the illumination field 32 is “d”. Then, it is assumed that the surface light source 31 end to the illumination field 32 end are surrounded by the mirrors 33a, 33b, 33c, and 33d facing each other without a gap. At this time, the surface light source 31 and the light source mirror image 35 viewed from the central observation point “P” of the illumination field 32 have a radius “r” from the surface light source 31 to the intersection “O” on the extension line of the mirrors 33a and 33b. Line up on the circle 36.
[0025]
If the illumination distance “d” is sufficiently secured, the mirror image 35 is allowed to be regarded as a circle 36. Therefore, the maximum illumination angle to the observation point “P” is an angle “θ” formed by the tangent line from “P” to the circle 36 with the optical axis, and from the illumination field 32 to the extended intersection “O” of the mirrors 33a and 33b. When the distance is “L” and the optical axis angle of the mirrors 33a and 33b is “φ”,
r = d × a / (ba) (1)
L = d × b / (ba) (2)
φ = tan^-1{(Ba) / (2d)} (3)
Therefore, the illumination angle “θ” is
θ = sin^-1(R / L) = sin^-1(A / b) (4)
It becomes. Therefore, the minimum F value of the projection system that can cover all the illumination angles is
F = 1 / (2sin θ) = b / (2a) (5)
And does not depend on the illumination distance “d”.
[0026]
Therefore, if the dimensional ratio between the light source and the illumination field 32 has the same ratio when viewed from any direction, that is, if it is similar, the surface light source 31 and its mirror image 35 viewed from the observation point “P” have a radius “r”. Observed as a spherical shape.
[0027]
In general, the projection lens element has a circular shape when viewed from the optical axis because of its workability. Accordingly, the projection lens entrance pupil viewed from the optical axis has a circular shape symmetrical to the optical axis. It is possible to obtain the maximum pupil passage efficiency with the largest F value by making a similar shape. (F value: Effective angle (brightness) index of optical system, θ: Maximum effective angle)
F = 1 / (2 sin θ) = b / (2a) (repost (5))
If this condition is ensured, the most efficient projection display can be constructed. If the F value Ft of the projection lens is Ft <= F = 1 / (2 sin θ) = b / (2a), the illumination light can be projected without loss.
[0028]
The above is a design method at the time of a light source having an emission characteristic close to perfect diffusion, but depending on the optical semiconductor element, it has a remarkable characteristic in the light divergence angle, and `` θ<sub>L</sub>"An output angle greater than or equal to" may not be considered effective.
[0029]
An application example of the present invention when an effective emission angle is given to the light source will be described with reference to FIG.
[0030]
The effective emission angle of the optical semiconductor element is “θ<sub>L</sub> The other conditions are the same as those in the previous section using FIG. Here, the converging emission angle range “θ” of the surface light source 31 is larger than the angle “φ” formed by the kaleidoscope 33.<sub>L</sub>"Is large, the light source image seen from the observation point" P "exists on a circle 36 having a radius" r "centering on the extended line intersection of the mirrors 33a and 33b as in the previous section.
[0031]
Here, the light distribution characteristic of the surface light source 31 is “θ<sub>L</sub>”, So from the circle 36“ θ<sub>L</sub>”And the angle“ θ ”formed by the light beam emitted from the mirror image 35 on the circle 36 reaching the observation point“ P ”with the optical axis.<sub>T</sub>"Is the maximum illumination angle for the observation point" P ".
[0032]
Therefore, the angle between the mirror image 35 and the center “O” of the circle 36 and the optical axis is expressed as “θ<sub>M</sub>"given that,
θ<sub>L</sub>= Θ<sub>M</sub>+ Θ<sub>T</sub>                                ... (6)
r sinθ<sub>M</sub>= (L-r cosθ<sub>M</sub>) Tanθ<sub>T</sub>        ... from (7)
sinθ<sub>T</sub>= R sinθ<sub>L</sub>/ L (8)
Therefore, the light distribution characteristic condition “θ<sub>L</sub>The F value of the most effective projection system when “” is added is obtained from the equations (8), (1), and (2)
F = 1 / (2 sinθ<sub>T</sub>) = B / (2a sinθ<sub>L</sub>(9)
It becomes.
[0033]
Here, when a liquid crystal is used as a light modulation element of a projection display, there are many cases where only linearly polarized light is used as illumination effective light. If the semiconductor element is linearly polarized light such as a semiconductor laser, the present invention described so far can be applied as it is, but at the time of random polarization such as an LED, it is separated into two orthogonally polarized light using a PBS element or the like. It is desirable to apply a method of improving the light utilization efficiency by adding a phase rotation process on one side.
[0034]
In the ordinary lamp light source, the above-described method is used in the vicinity of the fly-eye second element (6 in FIG. 14 (a)) that performs division and superimposition. As for the means, if the conditions after the illumination system do not change, a technique is required in which the illumination effective light is halved in an arbitrary direction and such processing is applied using this gap.
[0035]
Even in the case where such both polarized light utilization means are provided in the present invention, it is necessary to perform a process of converting random polarized light into linearly polarized light after applying a means for halving the illumination angle in an arbitrary direction. From the description so far, the means for halving the illumination angle in the arbitrary direction in the expressions (5) and (9) is simply separated from the similar shape of the illumination field 32 and the surface light source 31 by both polarized light utilization means. Although the importance of the condition described later is proved only by setting the shape of the surface light source to ½ in the direction of the light source, FIG. 4 is used assuming that both polarized light using means are applied to the light source side as an example. I will explain. FIG. 4 shows an example in which the illumination effective light is halved in the downward direction (short side direction).
[0036]
As shown in FIG. 4A, the long side dimension “a” of the surface light source 31 is used.<sub>1</sub>”, Short side dimension“ a ”<sub>2</sub>"Long side dimension of lighting field 32" b<sub>1</sub>", Short side dimension" b<sub>2</sub>It is assumed that both polarized light utilization means shown in FIG. 4B are applied in the short side direction.
[0037]
If both polarization utilizing means are described with reference to FIG. 4B, the p-polarized component indicated by the dotted line emitted from the surface light source 31 passes through the PBS element 44 and is aligned with the s-polarized light by the polarization rotating plate 46. The light is emitted into the ride scope 33. On the other hand, the s-polarized component indicated by the solid line in the figure emitted from the surface light source 31 is reflected by the PBS element 44, further redirected by the mirror 45 and emitted into the kaleidoscope 33. The PBS 44 element and the mirror 45 are formed by prisms 47 and 48. In general, the prisms 47 and 48 have the same size. Depending on the emission conditions of the light source 31, a convex lens (not shown) is disposed between the light source 31 and the prism 47, the outer boundary of the prisms 47 and 48 is mirrored, and the PBS element 44 and the mirror 45 are processed into a concave lens shape. The light utilization efficiency may be improved.
[0038]
Even in such a case, since the relationship between the kaleidoscope 33 and the projection system F value after the irradiation surface 32 is already derived by the equations (5) and (9), when the shapes of the prisms 47 and 48 are substantially equal, Total value “2a” of the prisms 47 and 48<sub>2</sub>"And long side" a<sub>1</sub>If the combined light source formed by “” is formed to have a similar shape to the illumination field 32, the present invention described so far can be applied as it is. That is, the polarization separation direction when using both polarized light is a<sub>2</sub>, B<sub>2</sub>When the side direction
a<sub>1</sub>: 2a<sub>2</sub>= B<sub>1</sub>+ B<sub>2</sub>                    (10)
The projection system F value when the diffused light source shape is
F = b / (4a) (11)
And the effective light source divergence angle is `` θ_L”Is applied, the projection system F value is F = b / (4a sin θ_L(12)
The effectiveness of setting is verified.
[0039]
The verification of the specific embodiment of the present invention has been described above from the observation point on the optical axis. However, the light source and the light source mirror image by the kaleidoscope viewed from the irradiation observation position other than the optical axis are also mirrors as shown in FIG. It exists on a circle 36 having a radius r centered on the intersection of the extended lines 33a and 33b.
[0040]
That is, in FIG. 5, the illumination light chief rays at the irradiation surface peripheral observation points “P” and “Q” are approximately the inclination angle “θ” of the kaleidoscope 33. Therefore, when a liquid crystal that is easily affected by the viewing angle is used as the light modulation element, a lens 37 having a focal length “L” is disposed immediately before the illumination field 32, thereby illuminating light chief rays to all illumination fields. Can be substantially parallel to the optical axis. That is, the focal length “f” of the lens 37 is
f = L = d × b / (ba) (13)
When the mirror reflection efficiency is so large that it cannot be ignored, it is often possible to obtain a result that is preferably set slightly shorter than the focal point obtained from the equation (13).
[0041]
On the other hand, when the light modulation element is not affected by the viewing angle, it is often possible to obtain a more preferable result by slightly changing the focus under the projection system conditions.
[0042]
As shown in FIG. 6 (a), in most cases, the object 71 is imaged by the lens 71. The central portion has the widest effective angle θ1 and is balanced, and the outer peripheral direction is closer to the outer peripheral portion from the optical axis. The effective angle of becomes narrower. FIG. 6B shows this state represented by the projection lens entrance pupil shape from the main observation point of the illumination field having a wide aspect ratio. In the figure, the left side is the case where the focus of the condenser lens is “L”, and the right side of the figure is that the focus of the condenser lens is a short focal point considering the peripheral pupil of the projection system, and the chief ray of illumination light at the outer periphery Simulates a slightly focused state. In this way, it is obvious that even with a projection lens or the like having a small peripheral light amount ratio, the peripheral light amount is hardly deteriorated and a good result can be obtained.
[0043]
In summary, the focal length “f” of the condenser lens 37 to be arranged is
f ≦ L = d × b / (ba) (14)
Is desirable.
[0044]
An LED (light emitting diode) is considered to be an effective light source to which the present invention is applied. However, as described in the conventional section, a very large number of projection display light sources are required for each color. It is obvious that conventional LEDs cannot be arranged in high density, which is clearly less preferable than the equations (5), (9), (11), and (12), and a large number of light sources configured individually. Since it is a body, it becomes very expensive.
[0045]
Originally, LEDs are manufactured with hundreds of thousands of LEDs on a several inch wafer, so the light source is in a state where an arbitrary range suitable for application of the present invention is connected in the wafer state with some modifications. If this is manufactured, the steps after the division processing are omitted, and even if a considerable amount is used, it is very advantageous in terms of cost.
[0046]
However, many semiconductor crystals used for LEDs have a high refractive index of N (refractive index) = 3.5, and when released into the atmosphere as they are, the transmittance is low as shown by the thin solid line on the graph of FIG. The critical angle is about 16 degrees, and it is not effectively emitted into the kaleidoscope.
[0047]
Therefore, as shown in FIG. 8, by filling an arbitrary range within the kaleidoscope 33 from the surface light source 31 with a medium 39 having a refractive index larger than that of the atmosphere, transmission is performed as shown by a thick dotted line in FIG. The rate can be improved.
[0048]
If the filling range “t” of the medium 39 has an arbitrary thickness or more, most of the light source rays in the vicinity of the critical angle are reflected in the medium 39 at the interface of the kaleidoscope 33 with respect to the optical axis angle “φ”. Therefore, the angle of the optical axis of the light after reflection “θ_M”Is the angle of the optical axis before reflection“ θ_BFor
θ_M= Θ_B-2φ (15)
It becomes. For this reason, it has the effect of increasing the light source critical angle as shown by the thick line in FIG. 7 and increasing the light emission efficiency itself to the outside of the crystal. That is, at least the vicinity of the surface light source of the kaleidoscope is filled with a medium having an arbitrary refractive index not less than the atmospheric refractive index and not more than the semiconductor refractive index.
[0049]
However, if the thickness “t” of the medium 39 is too large, the light source size “a” described so far and the radius “r” of the circle 36 where the light source mirror image (not shown) exists are “a ′” and “r ′”, respectively. Therefore, the optimum thickness value is determined from the light source and projection conditions.
[0050]
Most of the front projection type projection displays are provided with a turning (knitting center) vertically upward with respect to the modulation element, and project and image upward. This has two reasons that it is advantageous to ensure the contrast performance from the convenience of use and the viewing angle characteristics when a large number of liquid crystals are used as light valves.
[0051]
In such an optical system of the projection display, the center of the irradiation surface “P” shown by the solid line in FIG. 9 is arranged rather than arranging the light source on the straight line extending in the direction of the liquid crystal surface from the center of the liquid crystal shown by the dotted line in FIG. It is obvious that it is more efficient than the projection condition to install the extension line of the mirror of the kaleidoscope 33 on a straight line 34b connecting the entrance pupil position 34a of the projection system 34 shown in an image. . That is, in a projection display having a deviation between the optical axis of the projection lens and the center of the irradiation display surface, there is an intersection point on the extension line of the kaleido mirror near the extension line originating from the center of the projection lens entrance pupil and passing through the center of the irradiation surface. This is an effect of the characteristic configuration. In other words, this is an effect due to the arrangement when there is a deviation between the optical axis of the projection lens and the center of the irradiation display surface.
[0052]
Next, a description will be given of a configuration in which the distance d between the surface light source and the irradiation surface has a distance that is not less than 2 times and not more than 6 times the shortest side of the irradiation surface, that is, the necessity of setting an appropriate illumination distance range between the light source and the illumination field.
[0053]
As shown in FIG. 10, the illumination distance is set to “d” without changing the size of the light source 31 in which a sufficient illumination distance “d” is secured.₂"," D₁As the light source 31 viewed from the illumination field observation point “P” increases, the number of mirror images decreases and the error from the circular model gradually increases, so that it must be considered as a polygon.
[0054]
FIG. 11 shows a process of obtaining the illumination F value while keeping the light source mirror image in a polygonal shape.
[0055]
As a result, the mirror image number N viewed from the observation point Ps with the illumination distance and the illumination range size ratio as variables is shown in FIG. 12A, and the minimum F value of the illumination light reaching the observation point Ps is shown in FIG. It was shown to.
[0056]
Further, based on these, the projection system efficiency when projected by the projection system having the F value defined by the equation (5) when there is no loss and the light source is emitted in a completely diffused state is shown. FIG. 12D shows an enlarged view of the vicinity of 100% efficiency in FIG.
[0057]
FIG. 12B shows the F value converted from illumination from a polygonal vertex protruding from a circle. When the illumination distance is short with respect to the illumination field, the F value necessary for the projection system needs to be considerably small. It shows that there is.
[0058]
Even if these losses are at an acceptable level, if the cross section shown in FIG. 11 is in the direction of the short side of the illumination field, the illumination distance “d” remains fixed as the cross section rotates, and the light source dimension “ Since “a” and the illumination range “b” are continuously expanded, a luminance wave as shown in FIG. 12C is generated in a circular shape on the screen and cannot be allowed as image quality. As a result, FIG. The F value of the projection system indicated by () is an indispensable condition and is not appropriate in terms of cost conditions.
[0059]
Therefore, by providing the illumination distance at least twice as long as the short side dimension of the illumination field, as can be seen from FIG. 12 (c), due to the polygonal surface light source main factor in the projection system F value obtained by equation (5). The projection system loss is 5% or less, which is the minimum allowable level. On the other hand, when the maximum value is 6, the above-mentioned projection system loss is about 0.5%, and necessary and sufficient quality is secured, and securing an illumination light path length longer than this has little improvement effect on illumination quality. In addition, since the mirror image exceeds 10, the illumination light rate in the vicinity of the maximum mirror image deteriorates in a kaleidoscope having a finite reflection efficiency, and as a result, a desirable luminance cannot be obtained.
[0060]
Here, the process of determining the illumination F value in the polygon model will be described with reference to FIG.
When the illumination distance d is reduced in the illumination system using the combination of the LED surface light source and the guide scope, the error is increased in the simple circular model. Therefore, when a simulation is performed with a polygonal model in a region where d is small, the following results.
[0061]
Now, let us consider increasing d from O, assuming that the sizes of a and b are fixed. r = d · a / (ba)
L = d · b / (ba)
φ = tan^-1((Ba) / (2 · d)).
[0062]
If the distance between the point where the extension of the light source mirror image S1, S2 and the optical axis intersect with the point O is Ln using the green drawing in the figure,
Ln = r / cos (2 ・ n ・ φ)
The maximum value of the integer n satisfying Ln <= L is the number of observable mirror images N.
N = [cos^-1(A / b) / (2.tan^-1((Ba) / (2d)))]
At this time, if the end (vertex) of the mirror image of N is CN, the angle CNOP is (2N + 1) φ
Therefore, θ =
tan^-1[{Sin (2 · N + 1) · φ} / {(b / a) cosφ−cos (2N + 1) φ}]
Therefore, the illumination F value in the polygonal model is determined by F = 1 / (2 · sin θ).
[0063]
FIG. 13A shows the relationship between the illumination distance and the number of light source reflection images created based on the above results, and FIG. 13B shows the relationship between the illumination distance and the illumination F value. The angle θ deteriorates with the circular model set F value as a vertex. This means that if the illumination distance is short, the illumination angle expansion due to the polygonal vertex is further increased. To maintain efficiency (effective use of light), it is necessary to set a brighter F value than the circular model. There is a disadvantage in terms of cost.
[0064]
FIG. 12C is a graph obtained by graphing the above results in terms of projection efficiency when the projection system F value is set using a circular model. FIG. 12 (d) is an enlarged view thereof. This graph shows a case where the light source mirror image is viewed from the center of illumination, and the efficiency changes in the direction of the horizontal axis as it moves in the diagonal direction of the liquid crystal. This means that illumination (projection) unevenness occurs, and even a planar shape is not suitable for projector illumination.
[0065]
Representative values are shown in FIG. 14 from the viewpoint of efficiency and luminance unevenness.
[0066]
As can be seen from this representative value, it can be seen that brightness unevenness of about 5% occurs if there is no illumination distance of about twice the diagonal.
[0067]
From the above description, if the present invention is used, an optical semiconductor element that can be replaced with a conventional lamp can be made into a simple, compact, and inexpensive illumination system configuration as compared with a fly-eye or the like while maintaining an inexpensive wafer state. . In addition, it is proved that a high-efficiency and high-quality projection display system can be constructed.
[0068]
In the present invention, the smaller the light source, that is, the higher the efficiency and the higher the density, the cheaper and more compact the optical system can be constructed. Therefore, the light emission efficiency of the optical semiconductor device that can be plotted in a straight line on the logarithmic graph can be improved. It is a very promising and useful illumination optical device at present and in the future.
[0069]
【The invention's effect】
As described above, the present invention can provide an illuminating device that can avoid a problem using a surface light source such as an optical semiconductor element and can obtain inexpensive and high-quality illumination.
[Brief description of the drawings]
FIG. 1 of the present inventionPremiseThe schematic block diagram which shows embodiment, the light source mirror image figure seen from the illumination field observation point, and explanatory drawing of the emitted light of a surface light source.
FIG. 2 is a view for explaining the principle of the apparatus of the present invention.
FIG. 3 is a diagram showing an application example of the present invention when a surface light source has directivity.
FIG. 4 of the present inventionOne concreteExplanatory drawing at the time of giving both polarization utilization means which is embodiment.
FIG. 5 is an explanatory diagram of an embodiment of the present invention when a light modulation element has viewing angle characteristics.
FIG. 6 is a diagram showing an embodiment of the present invention when the light modulation element has no directivity and the projection system has an effective angle deviation.
7 is a graph showing an effect example when the light emission efficiency means in the embodiment of FIG. 8 is applied.
FIG. 8 is an explanatory view of an embodiment of the present invention in which a semiconductor crystal has a high refractive index, to which light emission efficiency improving means is applied.
FIG. 9 is a diagram showing another embodiment of the present invention when a projection is added to the projection system.
FIG. 10 is a diagram for explaining a problem when the illumination distance is short.
11 is an explanatory diagram showing an illumination angle calculation process when a mirror image is regarded as a polygonal light source when the illumination distance shown in FIG. 10 is short.
FIG. 12 is an explanatory diagram in which the result of mirror image analysis using the calculation result obtained in FIG. 11 is graphed.
FIG. 13 is a diagram illustrating an example of representative numerical values of the relationship between the illumination distance and the luminance efficiency.
FIG. 14 is a schematic diagram of an optical system of a conventional transmissive liquid crystal light valve projector and a diagram showing an emission spectrum graph of a main lamp.
[Explanation of symbols]
31 ... surface light source, 32 ... illumination field, 33 ... guide scope.

Claims (3)

A surface light source of a light diffusion type, the surface light source facing the irradiation surface or the display surface, and having a surface shape smaller than a transverse cross section of the space between the surface light source and the irradiation surface or the display surface There further is a structure having a kaleidoscope enclosed in reflector between sky periphery around the Ru is formed from the outer circumferential vicinity of the irradiation surface or the display surface of the surface light source,
The surface light source has a dimensional ratio of a half of a similar shape to the irradiation surface or the display surface in a predetermined direction;
Both polarized light utilization means for performing light separation and phase rotation processing in the predetermined direction are provided near the surface light source of the kaleidoscope,
F value of a projection lens that projects light from the irradiation surface or display surface, where a is the size of the surface light source in the predetermined direction and b is the size of the irradiation surface or display surface.
F = b / (4a)
The F value of the projection lens that projects light from the irradiation surface or display surface when the size a ′ of the surface light source in the direction orthogonal to the arbitrary direction is b ′ and the size of the irradiation surface or display surface in the same direction is b ′. F = b ' / (2a ' )
An illumination device for a projection display, characterized in that: The effective diffusion angle (half angle) of the surface light source is θ _L , and both polarized light using means for performing light separation and phase rotation processing in the predetermined direction are provided near the surface light source of the kaleidoscope,
When the size of the surface light source in the predetermined direction is a and the irradiation surface or display surface size is b, the F value of the projection lens that projects light from the irradiation surface or display surface
F = b / (4a sin θ _L )
The F value of the projection lens that projects light from the irradiation surface or display surface when the size a ′ of the surface light source in the direction orthogonal to the predetermined direction is b ′ and the size of the irradiation surface or display surface in the same direction is b ′. about
F = b ′ / (4a ′ sin θ _L )
The projection display illumination device according to claim 1, wherein the following condition is satisfied . The illumination device for a projection display according to claim 1 or 2 , wherein at least the vicinity of the surface light source of the kaleidoscope is filled with a medium having a refractive index not lower than the atmospheric refractive index and not higher than the semiconductor refractive index. .

Images