JP5725138B2 - Lighting device and projector - Google Patents

Description

  The present invention relates to an illumination device and a projector using a laser as a light source.

  In order to reduce the size, power consumption, color gamut, and life of a projector, it is considered to use a laser as a light source. The high coherence and monochromaticity of the laser can be applied to a diffractive optical element (DOE), which is difficult to use with a conventional lamp light source, and cannot be considered with a conventional refractive optical system. An element having multiple functions can also be realized. By using DOE, the optical system can be simplified and downsized.

JP 2007-33576 A

  The above Patent Document 1 shows a configuration of an illumination device to which the above DOE is applied. According to Patent Document 1, by using a laser light source that oscillates laser light as a light source and having a DOE for conversion to rectangular illumination, the apparatus becomes larger and complicated, or the cost of the apparatus increases. It is shown that it is possible to efficiently illuminate a predetermined surface while suppressing the above.

However, Patent Document 1 does not consider the DOE diffraction angle. The limitation on the diffraction angle of the DOE will be described. The spatial frequency f of the phase amplitude modulation of the DOE and the maximum spread angle (diffraction angle) θ of the light beam emitted from the DOE have the following relationship.
tanθ∝f
In order to further reduce the size of the illumination device as compared with the configuration of Patent Document 1, the maximum spread angle θ of the light beam emitted from the DOE may be increased. However, in order to increase the angle θ, it is necessary to reduce the spatial frequency f of the DOE. However, a more advanced fine processing technique is required, which increases the cost. An object of the present invention is to realize a small illuminating device without increasing the angle θ.

In order to solve at least a part of the above problems,
An illumination device according to this application example includes a light source device that emits coherent light, a diffractive optical element that shapes the coherent light into a light beam having a predetermined luminance distribution, and a light beam emitted from the diffractive optical element for making a parallel light beam. It is characterized by comprising a collimating lens and a curved mirror disposed between the diffractive optical element and the collimating lens to increase the divergence angle of the light beam emitted from the diffractive optical element.

If the divergence angle of the light beam emitted from the diffractive optical element is small, the distance between the surface to be illuminated and the diffractive optical element must be increased in order to obtain a desired size of illumination light. In order to increase the divergence angle of the emitted light beam from the diffractive optical element, a more advanced fine processing technique is required, which causes an increase in cost. By placing a curved mirror between the diffractive optical element and the collimating lens to increase the divergence angle of the light beam emitted from the diffractive optical element, the distance between the diffractive optical element and the surface to be illuminated can be reduced and inexpensive. In addition, the lighting device can be downsized.

As a preferred mode of this application example, the curved mirror is desirably a convex mirror. Thereby, it can be set as a return | turnback optical system, a desired illumination area can be illuminated, and size reduction of an illuminating device is realizable.

As a preferred mode of this application example, it is desirable that the curved mirror is a concave mirror. Thereby, it can be set as a return | turnback optical system, a desired illumination area can be illuminated, and size reduction of an illuminating device is realizable.

Moreover, as a preferable aspect of this application example, it is desirable that the surface shape of the curved mirror is an aspherical surface. Thereby, the distortion aberration of a mirror can be suppressed and the high illumination efficiency of an illuminating device can be implement | achieved.

Moreover, as a preferable aspect of this application example, it is desirable that the curved mirror is disposed at a substantially intermediate position between the diffractive optical element and the collimating lens. Thereby, further miniaturization of an illuminating device is realizable.

  As a preferable aspect of this application example, a projector including the illumination device described in the above application example is desirable. As a result, the projector can be reduced in size, simplified, and reduced in cost.

A preferable aspect of this application example is a projector, each of which includes a plurality of light source devices that emit coherent light of a predetermined color, a diffractive optical element that shapes the coherent light into a light beam having a predetermined luminance distribution, and a diffraction A collimating lens for converting a light beam emitted from the optical element into a parallel light beam, a spatial light modulation element that has pixels and modulates the light beam emitted from the collimating lens according to image information, and is emitted from the spatial light modulation element A projection lens for projecting the luminous flux onto the irradiated surface, a collimating lens, and the spatial light modulation element. The luminous flux of a predetermined color incident on the spatial light modulation element is set at a different incident angle for each color, Is provided between the diffractive optical element and the collimating lens, and controls the ray angle of the light beam of a predetermined color. It is desirable, characterized in that a curved mirror.
As a result, a color image can be projected with one spatial light modulation element, and the distance between the diffractive optical element and the surface to be illuminated can be reduced, and the projector can be miniaturized, simplified, and reduced in cost.

1 is a schematic diagram illustrating a schematic configuration of a lighting device according to Embodiment 1. FIG. It is the figure which showed the schematic shape of the computer generated hologram. It is the figure which showed typically the surface shape of the computer generated hologram. It is the figure which showed typically about the 1st diffraction region of DOE. It is a line graph which showed the distance from DOE to a convex lens, and the distance from DOE to a parallelization lens. It is the figure which showed typically the aspect of the modification of Example 1. FIG. FIG. 6 is a schematic diagram illustrating a schematic configuration of a lighting device according to a second embodiment. It is the figure which showed typically the aspect of the modification of Example 2. FIG. FIG. 6 is a schematic diagram illustrating a schematic configuration of a lighting device according to a third embodiment. FIG. 10 is a schematic diagram illustrating a schematic configuration of a projector according to a fourth embodiment. FIG. 10 is a schematic diagram illustrating a schematic configuration of a spatial color separation projector according to a fifth embodiment. It is a schematic diagram which shows schematic structure of the spatial light modulation element regarding a spatial color separation system. It is a schematic diagram which shows schematic structure of the illuminating device regarding a spatial color separation system.

Example 1
The aspect of Example 1 regarding the illuminating device of this invention is demonstrated using FIGS.
FIG. 1 is a schematic diagram illustrating a schematic configuration of the illumination device according to the first embodiment. In FIG. 1, an illuminating device 1 includes a light source device 2, a diffractive optical element (DOE) 3, a convex lens 4 as an optical element, and a collimating lens 5, and illuminates an illuminated surface 6. The outline of the illumination device 1 shown in FIG. 1 will be described below.
From the light source device 2, coherent light L1 is emitted, and the coherent light L1 enters the DOE 3. A light beam L2 shaped into a predetermined luminance distribution is emitted from the DOE 3 and enters the convex lens 4. However, where the focal length of the convex lens 4 to be used f4 (not shown) using the distance D ₂ of DOE3 and the convex lens 4, meets f4 <D _2/2 the relationship. Thereby, the condensing angle θ _L3 of the light beam L3 emitted from the convex lens 4 is larger than the condensing angle θ _{L2 of the} light beam _L2 . Then, the light beam L3 is condensed at the condensing point P _f4 , diffused again, and enters the collimating lens 5. The focal length f5 of the collimating lens 5 is arranged to be substantially equal to the distance between the condensing point P _f4 and the collimating lens 5. The collimating lens 5 emits a parallel light beam L4 and reaches the illuminated surface 6.

  Here, the light source device 2 is a light source device that emits coherent light, and a semiconductor laser is used in this embodiment. Note that any light source that emits coherent light is applicable, such as an LD-excited solid state (DPSS) laser or a super luminescent diode (SLD). Further, the present invention can also be applied to a light source in which the above light source devices are arranged in an array in a one-dimensional or two-dimensional direction to emit a plurality of light beams.

Moreover, DOE3 in the present Example 1 is a computer generated hologram (CGH: Computer Generated Hologram). Hereinafter, the computer generated hologram will be described.
A computer generated hologram is an element capable of controlling the luminance (or phase) of an emitted light beam by applying phase and amplitude modulation to incident coherent light. In the present embodiment, the luminance distribution of the incident beam is converted into a uniform luminance distribution with a rectangular shape, and the illuminated surface 6 having a rectangular shape can be illuminated uniformly and efficiently.
A schematic diagram showing a schematic shape of a computer generated hologram is shown in FIG. 2 (plan view) and FIG. 3 (sectional view taken along line A in FIG. 2). On the surface of the computer generated hologram, a square region having a pixel length p has an uneven shape having different depths as shown in FIG. 3, and a square region having a different depth for each hatching is two-dimensional as shown in FIG. They are arranged in an array. The uneven shape is made of a material such as quartz glass or resin, and the luminance distribution of the emitted light can be controlled by giving different phase differences in each region to the incident light.

When a predetermined luminance distribution is given to the emitted light, the uneven shape is optimized using a computer. Examples of optimization methods that are mainly used include methods such as an iterative Fourier transform method and a simulated annealing method (SA method).
The surface uneven shape is produced by a so-called nanoimprint technique in which a surface is transferred from a mold (mold) created by a high-precision micromachining technique such as a semiconductor process to a substrate or the like by thermal transfer. At present, the pixel length p in FIG. 3 is limited to about sub μm.
Note that the DOE 3 used in the present invention may be manufactured by another conventionally used method as long as a desired shape can be formed. The DOE 3 is not limited to a computer generated hologram, and other surface relief type diffractive optical elements, volume type diffractive optical elements produced by a two-beam interference method, or the like may be used.

FIG. 4 shows the high-order diffracted light emitted from the computer generated hologram (DOE 3). The DOE 3 emits second-order, third-order,..., M-order diffracted light in addition to the first-order diffracted light giving a predetermined luminance distribution. In addition, there is zero-order light that is emitted without being diffracted among incident light. If the region from which the first-order diffracted light is emitted is called a first-order diffraction region, the grating is obtained using the maximum emission angle θ _m of the light beam emitted from the DOE 3 to the m-th order diffraction region, the pixel length p, and the wavelength λ of the incident light. From the equation, it can be expressed by the following equation.
2 psin θ _m = mλ (m = ± 1, ± 2...)
m is an integer.
From this relational expression, the maximum emission angle θ ₁ of the light beam emitted to the first-order diffraction region can be expressed by the following expression.
sin θ ₁ = λ / 2p
If the wavelength λ of the coherent light L1 emitted from the light source device 2 used in this embodiment is 532 nm and the pixel length p of the DOE (computer hologram) 3 is 1 μm, θ ₁ is 15.4 °.

In FIG. 1, when the size S in the x-axis direction of the illuminated surface 6 is 16 mm, the exit angle θ _L2 from the DOE 3 is 15.4 °, and therefore the first-order diffraction region of the DOE 3 is equal to the size S. The distance D ′, that is, the distance D ′ from the DOE 3 to the collimating lens 5 when the convex lens 4 is not provided is expressed by the following equation, and D ′ can be derived as 29 mm.
D ′ = (S / 2) / Tanθ _L2

On the other hand, according to the present embodiment in which the convex lens 4 is arranged between the DOE 3 and the parallelizing lens 5, when D ₂ = 10 mm and the focal length f4 of the convex lens 4 is 3 mm, the condensing point P _{f4 of the} light beam L3 from the convex lens 4 The distance D ₃ is calculated to be 4.29 mm. As a result, the condensing angle θ _L3 of the light beam L3 at the condensing point P _f4 is 32.7 °, and the distance (focal length f5) between the condensing point P _f4 and the collimating lens 5 is derived as 12.4 mm. . As a result, the distance D from the DOE 3 to the collimating lens 5 is 26.7 mm, and the configuration in which the convex lens 4 is arranged makes it possible to reduce the illumination device 1 by about 2 mm.

Here, as for the convex lens 4, any element having a positive focal length and a function of increasing the outgoing angle θ _L3 of the outgoing light beam than the incident angle θ _L2 of the incoming light beam may be used. For example, if an aspherical convex lens is used, the distortion aberration can be reduced compared to when a spherical lens is used, and the illuminated surface 6 can be efficiently illuminated. Further, for example, if a ball lens having a shorter focal length is used, the lighting device 1 can be further downsized. For example, if a diffractive lens represented by a Fresnel lens is used, a thin element can be used. In addition to the Fresnel lens described above, the diffractive lens includes binary elements, hologram elements, and the like. By using the diffractive lens, the lighting device 1 can be reduced in weight.

Further, regarding the arrangement of the convex lens 4, it is desirable that the position of the convex lens 4 is approximately halfway between the positions of the DOE 3 and the parallelizing lens 5. FIG. 5 shows the relationship between the distance D ₂ from the DOE 3 to the convex lens 4 and the distance D from the DOE 3 to the collimating lens 5 under the above conditions. It should be noted that the graph shown in FIG. 5 is derived using paraxial theory and does not consider any aberrations of the lens. In the graph of FIG. 5, the distance D ₂ from the DOE 3 to the convex lens 4 at the point where the distance from the DOE 3 to the collimating lens 5 becomes small, that is, the point where the illumination device 1 becomes the smallest, is 12.8 mm. The distance D up to 5 is derived as 25.6 mm. From this result, it is shown that the size of the illumination device 1 can be reduced most effectively by disposing the convex lens 4 at a substantially intermediate position between the DOE 3 and the parallelizing lens 5.

  In addition, as another effect obtained by inserting the convex lens 4, the fine shape of the DOE 3 can be relaxed, and the manufacturing difficulty level and manufacturing error can be reduced. As described above, when the pixel length p of the DOE 3 in FIG. 1 is 1.0 μm, the distance D ′ from the DOE 3 to the collimating lens 5 when the convex lens 4 is not provided is 28.9 mm. On the other hand, when the distance D between the DOE 3 and the collimating lens 5 is fixed to 28.9 mm and the convex lens 4 with a focal length f4 = 3 mm is arranged, the maximum emission angle θ1 emitted to the first-order diffraction region of the DOE 3 is 11. Once. From this, the pixel length p of DOE 3 can be derived as 1.38 μm. When the DOE 3 is manufactured using the same technique and processing machine, the longer the pixel length p, the smaller the influence of the manufacturing error, and the DOE 3 with high shape accuracy and high first-order diffraction efficiency can be manufactured. The light utilization efficiency can be improved. Further, since the pixel length p can be increased, the required processing accuracy in the manufacturing process can be lowered, and the manufacturing cost of the DOE 3 can be reduced.

Another embodiment in the present embodiment will be described with reference to FIG. FIG. 6 schematically shows a configuration in which a concave mirror (optical element) 8 is arranged at the position of the convex lens (optical element) 4 in FIG. Although the configuration up to DOE 3 is not different from the configuration in FIG. 1, a concave mirror 8 is arranged as a light collecting means. The concave mirror 8 uses an off-axis elliptical mirror and is arranged such that the second focal length Fb ₈ is smaller than the first focal length Fa ₈ . The light beam L2 emitted from the DOE 3 is emitted in the direction in which the optical axis is rotated by 90 ° by the concave mirror 8. The emitted light beam L5 is once condensed at the second focal point of the concave mirror 8, and then diffused again at the diffusion angle (half angle) _θL5 . As described above, since the second focal length Fb ₈ is smaller than the first focal length Fa _{8 of} the concave mirror 8, the exit angle θ _L5 from the concave mirror is larger than the incident angle θ _L2 to the concave mirror 8. Becomes larger. The light beam L5 reaches the illuminated surface 6 after becoming a parallel light beam L6 by the collimating lens 5.

It is conceivable that the optical system of the illumination device needs to be a folded optical system due to restrictions on the shape of the device. A small folded optical system can be realized by inserting a reflective flat plate at the condensing point Pf ₄ in FIG. On the other hand, if the configuration using the concave mirror 8 as shown in FIG. 6 is used, the condensing effect by the lens and the rotation effect of the optical axis can be realized by one element, so that the apparatus can be simplified and reduced in weight. Can be realized.

  The concave mirror used in the configuration of FIG. 6 is an off-axis elliptical mirror that rotates the 90 ° optical axis, but the rotation angle of the optical axis is not limited to this. As the concave mirror, a so-called deformable mirror that can modulate the mirror surface shape at a high speed in time may be used in addition to a commonly used aluminum vapor deposition mirror. By using a deformable mirror, it is possible to reduce speckle noise, which is a problem when using coherent light as illumination light. Speckle noise is a phenomenon in which, when light coherence is high, luminance spots occur in illumination light due to interference between different parts of the light path (partial light beams) in the light beam. For example, when a coherent light source is used as illumination light of a projector, there is a problem that display quality is greatly deteriorated due to speckle noise occurring in a projected image. By applying the deformable mirror described above to the concave mirror, luminance spots that are temporally different are generated by changing the wavefront of each partial light beam with time. By superimposing it over time, speckle noise can be reduced and illumination light can be made uniform.

(Example 2)
The aspect of Example 2 regarding the illuminating device of this invention is demonstrated using FIG. In addition, the same code | symbol is attached | subjected to the part same as Example 1, and description is abbreviate | omitted suitably about the overlapping content.
FIG. 7 is a schematic diagram illustrating a schematic configuration of the illumination device according to the second embodiment. In FIG. 7, the illumination device 11 includes a light source device 2, a DOE 3, a concave lens (optical element) 12, and a collimating lens 13, and illuminates the illuminated surface 6. Hereinafter, an outline of the illumination device 11 illustrated in FIG. 7 will be described.

In FIG. 7, the direction in which the light beam travels from the light source device 2 is defined as + z, the upward direction in the drawing is defined as + x, and the forward direction from the drawing is defined as + y. From the light source device 2, coherent light L <b> 11 is emitted, and the coherent light L <b> 11 enters the DOE 3. A light beam L12 shaped into a predetermined luminance distribution is emitted from the DOE 3 and is incident on the concave lens 12 at an incident angle θ _L12 . The concave lens 12 and emitted at large emission angle theta _L13 than theta _L12 L13 after passing through the collimating lens 13 is illuminated and becomes light beam L14 which is substantially parallel to the illuminated surface 6 of a predetermined size S The Focal length f13 of the collimating lens 13 can be expressed by the distance the light beam L13 to the principal point position of the collimating lens 13 from the focal point P _L13' the virtual light beam L13' that extends in the -z direction is focused.

  In the conventional configuration that does not include the concave lens 12, the light beam L12 emitted from the DOE 3 spreads as a light beam L12 ′ indicated by a broken line in FIG. 7 and is illuminated on the illuminated surface 6 ′. It is shown that the distance Db between the DOE 3 and the illuminated surface 6 is reduced by providing the concave lens 12 with respect to the distance Db ′ between the DOE 3 and the illuminated surface 6 ′. For this reason, the illumination device 11 can be reduced in size by including the concave lens 12.

In this embodiment, it is desirable to use a concave lens 12 having a smaller focal length f12 (not shown). The exit angle θ _L12 from the DOE 3 and the exit angle θ _L13 from the concave lens 12 in FIG. 7 are expressed as follows using the distance D ₁₂ from the DOE 3 to the concave lens 12 and the focal length f12 of the concave lens 12.
Tanθ _L12 / Tanθ _L13 = f ₁₂ / (D ₁₂ + f ₁₂ )
From the above relational expression, it can be seen that θ _L13 increases as the focal length f ₁₂ of the concave lens 12 decreases. The larger the exit angle θ _L13 from the concave lens 12, the smaller the distance from the concave lens 12 to the parallelizing lens 13, and the smaller the illumination device 11 can be made. For these reasons, by a smaller focal length f ₁₂ of the concave lens 12, it is possible to efficiently reduce the size of the lighting device 11.

  In the present embodiment, the concave lens 12 is preferably disposed at a substantially intermediate position between the DOE 3 and the parallelizing lens 13. By disposing the concave lens 12 at a substantially middle position between the DOE 3 and the collimating lens 13, the illumination device 11 can be more efficiently downsized.

The concave lens 12 used in this embodiment is a generally used spherical plano-concave lens. The spherical plano-concave lens is easy to process, and the configuration shown in this embodiment can be realized at low cost. The concave lens 12 may be any element that has a negative focal length and a larger output angle θ _L13 with respect to the incident angle θ _L12 . For example, the concave shape of the concave lens 12 may be aspherical. By making the surface shape of the concave lens an aspherical surface, it is possible to reduce the distortion of the lens and to efficiently illuminate the surface to be illuminated having a predetermined shape. For example, the concave lens 12 may be a diffractive lens represented by a Fresnel lens. The diffractive lens is characterized in that the element can be thinned, and the illumination device 11 can be further reduced in weight.

Another embodiment in the present embodiment will be described with reference to FIG. FIG. 8 schematically shows a configuration in which a convex mirror (optical element) 15 is arranged at the position of the concave lens 12 in FIG. The configuration up to DOE 3 is the same as the configuration in FIG. A convex mirror 15 that is an off-axis free-form surface mirror is arranged for the light beam _L2 emitted from the DOE 3 at the emission angle θ _L2 , and the emission angle θ _L15 of the light beam L15 emitted from the convex mirror 15 is made larger than the emission angle θ _L2 . Thereafter, the light beam L15 enters the collimating lens 16, and the parallel light beam L16 emitted from the collimating lens 16 reaches the illuminated surface 6.

  If it is necessary to use a folding optical system as shown in FIG. 8 due to the size limitation of the apparatus, for example, it may be achieved by arranging a reflecting plate between the concave lens 12 and the collimating lens 13 in FIG. Is possible. However, by adopting a configuration using a convex mirror as shown in FIG. 8, the effect of the concave lens and the reflecting plate can be realized by one element, so that the apparatus can be reduced in size and simplified.

(Example 3)
The aspect of Example 3 regarding the illuminating device of this invention is demonstrated using FIG. In addition, the same code | symbol is attached | subjected to the part same as Example 1 and 2, and description is abbreviate | omitted suitably about the overlapping content.
The present embodiment is different from the first embodiment (FIG. 1) in that the DOE and the convex lens are formed on the same substrate, and the other parts have the same configuration. FIG. 9 schematically shows the configuration of this embodiment. On the + z side of the light source device 2, a DOE 23 having a beam shaping function for shaping the coherent light L21 into a desired illumination shape is formed on the incident side, and a convex shape is formed on the output side, which is a convex shape. Are provided with a single substrate 22 provided with a convex lens (optical element) 24 provided respectively. The light beam L23 emitted from the substrate 22 is once condensed at the condensing point P _f24 and then diffused again to become a parallel light beam L24 by the parallelizing lens 25 and reaches the illuminated surface 6.

  By using the elements having the DOE function and the convex lens function on the same substrate as described above, there are advantages such as reduction in the number of parts of the device and the need for alignment adjustment, thereby realizing an inexpensive and small illumination device. It becomes possible.

  In order to produce the substrate 22 provided with the concave and convex shape of the DOE 23 and the convex shape of the convex lens 24 on both surfaces of the substrate, for example, double-sided integral molding by injection molding is exemplified. By using injection molding, a large number of replicas can be manufactured with high throughput, so that the element can be manufactured at low cost.

  In this embodiment, a substrate provided with a concave lens on the exit side of the substrate 22 may be used. By using an element having a DOE on the incident side and a concave lens on the exit side, the lighting device can be miniaturized for the same reason as described in the second embodiment.

Example 4
The mode of Example 4 regarding the illuminating device of this invention is demonstrated using FIG. In this embodiment, a mode when the lighting device described in Embodiments 1 to 3 is applied to a projector is shown. FIG. 10 shows a schematic diagram when the illumination device 11 according to the second embodiment of the present invention is applied to a projector.

  The projector 30 shown in FIG. 10 emits red coherent light and illuminates a predetermined illuminated surface 6R after luminance shaping, and predetermined illumination after emitting green coherent light and luminance shaping. An illumination device 11G for illuminating the surface 6G, an illumination device 11B for illuminating a predetermined illuminated surface 6B after emitting blue coherent light and shaping the luminance, and an illuminated surface 6R illuminated by each color illumination device , 6G, and 6B, and light modulated by each of the spatial light modulators 31R, 31G, and 31B and the spatial light modulators 31R, 31G, and 31B that modulate and transmit the light illuminated in each color according to image information, and transmit the light. A dichroic prism 32 for combining the light beams of the respective colors, and a projection optical system 3 for projecting the light beams generated by the dichroic prism 32 onto the screen 34. It is equipped with a door.

  The spatial light modulation elements 31R, 31G, and 31B have a configuration in which the incident side and the emission side are sandwiched by polarizing plates with respect to a liquid crystal panel that controls polarization by controlling the orientation direction by applying an electric field. Polarization is controlled by changing the amount of electric field applied by the TFT array arranged at each part of the liquid crystal panel, and the polarization state is changed by the polarizing plate on the incident side and the outgoing side, thereby modulating the luminance of each color light beam transmitted therethrough. Do. Hereinafter, the expression “light valve” is also used for the spatial light modulator.

  The dichroic prism 32 is formed by adhering four right-angle prisms deposited on the surface of a multilayer film. The dichroic prism 32 has characteristics that depend on the wavelength and the polarization of the transmittance and the reflectance, thereby allowing the red light beam and the green light beam. It is possible to synthesize a blue light beam. By enlarging the light beams of three colors of red, green, and blue with a projection lens and projecting them on the screen 34, a huge full-color image is displayed on the screen 34.

  As described in the second embodiment, the illumination devices 11R, 11G, and 11B are reduced in size by disposing the concave lens 12. By using the illumination devices 11R, 11G, and 11B of the present invention for the projector 30, the projector 30 can be reduced in size. In addition, although the illuminating device 11 shown in Example 2 is used as the illuminating devices 11R, 11G, and 11B in the present Example, about the illuminating devices 1, 7, 8, and 9 as described in Example 1, 2, or 3. Can also be applied.

In this embodiment, illumination devices 11R, 11G, and 11B for generating and illuminating each color of red, green, and blue are arranged, and each spatial light modulation device 31R is used to modulate the luminous flux of each illuminated color. 31G and 31B are arranged, but the wavelength (color) and the number of light sources used in the illumination device are not limited thereto.
Regarding the configuration of the projector, a plurality of coherent light sources that generate a plurality of wavelengths are arranged in an array, and the illumination device is composed of a single substrate DOE, a concave lens, and a collimating lens. May be of a so-called light valve single plate type constituted by a single illumination device, a single spatial light modulation device, and a projection optical system by a so-called time-division operation in which the lights are turned on at different times.

  As for the spatial light modulator, in this embodiment, the configuration using the transmissive liquid crystal is given as an example, but the application of the present invention is not limited to this. For example, the present invention can also be applied to a projector using a reflective liquid crystal (LCOS) or DMD (Digital Micromirror Device).

(Example 5)
The aspect of Example 5 regarding the illuminating device of this invention is demonstrated using FIGS. This embodiment is a so-called spatial color that can modulate light beams of a plurality of colors with a single spatial light modulator (liquid crystal light valve) by distributing illumination light of a plurality of colors to different pixels of the spatial light modulator. This is about the separation type projector.

  FIG. 11 is a schematic diagram of a light valve single-plate full-color projector using a spatial color separation system shown in the fifth embodiment. The projector 40 according to the present embodiment generates a red light beam, a green light beam, and a blue light beam, and uniformly illuminates each color parallel light beam at a different incident angle on the illumination surface 46 having a predetermined shape; A spatial light modulator 47 for performing luminance modulation on each color parallel light beam illuminated on the surface to be illuminated 46 according to the video signal, and a light beam emitted from the spatial light modulator 47 on the surface to be illuminated of the screen 49 A projection optical system 48 for enlarging projection.

The spatial light modulator 47 includes a liquid crystal panel provided with a microlens array (MLA) 50 (described later) on the incident side, an incident side polarizing plate, and an outgoing side polarizing plate. The spatial color separation method will be described below. FIG. 12 schematically shows a liquid crystal panel including the MLA 50.
And is incident at an angle difference theta _L50 respectively red beam L50R, green beam L50G and blue light beam 50B on the liquid crystal panel. The red light beam L50R is condensed (L51R) on the pixel 52R of the liquid crystal layer 52 sandwiched between the functional films 53a and 53b formed of the ITO film and the alignment film by the MLA 50, and the green light beam L50G is focused on the liquid crystal layer 52 by the MLA 50. The light is condensed on the pixel 52G (L51G), and the blue light beam L50B is condensed on the pixel 52B of the liquid crystal layer 52 by the MLA 50 (L51B). The angle difference θ _L50 between the light beams of the respective colors can be expressed as follows using the optical distance D ₅₀ between the MLA ₅₀ and the liquid crystal layer 52 and the inter-pixel distance p ₅₂ .
θ _L50 = Tan ⁻¹ (p ₅₂ / D ₅₀ )
With such a configuration, each color beam can be guided to different pixels, and a plurality of colors can be controlled without using a color filter.

  The lighting device 41 will be described. The illumination device 41 includes a light source device 42 including a red laser light source 42R that emits red coherent light, a green laser light source 42G that emits green coherent light, and a blue laser light source 42B that emits blue coherent light, and each color coherent. DOE 43 having red DOE 43R, green DOE 43G and blue DOE 43B designed for each color so as to shape the luminous flux into a rectangular luminance distribution, concave lens 44 for increasing the spread angle of each color luminous flux, and each color A collimating lens 45 for converting the light beam into a substantially parallel light beam.

Here, the function of the concave lens 44 will be described. In FIG. 13, the schematic of the illuminating device 41 is shown. As shown in the second embodiment, by arranging the concave lens 44, the exit angle of the diffused light beam from the DOE 43G can be increased, thereby obtaining the effect of reducing the distance between the DOE 43 and the parallelizing lens 45, The illumination device 41 can be reduced in size. On the other hand, another effect of the concave lens 44 is that the restriction due to the size of the light source device 42 can be suppressed. As described above, it is necessary to illuminate each at an chief ray Lc44R, angle of angle difference theta _L44 principal rays Lc44B principal ray Lc44G and blue beam of green light beam of the red light beam with respect to the surface to be illuminated 46. The angle difference θ _L44 is equal to the angle difference θ _{L50 in} FIG. Here, as shown in FIG. 13, the inter-beam distance between the principal ray L42G of the green luminous flux and the principal ray L42B of the blue luminous flux is defined as a beam interval D42. Furthermore, the principal rays L43B ′ and L42B ′ of the blue light beam when the concave lens 44 is not disposed are indicated by broken lines. At this time, the positions of the principal rays L43G and L42G of the green light flux and the green DOE 43G do not change. If the inter-beam distance between the principal ray L42G ′ of the green light beam and the principal ray L42B ′ of the blue light beam when the concave lens 44 is not arranged is defined as a beam interval D42 ′, the beam interval D42 and the concave lens 44 when the concave lens 44 is arranged are arranged. The relational expression of the beam interval D42 ′ when not can be expressed as follows.
D42> D42 '
For this reason, it is possible to widen the light source interval by arranging the concave lens 44. By widening the distance between the light sources, restrictions on the size of the light source to be used can be suppressed, the difficulty of light source development can be reduced, and the cost can be suppressed. Further, since the interval between the light sources can be widened, it is easy to dissipate heat generated from the light sources, and the effect that the oscillation luminance of the light sources can be increased accordingly. From these effects, an inexpensive and high-brightness projector can be realized.
Further, when the concave lens 44 is not disposed when the light source interval D ₄₂ must be set due to the light source size restriction, the distance between the DOE 43 and the parallelizing lens 45 must be increased by the distance D _{43 in} order to maintain the angle difference θ _L44. I will have to. By disposing the concave lens 44, restrictions on the size of the optical system due to the light source size can be suppressed, and the projector can be miniaturized.

  As the element used as the spatial light modulation element, a transmissive liquid crystal panel in which MLA is disposed on the incident side is used, but the present invention can also be applied to other types of light valves such as a reflective liquid crystal panel (LCOS). In general, a polarizing plate is often arranged on the incident side and the outgoing side, but the position of the incident side polarizing plate is not limited to this. In addition, when a light source having a polarization property is used, it is possible not to use the incident side polarizing plate. As for the pixel structure of the liquid crystal panel, a configuration in which red, green, and blue pixels are arranged in the horizontal direction is taken as an example, but the arrangement method is not limited to this. For example, a square pixel structure panel may be used to cause red, yellow, green, and blue light beams to enter four pixels. Further, two pixels may be used for one color such as red, green, green, and blue.

  As for the projector according to the present embodiment, an example is given regarding a projector that is used alone. However, the projector can also be applied to an embedded projector incorporated in another device. For example, a small built-in projector that displays a screen by a projection method by incorporating this configuration in a mobile phone can be cited as an application example. On the other hand, it can also be used for applications such as a head-up display (HUD).

DESCRIPTION OF SYMBOLS 1 Illumination device, 2 light source device, 3 DOE, 4 convex lens, 5 collimating lens, 6 surface to be illuminated, L1 coherent light, L2, L3, L4, L3 ′ luminous flux, P _f4 condensing point, θ _L2 , θ _L3 emission square, f5 the focal _{length, D, D', D 2,} D 3 distance, S size.

Claims (4)

A light source device that emits coherent light; a diffractive optical element that shapes the coherent light into a light beam having a predetermined luminance distribution; and a collimating lens that converts the light beam emitted from the diffractive optical element into a parallel light beam. A lighting device,
Between the collimating lens and the diffractive optical element comprises a concave surface mirror for increasing the divergence angle of the light beam emitted from the diffractive optical element,
The illumination apparatus according to claim 1, wherein the concave mirror is an off-axis elliptical mirror whose focal length on the exit side is shorter than the focal length on the incident side . The illumination apparatus according to claim 1, wherein the curved mirror is disposed at a substantially middle position between the diffractive optical element and the collimating lens. Projector comprises an illumination device according to claim 1 or 2. A projector,
A plurality of light source devices each emitting coherent light of a predetermined color;
A diffractive optical element that shapes the coherent light into a light beam having a predetermined luminance distribution;
A collimating lens for converting the light beam emitted from the diffractive optical element into a parallel light beam;
A spatial light modulation element that has pixels and modulates a light beam emitted from the collimating lens according to image information;
A projection lens that projects a light beam emitted from the spatial light modulation element onto an irradiated surface;
Provided between the collimating lens and the spatial light modulation element, the light beam of the predetermined color incident on the spatial light modulation element is set to a different incident angle for each color, and the light beam of the predetermined color is set for each color. Pixel distribution means for condensing and incident on different pixels;
Wherein provided between the collimating lens and the diffractive optical element, and a concave surface mirror for controlling the ray angle of the predetermined color of the light beam,
The concave mirror is an off-axis elliptical mirror in which the focal length on the output side is shorter than the focal length on the incident side .

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