Light source device and projection device

Abstract

To provide a light source device and a projection device that can be constructed in compact size, and with which the efficiency of light utilization is improved.SOLUTION: A projection device 10 equipped with a light source device 60 comprises: light-emitting devices 70, 70A including a plurality of laser diodes 71 and provided to be able to emit lights LB, LBA with which the polarization directions of the laser diodes 71 are aligned; a diffraction optical element 141 to which the lights LB, LBA from the light-emitting devices 70, 70A are entered; a polarization beam splitter 142 for reflecting or passing through lights L1, L1A from the diffraction optical element 141 in accordance with the polarization directions of the lights LB, LBA; a reflection mirror 144 for reflecting the light L2 reflected or the light L1A passed through by the polarization beam splitter 142 toward the polarization beam splitter 142; and a λ / 4 plate 143 provided in an optical path between the polarization beam splitter 142 and the reflection mirror 144.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a light source device and a projection device. [Background technology]

[0002] Conventionally, projection devices have been disclosed that generate image light by shaping light from a light source such as a laser diode using a diffractive optical element (DOE) and irradiating the light onto a display element. For example, Patent Document 1 discloses a projection device that includes a first laser light source that emits light in a red wavelength band, a second laser light source that emits light in a green wavelength band, and a third laser light source that emits light in a blue wavelength band, and in which light from each laser light source is irradiated onto a display element via a polarization rotation element, a polarization separation element, and a diffractive optical element. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-121842 Summary of the Invention [Problem to be solved by the invention]

[0004] There is a demand for miniaturization of projection devices including light source devices, and therefore, there is a demand for shortening the distance between each light source and optical element and the distance between optical elements. In the above-mentioned conventional projection devices, when light from a light source is irradiated onto a display element in a straight line, shortening the distance between the light source and the display element may increase the light ray angle of the light source. However, display elements have a predetermined range of light ray angles determined by their specifications, and therefore, a large light ray angle may generate light that deviates from the specification range of the display element. As a result, some light from the light source may not be used to generate an image, which may reduce the light utilization efficiency.

[0005] In view of the above, an object of the present invention is to provide a light source device and a projection device that can be made compact and that have improved light utilization efficiency. [Means for solving the problem]

[0006] The light source device of the present invention includes a light output device that has a plurality of light sources and is capable of outputting light with the polarization direction of each of the light sources aligned; a diffractive optical element onto which the light from the light output device is incident; a polarizing beam splitter that transmits or reflects the light from the diffractive optical element depending on the polarization direction; a reflection mirror that reflects the light transmitted or reflected by the polarizing beam splitter toward the polarizing beam splitter; and a λ / 4 plate that is provided on the optical path between the polarizing beam splitter and the reflection mirror.

[0007] The projection device of the present invention comprises the above-mentioned light source device, a display element that generates image light, a projection optical system that projects the image light emitted from the display element onto a projection target, and a control unit that controls the light source device and the display element. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a light source device and a projection device that can be configured to be compact and that have improved light utilization efficiency. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 2 is a diagram showing functional circuit blocks of the projection device according to the embodiment of the present invention. [Figure 2] FIG. 1 is a schematic plan view showing the internal structure of a projection device according to an embodiment of the present invention. [Figure 3] 2 is an enlarged schematic plan view of a main part of a light source device of the projection device according to the embodiment of the present invention. FIG. [Figure 4] 1A and 1B are diagrams for explaining a diffractive optical element in a light source device of a projection device according to an embodiment of the present invention, in which (a) is a schematic front view seen from the incident surface of laser light, and (b) is a schematic plan view seen from above. [Figure 5] 10 is an enlarged schematic plan view of a main portion showing a modified example of a light source device in a projection device according to an embodiment of the present invention. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a functional circuit block diagram of a projection device 10. The projection device control unit is composed of a CPU including an image conversion unit 23 and a control unit 38, a front-end unit including an input / output interface 22, a display encoder 24, and a display driver 26. Image signals of various standards input from an input / output connector unit 21 are converted by the image conversion unit 23 via the input / output interface 22 and system bus SB to unify them into image signals of a predetermined format suitable for display, and then output to the display encoder 24.

[0011] Furthermore, the display encoder 24 expands and stores the input image signal in the video RAM 25, generates a video signal from the stored contents of the video RAM 25, and outputs the video signal to the display driver .

[0012] The display driver 26 drives a display element 50, such as a DMD, which is a spatial light modulator (SOM), at an appropriate frame rate in response to the image signal output from the display encoder 24. The projection device 10 forms an optical image with the light reflected from the display element 50 by irradiating the light beam emitted from the light source device 60 onto the display element 50 via a light guide optical system 170 (see FIG. 2), and projects and displays the image on a projection target such as a screen (not shown) via a projection optical system 220 (see FIG. 2). A movable lens group 235 of the projection optical system 220 can perform zoom adjustment and focus adjustment by driving a lens motor 45.

[0013] Furthermore, the image compression / expansion unit 31 performs a recording process in which the luminance signal and color difference signal of the image signal are compressed by processes such as ADCT and Huffman coding, and the data is sequentially written to a memory card 32, which is a removable recording medium. Furthermore, the image compression / expansion unit 31 reads image data recorded on the memory card 32 in the playback mode, expands each piece of image data constituting a series of moving images on a frame-by-frame basis, and outputs the expanded data to the display encoder 24 via the image conversion unit 23. Thus, the image compression / expansion unit 31 can output moving images, etc., based on the image data stored in the memory card 32.

[0014] The control unit 38 controls the operation of each circuit in the projection device 10, and is composed of a CPU, a ROM that permanently stores operation programs such as various settings, and a RAM used as a work memory.

[0015] The key / indicator section 37 is composed of main keys and indicators provided on the housing. Operation signals from the key / indicator section 37 are sent directly to the control section 38. In addition, key operation signals from the remote controller are received by the Ir receiving section 35, demodulated into code signals by the Ir processing section 36, and output to the control section 38.

[0016] The control unit 38 is connected to an audio processing unit 47 via a system bus SB. The audio processing unit 47 includes a sound source circuit such as a PCM sound source, and converts audio data into analog data in the projection mode and playback mode, driving a speaker 48 to emit amplified sound.

[0017] The control unit 38 controls a light source control device including a light source control circuit 41. The light source control device including the light source control circuit 41 controls the light source device 60 in a time-division manner so that light in a predetermined wavelength band required for image generation is emitted from the light source device 60.

[0018] Furthermore, the control unit 38 causes the cooling fan drive control circuit 43 to detect temperatures using a plurality of temperature sensors provided in the light source device 60, etc., and controls the rotation speed of the cooling fan 261 based on the results of this temperature detection. The control unit 38 also controls the cooling fan drive control circuit 43 to continue rotating the cooling fan 261 using a timer or the like even after the power to the projection device 10 main body is turned off, or to turn off the power to the projection device 10 main body depending on the results of temperature detection by the temperature sensors.

[0019] Next, the internal structure of the projection device 10 will be described. Fig. 2 is a schematic plan view showing the internal structure of the projection device 10. Here, the housing of the projection device 10 is formed in a substantially box shape and includes an upper panel and a lower panel (not shown), a front panel 12, a rear panel 13, a right panel 14, and a left panel 15. The projection device 10 also has a projection opening 12a on the front side. In the following description, left and right of the projection device 10 refer to the left and right directions relative to the projection direction from the projection opening 12a, and front and rear refer to the direction toward the projection target of the projection device 10 and the front and rear directions relative to the traveling direction of the light beam.

[0020] The projection device 10 includes a control circuit board 242 near the left panel 15. This control circuit board 242 includes a power circuit block, a light source control block, and the like. The projection device 10 also includes a light source device 60 located approximately in the center of the projection device 10. A power connector 57, a heat sink 130, a cooling fan 261, and the like are located between the light source device 60 and the right panel 14. A display element 50 is also provided on the left side of the light source device 60. The display element 50 is connected to a heat sink 190 provided on the left side of the rear panel 13 by a heat pipe (not shown).

[0021] The light source device 60 has a light emitting device 70 arranged on the rear panel 13 side in approximately the center in the left-right direction of the projection device 10. The light emitting device 70 is equipped with a plurality of laser diodes 71 as light sources configured to be able to emit red wavelength band light, green wavelength band light, and blue wavelength band light. The plurality of laser diodes 71 may be a multi-chip package structure (MCP (Multi Chip Package)) including a red laser diode 71R that emits red wavelength band light, a green laser diode 71G that emits green wavelength band light, and a blue laser diode 71B that emits blue wavelength band light.

[0022] The light output device 70 is connected to a heat sink 130 via a heat pipe (not shown) so as to be cooled. The light source device 60 is provided with a light source optical system 140 that guides blue, red, and green wavelength band light. The light source device 60 also is provided with a light guide optical system 170 that guides light from the light source optical system 140 to the display element 50 and guides image light generated by the display element 50 to the projection optical system 220.

[0023] The light emitting device 70 emits light of each color wavelength band from the rear panel 13 toward the front panel 12, tilted slightly to the right. The light emitting device 70 is also integrally provided with a collimator lens (not shown) corresponding to each laser diode 71. The light emitting device 70 is also configured to emit light with the same polarization direction as the light emitted from each laser diode 71. In this embodiment, the light emitted from the light emitting device 70 is s-polarized laser light. Therefore, for example, if the red laser diode 71R, the green laser diode 71G, and the blue laser diode 71B are configured and arranged to emit s-polarized light, a λ / 2 plate 72, as indicated by the two-dot chain line, can be disposed on the output side of the light-emitting point of the green laser diode 71G, which emits p-polarized light. This aligns the polarization direction of the light of each color wavelength band emitted from the light emitting device 70 to s-polarized light.

[0024] As shown in FIGS. 2 and 3 , the light source optical system 140 includes a diffractive optical element 141, a polarizing beam splitter 142, a λ / 4 plate 143, and a reflecting mirror 144. The diffractive optical element 141 is disposed on the output side of the light output device 70. The diffractive optical element 141 can shape the laser light from the light output device 70 into a rectangular shape. Specifically, by finely fabricating the surface structure of the diffractive optical element 141, the light emitted from the diffractive optical element 141 can be shaped into a rectangular shape. As shown in FIG. 4 , the diffractive optical element 141 has multiple diffractive optical element regions 141R, 141G, and 141B, each having a diffraction characteristic corresponding to the laser diode 71. The diffractive optical element region 141R has a diffraction characteristic corresponding to the red laser diode 71R. Similarly, the diffractive optical element region 141G has a diffraction characteristic corresponding to the green laser diode 71G, and the diffractive optical element region 141B has a diffraction characteristic corresponding to the blue laser diode 71B.

[0025] The polarizing beam splitter 142 is disposed on the output side of the diffractive optical element 141. The polarizing beam splitter 142 reflects s-polarized laser light and transmits p-polarized laser light. The λ / 4 plate 143 is disposed on the right side of the polarizing beam splitter 142 with respect to the output direction of the light L1 from the diffractive optical element 141. The reflecting mirror 144 is disposed on the right side of the λ / 4 plate 143 (the right side with respect to the output direction of the light L1). A light-guiding optical system 170 is provided on the left side of the polarizing beam splitter 142 (the left side with respect to the output direction of the light L1). The light-guiding optical system 170 has an RTIR prism 171. The RTIR prism 171 is disposed on the left side of the polarizing beam splitter 142, in front of the display element 50. The RTIR prism 171 is disposed in such a position that a reflection / transmission surface 171a, which reflects or transmits light depending on the incident angle of the incident light, faces the polarizing beam splitter 142 side.

[0026] The projection optical system 220 has an RTIR prism 171, and a movable lens group 235 and a fixed lens group 225 housed in a lens barrel 221. Image light generated by the display element 50 and emitted via the RTIR prism 171 is emitted as projection light from the projection opening 12a via the movable lens group 235 and the fixed lens group 225 provided in the lens barrel 221. The movable lens group 235 can be moved manually or automatically to enable zoom adjustment and focus adjustment.

[0027] By configuring the projection device 10 in this manner, light emitted from the light emitting device 70 is incident on the display element 50 via the light guiding optical system 170. Then, the DMD, which is the display element 50 of the projection device 10, displays light of each color in a time-division manner according to data, thereby projecting a color image onto a screen.

[0028] 3, the light LB of each color wavelength band, which is the laser light emitted from the light emitting device 70, has its polarization direction aligned to s-polarized light, as described above. The light LB enters the diffractive optical element 141, is shaped into a rectangular shape, and is emitted toward the polarizing beam splitter 142 as shown by light L1. The polarizing beam splitter 142 reflects the s-polarized light L1 toward the reflecting mirror 144 as shown by light L2.

[0029] Here, a λ / 4 plate 143 is provided on the optical path between the polarizing beam splitter 142 and the reflecting mirror 144. Therefore, the light L2, which has been reflected by the polarizing beam splitter 142 and has its polarization direction aligned with s-polarized light, passes through the λ / 4 plate 143 and is converted into circularly polarized light, enters and is reflected by the reflecting mirror 144, passes through the λ / 4 plate 143 again and is converted into p-polarized light, and is emitted from the λ / 4 plate 143.

[0030] Light L3 emitted from the λ / 4 plate 143 passes through the polarizing beam splitter 142. Light L3 is irradiated onto the image forming surface of the display element 50 via the RTIR prism 171. Image light L4 generated by the display element 50 is incident on the lens barrel 221 of the projection optical system 220 by the RTIR prism 171 and projected as projection light onto a projection target such as a screen from the projection opening 12a. The RTIR prism 171 is positioned so that light L3 is incident on the reflective / transmissive surface 171a at an angle of incidence smaller than the angle at which total reflection occurs, and image light L4 is incident on the reflective / transmissive surface 171a at an angle of incidence at which total reflection occurs.

[0031] In this way, in this embodiment, the optical path from the light emitting device 70 to the image forming surface of the display element 50 can be made relatively long compared to a configuration in which light shaped by the diffractive optical element 141 is directly irradiated onto the image forming surface of the display element 50 via the RTIR prism 171, so that the light source light can be emitted from the light emitting device 70 at an appropriate light ray angle. Then, the light source device 60 emits light L3 toward the display element 50 on the optical path between the light emitting device 70 and the diffractive optical element 141 (on the optical path of light LB) or on the optical path of the lights L1 to L3 emitted from the diffractive optical element 141 without passing through a lens for collecting the lights L1 to L3.

[0032] 4(b), for example, light L71 emitted from the laser diode 71 of the light emitting device 70 (light L71 emitted from the green laser diode 71G in the example of FIG. 4(b)) is converted into rectangular light L141 by the diffractive optical element region of the diffractive optical element 141 (diffractive optical element region 141G in the example of FIG. 4(b)). However, in the diffractive optical element region 141G, light L141m that could not be used for the rectangularly shaped light L141 may be emitted from the diffractive optical element 141 as zero-order light (i.e., unshaped light that is the same as light L71 before entering the diffractive optical element region 141G).

[0033] However, according to an embodiment of the present invention, as shown in Fig. 3, the optical path from the diffractive optical element 141 to the display element 50 can be lengthened, thereby increasing the degree of freedom in arranging the optical elements (light output device 70, diffractive optical element 141, polarizing beam splitter 142, and reflecting mirror 144). Therefore, by appropriately adjusting the arrangement of the optical elements (light output device 70, diffractive optical element 141, polarizing beam splitter 142, and reflecting mirror 144), it is possible to provide an escape optical path L141mk that allows stray light to escape outside the effective area of ​​the display element 50 somewhere in the optical path from the diffractive optical element 141 to the display element 50. In other words, the light output device 70, diffractive optical element 141, polarizing beam splitter 142, and reflecting mirror 144 are arranged to allow stray light (zero-order light) emitted from the diffractive optical element 141 to escape.

[0034] Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments and can be implemented with various modifications. For example, instead of the light output device 70 that aligns the polarization direction of the output light to s-polarized light, a light output device 70A that can output light LBA that aligns the polarization direction to p-polarized light can be used, as shown in the modified example of FIG. 5. In this case, the λ / 4 plate 143 and the reflecting mirror 144 are positioned opposite the light output device 70 with the polarizing beam splitter 142 between them.

[0035] The p-polarized light LBA from the light output device 70A is diffracted by the diffractive optical element 141 to become rectangularly shaped light L1A. The light L1A passes through the polarizing beam splitter 142 and is reflected by the reflecting mirror 144 via the λ / 4 plate 143. The light reflected by the reflecting mirror 144 passes through the λ / 4 plate 143 again to be converted into s-polarized light L2A. The light L2A is reflected by the polarizing beam splitter 142 toward the display element 50. In this way, the polarizing beam splitter 142 transmits or reflects the light from the diffractive optical element 141 depending on the polarization direction. The polarizing beam splitter 142 can be configured to reflect or transmit the light from the diffractive optical element 141 via the λ / 4 plate 143 toward the reflecting mirror 144, and to transmit or reflect the light from the reflecting mirror 144 that enters via the λ / 4 plate 143.

[0036] In addition, in this embodiment, the light emitting devices 70 and 70A have a multi-chip package structure, but other configurations are also possible, such as a configuration including a laser light source device having a holder that holds multiple laser diodes in a row and column direction and collimator lenses provided corresponding to each laser diode. In other words, the light emitting devices 70 and 70A may be configured to emit laser light with a uniform polarization direction.

[0037] According to the above embodiment, the light source device 60 includes light emitting devices 70, 70A that are provided with laser diodes 71 as multiple light sources and are capable of emitting light LB, LBA with the polarization directions of the laser diodes 71 aligned, a diffractive optical element 141 onto which the light LB, LBA from the light emitting devices 70, 70A is incident, a polarizing beam splitter 142 that transmits or reflects light L1, L1A from the diffractive optical element 141 depending on the polarization direction of the light LB, LBA, a reflecting mirror 144 that reflects light L2 reflected by the polarizing beam splitter 142 or the transmitted light L1A toward the polarizing beam splitter 142, and a λ / 4 plate 143 that is provided on the optical path between the polarizing beam splitter 142 and the reflecting mirror 144.

[0038] As a result, the light from the laser diode 71 can be shaped by the diffractive optical element 141 to form a long optical path even in a small size, and the light emitted from the diffractive optical element 141 can have a relatively small ray angle. Therefore, the device can be configured to be small, and the ray angle can be set within the range of the specifications of the display element 50, thereby reducing unused light and providing a light source device 60 with improved light utilization efficiency. Furthermore, since unused light is reduced, it is possible to reduce the occurrence of a portion of light becoming insufficient, and color unevenness in the projected image can also be reduced.

[0039] If light shaped by the diffractive optical element 141 were to be directly irradiated onto the image forming surface of the display element 50 via the RTIR prism 171, the light emitted from the diffractive optical element 141 would need to have a large ray angle to match the image forming surface of the display element 50, or the distance from the diffractive optical element 141 to the display element 50 would need to be long. Since the display element 50 generally has a set range of ray angles to be irradiated, the position of the diffractive optical element 141 would be determined based on that ray angle range, which could result in an increase in the size of the device. Furthermore, if light with a large ray angle is irradiated onto the display element 50, image light that is not used in the subsequent projection optical system 220 may be generated, reducing the light utilization efficiency. However, according to the present invention, the optical path can be lengthened, thereby enabling the device to be made more compact while still generating high-quality image light by setting an appropriate ray angle.

[0040] Furthermore, as described above, in a configuration in which light is irradiated directly from the diffractive optical element 141 to the display element 50 via the RTIR prism 171, the zero-order light (light 141m) described above becomes stray light and is irradiated within the effective area of ​​the image forming surface of the display element 50. As a result, stray light that should not be used as image light overlaps on the display element 50 and the screen onto which the projection light is projected, resulting in a degradation of image quality. However, according to the present invention, a relatively long optical path can be achieved, which increases the degree of freedom in the arrangement of the optical elements (light emitting device 70, diffractive optical element 141, polarizing beam splitter 142, and reflecting mirror 144). This allows stray light to escape along one of the optical paths, thereby reducing the degradation of image quality.

[0041] Furthermore, the light emitting device 70, the diffractive optical element 141, the polarizing beam splitter 142, and the reflecting mirror 144 are arranged so as to allow stray light (zeroth-order light) emitted via the diffractive optical element 141 to escape. This allows the stray light (zeroth-order light) to be removed from the effective area of ​​the display element 50.

[0042] Furthermore, the light emitting device 70, 70A includes a λ / 2 plate 72 provided corresponding to at least one laser diode 71. This makes it possible to emit light with the same polarization direction even if the laser diodes 71 are arranged so that the polarization directions are different.

[0043] Furthermore, the diffractive optical element 141 has a plurality of diffractive optical element regions 141R, 141G, and 141B corresponding to the laser diode 71. This allows the diffractive optical element 141 to have optimal diffraction characteristics for each color wavelength band light, for example.

[0044] The light emitting devices 70 and 70A also have a multi-chip package including a red laser diode 71R that emits light in the red wavelength band, a green laser diode 71G that emits light in the green wavelength band, and a blue laser diode 71B that emits light in the blue wavelength band, thereby enabling the light emitting devices 70 and 70A to be compact while being equipped with three color light sources.

[0045] Furthermore, the polarizing beam splitter 142 reflects the light from the diffractive optical element 141 toward the reflecting mirror 144 via the λ / 4 plate, and transmits the light from the reflecting mirror 144 that is incident via the λ / 4 plate. This reduces the space required in the optical axis direction of the projection optical system 220, allowing for a layout design that makes it easy to avoid interference with other devices.

[0046] The projection device 10 also includes a display element 50 that generates image light, a projection optical system 220 that projects the image light emitted from the display element 50 onto a projection target such as a screen, and a control unit that controls the light source device 60 and the display element 50. This allows the device to be made compact, and also provides a projection device 10 that reduces the impact on the image light.

[0047] The projection device 10 may also be provided with an escape optical path L141mk that allows stray light emitted through the diffractive optical element 141 to escape outside the effective area of ​​the display element 50. This reduces glare from stray light, enabling clear image light to be projected.

[0048] Furthermore, the light source device 60 emits light L3 toward the display element 50 without passing through a lens for converging the light L1 to L3 on the optical path between the light emitting device 70 and the diffractive optical element 141 or on the optical path of the light L1 to L3 emitted from the diffractive optical element 141. Conventionally, for highly directional light such as laser light, a microlens array is used to perform beam shaping, so a microlens array and a lens for converging the light on the microlens array (for example, a concave lens for expanding the light and a convex lens for converting the expanded light into parallel light) are separately provided. In the present invention, since the beam is shaped by the diffractive optical element 141, it is possible to eliminate the conventionally used microlens array and the lens for converging the light on the microlens array, and it is possible to provide a more compact projection device 10.

[0049] The above-described embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments may be embodied in various other forms, and various omissions, substitutions, and modifications may be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0050] 10...Projection device 60...Light source device 70, 70A...Light output device 141...Diffractive optical element 142...Polarizing beam splitter 143...λ / 4 plate 144...Reflecting mirror

Claims

1. a light emitting device including a plurality of light sources, the light emitting device being capable of emitting light beams with the polarization directions of the light sources aligned; a diffractive optical element onto which the light from the light output device is incident; a polarizing beam splitter that transmits or reflects the light from the diffractive optical element according to the polarization direction; a reflecting mirror that reflects the light transmitted or reflected by the polarizing beam splitter toward the polarizing beam splitter; a λ / 4 plate provided on an optical path between the polarizing beam splitter and the reflecting mirror; A light source device having the above structure.

2. The light source device according to claim 1 , wherein the light output device, the diffractive optical element, the polarizing beam splitter, and the reflecting mirror are arranged so as to allow stray light output through the diffractive optical element to escape.

3. The light source device according to claim 1 , wherein the light output device includes a λ / 2 plate provided corresponding to at least one of the light sources.

4. The light source device according to claim 1 , wherein the diffractive optical element has a plurality of diffractive optical element regions corresponding to the light sources.

5. 2. The light source device according to claim 1, wherein the light emitting device has a multi-chip package including a red laser diode that emits light in a red wavelength band, a green laser diode that emits light in a green wavelength band, and a blue laser diode that emits light in a blue wavelength band.

6. 2. The light source device according to claim 1, wherein the polarizing beam splitter reflects the light from the diffractive optical element toward the reflecting mirror via the λ / 4 plate and transmits the light from the reflecting mirror that is incident via the λ / 4 plate.

7. A light source device according to any one of claims 1 to 6, a display element that generates image light; a projection optical system that projects the image light emitted from the display element onto a projection target; a control unit that controls the light source device and the display element.

8. 8. The projection device according to claim 7, further comprising an escape optical path for escaping stray light emitted through said diffractive optical element to outside the effective area of ​​said display element.

9. 8. The projection device according to claim 7, wherein the light source device emits the light toward the display element without passing through a lens for concentrating the light on the optical path between the light emitting device and the diffractive optical element or on the optical path of the light emitted from the diffractive optical element.

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