Lighting device

Abstract

This lighting device comprises: a light emitting unit that emits light; a phase modulation unit that performs spatial light phase modulation on incident light from the light emitting unit; a projection lens that enlarges and projects a reproduced image formed by the spatial light phase modulation by the phase modulation unit; a reformation optical system that reforms the reproduced image as a Fourier transformed image on a branch optical path branched off from a projection optical path which guides the reproduced image to the projection lens; a light receiving unit that is disposed such that a light receiving surface thereof coincides with a reproduced image reformation surface which is the surface on which the Fourier transformed image is formed; and an abnormality detection unit that detects an abnormality related to the light intensity distribution of an exit pupil of the projection lens on the basis of a light receiving signal by the light receiving unit.

Description

lighting equipment

[0001] The present technology relates to an illumination device, and more particularly to an illumination device that enlarges and projects a reproduced image generated by performing spatial light phase modulation on incident light from a light-emitting unit using a projection lens.

[0002] A technology is known that uses spatial light phase modulation to generate an image (reconstructed image) with a desired light intensity distribution on a predetermined imaging plane. A liquid crystal panel, for example, is used as a phase modulator for performing spatial light phase modulation. Changing the driving state of a pixel in the phase modulator (e.g., the orientation state of liquid crystal molecules) changes the amount of phase modulation (phase delay) for incident light at the pixel. Changing the driving state of the pixel changes the diffraction angle of the light incident on the pixel. Therefore, in a phase modulator, by setting the amount of phase modulation for each pixel, it is possible to set the exit angle of the emitted light, i.e., the amount of light bending, for each pixel. Setting the amount of light bending for each pixel in this way makes it possible to concentrate light in certain areas on the imaging plane and sparse light in other areas, thereby forming a desired light intensity distribution on the imaging plane. In other words, it is possible to generate a reconstructed image with a desired light intensity distribution.

[0003] Spatial light intensity modulation can also be used as a spatial light modulation for generating a reconstructed image. In spatial light intensity modulation, a reconstructed image having a desired light intensity distribution is generated using an intensity modulator configured to be able to change the transmittance and reflectance of incident light for each pixel. In contrast to generating a reconstructed image using such spatial light intensity modulation, generating a reconstructed image using the above-mentioned spatial light phase modulation has the advantage of improving the utilization efficiency of the incident light because it is no longer necessary to absorb or reflect a portion of the incident light to generate a reconstructed image with a desired light intensity distribution.

[0004] Illumination devices that utilize the image reconstruction technology based on spatial light phase modulation as described above are known. For example, as described in Patent Document 1 below, an illumination device that projects a reconstructed image formed by spatial light phase modulation is known.

[0005] International Publication No. 2018 / 211878

[0006] In the above-mentioned lighting device, when a person looks into the projection lens, an image of the exit pupil is formed on the retina, and if an abnormality occurs in the light intensity distribution of the exit pupil for some reason, safety may not be guaranteed.

[0007] The present technology has been made in view of the above circumstances, and aims to improve the safety of an illumination device that enlarges and projects an image formed by spatial light phase modulation using a projection lens.

[0008] The illumination device according to the present technology includes a light-emitting unit that emits light, a phase modulation unit that performs spatial light phase modulation on incident light from the light-emitting unit, a projection lens that enlarges and projects a reconstructed image formed by the spatial light phase modulation by the phase modulation unit, a reconstruction optical system that reconstructs the reconstructed image as a Fourier transform image on a branched optical path branched from a projection optical path that leads the reconstructed image to the projection lens, a light-receiving unit arranged so that its light-receiving surface coincides with the reconstructed image reconstruction surface on which the Fourier transform image is formed, and an anomaly detection unit that detects an anomaly related to the light intensity distribution at the exit pupil of the projection lens based on a light-receiving signal from the light-receiving unit. The light intensity distribution at the exit pupil depends on the radiant intensity distribution of the reconstructed image. Therefore, by reconstructing the reconstructed image as a Fourier transform image on a branched path from the projection optical path as described above and using a light-receiving signal of the Fourier transform image of the reconstructed image, it is possible to detect an anomaly related to the light intensity distribution at the exit pupil.

[0009] 1 is a diagram showing an example of the configuration of an illumination device as an embodiment according to the present technology. FIG. 1 is a diagram for explaining an example of the structure of a diffusing section of a fly-eye lens type movable diffuser. FIG. 2 is a diagram illustrating an example of the change characteristics of the light intensity distribution of an exit pupil image when the magnitude relationship between the lens pitch of the fly-eye lens and the size of the reproduced image is changed. FIG. 3 is an explanatory diagram of an advantage of using a fly-eye lens type movable diffuser. FIG. 4 is an explanatory diagram of a reforming optical system. FIG. 5 is a diagram showing an example of a four-segment detector. FIG. 6 is an explanatory diagram of a change that occurs in a Fourier transform image of a reproduced image in response to the movable diffuser becoming immobile. FIG. 7 is a diagram schematically showing a change in the light receiving signal value of each light receiving element when an immobility abnormality occurs in a movable diffuser from an operating state. FIG. 8 is an explanatory diagram of shifting the center of the light receiving surface with respect to the optical axis. FIG. 9 is an explanatory diagram of the effect of shifting the center of the light receiving surface with respect to the optical axis. FIG. 10 is a diagram schematically showing a change in a difference value when an abnormality in the radiation intensity distribution occurs. FIG. 11 is a diagram schematically showing a change in the light receiving signal by light receiving element A or B when an abnormality in the radiation intensity distribution occurs. 1 is a diagram showing a schematic diagram of changes occurring in the light receiving signals of the light receiving elements A to D when an abnormality in the reduction of the reproduced image size occurs. FIG. 2 is a flowchart showing an example of a specific processing procedure to be executed by a control unit to realize the abnormality detection method as an embodiment. FIG. 3 is a flowchart showing processing relating to another example of the abnormality detection method as an embodiment.

[0010] Hereinafter, with reference to the accompanying drawings, embodiments according to the present technology will be described in the following order: <1. Configuration of an illumination device as an embodiment> <2. Regarding the diffusion plate> <3. Regarding the light receiving system for detecting anomalies> <4. Anomaly detection method as an embodiment> <5. Processing procedure> <6. Modifications> <7. Summary of the embodiment> <8. The present technology>

[0011] 1 is a diagram showing an example of the configuration of a lighting device 1 according to an embodiment of the present technology. The lighting device 1 of this embodiment is configured as a device that projects an image, i.e., an image having a predetermined light intensity distribution, onto a projection surface. For example, the lighting device 1 may be configured as a device that projects an image representing predetermined letters, numbers, symbols, figures, etc. onto a road surface, or as a device known as a projector device that projects an image representing visual content such as various moving images (e.g., movies) or photographs onto a target surface such as a screen or a wall in a room.

[0012] As shown in the figure, the lighting device 1 includes an optical system 2 for forming and projecting an image having a predetermined light intensity distribution, a control unit 3, a light emission driving unit 4, a modulator driving unit 5, and an actuator driving unit 6.

[0013] The optical system 2 includes a light-emitting unit 21 that functions as a light source for image formation, a phase modulator 25 that forms an image having a light intensity distribution corresponding to the image by performing spatial light phase modulation on the light emitted from the light-emitting unit 21 in accordance with image data that indicates the content of the image to be projected, and a projection lens 28 that enlarges and projects the formed image onto a projection surface. Hereinafter, the image projected by the projection lens 28 will be referred to as a "reconstructed image," meaning an image for reconstructing the image data described above.

[0014] The light emitting unit 21 is configured to have one or more light emitting elements, such as a semiconductor laser, an LED (Light Emitting Diode), or a fluorescent light source.

[0015] The light emitted from the light emitting unit 21 is converted into parallel light by the collimating lens 22, and then enters the flat surface side of the plano-concave cylindrical lens 23. The light that has passed through the plano-concave cylindrical lens 23 is reflected by the mirror M1 and then reflected by the mirror M2, enters the convex surface side of the plano-convex cylindrical lens 24, and exits from the flat surface side of the plano-convex cylindrical lens 24 to enter the phase modulator 25.

[0016] The phase modulator 25 performs spatial light phase modulation on the incident light. In this example, a reflective liquid crystal panel is used as the phase modulator 25. As is well known, spatial light phase modulation makes it possible to change the emission direction of incident light pixel by pixel in a desired direction, thereby concentrating the incident light at a desired position, i.e., forming an image with a desired light intensity distribution at a desired position. Specifically, as described above, by setting the amount of light bending for each pixel, it is possible to concentrate light in a certain region on the imaging surface and sparse light in another region, thereby forming a desired light intensity distribution on the imaging surface. As described above, the amount of light bending for each pixel can be adjusted by changing the amount of phase modulation for each pixel, specifically, by changing the driving state of the pixel (in the case of a liquid crystal panel, the orientation state of the liquid crystal molecules).

[0017] Here, various known methods, such as a CGH (Computer Generated Hologram) calculation method, can be used to calculate a phase modulation pattern for generating an image having a desired light intensity distribution as a reconstructed image at a desired position. Specific examples of the CGH calculation method include a calculation method using the Gerchberg-Saxton algorithm, a Wirtinger Hologram algorithm, a Stochastic Gradient Descent (SGD) algorithm, and a calculation method using a learning model based on deep learning. Here, the CGH calculation method is not limited to one that uses the principle of diffraction, and a method that uses light refraction, such as the Freeform method, can also be used.

[0018] The light emitted from the phase modulator 25 is incident on the beam splitter 27 via mirrors M3, M4, and M5 as shown in the figure, and a part of the light is reflected by the splitting surface of the beam splitter 27 and incident on the projection lens .

[0019] The optical system 2 of this example is configured so that the reconstructed image formed by the spatial light phase modulation of the phase modulator 25 is focused at a position on the optical path between the mirror M5 and the beam splitter 27. The plane on which the reconstructed image is focused is referred to as the "reconstructed image plane Si." In the optical system 2, the reconstructed image formed on this reconstructed image plane Si is projected onto a projection surface by the projection lens 28.

[0020] The optical system 2 also includes a movable diffuser 26, a condenser lens 29, and a light receiving unit 30, which will be described later.

[0021] In the lighting device 1, the light emission drive section 4 has an electric circuit (drive circuit) for driving the light emitting elements provided in the light emitting section 21 to emit light, and drives the light emitting elements to emit light under the control of the control section 3.

[0022] The modulator driver 5 includes a drive circuit for driving each pixel of the phase modulator 25 , and drives each pixel of the phase modulator 25 under the control of the controller 3 .

[0023] The actuator driving unit 6 will be described later.

[0024] The control unit 3 is configured with a microcomputer having, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory), and the CPU executes processes in accordance with programs stored in the ROM to control various operations of the lighting device 1. Specifically, the control unit 3 issues instructions to the light-emitting drive unit 4 to control the start / stop of the light-emitting operation of the light-emitting unit 21, control the amount of light emitted, etc.

[0025] Furthermore, the control unit 3 controls the spatial light phase modulation in the phase modulator 25, that is, controls the phase modulation amount (pixel driving state) for each pixel. Specifically, based on the input image data, the control unit 3 calculates a phase modulation pattern for reproducing the light intensity distribution of the image represented by the image data as a reproduced image. The phase modulation pattern here refers to the phase modulation amount for each pixel of the phase modulator 25. Note that the calculation of the phase modulation pattern for generating a reproduced image having a desired light intensity distribution at a desired position can employ the Gerchberg-Saxton algorithm, the Wirtinger Hologram algorithm, or the like.

[0026] Then, the control unit 3 generates a drive signal for the phase modulator 25 based on the calculated phase modulation pattern. That is, to realize the phase modulation pattern, a drive signal is generated for each pixel of the phase modulator 25. Furthermore, the control unit 3 outputs the drive signal thus generated to the modulator driving unit 5.

[0027] The modulator driving unit 5 drives each pixel of the phase modulator 25 based on the driving signal input from the control unit 3. As a result, the phase modulator 25 performs spatial light phase modulation in accordance with the phase modulation amount for each pixel indicated by the phase modulation pattern.

[0028] In the illumination device 1, the size of the reconstructed image formed on the reconstruction image surface Si can vary depending on the size of the image projected as the projection image, and can be set by the phase modulation pattern of the phase modulator 25. If the size of the reconstructed image is too small, the light density at the exit pupil of the projection lens 28 will be excessive, so for safety reasons, a lower limit should be set for the size of the reconstructed image. In the illumination device 1 of this embodiment, a lower limit is set for such a reconstructed image size, and the control unit 3 has a function of setting the phase modulation pattern in control of the phase modulator 25 so that the size of the reconstructed image does not fall below this lower limit.

[0029] In this embodiment, the control unit 3 controls the actuator driving unit 6 and also performs various processes based on the light receiving signal of the light receiving unit 30, which will be described later.

[0030] <2. Regarding the Diffuser> As explained above, in the illumination device 1, the reproduction image is generated by spatial light phase modulation rather than spatial light intensity modulation. However, the amount of light bending due to spatial light phase modulation is at most about 2 degrees (this is just one example), and if the reproduction image is allowed to enter the projection lens 28 as is, the light density at the exit pupil of the projection lens 28 will increase, and there is a risk that safety cannot be guaranteed.

[0031] For this reason, the illumination device 1 of the embodiment is provided with a diffuser plate having a light diffusion portion positioned on the reproduction image plane Si. Specifically, in this embodiment, the diffuser plate is not a fixed type, but a movable diffuser plate 26 having a movable diffusion portion. As shown in the figure, the movable diffuser plate 26 is provided with a diffusion portion 26a positioned on the reproduction image plane Si and an actuator 26b that drives the diffusion portion 26a.

[0032] In this example, the movable diffuser 26 is a fly-eye lens type movable diffuser having a lens array of fly-eye lenses as the diffusing portion 26a.

[0033] In this example, a rotation type diffuser in which the diffusion portion 26a is rotated in a plane perpendicular to the optical axis (i.e., a plane parallel to the reproduced image plane Si) is used as the movable diffuser 26. In this case, the diffusion portion 26a is formed in a disk shape, and the actuator 26b is configured as a motor.

[0034] In this example, the actuator 26b is driven by the actuator driving unit 6, which is controlled by the control unit 13. The control unit 13 issues instructions to the actuator driving unit 6 to control the operation of the actuator 26b, such as rotating or stopping the motor.

[0035] 2A and 2B are diagrams illustrating an example of the structure of the diffusion section 26a of the fly-eye lens type movable diffuser 26, with Fig. 2A showing a plan view of the diffusion section 26a and Fig. 2B showing a cross-sectional view of the diffusion section 26a. The fly-eye lens in this case has a structure in which a plurality of lens sections, each having a hexagonal shape in a plan view, are arranged two-dimensionally, as shown in Fig. 2A. As illustrated in the cross-sectional view of Fig. 2B, each lens section is formed as a concave lens section that is thickest at the outer edge and gradually becomes thinner toward the center.

[0036] The diffusing portion 26a has the effect of diffusing the light incident on the reproduction image plane Si before it exits, and this diffusing effect has the effect of enlarging the image size at the exit pupil. In the movable diffuser plate 26 of this example, the diffusing portion 26a is driven by the actuator 26b, so that, unlike when a fixed diffuser plate is used, the diffusion pattern is not uniform but varies, thereby improving the dispersion of the light density at the exit pupil and improving safety.

[0037] At this time, in order to improve the dispersion of light density at the exit pupil, the relationship between the size of the reproduced image to be diffused and the pitch P (see FIG. 2), which is the lens pitch of the fly-eye lens, is important.

[0038] 3A and 3B show examples of the change characteristics of the light intensity distribution of the exit pupil image when the relationship between the pitch P and the size of the reconstructed image is changed. Fig. 3A shows the results when the size of the reconstructed image matches the pitch P, while Figs. 3B, 3C, and 3D show the results when the size of the reconstructed image is gradually made smaller with respect to the pitch P. As shown in the figures, when the size of the reconstructed image becomes smaller than the pitch P, a bias occurs in the light intensity distribution of the exit pupil, and this bias becomes larger as the size of the reconstructed image becomes smaller with respect to the pitch P.

[0039] Taking this into consideration, in the illumination device 1 of this embodiment, the pitch P of the fly-eye lens is determined so that safety can be ensured in terms of the light density at the exit pupil even when the size of the reproduced image is set to the minimum size.

[0040] Here, by using a fly-eye lens-type movable diffuser 26, the uniformity of the light density at the exit pupil can be improved. Figure 4 is an explanatory diagram of this point, with Figure 4A showing the light diffusion characteristics (radiant intensity distribution characteristics) when a conventional frosted-type movable diffuser is used, and Figure 4B showing the light diffusion characteristics when a fly-eye lens-type movable diffuser 26 is used. In the case of the frosted type shown in Figure 4A, it can be seen that the characteristic has a sharp light intensity peak near an angle of 0 degrees, and the light density near the optical axis at the exit pupil is high. In contrast, in the case of the fly-eye lens-type shown in Figure 4B, a so-called hat-top-shaped characteristic is obtained, with a substantially flat peak rather than a sharp peak, and it can be seen that the light density at the exit pupil is made uniform.

[0041] In this way, by adopting a fly-eye lens type, it is possible to improve the uniformity of the light density at the exit pupil, thereby improving safety.

[0042] The movable diffuser plate 26 is not limited to the rotary type exemplified above, but may be a vibration type movable diffuser plate that displaces the diffusing portion 26a on a plane perpendicular to the optical axis.

[0043] <3. Light-Receiving System for Abnormality Detection> In the illumination device 1 according to an embodiment that generates a reconstructed image by spatial light phase modulation, the following four types of abnormalities can occur as abnormalities related to the light density at the exit pupil: (1) Immobility Abnormality of the Movable Diffuser 26 (2) Abnormality in the Radiant Intensity Distribution (3) Abnormality in the Size Reduction of the Reconstructed Image (4) Abnormality in the Light-Emitting Unit 21 The immobility abnormality of the movable diffuser 26 in (1) can be, for example, when the rotation of the diffusing unit 26a stops due to a malfunction of the actuator 26b or the actuator driving unit 6. The abnormality in the radiant intensity distribution in (2) is an abnormality in the diffusing function of the movable diffuser 26 due to some factor, resulting in a deviation in the radiant intensity distribution of the reconstructed image or reduction. This abnormality can be caused, for example, by damage to a portion of the diffusing unit 26a even though the diffusing unit 26a is rotating. The abnormality in the size reduction of the reconstructed image in (3) can be, for example, when the reconstructed image size is abnormally reduced due to the phase modulation pattern of the phase modulator 25. Specifically, this can be a case where the limit function for the phase modulation pattern described above, i.e., the function of setting the phase modulation pattern so that the size of the reproduced image does not fall below the size of the lower limit, is not exhibited due to some factor, etc. The abnormality of the light-emitting unit 21 in (4) is a case where the intensity of the light emitted by the light-emitting unit 21 becomes abnormally high, and for example, a factor such as a failure of the light-emitting element of the light-emitting unit 21 can be considered.

[0044] In order to enable detection of these abnormalities, the lighting device 1 of this embodiment is provided with a reshaping optical system 31 consisting of the beam splitter 27 and the condenser lens 29 shown in FIG. 1, and a light receiving unit 30.

[0045] The reforming optical system 31 reforms the reproduced image as a Fourier transform image on a branched optical path branching from the projection optical path that leads the reproduced image to the projection lens 28. As shown in Fig. 1, light that enters the beam splitter 27 via the diffusing portion 26a of the movable diffuser 26 is partially transmitted through the splitting surface of the beam splitter 27 and enters the condenser lens 29. Fig. 5 is an explanatory diagram of the reforming optical system 31, showing an enlarged view of the reforming optical system 31 and also showing the diffusing portion 26a of the movable diffuser 26. As shown in the figure, the plane at which the light emitted from the condenser lens 29 is focused is the reproduced image reforming plane Sr on which a Fourier transform image of the reproduced image is formed.

[0046] 1, the light receiving unit 30 is configured with a light receiving element (not shown) and is arranged so that the light receiving surface Sd coincides with the reconstructed image reformation surface Sr. This light receiving unit 30 makes it possible to obtain a light receiving signal for the image formed on the reconstructed image reformation surface Sr (the above-mentioned Fourier transform image: hereinafter referred to as the "reconstructed image").

[0047] Here, the light intensity distribution at the exit pupil depends on the radiant intensity distribution of the reconstructed image, so by reconstructing the reconstructed image as a Fourier transform image on a path branched from the projection optical path as described above and obtaining a light reception signal of the Fourier transform image of the reconstructed image, it becomes possible to detect abnormalities related to the light intensity distribution at the exit pupil.

[0048] In this embodiment, the light receiving unit 30 has a split detector 30a. Specifically, in this example, a four-segment detector as shown in FIG. 6 is used as the split detector 30a. In the following, when distinguishing between the four light receiving elements 35 of the split detector 30a as a four-segment detector, identifiers A, B, C, and D as shown in the figure are used. In the light receiving unit 30, for example, a photodiode is used as the light receiving element 35.

[0049] As will be apparent from the following description, the split detector 30a is used to enable the detection of the above-mentioned abnormalities (2) and (3). However, the use of a split detector is not essential to enable the detection of the abnormalities (2) and (3).

[0050] In addition, in this specification, the "split" in "split detector" means that the amount of received light can be detected separately for each different area on the same light-receiving surface, and it does not matter whether each "split" light-receiving element is physically separated or not. In other words, each light-receiving element may be formed individually or integrally.

[0051] 4. Anomaly Detection Method According to an Embodiment The control unit 3 shown in FIG. 1 detects the above-described anomalies (1) to (4) based on the light reception signal of the light receiving unit 30.

[0052] First, the method for detecting the immobility abnormality of the movable diffuser plate 26 (1) will be described. Fig. 7 is an explanatory diagram of a change that occurs in the reformed reconstructed image (Fourier transform image of the reconstructed image) in response to the movable diffuser plate 26 becoming immobile, with Fig. 7A showing an example of the illuminance distribution on the reconstructed image reformation surface Sr when the movable diffuser plate 26 is in operation, and Fig. 7B showing an example of the same illuminance distribution when the movable diffuser plate 26 is not in motion. Figs. 7A and 7B do not show instantaneous illuminance distributions, but rather show accumulation over a period of at least one operating cycle (the rotation cycle in this example) of the diffusion section 26a.

[0053] During operation as shown in Fig. 7A, the rotation of the diffusion unit 26a causes the illuminance distribution on the reconstructed-image reformation surface Sr to be approximately uniform when averaged over time. On the other hand, during the stationary state as shown in Fig. 7B, the rotation of the diffusion unit 26a stops, and the illuminance distribution pattern on the reconstructed-image reformation surface Sr is fixed. Therefore, even when averaged over time, the illuminance distribution is not uniform as shown in Fig. 7A, and remains biased and unchanged.

[0054] The control unit 3 detects a change occurring in the reconstructed image in response to the movable diffuser plate 26 becoming immobile as an immobility abnormality of the movable diffuser plate 26. A specific detection method will be described below.

[0055] 8 is a schematic diagram showing changes in the light-receiving signal value of each light-receiving element 35 when the movable diffuser plate 26 is in operation and a stationary abnormality occurs. As shown in the figure, when the movable diffuser plate 26 is in operation, the light-receiving signal value of each light-receiving element 35 repeatedly increases and decreases periodically. When the movable diffuser plate 26 is in operation, an image based on the illuminance distribution pattern as illustrated in FIG. 7B rotates on the light-receiving surface Sd, and therefore the light-receiving signal value of each light-receiving element 35 repeatedly fluctuates in a fixed pattern with the rotation period of the diffusing portion 26a.

[0056] On the other hand, when the movable diffusion plate 26 is stationary, the light receiving signal value of each light receiving element 35 becomes substantially constant as shown in the figure.

[0057] The control unit 13 detects the immobility abnormality of the movable diffuser plate 26 by a method based on the principle that the light receiving signal value of the light receiving element 35 changes from a vibrating state to a non-vibrating state in response to the occurrence of the immobility abnormality. Specifically, the control unit 13 detects as an abnormality when the amplitude per unit time of the light receiving signal of at least one light receiving element 35 in the divided detector 30a becomes less than the threshold value THa. Here, the amplitude per unit time means the amplitude over a period of at least one cycle of the operation of the movable diffuser plate 26 (in this example, one rotation).

[0058] Although not shown in the figure, the control unit 3 in this example has a HPF (High Pass Filter) for each light receiving element 35, and these HPFs make it possible to extract the AC component of the light receiving signal for each light receiving element 35.

[0059] Then, the control unit 13 in this example extracts the AC component of the light receiving signal of each light receiving element using this HPF, and detects that the amplitude per unit time of the AC component of any light receiving element is less than the threshold value THa as an abnormality (1).

[0060] By extracting the AC component of the light reception signal, it is possible to remove the DC component that is unnecessary for detecting the immobility of the movable diffusion plate 26, thereby improving the detection accuracy.

[0061] Here, if only the immobility abnormality (1) is to be detected, there is no need to use the split detector 30a. When the split detector 30a is used, it is also possible to use the sum, difference, product, or quotient of the light receiving signal values ​​of each light receiving element as the detection target value for the immobility abnormality (1) detection (this allows the amplitude of the value per unit time to be increased, thereby improving detection accuracy).

[0062] 3, when the fly-eye lens type movable diffuser 26 is used, the smaller the size (display area) of the reproduced image, the larger the amplitude of the received light signal per unit time. Therefore, it is conceivable to set the threshold value THa according to the reproduced image size (the smaller the reproduced image size, the larger the threshold value THa).

[0063] 7, when the split detector 30a is used, there will be light receiving elements 35 in which the average value of the light receiving signal per unit time is lower when the movable diffuser plate 26 is stationary than when the movable diffuser plate 26 is in operation. From this point of view, with regard to the immobility abnormality of (1), it is also conceivable to detect as an abnormality that among the light receiving elements 35 in the split detector 30a, there is a light receiving element 35 in which the average value (DC component) of the light receiving signal per unit time is below the normal band.

[0064] Next, the detection of abnormalities in the radiation intensity distribution (2) will be described. First, in order to enable detection of abnormalities in the radiation intensity distribution, in this example, the split detector 30a is arranged so that the center Cd of the light-receiving surface Sd is shifted from the optical axis Ax, as shown in Fig. 9. Hereinafter, the direction in which the center Cd of the light-receiving surface Sd is shifted from the optical axis Ax will be referred to as the "center offset direction."

[0065] As shown in Figure 9, in this example, for the light receiving elements 35 A, B, C, and D that the split detector 30a has, the set of A and B and the set of C and D are adjacent to each other in a direction perpendicular to the center offset direction, and the set of A and C and the set of B and D are adjacent to each other in a direction parallel to the center offset direction.

[0066] Based on the light receiving signal of the split detector 30a, whose center Cd is shifted relative to the optical axis Ax as described above, the control unit 3 detects the change that occurs in the reconstructed image due to the reduction in the image size of the exit pupil caused by an abnormality in the radiation intensity distribution of the movable diffuser 26 as an abnormality (2).

[0067] 10A and 10B are explanatory diagrams illustrating the effect of shifting the center Cd with respect to the optical axis Ax. FIG. 10A shows an image of a reconstructed image formed on the light-receiving surface Sd when the radiant intensity distribution is normal, and FIG. 10B shows an image of a reconstructed image formed on the light-receiving surface Sd when the radiant intensity distribution is abnormal. As shown in FIGS. 10A and 10B , because the center Cd is shifted from the optical axis Ax, in the split detector 30a, the image area on one of the light-receiving elements 35 arranged in a direction parallel to the center offset direction is smaller than the image area on the other light-receiving element 35. When an abnormality occurs in which the image size of the exit pupil shrinks due to an abnormality in the radiant intensity distribution, the size of the reconstructed image also becomes smaller. However, when the size of the reconstructed image becomes smaller when the center Cd is shifted from the optical axis Ax, the difference in image area between the light-receiving elements 35 arranged in a direction parallel to the center offset direction becomes larger, as shown in the figures.

[0068] In this embodiment, the abnormality detection of (2) is performed based on this principle. Specifically, the control unit 3 in this example calculates an index value indicating the difference between the light receiving signals of the light receiving elements 35 arranged in a direction parallel to the center offset direction in the split detector 30a, and detects that the index value is equal to or greater than the threshold value THb as an abnormality of (2).

[0069] FIG. 11 shows a schematic diagram of the change in the difference value ((C+D)-(A+B)) when an abnormality in the radiation intensity distribution occurs.

[0070] Here, since the movable diffusion plate 26 is used in this example, the control unit 3 calculates the difference between the average values ​​of the amplitude per unit time as the index value indicating the difference.

[0071] Although not illustrated, the control unit 3 in this example has an LPF (Low Pass Filter) for each light receiving element 35, and is capable of extracting a DC component (corresponding to the average value of the light receiving signal) of each light receiving signal. The control unit 3 in this example extracts a DC component for each light receiving element 35 A to D using the LPF, calculates a difference value for each DC component by (C+D)-(A+B), and detects an abnormality (2) when this difference value is equal to or greater than a threshold value THb. This makes it possible to appropriately detect an abnormality in which the image of the exit pupil shrinks due to an abnormality in the radiant intensity distribution.

[0072] Incidentally, the detection of abnormalities in the radiation intensity distribution in (2) can also be performed when a fixed diffuser is used instead of the movable diffuser 26. When a fixed diffuser is used, the index value of the difference described above can be calculated by finding the difference between the light receiving signal values ​​sampled at a predetermined sampling timing, rather than the difference between the DC components (average values).

[0073] Furthermore, in the above, for detecting the abnormality in (2), a method using the difference in the light-receiving signals between the light-receiving elements 35 arranged in a direction parallel to the center offset direction has been exemplified, but the method for detecting the abnormality in (2) is not limited to a method using such a difference. As can be seen with reference to Fig. 10, when the center Cd is deviated from the optical axis Ax, and an abnormality in (2) occurs, the image area on one of the light-receiving elements 35 arranged in a direction parallel to the center offset direction is greatly reduced, resulting in a significant decrease in the amount of received light.

[0074] For reference, FIG. 12 shows a schematic diagram of changes in the light receiving signal from the light receiving element 35 A or B when an abnormality in the radiation intensity distribution occurs.

[0075] Based on this principle, one possible method for detecting abnormalities (2) is to calculate an index value for the amount of light received for each light receiving element 35, and detect an abnormality when the index value of any light receiving element 35 falls below the threshold value THc.

[0076] In this example, since the movable diffuser plate 26 is used, the DC component (average value) of the light reception signal is used as the "index value of the amount of received light."

[0077] The above-described method of detecting an abnormality (2) using the threshold value THc can also be performed when a fixed diffuser is used instead of the movable diffuser 26. When a fixed diffuser is used, the light reception signal value sampled at a predetermined sampling timing, rather than the DC component, can be used as the index value of the amount of received light.

[0078] Furthermore, if only the detection of abnormality (2) is required, it is not necessary to use the split detector 30a. In that case, a single light-receiving element 35 is used as the light-receiving unit 30, and this single light-receiving element 35 may be arranged to be the light-receiving element 35 A or B shown in FIG. 10B. Specifically, in this case, the center Cd of the light-receiving surface of the single light-receiving element 35 is offset upward from the optical axis Ax in the plane of FIG. 10B. The index value of the amount of light received by this single light-receiving element 35 falling below the threshold value THc is detected as an abnormality (2).

[0079] Here, it is not essential to use an LPF to find the "average value." For example, it is also possible to find the average value by performing a calculation process that averages the sampled values ​​of the received light signal for each unit time.

[0080] Next, we will explain the abnormality of the reduction in the size of the reconstructed image (3). As can be understood from the previous explanation of Figure 3, as the size of the reconstructed image is reduced, the bias in the light intensity distribution of the reconstructed image becomes greater. The control unit 3 detects, as an abnormality, any change that occurs in the reconstructed image when such a reduction in the reconstructed image occurs.

[0081] In this example, because the movable diffuser plate 26 is used, as the bias in the light intensity distribution of the reconstructed image increases, the amplitude of the received light signal from each light-receiving element 35 gradually increases. Specifically, in this example, as the diffuser plate 26 rotates, an image with a biased light intensity distribution, such as that shown in Figures 3C and 3D, rotates on the light-receiving surface Sd, and strong and weak light portions of the reconstructed image are alternately received. Therefore, compared to the normal state shown in Figure 3A, the amplitude of the received light signal from each light-receiving element 35 increases.

[0082] 13 is a schematic diagram showing changes that occur in the light receiving signals of the light receiving elements 35 A to D when an abnormality in the reduction of the reconstructed image size occurs. As shown in the figure, when an abnormality in the reduction of the reconstructed image size occurs, the amplitude of the light receiving signal of each light receiving element 35 becomes large.

[0083] The control unit 3 of this example detects the abnormality (3) using the following method. That is, the control unit 3 of this example detects as the abnormality (3) that the amplitude per unit time of the light-receiving signal of any of the light-receiving elements 35 in the split detector 30a exceeds the threshold value THd. This makes it possible to appropriately detect as an abnormality a change that occurs in the reconstructed image when an abnormality occurs in the reduction of the reconstructed image size.

[0084] Here, in the abnormality detection of (3), as in the abnormality detection of (1) above, the amplitude of the received light signal is used as a criterion for abnormality detection, so that the AC component extracted by the HPF can be used.

[0085] As can be understood from the above explanation, the abnormality detection method (3) requires that the light receiving element 35 is configured to receive only a portion of the reconstructed image, because if one light receiving element 35 were able to receive the entire reconstructed image, no fluctuation in the light receiving signal value would occur due to the operation of the movable diffuser plate 26.

[0086] Also, as can be understood from this point, if only the abnormality detection of (3) is to be performed, it is not essential to use the split detector 30a, and it is possible to adopt a configuration with a single light receiving element 35. In that case, the single light receiving element 35 is placed in a position where only a part of the reconstructed image is received, and it is determined whether or not the amplitude of the received light signal per unit time exceeds the threshold value THd.

[0087] A method for detecting an abnormality in the light-emitting unit 20 in (4) will be described. If an abnormality occurs in which the amount of light emitted by the light-emitting unit 20 is excessive, the amount of light in the reconstructed image will be excessive overall. For this reason, in the case of this example using the split detector 30a, the abnormality in (4) can be detected by detecting whether the sum of the light-receiving signals from each light-receiving element 35 is equal to or greater than a threshold value. In this example, since the average value (DC component) of each light-receiving signal is calculated when detecting an abnormality in the radiation intensity distribution in (2), a method is adopted in which an abnormality is detected when the sum of the average values ​​is equal to or greater than a threshold value THe.

[0088] 14 and 15, a specific example of a processing procedure to be executed by the control unit 3 in order to realize the anomaly detection method according to the embodiment described above will be described. The processing shown in Fig. 14 and 15 is executed by the CPU of the control unit 3 based on a program stored in a predetermined memory such as a ROM of the control unit 3. Here, although the CPU executes the processing in Fig. 14 and 15 as described above, for convenience of explanation, the processing will be expressed below as being executed by the control unit 3.

[0089] First, the process of Fig. 14 will be described. The process of Fig. 14 is a process of detecting an abnormality in the radiation intensity distribution (2) based on the difference value described above.

[0090] In the process of FIG. 14, in step S101, the control unit 3 calculates, for each light receiving element 35, the amplitude per unit time of the AC component of the light receiving signal as an AC amplitude value.

[0091] In step S102 following step S101, the control unit 3 determines whether the AC amplitude values ​​of all the light receiving elements 35 are equal to or greater than the threshold value THa. If a negative result is obtained in step S102, that is, the AC amplitude value of any of the light receiving elements 35 is less than the threshold value THa and the AC amplitude values ​​of all the light receiving elements 35 are not equal to or greater than the threshold value THa, the control unit 3 proceeds to step S103, determines that an immobility abnormality has occurred in the movable diffuser 26, and then executes light emission stop processing in step S113. That is, processing is performed to instruct the light emission drive unit 4 to stop light emission of the light emitter 21.

[0092] This allows detection of the immobility abnormality of the movable diffusion plate 26 (1) and implementation of safety measures against the abnormality.

[0093] If step S102 returns a positive result indicating that the AC amplitude values ​​of all light-receiving elements 35 are equal to or greater than the threshold value THa, the control unit 3 proceeds to step S104, where it determines whether the AC amplitude values ​​of all light-receiving elements are equal to or less than the threshold value THd. If step S104 returns a negative result indicating that the AC amplitude value of any light-receiving element 35 exceeds the threshold value THd but that the AC amplitude values ​​of all light-receiving elements are not equal to or less than the threshold value THd, the control unit 3 proceeds to step S105, where it determines that an abnormality has occurred in the reduction of the reconstructed image, and then executes the light emission stop process of step S113. This allows the detection of an abnormality in the reduction of the reconstructed image (3) and the implementation of safety measures to prevent the abnormality.

[0094] If a positive result is obtained in step S104 that the AC amplitude values ​​of all the light receiving elements are equal to or less than the threshold value THd, the control unit 3 proceeds to step S106 and acquires the DC component of the light receiving signal for each light receiving element 35. That is, the DC component of the light receiving signal extracted by the above-mentioned LPF is acquired.

[0095] In step S107 following step S106, the control unit 3 calculates the difference value of (C+D)-(A+B) for the DC component.

[0096] Then, in step S108 following step S107, the control unit 3 determines whether the difference value is equal to or greater than the threshold value THb. If a positive result is obtained in step S108 that the difference value is equal to or greater than the threshold value THb, the control unit 3 proceeds to step S109, determines that an abnormality has occurred in the radiation intensity distribution, and executes light emission stop processing in step S113. This realizes the detection of an abnormality in the radiation intensity distribution (2) and the implementation of safety measures against the abnormality.

[0097] On the other hand, if a negative result is obtained in step S108, that is, the difference value is not equal to or greater than the threshold value THb, the control unit 3 proceeds to step S110, where it calculates the total value of the DC components of all the light-receiving elements 35. Then, in the following step S111, the control unit 3 determines whether the total value is equal to or greater than the threshold value THe. If a positive result is obtained in step S111, that the total value is equal to or greater than the threshold value THe, the control unit 3 proceeds to step S112, where it determines that an abnormality has occurred in the light-emitting unit 21, and then performs light emission stop processing in step S113. This realizes the detection of an abnormality in the light-emitting unit 21 in (4) and the implementation of safety measures in response to the abnormality.

[0098] If a negative result is obtained in step S111, that is, the total value is not equal to or greater than the threshold value THe, the control unit 3 proceeds to step S114. The control unit 3 also proceeds to step S114 if the control unit 3 has executed the light emission stop process in step S113.

[0099] In step S114, the control unit 3 determines whether a processing termination condition is met. The processing termination condition may be a predetermined condition for terminating the abnormality detection processing, such as a user operation instructing the end of image projection or the execution of the light emission stop processing in step S113. If a negative result is obtained in step S114, indicating that the processing termination condition is not met, the control unit 3 returns to step S101. This allows the above-described abnormality detection processing to be repeated until an abnormality is detected.

[0100] On the other hand, if a positive result is obtained in step S114 that the processing termination condition is met, the control unit 3 terminates the series of processing steps shown in FIG.

[0101] Next, the process of Fig. 15 will be described. The process of Fig. 15 employs the method of using the threshold value THc described above as the process of detecting an abnormality in the radiation intensity distribution (2). The difference from the process shown in Fig. 14 is that the processes of steps S107 and S108 are omitted, and instead the process of step S201 is executed.

[0102] In this case, in response to executing the DC component acquisition process in step S106, the control unit 3 determines in step S201 whether or not the DC component values ​​of all the light receiving elements 35 are greater than the threshold value THc. If a positive result is obtained in step S201 that the DC component values ​​of all the light receiving elements are greater than the threshold value THc, the control unit 3 executes the processes from step S110 onward described with reference to FIG.

[0103] On the other hand, if the value of the DC component of any of the light receiving elements 35 is below the threshold value THc and a negative result is obtained in step S201, the control unit 3 determines in step S109 that the radiation intensity distribution is abnormal and proceeds to the light emission stop processing in step S113.

[0104] This makes it possible to detect the abnormality in the radiation intensity distribution (2) without calculating the difference value.

[0105] It should be noted that the execution order of the processes relating to the determinations (1) to (4) in the processes of Figures 14 and 15 is merely an example, and the order can be changed, for example, in the process of Figure 14, the determination regarding (2) (S108) can be made after the determination regarding (4) (S111).

[0106] 6. Modifications Although various embodiments according to the present technology have been described above, the present technology is not limited to the specific examples described above and may adopt configurations as various modifications. For example, although a hexagonal shape is exemplified as the shape of the fly's eye lens in the above, other shapes such as a triangle or an octagon may also be adopted.

[0107] Furthermore, although a transmission type diffusion plate has been exemplified as the diffusion plate, a reflection type diffusion plate can also be used.

[0108] Although an example in which a reflective liquid crystal panel is used as the phase modulator 25 has been given, a spatial light phase modulator other than a reflective liquid crystal panel can also be used as the phase modulator 25. For example, a transmissive liquid crystal panel can be used. Furthermore, the phase modulator is not limited to a liquid crystal panel, and devices other than a liquid crystal panel, such as a MEMS (Micro Electro Mechanical Systems) device (for example, a device configured so that the height of the mirror surface can be adjusted for each pixel), can also be used.

[0109] 7. Summary of the embodiment As described above, the illumination device (1) according to the embodiment includes a light-emitting unit (21) that emits light, a phase modulation unit (phase modulator 25) that performs spatial light phase modulation on incident light from the light-emitting unit, a projection lens (28) that enlarges and projects a reconstructed image formed by the spatial light phase modulation by the phase modulation unit, a reconstruction optical system (31) that reconstructs the reconstructed image on a branched optical path branched from the projection optical path that leads the reconstructed image to the projection lens, a light-receiving unit (30) that is positioned so that its light-receiving surface coincides with the reconstructed image reconstruction surface on which the reconstructed image is reconstructed, and an abnormality detection unit (controller 3) that detects an abnormality in the light intensity distribution at the exit pupil of the projection lens based on a light-receiving signal from the light-receiving unit. The light intensity distribution at the exit pupil depends on the radiant intensity distribution of the reconstructed image. Therefore, by reconstructing the reconstructed image as a Fourier transform image on a path branched from the projection optical path as described above and using the light reception signal of the Fourier transform image of the reconstructed image, it becomes possible to detect abnormalities related to the light intensity distribution of the exit pupil. If an abnormality in the exit pupil can be detected, it becomes possible to take measures to deal with the abnormality, such as forcibly stopping the light emitting unit, thereby improving safety.

[0110] Furthermore, the illumination device according to the embodiment includes a diffuser (movable diffuser 26) having a light diffusing portion positioned on the image plane where the image is formed. By including such a diffuser, it becomes possible to reduce the light density at the exit pupil, thereby improving safety.

[0111] Furthermore, in the lighting device according to the embodiment, the diffuser is a movable diffuser having a movable diffuser portion (26a). By providing a movable diffuser, the light density dispersion at the exit pupil can be improved compared to a fixed diffuser, and safety can be further improved.

[0112] Furthermore, in the lighting device according to the embodiment, the movable diffuser is a fly-eye lens type movable diffuser having a lens array of fly-eye lenses as a movable diffusing section. By using a fly-eye lens type movable diffuser, the light diffusion characteristics become hat-top shaped, making it possible to achieve uniform light density at the exit pupil. Therefore, safety can be improved.

[0113] In addition, in the illumination device according to the embodiment, the abnormality detection unit detects, based on the light receiving signal, a change in the Fourier transform image on the reconstructed image reformation plane in response to the movable diffuser plate becoming immobile as an abnormality. If the movable diffuser plate becomes immobile, the light density reduction effect at the exit pupil cannot be obtained, which could be an abnormality that compromises safety. With the above configuration, such immobility of the movable diffuser plate can be detected as an abnormality, contributing to improved safety.

[0114] Furthermore, in the illumination device according to the embodiment, the abnormality detection unit detects an abnormality when the amplitude of the received light signal per unit time falls below a threshold value, thereby making it possible to properly detect a change in the reconstructed image caused by the movable diffuser plate becoming immobile, and to properly detect the immobility of the movable diffuser plate as an abnormality.

[0115] Furthermore, in the lighting device according to the embodiment, the abnormality detection unit extracts the AC component of the received light signal and detects an abnormality when the amplitude of the AC component per unit time falls below a threshold. By extracting the AC component, it is possible to remove the DC component that is unnecessary for detecting immobility of the movable diffuser, thereby improving detection accuracy.

[0116] In addition, in an illumination device according to an embodiment, the light receiving unit has the center of its light receiving surface positioned off the optical axis, and the anomaly detection unit detects, based on the light receiving signal, a change in the Fourier transform image on the reconstructed image formation plane in response to a reduction in the image size of the exit pupil due to an anomaly in the radiant intensity distribution of the diffuser. When the image size of the exit pupil is reduced due to an anomaly in the radiant intensity distribution of the diffuser, the light density of the exit pupil increases, which can be an anomaly that compromises safety. With the above configuration, such a reduction in the image size of the exit pupil can be detected as an anomaly, contributing to improved safety.

[0117] Furthermore, in an illumination device according to an embodiment, the light receiving unit includes a split detector split in a direction parallel to the offset direction of the center relative to the optical axis, and the anomaly detection unit calculates an index value indicating the difference between the light receiving signals of the light receiving elements arranged in the split detector in a direction parallel to the offset direction, and detects an anomaly when the index value exceeds a threshold. Because the center of the light receiving surface is offset from the optical axis, the image area on one of the light receiving elements in the split detector arranged in a direction parallel to the offset direction becomes smaller than the image area on the other light receiving element. When the image size of the exit pupil is reduced due to an anomaly in the radiant intensity distribution, the size of the reconstructed image also becomes smaller. However, when the size of the reconstructed image is reduced when the center of the light receiving surface is offset from the optical axis, the difference in image area between the light receiving elements arranged in a direction parallel to the offset direction becomes larger. Therefore, the above configuration can detect an anomaly in the image size of the exit pupil being reduced due to an anomaly in the radiant intensity distribution, contributing to improved safety.

[0118] Furthermore, in an illumination device according to an embodiment, the light receiving unit has a split detector split in a direction parallel to the offset direction of the center relative to the optical axis, and the anomaly detection unit calculates an index value for the amount of received light for each light receiving element in the split detector and detects an anomaly when the index value of any light receiving element falls below a threshold. When the center of the light receiving surface is offset from the optical axis, an anomaly in which the image size of the exit pupil is reduced occurs, and therefore the image area on one of the light receiving elements arranged in a direction parallel to the offset direction is significantly reduced, resulting in a significant decrease in the index value for the amount of received light. Therefore, even with the above configuration, an anomaly in which the image size of the exit pupil is reduced due to an abnormality in the radiant intensity distribution can be detected, contributing to improved safety.

[0119] In addition, in an illumination device according to an embodiment, the light receiving unit has a light receiving element that receives only a portion of the Fourier transform image on the reconstructed image reformation plane, and the anomaly detection unit detects, based on the light receiving signal of the light receiving element, a change that occurs in the Fourier transform image when the reconstructed image is reduced as an anomaly. When the reconstructed image is reduced, the optical density of the exit pupil increases, which can be an anomaly that compromises safety. With the above configuration, such reduction in the reconstructed image can be detected as an anomaly, contributing to improved safety.

[0120] Furthermore, in an illumination device according to an embodiment, the light receiving unit includes a segmented detector, and the anomaly detection unit detects an anomaly when the amplitude per unit time of the light receiving signal of any of the light receiving elements in the segmented detector exceeds a threshold. When the reconstructed image is reduced due to the phase modulation pattern and the size of the reconstructed image becomes smaller than the lens pitch of the fly's eye lens, a bias in the light intensity distribution occurs in the reconstructed image. When the movable diffuser is in operation, each light receiving element of the segmented detector alternately receives strong and weak light in the reconstructed image, increasing the amplitude per unit time of the light receiving signal. Therefore, with the above configuration, it is possible to properly detect changes in the reconstructed image when the reconstructed image is reduced due to the phase modulation pattern, and to properly detect the reduction in the reconstructed image as an anomaly.

[0121] In yet another embodiment of the illumination device (see FIG. 15 ), the light receiving unit has a split detector whose center of the light receiving surface is positioned off the optical axis and which is split in a direction parallel to the direction of deviation of the center from the optical axis, and the abnormality detection unit calculates the amplitude and average value of the light receiving signal per unit time for each light receiving element in the split detector, and performs a first determination process (step S102) to determine whether the amplitude of any light receiving element in the split detector is less than a threshold, a second determination process (step S201) to determine whether the average value of any light receiving element in the split detector is equal to or less than the threshold, and a third determination process (step S105) to determine whether the amplitude of any light receiving element in the split detector exceeds the threshold. By performing the first, second, and third determination processes as described above, an illumination device can be realized that can detect abnormalities such as immobility of a movable diffuser plate, reduction in the size of an exit pupil image due to an abnormality in the radiant intensity distribution of the diffuser plate, and reduction in the size of a reproduced image.

[0122] The effects described in this specification are merely examples and are not limiting, and other effects may also be present.

[0123] 8. The Present Technology The present technology may also have the following configurations: (1) An illumination device comprising: a light-emitting unit that emits light; a phase modulation unit that performs spatial light phase modulation on incident light from the light-emitting unit; a projection lens that enlarges and projects a reconstructed image formed by the spatial light phase modulation by the phase modulation unit; a reformation optical system that reforms the reconstructed image as a Fourier transform image on a branched optical path branched from a projection optical path that leads the reconstructed image to the projection lens; a light-receiving unit that is arranged so that its light-receiving surface coincides with the reconstructed image reformation surface that is the surface on which the Fourier transform is formed; and an abnormality detection unit that detects an abnormality in the light intensity distribution of the exit pupil of the projection lens based on a light-receiving signal from the light-receiving unit. (2) The illumination device described in (1) above, comprising a diffuser plate having a light diffusion portion positioned on a reconstructed image surface that is the surface on which the reconstructed image is formed. (3) The illumination device described in (2) above, in which the diffuser plate is a movable diffuser plate having a movable diffusion portion. (4) The illumination device according to (3), wherein the movable diffuser plate is a fly-eye lens type movable diffuser plate having a lens array using fly-eye lenses as the movable diffusing portion. (5) The illumination device according to (4), wherein the abnormality detection unit detects, based on the light receiving signal, a change that occurs in the Fourier transform image on the reconstructed image reforming plane in response to the movable diffuser plate becoming stationary, as the abnormality. (6) The illumination device according to (5), wherein the abnormality detection unit detects, as the abnormality, that the amplitude of the light receiving signal per unit time is less than a threshold. (7) The illumination device according to (6), wherein the abnormality detection unit extracts an AC component of the light receiving signal, and detects, as the abnormality, that the amplitude of the AC component per unit time is less than a threshold. (8) The illumination device according to any one of (2) to (7), wherein the light receiving unit has a center of the light receiving surface positioned at a position shifted from the optical axis, and the abnormality detection unit detects, based on the light receiving signal, a change occurring in the Fourier transform on the reconstructed image reformation plane in response to a reduction in the image size of the exit pupil caused by an abnormality in the radiation intensity distribution of the diffuser plate, as the abnormality.(9) The illumination device according to (8), wherein the light receiving unit has a split detector split in a direction parallel to the direction of deviation of the center from the optical axis, and the abnormality detection unit calculates an index value indicating a difference in light reception signals of light receiving elements arranged in the split detector in a direction parallel to the direction of deviation, and detects the index value as being equal to or greater than a threshold value as the abnormality. (10) The illumination device according to (8), wherein the light receiving unit has a split detector split in a direction parallel to the direction of deviation of the center from the optical axis, and the abnormality detection unit calculates an index value for the amount of received light for each light receiving element in the split detector, and detects the index value of any light receiving element as being equal to or less than a threshold value as the abnormality. (11) The illumination device according to (4), wherein the light receiving unit has light receiving elements that receive light from only a portion of the Fourier transform image on the reconstructed image reformation plane, and the abnormality detection unit detects a change that occurs in the Fourier transform image when the reconstructed image is reduced, based on the light reception signals of the light receiving elements. (12) The illumination device according to (11), wherein the light-receiving unit has a split detector, and the abnormality detection unit detects, as the abnormality, that the amplitude per unit time of the light-receiving signal of any of the light-receiving elements in the split detector exceeds a threshold. (13) The illumination device according to (4), wherein the light-receiving unit has a split detector whose center of the light-receiving surface is positioned at a position shifted from an optical axis and which is split in a direction parallel to the direction of deviation of the center from the optical axis, and the abnormality detection unit calculates, for each light-receiving element in the split detector, an amplitude and an average value of the light-receiving signal per unit time, and performs a first determination process of determining whether the amplitude of any of the light-receiving elements in the split detector has become less than a threshold, a second determination process of determining whether the average value of any of the light-receiving elements in the split detector has become equal to or less than a threshold, and a third determination process of determining whether the amplitude of any of the light-receiving elements in the split detector has exceeded a threshold.

[0124] REFERENCE SIGNS LIST 1 Illumination device 2 Optical system 3 Control unit 4 Light emission driver 5 Modulator driver 6 Actuator driver 21 Light emitting unit 22 Collimator lens 23 Plano-concave cylindrical lens 24 Plano-convex cylindrical lens 25 Phase modulator 26 Movable diffuser 26a Diffusion unit 26b Actuator 27 Beam splitter 28 Projection lens 29 Condenser lens 30 Light receiving unit 31 Reconstruction optical system M1, M2, M3, M4, M5 Mirror Si Reconstructed image plane Sr Reconstructed image reconstruction plane Sd Light receiving surface 30a Segment detector 35 Light receiving element Ax Optical axis Cd Center

Claims

1. An illumination device comprising: a light-emitting unit that emits light; a phase modulation unit that performs spatial light phase modulation on incident light from said light-emitting unit; a projection lens that enlarges and projects a reconstructed image formed by the spatial light phase modulation by said phase modulation unit; a reconstruction optical system that reconstructs said reconstructed image as a Fourier transform image on a branched optical path that branches off from a projection optical path that leads said reconstructed image to said projection lens; a light-receiving unit that is positioned so that its light-receiving surface coincides with the reconstructed image reconstruction surface, which is the surface on which said Fourier transform image is formed; and an abnormality detection unit that detects abnormalities in the light intensity distribution of the exit pupil of said projection lens based on a light-receiving signal from said light-receiving unit.

2. The lighting device according to claim 1, further comprising a diffusion plate having a light diffusing portion positioned on the surface of the reconstructed image, which is the surface on which the reconstructed image is formed.

3. The lighting device according to claim 2, wherein the diffusion plate is a movable diffusion plate having a movable diffusion portion.

4. The lighting device according to claim 3, wherein the movable diffuser plate is a fly-eye lens type movable diffuser plate having a lens array of fly-eye lenses as the movable diffusing section.

5. The lighting device according to claim 4, wherein the abnormality detection unit detects, based on the received light signal, a change that occurs in the Fourier transform image on the reconstructed image reformation plane in response to the movable diffusion plate becoming immobile, as the abnormality.

6. The lighting device according to claim 5, wherein the abnormality detection unit detects that the amplitude of the received light signal per unit time is less than a threshold value as the abnormality.

7. The lighting device according to claim 6, wherein the abnormality detection unit extracts an AC component of the received light signal and detects that the amplitude of the AC component per unit time is less than a threshold value as the abnormality.

8. The lighting device according to claim 2, wherein the light receiving unit has the center of the light receiving surface positioned at a position offset from the optical axis, and the abnormality detection unit detects, based on the light receiving signal, a change that occurs in the Fourier transform image on the reconstructed image reformation plane in response to a reduction in the image size of the exit pupil caused by an abnormality in the radiation intensity distribution of the diffuser plate, as the abnormality.

9. The lighting device according to claim 8, wherein the light receiving unit has a split detector split in a direction parallel to the direction of deviation of the center from the optical axis, and the abnormality detection unit calculates an index value indicating the difference in light receiving signals of light receiving elements arranged in a direction parallel to the direction of deviation in the split detector, and detects the abnormality when the index value becomes equal to or greater than a threshold value.

10. The lighting device according to claim 8, wherein the light receiving unit has a split detector split in a direction parallel to the direction of deviation of the center from the optical axis, and the abnormality detection unit obtains an index value of the amount of light received for each light receiving element in the split detector, and detects as an abnormality when the index value of any light receiving element falls below a threshold value.

11. The lighting device according to claim 4, wherein the light receiving unit has a light receiving element that receives only a portion of the Fourier transform image on the reconstructed image reformation surface, and the abnormality detection unit detects, based on the light receiving signal of the light receiving element, a change that occurs in the Fourier transform image when the reconstructed image is reduced, as the abnormality.

12. The lighting device according to claim 11, wherein the light receiving unit has a split detector, and the abnormality detection unit detects as the abnormality the amplitude per unit time of the light receiving signal of any of the light receiving elements in the split detector exceeding a threshold value.

13. The lighting device according to claim 4, wherein the light receiving unit has a split detector whose center of the light receiving surface is positioned at a position offset from the optical axis and which is split in a direction parallel to the direction of offset of the center relative to the optical axis, and the abnormality detection unit calculates the amplitude and average value of the light receiving signal per unit time for each light receiving element in the split detector, and performs a first determination process to determine whether the amplitude of any light receiving element in the split detector has become less than a threshold value, a second determination process to determine whether the average value of any light receiving element in the split detector has become equal to or less than the threshold value, and a third determination process to determine whether the amplitude of any light receiving element in the split detector has exceeded the threshold value.

Images