Image display device

Abstract

An image display device (1) comprises: a light source (11) that emits light (L1) which has been modulated on the basis of a video signal and collimated; a polarizing beam splitter (12) that is positioned such that a polarizing separation film (12a) substantially has an inclination of 45° with respect to the principal ray of the light (L1); a lens system (14) that imparts a condensing action to the light (L1) which has passed through the polarizing beam splitter (12); a mirror rotation-type deflector (15) that is positioned in the vicinity of the focal position of the lens system (14) and has a mirror (15a) for reflecting the light (L1) toward the polarizing beam splitter (12); and a quarter-wave plate (13) that is positioned between the polarizing beam splitter (12) and the deflector (15).

Description

Image display device

[0001] The present invention relates to an image display device that displays an image by scanning light.

[0002] Conventionally, as an image display device that displays an image by scanning light, for example, a head-mounted display such as goggles or glasses that realize AR (Augmented Reality) or VR (Virtual Reality) has been known. In these devices, for example, light modulated by a video signal is reflected by a mirror and irradiated onto a user's eyes, or is irradiated directly onto the user's eyes.

[0003] In addition, in head-up displays installed in passenger cars, light modulated by a video signal is projected onto the windshield, and the reflected light is irradiated onto the driver's eyes, allowing the driver to see a virtual image in front of the windshield.

[0004] In these image display devices, it is required to configure the optical system for scanning light modulated by a video signal as compactly as possible.

[0005] Patent Document 1 below describes a scanner using a polarizing beam splitter (PBS). In this scanner, light emitted from a light source and transmitted through the PBS is incident on a tiltable reflector via a quarter-wave plate. The light is scanned by tilting the reflector. The light reflected by the reflector is incident on the PBS again and reflected by the PBS. The light then passes through another quarter-wave plate and is incident on another reflector. The light reflected by the other reflector is incident on the PBS again and transmitted through the PBS. The light is then guided to a pupil duplication waveguide assembly.

[0006] Special Publication No. 2022-549990

[0007] In the configuration of Patent Document 1, the PBS is positioned so that the polarization splitter film is inclined at a 45° angle with respect to the chief ray of light from the light source. However, the two lenses positioned on either side of the PBS focus the light emitted from the light source onto another reflector. This causes the angle of incidence of light incident on the polarization splitter film on the outbound and inbound paths to deviate significantly from 45°. This reduces the light transmittance and reflectance of the polarization splitter film, resulting in a decrease in light utilization efficiency.

[0008] In view of the above problem, an object of the present invention is to provide an image display device that can improve the utilization efficiency of light modulated by a video signal.

[0009] An image display device according to a main aspect of the present invention comprises a light source that emits modulated and collimated light based on a video signal, a polarizing beam splitter that is positioned so that a polarization separation film is inclined at substantially 45° with respect to the chief ray of the light, a lens system that imparts a focusing effect to the light that has passed through the polarizing beam splitter, a mirror-rotating deflector that is positioned near the focal position of the lens system and has a mirror that reflects the light toward the polarizing beam splitter, and a quarter-wave plate that is positioned between the polarizing beam splitter and the deflector.

[0010] In the image display device according to this aspect, because collimated light is incident on the polarization splitting film from the light source, the angle of incidence of the light incident on the polarization splitting film on the outbound path is substantially 45°. Furthermore, because the deflector is disposed near the focal position of the lens system, the light reflected by the deflector and then transmitted through the lens system travels in a direction substantially parallel to the optical axis of the lens system, regardless of the rotation position of the mirror. Therefore, the angle of incidence of the light incident on the polarization splitting film on the return path does not deviate significantly from 45°. Therefore, a decrease in the transmittance and reflectance of light on the polarization splitting film is suppressed on both the outbound path and the return path. This increases the utilization efficiency of light modulated by a video signal.

[0011] As described above, according to the present invention, it is possible to provide an image display device that can improve the utilization efficiency of light modulated by a video signal.

[0012] The effects and significance of the present invention will become more apparent from the following description of the embodiments, however, the embodiments shown below are merely examples of how the present invention can be implemented, and the present invention is not limited to the embodiments described below.

[0013] FIG. 1 is a diagram showing the configuration of an image display device according to embodiment 1. FIGS. 2( a) and 2(b) are side views showing the configuration of an optical system according to embodiment 1. FIG. 2(c) is a diagram showing an example configuration of a light source according to embodiment 1. FIGS. 3(a) and 3(b) are schematic diagrams showing the optical path and condensed state of light traveling through the optical system according to embodiment 1. FIGS. 4(a) to 4(d) are graphs showing the relationship between wavelength and transmittance of the polarization separation film when the angle of incidence of a light beam on the polarization separation film is changed according to embodiment 1. FIGS. 5(a) to 5(d) are graphs showing the relationship between wavelength and transmittance of the polarization separation film when the angle of incidence of a light beam on the polarization separation film is changed according to embodiment 1. FIG. 6 is a diagram showing the configuration of the optical system of an image display device according to embodiment 2. FIGS. 7(a) and 7(b) are side views showing the configuration of the optical system according to embodiment 2. FIG. 8 is a diagram showing the optical path and condensed state of light traveling through the optical system according to embodiment 2. FIG. 9 is a plan view showing the configuration of an optical system of an image display device according to Embodiment 3. FIG. 10 is a plan view showing the configuration of an optical system of an image display device according to Embodiment 4. FIG. 11 is a plan view showing the configuration of an optical system of an image display device according to Embodiment 5. FIG. 12 is a plan view showing the configuration of an optical system of an image display device according to Embodiment 6. FIGS. 13(a) and 13(b) are plan views showing the configurations of optical systems of image display devices according to Modification Examples 1 and 2, respectively. FIGS. 14(a) and 14(b) are plan views showing the configurations of optical systems of image display devices according to Modification Examples 3 and 4, respectively. FIGS. 13(a) and 13(b) are perspective and plan views, respectively, showing the configuration of an optical system of an image display device according to Modification Example 5. FIG. 16 is a plan view showing the configuration of an optical system of an image display device according to Modification Example 6. FIG. 17 is a plan view showing the configuration of an optical system of an image display device according to another modification.

[0014] However, the drawings are for illustrative purposes only and do not limit the scope of the present invention.

[0015] Hereinafter, embodiments of the present invention will be described with reference to the drawings. For convenience, each drawing is labeled with X, Y, and Z axes that are orthogonal to one another. The Z axis direction is the vertical direction of the optical system 10, and the positive X axis direction is the direction in which light is emitted from the light source 11. Hereinafter, the X axis direction and the Y axis direction may also be referred to as the horizontal direction, and the Z axis direction may also be referred to as the vertical direction.

[0016] First Embodiment FIG. 1 is a diagram showing the configuration of an image display device 1 according to a first embodiment.

[0017] The upper part of Fig. 1 shows a plan view of an optical system 10 that constitutes the image display device 1, and the lower part of Fig. 1 shows a block diagram of a circuit unit 30 that constitutes the image display device 1. Fig. 2(a) is a side view of the optical system 10 in Fig. 1 as seen in the positive direction of the Y axis, and Fig. 2(b) is a side view of the optical system 10 in Fig. 1 as seen in the negative direction of the X axis.

[0018] As shown in FIG. 1, the image display device 1 includes an optical system 10 and a circuit section 30 .

[0019] The optical system 10 includes a light source 11, a polarizing beam splitter 12 (hereinafter referred to as "PBS 12"), a quarter-wave plate 13, a lens system 14, a deflector 15, a second lens system 16, and a second deflector 17.

[0020] The light source 11 emits light L1 modulated based on a video signal under the control of the circuit unit 30. The light source 11 collimates the modulated light L1 and emits it in the positive direction of the X axis. In the first embodiment, the light L1 emitted from the light source 11 is laser light.

[0021] FIG. 2C is a diagram showing an example of the configuration of the light source 11.

[0022] In this configuration example, the light source 11 includes semiconductor lasers 101 to 103, collimator lenses 111 to 113, apertures 121 to 123, a mirror 131, and dichroic mirrors 132 and 133.

[0023] Semiconductor lasers 101 to 103 emit laser light in the red, green, and blue wavelength bands, respectively, in the negative direction of the Z axis. Collimator lenses 111 to 113 collimate the laser light of each color emitted from semiconductor lasers 101 to 103. Apertures 121 to 123 shape the beam shape of the collimated laser light of each color into a predetermined shape (for example, circular).

[0024] Mirror 131 reflects, in the positive direction of the X axis, the laser light in the red wavelength band that has passed through aperture 121. Dichroic mirror 132 transmits, in the positive direction of the X axis, the laser light in the red wavelength band that has been reflected by mirror 131, and reflects, in the positive direction of the X axis, the laser light in the green wavelength band that has passed through aperture 122. Dichroic mirror 133 transmits, in the positive direction of the X axis, the laser light in the red and green wavelength bands that has passed through dichroic mirror 132, and reflects, in the positive direction of the X axis, the laser light in the blue wavelength band that has passed through aperture 123.

[0025] The central axes of the laser beams of each color are aligned by a mirror 131 and dichroic mirrors 132 and 133. Furthermore, the emission intensities of the semiconductor lasers 101 to 103 are modulated based on a video signal. In this way, light L1 modulated by the video signal is generated.

[0026] The configuration of the light source 11 is not limited to that shown in Fig. 2(c) and can be modified in various ways. Also, in Fig. 2(c), light in red, green, and blue wavelength bands is combined to generate light L1 in order to display a color-modulated color image. However, when a monochromatic image is to be displayed, any of the semiconductor lasers may be omitted. For example, when a red image is to be displayed, the semiconductor lasers 102 and 103 may be omitted, and further, the collimator lenses 112 and 113 and the apertures 122 and 123 may be omitted.

[0027] 1 and 2(a) and (b) show the chief ray (the ray of the central axis) of light L1 traveling through the optical system 10 with a dashed line. The dashed line of the chief ray traveling on the outward path from the light source 11 to the deflector 15 is marked with a solid black arrow. The dashed line of the chief ray traveling on the return path from the deflector 15 to the second deflector 17 is marked with a hollow arrow. FIG. 1 shows the chief ray of light L1 when reflected by the mirror 15a of the deflector 15 in a state in which the mirror 15a is in the neutral position shown in FIG. 1 and in two tilt positions with maximum deflection angles parallel to the X-Y plane. The dashed lines shown within each optical element indicate the optical path of the chief ray passing through that optical element.

[0028] The PBS 12 is disposed so that the polarization separation film 12a is inclined at a substantially 45° angle with respect to the chief ray of the light L1 emitted from the light source 11. The polarization separation film 12a is disposed along a plane that is parallel to the Z axis and inclined at a substantially 45° angle with respect to the X axis and the Y axis. In a plan view, the PBS 12 has four side surfaces 12b to 12e that surround the polarization separation film 12a. The side surfaces 12b and 12c are planes parallel to the Y-Z plane, and the side surfaces 12d and 12e are planes parallel to the X-Z plane. In a plan view, the PBS 12 has a square outline. The top and bottom surfaces of the PBS 12 are planes parallel to the X-Y plane.

[0029] In the first embodiment, the light source 11 is configured so that the polarization direction of the light L1 becomes P-polarized with respect to the polarization separation film 12a. In the configuration of Fig. 2(c), the semiconductor lasers 101 to 103 are arranged so that the polarization direction of the light L1 becomes P-polarized with respect to the polarization separation film 12a. More specifically, the semiconductor lasers 101 to 103 are arranged so that the polarization direction of the linearly polarized light emitted from the semiconductor lasers 101 to 103 becomes P-polarized with respect to the polarization separation film 12a.

[0030] The quarter-wave plate 13 converts the polarization state of the light L1 incident from the PBS 12 side into circularly polarized light. The lens system 14 imparts a focusing effect to the light L1 that has passed through the PBS 12 and the quarter-wave plate 13. The lens system 14 focuses the light L1 only in the Y-axis direction, and does not focus it in the Z-axis direction. In other words, the lens system 14 focuses the parallel light incident in a direction parallel to the optical axis (the X-axis direction) into one focal line.

[0031] As shown in FIG. 2( c), when the light source 11 emits light L1 that is a composite of laser beams of multiple wavelength bands, the lens system 14 may be composed of multiple lenses to achromatize these wavelength bands. This allows the lens system 14 to provide a similar focusing effect to the light of these wavelength bands. This causes light of all wavelength bands to be focused onto a single focal line. On the other hand, when the light source 11 emits laser beam of a single wavelength band as the light L1, the lens system 14 may be composed of a single lens. Here, a refractive lens with a spherical or aspherical lens surface is used as the lens that constitutes the lens system 14.

[0032] The deflector 15 scans the light L1 in the horizontal direction (a direction parallel to the X-Y plane). The deflector 15 includes a mirror 15a for reflecting the light L1, and rotates the mirror 15a about a rotation axis 15b parallel to the Z axis. The deflector 15 is configured, for example, by a MEMS (Micro Electro Mechanical Systems) mirror. The deflector 15 may be configured in a way other than a MEMS mirror. The reflective surface of the mirror 15a is flat.

[0033] The deflector 15 is disposed near the focal position of the lens system 14. That is, the deflector 15 is disposed at a position spaced apart from the lens system 14 by the focal length F1 of the lens system 14. More specifically, the deflector 15 is disposed so that the center position of the reflecting surface of the mirror 15a (the position corresponding to the rotation axis 15b) substantially aligns with the focal position of the lens system 14.

[0034] 1 and 2(a) and (b) show the state in which the mirror 15a is in the neutral position. In this state, the reflecting surface of the mirror 15a is perpendicular to the chief ray of the incident light L1 (perpendicular to the X-axis). The deflector 15 rotates the mirror 15a around the neutral position within a predetermined range of deflection angles under the control of the circuit unit 30. As a result, the light L1 reflected by the mirror 15a is scanned in the horizontal direction (parallel to the X-Y plane).

[0035] On the return path, the light L1 reflected by the mirror 15a passes through the lens system 14 and the quarter-wave plate 13 in that order, and then enters the PBS 12. Here, since the mirror 15a of the deflector 15 is disposed near the focal position of the lens system 14 as described above, the chief ray of the light L1 reflected when the mirror 15a is tilted from its neutral position has its optical path bent by the lens system 14 and travels substantially parallel to the X-axis. Therefore, as shown in the upper part of FIG. 1 , the chief ray of the light L1 reflected by the mirror 15a enters the quarter-wave plate 13 and the PBS 12 in that order, in a state substantially parallel to the X-axis, regardless of the rotational position of the mirror 15a.

[0036] The quarter-wave plate 13 converts the light L1 transmitted on the return path into linearly polarized light that is S-polarized with respect to the polarization separation film 12a. As a result, the light L1 incident on the polarization separation film 12a on the return path is reflected by the polarization separation film 12a in the negative Y-axis direction. The light L1 then enters the second lens system 16.

[0037] The second lens system 16 provides a focusing effect to the light L1 traveling from the PBS 12 toward the second deflector 17. The second lens system 16 provides a focusing effect to the light L1 only in the X-axis direction, and does not provide a focusing effect in the Z-axis direction. In other words, the second lens system 16 focuses the parallel light incident in a direction parallel to the optical axis (the Y-axis direction) onto one focal line.

[0038] Like the lens system 14, the second lens system 16 may also be composed of multiple lenses. That is, when the light L1 is generated by combining laser beams of multiple wavelength bands, the second lens system 16 may be composed of multiple lenses to achromatize these wavelength bands. On the other hand, when the light L1 is generated by laser beams of one wavelength band, the second lens system 16 may be composed of a single lens. Here, a refractive lens with a spherical or aspherical lens surface is used as the lens that constitutes the second lens system 16.

[0039] The second deflector 17 scans the light L1 in the vertical direction (a direction parallel to the Y-Z plane). The second deflector 17 includes a mirror 17a for reflecting the light L1, and rotates the mirror 17a about a rotation axis 17b parallel to the X-axis. The second deflector 17 is formed, for example, by a MEMS mirror. The reflecting surface of the mirror 17a has a flat shape. The second deflector 17 may be a deflector having a configuration other than a MEMS mirror.

[0040] The second deflector 17 is disposed near the focal position of the second lens system 16. That is, the second deflector 17 is disposed at a position spaced apart from the second lens system 16 by the focal length F2 of the second lens system 16. More specifically, the second deflector 17 is disposed so that the center position of the reflecting surface of the mirror 17 a (the position corresponding to the rotation axis 17 b) substantially aligns with the focal position of the second lens system 16.

[0041] As shown in FIG. 2B, the second deflector 17 is disposed such that the mirror 17a is tilted in a direction parallel to the Y-Z plane from a state in which the mirror 17a is perpendicular to the principal ray of the incident light L1. That is, in the neutral position, the reflective surface of the mirror 17a is tilted upward (in the positive direction of the Z axis) by a predetermined angle from a state in which the reflective surface is perpendicular to the principal ray of the incident light L1. The second deflector 17 rotates the mirror 17a around the neutral position within a predetermined range of deflection angles under the control of the circuit unit 30. As a result, the light L1 reflected by the mirror 17a is scanned in the vertical direction (parallel to the Y-Z plane).

[0042] 2B, the second deflector 17 guides the light L1 to the outside of the PBS 12 and the second lens system 16. More specifically, the tilt angle of the mirror 17a in the neutral position is set so that the PBS 12 and the second lens system 16 are not included in the scanning range (deflection angle) of the light L1 in the vertical direction.

[0043] As shown in FIGS. 2A and 2B , the configuration of the first embodiment allows the entire optical system 10 to be thinned in the vertical direction (Z-axis direction). That is, the optical system 10 only needs to cover the range scanned by the light L1 in the horizontal direction. Therefore, each optical element constituting the optical system 10 requires a certain degree of width in the horizontal direction (X-axis direction, Y-axis direction). However, because the light L1 is not scanned within the optical system 10 in the vertical direction (Z-axis direction), the vertical width of the optical system 10 only needs to be large enough to cover the beam size of the light L1. Therefore, the entire optical system 10 can be significantly thinned in the vertical direction (Z-axis direction).

[0044] In this way, the optical system 10 is made thinner in the vertical direction, and by tilting the second deflector 17 as shown in Figure 2(b), the light L1 can be smoothly guided outside the PBS 12 and the second lens system 16. In this configuration, an image is formed by the light L1 reflected by the mirror 17a. A lens system for correcting image distortion, etc. may be further disposed after the mirror 17a.

[0045] Referring to FIG. 1, the image display device 1 includes a circuit section 30 including a control circuit 31, a light source drive circuit 32, and a scan drive circuit 33.

[0046] The control circuit 31 includes a microcomputer or an FPGA (Field Programmable Gate Array) and controls each component according to a predetermined program. The control circuit 31 controls the light source drive circuit 32 and the scan drive circuit 33 so that an image based on an input video signal is displayed. The light source drive circuit 32 drives the semiconductor lasers 101 to 103 in the light source 11 according to control from the control circuit 31. The scan drive circuit 33 drives the deflector 15 and the second deflector 17 according to control from the control circuit 31.

[0047] The control circuit 31 displays an image by a raster scan method, i.e., the control circuit 31 causes the deflector 15 to scan the light L1 modulated by the video signal in the horizontal direction, while the second deflector 17 scans it in the vertical direction, thereby displaying a frame image.

[0048] In this operation, the deflector 15 causes the light L1 modulated by a video signal to scan along multiple scan lines. The deflector 15 also moves the scanning position of the light from the end position of one scan line to the start position of the next scan line. In parallel with this movement, the second deflector 17 moves the scanning position of the light vertically by the interval between the scan lines. When scanning is completed up to the last scan line, one frame of image is displayed. When the scanning position reaches the end position of the last scan line, the deflector 15 and the second deflector 17 move the scanning position to the start position of the first scan line. Thereafter, the same operation as above is performed to display the next frame image.

[0049] 3A and 3B are diagrams schematically showing the optical path and condensed state of the light L1 traveling through the optical system 10. FIG.

[0050] Figure 3(a) shows the optical path and focusing state of light L1 when the mirror 15a of the deflector 15 is in the neutral position, and Figure 3(b) shows the optical path and focusing state of light L1 when the mirror 15a of the deflector 15 is at one of the maximum deflection angles.

[0051] 3A, as described above, collimated light L1 is emitted from the light source 11. The light L1 is incident perpendicularly on the side surface 12b of the PBS 12 and travels to the polarization separation film 12a. Because the light L1 is collimated, all rays of the light L1 are incident on the polarization separation film 12a at an incident angle of substantially 45°. The light L1 then passes through the polarization separation film 12a and travels to the quarter-wave plate 13 and lens system 14. The light L1 is focused in the Y-axis direction by the lens system 14 and forms a focal line on the mirror 15a of the deflector 15.

[0052] The light L1 reflected by the mirror 15a travels backward along the same optical path as the outward path. The light L1 enters the lens system 14 while expanding in the Y-axis direction. Because the mirror 15a is disposed at the focal position of the lens system 14, the light L1 is converted into substantially parallel light by passing through the lens system 14. The light L1 then passes through the quarter-wave plate 13 and travels toward the polarization separation film 12a of the PBS 12. At this time, the light L1 is S-polarized with respect to the polarization separation film 12a, as described above. Therefore, the light L1 is reflected by the polarization separation film 12a and travels toward the second lens system 16. The light L1 is focused in the X-axis direction by the second lens system 16, and forms a focal line on the mirror 17a of the second deflector 17.

[0053] Referring to Figure 3(b), light L1 emitted from light source 11 travels to deflector 15 in the same state as in Figure 3(a). Because mirror 15a of deflector 15 is at one of the maximum deflection angles, light L1 is reflected in a direction tilted in the positive Y-axis direction from the optical axis of lens system 14. In this direction, light L1 enters lens system 14 while spreading in a direction parallel to the X-Y plane. Here, mirror 15a is disposed at the focal position of lens system 14. Therefore, ideally, light L1 is converted into parallel light that is substantially parallel to the X-axis by passing through lens system 14.

[0054] Thereafter, the light L1 is reflected by the polarization separation film 12a and travels to the second lens system 16. The light L1 is condensed in the X-axis direction by the second lens system 16, and forms a focal line on the mirror 17a of the second deflector 17.

[0055] Generally, the lens characteristics of the lens system 14 tend to deviate from the ideal characteristics near the ends in the Y-axis direction. Therefore, as shown in FIG. 3B, when light L1 passes through the ends of the lens system 14 in the Y-axis direction, the light L1 tends to change from a parallel beam to a slightly diverged or converged state in the Y-axis direction, and its chief ray tends to be slightly tilted with respect to the X-axis. This tendency becomes more pronounced as the NA (numerical aperture) of the lens system 14 increases. Therefore, the angle of incidence of the light L1 incident on the polarization splitter film 12a near the dotted circle in FIG. 3B tends to deviate from 45°. This tendency becomes more pronounced as the NA of the lens system 14 increases.

[0056] If the incident angle of the light beam on the polarization splitting film 12a deviates from 45°, the transmittance and reflectance of the light on the polarization splitting film 12a deviate from the ideal values ​​(values ​​when the incident angle is 45°). Therefore, if the incident angle of the light beam deviates significantly from 45°, the utilization efficiency of the light L1 for image display decreases.

[0057] 4(a) to 4(d) and 5(a) to 5(d) are graphs showing the relationship between wavelength and transmittance of the polarization splitting film 12a when the angle of incidence of the light beam on the polarization splitting film 12a is changed.

[0058] These graphs are based on simulations and show the transmittance Tp when the light L1 is P-polarized light through the polarization splitting film 12a, and the transmittance Ts when the light L1 is S-polarized light through the polarization splitting film 12a. The closer the transmittance Ts is to zero, the closer the reflectance is to 100%.

[0059] FIG. 4(a) is a graph showing the transmittances Tp and Ts when the incident angle is 45°, and FIGS. 4(b) to 4(d) are graphs showing the transmittances Tp and Ts when the incident angle is decreased by 2.5° from 45°.

[0060] 4A, when the incident angle is 45°, the transmittance Tp is close to 100% and the transmittance Ts is close to 0% within the wavelength range on the horizontal axis. Therefore, when the incident angle is 45°, substantially all of the light incident on the polarization splitting film 12a as P-polarized light is transmitted through the polarization splitting film 12a, and substantially all of the light incident on the polarization splitting film 12a as S-polarized light is reflected by the polarization splitting film 12a.

[0061] As shown in Figure 4(b), when the incident angle is 42.5°, the transmittance Ts is close to 0% within the wavelength range indicated on the horizontal axis, but the transmittance Tp is slightly reduced from 100%. Therefore, when the incident angle is 42.5°, substantially all of the S-polarized light incident on the polarization splitting film 12a is reflected by the polarization splitting film 12a, but a portion of the P-polarized light incident on the polarization splitting film 12a does not pass through the polarization splitting film 12a. Therefore, the amount of P-polarized light L1 that passes through the polarization splitting film 12a is slightly reduced.

[0062] 4(c), when the incident angle is 40°, the transmittance Tp is further reduced from 100% and the transmittance Ts is slightly increased from 0% within the wavelength range on the horizontal axis. Therefore, when the incident angle is 40°, the amount of P-polarized light L1 transmitted through the polarization splitting film 12a is further reduced, and the amount of S-polarized light L1 reflected by the polarization splitting film 12a is slightly reduced.

[0063] As shown in Figure 4(d), when the incident angle is 37.5°, the transmittance Tp decreases to approximately 60-80% within the wavelength range indicated by the horizontal axis, with the transmittance Tp decreasing to approximately 60% in the red wavelength range. Also, when the incident angle is 37.5°, the transmittance Ts increases slightly from 0% within the wavelength range indicated by the horizontal axis, with the transmittance Ts increasing to approximately 35% (approximately 65% ​​reflectance) in the blue wavelength range. Therefore, when the incident angle is 37.5°, the amount of P-polarized light L1 transmitted through the polarization splitting film 12a is significantly reduced, and the amount of S-polarized light L1 reflected by the polarization splitting film 12a is significantly reduced in the blue wavelength range.

[0064] Fig. 5(a) is a graph showing the transmittances Tp and Ts when the incident angle is 45°, and Figs. 5(b) to 5(d) are graphs showing the transmittances Tp and Ts when the incident angle is increased by 2.5° from 45°. The graph in Fig. 5(a) is similar to the graph in Fig. 4(a).

[0065] The degree of decrease in transmittance Tp and the degree of increase in transmittance Ts in Figures 5(b) and (c) are similar to the degree of decrease in transmittance Tp and the degree of increase in transmittance Ts in Figures 4(b) and (c). The degree of decrease in transmittance Tp in Figure 5(d) is more significant than the degree of decrease in transmittance Tp in Figure 4(d), except in the red wavelength band. The transmittance Ts in Figure 5(d) does not increase significantly near the blue wavelength band as in Figure 4(d), and remains near 0% across all wavelength bands. Therefore, the graphs in Figures 5(b) to (d) show that as the angle of incidence increases from 45°, the transmittance Tp increases, and the rate of decrease in the amount of P-polarized light L1 transmitted through the polarization splitting film 12a increases.

[0066] From the above simulation results, it is preferable that the deviation angle of the incident light L1 incident on the polarization splitting film 12a from 45° be between -5° and +5°. This makes it possible to set the transmittance of P-polarized light L1 passing through the polarization splitting film 12a to approximately 75% or more in the wavelength range of 400 to 800 nm, and to set the transmittance of S-polarized light L1 reflected by the polarization splitting film 12a to a few percent or less. This makes it possible to maintain a high utilization efficiency of light L1 for image display.

[0067] As described above, the deviation angle of the incident angle of light L1 on the polarization split film 12a from 45° becomes more significant as the focusing action (NA) of the lens system 14 increases. Therefore, the focusing action (NA) of the lens system 14 should be set so that this deviation angle is between −5° and +5°.

[0068] The greater the focusing effect (NA) of the lens system 14, the closer the deflector 15 can be to the lens system 14, making the optical system 10 more compact in the X-axis direction. However, as described above, the greater the focusing effect (NA) of the lens system 14, the lower the utilization efficiency of the light L1. Therefore, in order to maintain a high utilization efficiency of the light L1, it is advisable to set the focusing effect (NA) of the lens system 14 as large as possible under the condition that the deviation angle of the incident angle of the light L1 with respect to 45° on the polarization split film 12a is between −5° and +5°.

[0069] <Effects of First Embodiment> According to the first embodiment, the following effects are achieved.

[0070] As shown in Figures 1 and 2(a) and (b), the image display device 1 includes a light source 11 that emits light L1 that has been modulated and collimated based on a video signal, a PBS 12 that is arranged so that a polarization separation film 12a is inclined at a substantially 45° angle with respect to the principal ray of the light L1, a lens system 14 that imparts a focusing effect to the light L1 that has passed through the PBS 12, a mirror-rotating deflector 15 that is arranged near the focal position of the lens system 14 and has a mirror 15a that reflects the light L1 toward the PBS 12, and a quarter-wave plate 13 that is arranged between the PBS 12 and the deflector 15.

[0071] With this configuration, collimated light L1 is incident on the polarization splitting film 12a from the light source 11, so the angle of incidence of light L1 incident on the polarization splitting film 12a on the outbound path is substantially 45°. Furthermore, because the deflector 15 is located near the focal position of the lens system 14, light L1 reflected by the deflector 15 and then transmitted through the lens system 14 travels in a direction substantially parallel to the optical axis of the lens system 14, regardless of the rotation position of the mirror 15a. Therefore, the angle of incidence of light L1 incident on the polarization splitting film 12a on the return path does not deviate significantly from 45°. Therefore, the transmittance and reflectance of light L1 relative to the polarization splitting film 12a are prevented from decreasing on both the outbound and return paths. This increases the utilization efficiency of light L1 modulated by a video signal.

[0072] As shown in Figures 1 and 2(a) and (b), the deflector 15 scans the light L1 in one direction (horizontal direction), and is equipped with a second deflector 17 that scans the light L1 that has been reflected by the deflector 15 and passed through the PBS 12 in a direction (vertical direction) different from the scanning direction of the deflector 15.

[0073] With this configuration, it is sufficient that at least the PBS 12 and the quarter-wave plate 13 cover the range of the light L1 scanned in the horizontal direction by the deflector 15. Therefore, although these optical elements need to have a certain horizontal width, their vertical width only needs to be large enough to cover the beam size of the light L1. Therefore, as shown in FIG. 2A, the PBS 12 and the quarter-wave plate 13 can be significantly thinned in the vertical direction (Z-axis direction).

[0074] As shown in Figures 1 and 2(a) and (b), the image display device 1 is equipped with a second lens system 16 that imparts a focusing effect to light L1 traveling from the PBS 12 toward the second deflector 17, and the second deflector 17 is positioned near the focal position of the second lens system 16.

[0075] This configuration significantly reduces the range of the light L1 incident on the second deflector 17. Therefore, the second deflector 17 can be significantly reduced in size, and the light L1 can be scanned in the vertical direction with good responsiveness.

[0076] As shown in FIG. 2B, the second deflector 17 guides the light L1 to the outside (here, above) of the PBS 12 and the second lens system 16.

[0077] With this configuration, it is sufficient that the PBS 12 and the second lens system 16, in addition to the quarter-wave plate 13 and the lens system 14, also cover the scanning range of the light L1 in the horizontal direction, so that the width in the vertical direction (Z-axis direction) can be reduced to a size that can cover the beam size of the light L1. Therefore, as shown in FIG. 2A, the entire optical system 10 can be significantly thinned in the vertical direction (Z-axis direction).

[0078] As explained with reference to Figures 4(a) to 5(d), the focusing action of the lens system 14 should be set so that the deviation angle of the incident angle of light L1 that is incident on the polarization separation film 12a after being reflected by the deflector 15 is between -5° and +5° from 45°.

[0079] This allows the light L1 incident on the polarization splitting film 12a to be efficiently guided to the second deflector 17. Therefore, the light L1 can be used highly efficiently for image display.

[0080] As shown in FIG. 2(b), the light source 11 emits light L1 that is a composite of light of multiple wavelength bands, and the lens system 14 is composed of multiple lenses and provides a similar focusing effect to the light of the multiple wavelength bands.

[0081] This configuration allows a color-modulated image to be displayed. Furthermore, the light reflected by the deflector 15 and then transmitted through the lens system 14 travels in a direction substantially parallel to the optical axis of the lens system 14, regardless of the rotation position of the mirror 15a, regardless of the wavelength band of the light. Therefore, the angle of incidence of the light incident on the polarization splitting film 12a on the return path does not deviate significantly from 45°, regardless of the wavelength band of the light. This allows the utilization efficiency of the light L1 incident on the polarization splitting film 12a on the return path to be maintained high, regardless of the wavelength band of the light. This increases the utilization efficiency of the light modulated by the video signal.

[0082] 2B, in the above-described first embodiment, the second deflector 17 guides the light L1 to the outside (here, the upper side) of the PBS 12 and the second lens system 16. In contrast, in the second embodiment, the light L1 is reflected by the second deflector 17 toward the PBS 12 and travels inside the PBS 12.

[0083] Fig. 6 is a diagram showing the configuration of the optical system 10 of the image display device 1 according to embodiment 2. Fig. 7(a) is a side view of the optical system 10 of Fig. 6 as seen in the positive direction of the Y axis, and Fig. 7(b) is a side view of the optical system 10 of Fig. 6 as seen in the negative direction of the X axis.

[0084] As shown in these figures, in the second embodiment, the second quarter-wave plate 18 is disposed between the PBS 12 and the second deflector 17. Here, the second quarter-wave plate 18 is disposed between the PBS 12 and the second lens system 16. The second deflector 17 is disposed so that the reflecting surface of the mirror 17a is perpendicular to the Y axis in the neutral position. The second deflector 17 rotates the mirror 17a at a predetermined deflection angle around the neutral position to scan the light L1.

[0085] 7(a) and (b), the width of the PBS 12, the second lens system 16, and the second quarter-wave plate 18 in the vertical direction (Z-axis direction) is enlarged compared to the configurations of FIGS. 2(a) and (b) so that the scanning range of the light L1 by the second deflector 17 can be covered.

[0086] The second lens system 16 has a focusing effect in both the horizontal direction (X-axis direction) and the vertical direction (Z-axis direction). The second lens system 16 has the effect of uniformly converging incident parallel light around the entire circumference of the optical axis (positive power). The second lens system 16 converges the incident parallel light in the X-axis direction and the Y-axis direction to focus the light at one focal point. The second deflector 17 is positioned so that the center of the reflecting surface is positioned near the focal position of the second lens system 16.

[0087] Furthermore, in the second embodiment, a third lens system 19 is disposed opposite the side surface 12 e of the PBS 12. The third lens system 19 has a function (negative power) of uniformly diffusing the incident parallel light all around the optical axis. Therefore, the third lens system 19 magnifies the image formed by the light L1 that has been reflected by the second deflector 17 and then passed through the PBS 12.

[0088] Similar to the first lens system 14 and the second lens system 16, the third lens system 19 may be configured with multiple lenses for achromatization, or may be configured with a single lens if achromatization is not required. The optical axis of the third lens system 19 is aligned with the optical axis of the second lens system 16. These optical axes also pass through the centers of the PBS 12 and the quarter-wave plate 18, respectively.

[0089] The light L1 reflected by the second deflector 17 passes through the second quarter-wave plate 18 and is converted into linearly polarized P-polarized light with respect to the polarization splitting film 12a. As a result, this light L1 passes through the polarization splitting film 12a and enters the third lens system 19. The light L1 is then diffused and its optical path is bent by the third lens system 19. An image is displayed on the image plane by the light thus projected.

[0090] FIG. 8 is a diagram schematically illustrating the optical path and condensed state of light L1 traveling through the optical system 10 according to the second embodiment.

[0091] 8 shows the optical path and condensed state of light L1 when the mirror 15a of the deflector 15 is at one of the maximum deflection angles. Light L1 reflected by the mirror 17a is diffused and enters the second lens system 16. Light L1 is converted into parallel light by passing through the second lens system 16. Light L1 then passes through the polarization separation film 12a of the PBS 12 and proceeds to the third lens system 19. Light L1 is diffused and bent by the third lens system 19 and projected onto the image plane.

[0092] 6 and 7(a) and (b), the second quarter-wave plate 18 is disposed between the PBS 12 and the second deflector 17, and the second deflector 17 reflects the light L1 toward the PBS 12. In this configuration, the second deflector 17 is also disposed near the focal position of the second lens system 16.

[0093] Even in this configuration, as shown in FIG. 7B, the light reflected by the second deflector 17 and then transmitted through the second lens system 16 travels in a direction substantially parallel to the optical axis of the second lens system 16, regardless of the rotational position of the mirror 17a. Therefore, the angle of incidence of the light L1 incident on the polarization splitting film 12a from the second deflector 17 side does not deviate significantly from 45°. This prevents a decrease in the transmittance of the light L1 through the polarization splitting film 12a. This increases the utilization efficiency of the light modulated by the video signal.

[0094] In addition, since the polarization direction of light L1 is rotated by 90° by the second quarter-wave plate 18, the optical path of light traveling from the second deflector 17 to the PBS 12 can be separated from the optical path of light L1 traveling from the deflector 15 to the PBS 12, allowing light L1 to travel smoothly to the image plane.

[0095] As shown in Figures 6 and 7(b), the optical system 10 includes a third lens system 19 that magnifies the image formed by the light L1 that has been reflected by the second deflector 17 and then passed through the PBS 12.

[0096] According to this configuration, the image can be displayed in a desired size.

[0097] Third Embodiment FIG. 9 is a plan view showing the configuration of an optical system 10 of an image display device 1 according to a third embodiment.

[0098] In comparison with the first embodiment shown in FIG. 1 , the third embodiment adds a second polarization beam splitter 20 (hereinafter referred to as the "second PBS 20"). The configuration of the second PBS 20 is similar to that of the PBS 12. The second PBS 20 includes a polarization splitting film 20a that is parallel to the Z axis and inclined at substantially 45 degrees with respect to the X and Y axes, and side surfaces 20b to 20e that surround the polarization splitting film 20a. The side surface 20d of the second PBS 20 faces the side surface 12d of the PBS 12. The second PBS 20 is positioned so that light L1 incident through the side surface 20d from the PBS 12 side becomes S-polarized light with respect to the polarization splitting film 12a.

[0099] Therefore, light L1 incident on the second PBS 20 from the PBS 12 side is reflected in the positive direction of the X axis by the polarization separation film 12a. Light L1 is then focused on the mirror 17a of the second deflector 17 by the second lens system 16. Light L1 incident on a part other than the optical axis of the second lens system 16 due to scanning by the deflector 15 has its optical path bent by the second lens system 16 and heads toward the mirror 17a of the second deflector 17.

[0100] Thereafter, the light L1 is scanned in the vertical direction (Z-axis direction) by the second deflector 17. In this case, as in Fig. 2B, the second deflector 17 also guides the light L1 to the outside of the second polarizing beam splitter 20 and the second lens system 16. In this way, an image is displayed on the image plane.

[0101] Effect of Embodiment 3 In the same manner as in Embodiment 1, in Embodiment 3, it is possible to suppress a decrease in the amount of light L1 when it is transmitted through and reflected by the polarization splitting film 12a of the deflector 15. Furthermore, since the light L1 is incident on the polarization splitting film 20a of the second PBS 20 at an incident angle of approximately 45°, it is possible to suppress a decrease in the amount of light L1 when it is transmitted through and reflected by the polarization splitting film 20a of the second PBS 20. Therefore, it is possible to maintain a high efficiency in the use of the light L1 for image display.

[0102] In the configuration of embodiment 3, too, it is preferable to set the focusing action of the lens system 14 so that the deviation angle of the incident angle of light L1 that is incident on the polarization separation film 12a of the PBS 12 after being reflected by the deflector 15 is greater than -5° and less than +5° from 45°.

[0103] This makes it possible to suppress a decrease in the amount of light L1 when the light L1 is transmitted through and reflected by the polarization separation film 12a, as in the above-described embodiment 1. Furthermore, it is also possible to suppress a deviation angle from 45° of the angle of incidence of light L1 incident on the polarization separation film 20a of the second PBS 20 from the PBS 12 side, and therefore it is possible to suppress a decrease in the amount of light L1 when the light L1 is reflected by the polarization separation film 20a.

[0104] The second lens system 16 is provided to impart a focusing effect to the light L1 traveling from the second PBS 20 toward the second deflector 17, and the second deflector 17 is disposed near the focal position of the second lens system 16.

[0105] This allows the second deflector 17 to be made smaller, as in the first embodiment.

[0106] The second deflector 17 directs the light L 1 to the outside of the second PBS 20 and the second lens system 16 .

[0107] This reduces the vertical width (Z-axis direction) of the second lens system 16, as in the first embodiment, and also reduces the vertical width of the second PBS 20. This reduces the vertical width of the entire optical system 10, making the optical system 10 more compact.

[0108] 9, the second PBS 20 is disposed compared to the configuration of the first embodiment, and therefore the number of components in the optical system 10 increases compared to the first embodiment. On the other hand, in the configuration of FIG. 9, the second PBS 20 is disposed to the side of the PBS 12, and the second deflector 17 is disposed to the side of the deflector 15. This allows the optical system 10 to be made compact in plan view. Furthermore, because the deflector 15 and the second deflector 17 are disposed to the side, these deflectors can be disposed on the same circuit board or the like to form a unit. This simplifies the arrangement of the deflector 15 and the second deflector 17 relative to the optical system 10.

[0109] Fourth Embodiment FIG. 10 is a plan view showing the configuration of an optical system 10 of an image display device 1 according to a fourth embodiment.

[0110] In the fourth embodiment, the light L1 reflected by the second deflector 17 is guided to the second PBS 20. Therefore, similar to the second embodiment, the optical system 10 is provided with a second quarter-wave plate 18 and a third lens system 19. The arrangement of the second deflector 15 relative to the second PBS 20 and the deflection angle during optical scanning are similar to the arrangement of the second deflector 15 relative to the PBS 12 and the deflection angle during optical scanning in the second embodiment.

[0111] In the fourth embodiment, the light L1 reflected by the second deflector 17 has its optical path bent parallel to the X-axis by the second lens system 16. Furthermore, the light L1 is converted by the second quarter-wave plate 18 into linearly polarized P-polarized light for the polarization splitting film 20a. The light L1 then passes through the polarization splitting film 20a and proceeds to the third lens system 19. The third lens system 19 then widens the optical path of the light L1 in the X-axis and Y-axis directions. In this way, an image is displayed on the image plane.

[0112] <Effects of Embodiment 4> As shown in FIG. 10 , the optical system 10 of the image display device 1 includes the second quarter-wave plate 18 disposed between the second PBS 20 and the second deflector 17, and the second deflector 17 reflects the light L1 toward the second PBS 20.

[0113] 10, even in this configuration, the light reflected by the second deflector 17 and then transmitted through the second lens system 16 travels in a direction substantially parallel to the optical axis of the second lens system 16, regardless of the rotation position of the mirror 17a. Therefore, the angle of incidence of the light L1 incident on the polarization splitting film 20a from the second deflector 17 side does not deviate significantly from 45°. Therefore, it is possible to prevent a decrease in the transmittance of the light L1 through the polarization splitting film 12a, and to prevent a decrease in the amount of light L1 when it passes through the polarization splitting film 20a.

[0114] In addition, since the polarization direction of light L1 is rotated by 90° by the second quarter-wave plate 18, the optical path of light traveling from the second deflector 17 to the second PBS 20 can be separated from the optical path of light L1 traveling from the PBS 12 to the second PBS 20, allowing light L1 to travel smoothly to the image plane.

[0115] In the configuration of the fourth embodiment, it is further preferable to set the light-collecting action of the lens system 14 so that the deviation angle of the incident light L1, which is incident on the polarization splitting film 20a of the second PBS 20 after being reflected by the second deflector 17, from 45° is between −5° and +5°. This makes it possible to suppress a decrease in the amount of light L1 when the light L1 passes through the polarization splitting film 12a.

[0116] As shown in FIG. 10, the optical system 10 of the image display device 1 includes a third lens system 19 that magnifies the image formed by the light L1 that has been reflected by the second deflector 17 and then passed through the second PBS 20.

[0117] According to this configuration, the image can be displayed in a desired size.

[0118] Fifth Embodiment FIG. 11 is a plan view showing the configuration of an optical system 10 of an image display device 1 according to a fifth embodiment.

[0119] In the fifth embodiment, the second PBS 20, the second lens system 16, and the second deflector 17 are arranged so as to be folded back in the X-axis direction, as compared with the third embodiment. The other configurations are the same as those of the third embodiment. In the configuration of Fig. 11 , the second deflector 17 also guides the light L1 to the outside of the second polarizing beam splitter 20 and the second lens system 16. As a result, an image is displayed on the image plane.

[0120] <Effects of Fifth Embodiment> In the fifth embodiment, the same effects as those in the third embodiment are achieved.

[0121] However, in embodiment 5, since the deflector 15 and the second deflector 17 are not adjacent to each other, the optical system 10 cannot be made compact in plan view as in embodiment 3, and the deflector 15 and the second deflector 17 cannot be unitized and arranged in the optical system 10.

[0122] Sixth Embodiment FIG. 12 is a plan view showing the configuration of an optical system 10 of an image display device 1 according to a sixth embodiment.

[0123] In the sixth embodiment, compared to the fourth embodiment, the second PBS 20, the second quarter-wave plate 18, the second lens system 16, the second deflector 17, and the third lens system 19 are arranged so as to be folded in the X-axis direction. The other configurations are the same as those of the fourth embodiment. In the configuration of Fig. 12 , the second deflector 17 also guides the light L1 to the second PBS 20. The light L1 passes through the polarization separation film 20a of the second PBS 20 and proceeds to the third lens system 19. As a result, an image is displayed on the image plane.

[0124] <Effects of Sixth Embodiment> In the sixth embodiment, the same effects as those in the fourth embodiment are achieved.

[0125] However, in embodiment 6, since the deflector 15 and the second deflector 17 are not adjacent to each other, the optical system 10 cannot be made compact in plan view as in embodiment 4, and the deflector 15 and the second deflector 17 cannot be unitized and arranged in the optical system 10.

[0126] 13A, the lenses constituting the lens system 14 may be integrated with the side surface 12c of the PBS 12, and the lenses constituting the second lens system 16 may be integrated with the side surface 12d of the PBS 12. The lenses may be integrated with the PBS 12 using, for example, a light-transmitting adhesive.

[0127] When the lens system 14 is made up of a plurality of lenses, one of the lenses may be integrated into the side surface 12c of the PBS 12, and when the second lens system 16 is made up of a plurality of lenses, one of the lenses may be integrated into the side surface 12d of the PBS 12. These lenses may also be formed integrally with the PBS 12. In this case, the surfaces of these lenses form the side surfaces of the PBS 12.

[0128] According to the configuration of the first modified example, the lenses that make up the lens system 14 and the second lens system 16 are integrated into the PBS 12, so that the optical system 10 can be made compact.

[0129] 13B, the configuration of Embodiment 2 can also be modified in the same manner as in Modification 1. Here, the lens constituting the third lens system 19 is further integrated with the side surface 12e of the PBS 12. When the third lens system 19 is composed of multiple lenses, one of the lenses is integrated with the side surface 12e of the PBS 12. As in Modification 1, this lens may be formed integrally with the PBS 12.

[0130] According to the configuration of the second modification, the lenses that make up the lens system 14 and the second lens system 16, as well as the lenses that make up the third lens system 19, are integrated into the PBS 12, so that the optical system 10 can be made compact.

[0131] In the configurations of embodiments 3 to 6, as in modified examples 1 and 2, the lenses constituting lens system 14 may be integrated with PBS 12, and the lenses constituting second lens system 16 and third lens system 19 may be integrated with second PBS 20.

[0132] <Modification 3> In the above-described first embodiment, lens system 14 and second lens system 16 are each composed of one or more refractive lenses, but as the lenses that make up lens system 14 and second lens system 16, a diffractive lens (hologram diffraction element) in which a diffraction hologram is formed on the incident surface or exit surface of light L1 may be used, or a volume hologram having a refractive index distribution therein may be used.

[0133] FIG. 14A is a plan view showing the configuration of the optical system 10 when diffractive lenses or volume holograms are used as lenses that make up the lens system 14 and the second lens system 16. FIG.

[0134] In this configuration, when the light source 11 emits light L1 including multiple wavelength bands, as in the configuration of Fig. 2(c), the lens system 14 and the second lens system 16 can be configured with multiple diffractive lenses or multiple volume holograms that act individually on the light of these wavelength bands. For example, when a diffractive lens is used, wavelength-selective diffractive holograms that act on different wavelength bands may be formed on the entrance surface and exit surface of a single diffractive lens.

[0135] Alternatively, a plurality of diffractive lenses corresponding to different wavelength bands may be stacked and integrated to form the lens system 14 or the second lens system 16. Alternatively, a plurality of volume holograms corresponding to different wavelength bands may be integrated to form the lens system 14 or the second lens system 16. The integration can be performed, for example, with a light-transmitting adhesive.

[0136] In this way, when the lens system 14 and the second lens system 16 are respectively configured by integrating multiple diffractive lenses or multiple volume holograms, the respective integrated structures may be integrated with the side surfaces 12c and 12d of the PBS 12, as in the above-described first modification. The structures may be integrated with the PBS 12 using, for example, an optically transparent adhesive. This allows the optical system 10 to be made smaller.

[0137] Furthermore, when the respective structures are integrated with the side surfaces 12c and 12d of the PBS 12 in this manner, the quarter-wave plate 13 and the second quarter-wave plate 18 may be further integrated with the PBS 12 with the integrated structures, thereby enabling the optical system 10 to be made even more compact.

[0138] <Modification 4> As shown in Fig. 14(b) , in the configuration of Embodiment 2, the lens system 14 and the second lens system may be configured with a diffractive lens or a volume hologram, as in Modification 3. In Fig. 14(b) , a third lens system 19 is also configured with a diffractive lens or a volume hologram.

[0139] When the third lens system 19 is composed of multiple diffractive lenses or multiple volume holograms, these may be stacked and integrated. This integration may be performed, for example, with an optically transparent adhesive. In this case, too, the integrated structure may be integrated with the side surface 12 e of the PBS 12 with an optically transparent adhesive or the like. This allows the optical system 10 to be made smaller.

[0140] Although the above describes modified examples 1 and 2 of embodiments 1 and 2, in the configurations of embodiments 3 to 6, lens system 14 may similarly be configured as a diffractive lens or a volume hologram, and second lens system 16 and third lens system 19 may also be configured as diffractive lenses or volume holograms.

[0141] <Modification 5> In the above-described first embodiment, two deflectors 15 and 17 are used to scan the light L1 in the horizontal and vertical directions, but the light L1 may be scanned in the horizontal and vertical directions using one biaxially driven deflector.

[0142] 15A and 15B are a perspective view and a plan view, respectively, showing the configuration of an optical system 10 according to Modification 5. For convenience, the light source 11 is not shown in FIG. 15A.

[0143] In the optical system 10 according to the fifth modification, a lens system 21 and a deflector 22 are disposed downstream of the quarter-wave plate 13. The lens system 21 uniformly focuses the light L1 around the entire circumference of the optical axis. That is, the lens system 21 focuses parallel light incident in a direction parallel to the optical axis (the X-axis direction) to a single focal point. The lens system 21 is composed of one or more refractive lenses. As in the third modification, the lens system 21 may be composed of a diffractive lens or a volume hologram.

[0144] The deflector 22 scans the light L1 in the horizontal direction (a direction parallel to the X-Y plane) and the vertical direction (a direction parallel to the X-Z plane). The deflector 22 includes a mirror 22a for reflecting the light L1, and rotates the mirror 22a about a rotation axis 22b parallel to the Z axis and a rotation axis 22c parallel to the Y axis. More specifically, the mirror 22a is supported by a frame 22d via the rotation axis 22b and rotates in the horizontal direction relative to the frame 22d. Rotating the frame 22d about the rotation axis 22c rotates the mirror 22a in the vertical direction.

[0145] The deflector 22 is configured, for example, by a MEMS mirror. The deflector 22 may be configured in a manner other than a MEMS mirror. The reflective surface of the mirror 22 a is flat. The two rotation axes 22 b and 22 c do not necessarily have to be orthogonal to each other, as long as they intersect with each other.

[0146] The deflector 22 is disposed near the focal position of the lens system 21. That is, the deflector 22 is disposed at a position spaced apart from the lens system 21 by the focal length F3 of the lens system 21. More specifically, the deflector 22 is disposed so that the center position of the reflecting surface of the mirror 22a (the position where the rotation axes 22b and 22c intersect) substantially aligns with the focal position of the lens system 21.

[0147] By disposing the polarizer 22 in this manner, the light L1 reflected by the mirror 22a is incident on the polarization separation film 12a of the PBS 12 at an incident angle of substantially 45° due to the action of the lens system 21, regardless of whether the mirror 22a is rotated horizontally or vertically. Therefore, similar to the first embodiment, a decrease in the transmittance and reflectance of the light L1 relative to the polarization separation film 12a is suppressed in both the outbound and inbound paths, and the utilization efficiency of the light L1 modulated by the video signal can be increased.

[0148] According to the configuration of Modification 15, the light L1, which is reflected by the mirror 22a and then transmitted through the quarter-wave plate 13, is reflected by the polarization separation film 12a and is projected directly onto the image plane. By rotating the mirror 22a of the polarizer 22 about the rotation axes 22b and 22c, the light L1 is scanned across the image plane, and an image is displayed on the image plane.

[0149] According to the configuration of modified example 15, it is not necessary to place the second lens system 16 and the second polarizer 17 on the image plane side of the PBS 12 as in the above-mentioned embodiment 1, so the number of parts can be reduced and the optical system 10 can be made compact.

[0150] 16 , the configuration of Modification Example 5 can also be modified in the same manner as in Embodiment 2. In Modification Example 6, another lens system 23 is disposed between the PBS 12 and the image plane. The configuration of the other lens system 23 is similar to that of the third lens system 19 in Embodiment 2. This allows the image formed by the light L1 that has passed through the PBS 12 to be enlarged by the other lens system 23, and the image can be displayed at a desired size.

[0151] As in the second modification, the third lens system 19 may be integrated into the PBS 12. This allows the optical system 10 to be made even more compact.

[0152] <Other Modifications> In the first to sixth embodiments, the optical system 10 is configured so that the light L1 emitted from the light source 11 becomes P-polarized light with respect to the PBS 12. However, the optical system 10 may be configured so that the light L1 emitted from the light source 11 becomes S-polarized light with respect to the PBS 12. In this case, the optical system of the first embodiment is modified, for example, as shown in Fig. 17. In this configuration, the light incident on the second deflector 17 is reflected in the negative Y-axis direction and projected onto the image plane.

[0153] 4(a) to 5(d), the variation in transmittance due to deviation of the incident angle from 45° is smaller for S-polarized light than for P-polarized light. Therefore, when the light reflected by the second deflector 17 is not returned to the PBS 12 as in the first embodiment, it is preferable to configure the optical system 10 so that the light L1 emitted from the light source 11 becomes P-polarized light with respect to the PBS 12, as in the first embodiment, and to make the light L1 incident on the polarization separation film 12a as S-polarized light on the return path.

[0154] In the first embodiment, the light L1 reflected by the second deflector 17 is scanned so as to deviate above the second lens system 16 and the PBS 12 (positive side of the Z axis), but the direction in which the light L1 is deviated is not limited to this. For example, the second deflector 17 may scan the light L1 so that the light L1 reflected by the second deflector 17 deviates below the second lens system 16 and the PBS 12 (negative side of the Z axis).

[0155] Similarly, in the above-described third and fifth embodiments, the light L1 reflected by the second deflector 17 is scanned so as to deviate above the second lens system 16 and the second PBS 20 (positive side of the Z axis), but the direction in which the light L1 is deviated is not limited to this. For example, the second deflector 17 may scan the light L1 so that the light L1 reflected by the second deflector 17 deviates below the second lens system 16 and the second PBS 12 (negative side of the Z axis).

[0156] Furthermore, in the above embodiments 1 to 6, the deflector 15 scans the light L1 in the horizontal direction, and the second deflector 17 scans the light L1 in the vertical direction, but the deflector 15 may scan the light L1 in the vertical direction, and the second deflector 17 may scan the light L1 in the horizontal direction.

[0157] However, in this configuration, the sizes of the PBS 12, the quarter-wave plate 13, and the lens system 14 become larger in the Z-axis direction. Also, in a configuration in which the second deflector 17 deflects the light L1 from the PBS 12 and the second lens system 16, as in the first embodiment, it becomes difficult to deflect the light L1 from these optical elements. Therefore, taking these points into consideration, it is preferable that the deflector 15 scans the light L1 in the horizontal direction and the second deflector 17 scans the light L1 in the vertical direction, as in the first to sixth embodiments.

[0158] The scanning direction of the deflector 15 and the scanning direction of the second deflector 17 do not necessarily have to be perpendicular to each other. As long as an image can be displayed on the image plane, the scanning direction of the deflector 15 and the scanning direction of the second deflector 17 may be deviated from the perpendicular direction.

[0159] Furthermore, in the above-described first, third, and fifth embodiments, the second deflector 17 is a reflective deflector, but a transmissive deflector may be used as the second deflector 17. For example, the second deflector 17 may be configured so that a transmissive diffractive optical element (DOE) that diffracts the light L1 only in the positive direction of the Z axis is rotated about an axis parallel to the X axis.

[0160] The embodiments of the present invention can be modified in various ways as appropriate within the scope of the technical idea defined in the claims.

[0161] (Additional Notes) The above description of the embodiments discloses the following techniques.

[0162] (Technology 1) An image display device comprising: a light source that emits light that has been modulated and collimated based on a video signal; a polarizing beam splitter that is positioned so that a polarization separation film is inclined at a substantially 45° angle with respect to a chief ray of the light; a lens system that imparts a focusing effect to the light that has passed through the polarizing beam splitter; a mirror-rotating deflector that is positioned near the focal position of the lens system and has a mirror that reflects the light toward the polarizing beam splitter; and a quarter-wave plate that is positioned between the polarizing beam splitter and the deflector.

[0163] According to this technology, because collimated light is incident on the polarization splitting film from the light source, the angle of incidence of the light incident on the polarization splitting film on the outward path is substantially 45°. Furthermore, because the deflector is located near the focal position of the lens system, the light reflected by the deflector and then transmitted through the lens system travels in a direction substantially parallel to the optical axis of the lens system, regardless of the rotation position of the mirror. Therefore, the angle of incidence of the light incident on the polarization splitting film on the return path does not deviate significantly from 45°. Therefore, a decrease in the transmittance and reflectance of light on the polarization splitting film is suppressed on both the outward path and the return path. This increases the utilization efficiency of light modulated by a video signal.

[0164] (Technology 2) In the image display device described in Technology 1, the deflector scans the light in one direction, and the image display device is provided with a second deflector that scans the light that has been reflected by the deflector and passed through the polarizing beam splitter in a direction different from the scanning direction of the deflector.

[0165] According to this technology, it is sufficient that the polarizing beam splitter and the quarter-wave plate cover at least the range of light scanned by the deflector. Therefore, although these optical elements need to be large enough in width in the scanning direction, their width in the direction perpendicular to the scanning direction only needs to be large enough to cover the beam size of the light. This allows the polarizing beam splitter and the quarter-wave plate to be significantly smaller in size in the direction perpendicular to the scanning direction.

[0166] (Technology 3) The image display device according to Technology 2, further comprising a second lens system that imparts a focusing effect to the light traveling from the polarizing beam splitter toward the second deflector, and the second deflector is disposed near a focal position of the second lens system.

[0167] This technique significantly reduces the range of light incident on the second deflector, thereby significantly reducing the size of the second deflector and enabling the light to be scanned with good responsiveness in the scanning direction of the second deflector.

[0168] (Technology 4) In the image display device according to Technology 2 or 3, the second deflector guides the light to the outside of the polarizing beam splitter and the second lens system.

[0169] According to this technology, in addition to the quarter-wave plate and lens system, the polarizing beam splitter and second lens system only need to cover the scanning range of light in the scanning direction of the deflector. Therefore, the width of these optical elements in the direction perpendicular to the scanning direction of the deflector can be reduced to a size that can cover the beam size of light. This allows for a significant reduction in the size of the optical system of the image display device.

[0170] (Technology 5) The image display device according to Technology 2 or 3, further comprising a second quarter-wave plate disposed between the polarizing beam splitter and the second deflector, wherein the second deflector reflects the light toward the polarizing beam splitter.

[0171] According to this technology, the polarization direction of the light is rotated by 90 degrees by the second quarter-wave plate, so that the optical path of the light traveling from the second deflector to the polarizing beam splitter can be separated from the optical path of the light traveling from the deflector to the polarizing beam splitter, allowing the light to travel smoothly to the image plane.

[0172] (Technology 6) The image display device according to Technology 5, further comprising a third lens system that magnifies an image formed by the light that has been reflected by the second deflector and then passed through the polarizing beam splitter.

[0173] This technique allows an image to be displayed on the image plane at a desired size.

[0174] (Technology 7) The image display device according to Technology 2, further comprising a second polarizing beam splitter into which the light that has been reflected by the deflector and passed through the polarizing beam splitter is incident, and the light that has passed through the second polarizing beam splitter is incident on the second deflector.

[0175] According to this technique, light is incident on the polarization splitting film of the second polarizing beam splitter at an incident angle of approximately 45°, which makes it possible to suppress the reduction in the amount of light when the light is transmitted through and reflected from the polarization splitting film of the second polarizing beam splitter, thereby maintaining a high efficiency of light utilization for image display.

[0176] (Technology 8) The image display device according to Technology 7, further comprising a second lens system that imparts a focusing effect to the light traveling from the second polarizing beam splitter toward the second deflector, and the second deflector is disposed near the focal position of the second lens system.

[0177] This technique allows the second deflector to be made smaller.

[0178] (Technology 9) In the image display device according to Technology 7 or 8, the second deflector guides the light to the outside of the second polarizing beam splitter and the second lens system.

[0179] This technique allows the widths of the second polarizing beam splitter and the second lens system to be reduced, thereby reducing the width of the optical system of the image display device and making the optical system more compact.

[0180] (Technology 10) The image display device according to Technology 7 or 8, further comprising a second quarter-wave plate disposed between the second polarizing beam splitter and the second deflector, wherein the second deflector reflects the light toward the second polarizing beam splitter.

[0181] According to this technology, the polarization direction of the light is rotated by 90 degrees by the second quarter-wave plate, so that the optical path of the light traveling from the second deflector to the second polarizing beam splitter can be separated from the optical path of the light traveling from the polarizing beam splitter to the second polarizing beam splitter, allowing the light to travel smoothly to the image plane.

[0182] (Technology 11) The image display device according to Technology 10, further comprising a third lens system that magnifies an image formed by the light that has been reflected by the second deflector and then passed through the second polarizing beam splitter.

[0183] This technique allows an image to be displayed on the image plane at a desired size.

[0184] (Technology 12) In the image display device according to any one of Techniques 7 to 11, the second polarizing beam splitter is arranged to the side of the polarizing beam splitter, and the second deflector is arranged to the side of the deflector.

[0185] This technology allows the optical system of the image display device to be made compact in plan view. Furthermore, since the deflector and the second deflector are arranged side by side, these deflectors can be arranged on the same circuit board or the like to form a unit. This simplifies the arrangement of the deflector and the second deflector relative to the optical system.

[0186] (Technology 13) In the image display device according to any one of technologies 1 to 12, the deviation angle of the incident angle of the light that is incident on the polarization separation film after being reflected by the deflector from 45° is set to be between −5° and +5° by the focusing effect of the lens system.

[0187] This technique allows light incident on the polarization splitting film to be efficiently guided to the second deflector, thereby maintaining high light utilization efficiency for image display.

[0188] (Technology 14) In the image display device described in any one of technologies 1 to 13, the light source emits light of a plurality of wavelength bands as the light, and the lens system is composed of a plurality of lenses and provides a similar focusing effect to the light of the plurality of wavelength bands.

[0189] This technology makes it possible to display a color-modulated image. Furthermore, light reflected by the deflector and then transmitted through the lens system travels in a direction substantially parallel to the optical axis of the lens system, regardless of the rotational position of the deflector mirror, regardless of the wavelength band of the light. Therefore, the angle of incidence of light incident on the polarization splitting film on the return path does not deviate significantly from 45°, regardless of the wavelength band of the light. This makes it possible to maintain a high utilization efficiency of light incident on the polarization splitting film on the return path, regardless of the wavelength band of the light. Therefore, it is possible to increase the utilization efficiency of light modulated by a video signal.

[0190] (Technology 15) In the image display device according to Technology 1, the deflector rotates the mirror about two mutually intersecting rotation axes to scan the light in two directions.

[0191] According to this technique, it is not necessary to place a second lens system and a second polarizer on the image plane side of the polarizing beam splitter, so the number of parts can be reduced and the optical system can be made compact.

[0192] (Technology 16) The image display device according to Technology 15, further comprising another lens system that magnifies an image formed by the light that has been reflected by the deflector and then passed through the polarizing beam splitter.

[0193] According to this technology, an image formed by light passing through a polarizing beam splitter can be enlarged by another lens system, and an image can be displayed at a desired size.

[0194] REFERENCE SIGNS LIST 1 image display device 10 optical system 11 light source 12 PBS 13 1 / 4 wave plate 14, 21 lens system 15, 22 deflector 16 second lens system 17 second deflector 18 second 1 / 4 wave plate 19 third lens system 20 second PBS 20a polarization separation film 23 other lens system

Claims

1. An image display device comprising: a light source that emits modulated and collimated light based on a video signal; a polarizing beam splitter that is positioned so that a polarizing separation film is inclined at a substantially 45° angle with respect to the principal ray of the light; a lens system that imparts a focusing effect to the light that has passed through the polarizing beam splitter; a mirror-rotating deflector that is positioned near the focal position of the lens system and has a mirror that reflects the light toward the polarizing beam splitter; and a quarter-wave plate that is positioned between the polarizing beam splitter and the deflector.

2. An image display device according to claim 1, characterized in that the deflector scans the light in one direction, and a second deflector is provided which scans the light which has been reflected by the deflector and passed through the polarizing beam splitter in a direction different from the scanning direction of the deflector.

3. An image display device as described in claim 2, further comprising a second lens system that provides a focusing effect to the light traveling from the polarizing beam splitter toward the second deflector, and the second deflector is disposed near the focal position of the second lens system.

4. An image display device according to claim 3, characterized in that the second deflector directs the light to the outside of the polarizing beam splitter and the second lens system.

5. An image display device according to claim 3, further comprising a second quarter-wave plate disposed between the polarizing beam splitter and the second deflector, the second deflector reflecting the light toward the polarizing beam splitter.

6. An image display device according to claim 5, further comprising a third lens system for magnifying an image formed by the light that has been reflected by the second deflector and then passed through the polarizing beam splitter.

7. An image display device according to claim 2, further comprising a second polarizing beam splitter onto which the light that has been reflected by the deflector and passed through the polarizing beam splitter is incident, and the light that has passed through the second polarizing beam splitter is incident on the second deflector.

8. An image display device as described in claim 7, further comprising a second lens system that imparts a focusing effect to the light traveling from the second polarizing beam splitter toward the second deflector, and the second deflector is disposed near the focal position of the second lens system.

9. An image display device according to claim 8, wherein the second deflector directs the light to the outside of the second polarizing beam splitter and the second lens system.

10. An image display device according to claim 8, further comprising a second quarter-wave plate disposed between the second polarizing beam splitter and the second deflector, the second deflector reflecting the light toward the second polarizing beam splitter.

11. An image display device according to claim 10, further comprising a third lens system for magnifying an image formed by the light that has been reflected by the second deflector and then passed through the second polarizing beam splitter.

12. An image display device according to claim 7, characterized in that the second polarizing beam splitter is arranged to the side of the polarizing beam splitter, and the second deflector is arranged to the side of the deflector.

13. An image display device according to claim 1, characterized in that the deviation angle of the incident angle of the light which is reflected by the deflector and then enters the polarization separation film from 45° is set to be between -5° and +5° by the focusing effect of the lens system.

14. An image display device according to claim 1, characterized in that: the light source emits light of a plurality of wavelength bands as the light; and the lens system is composed of a plurality of lenses and provides a similar focusing effect to the light of the plurality of wavelength bands.

15. An image display device according to claim 1, wherein the deflector rotates the mirror about two mutually intersecting rotation axes to scan the light in two directions.

16. An image display device according to claim 15, further comprising another lens system for magnifying an image formed by the light that has been reflected by the deflector and then passed through the polarizing beam splitter.

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