Optical element, optical apparatus, and projector

Abstract

To reduce the difference of light intensity in a polarization direction of color light emitted from an optical element.SOLUTION: An optical element according to an embodiment comprises: a light permeable substrate; a first optical thin film provided on a first plane of the light permeable substrate, for reflecting first light of a first wavelength band out of the visible wavelength band and passing infrared light of an infrared wavelength band through; and a second optical thin film provided on a second plane of the light permeable substrate, for passing second light of a second wavelength band out of the infrared wavelength band through. The transmittance of the first optical thin film to infrared light entering at an incidence angle of 30° to 60° inclusive is 90% or greater. When S-polarization or P-polarization of the second light the difference of which between maximum transmittance and minimum transmittance when entering the first optical thin film at the incidence angle of 30° to 60° inclusive is larger than the other is assumed to be first polarization, there is a range of incidence angles where the plus and minus of inclination of the incidence angle dependency curve of transmittance to first polarization of the second light of the first optical thin film and the plus and minus of inclination of the incidence angle dependency curve of transmittance to the first polarization of the second light of the second optical thin film are mutually opposite.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an optical element, an optical device, and a projector. [Background technology]

[0002] 2. Description of the Related Art Optical devices such as projectors use optical elements such as mirrors for coaxially overlapping and synthesizing colored light beams emitted from a plurality of light sources arranged at different positions.

[0003] For example, Patent Document 1 discloses a light source device including a light emitting diode (LED) that emits visible light and an LED that emits infrared light, which are arranged at different positions as light sources, and a dichroic mirror that coaxially combines the visible light and infrared light emitted from the two LEDs. The dichroic mirror of the light source device disclosed in Patent Document 1 transmits infrared light including near-infrared light, reflects visible light, and emits it onto an optical path coaxial with the red light. The visible light and infrared light emitted from the dichroic mirror are incident on a liquid crystal panel, and at least the visible light is modulated according to image information. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-042431 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the light source device of Patent Document 1, visible light and red light are incident on the dichroic mirror at an angle. As a result, in the light source device of Patent Document 1, differences in the characteristics of S-polarized light and P-polarized light occur in the visible light and infrared light emitted from the dichroic mirror. In particular, the transmittance of infrared light passing through the dichroic mirror tends to decrease as the angle at which the infrared light is incident with respect to the optical axis increases. In optical devices that use multiple polarized light, including S-polarized and P-polarized light, large differences in the characteristics of the multiple polarized light, as described above, can cause uneven illumination in the output image or optical pattern. In other words, when light emitted from multiple light sources located at different positions is superimposed on a coaxial optical path using an optical element, measures are needed to reduce the difference in light intensity in the polarization direction of the colored light emitted from the optical element. [Means for solving the problem]

[0006] An optical element according to one embodiment of the present invention includes a light-transmitting substrate having a first surface and a second surface opposite to the first surface; a first optical thin film provided on the first surface, the first optical thin film reflecting first light in a first wavelength band within a visible wavelength band and transmitting infrared light in an infrared wavelength band; and a second optical thin film provided on the second surface, transmitting second light in a second wavelength band within the infrared wavelength band. The first optical thin film has a transmittance of 90% or greater for infrared light incident at an incident angle of 30° to 60°. When the first polarization is defined as S-polarized or P-polarized second light having a larger difference between the maximum transmittance and the minimum transmittance when incident on the first optical thin film at an incident angle of 30° to 60°, the first optical thin film has a range of incident angles in which the slope of a curve showing the incidence angle dependence of the transmittance of the second light for the first polarization of the first optical thin film is opposite to the slope of a curve showing the incidence angle dependence of the transmittance of the second light for the first polarization of the second optical thin film. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic diagram of a projector according to a first embodiment. [Figure 2] FIG. 2 is a front view of a light-transmitting member of the projector in FIG. [Figure 3]FIG. 2 is a schematic diagram of a dichroic mirror that is an optical element of the projector in FIG. [Figure 4] 4 is a graph showing the incidence angle dependency of the transmittance of the first optical thin film of the dichroic mirror of FIG. 3 for near-infrared light. [Figure 5] 4 is a graph showing the incidence angle dependency of the transmittance of the second optical thin film of the dichroic mirror of FIG. 3 for near-infrared light. [Figure 6] 4 is a graph showing the incidence angle dependency of the transmittance of the dichroic mirror of FIG. 3 for near-infrared light. [Figure 7] 10 is a graph showing the incidence angle dependency of the transmittance of the second optical thin film of the dichroic mirror of the comparative example for near-infrared light. [Figure 8] 10 is a graph showing the incidence angle dependency of the transmittance of a dichroic mirror of a comparative example for near-infrared light. [Figure 9] FIG. 10 is a schematic diagram of a projector according to a second embodiment. [Figure 10] FIG. 10 is a schematic diagram of a projector according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In each drawing, the scale of each component may be changed to make it easier to see each component.

[0009] [First embodiment] First, a first embodiment of the present invention will be described with reference to Fig. 1 to Fig. 8. Fig. 1 is a schematic diagram showing the configuration of a projector 11 according to the first embodiment of the present invention. The projector 11 is an optical device and image display device that includes three liquid crystal panels as a light modulation device, and is a so-called three-panel projector.

[0010] <Projector> As shown in FIG. 1, the projector 11 includes an illumination device 20, a light source device 150, a color separation optical system 200, field lenses 300R, 300G, and 300B, incident-side polarizing plates 410R, 410G, and 410B, light modulation devices 400R, 400G, and 400B, exit-side polarizing plates 420R, 420G, and 420B, a light-transmitting member 505, a cross dichroic prism 500, a projection optical system 600, an image sensor 710, a moving mechanism 720, and a control device 730.

[0011] The lighting device 20 includes a light source device 100, a first lens array 70, a second lens array 80, a polarization conversion element 92, and a superimposing lens 94. The lighting device 20 emits white light WL.

[0012] The light source device 100 emits white light WL. The detailed configuration of the light source device 100 is not limited to a specific configuration as long as it can emit white light WL. The light source device 100 may have, for example, an LED or laser diode (LD) that emits blue light, and a phosphor that is excited by a portion of the blue light emitted from the LED or LD and emits yellow light as fluorescence.

[0013] The white light WL emitted from the light source device 100 is collimated and enters the first lens array 70. The first lens array 70 has a plurality of small lenses 71 for dividing the white light WL emitted from the light source device 100 into a plurality of partial beams. The plurality of small lenses 71 are arranged in a matrix in a plane perpendicular to the optical axis AX20 of the light source device 100.

[0014] The second lens array 80 has a plurality of small lenses 81 corresponding to the plurality of small lenses 71 of the first lens array 70. The plurality of small lenses 81 are arranged in a matrix in a plane perpendicular to the optical axis AX20. The second lens array 80, together with the superimposing lens 94, forms an image of each small lens 71 of the first lens array 70 near the image forming area of ​​each of the light modulation devices 400R, 400G, and 400B.

[0015] The polarization conversion element 92 has a polarization separation layer, a reflective layer, and a retardation plate (not shown). The polarization conversion element 92 converts the partial light beams emitted from the second lens array 80 into linearly polarized light. The polarization conversion element 92 is formed in a plate shape as a whole. The plate surface of the polarization conversion element 92 is arranged parallel to a plane perpendicular to the optical axis AX20.

[0016] The polarization separation layer of the polarization conversion element 92 transmits one linearly polarized component of the polarization components contained in the partial light beams emitted from the second lens array 80, and reflects the other linearly polarized component in a direction perpendicular to the optical axis AX20. The reflective layer of the polarization conversion element 92 reflects the other linearly polarized component reflected by the polarization separation layer in a direction parallel to the optical axis AX20. The retardation plate of the polarization conversion element 92 converts the other linearly polarized component reflected by the reflective layer into one linearly polarized component.

[0017] The superimposing lens 94 collects the partial light beams from the polarization conversion element 92 and superimposes them near the image forming areas of the light modulation devices 400R, 400G, and 400B. The first lens array 70, the second lens array 80, and the superimposing lens 94 constitute an integrator optical system. The integrator optical system homogenizes the in-plane light intensity distribution of the white light WL emitted from the illumination device 20 in the image forming areas of the light modulation devices 400R, 400G, and 400B.

[0018] The color separation optical system 200 includes dichroic mirrors 210 and 220 and reflecting mirrors 230, 240, and 250. The dichroic mirror 220 corresponds to an optical element. The color separation optical system 200 separates the white light WL emitted from the illumination device 20 into red light RL, green light GL, and blue light BL, which are visible light, and guides each of the red light RL, green light GL, and blue light BL to the light modulation devices 400R, 400G, and 400B, respectively. Infrared light IL from the light source device 150 is incident on the dichroic mirror 220 of the color separation optical system 200.

[0019] The dichroic mirror 210 transmits the green light GL and blue light BL of the incident white light WL and reflects the red light RL. The dichroic mirror 220 transmits the blue light BL of the incident green light GL and blue light BL, reflects the green light GL, and transmits the incident infrared light IL. The configuration of the dichroic mirror 220 will be described later. The reflecting mirrors 230 and 240 reflect the incident blue light BL. The reflecting mirror 250 reflects the incident red light RL.

[0020] Field lenses 300R, 300G, and 300B are disposed on the optical paths of red light RL, green light GL, and blue light BL, respectively, between color separation optical system 200 and light modulation devices 400R, 400G, and 400B. Red light RL reflected by reflection mirror 250 passes through field lens 300R and enters the image formation area of ​​light modulation device 400R. Green light GL reflected by dichroic mirror 220 passes through field lens 300G and enters the image formation area of ​​light modulation device 400G. Blue light BL reflected by reflection mirror 240 passes through field lens 300B and enters the image formation area of ​​light modulation device 400B.

[0021] Relay lenses (not shown) may be arranged on the optical path of the blue light BL between the dichroic mirror 220 and the reflecting mirror 230, and on the optical path of the blue light BL between the reflecting mirrors 230 and 240. By providing the relay lenses, loss of the blue light BL, which has a longer optical path length than the green light GL and the red light RL, is reduced.

[0022] The light source device 150 includes a substrate 151, a plurality of light-emitting elements 152, and a homogenizing element 153. The substrate 151 is, for example, a plate-like member made of metal. The plurality of light-emitting elements 152 are arranged on a plate surface of the substrate 151 facing the dichroic mirror 220 of the color separation optical system 200. The light-emitting elements 152 emit infrared light IL. The wavelength of the infrared light IL is, for example, not less than 930 nm and not more than 950 nm, which is included in the near-infrared wavelength band. Note that the light source device 150 may include only one light-emitting element 152. The light-emitting element 152 is, for example, an LED that emits infrared light IL.

[0023] The homogenizing element 153 is disposed on the optical path of the infrared light IL emitted from the plurality of light-emitting elements 152, and is disposed on the optical path of the infrared light IL between the plurality of light-emitting elements 152 and the dichroic mirror 220. The homogenizing element 153 homogenizes the light intensity distribution of the infrared light IL emitted from the plurality of light-emitting elements 152 in a plane perpendicular to the optical axis AX150 of the infrared light IL. The homogenizing element 153 is, for example, a condenser lens including at least one convex lens, a holographic optical element (HOE) formed by a computer-generated hologram (CGH), or a diffractive optical element (DOE).

[0024] The incident-side polarizer 410R is disposed on the optical path of the red light RL between the field lens 300R and the optical modulation device 400R. The incident-side polarizer 410R transmits S-polarized light of the incident red light RL and reflects or absorbs P-polarized light of the red light RL. The incident-side polarizer 410G is disposed on the optical path of the green light GL between the dichroic mirrors 210 and 220, but outside the optical path of the infrared light IL. The incident-side polarizer 410G transmits S-polarized light of the incident green light GL and reflects or absorbs P-polarized light of the green light GL. The incident-side polarizer 410G is, for example, an inorganic polarizer. The incident-side polarizer 410B is disposed on the optical path of the blue light BL between the field lens 300B and the optical modulation device 400B. The incident-side polarizer 410B transmits S-polarized light of the incident blue light BL and reflects or absorbs P-polarized light of the blue light BL.

[0025] Each of the light modulation devices 400R, 400G, and 400B modulates the incident red light RL, green light GL, and blue light BL in accordance with image information to form image light. Each of the light modulation devices 400R, 400G, and 400B is configured, for example, with a liquid crystal panel. The operating mode of the liquid crystal panel may be any of TN mode, VA mode, lateral electric field mode, etc., and is not limited to a specific mode.

[0026] The exit-side polarizing plate 420R is disposed on the optical path of the red image light between the light modulation device 400R and the cross dichroic prism 500. The exit-side polarizing plate 420R transmits P-polarized light of the incident red image light and reflects or absorbs S-polarized light of the red image light. The exit-side polarizing plate 420G is disposed on the optical path of the green image light and infrared light IL between the light modulation device 400G and the cross dichroic prism 500. The exit-side polarizing plate 420G transmits P-polarized light of the incident green image light and infrared light IL and reflects or absorbs S-polarized light of the green image light and infrared light IL. The exit-side polarizing plate 420G is, for example, an organic polarizing plate. The exit-side polarizing plate 420B is disposed on the optical path of the blue image light between the light modulation device 400B and the cross dichroic prism 500. The exit-side polarizing plate 420B transmits P-polarized light of the incident blue image light and reflects or absorbs S-polarized light of the blue image light.

[0027] The light-transmitting member 505 is disposed on the optical path of the green light GL between the incident-side polarizing plate 410G and the light modulation device 400G.

[0028] FIG. 2 is a front view of the light-transmitting member 505, viewed along the direction in which the green light GL and the infrared light IL are incident. The light-transmitting member 505 has a shielding portion 511 and a transmitting portion 512. The shielding portion 511 blocks the infrared light IL by reflecting or absorbing it and transmits the green light GL. The transmitting portion 512 transmits both the infrared light IL and light in the visible wavelength band including the green light GL, i.e., visible light. The transmitting portions 512 are arranged in a predetermined pattern F. The predetermined pattern F of the transmitting portions 512 is, for example, a dotted pattern. The infrared light IL that passes through the light-transmitting member 505 and is emitted from the light-transmitting member 505 includes the dotted predetermined pattern F. The visible light that passes through the light-transmitting member 505 and is emitted from the light-transmitting member 505 is not blocked by the shielding portion 511 and does not include the predetermined pattern F.

[0029] As shown in Fig. 1, the cross dichroic prism 500 combines the image light emitted from each of the light modulation devices 400R, 400G, and 400B to generate color image light ML and emits a pattern of infrared light IL. As shown in Fig. 1, the cross dichroic prism 500 is formed in a generally cubic shape as a whole, with four right-angle prisms arranged so that their apexes overlap at a common center position in a plan view. A dichroic mirror made of a dielectric multilayer film or the like (not shown) is formed at the interface where the right-angle prisms in the cross dichroic prism 500 are bonded together.

[0030] The pattern of the image light ML and the infrared light IL emitted from the cross dichroic prism 500 is enlarged and projected onto the screen SCR by the projection optical system 600.

[0031] The imaging element 710 captures the pattern of infrared light IL projected by the projection optical system 600. The imaging element 710 is, for example, an imaging camera, and is disposed in any location in the projector 11 that does not block the light emitted from the projection optical system 600. The imaging element 710 is, for example, a near-infrared camera device. The infrared light IL preferably includes a wavelength band of 930 nm or more and 950 nm or less. By using infrared light with a wavelength of 930 nm or more and 950 nm or less, which has low energy in sunlight, it is possible to prevent the contrast of the infrared light IL pattern from decreasing due to the influence of sunlight when the infrared light IL is irradiated onto the screen SCR. As a result, the pattern of infrared light IL can be captured well by the imaging element 710.

[0032] The movement mechanism 720 receives an electrical signal from the control device 730, adjusts the position of the projection optical system 600 as appropriate, and changes the positions of the projected image and the infrared light IL pattern on the screen SCR.

[0033] The control device 730 controls the moving mechanism 720 and the light modulation devices 400R, 400G, and 400B in accordance with the image captured by the imaging element 710. The control device 730 changes the area where an image is formed in the image display area of ​​the light modulation device 400R corresponding to the red light RL in accordance with the image captured by the imaging element 710.

[0034] The control device 730 is configured, for example, by a computer or integrated circuit on which programs are recorded for the processes of the drive devices that drive the image sensor 710, the movement mechanism 720, the light source device 150, and the optical modulation devices 400R, 400G, and 400B. The control device 730 is, for example, a processor. The control device 730 is electrically connected to the drive circuits of the image sensor 710, the movement mechanism 720, the light source device 150, and the optical modulation devices 400R, 400G, and 400B via wires or wirelessly (not shown).

[0035] <Dichroic mirror (optical element)> Fig. 3 is a schematic diagram of the dichroic mirror 220. As shown in Fig. 3, the dichroic mirror 220 has a light-transmitting substrate 255 and optical thin films 251 and 252. The optical thin film 251 corresponds to the first optical thin film. The optical thin film 252 corresponds to the second optical thin film.

[0036] The light-transmitting substrate 255 is a base material of the dichroic mirror 220, and is a thin, plate-like member having plate surfaces 255a and 255b. The light-transmitting substrate 255 is formed of a material that transmits at least the green light GL and the infrared light IL, for example, optical glass or quartz. The plate surface 255a of the light-transmitting substrate 255 corresponds to the first surface, faces toward the field lens 300G, and is inclined at approximately 45° with respect to the incident surface of the light modulation device 400G. The plate surface 255b of the light-transmitting substrate 255 corresponds to the second surface, faces toward the reflecting mirror 230, and is approximately parallel to the reflecting surface of the reflecting mirror 230.

[0037] The optical thin film 251 is provided on a plate surface 255a of the light-transmitting substrate 255. The optical thin film 251 is provided as a reflective film of the dichroic mirror 220, and reflects green light GL in the green wavelength band of the visible wavelength band, and transmits near-infrared light NIL in the near-infrared wavelength band of the infrared wavelength band. The optical thin film 252 is provided on a plate surface 255b of the light-transmitting substrate 255. The optical thin film 252 is provided as an anti-reflection film of the dichroic mirror 220, and transmits light including red light RL in the visible wavelength band, and transmits near-infrared light NIL in the near-infrared wavelength band. The green wavelength band corresponds to the first wavelength band. The near-infrared wavelength band corresponds to the second wavelength band, for example, 920 nm to 960 nm. The green light GL corresponds to the first light. The near-infrared light NIL corresponds to the second light.

[0038] Green light GL incident on the dichroic mirror 220 is incident on the optical thin film 251 at an incident angle θ1 of approximately 45° and is reflected by the optical thin film 251. Blue light BL (not shown) incident on the dichroic mirror 220 from an optical path coaxial with the green light GL is incident on the optical thin film 251 at an incident angle θ1 of approximately 45° and is transmitted sequentially through the optical thin film 251, the light-transmitting substrate 255, and the optical thin film 252. Near-infrared light NIL incident on the dichroic mirror 220 from an optical path perpendicular to the green light GL is incident on the optical thin film 252 at an incident angle θ2 of approximately 45° and is transmitted sequentially through the optical thin film 252, the light-transmitting substrate 255, and the optical thin film 251.

[0039] Fig. 4 is a graph of the transmittance of the optical thin film 251 for near-infrared light NIL, and is a graph showing the dependency of the transmittance of near-infrared light NIL incident on the optical thin film 251 on the incident angle θ2. The transmittance on the vertical axis of each graph in Fig. 4 and Figs. 5 to 8, which will be referred to later, represents the average transmittance for near-infrared light NIL in the wavelength band of 920 nm to 960 nm. The average transmittance is calculated by (sum of transmittances at 1 nm intervals) / (number of plots), and the number of plots is 41.

[0040] 4, in the range of the incident angle θ2 from 30° to 60°, the maximum transmittance of the optical thin film 251 for S-polarized near-infrared light NIL is 99.6%, and the minimum transmittance of the optical thin film 251 for S-polarized near-infrared light NIL is 93.6%. The difference between the maximum and minimum transmittance of the optical thin film 251 for S-polarized near-infrared light NIL is 6.0%.

[0041] The transmittance of the optical thin film 251 for S-polarized near-infrared light NIL increases nonlinearly as the incident angle θ2 increases from 30° to around 40°, reaches a maximum when the incident angle θ2 is 40°, and decreases nonlinearly as the incident angle θ2 further increases from 40° to 60°. Furthermore, in the range of incident angles θ2 from 30° to 60°, the slope of the curve showing the incident angle dependence of the transmittance of the optical thin film 251 for S-polarized near-infrared light NIL is positive when the incident angle θ2 is from 30° to around 40°, and is negative when the incident angle θ2 is from around 40° to 60°. The slope of the curve showing the incident angle dependence of transmittance represents the slope of the tangent to the curve passing through the transmittance at each incident angle.

[0042] Similarly, within the range of the incident angle θ2 of 30° or more and 60° or less, the maximum transmittance of the optical thin film 251 for P-polarized near-infrared light NIL is 99.3%, and the minimum transmittance of the optical thin film 251 for P-polarized near-infrared light NIL is 97.8%. The difference between the maximum and minimum transmittance of the optical thin film 251 for P-polarized near-infrared light NIL is 1.5%, which is smaller than the difference between the maximum and minimum transmittance for S-polarized light. S-polarized light corresponds to the "first polarized light" described in the claims below.

[0043] The transmittance of the optical thin film 251 for S-polarized near-infrared light NIL increases nonlinearly as the incident angle θ2 increases from 30° to around 35°, reaches the highest transmittance when the incident angle θ2 is 35°, then decreases nonlinearly as the incident angle θ2 increases from 35° to around 50°, increases nonlinearly again as the incident angle θ2 increases from 50° to 57.5°, and decreases nonlinearly as the incident angle θ2 increases further from 57.5° to 60°.

[0044] 5 is a graph showing the transmittance of the optical thin film 252 for near-infrared light NIL, and is a graph showing the dependency of the transmittance of near-infrared light NIL incident on the optical thin film 252 on the incident angle θ2. As shown in FIG. 5, the transmittance of the optical thin film 252 for S-polarized near-infrared light NIL increases nonlinearly as the incident angle θ2 increases from 30° to approximately 55°, reaches a maximum transmittance of 99.0% when the incident angle θ2 is 55°, and decreases nonlinearly as the incident angle θ2 further increases from 55° to 60°. Furthermore, the slope of the curve showing the dependency of the transmittance of the optical thin film 252 for S-polarized near-infrared light NIL is positive over most of the range of incident angles θ2 from 30° to 60°, i.e., in the range of incident angles θ2 from 30° to 55°. In the range of the incident angle θ2 from approximately 55° to 60°, the slope of the curve showing the incident angle dependency of the transmittance of the optical thin film 252 for S-polarized near-infrared light NIL is negative.

[0045] On the other hand, within the range of the incident angle θ2 between 30° and 60°, the transmittance of the optical thin film 252 for P-polarized near-infrared light NIL increases nonlinearly as the incident angle θ2 increases from 30° to around 42.5°, reaching a maximum transmittance of 99.2% when the incident angle θ2 is 42.5°, and then decreases nonlinearly as the incident angle θ2 further increases from 42.5° to 60°.

[0046] In the dichroic mirror 220, the positive and negative slopes of the curves showing the incidence angle θ2 dependency of the transmittance of the optical thin film 251 for S-polarized near-infrared light NIL and the curves showing the incidence angle θ2 dependency of the transmittance of the optical thin film 252 for S-polarized near-infrared light NIL have mutually opposite incidence angle ranges. This means that the structure of the optical thin film 252 is designed so that the change in the transmittance of the optical thin film 252 for S-polarized near-infrared light NIL has an opposite trend to the change in the transmittance of the optical thin film 251 for S-polarized near-infrared light NIL within the incidence angle θ2 range of 30° to 60°, particularly within the incidence angle θ2 range of at least 30° to 55°.

[0047] Fig. 6 is a graph of the transmittance of the dichroic mirror 220 as a whole to near-infrared light NIL, and is a graph showing the dependence of the transmittance of the near-infrared light NIL on the incident angle θ2 of the composite film made up of the optical thin films 251 and 252. As shown in Fig. 6, the maximum transmittance of the dichroic mirror 220 as a whole to S-polarized near-infrared light NIL is 97.8%, and the minimum transmittance of the dichroic mirror 220 as a whole to S-polarized near-infrared light NIL is 92.4%. The difference between the maximum and minimum transmittance of the dichroic mirror 220 as a whole to S-polarized near-infrared light NIL is 5.4%.

[0048] A comparative example will be described with reference to Fig. 7. In the comparative example, unlike the present embodiment, polarization compensation is not performed so that the change in transmittance of the optical thin film 252 for S-polarized near-infrared light NIL has an opposite tendency to the change in transmittance of the optical thin film 251 for S-polarized near-infrared light NIL, at least within the range of the incident angle θ2 from 30° to 55°.

[0049] 7 is a graph of the transmittance of the optical thin film 252 for near-infrared light NIL as a comparative example. As shown in FIG. 7, in the comparative example, the transmittance of the optical thin film 252 for S-polarized near-infrared light NIL reaches a maximum of 99.6% when the incident angle θ2 is 30°, decreases nonlinearly as the incident angle θ2 increases from 30° to approximately 60°, and reaches a minimum of 96.3% when the incident angle θ2 is 60°. Furthermore, in the range of incident angles θ2 from 30° to 60°, the slope of the curve showing the incident angle dependency of the transmittance of the optical thin film 252 for S-polarized near-infrared light NIL is negative, and is the same as the slope of the curve showing the incident angle dependency of the transmittance of the optical thin film 251 for S-polarized near-infrared light NIL.

[0050] Fig. 8 is a graph of the transmittance of the entire dichroic mirror 220 as a comparative example for near-infrared light NIL. As shown in Fig. 8, the maximum transmittance of the entire dichroic mirror 220 as a comparative example for S-polarized near-infrared light NIL increases to 98.7%, but the minimum transmittance of the entire dichroic mirror 220 as a comparative example for S-polarized near-infrared light NIL decreases to 90.4%. The difference between the maximum and minimum transmittance of the entire dichroic mirror 220 as a comparative example for S-polarized near-infrared light NIL increases to 8.3%.

[0051] In the dichroic mirror 220 of this embodiment, the optical thin film 251 is composed of a dielectric multilayer film 261. The dielectric multilayer film 261 is a layered structure in which first high refractive index layers (not shown) and first low refractive index layers (not shown) having a lower refractive index than the first high refractive index layers are alternately stacked in the thickness direction. The material of the first high refractive index layers is, for example, tantalum pentoxide (Ta2O5). The material of the first low refractive index layers is, for example, silicon dioxide (SiO2). The difference in refractive index between Ta2O5 and SiO2 at the wavelength of 530 nm of the green light GL is 0.7.

[0052] The materials for the first high-refractive index layer and the first low-refractive index layer may be changed as needed as long as the difference in refractive index between the first high-refractive index layer and the first low-refractive index layer is appropriate. Preferably, the materials include oxide, nitride, or fluoride. When the material for the first high-refractive index layer or the material for the first low-refractive index layer includes an oxide, absorption of green light GL, blue light BL, and near-infrared light NIL is suppressed in the visible to near-infrared wavelength range, e.g., in the range of 200 nm to 1000 nm. Therefore, even if the number of first high-refractive index layers and first low-refractive index layers is increased, deterioration in reliability of the dielectric multilayer film 261 and the optical thin film 251 and increase in manufacturing costs are suppressed.

[0053] When the material of the first high-refractive index layer or the material of the first low-refractive index layer contains a nitride, the hardness of the first high-refractive index layer and the first low-refractive index layer is ensured, and a decrease in reliability of the dielectric multilayer film 261 and the optical thin film 251 and damage due to aging or external impact are suppressed. When the material of the first high-refractive index layer or the material of the first low-refractive index layer contains a fluoride, absorption of green light GL, blue light BL, and near-infrared light NIL is suppressed over an even wider wavelength band than when an oxide is used. Therefore, even if the number of first high-refractive index layers and first low-refractive index layers is increased, a decrease in reliability of the dielectric multilayer film 261 and the optical thin film 251 and an increase in manufacturing costs are further suppressed.

[0054] The number of first high-refractive index layers, the number of first low-refractive index layers, and the difference in refractive index between the first high-refractive index layers and the first low-refractive index layers in the dielectric multilayer film 261 are determined in accordance with the incidence angle θ1 dependency of the transmittance of the optical thin film 251 for at least S-polarized green light GL, specifically, so that the reflectance of the S-polarized green light GL incident on the optical thin film 251 is high at an incidence angle θ1 of 45°, and the transmittance of the S-polarized blue light BL incident on the optical thin film 251 is high at an incidence angle θ1 of 45°. Table 1 shows design examples of the first high-refractive index layers and first low-refractive index layers of the dielectric multilayer film 261.

[0055] [Table 1]

[0056] The layer numbers in Table 1 refer to the numbers when counting each layer from the side closer to plate surface 255a of light-transmitting substrate 255. The thicknesses in Table 1 represent the thickness of each layer in the direction perpendicular to plate surface 255a.

[0057] In the dichroic mirror 220 of this embodiment, the optical thin film 251 is preferably a color separation filter.

[0058] In the dichroic mirror 220 of this embodiment, the optical thin film 252 is composed of a dielectric multilayer film 262. The dielectric multilayer film 262 is a layered structure in which second high refractive index layers (not shown) and second low refractive index layers (not shown) having a lower refractive index than the second high refractive index layers are alternately stacked in the thickness direction. The material of the second high refractive index layers is, like the first high refractive index layers, tantalum pentoxide (Ta2O5), for example. The material of the second low refractive index layers is, like the second low refractive index layers, silicon dioxide (SiO2), for example. The difference in refractive index between Ta2O5 and SiO2 at a wavelength of 940 nm of near-infrared light NIL is 0.65.

[0059] The material of the second high refractive index layer and the material of the second low refractive index layer may be changed as appropriate as long as the refractive index difference between the second high refractive index layer and the second low refractive index layer is appropriate, and for the same reasons as those for the material of the first high refractive index layer and the material of the first low refractive index layer, it is preferable that they include any of oxide, nitride, and fluoride.

[0060] As described above, the number of second high-refractive-index layers, the number of second low-refractive-index layers, and the difference in refractive index between the second high-refractive-index layers and the second low-refractive-index layers in the dielectric multilayer film 262 are determined in accordance with the incidence angle θ1 dependence of the transmittance of at least S-polarized light of the green light GL of the optical thin film 251. Specifically, the above-mentioned parameters of the dielectric multilayer film 262 are set so that the positive and negative slopes of the curve showing the incidence angle θ2 dependence of the transmittance of the dielectric multilayer film 262 constituting the optical thin film 252 for S-polarized light of the near-infrared light NIL are opposite to the positive and negative slopes of the curve showing the incidence angle θ2 dependence of the transmittance of the dielectric multilayer film 261 constituting the optical thin film 251 for S-polarized light of the near-infrared light NIL, and so that the incidence angle θ2 dependence of the transmittance of the dielectric multilayer film 261 for S-polarized light of the near-infrared light NIL is compensated for by the incidence angle θ2 dependence of the transmittance of the dielectric multilayer film 262 for S-polarized light of the near-infrared light NIL. Table 2 shows design examples of the second high refractive index layer and the second low refractive index layer of the dielectric multilayer film 262.

[0061] [Table 2]

[0062] The layer numbers in Table 2 refer to the numbers when counting each layer from the side closer to plate surface 255b of light-transmitting substrate 255. The thicknesses in Table 2 represent the thicknesses of each layer in the direction perpendicular to plate surface 255b.

[0063] As described above, the dichroic mirror (optical element) 220 of the first embodiment includes a light-transmitting substrate 255, an optical thin film (first optical thin film) 251, and an optical thin film (second optical thin film) 252. The light-transmitting substrate 255 has a plate surface (first surface) 255a and a plate surface (second surface) 255b opposite the plate surface 255a. The optical thin film 251 is provided on the plate surface 255a of the light-transmitting substrate 255 and reflects green light (first light) in a green wavelength band (first wavelength band) of the visible wavelength band and transmits near-infrared light NIL, which is infrared light. The optical thin film 252 is provided on the plate surface 255b of the light-transmitting substrate 255 and transmits near-infrared light (second light) NIL in a near-infrared wavelength band (second wavelength band) of the infrared wavelength band and transmits light in the visible wavelength band. In the dichroic mirror 220 of the first embodiment, the transmittance of the optical thin film 251 for near-infrared light (infrared light) NIL incident at an incident angle θ2 of 30° or more and 60° or less is 90% or more. In the dichroic mirror 220 of the first embodiment, of the S-polarized and P-polarized near-infrared light NIL, the polarization that has a larger difference between the maximum transmittance and the minimum transmittance when it is incident on the optical thin film 251 at an incident angle θ2 of 30° or more and 60° or less is, for example, S-polarized light (first polarization). In the dichroic mirror 220 of the first embodiment, the slope of the curve showing the incident angle dependency of the transmittance of the optical thin film 251 for S-polarized near-infrared light NIL is negative when the incident angle θ2 is between approximately 40° and approximately 55°. The slope of the curve showing the incidence angle dependence of the transmittance of the optical thin film 252 for S-polarized near-infrared light NIL is positive from around 30° to around 55°, and is in the opposite relationship to the slope of the curve showing the incidence angle dependence of the transmittance of the optical thin film 251 for S-polarized near-infrared light NIL. The dichroic mirror 220 of the first embodiment has a range of incidence angles θ2 in which the slope of the curve showing the incidence angle dependence of the transmittance of the optical thin film 251 for S-polarized near-infrared light NIL and the slope of the curve showing the incidence angle dependence of the transmittance of the optical thin film 252 for S-polarized near-infrared light NIL are mutually opposite. This range is, for example, 40° to 55°, including 45°.

[0064] As described above, in the dichroic mirror 220 of the first embodiment, the positive and negative slopes of the curve showing the incidence angle dependency of the transmittance of the optical thin film 251 for S-polarized near-infrared light NIL have a range of incidence angles inversely related to the positive and negative slopes of the curve showing the incidence angle dependency of the transmittance of the optical thin film 252 for S-polarized near-infrared light NIL, and polarization compensation is performed on the optical thin film 252. The dichroic mirror 220 of the first embodiment suppresses the amount of change in the light intensity of the S-polarized near-infrared light NIL emitted from the dichroic mirror 220 due to the incidence angle θ2 dependency, thereby reducing differences in light intensity in the polarization direction of the near-infrared light NIL and differences in the polarization characteristics of the near-infrared light NIL. As a result, uneven illuminance of the optical pattern of the near-infrared light NIL projected onto the screen SCR can be reduced.

[0065] In the dichroic mirror 220 of the first embodiment, the optical thin film 251 transmits blue light (third light) BL in a blue wavelength band (third wavelength band) that is different from the green wavelength band in the visible wavelength band. The optical thin film 252 transmits the blue light BL.

[0066] According to the dichroic mirror 220 of the first embodiment, the directions of travel of the incident green light GL and blue light BL can be separated, and the incident near-infrared light NIL can be emitted onto an optical path coaxial with the green light GL, thereby combining the green light GL and the near-infrared light NIL.

[0067] In the dichroic mirror 220 of the first embodiment, the optical thin film 251 is composed of a dielectric multilayer film (first dielectric multilayer film) 261 in which first high refractive index layers and first low refractive index layers are alternately stacked. The optical thin film 252 is composed of a dielectric multilayer film (second dielectric multilayer film) 262 in which second high refractive index layers and second low refractive index layers are alternately stacked.

[0068] The dielectric multilayer film has low absorption of color light, and the controllability and design freedom of the dielectric multilayer film are higher than those of other optical thin films. According to the dichroic mirror 220 of the first embodiment, it is possible to minimize the decrease in efficiency of the green light GL and the near-infrared light NIL, while reducing the difference in light intensity in the polarization direction of the near-infrared light NIL, i.e., the difference in light intensity between S-polarized and P-polarized light of the near-infrared light NIL, and the difference in polarization characteristics including the dependence on the incident angle θ2 of the near-infrared light NIL.

[0069] In the dichroic mirror 220 of the first embodiment, the number of first high-refractive-index layers, the number of first low-refractive-index layers, and the difference in refractive index between the first high-refractive-index layers and the first low-refractive-index layers of the dielectric multilayer film 261 are determined in accordance with the incidence angle dependency of the transmittance of the optical thin film 251 for S-polarized green light GL. In the dichroic mirror 220 of the first embodiment, the number of second high-refractive-index layers, the number of second low-refractive-index layers, and the difference in refractive index between the second high-refractive-index layers and the second low-refractive-index layers of the dielectric multilayer film 262 are determined in accordance with the positive or negative slope of the curve that indicates the incidence angle dependency of the transmittance of the optical thin film 251 for S-polarized near-infrared light NIL.

[0070] According to the dichroic mirror 220 of the first embodiment, it is possible to easily reduce the difference in light intensity in the polarization direction of the near-infrared light NIL and the difference in polarization characteristics including the dependence of the near-infrared light NIL on the incident angle θ2 while minimizing the decrease in efficiency of the green light GL and the near-infrared light NIL.

[0071] In the dichroic mirror 220 of the first embodiment, the dielectric multilayer films 261 and 262 contain any of an oxide, a nitride, and a fluoride.

[0072] According to the dichroic mirror 220 of the first embodiment, it is possible to suppress the occurrence of absorption or loss of the green light GL and the near-infrared light NIL in the optical thin films 251 and 252, or the deterioration of the optical thin films 251 and 252, etc.

[0073] In the dichroic mirror 220 of the first embodiment, the second wavelength band is the near-infrared wavelength band.

[0074] According to the dichroic mirror 220 of the first embodiment, the target wavelength range is the near-infrared wavelength range, which is longer than the visible wavelength range, thereby widening the range of choices for materials for the refractive index layers of the optical thin films 251, 252 and the dielectric multilayer films 261, 262, and facilitating manufacturing. Furthermore, according to the dichroic mirror 220 of the first embodiment, the second wavelength range is adjacent to and close to the first wavelength range, thereby reducing the effects on the amount of transmitted light and reflected light of each color light in the optical elements arranged on the optical paths of the green light GL, the blue light BL, and the near-infrared light NIL, including the translucent substrate 255, and on the amount of light of each color light emitted from the optical elements.

[0075] In the dichroic mirror 220 of the first embodiment, the transmittance of the optical thin film 252 for S-polarized light (at least one of the polarized lights) of the S-polarized light and P-polarized light of the near-infrared light NIL increases as the incident angle θ2 of the S-polarized light increases.

[0076] According to the dichroic mirror 220 of the first embodiment, it is possible to suppress a decrease in efficiency of colored light in the projector 11 and other optical devices that include the dichroic mirror 220.

[0077] In the dichroic mirror 220 of the first embodiment, the first wavelength band is a green wavelength band and the third wavelength band is a blue wavelength band. The dichroic mirror 220 separates the incident green light GL and blue light BL into different optical paths.

[0078] The projector (optical device) 11 of the first embodiment includes the above-described dichroic mirror 220. In the projector 11 of the first embodiment, it is preferable that the near-infrared light NIL is incident on the optical thin film 252 so that the intensity of the S-polarized light and the intensity of the P-polarized light of the near-infrared light NIL emitted from the optical thin film 252 are approximately equal.

[0079] The projector 11 of the first embodiment reduces the difference in polarization characteristics between the green light and the near-infrared light NIL emitted from the dichroic mirror 220. The projector 11 of the first embodiment can prevent illuminance unevenness from becoming apparent in the image enlarged and projected onto the screen SCR and in the optical pattern of the near-infrared light NIL.

[0080] In the projector 11 of the first embodiment, the angle of incidence θ1 of the green light GL and the angle of incidence θ2 of the near-infrared light NIL that are incident on the dichroic mirror 220 are 45°. Note that the angle of incidence θ1 represents the angle that the green light GL makes with respect to the normal to the plate surface 255a of the light-transmitting substrate 255 when it is incident on the optical thin film 251 of the dichroic mirror 220. The angle of incidence θ2 represents the angle that the near-infrared light NIL makes with respect to the normal to the plate surface 255b of the light-transmitting substrate 255 when it is incident on the optical thin films 251 and 252 of the dichroic mirror 220.

[0081] According to the projector 11 of the first embodiment, the arrangement of the components of the color separation optical system 200 is simplified, making it easy to design.

[0082] In the projector 11 of the first embodiment, the near-infrared light NIL emitted from the light emitting element 152 of the light source device 150 is randomly polarized light.

[0083] According to the projector 11 of the first embodiment, an LED can be used as the light emitting element 152, and it is possible to achieve miniaturization and cost reduction.

[0084] In the projector 11 of the first embodiment, the green light GL may be linearly polarized light that is incident as S-polarized light on the optical thin film 251 of the dichroic mirror 220. In that case, when reflected by the optical thin film 251 in the dichroic mirror 220, the intensity of the S-polarized light can be obtained compared to the P-polarized light of the green light GL.

[0085] The projector 11 of the first embodiment further includes a light modulation device 400G. Green light (light) GL and near-infrared light (light) NIL emitted from the dichroic mirror 220 are incident on the light modulation device 400G. The light modulation device 400G modulates the green light GL in the visible wavelength band out of the incident green light GL and near-infrared light NIL in accordance with image information, and converts it into image light.

[0086] According to the projector 11 of the first embodiment, it is possible to obtain green image light generated by the light modulation device 400G and a pattern of near-infrared light NIL generated by the translucent member 505 or the like without being modulated by the light modulation device 400G.

[0087] [Second embodiment] Next, a second embodiment of the present invention will be described with reference to Fig. 9. In the second and third embodiments, components common to the first embodiment are denoted by the same reference numerals as the corresponding components of the first embodiment, and descriptions that overlap with the first embodiment will be omitted. In the second and third embodiments, components and contents different from the first embodiment will be described.

[0088] FIG. 9 is a schematic diagram showing the configuration of a projector 12 of a second embodiment. As shown in FIG. 9, the projector 12 of the second embodiment has the same components as the projector 11 of the first embodiment. However, the projector 12 of the second embodiment has a dichroic mirror 222 that reflects incident green light GL and transmits incident blue light BL instead of the dichroic mirror 220 in the projector 11 of the first embodiment. Also, the dichroic mirror 220 is arranged instead of the reflection mirror 250. The incident-side polarizing plate 410R is moved onto the optical path of the red light RL between the dichroic mirrors 210 and 220. A translucent member 505 is arranged on the optical path of the red light RL between the field lens 300R and the light modulation device 400R.

[0089] In the projector 12 of the second embodiment, the dichroic mirror 220 reflects incident red light RL and transmits incident infrared light IL. In the projector 12 of the second embodiment, the green light GL can be replaced with red light RL in the description of the configuration of the dichroic mirror 220. In the projector 12 of the second embodiment, the same effects as those of the dichroic mirror 220 and the projector 11 of the first embodiment can be obtained with respect to the configuration in common.

[0090] [Third embodiment] Next, a second embodiment of the present invention will be described with reference to FIG.

[0091] FIG. 10 is a schematic diagram showing the configuration of a projector 13 of a third embodiment. As shown in FIG. 10, the projector 13 of the third embodiment has the same components as the projector 11 of the first embodiment. However, the projector 12 of the third embodiment has a dichroic mirror 222 that reflects incident green light GL and transmits incident blue light BL instead of the dichroic mirror 220 in the projector 11 of the first embodiment. Furthermore, a dichroic mirror 220 is provided instead of the reflecting mirror 240, and is reversed left to right on the page. An incident-side polarizing plate 410B is moved onto the optical path of the blue light BL between the reflecting mirror 230 and the dichroic mirror 220. A translucent member 505 is provided on the optical path of the blue light BL between the field lens 300B and the light modulation device 400B.

[0092] In the projector 13 of the third embodiment, the dichroic mirror 220 reflects incident blue light BL and transmits incident infrared light IL. In the projector 13 of the third embodiment, in the description of the configuration of the dichroic mirror 220, green light GL can be replaced with blue light BL. In the projector 13 of the third embodiment, the same effects can be obtained from the configuration common to the dichroic mirror 220 and projector 11 of the first embodiment.

[0093] Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and changes are possible within the scope of the gist of the present invention as set forth in the claims.

[0094] For example, in the above description, a projector is used as an example of an optical device, but the optical device to which the present invention is applied is not limited to a projector. The optical device to which the present invention is applied may be, for example, a head-mounted display device, a printer, or other output device.

[0095] Summary of this disclosure A summary of this disclosure is provided below. (Appendix 1) An optical element comprising: a light-transmitting substrate having a first surface and a second surface opposite to the first surface; a first optical thin film provided on the first surface, the first optical thin film reflecting first light in a first wavelength band within a visible wavelength band and transmitting infrared light in an infrared wavelength band; and a second optical thin film provided on the second surface, the second optical thin film transmitting second light in a second wavelength band within the infrared wavelength band, wherein the transmittance of the first optical thin film for the infrared light incident at an incident angle of 30° to 60° is 90% or more, and the first polarized light is S-polarized light or P-polarized light of the second light, which has a larger difference between the maximum transmittance and the minimum transmittance when incident on the first optical thin film at an incident angle of 30° to 60°, and the optical element has an incident angle range in which the positive and negative slopes of the curves showing the incident angle dependence of the transmittance of the first optical thin film for the first polarized light are opposite to each other.

[0096] The configuration of Supplementary Note 1 can reduce the difference in light intensity between the S-polarized light and the P-polarized light of the second light in the infrared wavelength band emitted from the optical element.

[0097] (Appendix 2) The optical element of Appendix 1, wherein the first optical thin film transmits third light in a third wavelength band different from the first wavelength band within the visible wavelength band, and the second optical thin film transmits the third light.

[0098] The configuration of Supplementary Note 2 separates the traveling direction and optical path of the first light from the traveling direction and optical path of the third light, and superimposes the second light on an optical path coaxial with the first light, thereby combining the first light and the second light.

[0099] (Appendix 3) The optical element of appendix 1 or appendix 2, wherein the first optical thin film is composed of a first dielectric multilayer film formed by alternately stacking first high-refractive index layers and first low-refractive index layers, and the second optical thin film is composed of a second dielectric multilayer film formed by alternately stacking second high-refractive index layers and second low-refractive index layers.

[0100] The configuration of Supplementary Note 3 can suppress absorption and loss of the first light and the second light in the optical element, and prevent a decrease in the efficiency of the first light and the second light.

[0101] (Appendix 4) The optical element of Appendix 3, wherein the number of the first high-refractive-index layers, the number of the first low-refractive-index layers, and the difference in refractive index between the first high-refractive-index layers and the first low-refractive-index layers are determined in accordance with the incidence angle dependency of the transmittance of the first optical thin film for the first polarization of the first light, and the number of the second high-refractive-index layers, the number of the second low-refractive-index layers, and the difference in refractive index between the second high-refractive-index layers and the second low-refractive-index layers are determined in accordance with the positive or negative slope of a curve showing the incidence angle dependency of the transmittance of the first optical thin film for the first polarization of the second light.

[0102] The configuration of Supplementary Note 4 prevents a decrease in the efficiency of the first light and the second light, improves the reliability of the optical element, and allows the optical element to be easily designed and manufactured.

[0103] (Supplementary Note 5) The optical element according to Supplementary Note 3, wherein the first dielectric multilayer film and the second dielectric multilayer film contain any of oxide, nitride, and fluoride.

[0104] The configuration of Supplementary Note 5 improves the reliability and durability of the first optical thin film and the second optical thin film, and provides excellent optical properties.

[0105] (Supplementary Note 6) The optical element according to any one of Supplementary Notes 1 to 5, wherein the second wavelength band is a near-infrared wavelength band.

[0106] The configuration of Supplementary Note 6 allows for a wider range of choices for materials for the first optical thin film and the second optical thin film, making it possible to easily manufacture optical elements. Furthermore, the configuration of Supplementary Note 6 makes it possible to reduce the wavelength difference between the near-infrared wavelength band and the first wavelength band, thereby suppressing the influence on the transmittance of each light and the amount of emitted light in optical elements on the optical paths of the first light and the second light.

[0107] (Appendix 7) The optical element according to any one of Appendices 1 to 6, wherein the transmittance of the second optical thin film for at least one of S-polarized and P-polarized light of the second light increases as the incident angle of the at least one polarized light increases.

[0108] The configuration of Supplementary Note 7 can suppress a decrease in the efficiency of the first light and the second light in the optical element.

[0109] (Supplementary Note 8) The optical element according to any one of Supplementary Notes 1 to 7, wherein the first wavelength band is a green wavelength band, and the third wavelength band is a blue wavelength band.

[0110] The configuration of Supplementary Note 8 makes it possible to easily separate the green light in the green wavelength band and the blue light in the blue wavelength band onto different optical paths.

[0111] (Appendix 9) An optical device comprising the optical element according to claim 1 or claim 2, wherein the second light is incident on the second optical thin film so that the intensity of the S-polarized light of the second light emitted from the second optical thin film is approximately equal to the intensity of the P-polarized light of the second light.

[0112] The configuration of Supplementary Note 8 can suppress differences in the polarization characteristics of the irradiated light emitted from the optical device, thereby reducing uneven illuminance.

[0113] (Appendix 10) The optical device of Appendix 9, wherein the incident angle of the first light and the second light is 45°.

[0114] The configuration of Supplementary Note 10 can simplify the arrangement of the components of the optical device.

[0115] (Appendix 11) The optical device of appendix 9 or appendix 10, wherein the second light is randomly polarized.

[0116] According to the configuration of Supplementary Note 11, an LED is used as a light emitting element of the light source device that emits the second light, thereby achieving miniaturization and cost reduction.

[0117] (Supplementary Note 12) The optical device according to Supplementary Note 9 or Supplementary Note 10, wherein the first light is linearly polarized light incident on the first optical thin film as S-polarized light.

[0118] The configuration of Supplementary Note 12 allows the first light to be efficiently emitted to the rear stage of the optical element, thereby increasing the utilization efficiency of the first light.

[0119] (Appendix 13) The optical device according to any one of appendices 9 to 12, further comprising a light modulation device into which light emitted from the optical element is incident and which modulates light in the visible wavelength band of the incident light in accordance with image information.

[0120] With the configuration of Supplementary Note 13, the first light emitted from the optical element can be modulated into image light and enlarged and projected, and the second light can be enlarged and projected in a predetermined pattern without being modulated by the light modulation device.

[0121] (Appendix 14) A projector comprising an optical element according to any one of appendices 1 to 8.

[0122] The configuration of Supplementary Note 14 can suppress the difference in polarization characteristics between the image light including the first light emitted from the optical element and the second light, thereby reducing unevenness in illuminance of the projected image and the pattern of the second light.

[0123] (Appendix 15) A projector equipped with any one of the optical devices of Appendices 9 to 13.

[0124] The configuration of Supplementary Note 15 can suppress the difference in polarization characteristics between the image light including the first light emitted from the optical element and the second light, thereby reducing unevenness in illuminance of the projected image and the pattern of the second light. [Explanation of symbols]

[0125] 11...Projector (optical device), 250...Light-transmitting substrate, 251...Optical thin film (first optical thin film), 252...Optical thin film (second optical thin film).

Claims

1. a light-transmitting substrate having a first surface and a second surface opposite to the first surface; a first optical thin film provided on the first surface, the first optical thin film reflecting first light in a first wavelength band of a visible wavelength band and transmitting infrared light in an infrared wavelength band; a second optical thin film provided on the second surface and transmitting second light in a second wavelength band within the infrared wavelength band; Equipped with the transmittance of the first optical thin film for the infrared light incident at an incident angle of 30° or more and 60° or less is 90% or more; When the first polarization is defined as the S-polarized light or the P-polarized light of the second light, the first polarization is the polarization having a larger difference between the maximum transmittance and the minimum transmittance when the second light is incident on the first optical thin film at an incident angle of 30° or more and 60° or less, the first optical thin film has an incident angle range in which the positive and negative slopes of the curves showing the incident angle dependency of the transmittance of the second light for the first polarized light of the first optical thin film and the second optical thin film have mutually opposite positive and negative slopes. Optical elements.

2. the first optical thin film transmits third light in a third wavelength band different from the first wavelength band within a visible wavelength band; the second optical thin film transmits the third light; The optical element according to claim 1 .

3. the first optical thin film is composed of a first dielectric multilayer film in which first high refractive index layers and first low refractive index layers are alternately stacked, the second optical thin film is composed of a second dielectric multilayer film in which second high refractive index layers and second low refractive index layers are alternately stacked; 3. The optical element according to claim 1.

4. the number of the first high-refractive-index layers, the number of the first low-refractive-index layers, and a difference in refractive index between the first high-refractive-index layers and the first low-refractive-index layers are determined in accordance with the incidence angle dependency of the transmittance of the first optical thin film with respect to a first polarization of the first light, the number of the second high-refractive-index layers, the number of the second low-refractive-index layers, and the difference in refractive index between the second high-refractive-index layers and the second low-refractive-index layers are determined depending on whether the slope of a curve indicating the incidence angle dependency of the transmittance of the first optical thin film with respect to the first polarization of the second light is positive or negative. The optical element according to claim 3 .

5. the first dielectric multilayer film and the second dielectric multilayer film contain any one of an oxide, a nitride, and a fluoride; The optical element according to claim 3 .

6. the second wavelength band is a near-infrared wavelength band; 3. The optical element according to claim 1.

7. the transmittance of the second optical thin film for at least one of S-polarized light and P-polarized light of the second light increases as the incident angle of at least one of the S-polarized light and P-polarized light increases; 3. The optical element according to claim 1.

8. the first wavelength band is a green wavelength band; the third wavelength band is a blue wavelength band; The optical element according to claim 2 .

9. The optical element according to claim 1 or 2, the second light is incident on the second optical thin film such that the intensity of S-polarized light of the second light emitted from the second optical thin film and the intensity of P-polarized light of the second light are substantially equal to each other; optical equipment.

10. the incident angle of the first light and the second light is 45°; 10. The optical instrument of claim 9.

11. the second light is randomly polarized; 10. The optical instrument according to claim 9.

12. the first light is linearly polarized light incident on the first optical thin film as S-polarized light; 10. The optical instrument according to claim 9.

13. The optical element further includes a light modulation device that receives the light emitted from the optical element and modulates light in a visible wavelength range among the incident light in accordance with image information.

10. The optical instrument according to claim 9.

14. The optical element according to claim 1 or 2 is provided. projector.

15. 10. An optical instrument comprising: an optical instrument according to claim 9; projector.

Images