Optical device and display device

Abstract

To provide an optical device using an angle selection type transmission element in which a decrease in vignetting or numerical aperture is suppressed and eyepiece observation and sight line detection are enabled while reducing ghosts due to light from behind a user.SOLUTION: A head mounted display (HMD) 1 having a sight line detection function comprises angle selection type transmission elements 6, 7 arranged in finder optical paths for user's eyes, respectively, and a light projection and a light reception unit for sight line detection, with the direction of the finder being adjustable to the detected sight line direction. The angle selection type transmission elements 6, 7 have a first to a third opening, the respective directions of which are different. The first and the second openings respectively limit light passage directions in first and second regions in the finder paths. The third opening is formed centering around a line linking an eyepoint and the light receiving element.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a ghost reduction technique for head mounted displays, binoculars, camera viewfinders, and the like, and more particularly to an optical device and a display device that include an angle-selection type transmission element. [Background technology]

[0002] When a user uses a head mounted display or a camera viewfinder outdoors, there is a possibility that ghost images may be generated by light coming from behind the user. Patent Document 1 discloses a technology that blocks light that causes ghost images by placing a louver film on the eye side of the display unit.

[0003] Furthermore, cameras with a gaze detection function that realizes functions such as distance measurement point selection by detecting the direction of the user's gaze have been put to practical use (Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 5-215908 [Patent Document 2] Patent No. 3186072 Summary of the Invention [Problem to be solved by the invention]

[0005] With conventional technology, problems such as vignetting due to the narrow eye box and reduced aperture ratio are a problem. Also, measures are needed to prevent vignetting of the light from the infrared light source (LED) directed from the eye point to the gaze detection sensor. An object of the present invention is to enable ocular observation and line of sight detection while suppressing vignetting and a decrease in aperture ratio and reducing ghosts caused by light from behind the user in an optical device using an angle-selective transmission element. [Means for solving the problem]

[0006] An apparatus according to one embodiment of the present invention is an optical device equipped with a viewfinder, comprising: an angle-selective transmission element arranged in the optical path of the viewfinder; a detection means for detecting the line of sight using light passing through the angle-selective transmission element; and a mechanism capable of adjusting the direction of the viewfinder to the line of sight direction detected by the detection means. Effect of the Invention

[0007] According to the present invention, in an optical device using an angle-selective transmission element, vignetting and a decrease in the aperture ratio are suppressed, and ghosts caused by light from behind the user are reduced, making it possible to perform ocular observation and line of sight detection. [Brief description of the drawings]

[0008] [Figure 1] 1 is an external view of a display device (head mounted display) to which the present invention is applied. [Diagram 2] FIG. 2 is a diagram showing a state in which a user wears the display device on his / her head. [Diagram 3] 3 is a diagram showing a state in which the display unit is flipped up from the state shown in FIG. 2. FIG. [Figure 4] FIG. 2 is a cross-sectional view showing a configuration of the display device when in use. [Diagram 5] FIG. 3 is a cross-sectional view taken along line AA in FIG. [Figure 6] 1 is a cross-sectional view showing the relationship between a user's head and eyeballs and a display device. [Figure 7] FIG. 7 is a detailed view showing part B in FIG. 6. [Figure 8] 2 is a diagram showing a first surface side of an angle-selective transmission element. FIG. [Figure 9] FIG. 9 is a cross-sectional view taken along line CC in FIG. [Figure 10] FIG. 4 is a diagram showing optical paths when detecting a line of sight. [Figure 11] FIG. 4 is a cross-sectional view showing a configuration during gaze detection. [Figure 12] 4 is a schematic diagram of an eyeball image during gaze detection; FIG. [Figure 13]13 is a diagram showing a first surface side of an angle-selective transmission element according to a second embodiment. FIG. [Figure 14] FIG. 14 is a cross-sectional view taken along line DD in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. A head mounted display (hereinafter, referred to as HMD) is shown as an example of a display device that uses an angle-selective transmission element arranged in the optical path of a viewfinder, etc. Note that the present invention is not limited to HMDs and can be applied to various optical devices.

[0010] [First Example] An electronic viewfinder (hereinafter, referred to as EVF) with a gaze detection function according to this embodiment will be described with reference to Fig. 1 to Fig. 12. Fig. 1 is an external view showing an example of the configuration of an HMD 1. The HMD 1 comprises a main body 2, EVFs 3 and 4, and a head-mounted unit 5. The pair of EVFs is made up of an EVF 3 for the left eye and an EVF 4 for the right eye, which correspond to both eyes of the user.

[0011] The main body 2 and head mounted unit 5 of the HMD 1 are rotatable by a hinge 2a on the main body 2 side and a hinge 5a on the head mounted unit 5 side, and are joined in a state in which the distance between the main body 2 and the user's eyes (FIG. 5: distance E1 between eye point 13 and eye side surface 6a) can be adjusted. The left eye EVF 3 and right eye EVF 4 are held relative to the main body 2 in a state in which the interpupillary distance can be adjusted.

[0012] Figures 2 and 3 show a state in which a user wears the HMD 1 on his / her head. Figure 2 shows a state in which the user is looking at the display screen, and Figure 3 shows a state in which the main body 2 of the HMD 1 is flipped up so that the user can see the surroundings.

[0013] Angle-selective transmission elements 6 and 7 are attached to the portions where the user looks into the EVF 3 and EVF 4, respectively. In this embodiment, the angle-selective transmission element 6 and the angle-selective transmission element 7 have the same configuration, but by making the configurations of both elements different, it is possible to optimize the convergence angle between the right and left eyes and the ghost cutting characteristics. In the following, the side of the angle-selective transmission elements 6 and 7 that is on the side facing the optical axis of the viewfinder is defined as the inside, and the side that is away from the optical axis of the viewfinder is defined as the outside.

[0014] FIG. 4 is a cross-sectional view showing the configuration of the main body 2 and the EVF 3 when the HMD 1 is in use, showing the portion corresponding to the left eye of the user. The display unit 9 and the eyepiece lens system 10 are provided inside the exterior member 11 of the EVF 3. The display unit 9 has an organic EL (Electro-Luminescence) display panel. The surface of the eyepiece lens system 10 facing the angle-selective transmission element 6 is a curved surface. The angle-selective transmission element 6 is disposed in a position facing the left eye of the user on the exterior member 11. The first surface 6a of the angle-selective transmission element 6 is the surface on the side of the user's eye, and the second surface 6b is the surface on the side of the eyepiece lens system 10. Details of the optical path splitting prism unit 21 disposed between the display unit 9 and the eyepiece lens system 10 will be described later.

[0015] The angle-selective transmission element 6 is provided with a plurality of openings 6c, which have the function of restricting the direction in which light passes. The plurality of openings 6c are open in the direction of the light beam that travels from the eyepiece lens system 10 toward an eyepoint 13, which is the position of the user's eye. Figure 4 shows a schematic diagram of a viewfinder light beam 12 that reaches the eyepoint 13 out of the light beams emitted from the eyepiece lens system 10. The eyepoint 13 is determined by the eyepiece lens system 10.

[0016] The exterior member 14 of the main body 2 has therein a control circuit 15 that controls the entire HMD 1. The control circuit 15 controls the display unit 9, and light from the display unit 9 is collected by the eyepiece lens system 10 and passes through multiple openings 6c provided in the angle-selective transmission element 6, so that the information displayed on the display unit 9 is observed by the eye at the eyepoint 13.

[0017] Fig. 5 is a cross-sectional view taken along line AA in Fig. 2, and shows the relationship between the EVF 3 and EVF 4 and the head and eyes when the HMD 1 is in use. Fig. 6 shows the relationship between the head and eyes and the HMD 1 when the HMD 1 is in use. Fig. 7 is a detailed view of part B shown in Fig. 6.

[0018] Figure 5 shows the adjustable parts in relation to the EVF3, EVF4 and the eyeball. Because the user can only view the display from near the eyepoint, it is necessary to keep the eye position near the eyepoint at all times. To achieve this, the HMD1 has first to third mechanisms that detect the user's line of sight and use the line of sight detection results to adjust the position.

[0019] The first mechanism is configured to adjust the interpupillary distance (W) so that it can be adjusted to match the width between the user's eyes. Specifically, the EVFs 3 and 4 are guided by a guide bar or the like relative to the main body 2, and are configured to move independently. The second mechanism is configured to adjust the distance (E1) between the eyepoint 13 and the eye-side surface 6a of the angle-selective transmission element 6 (7). The third mechanism is configured to adjust the rotational angle (θ) so that vignetting and changes in the aperture ratio do not occur due to eyeball rotational movement such as shaking the line of sight or changing the convergence angle. By detecting the direction of the user's line of sight, the EVF 3 (EVF 4) is configured to be adjustable in the rotational direction (θ direction) centered on the area 40 where the eye-side surface 6a and the optical axis of the eyepiece lens system 10 intersect. Specifically, the EVF 3 (EVF 4) constitutes a unit of the HMD 1 that can be adjusted in the rotational direction centered on the area 40. The HMD1 unit is attached to the main body 2 so that the interpupillary distance (W) is adjustable. Since the EVF3 and EVF4 each have a mechanism that allows them to move independently, the HMD1 is structured so that the EVF3 and EVF4 can be adjusted to the optimal positions for the left and right eyes by gaze detection units arranged for the left and right eyes of the user. In other words, the control unit of the HMD1 calculates the positions of the user's eyes by gaze detection, and performs control to adjust the EVF3 and EVF4 to the optimal positions by calculating the difference from the reference position in order to align them with the positions of the left and right eyes.

[0020] Combining the line of sight detection function with an angle-selectable transmission element makes it possible to solve the problem of vignetting and reduced aperture ratio caused by a narrow eye box. In addition, there are two types of adjustable parts in the first to third mechanisms: a configuration in which the user manually moves them using a lever or the like, and a configuration in which a motor or the like is incorporated as a power source to move them automatically, and either configuration can be used.

[0021] When using the HMD1 shown in Fig. 6, assume that the light is completely in front of the user, that is, the light is coming from a direction in which the user faces away from the light source (such as the sun). In this case, most of the light that enters the angle-selective transmission element 6 and the eyepiece lens system 10 is blocked by the user's head. However, when the user rotates his or her face from this state to the side by an angle of several tens of degrees, the light that passes through the side of the face (light that passes through the cross-hatched area in Fig. 6) reaches the position of the angle-selective transmission element 6 and the eyepiece lens system 10.

[0022] In the case of the left eye, the area where reverse light may cause ghosts in the eyepiece lens system 10 is the cross-hatched area as shown by the line 17 connecting the point 16 in Fig. 6 with the side of the head. In this embodiment, multiple openings 6c are provided from the eye point 13 toward the eyepiece lens system 10. In order for light to reach the eyepiece lens system 10 located on the side farther away from the multiple openings 6c than the user, a light source must be present in the direction of the hole of the openings 6c. Line 17 in Fig. 6 indicates the position where the direction of the multiple openings 6c and the direction of the light rays are closest, making it easier for reverse light to reach the eyepiece lens system 10.

[0023] As shown in FIG. 7, the plurality of openings 6c inside the angle-selective transmission element 6 are partitioned by walls 6d between adjacent holes. In this embodiment, the interior of the plurality of openings 6c is filled with a transparent solid having a small refractive index difference with air. By filling the interior of the angle-selective transmission element 6 with a transparent solid having a small refractive index difference with air, it is possible to prevent dust from entering the plurality of openings 6c. In addition, it is possible to prevent the wall 6d from being deformed by an external force. In this embodiment, a porous transparent material containing 90% or more of air is used as the transparent solid having a small refractive index difference with air, and the refractive index difference with air is 0.1 or less. Therefore, there is almost no reflection at the interface with air. Inside the plurality of openings 6c, there is almost no reflection at the transparent solid surface having a small refractive index difference with air on both the first surface 6a on the eye side and the second surface 6b on the eyepiece lens system 10 side. Light entering the plurality of openings 6c from the outside enters the interior with almost no reflection.

[0024] In the angle-selective transmission element 6, anti-reflection treatment is applied to the second surface 6b on the eyepiece lens system 10 side, the first surface 6a on the eye side, and the inner wall portions 6d of the multiple openings 6c. The angle-selective transmission element 6 can be created with a 3D printer, and the anti-reflection treatment can be achieved by applying an anti-reflection coating.

[0025] In Fig. 7, light ray 18 represents light that has passed through the side of the user's head. Light ray 18 enters the inside through holes in the multiple openings 6c provided on the first surface 6a of the angle-selective transmission element 6. The light that has entered the multiple openings 6c reaches the wall 6d, but the reflected light is attenuated because the wall 6d is anti-reflection treated. Therefore, even if the reflected light reaches the eyepiece system 10, almost no ghosting occurs.

[0026] The thickness of the angle-selective transmission element 6 is denoted as t, the opening width of the opening 6c is denoted as w, and the incident angle of the unwanted light is denoted as θ0. The condition for preventing the unwanted light from directly reaching the eyepiece lens system 10 is given by the following formula (1). t ≧ w / tan θ0(1) Tan represents a tangent function, and in this embodiment, the condition of formula (1) is satisfied.

[0027] Fig. 8 is a diagram showing a schematic view of the first surface 6a of the angle-selective transmission element 6. The angle-selective transmission element 6 has inner openings 6e1, 6e2 and a plurality of openings 6c around them. Fig. 9 is a cross-sectional view taken along CC in Fig. 8. The plurality of openings 6c provided in the angle-selective transmission element 6 are formed in a hexagonal shape on the second surface 6b, which is the entrance side of the finder light beam, and on the first surface 6a, which is the exit side of the finder light beam. Adjacent hexagonal portions are separated by walls 6d, and the interior is filled with a transparent solid having a small refractive index difference with air.

[0028] Figure 9 (cross-sectional view taken along CC in Figure 8) shows the orientation of the multiple openings 6c. The orientation of the multiple openings 6c is set so as to follow the direction of light toward the eye point 13. The distance between the eye point 13 and the first surface 6a is denoted as E1, and the distance between the eye point 13 and the second surface 6b is denoted as E2. The formation pitch of the multiple openings 6c on the first surface 6a is denoted as P1.

[0029] The multiple openings 6c are provided at equal pitches, and the distance from the center of the optical axis is represented as Hi. In the right half of FIG. 9 based on the center of the optical axis, i in "Hi" represents any natural number from 1 to 9. H1=P1 H2=P1×2 · · H8=P1×8 H9=P1×9 In other words, the relationship is "Hi = P1 x i."

[0030] With respect to the center of the optical axis as a reference, the angle of each line connecting the eye point 13 and each of the openings 6c is represented as θi. The i in “θi” represents any natural number from 1 to 9. θ1=tan -1 (H1 / E1) θ2=tan -1 (H2 / E1) · · θ8=tan -1 (H8 / E1) θ9=tan-1 (H9 / E1) tan -1 represents the arctangent function, and "θi = tan -1 (Hi / E1)" relationship. The pitch P2 of the multiple openings 6c on the second surface 6b is as shown in the following formula (2). P2 = E2 × tan θ1 (2) In FIG. 9, the right half surface has been described with reference to the center of the optical axis, but the same relationship as above also applies to the left half surface since the configuration is symmetrical with respect to the optical axis.

[0031] When the eyepiece lens system 10 is viewed from the user's eye with the eye point 13 as a reference, the eyepiece lens system 10 is visible through the multiple openings 6c. The wall portion 6d is approximately parallel to the direction of light reaching the user's eye, so it is almost invisible. Furthermore, when the user's eye is at the eye point 13, the first surface 6a is close to the eye and the view is not in focus. The wall portion 6d is made thin, so the flat portion at the entrance of the wall portion 6d is also almost invisible.

[0032] The user can only view the displayed information from the vicinity of eyepoint 13, and the position of the eyes must be fixed near eyepoint 13. In this embodiment, the head mounting unit 5 fixes the relative positional relationship between the user's head and HMD 1, thereby enabling the eyes to be placed at eyepoint 13.

[0033] Fig. 10 is a perspective view showing the configuration of the EVF portion. Fig. 11 is a cross-sectional view of the EVF portion on the optical axis. In order from the side closest to the eyepoint 13, the angle-selection-type transmission element 6, the eyepiece lens system 10, the second optical-path splitting prism 20, the first optical-path splitting prism 19, and the display unit 9 are shown.

[0034] The first optical path dividing prism 19 and the second optical path dividing prism 20 constitute an optical path dividing prism unit 21. The optical path dividing prism unit 21 is an optical path dividing means formed by bonding the first optical path dividing prism 19 and the second optical path dividing prism 20 together.

[0035] The infrared LEDs 22, 23 are light-emitting elements that illuminate the eye for gaze detection. The infrared LEDs 22, 23 constitute a light-projecting section and are arranged on the first surface 6a side of the angle-selective transmission element 6. The infrared LEDs 22, 23 are arranged to irradiate infrared light toward different positions, and are used in pairs to detect the distance between the EVF portion (including the light-receiving section) and the viewer's eye. The lens 24 is a gaze imaging lens of the gaze detection optical system. The sensor 25 that constitutes the light-receiving section is a gaze detection sensor.

[0036] Light from the eyeball illuminated by the infrared LEDs 22 and 23 passes through the angle-selective transmission element 6 and the eyepiece lens system 10, and enters the second optical path splitting prism 20 from the second surface 20a. This is shown by optical path 26a in Figure 6. A dichroic film that reflects infrared light is formed on the first surface 20b of the second optical path splitting prism 20.

[0037] The light from the eyeball illuminated by the infrared LEDs 22 and 23 is reflected by the first surface 20b of the second optical path splitting prism 20. The light is reflected in the direction of the second surface 20a. This reflected optical path is indicated by optical path 26b. The light along the reflected optical path 26b is totally reflected by the second surface 20a, and the light along the imaging optical path 26c is imaged on the visual line detection sensor 25 by the visual line imaging lens 24.

[0038] To detect the line of sight, a corneal reflection image formed by regular reflection of infrared LED light from the cornea is used in addition to the eyeball image created by illumination. Figure 10 shows the optical path of light emitted from infrared LEDs 22 and 23 and reflected by the cornea 27 of the eyeball.

[0039] FIG. 11 shows optical paths 26a, 26b, and 26c that are directed toward the line of sight detection sensor 25 after light is reflected by the cornea 27. Of these optical paths, the direction of the optical path 26a is not the same as the direction of the opening 6c that is set to the direction of light from the eyepiece lens system 10 toward the eye point 13. The inner openings 6e1 and 6e2 (see FIG. 8) in the angle-selective transmission element 6, through which the light along the optical path 26a passes, are formed substantially parallel to the optical path 26a so as not to cause vignetting. In addition, since there are individual differences in the way light exits from the optical path 26a (differences in corneal curvature), the openings 6e1 and 6e2 are formed larger than the adjacent openings 6c. By making the openings 6e1 and 6e2 larger, the light that passes through the side of the user's head can easily enter the inside of the openings, but by making the thickness of the angle-selective transmission element 6 larger, the light is reflected more times and attenuated inside the openings 6e1 and 6e2. In this embodiment, the part 6f of the angle-selective transmission element 6 is thicker than the peripheral part. That is, the thickness of the part 6f of the angle-selective transmission element 6 is increased along the opposing surface (curved surface) of the eyepiece lens system 10, and openings 6e1 and 6e2 are formed in this part.

[0040] FIG. 12 is a schematic diagram for explaining the eyeball distance between the eyeball image and the corneal reflection image. The iris 28, the pupil 29, and the corneal reflection images 30 and 31 by the infrared LEDs 22 and 23 for illumination are shown. The direction of the gaze is detected from the relationship between the center of the pupil 29 and the corneal reflection image. For gaze detection, a method is known that uses reflected light obtained when illuminating the observer's eyeball surface. For example, a correction coefficient for correcting the individual difference of the user's eyeball is acquired by gaze correction, and then gaze input processing is performed, and the angle of the gaze direction and the coordinate value on the observation surface are calculated using an arithmetic expression corresponding to the correction coefficient. Specifically, this can be realized by the method disclosed in Patent Document 2, so detailed explanation will be omitted.

[0041] In a configuration in which the direction of the opening of the angle-selective transmission element is set to the direction of light going from the lens to the eye point, measures are required to prevent vignetting caused by a narrow eye box and a decrease in the aperture ratio. Also, measures are required to suppress vignetting of the infrared LED light going from the eye point to the gaze detection sensor.

[0042] In this embodiment, in a finder using an angle-selection type transmission element, a measure can be taken by detecting the direction of the user's line of sight and using the line of sight detection result. Also, a finder having a line of sight detection function that realizes a function such as a range finder point selection while reducing ghosts caused by light coming from behind the user can be provided.

[0043] [Second Example] A second embodiment of the present invention will be described with reference to Figures 13 and 14. Explanations of matters similar to those in the first embodiment will be omitted, and differences from the first embodiment will be explained. Such omissions will be the same in the embodiments described below.

[0044] In this embodiment, an example is shown in which a line-of-sight detection sensor 25 is disposed in the vicinity of an angle-selective transmission element 6. Fig. 13 is an external view of the angle-selective transmission element 6 of this embodiment, showing the first surface 6a side. Fig. 14 is a configuration diagram of the DD cross section in Fig. 13.

[0045] In this embodiment, the gaze detection sensor 25 is disposed outside the eyepiece lens system 10. An angle-selective transmission element 6 is provided on the front side (eye point 13 side) of the infrared LEDs 22, 23 and the gaze detection sensor 25. Since this configuration makes it difficult for sunlight, which is external light, to be directly incident on the gaze detection sensor 25, it is possible to suppress the occurrence of erroneous detection.

[0046] 14, light traveling from eye point 13 toward gaze detection sensor 25 is shown as optical path 32. The direction of optical path 32 is not the same as the direction of opening 6c that is set in the direction of light traveling from eyepiece lens system 10 toward eye point 13. Opening 6g of angle-selective transmission element 6 through which light traveling along optical path 32 passes is formed in a cone shape with a taper angle (see θt in FIG. 14) whose axis is approximately parallel to optical path 32 so as to prevent vignetting.

[0047] [Third Example] Next, a third embodiment of the present invention will be described. This embodiment differs from the previous embodiments in that the angle-selective transmission element 6 is made of an infrared-transmitting resin material.

[0048] The angle-selective transmission element 6 is made of a material that transmits infrared light and absorbs visible light. According to this embodiment, it is possible to suppress intrusion of external light such as sunlight without changing the direction of the opening of the angle-selective transmission element 6 in accordance with the optical path from the eye point 13 to the gaze detection sensor 25.

[0049] According to the above embodiment, it is possible to provide an optical device having a line of sight detection function that can suppress vignetting and a decrease in aperture ratio by detecting the line of sight of the user, and can realize a function such as a range finding point selection while reducing ghosting caused by light coming from behind the user. Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of the gist thereof. [Explanation of symbols]

[0050] 3,4 EVF 6,7 Angle-selective transmission element 6c,6e1,6e2,6g opening

Claims

1. An optical device having a viewfinder, an angle-selective transmission element disposed in an optical path of the viewfinder; a detection means for detecting a line of sight by light passing through the angle-selective transmission element; a mechanism capable of adjusting the direction of the viewfinder to the line of sight direction detected by the detection means; 1. An optical device comprising:

2. The angle-selective transmission element has a plurality of openings that restrict the passing direction of the light beam.

2. The optical device according to claim 1.

3. The detection means has a light projecting portion and a light receiving portion, A first opening of the plurality of openings has a first angle that limits the passing direction of the light beam in a first region with respect to an optical axis of the viewfinder, a second opening has a second angle that limits the passing direction of the light beam in a second region, and a third opening has a third angle that is defined by a line connecting an eye point in the viewfinder and the light receiving unit.

3. The optical device according to claim 2.

4. The third opening has a larger opening than the first or second opening.

4. The optical device according to claim 3.

5. The third opening is formed closer to the optical axis of the finder than the first or second opening.

5. The optical device according to claim 3 or 4.

6. The portion of the angle-selective transmission element where the third opening is formed has a thickness greater than that of the surrounding portion of the portion.

6. An optical device according to claim 3, wherein the optical device is a casing.

7. Equipped with an eyepiece lens system, The portion of the angle-selective transmission element where the third opening is formed is formed along a curved surface facing the eyepiece lens system.

7. The optical device according to claim 6.

8. The third opening is formed at a position farther from the optical axis of the finder than the first or second opening.

5. The optical device according to claim 3 or 4.

9. Equipped with multiple viewfinders, one for each eye, The viewfinder is independently adjustable to the detected line of sight 9. An optical device according to claim 1, wherein the optical device is a casing.

10. The angle-selective transmission element is formed of an infrared-transmitting material.

10. An optical device according to claim 1 .

11. The optical device according to any one of claims 1 to 10, The viewfinder has a display means and an eyepiece system. A display device comprising:

12. an optical path splitting prism unit is provided between the display means and the eyepiece lens system; The detection means detects light that has passed through the optical path splitting prism unit. The display device according to claim 11 .

13. The detection means has a light projecting section and a light receiving section disposed between the eyepiece lens system and the angle-selective transmission element. The display device according to claim 11 .

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