Patent ID: 12196962

DESCRIPTION OF EXEMPLARY EMBODIMENTS

First Embodiment

Hereinafter, an example of a virtual image display device according to a first embodiment of the present disclosure and an optical unit incorporated therein will be described with reference to the drawings.

As illustrated inFIG.1, a virtual image display device100according to a first embodiment is a head-mounted display (HMD) having an external appearance like eyeglasses, and causes an observer or a user US wearing the virtual image display device100to recognize an image as a virtual image. InFIG.1, X, Y, and Z are orthogonal coordinate systems, the +X direction corresponds to a lateral direction in which both eyes of a user US wearing the virtual image display device100are arranged, the +Y direction corresponds to an upward direction orthogonal to the lateral direction in which both eyes of the user US are arranged, and the +Z direction corresponds to a forward direction or a front direction of the user US.

The virtual image display device100includes a first display device101A that forms a virtual image for the right eye, a second display device101B that forms a virtual image for the left eye, and a temple-shaped support device101C that supports both display devices101A and101B. The first display device101A includes an optical unit102disposed at an upper portion thereof and an appearance member103that has a spectacle lens shape and covers the entirety. Similarly, the second display device101B includes an optical unit102disposed at the upper portion thereof and an appearance member103that has a spectacle lens shape and covers the entirety. The support device101C supports both the display devices101A and101B on the upper end side of the appearance member103by a member (not illustrated) disposed behind the appearance member103. The second display device101B for the left eye has the same structure as the first display device101A. Hereinafter, the first display device101A will be described, and the description of the second display device101B will be omitted.

As illustrated inFIG.2, the first display device101A for the right eye includes a display element11and an optical unit12, as optical elements. Of these, the optical unit12includes a light-guiding system12aand a mirror member12b. The optical unit12is also referred to as a light-guiding device from the viewpoint of guiding image light ML from the display element11to the pupil position PP.

The display element11is a self-luminous display device represented by, for example, an organic EL (Organic Electro-Luminescence), an inorganic EL, an LED array, an organic LED, a laser array, and quantum dot light-emitting element, or the like, and forms a color still image or moving image on a two dimensional display surface11a. The display element11is driven by a drive control circuit (not illustrated) to perform a display operation. When an organic EL display or display device is used as the display element11, an organic EL control unit is provided. When a quantum dot light-emitting display is used as the display element11, light from a blue light-emitting diode (LED) is passed through a quantum dot film to emit green or red light. The display element11is not limited to a self-luminous display element, and may be configured by an LCD and other light modulation element, and may form an image by illuminating the light modulation element with a light source such as a backlight. As the display element11, an LCOS (Liquid crystal on silicon, LCoS is a registered trademark), a digital micro-mirror device, or the like may be used instead of the LCD.

The optical unit (light-guiding device)12includes a light-guiding system12athat guides the image light ML emitted from the display element11, and a mirror member12bthat reflects the image light ML emitted from the light-guiding system12atoward the pupil position PP. In the illustrated example, the optical unit12includes a projection lens (projection prism)21, a prism22, and a see-through mirror23. Of these, the projection lens21and the prism22function as a light-guiding system12a, and the see-through mirror23functions as a mirror member12b.

Hereinafter, the projection lens21, the prism22, and the see-through mirror23constituting the optical unit12will be described in more detail.

First, among the constituent components of the light-guiding system12a, the projection lens (projection prism)21is a single lens (single prism) and has an incident surface21aand an emission surface21bas its constituent optical surfaces. The projection lens21converges the image light ML emitted from the display element11.

In the light-guiding system12a, the prism22is formed by providing a mirror deposition surface on a part of an optically transparent prism member (main body portion). That is, the prism22is a refractive/reflective optical member having a function of combining a mirror and a lens, and guides the image light ML emitted from the projection lens21. The prism22receives the image light ML from the projection lens21, guides the image light ML inside, and emits the image light ML. Therefore, the prism22has, as constituent surfaces, a first surface22athat is a transmissive surface, a second surface22bthat is a reflective surface (internal reflective surface) and is also a transmissive surface, and a third surface22cthat is a reflective surface (internal reflective surface). Among them, the first surface22ais an incident surface at which the image light ML is incident, and the second surface22bis an emission surface from which the image light ML is emitted. In particular, the second surface22bincludes a reflective area RS that functions as a reflective surface and a transmissive area TS that functions as a transmissive surface. That is, on the second surface22b, there are the reflective area RS that reflects the image light ML and a transmissive area TS that transmits the image light ML. In the illustrated example, on the second surface22b, the reflective area RS is provided closer to the first surface22a(closer to the projection lens21) and the transmissive area TS is provided closer to the third surface22c(farther from the projection lens21). However, an overlapping area of the reflective area RS and the transmissive area TS may exist on the second surface22b. By providing the overlapping area, the prism22can be miniaturized.

In the illustrated example, the first surface22ahas a curved surface SS1having a convex shape toward the projection lens21as a surface having an optical function, and has a flat surface SS2as a coupling surface coupling the third surface22C and the curved surface SS1, as a surface having no optical function. In this case, the curved surface SS1of the first surface22ais located lower (−Y side) than the flat surface SS2.

In the prism22having the first surface22a, the second surface22b, and the third surface22cas described above, the image light ML emitted from the projection lens21first enters while being transmitted at the first surface22athat is the incident surface of the prism22, and then is reflected by the reflective area RS of the second surface22b. Here, in the illustrated example, in the reflection in the reflective area RS, the incident angle, relative to the second surface22b, of the image light ML that passed through the first surface22ais adjusted so as to satisfy the total reflection requirement. That is, the prism22totally reflects (internally reflects) the image light ML that passed through the first surface22aat the second surface22b. The image light ML that passed through the reflective area RS of the second surface22bis further reflected by the third surface22cand travels toward the second surface22bagain. However, the image light ML travels toward the transmissive area TS of the second surface22b. Further, at this time, the incident angle of the image light ML relative to the second surface22bis adjusted for the image light ML to transmit through the second surface22b. Therefore, the image light ML is emitted from the prism22by transmitting (passing) through the transmissive area TS. That is, in this case, the second surface22bfunctions as the emission surface of the prism22. As described above, the second surface22bfunctions as a transmissive/reflective surface that transmits or reflects the image light ML according to the incident angle. In other words, regarding the emission of the image light ML, the prism22emits while transmitting the image light ML reflected by the third surface22cat the second surface22b(transmissive area TS). That is, the prism22emits the image light ML toward the see-through mirror23disposed in the rear stage of the optical path by transmitting the image light ML at the second surface22b.

In the present embodiment, transmission (refraction) and reflection are repeated in the prism22, thereby increasing the number of surfaces for aberration correction and improving the optical function. That is, the prism22enhances the function of aberration correction (in particular, the function of correcting eccentric aberration) together with the projection lens21that is another optical element constituting the virtual image display device100.

The projection lens21and the prism22constituting the light-guiding system12ahave, for example, asymmetry with respect to the vertical direction, that is, the Y direction, and symmetry with respect to the lateral direction, that is, the X direction. Further, each of the optical surfaces (the incident surface21a, the emission surface21b, the first surface22a, the second surface22b, and the third surface22c) of the projection lens21and the prism22can be, for example, a free curved surface or an aspherical surface. By forming each surface as a free curved surface or an aspherical surface, it is possible to reduce aberration. In particular, when a free curved surface is used, it is easy to reduce aberration of the optical unit12that is an off-axis optical system or a non-coaxial optical system described later.

Moreover, the single lens constituting the projection lens21and the main body portion of the prism22are made of, for example, resin, but may be made of glass. For example, the prism22may be formed by forming a main body portion of COP (cycloolefin polymer) and providing a portion to be a third surface22cby forming a mirror deposition surface on a part of surfaces of the main body portion.

On the other hand, the see-through mirror23constituting the mirror member12bis, so as to function as a front mirror, a plate-shaped optical member that covers the pupil position PP where the eye EY or the pupils are arranged and that has a concave shape toward the pupil position PP. The see-through mirror23has a reflective surface23aon the side close to the prism22and the pupil position PP, that is, on the inner side of the concave shape, among the optical surfaces arranged on the light path. In addition, the see-through mirror23(reflective surface23a) is a transmission type reflective element which transmits a part of light at the time of reflection, and allows the external light HL to be visually recognized while being superimposed on the image light ML, that is, allows see-through viewing.

The main body portion of the see-through mirror23is made of, for example, resin, but may be made of glass. The see-through mirror23is formed by providing one layer or two or more layers of a mirror film as a vapor deposition film on a resin-made or glass-made light transmitting member to form a reflective surface23a. In addition, in order to make the shape, size, and weight of the see-through mirror23appropriate, it is conceivable to make the thickness about 2 mm, for example.

Although not illustrated in detail, the projection lens21and the prism22are housed together with the display element11in a case (not illustrated) made of a light-shielding material, and the see-through mirror23is supported via, for example, a support plate provided in the case. As described above, for example, the appearance member103supported by the the support device101C illustrated inFIG.1is constituted.

Hereinafter, light guiding, by the optical unit12as the light guiding device, of the image light ML emitted from the display element11will be briefly described with reference toFIG.2.

First, the projection lens21causes the image light ML emitted from the display element11to be incident while being refracted at the incident surface21a, and causes the image light ML to be emitted while being refracted at the emission surface21b. As a result, the projection lens21converges the image light ML in a state close to a parallel light flux and emits the image light ML toward the prism22. Next, as described above, the prism22causes the image light ML emitted from the projection lens21to be incident while being refracted at the first surface22aas the incident surface, to be reflected (totally reflected) at the reflective area RS of the second surface22b, to be reflected at the third surface22cas the internal reflective surface, and to be emitted from the transmissive area TS of the second surface22bas the emission surface while being refracted. Finally, the see-through mirror23reflects, at the reflective surface23a, the image light ML emitted from the prism22toward the pupil position PP. The pupil position PP is a position where the image light ML from each point on the display surface11ais incident so as to be superimposed from an angle direction corresponding to the position of each point on the display surface11ain a predetermined divergent state or parallel state. The illustrated optical unit12has a field of view (FOV) of 44°. The display area of the virtual image by the optical unit12is rectangular, and the above-mentioned 44° is in the diagonal direction.

On the other hand, the external light HL transmits through the see-through mirror23and is emitted from the reflective surface23a. That is, since the the reflective surface23ahas optical transparency, the virtual image can be superimposed on the external image.

Note that in the above example, the optical unit12is an off-axis optical system. That is, the projection lens21, the prism22, and the see-through mirror23constituting the optical unit12are arranged so as to form an off-axis optical system. The optical unit12being an off-axis optical system means that a light path is bent as a whole before and after a light beam is incident on at least one reflective surface or refractive surface in the optical element21,22,23constituting the optical unit12. In the illustrated example, the optical axis is bent while extending along a plane parallel to the Y-Z plane. That is, in the optical unit12, by bending the optical axis along the Y-Z plane, the optical elements21,22,23are also arranged along the Y-Z plane. The optical axis of the optical unit12that is the above-described off-axis optical system, is arranged in a Z-shape, viewed in cross-section, after reflection at the reflective area RS of the second surface22b. That is, in the drawing, a light path from the second surface22b(reflective area RS) of the prism22to the third surface22c, a light path from the third surface22cto the see-through mirror23, and a light path from the see-through mirror23to the exit pupil EP, are arranged to be folded back in two steps in a Z-shape.

In the light path of the image light ML illustrated in the drawing, the intermediate image IM is formed between the prism22and the see-through mirror23.

Hereinafter, the shape feature of the prism22will be further described with reference toFIG.3.FIG.3is a side cross-sectional view conceptually illustrating a structure of the prism22, and illustrates the reflective area RS of the second surface22band the third surface22cthat are reflective surfaces (internal reflective surfaces) in a partially enlarged manner in the drawing. To be more specific, inFIG.3, the state of reflection (total reflection) in the reflective area RS of the second surface22bis illustrated in a partially enlarged manner as a state α, and the state of reflection (mirror surface reflection) in the third surface22cis illustrated in a partially enlarged manner as a state β. As illustrated, in the second surface22b, the reflective area RS that reflects the image light ML has a concave shape, and the third surface22calso has a concave shape. In other words, the prism22has two concave reflective surfaces. Accordingly, the virtual image display device100according to the present embodiment can improve the performance of aberration correction or reduce the load of aberration correction by suppressing the power of each reflective surface, as compared with a case where a portion corresponding to the prism22is configured by one concave reflective surface.

Further, as illustrated by a two-way arrow DD1inFIG.3, it is desirable that the second surface22band the third surface22care separated from each other to some extent. Here, the distance from the second surface22bto the third surface22cindicated by the two-way arrow DD1means a distance between the origins of the optical surfaces forming the second surface22band the third surface22c, respectively, and it is desirable that the distance falls within any of the ranges from 5 mm to 15 mm, for example. Since there is provided such a certain distance, aberration correction by the concave surface can be performed at a position where the light beam of the image light ML spreads away from the intermediate image IM (seeFIG.2) on the emission side of the second surface22b.

Hereinafter, distortion in the virtual image display device100will be described with reference toFIG.4. As illustrated inFIG.4, the original projection image IG0illustrating the imaging state by the optical unit12has a relatively large distortion. Since the optical unit12is an off-axis optical system, it is not easy to remove distortion such as trapezoidal distortion. Therefore, even when the distortion remains in the optical unit12, in a case where the original display image is set as the DA0, the display image formed on the display surface11ais set as the corrected image DA1having the trapezoidal distortion which is previously distorted. That is, it is assumed that the image displayed on the display element11has an inverse distortion to cancel the distortion generated by the projection lens21, the prism22, and the see-through mirror23. As a result, the pixel array of the projected image IG1of the virtual image observed at the pupil position PP via the optical unit12can be a grid pattern corresponding to the original display image DA0, and the outline of the projected image IG1can be rectangular. As a result, it is possible to suppress aberration as a whole including the display element11while allowing distortion aberration generated in the optical unit12. In addition, when the external shape of the display surface11ais rectangular, a margin is formed by forming a forced distortion, and additional information can be displayed in such a margin. The corrected image DA1formed on the display surface11ais not limited to one in which the forced distortion is formed by the image processing, and for example, the arrangement of the display pixels formed on the display surface11amay correspond to the forced distortion. In this case, image processing for correcting the distortion is unnecessary. Furthermore, the display surface11amay be curved to correct the aberration.

As described above, the virtual image display device100according to the present embodiment includes a display element11, a projection lens21configured to converge image light ML emitted from a display element11, a prism22configured to guide the image light ML emitted from the projection lens21, and a see-through mirror23as a mirror member12bconfigured to reflect, toward a pupil position PP, the image light ML emitted from the prism22, wherein the prism22includes a first surface22aat which the image light ML from the projection lens21is incident while being transmitted, a second surface22bat which the image light ML that passed through the first surface22ais reflected, and a third surface22cat which the image light ML that passed through the second surface22bis reflected toward the second surface22b, and the image light ML that was reflected at the third surface22cis emitted while being transmitted through the second surface22b. That is, in the virtual image display device100, in the prism22having the first surface22ato the third surface22c, the image light ML emitted from the projection lens21first is incident while being transmitted at the first surface22a, is then reflected by the reflective area RS of the second surface22b, is further reflected at the third surface22cto be directed toward the second surface22bagain, and is emitted while being transmitted through the transmissive area TS of the second surface22b. This makes it possible to increase the number of surfaces on which aberration can be corrected without increasing the size of the optical system, and to improve the resolution performance, as compared with, for example, an aspect in which only the image light ML is transmitted through a portion corresponding to the prism22, or only one internal reflection is performed in addition to the transmission.

Second Embodiment

Hereinafter, a virtual image display device or the like according to a second embodiment of the present disclosure will be described. The virtual image display device according to the second embodiment is obtained by partially modifying the virtual image display device according to the first embodiment, and a description of common portions is omitted.

An example of the optical system of the virtual image display device according to the present embodiment will be described with reference toFIGS.5and6.FIG.5is a side cross-sectional view illustrating an optical system of a virtual image display device100according to the present embodiment, and corresponds toFIG.2. Further,FIG.6is a side cross-sectional view conceptually illustrating a structure of a prism222that constitutes the virtual image display device100according to the present embodiment.

As illustrated inFIGS.5and6, the present embodiment differs from the aspect illustrated in the first embodiment in that the prism222has a laminated structure in which a high refractive member222his attached to a main body portion222p.

Hereinafter, the structure of the prism222will be described in more detail. In the prism222, as in the first embodiment, for example, the main body portion222pis formed of COP, and a high refractive member222hformed of polycarbonate, OKP (optical polyester), or the like having a higher refractive index than COP is attached to the main body portion222p. In particular, in the illustrated example, the second surface22bof the prism222is formed by the high refractive member222h. In other words, the prism222forms the second surface22bwith the high refractive member222hhaving a relatively higher refractive index than the main body portion222p. As in the case of the first embodiment, the third surface22cis provided by providing a mirror deposition surface on a part of the main body portion222p.

As described above, the prism222has a laminated structure in which the main body portion222pand the high refractive member222h, which are members having different refractive indices, are combined.

With the above-described laminated structure, as compared with the case illustrated in the first embodiment, for example, the light path of the image light ML, as illustrated inFIG.6, increases the number of passages such that the light path additionally passes (transmits) through the laminated surface AS, in the second surface22b, between the main body portion222pand the high refractive member222hthree times in total including two times of passage (refraction) before and after reflection at the reflective area RS and one time of passage (refraction) before transmission at the transmissive area TS. In this case, the optical element (high refractive member222h) to be attached to the main body portion222pis made of a material having a higher refractive index than the main body portion222p(combining members having different in refractive index), so that the condition of total reflection of the image light ML in the reflective area RS of the second surface22bcan be relaxed, and the optical system can be further miniaturized. In addition, it is considered that the thickness TT of the high refractive member222his, for example, about 1 mm.

Further, here, for example, as illustrated inFIG.5, in the second surface22bformed by the high refractive member222h, there is an overlapping area OS of the reflective area RS that reflects the image light ML and the transmissive area TS that transmits the image light ML.

Furthermore, for example, the laminated surface AS of the main body portion222pand the high refractive member222hmay be made a curved surface different from the reflective area RS of the second surface22bto further increase the transmissive surface (refractive surface) and improve aberration correction and resolution performance.

For the bonding of the main body portion222pand the high refractive member222hat the laminated surface AS, it is considered that a high refractive material (polycarbonate or the like)222hto be the high refractive member222his bonded to the main body portion222pby an acrylic or epoxy adhesive or the like. In addition, it is conceivable to adopt, for positioning at the time of bonding, positioning by an outer shape of each optical surface, positioning provided with a positioning mechanism, or the like.

As described above, in the present embodiment, the prism222has a laminated structure in which the high refractive member222his laminated to the main body portion222p. Accordingly, the virtual image display device100can miniaturize the optical system and further increase the number of aberration correction surfaces.

Modified Examples and Others

The present disclosure is described according to the above embodiments, but the present disclosure is not limited to the above embodiments. The present disclosure may be implemented in various modes without departing from the gist of the present disclosure, and, for example, the following modifications may be implemented.

In the virtual image display device100of the embodiment described above, the virtual image visually recognized by the image light ML is not limited to the case where the component to be recognized as the image (virtual image) of the central portion is in the state along the Z direction as illustrated inFIGS.2and5, but the light path may be appropriately adjusted to be, for example, about −10° toward the Z direction, with the downward direction being negative as illustrated inFIG.7. In other words, the see-through mirror23covering the front side (+Z side) of the pupil position PP may be disposed such that the emission optical axis extends inclined downward by about 10° with respect to the +Z direction. This is because the line-of-sight of a person is stabilized in a slightly downcast eye state in which the line of sight is inclined downward by about 10° from the horizontal direction. Note that the horizontal direction in the virtual image display device100is based on the assumption that the user US wearing the virtual image display device100is in an upright posture, relaxed, facing the front, and gazing at the horizontal direction or the horizontal line. The shape and posture of the head including the arrangement of the eyes, the arrangement of the ears, or the like of each user US wearing the virtual image display device100are various. However, by assuming an average head shape or head posture of the user US, an average direction can be set as a horizontal direction for the virtual image display device100of interest.

In the above description, the image light ML is totally reflected in the reflective area RS of the second surface22b. However, for example, a mirror vapor deposition film may be formed in a portion or a part of the reflective area RS to perform reflection.

In addition, in the above description, for example, the size of the optical unit12in the plane direction or the Z direction may be arranged such that the distance from the pupil position PP to the see-through mirror23is from about 30 mm to 40 mm.

In addition to the case where the see-through mirror23is a concave plate member having a uniform thickness, the see-through mirror23may have, for example, asymmetry with respect to the vertical direction, that is, the Y direction, and symmetry with respect to the lateral direction, that is, the X direction, similar to the projection lens21and the prism22. Furthermore, it is also conceivable that the surface shape of the see-through mirror23may be a free curved surface or an aspherical surface, for example.

In the virtual image display device100of the above-described embodiment, a self-luminous display device such as an organic EL element, an LCD, and other light modulation elements are used as the display element11, but instead of this, a configuration using a laser scanner in which a laser light source and a scanner that is a polygon mirror or the like are combined is also possible. That is, the present disclosure can also be applied to a laser retina projection type head-mounted display.

A light control device that controls light by limiting transmitted light of the see-through mirror23may be attached on the external side of the see-through mirror23. The light control device adjusts the transmittance electrically, for example. As the light control device, a mirror liquid crystal, an electronic shade, or the like can be used. The light control device may adjust the transmittance according to the external light illuminance. When the external light HL is blocked by the light control device, only the virtual image that is not affected by the external image can be observed. In addition, the virtual image display device of the present disclosure can be applied to a so-called closed type head-mounted display device (HMD) that blocks external light and allows only image light to be visually recognized. In addition, the virtual image display device of the present disclosure may also be compatible with a so-called see-through video product constituted by a virtual image display device and an imaging device.

In the above description, it is assumed that the virtual image display device100is used while being mounted on the head. However, the virtual image display device100described above can also be used as a hand-held display that is not mounted on the head but viewed into it like binoculars. That is, according to an aspect of the present disclosure, the head-mounted display includes a hand-held display.

In the above description, light is guided in the vertical direction or the Y direction, but light may be guided in the lateral direction or the X direction.

The virtual image display device according to a specific aspect, includes a display element, a projection lens configured to converge image light emitted from the display element, a prism configured to guide the image light emitted from the projection lens, and a mirror member configured to reflect, toward a pupil position, the image light emitted from the prism, wherein the prism includes a first surface where the image light from the projection lens is incident while being transmitted, a second surface at which the image light that passed through the first surface is reflected, and a third surface at which the image light that passed through the second surface is reflected toward the second surface, and the image light reflected at the third surface is emitted while being transmitted through the second surface.

In the virtual image display device, in the prism having the first surface to the third surface, the image light emitted from the projection lens first enters while being transmitted from the first surface, is then reflected by the second surface, is further reflected by the third surface to be directed toward the second surface again, and is emitted while being transmitted through the second surface. This makes it possible to increase the number of surfaces on which aberration can be corrected without increasing the size of the optical system and to improve the resolution performance, as compared with, for example, an aspect in which only light is transmitted through a prism or only one internal reflection is performed by a prism in addition to the transmission.

In a specific aspect, the prism reflects, by total reflection at the second surface, the image light that passed through the first surface. In this case, the image light can be reflected at the second surface with high efficiency.

In another aspect, of the second surface, a reflective area that reflects image light has a concave shape.

The third surface has a concave shape. In this case, the performance of aberration correction can be improved, and the burden of aberration correction can be shared between the second surface and the third surface.

In still another aspect, in the second surface, there is an overlapping area of a reflective area that reflects the image light and a transmissive area that transmits the image light. In this case, the prism can be further miniaturized.

In still another aspect, in the second surface, the reflective area that reflects the image light is provided at a position closer to the projection lens than the transmissive area that transmits the image light.

In still another aspect, the prism has a laminated structure in which members having different refractive indexes are combined. In this case, light path control and aberration correction, which use the refractive index difference, can be performed.

In still another aspect, the prism forms the second surface with a high refractive member having a relatively high refractive index. In this case, reflection and transmission at the second surface can be adjusted by the high refractive member.

In still another aspect, the mirror member is a see-through mirror configured to reflect the image light emitted from the prism toward a pupil position and transmit external light. In this case, so-called AR (Augmented Reality) viewing becomes possible.

In still another aspect, in the prism, the first surface, the second surface, and the third surface are free curved surface. In this case, the entire optical system including the prism can be miniaturized.

In still another aspect, the projection lens has a free curved surface as an optical surface. In this case, high accuracy of the projection lens can be achieved.

In yet another aspect, the projection lens, the prism and the mirror member form an off-axis optical system. In this case, it is possible to miniaturize the optical system while maintaining the resolution, and thus to miniaturize the entire apparatus.

In still another aspect, a Z-shaped light path is formed by a two-step folding obtained by folding the light path at the third surface of the prism and at the mirror member. In this case, the apparatus can be miniaturized by bending the light path in a Z-shape.

In yet another aspect, the image displayed on the display element has distortion that cancels the distortion generated by the projection lens, the prism, and the mirror member. In this case, it is possible to suppress aberration as a whole including the display element while allowing distortion aberration generated in the mirror member or the like.

In still another aspect, the first surface has a curved surface that is convex toward the projection lens.

An optical unit according to a specific aspect, includes a projection lens configured to converge image light emitted from a display element, a prism configured to guide the image light emitted from the projection lens, and a mirror member configured to reflect, toward a pupil position, the image light emitted from the prism, wherein the prism includes a first surface where the image light from the projection lens is incident while being transmitted, a second surface at which the image light that passed through the first surface is reflected, and a third surface at which the image light that passed through the second surface is reflected toward the second surface, and the image light reflected at the third surface is emitted while being transmitted through the second surface.

In the optical unit, in the prism having the first surface to the third surface, the image light emitted from the projection lens first is incident while being transmitted at the first surface, is then reflected at the second surface, is further reflected at the third surface to be directed toward the second surface again, and is emitted while being transmitted through the second surface. This makes it possible to increase the number of surfaces on which aberration can be corrected without increasing the size of the optical system and to improve the resolution performance, as compared with, for example, an aspect in which only light is transmitted through a prism or only one internal reflection is performed by a prism in addition to the transmission.