JP6184370B2 - Light guide prism and image display device - Google Patents

Light guide prism and image display device Download PDF

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JP6184370B2
JP6184370B2 JP2014094107A JP2014094107A JP6184370B2 JP 6184370 B2 JP6184370 B2 JP 6184370B2 JP 2014094107 A JP2014094107 A JP 2014094107A JP 2014094107 A JP2014094107 A JP 2014094107A JP 6184370 B2 JP6184370 B2 JP 6184370B2
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surface
prism
light guide
side
light
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JP2015087742A (en
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良平 杉原
良平 杉原
高橋 真也
真也 高橋
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オリンパス株式会社
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  The present invention relates to a light guide prism that guides video light from a display element and displays a virtual image of a display image in an observer's field of view, and an image display device using the light guide prism.

  In recent years, there has been proposed a small and wearable image display device that is worn on a head or glasses. As such an image display device, for example, image light of an image displayed on a small image display element fixed to the temporal region is guided to the eyes by a transparent light guide member and observed as an enlarged virtual image. What is displayed within the visual field of a person is known (for example, see Patent Document 1). The small and light-weight light guide member does not greatly obstruct the field of view, and the entire image display apparatus can be configured to be small and light, and can be used as a wearable device that can always be worn and used.

  However, when the light guide member is downsized, stray light and ghost light reflected from the side surface inside the light guide member and the like are easily noticeable. In particular, ghost light reflected from the side surface of the light guide member becomes a problem because it appears closer to the display image in the field of view as the cross-sectional size of the light guide member is reduced. For this reason, in Patent Document 1, grooves are formed at different positions on the two opposing surfaces of the transparent substrate where the image light is reflected, and unnecessary reflected light in the transparent substrate for light guide is reflected and removed. Yes.

JP2007-286317A

  However, in the transparent substrate according to Patent Document 1, the surface on which the groove can be formed is limited to the two side surfaces, that is, the surface on the observer side and the surface on the opposite side, and the light guide direction (for image light) in which the groove can be formed. Since the position (traveling direction) is also limited, there is a concern that sufficient stray light and ghost light reduction effects cannot be obtained.

  Accordingly, an object of the present invention made by paying attention to these points is to provide a light guide prism that can be used as a light guide member and reduces stray light and ghost light caused by reflection on the inner surface, and an image display using the same. Is to provide a device.

The invention of the light guide prism that achieves the above object is as follows.
A light guide prism that guides image light from the display element to the eyeball of the observer, and displays a virtual image of the display element in the visual field of the observer,
At least four side surfaces arranged so as to surround the optical path of the image light incident from one end;
A reflecting surface for reflecting the image light guided by the at least four side surfaces;
An emission surface for emitting the image light reflected by the reflection surface toward an eyeball of an observer,
A V-shaped groove is formed in at least one side surface in a direction along the inclination of the reflection surface in the vicinity of the reflection surface.

  The V-shaped grooves may be formed on a pair of side surfaces that are opposed to each other among the at least four side surfaces and that are substantially orthogonal to the reflecting surface.

The invention of another light guide prism that achieves the above object is as follows.
A light guide prism that guides image light from the display element to the eyeball of the observer, and displays a virtual image of the display element in the visual field of the observer,
At least four side surfaces arranged so as to surround the optical path of the image light incident from one end;
A reflecting surface for reflecting the image light guided by the at least four side surfaces;
An emission surface for emitting the image light reflected by the reflection surface toward an eyeball of an observer,
At least one side surface is formed with a V-shaped groove provided at an inclined angle excluding orthogonal to the traveling direction of the image light in the surface of the side surface .

The invention of an image display device that achieves the above object is as follows.
A display element for emitting image light;
A light guide prism that guides image light from the display element to an observer's eyeball and displays a virtual image of the display element in the observer's field of view so as to surround the optical path of the image light incident from one end. The arranged at least four side surfaces, the reflection surface that reflects the image light guided by the at least four side surfaces, and the image light reflected by the reflection surface are emitted toward the eyeball of the observer. A light guide prism having an exit surface, wherein at least one side surface is formed with a V-shaped groove in a direction along the inclination of the reflection surface in the vicinity of the reflection surface;
The display device and the light guide prism are provided with a support unit for fixing and supporting the display element and the light guide prism on the head of an observer.

  According to the present invention, the outer periphery of the image light passes through the vicinity of the V-shaped groove twice before and after the reflecting surface, and a light guide prism capable of obtaining a high stray light and ghost light removal effect, and The used image display device can be provided.

FIG. 1 is a perspective view illustrating an appearance of an image display apparatus according to a first reference example. FIG. 2A is a front view of the optical system of the image display apparatus of FIG. 1 viewed from the eyeball side. FIG. 2B is a plan view of the optical system of the image display apparatus of FIG. FIG. 2C is a side view of the optical system of the image display apparatus of FIG. 1 viewed from the display element side. FIG. 3 is an enlarged cross-sectional view of the prism groove provided on the first side surface of FIG. FIG. 4 is a diagram for explaining the relationship between the viewing angle of the display element of FIG. 2, the frame formed by the edge of the prism groove, and the entrance window of the light guide prism. FIG. 5A is a front view of the optical system of the image display device of the second reference example as viewed from the eyeball side. FIG. 5B is a plan view of the optical system of the image display apparatus of the second reference example. FIG. 5C is a side view of the optical system of the image display apparatus of the second reference example as viewed from the display element side. FIG. 6A is a front view of the optical system of the image display device of the third reference example as viewed from the eyeball side. FIG. 6B is a plan view of the optical system of the image display device of the third reference example. FIG. 6C is a side view of the optical system of the image display apparatus of the third reference example as viewed from the display element side. FIG. 7A is a front view of the optical system of the image display device of the fourth reference example as viewed from the eyeball side. FIG. 7B is a plan view of the optical system of the image display apparatus of the fourth reference example. FIG. 8A is a front view of the optical system of the image display apparatus according to the embodiment as viewed from the eyeball side. FIG. 8B is a plan view of the optical system of the image display apparatus according to the embodiment. FIG. 9 is a front view showing an optical system of an image display apparatus of a fifth reference example. FIG. 10 is a diagram for explaining an optical system of an image display apparatus according to a sixth reference example. Fig.11 (a) is the front view which looked at the modification of the incident side edge part of a light guide prism from the eyeball side. FIG. 11B is a plan view of a modification of the incident side end of the light guide prism.

  Embodiments of the present invention will be described below with reference to the drawings.

(First Reference Example)
FIG. 1 is a perspective view showing an appearance of an image display apparatus according to a first reference example of the present invention. This image display device 1 has a shape of glasses and is fixed to a support portion 2 for fixing and supporting the entire image display device on the observer's head, and a temple (a temporal frame) of the support portion 2 for display. A main body 3 in which an element 31 (see FIG. 2) is incorporated, and a light guide prism 5 that is supported at one end by the main body 3 and extends to the viewer's eyes when the other end is attached to the observer. .

  In addition to the display element 31, the main body 3 includes an electronic circuit for displaying an image on the display element 31, a communication function for receiving video data from the outside of the main body 3 by wire or wireless, and the like.

  2 is a diagram showing an optical system of the image display apparatus of FIG. 1, FIG. 2 (a) is a front view seen from the eyeball side, FIG. 2 (b) is a plan view, and FIG. 2 (c) is a display element. It is the side view seen from the side. The display element 31 is a liquid crystal display element, an organic EL element, or the like that displays an image to be observed, and is built in the main body 3. The image light of the image displayed on the display element 31 is configured to enter the incident surface 51 of the light guide prism 5. It is desirable to provide a protective window (not shown) for protecting the display element 31 between the display element 31 and the incident surface 51 of the light guide prism 5.

  The light guide prism 5 is a prism long in one direction made of a transparent resin. The light guide prism 5 includes an incident surface 51 and a reflecting surface 52 at both ends in the longitudinal direction, which is the traveling direction of the image light, and surrounds the optical path of the image light between the incident surface 51 and the reflecting surface 52. The first side surface 53a, the second side surface 53b, the third side surface 53c, and the fourth side surface 53d are formed, and the emission surface 54 is formed on the second side surface. In a state where the observer wears the image display device 1, the first side surface 53a is located on the opposite side of the surface facing the front of the observer, and the second side surface 53b is the surface facing the front of the observer. . The third side surface 53c is an upper surface of the light guide prism, and the fourth side surface 53d is a lower surface of the light guide prism. That is, the first side surface 53a and the second side surface 53b are surfaces facing each other, and the third side surface 53c and the fourth side surface 53d are surfaces facing each other.

  In FIG. 2, the first to fourth side surfaces 53 a to 53 d are configured as flat surfaces and are substantially orthogonal to the incident surface 51. However, the first to fourth side surfaces 53a to 53d may have some curvature, and the incident surface 51 side may be configured to be wider than the reflection surface 52 side. For example, the distance between the third side surface 53c and the fourth side surface 53d can be made narrower on the reflecting surface 52 side than on the incident surface 51 side. Further, the width of the first and second side viewed from the observer's eyeball is preferably narrower than 4 mm, which is the average human pupil diameter, and does not hinder the observation of the outside world ahead of the light guide prism 5. Is set as follows. Alternatively, in order to display an image larger in the field of view, the width may be about 4 to 9 mm.

  The reflecting surface 52 is formed as an inclined surface inclined about 45 ° with the inner surface facing the viewer side with respect to the longitudinal direction of the light guide prism 5. The reflection surface 52 is formed as a mirror surface by aluminum sputtering or the like so that the image light traveling in the longitudinal direction in the light guide prism 5 is totally reflected. Depending on the conditions such as the refractive index of the material of the light guide prism 5 and the angle of the reflection surface, the total reflection surface can be formed without coating the surface with a reflection film.

  In addition, an exit surface 54 is provided in a portion adjacent to the reflecting surface 52 of the second side surface 53b. The exit surface 54 is formed as a convex surface located on the optical path of the image light reflected by the reflecting surface 52 to the eyeball. The exit surface 54 is formed integrally with the light guide prism 5. By integrally molding using resin, the light guide prism 5 can be manufactured in large quantities and at low cost. However, the emission surface 54 can be formed by bonding a plano-convex lens on the second side surface 53b formed as a flat surface. 2 and the subsequent drawings, the optical axis of the exit surface 54 is indicated by a one-dot chain line. The optical axis is bent at the reflecting surface 52 and passes through the center of the display element 31. Between the reflection surface 52 and the incident surface 51, the direction of the optical axis coincides with the longitudinal direction of the light guide prism 53.

  On the first to fourth side surfaces 53a to 53d of the light guide prism 5, prism grooves 61a to 61d each having a V-shaped cross section extend in a direction perpendicular to the longitudinal direction. Each of the prism grooves 61a to 61d is connected to the prism groove on the adjacent side surface, and is formed so as to go around the optical path of the image light through the four side surfaces 53a to 53d of the light guide prism 5 as a whole. Yes.

The prism grooves 61 a to 61 d are formed by two groove surfaces that sandwich an edge cut into each side surface of the light guide prism 5. FIG. 3 is an enlarged cross-sectional view of the prism groove 61a provided on the first side surface 53a of FIG. The prism groove 61a is composed of two groove surfaces S 1 and S 2 . The inclination angles θ 1 and θ 2 of the groove surfaces S 1 and S 2 allow stray light and ghost light generated in the light guide prism to be transmitted to the outside of the light guide prism 5 or directed into the light guide prism. It is designed to be removed by reflecting and transmitting from the other side. For this reason, the V-shaped cross section of each of the prism grooves 61a to 61d is not necessarily symmetrical with respect to the incident surface side and the reflection surface side. Note that undesirable light caused by reflection at an undesired position in the light guide prism is referred to as stray light, and in particular, light that generates an undesirable image other than a regular image to be observed is referred to as ghost light.

FIG. 4 is a diagram for explaining the relationship between the display element of FIG. 2, the frame formed by the edge of the prism groove, and the viewing angle of the entrance window of the light guide prism. The optical system of FIG. The bending by 52 is schematically shown in a straight line. In FIG. 4, Dθ, Vθ and Pθ are respectively the viewing angle of the display area of the display element, the viewing angle of the area formed by connecting the V-shaped edges of the prism grooves, and the entrance window frame of the light guide prism. The viewing angle is shown. These viewing angles can be confirmed by drawing a line connecting the center of the exit surface 54 and the outer peripheral edge of each region. Here, Dθ, Vθ and Pθ are
Dθ <Vθ <Pθ
It is formed to satisfy the relationship. In the example of FIG. 4, the angle viewing angle is a viewing angle in the horizontal direction (perpendicular to the first side surface 53a and the second side surface 53b), but the light guide prism has a viewing angle in the vertical direction. It is preferable to satisfy the same relationship.

  Since it is configured as described above, the image light emitted from the display element 31 of the main body unit 3 passes through the incident surface 51 of the light guide prism 5 and enters the light guide prism 5. The image light incident on the light guide prism 5 is guided in the longitudinal direction in the light guide prism 5, reflected by the reflecting surface 52, and emitted from the exit surface 54 toward the viewer's eyeball. Since the exit surface 54 has a positive refractive power, when viewed from the observer side, the image displayed on the display element 31 is displayed in the field of view as an enlarged virtual image.

  Further, a part of the image light emitted from the display element 31 is reflected at an undesired position on the first to fourth side surfaces 53a to 53d when there is no prism groove 61a to 61d, and generates stray light or ghost light. There is a risk of causing it. However, since the light guide prism 5 of the present invention has the prism grooves 61a to 61d formed in the first to fourth side surfaces 53a to 53d, respectively, stray light and ghost light are removed to the outside of the light guide prism 5, and contrast is increased. And the appearance of ghost images on the top, bottom, left and right of the display screen can be prevented. Also, the prism grooves 61a to 61d are arranged on the first to fourth side surfaces 53a to 53d so as to go around the optical path of the image light, so that stray light and ghost light are more reliably detected at the longitudinal position. Can be removed.

Further, as shown in FIG. 4, Dθ, Vθ, and Pθ are respectively set to the viewing angle of the display area of the display element, the viewing angle of the area formed by connecting the V-shaped edges of the prism grooves, and the light guide. When the viewing angle of the incident window frame of the prism is set, Dθ, Vθ and Pθ are
Dθ <Vθ <Pθ
Therefore, the image light from the display area of the display element 31 is not vignetted by the prism grooves 61a to 61d, and is generated on the side surface between the prism grooves 61a to 61d and the incident surface 51. Light can be cut.

  As described above, according to the present reference example, the V-shaped prism grooves 61a to 61d are formed on the four side surfaces 53a to 53d of the light guide prism 5 surrounding the optical path of the image light. It is possible to reduce stray light and ghost light due to reflection on each inner surface of the. Furthermore, since the prism grooves 61a to 61d are formed so as to go around the four side surfaces 53a to 53d, stray light and ghost light can be more reliably cut. Further, by satisfying the relationship of Dθ <Vθ <Pθ, it is possible to prevent effective image light from being vignetted by the prism grooves.

(Second reference example)
5A and 5B are diagrams showing an optical system of an image display apparatus according to a second reference example. FIG. 5A is a front view seen from the eyeball side, FIG. 5B is a plan view, and FIG. It is the side view seen from the display element side. The light guide prism 5 of the second reference example is a pair of light guide prisms 5 provided in the first side surface 53a and the second side surface 53b in place of the prism grooves 61a to 61d in the light guide prism 5 of the first reference example of FIG. Prism grooves 62a and 62b (first pair of grooves) are formed at positions facing each other, and another pair of prism grooves 62c and 62d (second pair) provided on the third side surface 53c and the fourth side surface 53d. Are formed at positions facing each other. Here, the prism grooves 62 a and 62 b are spaced apart from the prism grooves 62 c and 62 d on the reflective surface 52 side in the longitudinal direction of the light guide prism 5. Since other configurations are the same as those of the first reference example, the same or corresponding components are denoted by the same reference numerals and description thereof is omitted.

  According to the present reference example, since the V-shaped prism grooves 62a to 62d are formed on the four side surfaces 53a to 53d of the light guide prism 5 surrounding the optical path of the image light, respectively, similarly to the first reference example, the light guide is performed. Stray light and ghost light due to reflection on each side of the prism 5 can be reduced. Further, since the longitudinal positions of the prism grooves 62a and 62b and the prism grooves 62c and 62d are shifted, the resin fluidity is good when the light guide prism 5 is resin-molded, and the first to fourth side surfaces 53a to 53a- The accuracy of each optical surface 53d can be improved.

(Third reference example)
6A and 6B are diagrams illustrating an optical system of an image display apparatus according to a third reference example. FIG. 6A is a front view as viewed from the eyeball side, FIG. 6B is a plan view, and FIG. It is the side view seen from the display element side. The light guide prism 5 of the third reference example has prism grooves 62a to 62d extending on the first to fourth side faces 53a to 53d so as to cross the side faces of the light guide prism 5 of the second reference example of FIG. Instead, prism grooves 63a to 63d shorter than the width in the direction orthogonal to the longitudinal direction of the first to fourth side surfaces 53a to 53d are formed. Each prism groove 63a-63d is formed in the surface of the 1st-4th side surfaces 53a-53d, respectively, and it is to the corner | angular part between the mutually adjacent side surfaces of the 1st-4th side surfaces 53a-53d. It does not extend.

Further, the width of any side surface (for example, the second side surface 53b) of the light guide prism 5 is Pw, the length of the prism groove (prism groove 63b) formed on the side surface is Vw, and the effective area of the display element is When the width in the direction corresponding to the side surface is Dw,
Dw <Vw <Pw
Configure to meet.
Since other configurations are the same as those of the second reference example, the same or corresponding components are denoted by the same reference numerals, and description thereof is omitted.

  With the above configuration, the length of the prism grooves 63a to 63d is made longer than the effective diameter of the display element 31 in the corresponding direction, so that ghost light can be cut without leakage. In addition, the length of the prism grooves 63a to 63d is made shorter than the width of the corresponding side surfaces 53a to 53d of the light guide prism 5, and no grooves are provided in the corner portions between the adjacent side surfaces of the light guide prism 5. Therefore, it is possible to secure a holding force when the light guide prism 5 is attached to the main body 3 and used. Further, even when the light guide prism 5 is slid in the longitudinal direction with respect to the main body 3 in order to adjust the diopter, the light guide prism 5 can be operated smoothly.

(4th reference example)
7A and 7B are diagrams showing an optical system of an image display apparatus according to a fourth reference example. FIG. 7A is a front view seen from the eyeball side, and FIG. 7B is a plan view. The light guide prism 5 of the fourth reference example is similar to the light guide prism 5 of the third reference example of FIG. 6 on the reflective surface 52 side than the prism grooves 63a and 63b on the third side surface 53c and the fourth side surface 53d. Further, prism grooves 64c and 64d (a third pair of grooves) are formed at positions facing each other. Here, the prism grooves 63c and 63d on the incident surface 51 side and the prism grooves 64c and 64d on the reflection surface 52 side are formed by changing the angles of the groove surfaces forming the V-shape. Specifically, the prism grooves 63c and 63d are designed to cut stray light and ghost light due to the image light from the display element 31, whereas the prism grooves 64c and 64d are the exit surface 54 and the reflection surface 53. It is designed to prevent back-incident light from the edge of the light from reaching the display element 31 and affecting the operation of the display element or reducing the contrast. In this case, the groove surfaces of the prism grooves 64c and 64d on the reflecting surface 54 side are inclined in the opposite direction to the groove surfaces of the prism grooves 63c and 63d on the incident surface side. In other words, for the prism grooves 63c, 63d, 64c, and 64d, in the same manner as shown in FIG. 3, the angles θ of the incident surface side groove surface S 1 and the reflection surface side groove surface S 2 with respect to the corresponding side surfaces 1, when defining the theta 2, the prism grooves 63c, 63d and the prism grooves 64c, with the 64d, the magnitude relationship between theta 1 and theta 2 are different. By doing so, the reverse incident light can be cut. Since other configurations are the same as those of the third reference example, the same or corresponding components are denoted by the same reference numerals, and description thereof is omitted.

  As described above, according to the present reference example, two pairs of prism grooves 63c, 63d and 64c, 64d are formed on the third and fourth side surfaces 53c, 53d, and the prism grooves 64c, 64d are formed with the reverse incident light. Therefore, in addition to the effect of the third reference example, adverse effects on the operation of the display element due to reverse incident light and a decrease in contrast can be prevented.

  Note that the prism grooves 64c and 64d can be used for further removal of stray light and ghost light instead of removal of back-incident light. In that case, the depth of each of the prism grooves 63c, 63d, 64c, and 64d is made shallower than that in the third reference example, and the same effect as when only the pair of prism grooves 63c and 63d is formed may be produced. it can. In addition, various effects can be obtained by providing a plurality of pairs of prism grooves and changing the angle of the groove surface according to the distance from the incident surface 51.

(Embodiment)
8A and 8B are diagrams illustrating an optical system of the image display apparatus according to the embodiment. FIG. 8A is a front view as viewed from the eyeball side, and FIG. 8B is a plan view. In the light guide prism 5 of FIG. 8, three prism grooves 65a, 65c, 65e are formed on the third side surface 53c in this order from the incident surface 51 side. These prism grooves 65a, 65c, 65e are formed at an angle rather than a direction perpendicular to the longitudinal direction of the light guide prism. In particular, the prism groove 65e is provided in the vicinity of the reflecting surface 52 along the inclination of the reflecting surface. Further, similar prism grooves 65b, 65d, and 65f are formed at positions facing the prism grooves 65a, 65c, and 65e on the fourth side surface 53d, respectively.

  With the configuration as described above, out of the image light emitted from the display element 31, the light deviating from the optical path is observed by the prism grooves 65 a to 65 f as shown in FIGS. 8A and 8B. When viewed from the top, it is deflected with various direction components such as a vertical direction and a front-rear direction. This makes it possible to cut ghost light more reliably. In addition, since the prism grooves 65e and 65f are formed at a position close to the reflecting surface 52 so as to follow the inclination of the reflecting surface 52, the outer periphery of the image light passes through the vicinity of the prism grooves 65e and 65f twice before and after the reflecting surface 51. It will pass, and the double stray light and ghost light removal effect will be obtained.

  In addition to the prism grooves 65a to 65f provided on the third side surface 53c and the fourth side surface 53d, the first side surface 53a and the second side surface 53b also have a prism groove perpendicular to the longitudinal direction and an angle with respect to the longitudinal direction. A prism groove with a mark may be formed.

(5th reference example)
FIG. 9 is a front view showing an optical system of an image display apparatus of a fifth reference example. In the light guide prism 5, prism grooves 66a to 66d are formed in the second side surface 53b at an angle with respect to the longitudinal direction. In this case, a prism groove is also formed at a position facing the first side surface 53a, but the illustration is omitted for simplicity. Of the prism grooves formed on the second side surface 53 b, the prism grooves 66 a and 66 b intersect two prism grooves that are angled in the opposite direction to the longitudinal direction of the light guide prism 5. In this way, the prism grooves 66a and 66b are symmetrical with respect to the longitudinal direction of the light guide prism by intersecting the prism grooves whose angles are opposite to each other. Thereby, stray light and ghost light can be cut evenly.

(Sixth reference example)
FIG. 10 is a diagram for explaining an optical system of an image display apparatus according to a sixth reference example. The reflection by the reflecting surface 52 is omitted, and the light guide prism 53 is schematically shown by extending linearly. The first side surface 53a and the second side surface 53b are respectively formed with four pairs of prism grooves perpendicular to the longitudinal direction of the light guide prism 5 and crossing the side surfaces 53a and 53b. Specifically, as shown in FIG. 10, the prism grooves 67a and 67b, the prism grooves 67c and 67d, the prism grooves 67e and 67f, and the prism grooves 67g and 67h form a pair in order from the incident surface 51 side. ing.

In FIG. 10, the range through which the effective light beam of the image light emitted from the display area of the display element 31 and passing through the emission surface 54 passes is shown as an area sandwiched between two straight lines l 1 and l 2. Yes. The prism grooves 67a to 67h are formed outside the range through which the effective light beam passes. Therefore, the prism grooves 67 a to 67 h are formed so that the depth is closer to the incident surface 51, and the depth is closer to the reflecting surface 52. Further, since the prism grooves are deep on the incident surface 51 side, the interval between the prism grooves is widened, and on the reflecting surface 52 side, the prism grooves are shallow, so the interval between the prism grooves is narrow. That is, in FIG. 10, the prism grooves 67a, the depth of 67b as d 1, the prism grooves 67 g, when the depth of 67h and d 2, the d 1> d 2. The prism grooves 67a, 67b and the prism grooves 67c, P 1 the distance between the 67d, when the prism grooves 67e, 67f and the prism grooves 67 g, the distance between 67h and P 2, the P 1> P 2 .

  With the configuration as described above, according to the present reference example, vignetting of the effective luminous flux of the image light emitted from the display element 31 due to the prism grooves 67a to 67h does not occur. Further, since the pitch between the prism grooves is narrowed as the depth of the prism grooves is shallow, stray light and ghost light can be efficiently removed.

Further, in FIG. 10, a pair of grooves (prism grooves 67a and 67b) arranged on the side close to the incident surface 51 is Va, and another pair of grooves (prism grooves 67c and 67d) adjacent to the exit surface 54 side of this groove. ) Is Vb, the angle of view by the width Vbw between the other pair of grooves Vb is Vbθ, and the side surfaces 53a and 53b on which the pair of grooves Va are formed are symmetrical with the edges of the pair of grooves Va. When the position is Va ′, the width between Va ′ is Va′w, and the viewing angle by the width Va′w is Va′θ,
Vbθ <Va'θ
The distance (P1) between the grooves Va and Vb is set so as to satisfy the above. By doing so, ghost light generated between the pair of grooves Va and the other pair of grooves Vb can be removed.

  In this reference example, a plurality of prism grooves similar to those of the first side surface and the second side surface may be formed on the third side surface and the fourth side surface. In this case, the same effect can be obtained by satisfying the conditions of the groove depth and the groove interval as described above. Further, the number of prism grooves on each side surface is not limited to four, and a larger number of prism grooves may be formed.

  In addition, this invention is not limited only to the said embodiment, Many deformation | transformation or a change is possible. For example, in the above-described embodiment, the incident side end of the light guide prism is provided with the incident surface orthogonal to the longitudinal direction of the light guide prism. However, the shape of the incident side of the light guide prism is not limited to this. Absent. FIG. 11 is a modification of the light guide prism 5 in which the incident side end of the light guide prism of the first reference example shown in FIG. 2 is changed. In this light guide prism 5, a reflection surface 71 inclined with respect to the longitudinal direction is formed at the incident side end portion, and an incident surface 76 is formed at the end portion of the second side surface 53 b on the near side of the observer. The display element 31 is arranged to face the incident surface 76. Thereby, the image light emitted from the display element 32 enters the light guide prism 5 from the incident surface 76, is reflected by the reflection surface 71, and is guided in the longitudinal direction in the light guide prism 5. Even if the incident side end portion is configured in this manner, the same operations and effects as those of the above embodiments can be obtained. In addition to this, the incident side end can have various configurations.

  In each of the above embodiments, the prism grooves formed on the first side surface and the second side surface of the light guide prism are arranged to face each other, and similarly, the third side surface and the fourth side surface are arranged. The grooves formed on the side surfaces are arranged to face each other. However, the present invention is not limited to this, and for example, grooves may be arranged at different positions in the longitudinal direction of the four side surfaces. Furthermore, the optical axis of the light guide prism does not need to be in the direction along the longitudinal direction. For example, the image light reflected a plurality of times on the first and second side surfaces in the light guide prism is reflected by the reflecting surface and emitted. You may comprise so that it may inject from a surface. In that case, the positions of the prism grooves on the first and second side surfaces are set to positions that do not block the optical path of the effective image light.

  Moreover, although the side surface of the light guide prism is configured by four surfaces, it is not limited thereto. For example, the shape which took the corner of the ridgeline part between each adjacent side surface, or was rounded is also contained. The light guide prism is formed of a transparent resin, but is not limited thereto, and may be formed of other transparent optical members such as glass. Furthermore, in the said embodiment, although the exit surface of the light guide prism shall be formed as a convex surface, it is not restricted to this. For example, the reflecting surface may be formed as a reflecting surface having a positive refractive power, and the exit surface may be a flat surface. Also in this case, the observer can observe an enlarged virtual image of the image displayed on the display element.

  The image display apparatus illustrated in FIG. 1 displays an image toward the observer's right eye, but can also be configured as an image display apparatus for the left eye or for both eyes. Furthermore, the image display device is not limited to the glasses type, and various forms for fixing to the head, such as fixing the main body portion and the light guide prism to a goggle or a helmet, are possible.

DESCRIPTION OF SYMBOLS 1 Image display apparatus 2 Support part 3 Main-body part 5 Light guide prism 31, 32 Display element 51 Incident surface 52 Reflective surface 53a, 73a 1st side surface 53b, 73b 2nd side surface 53c, 73c 3rd side surface 53d, 73d 3rd 4 side surfaces 54, 74 exit surface 61a-61d prism groove 62a-62d prism groove 63a-63d prism groove 64c, 64d prism groove 65a-65f prism groove 66a-66d prism groove 67a-67h prism groove 70 light guide prism 71 reflecting surface

Claims (4)

  1. A light guide prism that guides image light from the display element to the eyeball of the observer, and displays a virtual image of the display element in the visual field of the observer,
    At least four side surfaces arranged so as to surround the optical path of the image light incident from one end;
    A reflecting surface for reflecting the image light guided by the at least four side surfaces;
    An emission surface for emitting the image light reflected by the reflection surface toward an eyeball of an observer,
    A light guide prism in which a V-shaped groove is formed on at least one side surface in a direction along the inclination of the reflection surface in the vicinity of the reflection surface.
  2.   2. The V-shaped groove is a set of side surfaces opposed to each other among the at least four side surfaces, and is formed on a set of side surfaces substantially orthogonal to the reflecting surface, respectively. The light guide prism described in 1.
  3. A light guide prism that guides image light from the display element to the eyeball of the observer, and displays a virtual image of the display element in the visual field of the observer,
    At least four side surfaces arranged so as to surround the optical path of the image light incident from one end;
    A reflecting surface for reflecting the image light guided by the at least four side surfaces;
    An emission surface for emitting the image light reflected by the reflection surface toward an eyeball of an observer,
    A light guide prism having a V-shaped groove formed on at least one side surface at an inclined angle excluding orthogonal to the traveling direction of the video light within the side surface .
  4. A display element for emitting image light;
    A light guide prism that guides image light from the display element to an observer's eyeball and displays a virtual image of the display element in the observer's field of view so as to surround the optical path of the image light incident from one end. The arranged at least four side surfaces, the reflection surface that reflects the image light guided by the at least four side surfaces, and the image light reflected by the reflection surface are emitted toward the eyeball of the observer. A light guide prism having an exit surface, wherein at least one side surface is formed with a V-shaped groove in a direction along the inclination of the reflection surface in the vicinity of the reflection surface;
    An image display device comprising: a support portion for fixedly supporting the display element and the light guide prism on an observer's head.
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