JP2009128649A - Combiner optical system and wearable display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a combiner optical system and a wearable display device capable of preventing deterioration of appearance due to a polarization separation element appearing dark.
A combiner optical system 11 allows a p-polarized light component to be transmitted and reflects an s-polarized light component, and reflects a p-polarized light component transmitted through the polarized light separating element toward the polarized light separating element. And a quarter-wave plate 18 disposed between the reflecting member and the polarization separation element 16. The reflectance of the s-polarized component by the polarization separation element 16 is 0.2 or more and 0.8 or less.
[Selection] Figure 3

Description

  The present invention relates to a combiner optical that can show an external environment together with an image displayed on an image display surface by superimposing a light beam emitted from an image display surface on a light beam incident from the outside and irradiating the eyes of the observer. The present invention relates to a system and a wearable display device using the same.

  Conventionally, a combiner optical system used in, for example, a wearable display device that is worn on the head of an observer is known (see, for example, Patent Document 1).

  Such a combiner optical system includes a polarization beam splitter (hereinafter referred to as PBS) that is a polarization separation element that transmits the p-polarized component of the light beam emitted from the image display unit and reflects the s-polarized component. Further, the combiner optical system includes a reflecting member for reflecting the light transmitted through the PBS toward the PBS, and a quarter wavelength plate disposed between the reflecting member and the PBS. PBS is arrange | positioned so that the reflected light from a reflection member may be reflected toward an observer's eyes. The reflectance Rs of the s-polarized component by PBS is approximately 1.

  The p-polarized component of the light beam emitted from the image display unit and transmitted through the PBS is converted to circularly polarized light by transmitting through the quarter-wave plate, reflected by the reflecting member, and then incident on the quarter-wave plate again. As a result, it is converted into an s-polarized component. Thereafter, the s-polarized component emitted from the quarter-wave plate enters the PBS. At this time, since the reflectance Rs of the s-polarized component by PBS is approximately 1, almost all of the s-polarized component incident on PBS is reflected by PBS and enters the observer's eyes.

  Further, most of the s-polarized component of the light beam incident on the PBS from the outside is reflected by the PBS, but most of the p-polarized component of the light beam passes through the PBS and enters the observer's eye.

Thereby, the observer wearing the wearable display device can see the image displayed on the image display unit superimposed on the external image.
Japanese Patent No. 3260867

  However, since almost all of the s-polarized component of the light beam incident on the PBS is reflected by the PBS, for example, when light is incident on the PBS from the observer side toward the outside, only the p-polarized component is transmitted. However, it becomes almost half of the ambient light amount through which both the p-polarized component and the s-polarized component are transmitted. Therefore, when the wearable display device is viewed from the outside, the brightness of the PBS looks darker than the surrounding brightness, so that the PBS is conspicuous and poor in appearance.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a combiner optical system and a wearable display device that can prevent deterioration in appearance due to a polarization separation element such as PBS appearing dark.

  In order to solve the above-described problem, a combiner optical system according to the present invention transmits a p-polarized component of an incident light beam and reflects a s-polarized component of the light beam, and light transmitted through the polarized light separation device. And a quarter wave plate disposed between the reflecting member and the polarization separation element, the s-polarized component of the s-polarization component by the polarization separation element The reflectance is 0.2 or more and 0.8 or less.

  According to the present invention, since the reflectance of the s-polarized component by the polarization separation element is 0.2 or more and 0.8 or less, for example, the reflectance of the s-polarization component is 0.5 by the polarization separation element. In this case, 50% of the s-polarized light component incident on the polarization separation element is transmitted through the polarization separation element.

  For this reason, for example, when light is incident toward the side opposite to the reflection direction of the s-polarized component by the polarization separation element, a part of the s-polarization component of the light is transmitted through the polarization separation element. As a result, compared with the conventional case where the reflectance of the s-polarized light component by the polarization separation element is 1, the light amount per unit area of the light beam transmitted through the polarization separation element and the unit area of the light beam transmitted through the periphery thereof. The difference with the amount of light becomes smaller. That is, the contrast between the polarized light separating element and its surroundings is smaller than when the reflectance of the s-polarized light component by the polarized light separating element is 1.

  Therefore, when the combiner optical system according to the present invention is used in, for example, a wearable display device worn on the observer's head so that the polarization separation element reflects the s-polarized light component toward the observer, the wearable display. When the apparatus is viewed from the outside, it is possible to prevent the polarization separation element from appearing darker than the surrounding brightness.

  In order to solve the above problem, the wearable display device according to the present invention includes an image display unit on which an image to be presented to an observer's eye is displayed, and a p-polarized component of a light beam emitted from the image display unit. A polarization separation element that transmits and reflects the s-polarized light component of the light beam, a reflection member that reflects light transmitted through the polarization separation element toward the polarization separation element, the reflection member, and the polarization separation element; A quarter-wave plate disposed between the polarization separation element and the polarization separation element so as to reflect the s-polarization component toward the eye. The reflectance is 0.2 or more and 0.8 or less.

  According to the present invention, since the reflectance of the s-polarized component by the polarization separation element is 0.2 or more and 0.8 or less, for example, the reflectance of the s-polarization component is 0.8 by the polarization separation element. In this case, 20% of the s-polarized component incident on the polarization separation element is transmitted through the polarization separation element.

  From this, for example, when light is incident from the observer side of the polarization separation element toward the outside, a part of the s-polarized component of the light is transmitted through the polarization separation element. As a result, compared with the conventional case where the reflectance of the s-polarized light component by the polarization separation element is 1, the light amount per unit area of the light beam transmitted through the polarization separation element and the unit area of the light beam transmitted through the periphery thereof. The difference with the amount of light becomes smaller. That is, the contrast between the polarized light separating element and its surroundings is smaller than when the reflectance of the s-polarized light component by the polarized light separating element is 1.

  Therefore, when the wearable display device is viewed from the outside, it is possible to prevent the polarization separation element from appearing darker than the surrounding brightness.

  ADVANTAGE OF THE INVENTION According to this invention, the bad appearance like the past by the polarization splitting element appearing dark can be suppressed reliably.

  Hereinafter, the present invention will be described with reference to the illustrated embodiments.

  As shown in FIG. 1, the wearable display device 10 according to the present invention includes a combiner optical system 11 and an image display unit 12. The wearable display device 10 is worn on an observer's head (not shown) in order to present the image output from the image display unit 12 to the observer via the combiner optical system 11.

  As shown in FIG. 2, the image display unit 12 includes a display screen 13 on which an image to be presented to an observer is displayed, a light source 14 for illuminating the display screen from the back side, a display screen 13 and a light source 14. And a housing 15 for storing the.

  The display screen 13 is composed of a liquid crystal panel in the illustrated example. The light source 14 is composed of an LED in the illustrated example. The wavelength of the light beam emitted from the display screen 13 illuminated by the light source 14 is set to a predetermined wavelength. Further, the light flux from the display screen 13 is polarized, and the polarization direction is set to be p-polarized light having a vibration surface in a plane parallel to the paper surface of FIG.

  The combiner optical system 11 includes a polarization separation element 16, a reflection member 17, and a quarter wavelength plate 18. Further, the combiner optical system 11 includes, in the illustrated example, a light guide prism 20 disposed in front of the left eye 19 of the observer, and a front of the light guide prism (above the light guide prism 20 as viewed in FIG. 2). And a plate-shaped polarizing plate 21 for the left eye arranged in the above.

  The light guide prism 20 has a rectangular parallelepiped shape as a whole, and extends along the left-right direction of the wearable display device 10 (the left-right direction as viewed in FIG. 2 and the left-right direction of the observer's head). Are arranged as follows. In the illustrated example, the light guide prism 20 is coupled to the housing 15 of the image display unit 12 at one end 20a in the longitudinal direction. The refractive index nd of the light guide prism 20 at the d-line (wavelength 587 nm) is nd = 1.804 in the illustrated example.

  On the end surface of the one end portion 20 a of the light guide prism 20, an incident surface 20 b that receives light from the display screen 13 is formed. The incident surface 20b is positioned on the front side of a pair of parallel side surfaces in which the principal ray of the light beam from the display screen 13 is substantially perpendicular to the incident surface 20b and the light beam faces each other in the front-rear direction of the light guide prism 20. It is inclined at a predetermined angle toward the inside of the light guide prism 20 so as to enter the front surface 20c which is a side surface. The inclination angle of the incident surface 20b is set so that the incident angle when the light beam from the display screen 13 is incident on the front surface 20c is larger than the critical angle, and is 78 ° in the illustrated example. Thereby, the light beam incident on the front surface 20c is totally reflected on the front surface. That is, the front surface 20c constitutes a reflection surface that totally reflects the light beam that has entered the light guide prism 20 through the incident surface 20b toward the PBS 16.

  The light guide prism 20 is composed of two prisms 20e and 20f that are joined together so as to form a rectangular parallelepiped. A polarization separating element 16 is formed on the joint surface 20g of one prism 20e by vacuum-depositing a dielectric in the form of a multilayer film. That is, the polarization separation element 16 is provided inside the light guide prism 20. Further, the one prism 20e has an emission surface 20h on an end surface located on the opposite side to the joint surface 20g.

  In the illustrated example, the polarization separation element 16 is configured by a polarization boom splitter 16 (hereinafter referred to as PBS). The PBS 16 transmits the p-polarized component of the light beam and reflects the s-polarized component having a vibration surface in a plane perpendicular to the paper surface of FIG. The PBS 16 is inclined with respect to the front surface 20c and the rear surface 20d of the light guide prism 20 so that the rear edge 16a is located on the inner side of the light guide prism 20 with respect to the front edge 16b. ing. In the illustrated example, the inclination angle of the PBS 16 is set such that the incident angle when the light beam totally reflected by the front surface 20c enters the PBS 16 is 39 °. The magnitude of the incident angle of the light beam on the PBS 16 is defined in accordance with the reflection performance of the PBS 16 in order to surely exhibit the polarization separation function of the PBS 16.

  The reflectance Rs of the s-polarized component by the PBS 16 according to the present invention is 0.2 or more and 0.8 or less. The adjustment of the reflectance Rs of the PBS 16 is performed by, for example, changing the number of stacked dielectric films vacuum-deposited on the joint surface 20g of the one prism 20e, or changing the refractive index set for each dielectric film. Is done.

  FIG. 3 is a graph showing the relationship between the wavelengths of the s-polarized component and the p-polarized component by the PBS 16 and the reflectance Rs of the s-polarized component and the reflectance Rp of the p-polarized component by the PBS 16 according to this embodiment. The vertical axis of the graph in FIG. 8 indicates the reflectances Rs and Rp, and the horizontal axis indicates the wavelength. As shown in FIG. 3, the reflectance Rp is almost 0% regardless of the value of the wavelength of the p-polarized component. On the other hand, the reflectance Rs is approximately 50%, that is, 0.5 regardless of the value of the wavelength of the s-polarized component.

  As shown in FIG. 2, the quarter-wave plate 18 is provided on the emission surface 20h of the one prism 20e. As is well known in the art, the quarter-wave plate 18 causes a phase difference in the light beam incident on the quarter-wave plate. For example, when the light beam transmitted through the quarter-wave plate 18 is linearly polarized light, the light beam is converted into circularly polarized light, and when the light beam transmitted through the quarter-wave plate 18 is circularly polarized light, the light beam Is converted to linearly polarized light.

  The reflecting member 17 is made of a glass plate having a convex surface on one surface. The reflecting member 17 is disposed such that the other plane is opposed to the quarter-wave plate 18, and is fixed to the one prism 20 e via the quarter-wave plate 18. A concave mirror 17a is formed on the convex surface of the reflecting member 17 by, for example, metal deposition. The light beam that has passed through the quarter-wave plate 18 enters the reflecting member 17 through the plane and is reflected by the concave mirror 17a. That is, the reflecting member 17 is a well-known back mirror. The reflecting member 17 is inclined at an angle at which the light beam irradiated on the concave mirror 17a from the reflecting member 17 is reflected toward the PBS 16 and further irradiated to the left eye 19 of the observer as will be described later.

  The left-eye polarizing plate 21 is disposed substantially parallel to the light guide prism 20. Further, as shown in FIG. 1, the left-eye polarizing plate 21 is disposed adjacent to the right-eye polarizing plate 22 disposed in front of the right eye (not shown) of the observer. Connected to the board. Each of the left-eye polarizing plate 21 and the right-eye polarizing plate 22 is provided with a mounting tool 23 for mounting the mounting type display device 10 on the observer's head. The image display unit 12 is fixed to a mounting tool 23 attached to the left-eye polarizing plate 21. The directions of the polarization axes of the left-eye polarizing plate 21 and the right-eye polarizing plate 22 are the same as the polarization directions of the s-polarized components with respect to the PBS 16, respectively. Accordingly, each of the polarizing plates 21 and 22 allows transmission of the s-polarized component and blocks transmission of the p-polarized component.

  Further, in the illustrated example, a cemented convex lens 24 for correcting aberration is disposed between the light guide prism 20 and the image display unit 12. In the illustrated example, the cemented convex lens 24 is formed by cementing a biconvex lens and a plano-concave lens.

  The p-polarized component emitted from the display screen 13 of the image display unit 12 is collected by passing through the cemented convex lens 24 and is incident on the incident surface 20 b of the light guide prism 20. At this time, as described above, the p-polarized component from the display screen 13 is incident on the incident surface 20b perpendicularly, so that an asymmetric element with respect to image formation of the light beam is prevented.

  The p-polarized light component that has entered the light guide prism 20 through the incident surface 20 is totally reflected by the front surface 20 c of the light guide prism 20 toward the PBS 16. At this time, since the p-polarized component is totally reflected, the optical energy loss of the p-polarized component due to the reflection of the p-polarized component on the front surface 20c does not occur. The p-polarized component is totally reflected by the front surface 20c and then enters the PBS 16. At this time, as described above, since the PBS 16 allows the transmission of the p-polarized component, the p-polarized component incident on the PBS 16 transmits the PBS 16.

  The p-polarized light component that has passed through the PBS 16 is converted into a circularly-polarized light component by passing through the quarter-wave plate 18, and then condensed on the concave mirror 17 a and reflected by the concave mirror to become substantially parallel light. That is, the concave mirror 17a plays a well-known role as a convex lens.

  The circularly polarized light component reflected by the concave mirror 17a is converted into the s-polarized light component by passing through the quarter wavelength plate 18, and then enters the PBS 16 again. At this time, since the reflectance Rs of the s-polarized component by the PBS 16 is approximately 50% as described above, almost half of the s-polarized component incident on the PBS 16 is reflected by the PBS 16 and almost half of the remaining s-polarized component. Passes through the PBS 16.

  The s-polarized light component reflected by the PBS 16 is irradiated to the left eye 19 of the observer through a rear surface 20d that is a side surface located on the rear side of the light guide prism 20. At this time, since the circularly polarized light component reflected by the concave mirror 17 a is parallel light, the image displayed on the display screen 13 of the image display unit 12 is far from the left eye 19 in the left eye 19 of the observer. Appears to be displayed.

  Natural light emitted from the outside of the wearable display device 10 to the wearable display device first enters the left-eye polarizing plate 21 and the right-eye polarizing plate 22.

  In general, when natural light in a non-polarized state is reflected by the ground and the water surface, the reflected light is polarized in a direction perpendicular to the incident surfaces on the ground and the water surface. The polarization direction of the reflected light coincides with the polarization direction of the p-polarized component of the light beam incident on the PBS 16 of the wearable display device 10. As described above, the directions of the polarization axes of the left-eye polarizing plate 21 and the right-eye polarizing plate 22 are the same as the polarization direction of the s-polarized component.

  Therefore, by making the direction of the polarization axis of the left-eye polarizing plate 21 and the right-eye polarizing plate 22 to be the polarization direction of the s-polarized component, the reflected light as the p-polarized component is changed to the left-eye polarizing plate 21 and the right-eye polarizing plate 21. Since the light is blocked by the polarizing plate 22, the reflected light is prevented from being irradiated to the eyes of the observer.

  This prevents the reflected light from hindering the viewer from seeing the outside world, so the observer can see the outside world more clearly. Further, since the brightness of the outside world viewed from the observer is halved by blocking the p-polarized light component by the left-eye polarizing plate 21 and the right-eye polarizing plate 22, the display screen of the image display unit 12 with respect to the brightness of the outside world The brightness of the image displayed at 13 is increased. Thereby, the observer can visually recognize the image displayed on the display screen 13 of the image display unit 12 more clearly.

  On the other hand, the s-polarized component of natural light transmitted through the left-eye polarizing plate 21 enters the PBS 16. At this time, since the reflectance of the s-polarized component by the PBS 16 is approximately 0.5, almost half of the s-polarized component of the natural light transmitted through the left-eye polarizing plate 21 is attached to the image display unit 12 by the PBS 16. Reflected along the left-right direction of the display device 10, the remaining half of the s-polarized component of natural light passes through the PBS 16.

  As a result, the brightness of the outside world when the observer sees the outside world through the PBS 16 becomes brighter than when the reflectance Rs of the s-polarized component by the PBS 16 is 100%, that is, 1. It becomes easy to visually recognize the outside world.

  Therefore, an observer wearing the wearable display device 10 can see the image displayed on the display screen 13 of the image display unit 12 superimposed on the external image.

  When the light beam enters the light guide prism 20 from the observer side, most of the light beam irradiated to the region other than the region corresponding to the PBS 13 in the region of the rear surface 20d of the light guide prism 20 is guided. The prism 20 is transmitted to the left-eye polarizing plate 21 side. The light beam that has passed through the light guide prism 20 is irradiated to the polarizing plate 21 for the left eye. At this time, the s-polarized component of the light beam is allowed to pass through the left-eye polarizing plate 21, and the p-polarized component is blocked from passing through the left-eye polarizing plate 21. Accordingly, only the s-polarized component of the light beam incident on the light guide prism 20 is emitted from the left-eye polarizing plate 21 to the front of the wearable display device 10.

  On the other hand, the light beam irradiated to the region corresponding to the PBS 16 in the region of the front surface 20 c of the light guide prism 20 is incident on the light guide prism 20 and then irradiated to the PBS 16. At this time, most of the p-polarized component of the luminous flux is transmitted through the PBS 16, and half of the s-polarized component of the luminous flux is transmitted through the PBS 16. The p-polarized light component and the s-polarized light component transmitted through the PBS 16 are transmitted through the light guide prism 20 and then irradiated to the left-eye polarizing plate 21, and only the s-polarized light component is transmitted through the left-eye polarizing plate 21. The light is emitted from the ophthalmic polarizing plate to the front of the wearable display device 10.

  As a result, since the s-polarized component transmitted through the PBS 16 is emitted to the outside, when the light beam enters the light guide prism 20 from the observer side, the PBS 16 is irradiated as if the reflectance Rs is approximately 1. Compared to the case where almost all of the s-polarized light component of the emitted light is not emitted in front of the wearable display device 10, the amount of light per unit area of the light beam emitted from the region corresponding to the PBS 16 of the light guide prism 20 to the outside is large. Become.

  Therefore, the difference between the light amount per unit area of the light beam that has passed through the PBS 16 and the light amount per unit area of the light beam that has passed through the periphery thereof is smaller than when the reflectance Rs is approximately 1. As a result, the contrast between the PBS 16 and its surroundings is reduced, so that when the wearable display device 10 is viewed from the outside, it is suppressed that the brightness of the PBS 16 looks darker than the surrounding brightness.

  On the other hand, when the reflectance Rs by the PBS 16 is approximately 1, if the left-eye polarizing plate 21 that allows transmission of only the s-polarized component is disposed in front of the light guide prism 20, the light flux is observed in the light guide prism 20. When the light is incident from the person side, neither the s-polarized component nor the p-polarized component is emitted from the region corresponding to the PBS 16 of the light guide prism 20 to the outside. For this reason, the unit of the light beam transmitted through the PBS 16 is compared with the case where the left-eye polarizing plate 21 is not disposed, that is, when the p-polarized component is emitted from the region of the light guide prism 20 and the region around the region to the outside. The difference between the amount of light per area and the amount of light per unit area of the light beam that has passed around the area is increased. Therefore, when the wearable display device 10 is viewed from the outside, the brightness of the PBS 16 appears darker than the surrounding brightness as compared with the case where the left-eye polarizing plate 21 is not disposed.

  According to the present embodiment, as described above, the reflectance Rs of the s-polarized component by the PBS 16 is set to 0.5, so that the brightness of the PBS 16 when the wearable display device 10 is viewed from the outside is It is suppressed that it looks dark compared to the brightness. Thereby, even when the left-eye polarizing plate 21 that allows transmission of only the s-polarized component is disposed in front of the light guide prism 20, the appearance of the wearable display device 10 by the fact that the PBS 16 looks dark is improved. Badness can be reliably suppressed.

  When the value of the reflectance Rs by the PBS 16 is smaller than 0.2, the above-mentioned poor appearance can be more reliably suppressed, but since most of the s-polarized component reflected by the concave mirror 17a passes through the PBS 16, The light quantity of the s-polarized component irradiated to the left eye 19 of the observer is reduced. For this reason, the image presentation performance to the observer by the combiner optical system 11 is deteriorated.

  When the value of the reflectance Rs by the PBS 16 is larger than 0.8, the above-described appearance deterioration suppressing effect by reducing the reflectance Rs cannot be exhibited.

  On the other hand, according to the present embodiment, as described above, the reflectance Rs by the PBS 16 is 0.2 or more and 0.8 or less, so that the wearable type is not caused without deteriorating the image presentation performance. The poor appearance of the display device 10 can be reliably suppressed.

  In addition, according to the present embodiment, as described above, by causing the concave mirror 17a to function as a convex lens, the image displayed on the display screen 13 of the image display unit 12 is displayed at a position far from the eye. Can be seen by the observer's eyes. Thereby, compared with the case where the image displayed on the display screen 13 is displayed near the eye as in the case where the image displayed on the display screen 13 is presented to the observer by simply reflecting it with a flat mirror, It is possible to make the image easily visible to the eyes of the observer.

  Furthermore, according to the present embodiment, as described above, the light beam emitted from the display screen 13 of the image display unit 12 is totally reflected toward the PBS 16 by the front surface 20c located on the front side of the light guide prism 20. Therefore, the optical path of the light beam from the display screen 13 to the PBS 16 can be tilted forward of the light guide prism 20 within the light incident surface with respect to the optical path when the light beam from the display screen 13 is directly incident on the PBS 16. it can. Thereby, the PBS can be further inclined at an angle corresponding to the inclination angle of the optical path in a direction in which the gradient of the PBS 16 with respect to the front surface 20c and the rear surface 20d of the light guide prism 20 becomes gentle. Thereby, the arrangement space of the PBS 16 to be secured in the light guide prism 20 can be reduced in the front-rear direction of the light guide prism 20.

  Therefore, it is possible to reduce the thickness of the light guide prism 20 as compared with the case where the light beam incident through the incident surface 20b is directly irradiated on the PBS 16 without being totally reflected.

  As a result, the weight of the wearable display device 10 using the combiner optical system 11 is reduced, so that the stability of the posture of the wearable display device when the observer wears the wearable display device 10 is reliably improved. Can be made. In addition, when the observer wears the wearable display device 10, it is possible to reliably suppress the light guide prism 20 from interfering with wearing. Therefore, the usability of the wearable display device 10 can be improved with certainty.

  In Example 1, when it is considered that a part of the p-polarized component of the light beam irradiated to the PBS 16 is reflected without passing through the PBS 16, the following reflection characteristics can be set in the PBS 16.

  In Example 1, the upper limit of the reflectance Rs of the s-polarized component by the PBS 16 is 0.8, and the reflectance Rp is 0, that is, the transmittance for the p-polarized component to pass through the PBS 16 is 1.

  Here, each of the s-polarized component and the p-polarized component is half of the whole natural light. Therefore, when Rs = 0.8, the reflectance Rst of the s-polarized component with respect to the whole natural light is Rst = Rs × 0.5 = 0.8 × 0.5 = 0.4, and the p-polarized component with respect to the whole natural light The reflectance Rpt is Rpt = Rp × 0.5 = 0 × 0.5 = 0.

  Therefore, the reflectance R of the whole natural light in the PBS 16 is R = Rst + Rpt = 0.4 + 0 = 0.4. In order to suppress the PBS 16 from appearing dark, it is necessary to satisfy the relationship of reflectance R ≦ 0.4. .

  From the above, even when the p-polarized component is reflected by the PBS 16 as in the present embodiment, the reflectances Rs and Rp satisfy the relationship R = Rst + Rpt = Rs × 0.5 + Rp × 0.5 ≦ 0.4, respectively. There is a need. Therefore, the reflection characteristic of the PBS 16 is set so that the sum “Rs + Rp” of the value of the reflectance Rs and the value of the reflectance Rp satisfies the relationship of Rs + Rp ≦ 0.8.

  Therefore, for example, when the value of the reflectance Rs is 0.6, the value of Rp is set within a range of 0 ≦ Rp ≦ 0.2.

  According to the present embodiment, by setting the sum of the reflectance Rs of the s-polarized component and the reflectance Rp of the p-polarized component by PBS 16 to 0.8 or less, a part of the p-polarized component is PBS 16. Even in the case of reflection, deterioration of the appearance of the wearable display device 10 due to the PBS 16 appearing dark can be reliably suppressed.

  In Example 1 and Example 2, between the PBS 16 and the left-eye polarizing plate 21, as shown in FIG. 4, two light beams transmitted through the left-eye polarizing plate 21 toward the PBS 16 are orthogonal to each other. A wave plate 25 for giving an optical path difference to the polarization component can be arranged.

  In the illustrated example, the wave plate 25 guides the light so that the slow axis is inclined by 10 ° with respect to the polarization direction of the s-polarized component of the light beam transmitted through the left-eye polarizing plate 21 toward the light guide prism 20. It arrange | positions between the prism 20 and the polarizing plate 21 for left eyes. One surface 25a of the wave plate 25 is bonded to the front surface 20c of the light guide prism 20, and the other surface 25b of the wave plate 25 is bonded to a surface located on the light guide prism 20 side of the left-eye polarizing plate 21. ing.

  In the example shown in the figure, the value of the optical path difference d given to each polarization component by the wave plate 25 is set to 0.5λ. That is, the wave plate 25 functions as a half-wave plate.

  The s-polarized component of natural light transmitted through the left-eye polarizing plate 21 toward the light guide prism 20 exits from the left-eye polarizing plate 21 and enters the wave plate 25 at the same time. At this time, since the slow axis of the wave plate 25 is inclined by 10 ° with respect to the polarization direction of the s-polarized component as described above, the s-polarized component incident on the wave plate 25 By transmitting, it is converted into linearly polarized light rotated by −10 ° from the slow axis. The linearly polarized light emitted from the wave plate 25 enters the light guide prism 20 through one surface 25 a of the wave plate and the front surface 20 c of the light guide prism 20. Of the light flux that has entered the light guide prism 20, linearly polarized light that has entered the PBS 16 is divided into an s-polarized component and a p-polarized component by the PBS. The p-polarized light component passes through the PBS 16 and then exits from the light guide prism 20 toward the observer via the rear surface 20d. Half of the s-polarized component is reflected by PBS 16 toward the image display unit 12 along the left-right direction of the wearable display device 10, and the remaining half of the s-polarized component is transmitted through PBS 16 and then observed from within the light guide prism 20. Ejaculate towards the person.

  Thereby, compared with the case where the reflectance of the s-polarized component by the PBS 16 is 1, the brightness of the outside world when the observer sees the outside world through the PBS 16 becomes brighter.

  Further, when the light beam enters the light guide prism 20 from the observer side, the light beam applied to the PBS 16 among the light beams incident on the light guide prism 20 is divided into a p-polarized component and an s-polarized component by the PBS. After that, the p-polarized component and half of the s-polarized component pass through the PBS 16 and enter the wave plate 25. Of the light flux incident on the light guide prism 20, the remaining light flux that is not irradiated on the PBS 16 passes through the light guide prism 20 and then enters the wave plate 25.

  At this time, the p-polarized component and the s-polarized component of the light beam are converted by the wave plate 25 into linearly polarized light having a polarization direction different from the polarization direction of the s-polarized component. None of the s-polarized components can pass through the left-eye polarizing plate 21 that allows transmission of only the s-polarized component. For this reason, the light beam incident on the light guide prism 20 is not emitted from the left-eye polarizing plate 21 to the front of the wearable display device 10. Thereby, there is no difference between the luminous intensity in the PBS 16 in front of the left-eye polarizing plate 21 and the luminous intensity in the vicinity thereof. Therefore, when the wearable display device 10 is viewed from the outside, it is possible to more reliably prevent the brightness of the PBS 16 from appearing darker than the surrounding brightness by arranging the polarizing plate 21 for the left eye. it can.

  In the third embodiment, the wave plate 25 is arranged such that the slow axis is inclined by 10 ° with respect to the polarization direction of the incident light beam. Instead, the slow axis is the polarization of the incident light beam. The wave plate 25 can be arranged so as to be inclined at an angle other than 10 ° with respect to the direction.

  For example, when the slow axis of the wave plate 25 is inclined by 45 ° with respect to the polarization direction of the incident light beam, the s-polarized component of the natural light transmitted through the left-eye polarizing plate 21 is delayed by being transmitted through the wave plate 25. It is converted into linearly polarized light that is rotated by −45 ° from the phase axis, that is, p-polarized light component. A part of the p-polarized component emitted from the wave plate 25 is incident on the light guide prism 20, then passes through the PBS 16 and is emitted from the light guide prism 20 toward the observer. A part of the p-polarized component emitted from the wave plate 25 enters the light guide prism 20 and then exits from the light guide prism 20 toward the observer without entering the PBS 16.

  As a result, all the light beams incident on the PBS 16 from the outside are irradiated to the left eye 19 of the observer, so that the observer has seen the outside through the PBS 16 as compared with the case where the reflectance of the s-polarized component by the PBS 16 is 1. When the brightness of the outside world can be made brighter.

  Further, when the tilt angle of the slow axis with respect to the polarization direction of the incident light beam is 45 °, the p-polarized component and the s-polarized component incident on the light guide prism 20 from the observer side and transmitted through the PBS 16, and the light guide prism The remaining p-polarized light component and s-polarized light component of the light beam incident on 20 that are not irradiated to the PBS 16 are converted to the s-polarized light component and the p-polarized light component by passing through the wave plate 25.

  Thereafter, each of the s-polarized component and the p-polarized component enters the left-eye polarizing plate 21. At this time, the s-polarized component converted into the p-polarized component by the wave plate 25 is blocked from being transmitted through the left-eye polarizing plate 21, and the p-polarized component converted into the s-polarized component is transmitted to the left-eye polarizing plate 21. Permeation is allowed.

  As a result, the light quantity per unit area of the light beam that has passed through the PBS 16 and passes through the left-eye polarizing plate 21 and is emitted to the outside, and the left eye of the light beam that has passed through the light guide prism 20 without passing through the PBS 16. The amount of light per unit area that passes through the polarizing plate 21 and exits to the outside is approximately equal.

  Accordingly, when the wearable display device 10 is viewed from the outside, the brightness of the PBS 16 is substantially equal to the brightness of the surroundings thereof, and therefore, a polarizing plate 21 that allows transmission of only the s-polarized component is disposed in front of the light guide prism 20. As a result, it is possible to more reliably prevent the PBS 16 from appearing darker than the surrounding brightness.

  In the third embodiment, an example is shown in which the optical path difference d given to each polarization component of the incident light beam by the wave plate 25 is 0.5λ. Instead, an optical path difference d other than 0.5λ is used as the incident light beam. The wave plate 25 given to each of the polarization components can be applied to the present invention.

  In this case, it is preferable that the optical path difference d given to each polarization component of the incident light beam by the wave plate 25 is set within a range of 0.1λ ≦ d ≦ 0.6λ.

  When the value of the optical path difference d given to each polarization component of the incident light beam by the wave plate 25 is smaller than 0.1λ, the function of converting the s-polarized component and the p-polarized component of the incident light beam into other polarized light, respectively. Cannot be fully utilized. Further, when the optical path difference d given to each polarization component of the incident light beam by the wave plate 25 is larger than 0.6λ, so-called coloring due to optical interference of reflected light becomes conspicuous.

  On the other hand, by setting the value of the optical path difference d given to each polarization component of the incident light beam by the wave plate 25 within the range of 0.1λ ≦ d ≦ 0.6λ, the above function as the wave plate 25 is sufficiently obtained. And can prevent coloring.

  In each of the above-described embodiments, the example in which the reflectance Rs of the s-polarized component by the PBS 16 is 0.5 is shown. Instead, for example, as shown in FIG. 5, the reflectance Rs is set to 0.7. can do.

  Further, in each of the above-described embodiments, the PBS 16 is formed by vacuum-depositing a dielectric on the joint surface 20g of one prism 20e of the two prisms 20e and 20f joined together. Although shown, instead of this, the PBS 16 can be constituted by a plate-like member having a function of allowing the p-polarized component of the incident light beam to pass and reflecting the s-polarized component of the light beam. In this case, the plate-like member can be sandwiched between the two prisms 20e and 20f.

  Further, in each of the above-described embodiments, the example in which the polarization separation element 16 is configured by the PBS 16 has been described. Instead, the p-polarized component of the incident light beam is allowed to pass and the s-polarized component of the light beam is reflected. If possible, the polarization separation element 16 can be configured by a member other than the PBS 16.

  In each of the above-described embodiments, the example in which the reflecting member 17 has the concave mirror 17a has been described. Instead of this, the p-polarized component transmitted through the polarization separation element 16 may be reflected toward the polarization separation element 16. If possible, a reflecting member other than the reflecting member 17 having the concave mirror 17a can be applied to the present invention.

  Further, in each of the above-described embodiments, an example in which the incident light beam to the light guide prism 20 is totally reflected once by the front surface 20c, but instead, the incident light beam to the light guide prism 20 is changed to The front surface 20c can be totally reflected toward the rear surface 20d, and the rear surface 20c can be further totally reflected toward the PBS 16, or the incident light beam can be totally reflected several times alternately on the front surface 20c and the rear surface 20d. Then, the incident light beam can be irradiated to the PBS 16. In this case, the inclination direction of the incident surface 20b of the light guide prism 20 can be changed as appropriate.

  In each of the above-described embodiments, the example in which the light flux from the display screen 13 is totally reflected by the front surface 20c of the light guide prism 20 and then enters the PBS 16 is shown. Instead, the light flux from the display screen 13 is shown. Can be directly irradiated to the PBS 16 without being totally reflected in the light guide prism 20. In this case, the light guide prism 20 is not required, and the plate-like PBS as described above can be used as the PBS 16.

  Further, in each of the above-described embodiments, the combiner optical system 11 according to the present invention can be used for existing spectacles including a spectacle lens having refractive power so as to correct the visual acuity of the left and right eyes.

  In this case, the left and right eyeglass lenses can each play the role of the left eye polarizing plate 21 and the right eye polarizing plate 22, or separately from the left and right eyeglass lenses, the left eye polarizing plate 21 and A right-eye polarizing plate 22 can be provided.

  In each of the above-described examples, the combiner optical system 11 includes the left-eye polarizing plate 21 and the right-eye polarizing plate 22 is disposed adjacent to the left-eye polarizing plate. Instead, the left-eye polarizing plate 21 and the right-eye polarizing plate 22 can be dispensed with.

  In this case, when natural light is incident on the PBS 16 from the outside of the wearable display device 10, when the reflectance Rs of the s-polarized component by the PBS 16 is 0.5, the p-polarized component and half of the s-polarized component of the natural light are PBS 16. Transparent.

  As a result, as in the case where the left-eye polarizing plate 21 is arranged, the brightness of the external environment when the observer sees the external environment through the PBS 16 as compared with the case where the reflectance Rs of the s-polarized component by the PBS 16 is 1. Becomes brighter. Therefore, it becomes easy for the observer to visually recognize the outside world through the PBS 16.

  Further, when the light beam enters the light guide prism 20 from the observer side, the light beam applied to the region other than the region corresponding to the PBS 13 in the region of the rear surface 20 d of the light guide prism 20 is reflected in the light guide prism 20. To the front of the wearable display device 10.

  On the other hand, the light beam irradiated to the region corresponding to the PBS 16 in the region of the front surface 20 c of the light guide prism 20 is divided into a p-polarized component and an s-polarized component when irradiated to the PBS 16. Half of the p-polarized component and the s-polarized component are transmitted through the PBS 16 and then emitted from the light guide prism 20 to the front of the wearable display device 10. That is, in addition to the p-polarized component irradiated to the PBS 16, half of the s-polarized component is emitted to the outside.

  Thus, if the light amount per unit area of the light beam emitted from the region other than the region corresponding to the PBS 13 in the region of the light guide prism 20 is 1, the light amount per unit area of the light beam emitted from the region corresponding to the PBS 16 The amount of light is 0.75.

  Accordingly, since the contrast between the PBS 16 and its surroundings becomes small, it is possible to reliably suppress that the brightness of the PBS 16 looks darker than the surrounding brightness when the wearable display device 10 is viewed from the outside. .

1 is a perspective view schematically showing a wearable display device according to the present invention. It is explanatory drawing which shows schematically the combine optical system which concerns on this invention. It is a graph which shows the relationship between the reflectance Rs of the s-polarized component by the polarizing beam splitter which concerns on this invention, and the reflectance Rp of the p-polarized component, and each wavelength of s-polarized component and p-polarized component. It is explanatory drawing which shows roughly the combine optical system by which the wavelength plate is arrange | positioned between the light guide prism which concerns on this invention, and the polarizing plate for left eyes. 3 is a graph showing the relationship between the reflectance Rs of the s-polarized component and the reflectance Rp of the p-polarized component and the respective wavelengths of the s-polarized component and the p-polarized component by a polarizing beam splitter according to an embodiment different from the example shown in FIG. It is.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Wearable display apparatus 11 Combiner optical system 12 Image display part 16 Polarization separation element (polarization beam splitter)
17 Reflective member 17a Concave mirror 18 1/4 wavelength plate 20 Light guide prism 20b Incident surface 20c Reflective surface (front surface)
21 Polarizing member (Left-eye polarizing plate)
25 wave plate

Claims (14)

  A polarization separation element that transmits the p-polarization component of the incident light beam and reflects the s-polarization component of the light beam, a reflection member that reflects the light transmitted through the polarization separation element toward the polarization separation element, and A quarter-wave plate disposed between a reflecting member and the polarization separation element, and the reflectance of the s-polarized component by the polarization separation element is 0.2 or more and 0.8 or less. Combiner optical system.   The combiner optical system according to claim 1, wherein the sum of the reflectance value of the s-polarized component and the reflectance value of the p-polarized component by the polarization separation element is 0.8 or less.   The polarizing member is disposed on the opposite side of the light reflection direction by the polarization separation element, and the direction of the polarization axis of the polarizing member is the same as the polarization direction of the s-polarized component. The combiner optical system according to 1 or 2.   Between the polarization separation element and the polarization member, a wave plate for providing an optical path difference between two polarization components orthogonal to each other of a light beam transmitted through the polarization member toward the polarization separation element is disposed. The combiner optical system according to claim 3.   5. The combiner optical system according to claim 4, wherein a value of an optical path difference given to the light flux by the wave plate is 0.1λ or more and 0.6λ or less.   The combiner optical system according to any one of claims 1 to 5, wherein the reflecting member includes a concave mirror having a concave surface directed to the polarization separation element.   The light guide prism further includes a light guide prism having an incident surface on one end surface on which the light beam is incident and the reflection member provided on the other end surface, and the polarization separation element is provided in the light guide prism. 7. The method according to claim 1, further comprising a reflecting surface that totally reflects the light beam incident on the light guide prism through the incident surface toward the polarization separation element at least once. The combiner optical system described.   An image display unit on which an image to be presented to an observer's eye is displayed, a polarization separation element that transmits a p-polarized component of a light beam emitted from the image display unit and reflects an s-polarized component of the light beam, and the polarization separation A reflection member for reflecting the light transmitted through the element toward the polarization separation element; and a quarter-wave plate disposed between the reflection member and the polarization separation element. The s-polarized component is arranged to be reflected toward the eye, and the reflectance of the s-polarized component by the polarization separation element is 0.2 or more and 0.8 or less. Wearable display device.   9. The wearable display device according to claim 8, wherein a sum of a reflectance value of the s-polarized component and a reflectance value of the p-polarized component by the polarization separation element is 0.8 or less.   The polarizing member is disposed on a side opposite to the observer side of the polarization separating element, and the direction of the polarization axis of the polarizing member is the same as the polarization direction of the s-polarized component. The wearable display device according to 8 or 9.   Between the polarization separation element and the polarization member, a wave plate for providing an optical path difference between two polarization components orthogonal to each other of a light beam transmitted through the polarization member toward the polarization separation element is disposed. The wearable display device according to claim 10.   12. The wearable display device according to claim 11, wherein a value of an optical path difference given to the light flux by the wave plate is 0.1λ or more and 0.6λ or less.   The wearable display device according to any one of claims 8 to 12, wherein the reflection member includes a concave mirror having a concave surface directed to the polarization separation element.   A light guide prism having an incident surface on one end surface on which the light beam emitted from the image display unit is incident and having the reflection member provided on the other end surface; and the polarization separation element is provided in the light guide prism. The light guide prism has a reflection surface that totally reflects the light beam incident on the light guide prism through the incident surface at least once toward the polarization separation element. The wearable display device according to any one of the above.

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