Patent Description:
Among display devices for information appliances of the type worn on the body, the goggle type format which also allows the outside world to be seen is becoming mainstream. <FIG> is an external view showing a goggle type display (display device) worn by a viewer, and <FIG> is a drawing illustrating the general configuration of a conventional goggle type display and the optical path in the XY plane.

Here, the goggle type display <NUM> is for the right eye, and defines an XYZ coordinate system having its origin at the center of the right eye E of a viewer viewing into the distance. The Y direction is to the front of the viewer, the Z direction is above the viewer, and the X direction (set direction) is to the left of the viewer.

The goggle type display <NUM> has an appearance similar to goggles, and comprises an output unit (output optical system) <NUM> which outputs image display light L, a light guide (optical element) <NUM> which is a substrate that internally reflects the image display light L from the output unit <NUM> and guides it to the eye E of the viewer, and a frame part F to which the output unit <NUM> and light guide <NUM> are attached (for example, see patent literature <NUM>).

The output unit <NUM> has a housing as shown in <FIG>, and inside this housing, comprises an output mechanism including a transmissive liquid crystal display <NUM>, an optical system <NUM> and a light source (not illustrated), and a control unit (not illustrated) which outputs an image signal to the output mechanism.

The transmissive liquid crystal display <NUM>, based on an image signal from the control unit, forms an image in a display region perpendicular to the output direction, and outputs an image display light L.

Optical system <NUM> transmits the image display light L of the display region. Optical system <NUM> is furthermore arranged at a distance in front of the transmissive liquid crystal display <NUM>. As a result, the optical system <NUM> forms a virtual image of the observed object while transmitting image display light L of the display region.

Light guide <NUM> is a substrate fashioned from a light transmitting material such as glass (BK7, etc.), resin (polycarbonate, polymethacrylic acid (PMMA), cycloolefin, etc.) or the like and comprises a front surface 10a, a rear surface 10b located opposite the front surface 10a in the -Y direction, a right surface 10c, a left surface 10d located opposite the right surface 10c in the X direction, a top surface (not illustrated) and a bottom surface (not illustrated) located opposite the top surface in the Z direction, and furthermore has a beam splitter surface <NUM> formed inside. Here, the front surface 10a, the rear surface 10b, the top surface and the bottom surface are parallel to the X direction (set direction), while the left surface 10d is perpendicular to the X direction (set direction).

Furthermore, the right surface 10c is arranged so as to have an angle α to the X direction (set direction) when viewed from the Z direction. The output unit <NUM> is moreover arranged so as to cause the image display light L from the output mechanism to be inputted through the right surface 10c of the light guide <NUM> into the light guide <NUM> in a direction perpendicular to the right surface 10c. As a result, when image display light L from the output unit <NUM> enters inside the light guide <NUM> through the right surface 10c in a direction perpendicular to the right surface 10c, it advances substantially in the X direction (set direction).

The beam splitter surface <NUM> comprises three planar beam splitter surfaces, arranged in the X direction in the sequence: first beam splitter surface 11a, second beam splitter surface 11b, third beam splitter surface 11c. Furthermore, each of the beam splitter surfaces 11a through 11c are arranged at the same angle β to the X direction when viewed from the Z direction.

The first beam splitter surface 11a, second beam splitter surface 11b and third beam splitter surface 11c furthermore make it possible to reflect a predetermined fraction of the luminous flux of the inputted image display light L and to transmit a predetermined fraction of the luminous flux of the image display light L.

In such a goggle type display <NUM>, first, the image display light L of the display region from the output unit <NUM> is inputted into the light guide <NUM> through the right surface 10c. Here, the image display light L from the output unit <NUM> is inputted through the right surface 10c into the light guide <NUM> in a direction perpendicular to the right surface 10c, and the right surface 10c causes the image display light L of the display region from the output unit <NUM> to be inputted such that it advances substantially in the X direction (set direction).

The front surface 10a and rear surface 10b cause the image display light L of the display region to advance in the X direction (set direction) while reflecting it in alternation multiple times, thereby leading it to the first beam splitter surface 11a. The first beam splitter surface 11a then reflects a predetermined fraction of the luminous flux of the inputted image display light L and transmits a predetermined fraction of the luminous flux of the image display light L. Namely, the luminous flux of image display light La is guided to the eye E of the viewer.

Furthermore, the image display light L which has passed through the first beam splitter surface 11a reaches the second beam splitter surface 11b. Here, the second beam splitter surface 11b reflects a predetermined fraction of the luminous flux of the inputted image display light L and transmits a predetermined fraction of the luminous flux of the image display light L. Namely, the luminous flux of image display light Lb is guided to the eye E of the viewer.

Moreover, the image display light L which has passed through the second beam splitter surface 11b reaches the third beam splitter surface 11c. Here, the third beam splitter surface 11c reflects a predetermined fraction of the luminous flux of the inputted image display light L and transmits a predetermined fraction of the luminous flux of the image display light L. Namely, the luminous flux of image display light Lc is guided to the eye E of the viewer.

<CIT> discloses an optical element including a light guide plate that has therein a light transmissive flat plate member on which a transflective layer is formed, and a layer of a light transmissive adhesive or a light transmissive resin layer that uniformly covers the light guide plate. The refractive index of the layer of the adhesive or the resin layer is set to a refractive index different from that of the light guide plate. A first surface of the layer of the adhesive or the resin layer that is on the light exit surface side of the light guide plate is kept parallel with a second surface of the layer of the adhesive or the resin layer that is on the opposite side to the light exit surface side of the light guide plate.

<CIT> discloses an optical device, and also a method for producing same and a display device. The display device is provided with a frame to be worn on the head of a viewer, and an image display device attached to the frame. The image display device is provided with an image forming device and an optical device that forms a virtual image on the basis of light emitted from the image forming device. The light from the image forming device enters a pupil of the viewer via the optical device. The optical device is at least provided with: a first glass plate, a second glass plate facing the first glass plate, and an impact buffer layer sandwiched between the first glass plate and the second glass plate.

However, in a goggle type display <NUM> as described above, images with a shadow generated in a portion thereof would sometimes be seen. <FIG> is an example of an image in which a shadow seen by the viewer has been generated by the goggle type display <NUM> of <FIG>.

The present applicant investigated methods that would allow the viewer to properly see the image, and found that in a goggle type display <NUM> as described above, the size of the luminous flux of the image display light L (the display region) is limited by the size of the right surface 10c, and with a luminous flux size that has been limited by the size of the right surface 10c shown in <FIG>, regions occur in which luminous flux of image display light L propagating through the inside of the light guide <NUM> is not present (dropouts).

Here, <FIG> is a drawing illustrating the propagation range of luminous flux in the XY plane of the goggle type display <NUM> of <FIG>, where symbols A in the drawing indicate luminous flux dropouts.

The occurrence of such regions in which luminous flux of the image display light propagating through the inside of the light guide is not present (dropouts) could conceivably be prevented by increasing the size of the right surface of the light guide and increasing the size of the inputted luminous flux. <FIG> is a plan view illustrating a light guide in which the size of the right surface and the size of the light flux have been increased. However, this sort of light guide <NUM> has protruding parts and is thus difficult to manufacture and also makes the output unit <NUM> larger and heavier.

Furthermore, <CIT> discloses a display device comprising a first light guide for guiding image display light from a first output unit and a second light guide for guiding image display light from a second output unit, but since this device comprises two output units, it has the problem that it becomes larger and heavier. Furthermore, International Publication No. <CIT> discloses a display device comprising a first light guide which reflects image display light by means of four surfaces - a front surface, rear surface, top surface and bottom surface, in order to guide it to a second light guide, and a second light guide for guiding the image display light from the first light guide, but this has the problem of making the device large and heavy.

Thus, the applicant discovered how to arrange a substance (secondary substrate) across a beam splitter surface (secondary beam splitter) in front of the light guide (main substrate) in order to prevent dropouts of luminous flux of the image display light propagating through the inside of the light guide without providing protruding parts as in light guide <NUM> and without increasing the size of the output unit <NUM>, etc. It will be noted that the term beam splitter surface here refers to a surface having the function of reflecting a portion of the luminous flux and transmitting a portion of the luminous flux.

Accordingly, the image display light of the display region is reflected in alternation multiple time at the front surface and rear surface of the light guide, and when it reaches the front surface (secondary beam splitter surface) of the light guide, <NUM>% of the luminous flux of the image display light is not reflected, but rather a predetermined fraction of the luminous flux of the image display light is reflected and advances into the light guide, and a predetermined fraction of the luminous flux of the image display light is transmitted and advances into the secondary substrate. Namely, a difference (offset) occurs between the optical path of the image display light advancing inside the light guide and the optical path of the image display light advancing inside the secondary substrate (the image display light is split by the secondary beam splitter surface and is magnified), and the occurrence of regions where luminous flux of image display light propagating through the inside of the light guide is not present (dropouts) can be prevented by making use of this difference (offset).

According to a first aspect of the present invention there is provided an optical element as specified in claim <NUM>.

Here, "set direction" is an arbitrary direction determined in advance by the designer, etc., and could be, for example, the left direction, right direction, top direction or bottom direction.

With the optical element of the present invention, as described above, light is split and magnified by a secondary beam splitter surface, thus making it possible to prevent the occurrence of regions where luminous flux propagating through the inside of the main substrate is not present (dropouts).

The optical element according to the first aspect of the present invention may optionally be as specified in claim <NUM>.

In this case, when the right surface, etc. of the secondary substrate is formed diagonally, the concentration of complex processing on a single substrate can be avoided, so productivity is improved. Furthermore, when the width of the output mechanism is to be reduced, in the case where the image display light is inputted through the right surface of the main substrate, if the main substrate is made thinner, it is necessary to increase the number of main beam splitter surfaces in the main substrate in order to maintain the output range outputted by the main beam splitter surface, but by inputting the image display light through the right surface, etc. of the secondary substrate, the need to increase the number of main beam splitter surfaces of the main substrate is eliminated even if the secondary substrate is made thinner, so productivity is better.

In this case, it is possible to increase the degree of freedom in respect of the location where light enters inside the main substrate and secondary substrate and the location where it is outputted from inside the main substrate and secondary substrate.

In this case, a substrate of a fixed minimum thickness is arranged in front of the reflective surface, so luminous flux which is reflected two or more times from the reflective surface can be eliminated and the occurrence of stray light can be prevented.

According to a second aspect of the present invention there is provided a display device as specified in claim <NUM>.

With the display device of the present invention, regions where luminous flux is not present (dropouts) do not occur and the output mechanism can be made smaller and lighter.

Furthermore, as light progresses in a set direction, since there exists light which passes through the inside of the secondary substrate without being transmitted through the main beam splitter surface, the difference between the light quantity outputted to the outside from the first main beam splitter surface near the input location and the light quantity outputted to the outside from the Nth main beam splitter surface from the input location becomes smaller, making it possible to make the brightness (light quantity) more uniform.

According to a third aspect of the present invention, there is provided a photoreceptor device as specified in claim <NUM>.

With the photoreceptor device of the present invention, [sic] when optical components such as shown in <FIG> are used for a photoreceptor device, missing regions occur in the luminous flux (light flux which cannot be received), but with the photoreceptor device of the present invention, the total luminous flux reaching the main beam splitter surface can be received. Thus, the photoreceptor device of the present invention is able to sense objects of sensing located in any region of the luminous flux.

Modes of embodiment of the present invention will be described below using the drawings. It should be noted that the present invention is not limited to the mode of embodiment described below and includes various different configurations within the scope of the invention, set by the appended claims.

<FIG> is a drawing illustrating the general configuration and optical path in the XY plane of a goggle type display (display device) of the present invention, and <FIG> is drawing illustrating the propagation range of luminous flux in <FIG>. Similar parts have been assigned the same reference symbols as in goggle type display <NUM> described above.

The goggle type display <NUM> has an appearance similar to goggles, and comprises an output unit <NUM> which outputs image display light L, a light guide (optical element) <NUM> which internally reflects the image display light L from the output unit <NUM> and guides it to the eye E of the viewer, and a frame part F to which the output unit <NUM> and light guide <NUM> are attached.

The light guide unit <NUM> comprises a main substrate <NUM> with a main beam splitter surface <NUM> formed inside, a secondary substrate <NUM>, and a secondary beam splitter surface <NUM>.

The secondary substrate <NUM> has a front surface 20a, a rear surface 20b located opposite the front surface 20a in the -Y direction, a right surface 20c, a left surface 20d located opposite the right surface 20c in the X direction, a top surface (not illustrated), and a bottom surface (not illustrated) located opposite the top surface in the Z direction.

The front surface 20a and rear surface 20b are parallel to the X direction (set direction). Namely, the front surface 10a, rear surface 10b, front surface 20a and rear surface 20b are parallel to the X direction (set direction).

Furthermore, the gap between the front surface 20a and the rear surface 20b is a prescribed distance (thickness) determined by the designer using calculation formulas, simulation software and the like in consideration of the difference (offset) between the optical path of the image display light L which advances inside the main substrate <NUM> and the optical path of the image display light L which advances inside the secondary substrate <NUM>, so that dropouts of luminous flux propagating inside the main substrate <NUM> do not occur.

The material of the secondary substrate includes light transmitting materials such as glass (BK7), resin (polycarbonate, polymethacrylic acid (PMMA), cycloolefin, etc.) or the like, where from the standpoint of ease of manufacturing, change in response to temperature, etc., glass is preferable, and from the standpoint of safety, such as resistance to breaking during use, polycarbonate is preferable. It will be noted that for the material of the main substrate and the secondary substrate, glass types of different refractive index, mechanical strength, etc. may be combined, and also the main substrate and secondary substrate may be formed by combining different materials, such as by making the main substrate from glass and the secondary substrate from polycarbonate.

The secondary beam splitter surface <NUM> makes it possible to reflect a set fraction of the luminous flux of inputted image display light L and to transmit a set fraction of the luminous flux of the image display light L.

The set fractions of light reflected and transmitted by the secondary beam splitter surface are fractions set by the designer using calculation formulas, simulation software and the like, so that the brightness of the area where dropouts of luminous flux propagating inside the main substrate <NUM> have been eliminated will be more uniform with the brightness of the other areas, being preferably <NUM>% or greater and <NUM>% or less, for example, <NUM>%, etc..

Furthermore, the secondary beam splitter surface <NUM> may be formed for example on the rear surface 20b of the secondary substrate <NUM> through optical coating, with the front surface 10a of the main substrate <NUM> being bonded to the rear surface 20b of the secondary substrate <NUM>, which is preferable from the standpoint of facilitating fixation of the elements, and moreover may be arranged between the front surface 10a of the main substrate <NUM> and the rear surface 20b of the secondary substrate <NUM> by being directly bonded (optical contact, anodic bonding, diffusion bonding, ambient temperature bonding, thermal bonding, fluoric acid bonding, etc.), which is preferable from the standpoint of eliminating the need for adhesive with a predetermined refractive index.

It should be noted that the secondary beam splitter surface <NUM> may be formed by making use of reflection occurring due to a combination of materials of different refractive indices for the main substrate <NUM> and secondary substrate <NUM>, and may also be formed by filling the space between the main substrate <NUM> and secondary substrate <NUM> with a medium such as adhesive, air or oil, and making use of reflection generated due to the difference between the refractive index of that medium and the refractive index of the main substrate <NUM> and secondary substrate <NUM>.

In such a goggle type display <NUM>, first, image display light L of the display region from the output unit <NUM> is inputted inside the main substrate <NUM> through the right surface 10c. Here, the image display light L from the output unit <NUM> is inputted inside through the right surface 10c in a direction perpendicular to the right surface 10c, and the right surface 10c causes the image display light L of the display region from the output unit <NUM> to be inputted such that it advances substantially in the X direction (set direction).

The front surface 10a and rear surface 10b reflect the image display light L of the display region multiple times in alternation, causing it to advance in the X direction (set direction). Here, the advancing image display light L reaches the secondary beam splitter surface <NUM> (front surface 10a), and the secondary beam splitter surface <NUM> (front surface 10a) reflects a set fraction of the luminous flux of the inputted image display light L and transmits a set fraction of the luminous flux of the image display light L. Namely, when the image display light L reaches the secondary beam splitter surface <NUM> (front surface 10a), a set fraction of the luminous flux of the image display light L advances inside the main substrate <NUM>, and a set fraction of the luminous flux of the image display light L advances inside the secondary substrate <NUM>.

Furthermore, the image display light L which has advanced inside the secondary substrate <NUM> is reflected by the front surface 20a and then reaches the secondary beam splitter surface <NUM> (front surface 10a). Thereupon, the secondary beam splitter surface <NUM> (front surface 10a) reflects a set fraction of the luminous flux of the inputted image display light L and transmits a set fraction of the luminous flux of the image display light L. Namely, a set fraction of the luminous flux of the image display light L advances inside the main substrate <NUM> and a set fraction of the luminous flux of the image display light L advances through the inside of the secondary substrate <NUM>.

Thereafter, the image display light L which has advanced through the inside of the main substrate <NUM> or the secondary substrate <NUM> reaches the first main beam splitter surface 11a. Here, the first main beam splitter surface 11a reflects a prescribed fraction of the luminous flux of the inputted image display light L and transmits a prescribed fraction of the luminous flux of the image display light L. Namely, the luminous flux of image display light La is guided toward the viewer.

Furthermore, the image display light L which has been transmitted through the first main beam splitter surface 11a or which has advanced through the inside of the secondary substrate <NUM> reaches the second main beam splitter surface 11b. Here, the second main beam splitter surface 11b reflects a prescribed fraction of the luminous flux of the inputted image display light L and transmits a prescribed fraction of the luminous flux of the image display light L. Namely, the luminous flux of image display light Lb is guided toward the viewer.

Moreover, image display light L which has been transmitted through the first main beam splitter surface 1la or through the second main beam splitter surface 11b or which has advanced through the inside of the secondary substrate <NUM> reaches the third main beam splitter surface 11c. Here, the third main beam splitter surface 11c reflects a prescribed fraction of the luminous flux of the inputted image display light L and transmits a prescribed fraction of the luminous flux of the image display light L. Namely, the luminous flux of image display light Lc is guided toward the viewer.

With the goggle type display <NUM> of the present invention, as described above, the image display light L is split and magnified by the secondary beam splitter surface <NUM>, making it possible to prevent the occurrence of regions where luminous flux propagating through the inside of the main substrate <NUM> is not present (dropouts). Furthermore, since the secondary substrate <NUM> is bonded to the front surface 10a of the main substrate <NUM>, the overall strength of the light guide unit <NUM> is improved. Moreover, when image display light L advances in the X direction (set direction), since there exists image display light L which passes through the inside of the secondary substrate <NUM> without being transmitted through the main beam splitter surfaces 11a and 11b, the difference between the light quantity outputted to the outside from the first main beam splitter surface 11a and the light quantity outputted to the outside from the third main beam splitter surface 11c becomes smaller, allowing the brightness (light quantity) to be made more uniform.

<FIG> is a drawing illustrating the general configuration and optical path in the XY plane of a goggle type display (display device) of the present invention, and <FIG> is a drawing illustrating the propagation range of luminous flux in <FIG>. Similar parts have been assigned the same reference symbols as in goggle type display <NUM> described above.

The goggle type display <NUM> has an appearance similar to goggles, and comprises an output unit <NUM> which outputs image display light L, a light guide unit (optical element) <NUM> which internally reflects the image display light L from the output unit <NUM> and guides it to the eye E of the viewer, and a frame part F to which the output unit <NUM> and light guide <NUM> are attached.

The light guide unit <NUM> comprises a main substrate <NUM>, secondary substrate <NUM> and secondary beam splitter surface <NUM>.

The main substrate <NUM> comprises a front surface 210a, a rear surface 210b located opposite the front surface 210a in the -Y direction, a right surface 210c, a left surface 210d located opposite the right surface 210c in the X direction, a top surface (not illustrated), and a bottom surface (not illustrated) located opposite the top surface in the Z direction, and furthermore has a reflective surface <NUM> and main beam splitter surface <NUM> formed inside. The front surface 210a and the rear surface 210b are parallel to the X direction (set direction).

The reflective surface <NUM> is arranged in the right part of the inside of the main substrate <NUM> and is arranged to have an angle β to the X direction when viewed from the Z direction. For the reflective surface <NUM>, a silver coating is applied to reflect the entire luminous flux of inputted image display light L in the X direction (set direction). It will be noted that the reflective surface is not limited to silver coating and may also be another metal coating (for example, aluminum coating), and may also be formed as a dielectric multilayer coating, not as a metal coating, or a different medium such as air may be used to the right of the reflective surface and the reflection generated by the refractive index difference thereof may be utilized.

The secondary beam splitter surface <NUM> makes it possible for a set fraction of the luminous flux of the inputted image display light L to be reflected and for a set fraction of the luminous flux of the image display light L to be transmitted.

Furthermore, the secondary beam splitter surface <NUM> is formed through optical coating on a prescribed region of the front surface 210a of the main substrate <NUM>, and the front surface 210a of the main substrate <NUM> and rear surface 20b of the secondary substrate <NUM> are directly bonded and are thereby arranged between a prescribed region of the front surface 210a of the main substrate <NUM> and a prescribed region of the rear surface 20b of the secondary substrate <NUM>.

Here, the prescribed region where the secondary beam splitter surface <NUM> is arranged is at a location such that image display light L is reflected by reflective surface <NUM> and is then reflected by the front surface 210a and is not reflected again by the reflective surface <NUM>. In this way, image display light L which is reflected two or more times by the reflective surface <NUM> is eliminated and the occurrence of stray light is prevented.

The output unit <NUM> is arranged such that image display light L from the output mechanism will be inputted inside through the front surface 20a of the secondary substrate <NUM> in a direction perpendicular to the front surface 20a. As a result, when image display light L from the output unit <NUM> is inputted inside through the front surface 20a in a direction perpendicular to the front surface 20a, it advances toward the reflective surface <NUM> of the main substrate <NUM>.

In this sort of goggle type display <NUM>, first, image display light L of the display region from the output unit <NUM> is inputted inside the secondary substrate <NUM> through the front surface 20a. Here, the image display light L from the output unit <NUM> is inputted inside through the front surface 20a in a direction perpendicular to the front surface 20a. The inputted image display light L then reaches the reflective surface <NUM>, and the reflective surface <NUM> reflects the image display light L of the display region substantially in the X direction.

The front surface 20a and rear surface 210b reflect the image display light L of the display region multiple times in alternation, causing it to advance in the X direction (set direction). Here, the advancing image display light L reaches the secondary beam splitter surface <NUM>, and the secondary beam splitter surface <NUM> reflects a set fraction of the luminous flux of the inputted image display light L and transmits a set fraction of the luminous flux of the image display light L. Namely, when the image display light L reaches the secondary beam splitter surface <NUM>, a set fraction of the luminous flux of the image display light L advances inside the main substrate <NUM>, and a set fraction of the luminous flux of the image display light L advances inside the secondary substrate <NUM>.

It will be noted that the thickness of the secondary substrate <NUM> and the region of the secondary beam splitter surface <NUM> are set in such a way that image display light L which has been reflected once by the reflective surface <NUM> will not enter the reflective surface <NUM> again after being reflected by the front surface 20a or secondary beam splitter surface <NUM>.

Furthermore, the image display light L which has advanced inside the secondary substrate <NUM> is reflected by the front surface 20a and then reaches the secondary beam splitter surface <NUM>. Thereupon, the secondary beam splitter surface <NUM> reflects a set fraction of the luminous flux of the inputted image display light L and transmits a set fraction of the luminous flux of the image display light L. Namely, a set fraction of the luminous flux of the image display light L advances inside the main substrate <NUM> and a set fraction of the luminous flux of the image display light L advances through the inside of the secondary substrate <NUM>.

Thereafter, the image display light L which has advanced through the inside of the main substrate <NUM> or the secondary substrate <NUM> reaches the first main beam splitter surface 11a, the second main beam splitter surface 11b and the third main beam splitter surface 11c. Here, the first main beam splitter surface 11a, the second main beam splitter surface 11b and the third main beam splitter surface 11c reflect a prescribed fraction of the luminous flux of the inputted image display light L and transmit a prescribed fraction of the luminous flux of the image display light L. Namely, the luminous flux of image display light La, Lb and Lc is guided toward the viewer.

With the goggle type display <NUM> of the present invention, as described above, since a secondary substrate <NUM> of a set minimal thickness is arranged in front of the reflective surface <NUM>, stray light which is reflected two or more times by the reflective surface <NUM> (for example, luminous flux which has been reflected by the reflective surface <NUM>, which is then reflected by the front surface 20a and is then reflected not by the rear surface 210b but again by the reflective surface <NUM>) is eliminated, and splitting and magnification are performed by the secondary beam splitter surface <NUM>, thereby making it possible to prevent the occurrence of regions where luminous flux propagating through the inside of the main substrate <NUM> is not present (dropouts). Furthermore, since the secondary substrate <NUM> is bonded to the front surface 210a of the main substrate <NUM>, the overall strength of the light guide unit <NUM> is improved. Moreover, by not including the secondary beam splitter surface <NUM> in the region where the viewer views the outside world through the light guide unit <NUM>, thereby separating the region through which the outside world is viewed from the region where the secondary beam splitter surface <NUM> is arranged, the effect of making the secondary beam splitter surface <NUM> not noticeable to the viewer is achieved.

<FIG> is a drawing illustrating the general configuration and optical path in the XY plane of a photoreceptor device of the present invention. Similar parts have been assigned the same reference symbols as in goggle type display <NUM> described above.

The photoreceptor device <NUM> comprises a photoreceptor unit (photoreceptor optical system) <NUM> which receives light, and a light guide unit (optical element) <NUM> which internally reflects light from the outside, guiding it to the photoreceptor unit <NUM>.

The photoreceptor unit <NUM> comprises a photoreceptor mechanism arranged opposite the right surface 10c and having a photoreceptor element <NUM> and optical system <NUM>; and a control unit (not illustrated) in which signals from the photoreceptor mechanism are inputted.

In such a photoreceptor device <NUM>, first, light from the outside is inputted inside the main substrate <NUM> through the rear surface 10b. The light then reaches first main beam splitter surface 11a, second main beam splitter surface 11b and third main beam splitter surface 11c. Here, the first main beam splitter surface 11a, the second main beam splitter surface 11b and the third main beam splitter surface 11c reflect a prescribed fraction of the luminous flux of the inputted light so that it advances substantially in the -X direction, and transmit a prescribed fraction of the luminous flux of the light.

The front surface 10a and rear surface 10b reflect the light multiple times in alternation, causing it to advance in the -X direction (set direction). Here, the advancing light reaches the secondary beam splitter surface <NUM> (front surface 10a), and the secondary beam splitter surface <NUM> (front surface 10a) reflects a set fraction of the luminous flux of the inputted light and transmits a set fraction of the luminous flux of the light. Namely, when the light reaches the secondary beam splitter surface <NUM> (front surface 10a), a set fraction of the luminous flux of the light advances through the inside of the main substrate <NUM>, and a set fraction of the luminous flux of the light advances inside the secondary substrate <NUM>.

Furthermore, the light which has advanced inside the secondary substrate <NUM> is reflected by the front surface 20a and then reaches the secondary beam splitter surface <NUM> (front surface 10a). Here, the secondary beam splitter surface <NUM> (front surface 10a) reflects a set fraction of the luminous flux of the inputted light and transmits a set fraction of the luminous flux of the light. Namely, a set fraction of the luminous flux of the light advances inside the main substrate <NUM> and a set fraction of the luminous flux of the light advances through the inside of the secondary substrate <NUM>.

Thereafter, light which has advanced through the inside of the main substrate <NUM> or which has advances through the inside of the secondary substrate <NUM> reaches the right surface 10c. The light outputted from the right surface 10c is then guided to the photoreceptor unit <NUM>.

With the photoreceptor device <NUM> of the present invention, as described above, the total luminous flux which reaches the first main beam splitter surface 11a, second main beam splitter surface 11b and third main beam splitter surface 11c can be received. Thus, the photoreceptor device <NUM> of the present invention is able to sense the object of sensing in whatever region of the luminous flux is may be present.

Claim 1:
An optical element (<NUM>) comprising a main substrate (<NUM>) fabricated from light transmitting material, whereof the front surface (10a) and rear surface (10b) are parallel to a set direction for reflecting image display light in alternation multiple times,
and having at least one main beam splitter surface (<NUM>) formed diagonally to said set direction inside said main substrate (<NUM>),
the optical element (<NUM>) being further characterized in that it comprises a secondary substrate (<NUM>) fabricated from light transmitting material, whereof the front surface (20a) and rear surface (20b) are parallel to said set direction whereby a gap is provided between the front surface (20a) and the rear surface (20b),
and a secondary beam splitter surface (<NUM>) having a transmittance of <NUM>% or greater to <NUM>% or less is arranged between the front surface (20a) of the secondary substrate (<NUM>) and the rear surface (10b) of said main substrate (<NUM>) or between the rear surface (20b) of the secondary substrate (<NUM>) and the front surface (10a) of said main substrate (<NUM>), whereby the secondary beam splitter surface is arranged to reflect a predetermined fraction of the luminous flux of the image display light to advance into the main substrate (<NUM>), and to transmit a predetermined fraction of the luminous flux of the image display light to advance into the secondary substrate such that in accordance with said gap an offset occurs between the optical path of the image display light advancing inside the main substrate and the optical path of the image display light advancing inside the secondary substrate across said gap to suppress an occurrence of regions where luminous flux of image display light propagating through the inside of the main substrate (<NUM>) is not present.