JP2022013157A - Video display device and video display system - Google Patents

Abstract

To provide a light guide plate type video display device and video display system capable of displaying a video having uniform brightness for a user.SOLUTION: There is provided a video display device that displays video, and that has a video projection module which makes a scan with light to generate video light, a video light duplication part which duplicates and emits the video light, and a light guide plate which duplicates and emits the video light from the video light duplication part. The light guide plate comprises a light input part that the video light impinges, and relational expression Dmin≤D×N holds for N which is the number of video light beams that the video light duplication part emits, D which is a spot diameter of the plurality of video light beams, emitted from the video light duplication part, at the light input part, and Dmin which is a minimum diameter size of the human pupil.SELECTED DRAWING: Figure 8

Description

The present invention relates to an image display device using a light guide plate.

An image display device using a light guide plate represented by a head mounted display (HMD) is known. By using a light guide plate, it is possible to realize a video display device having see-through properties. Further, since the light guide plate duplicates the image light and projects it to the user, a wide eye box (an area where the user can visually recognize the image) can be realized.

Further, in order to reduce the size of the image display device and improve the design, an image display device using a small image projection module such as a fiber scanning projector or a mirror scanning projector using a laser light source is known.

When the small image projection module as described above is used, since the spot diameter of the image light is small, the plurality of image lights output from the light guide plate do not overlap each other, or the overlap is insufficient. As a result, there is an image portion where the image light does not enter the user's pupil or the amount of light incident on the user's pupil is extremely small. Therefore, uneven brightness occurs in the displayed image, which causes a problem that the user cannot display an image having uniform brightness.

Patent Document 1 is a background technique in this technical field. Patent Document 1 describes an image display device equipped with an image light duplication unit that replicates image light between an image projection module and a light guide plate.

International Publication No. 2019/133188

However, Patent Document 1 does not describe the specific configuration of the video light duplication unit, and describes the conditions necessary for displaying an image having uniform brightness in the video light duplicated by the video light duplication unit. Therefore, there is a problem that the user cannot display an image having uniform brightness.

The present invention has been made in view of such a situation, and an object of the present invention is to provide a light guide plate type video display device and a video display system capable of displaying a video having uniform brightness for a user.

The present invention is, for example, an image display device for displaying an image, an image projection module that scans light to generate image light, an image light duplication unit that duplicates and emits image light, and an image. It has a light guide plate that duplicates and emits video light from the optical duplication unit, the light guide plate has an optical input unit for incident video light, and the number of video light emitted by the video light duplication unit is N. , When the spot diameter at the optical input section of the plurality of video lights emitted from the video light duplication section is D and the minimum diameter size of the human pupil is Dmin, the relational expression of Dmin ≤ D × N is satisfied. do.

According to the present invention, it is possible to provide a light guide plate type video display device and a video display system capable of displaying a video having uniform brightness for the user.

It is a block diagram which shows the structural example of the image display system in Example 1. FIG. It is a block diagram which shows the structural example of the image display device in Example 1. FIG. It is a figure which shows the application example when the image display device in Example 1 is used as an HMD. It is a figure which shows the example of the image projection module which can be adopted as the image display device in Example 1. FIG. It is a figure which shows the example of the light guide plate which can be adopted as an image display device in Example 1. FIG. It is a figure for demonstrating the optical path in which the image light of Example 1 propagates from an image projection module to a user. It is a figure for demonstrating the duplication interval of the image light duplication part in Example 1. FIG. It is a figure which shows the configuration example of the image display device in Example 1. FIG. It is a figure for demonstrating the image light duplication part in Example 1. FIG. It is a figure explaining the duplication interval which the image light duplication part in Example 1 duplicates the image light. It is a figure for demonstrating the modification of the image light duplication part in Example 1. FIG. It is a figure for demonstrating the image light duplication part and the duplication prism in Example 1. FIG. It is a figure which shows the configuration example of the image display device in Example 2. FIG. It is a figure for demonstrating the image light duplication part in Example 2. FIG. It is a figure which shows the modification of the image display device in Example 2. FIG.

Hereinafter, examples of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing a configuration example of a video display system in this embodiment. In FIG. 1, the video display system 110 includes a video display device 111, a control device 112, a video signal processing device 113, a power supply device 114, a storage device 115, a sensing device 116, a communication device 118, and a voice processing device 120.

The image display device 111 is a light guide plate type display device using a light guide plate typified by, for example, an HMD. The video display device 111 supplies a video signal generated by the video signal processing device 113 via the control device 112, and displays a video based on the video signal to the user. The details of the video display device 111 will be described later.

The control device 112 comprehensively controls the entire video display system 110. The control device 112 can realize its function by, for example, a CPU (Central Processing Unit), a computer, or the like executing a predetermined program.

The video signal processing device 113 generates a video signal to be supplied to the video display device 111. The power supply device 114 supplies power to each device constituting the video display system 110.

The storage device 115 stores a program executed by the control device 112, information necessary for processing of each device constituting the video display system 110, information generated by each device, and the like. The storage device 115 includes, for example, a RAM (Random Access Memory), a flash memory, an HDD (Hard Disk Drive), an SSD (solid state drive) CD-R (Compact Disc-Recordable), and a DVD-RAM (Digital Versatile Disk-Random Access). It consists of a storage medium such as Memory) that can be written and read, or a storage media driving device or the like.

The sensing device 116 detects the surrounding situation by using each sensor connected via the sensor input / output unit 117. The sensors include, for example, a tilt sensor that detects the user's posture, orientation, and movement, an acceleration sensor, a line-of-sight sensor that detects the user's physical condition, a temperature sensor, and GPS (Global Positioning System) reception that detects the user's position information. Devices, pressure sensitive sensors, capacitance sensors, bar code readers and the like can be mentioned.

The communication device 118 uses a communication input / output unit 119 for wireless communication using, for example, Bluetooth (registered trademark), Wi-Fi (registered trademark), UHF (Ultra-High Frequency) wave, VHF (Very High Frequency) wave, and the like. Alternatively, communication is performed by connecting to a predetermined communication network (mobile phone communication network, Internet, etc.) using wired communication.

The voice processing device 120 is connected to a microphone, earphones, or the like via the voice input / output unit 121 to input / output audio signals.

FIG. 2 is a configuration diagram of the video display device 111 in this embodiment. In FIG. 2, the image display device 111 includes an image projection module 131, an image light duplication unit 132, and a light guide plate 133.

The video projection module 131 is supplied with a video signal generated by the video signal processing device 113 via the control device 112, and based on the video signal, generates video light to be a video displayed by the video display device 111. It is projected onto the image light duplication unit 132. The image light duplication unit 132 duplicates the image light so that the image light projected by the image projection module 131 can be displayed as an image having uniform brightness for the user.

The light guide plate 133 transmits the image light from the image projection module 131 and the image light duplication unit 132 to the user's pupil 2. The user can visually recognize the image by forming the image light on the pupil 2.

FIG. 3 is a diagram showing a usage mode of the video display system 110 in this embodiment as an HMD 4. The HMD 4 is attached to the head of the user 1, and the user 1 can visually recognize the image from the image display device 111 as a virtual image 3 in a state where the outside world can be visually recognized. Although the case where the image is displayed in one eye is shown in FIG. 3, the HMD configuration in which the image is displayed in both eyes may be used at all.

FIG. 4 is an example of an image generation device that can be adopted in the image projection module 131 in this embodiment. FIG. 4A shows a fiber scanning projector 201 that can be used in the image projection module 131. FIG. 4B shows a mirror scanning projector 202 that can be used in the image projection module 131.

The fiber scanning projector 201 shown in FIG. 4A includes a light source unit 900, a fiber 901, a fiber scanning element 902, and a collimating lens 903.

The light source unit 900 emits, for example, a laser beam. The laser beam emitted by the light source unit 900 propagates inside the fiber 901 and is emitted from the end face 904 of the fiber 901. The light emitted from the fiber 901 passes through the collimating lens 903 to become light having high directivity.

The fiber scanning element 902 attached to the fiber 901 vibrates the end face 904 of the fiber 901 and scans the light emitted from the fiber 901. The fiber scanning projector 201 can project an image by synchronizing the intensity of the laser beam output by the light source unit 900 with the vibration of the end face 904 by the fiber scanning element 902 with the image signal.

The mirror scanning projector 202 shown in FIG. 4B includes a light source unit 900 and a scanning element 911.

The scanning element 911 has a scanning mirror (not shown). The laser light output by the light source unit 900 has directivity, and the laser light is incident on the scanning mirror of the scanning element 911 and reflected. At this time, the scanning element 911 can scan the reflected light reflected by vibrating the scanning mirror. The mirror scanning projector 202 can project an image by synchronizing the intensity of the laser beam output by the light source unit 900 with the vibration of the scanning element 911 with the image signal.

Next, the light guide plate used in the image display device will be described. The light guide plate includes a video light input surface on which an optical input unit 221 for incident video light is arranged, and a video light output surface on which video light is emitted on which an optical output unit 222 for emitting video light is arranged. (Details will be described later). The light guide plate duplicates the image light and projects it to the user. By duplicating the image light, the eyebox expands in the direction of duplication of the image light. The light guide plate can be an HMD having see-through properties by forming a light guide plate using a beam splitter array, a diffraction grating, a volume hologram, or the like.

FIG. 5 is an example of a light guide plate used in the image display device in this embodiment. The light guide plate 801 shown in FIG. 5A is a light guide plate using a beam splitter array and has N beam splitter surfaces 830 inside. Here, N is an integer of 1 or more. The N beam splitter planes 830 are substantially parallel to each other.

The incident surface 831 is an image light input surface on which the image light is incident on the light guide plate 801 and functions as an optical input unit 221. The first inner surface reflecting surface 832 and the second inner reflecting surface 833 guide the inside of the light guide plate 801 by total reflection of the light incident on the light guide plate 801 from the incident surface 831.

The light that is totally reflected by the first inner reflection surface 832 and the second inner reflection surface 833 and propagates inside the light guide plate 801 is incident on the N beam splitter surfaces 830. The beam splitter surface 830 reflects a part of the incident light and transmits a part of the incident light. The reflected light passes through the second inner reflection surface 833 and is transmitted to the user's pupil 2. The second inner reflection surface 833 is a video light output surface. The image light is reflected or transmitted by the N beam splitter surfaces 830, so that the image light is duplicated in the arrangement direction of the beam splitter surfaces (x direction in the figure), and the eyebox is expanded in the one-dimensional direction.

FIG. 5B is an example of a light guide plate using a surface-drilling diffraction grating. The light guide plate 811 shown in FIG. 5B has a plurality of diffraction regions 812 and 813. The diffraction region 812 has a diffraction structure in a direction substantially parallel to the z-axis. The diffraction region 813 has a diffraction structure in two directions in the xz plane, a first direction of approximately +60 degrees counterclockwise from the x-axis and a second direction of approximately -60 degrees. The pitch of the diffraction structure in the diffraction region 812 and the pitch of the diffraction structure in the two directions of the diffraction region 813 are all substantially equal to each other.

The video light incident on the diffraction region 812, which is the optical input unit 221, is diffracted and taken into the inside of the light guide plate 811 to guide the light while totally reflecting the inside of the light guide plate 811, and the diffraction corresponding to the light output unit 222. Reach region 813. The diffraction region 813 has a diffraction structure in two directions, and in the process of totally reflecting and guiding the light inside the light guide plate 811, the diffraction region 813 is diffracted once in each of the two directions of the diffraction structure. The image light is duplicated and emitted from the light guide plate 811. Since the image light is duplicated in the first direction and the second direction, the eyebox is enlarged in the two-dimensional direction.

FIG. 5C shows another example of a light guide plate using a surface-drilling diffraction grating. The light guide plate 821 shown in FIG. 5 (c) has a plurality of diffraction regions 822, 823, and 824. The diffraction region 822 has a diffraction structure in a direction substantially parallel to the x-axis. The diffraction region 823 has a diffraction structure in a direction substantially parallel to a straight line of z = −x in the xz plane. The diffraction region 824 has a diffraction structure in a direction substantially parallel to the z-axis. The pitch of the diffraction structure in the diffraction region 822 and the pitch of the diffraction structure in the diffraction region 824 are substantially equal to each other, and the pitch of the diffraction structure in the diffraction region 823 is the value obtained by dividing the pitch of the diffraction structure in the diffraction region 822 by the square root of 2. Approximately equal.

The video light incident on the diffraction region 822, which is the optical input unit 221, is diffracted and taken into the inside of the light guide plate 821, and the inside of the light guide plate 821 is totally reflected and guided. In the process of total internal reflection light guiding, a part of the light is diffracted every time it reaches the diffraction region 823, the traveling direction is changed, and the inside of the light guide plate 821 is totally reflected and guided. Further, each time the light reaches the diffraction region 824 corresponding to the light output unit 222, a part of the light is diffracted, the light is duplicated, and the light is emitted from the light guide plate 821. Therefore, according to the light guide plate 801, the image light is duplicated in the two directions of the x-axis direction and the z-axis direction of the figure, and the eye box is enlarged in the two-dimensional direction.

As a means for duplicating the image light propagating in the light guide plate and transmitting it to the user's pupil 2, diffraction by a volumetric hologram may be used instead of a mirror array or a diffraction grating.

As described above, a small image generator and a light guide plate that scan directional light (laser light) such as the fiber scanning projector 201 and the mirror scanning projector 202 shown in FIG. 3 to generate an image. By combining these, a compact video display device can be realized. Here, the spot diameter of the video light generated by the above-mentioned video generator is about 0.1 to 3.0 mm, which is smaller than the distance between the plurality of video lights output from the light guide plate 133, and is from the light guide plate 133. Multiple output video lights do not overlap, or the overlap is insufficient. As a result, there is an image portion where the image light does not enter the user's pupil or the amount of light incident on the user's pupil is extremely small. Therefore, uneven brightness occurs in the displayed image, which causes a problem that the user cannot display an image having uniform brightness.

Therefore, in order to provide a video display device that displays a video having uniform brightness for the user, in the video display device 111 in the present embodiment, video light is transmitted from a predetermined interval between the video projection module 131 and the light guide plate 133. There is also a video light duplication unit 132 that duplicates at small intervals. Hereinafter, the video light duplication unit 132 will be described in detail.

FIG. 6 schematically illustrates an optical path until the image light 5 emitted from the image projection module in this embodiment is transmitted to the user's pupil 2. As an example, the first video light duplication unit 132 shows a case where the video light is duplicated in the x direction in the figure, and the duplication direction of the light guide plate is not particularly shown. Further, as shown in FIG. 6, the eye relief, which is the distance from the user's pupil 2 to the light guide plate 133, is ER, the eye box in the x direction is EB, and the full angle of the angle of view in the x direction of the displayed image is FOV.

In FIG. 6, the image light 5 emitted from the image projection module 131 is duplicated by the first image light duplication unit 132. The image light 6 duplicated by the first image light duplication unit 132 is then duplicated by the light guide plate 133 and emitted. The plurality of video lights 6 emitted from the video light duplication unit 132 are incident on the light guide plate from the light input unit 221 of the light guide plate. The image light incident on the light guide plate 133 is emitted from the light output unit 222 and transmitted to the user's pupil 2.

Here, since the spot diameter of the image light emitted from the image projection module 131 is small, even if the image is duplicated only by the light guide plate 133 and the image is projected to the user, the plurality of image lights do not overlap or overlap. Is insufficient. As a result, there is an image portion where the image light does not enter the user's pupil or the amount of light incident on the user's pupil is extremely small. Therefore, the above problem can be solved, that is, the brightness of the displayed image can be made uniform by duplicating the image light in the image duplication unit after the image projection module and making it incident on the light guide plate.

FIG. 7 is a diagram for explaining the duplication interval of the video light duplication unit in this embodiment. FIG. 7 shows the intensity distribution of the plurality of video lights 6 at the light input unit 221 of the light guide plate, and shows the spot 20 of the video light in a circular shape. The spot diameter of the image light in the optical input unit 221 was set to D. Further, the number of a plurality of video lights emitted by the video light duplication unit 132 is N (N is an integer of 2 or more), and the distance between the centers of the kth and k + 1th video lights adjacent to each other is the duplication interval Lk. (K is an integer of 1 or more and N-1 or less). Although the spots are shown in a circle for simplicity in the figure, they are not necessarily circular, and in that case, the replication interval is determined centering on the center of gravity of the spot intensity distribution.

Here, the brightness of the displayed image can be effectively made uniform by appropriately selecting the duplication interval Lk. That is, unless the image light duplicated by the image light duplication unit finally enters the user's pupil, the image brightness uniform effect due to the duplication cannot be obtained, so the duplication interval Lk needs to be smaller than the human pupil size. There is. Since the pupil size of a person changes to about 2 to 8 mm depending on the outside brightness, the duplication interval Lk needs to be 2 mm or less, which is the minimum pupil size.

In addition, as shown in FIG. 7A, if the spots 20 do not overlap and a gap is formed, the gap may be projected to the user's eyes, and the user can visually recognize the image with uniform brightness. There are cases where it cannot be done. Therefore, in order to make the displayed image uniform in brightness, it is necessary that the spot 20 is at least in contact with the spot 20 when viewed on the optical input unit. That is, in order for the image duplication device to obtain the effect of equalizing the brightness of the displayed image, the diameter D of the spot 20 and the duplication interval Lk are at least one k, and the following relational expression (1)

を満たしていることが必要である。

It is necessary to meet.

In addition, the intensity of the spot is the strongest in the center, and the intensity becomes weaker toward the periphery. Therefore, the distribution of the plurality of video lights duplicated and emitted by the video light duplication unit may not be sufficiently uniform just by being in contact with each other, and may be insufficient to make the displayed video uniform in brightness. In order to make the displayed image uniform in brightness, it is desirable that the spots have overlaps as shown in FIG. 7 (b).

If the light intensity ratio is 10% or more overlapped, the user can visually recognize the image with uniform brightness. Therefore, it is desirable that adjacent spots overlap with 10% or more of the peripheral illumination of the spot distribution. Alternatively, it is desirable for the user to duplicate the image by overlapping one quarter or more of the spot diameter D in order to visually recognize the image with uniform brightness, and the diameter D and the duplication interval Lk are at least one k and the following relational expression (2).

を満たしていることが望ましい。

It is desirable to meet.

Next, the condition of the width C of the plurality of video lights duplicated by the video light duplication unit shown in FIG. 7B will be described. C can be written by the following equation (3) using the duplication interval Lk and the spot diameter D.

Considering that the image light emitted by the width C is finally projected to the user's eyes, it is desirable that the width C is larger than the pupil size of the user. As a result, it is possible to display an image with uniform brightness even when the user's eyes move due to misalignment or eye movements. Therefore, when the minimum diameter size of the pupil is Dmin, it is desirable that the width C is larger than Dmin, and it is desirable that the following equation (4) is satisfied.

In order to make the displayed image uniform in brightness, C ≦ D × N can be written when adjacent spots are at least in contact with each other. As a result, the number of duplicates of video light N and the spot diameter D are related to the following relational expression (5).

を満たすことが望ましい。

It is desirable to meet.

Next, the width W of the image light emitted from the light guide plate 133 shown in FIG. 6 will be described. In order for the user to visually recognize the entire image, the width W needs to satisfy the following equation (6).

As described above, ER is an eye relief, EB is an eye box in the x direction of EB, and FOV is the full-width angle of view of the displayed image in the x direction.

Assuming that the number of duplications in which the light guide plate 133 duplicates the image light is M, the width W of the image light emitted from the light guide plate 133 does not always match the duplication direction of the image light duplication portion and the light guide plate. The inequality (7) holds.

Therefore, from the equations (6) and (7), the spot diameter D, the number of duplicates N of the image duplication unit, and the number of duplications M of the light guide plate are the following relational expressions (8) in order to make the entire image visible to the user.

を満たしている必要がある。

Must be met.

FIG. 8 is a diagram showing a configuration example of the video display device 111 in this embodiment. In FIG. 8, (a) is a view seen from the upper part of the light guide plate 133, and (b) is a view seen from the front of the light guide plate 133.

In FIG. 8, the image light emitted from the image projection module 131 is incident on the image light duplication unit 132, then duplicated and emitted by the image light duplication unit 132, and is incident on the light guide plate from the light input unit 221 of the light guide plate. The image light incident on the light guide plate 133 is emitted from the light output unit 222 and transmitted to the user's pupil 2 (not shown). The user can visually recognize the image by forming the image light on the pupil 2.

The surface of the light guide plate on which the optical input unit 221 is installed is the video light input surface 22. Further, the angle (α) formed by the video light input surface 22 of the light guide plate and the incident surface 11 of the video light duplication unit is defined as the installation angle α of the video light duplication unit.

FIG. 9 is a diagram for explaining the image light duplication unit 132 in this embodiment. In FIG. 9, the image light duplication unit 132 has a single flat plate shape, and has an incident surface 11 on which the image light emitted from the image projection module 131 is incident and a first surface 10 substantially parallel to the incident surface 11. A reflection coat 8 is applied to the first surface 10, which is a partially reflective surface through which light is reflected and transmitted. Further, a reflective coat 7 is applied to a part of the incident surface 11, which is a reflective surface on which light is reflected. As shown in FIG. 9, the thickness t of the image light duplication portion 132 indicates the thickness formed by the incident surface 11 and the first surface 10.

In FIG. 9, the image light 5 shows a typical light ray emitted from the image projection module 131. The video light emitted from the video projection module 131 is incident from the incident surface 11 of the video light duplication unit 132. The incident light is first transmitted and reflected by the first surface 10 which is a partially reflecting surface. The video light transmitted through the first surface 10 is emitted from the video light duplication unit 132. The light reflected by the first surface 10 travels toward the incident surface 11 and is reflected by the incident surface 11 which is coated with the reflection coat 7 and serves as the reflecting surface. The image light reflected by the incident surface 11 is transmitted or reflected by the first surface 10 which is a partially reflecting surface. As described above, the video light is duplicated at equal intervals by repeating partial reflection and reflection.

The direction in which the image light 5 is duplicated is the direction in which the image light duplication unit 132 has an inclination with respect to the image light input surface 22 which is the light input unit 221 of the light guide plate (direction in the x-axis in FIG.).

In this embodiment, the entrance surface 11 and the emission surface of the image light duplication unit 132 are different, and the emission surface is the first surface 10 substantially parallel to the entrance surface 11.

The video light duplication unit 132 duplicates the video light with a very simple structure in the shape of a flat plate and causes it to be incident on the light guide plate. It prevents it from becoming sufficient. By mounting the video light duplication unit 132, which has a very simple flat plate shape, on the video display device 111, it is possible to provide a video display device capable of displaying a video having uniform brightness for the user.

It should be noted that the above-mentioned problem that the user cannot display an image having uniform brightness becomes more prominent in a direction different from the duplication direction of the light guide plate. Therefore, it is effective to arrange the video light duplication unit so that the duplication direction of the light guide plate and the duplication direction of the video light duplication unit are different.

Further, by applying a reflection coating only to a part of the incident surface 11, only transmission occurs in the region of the incident surface 11 where the image light is incident, preventing reflection at the time of incidence and efficiently transmitting the image light to the image light. It can be incident on the duplication unit 132.

Further, it is preferable that the end surface 13 of the image light duplication portion 132 is treated with either or both of sand rub and black coating. This makes it possible to prevent the generation of stray light due to the light incident on the end face 13.

Next, the duplication interval L of the plurality of video lights 6 duplicated by the video light duplication unit 132 will be described. Using the thickness t and angle α of the video light duplication portion and the refractive index n of the material of the video light duplication portion, the duplication interval L is the following equation (9).

のように書ける。

Can be written like this.

Since the image brightness uniform effect by duplication cannot be obtained unless the image light duplicated by the image light duplication unit finally enters the user's pupil, the duplication interval L needs to be smaller than the pupil size of a person. .. The size of a person's pupil varies from about 2 to 8 mm depending on the outside brightness. Therefore, the duplication interval Lk needs to be a minimum pupil size of 2 mm or less.

In addition, from the viewpoint of making the brightness of the displayed image uniform, it is preferable that the spots of the image light emitted from the image projection module are in contact with each other or duplicated when viewed by the optical input unit 221. Therefore, it is desirable that the duplication interval L is the same as or smaller than the spot diameter D in the optical input unit 221. Therefore, the following relational expression (10)

を満たすことが望ましい。

It is desirable to meet.

From the above viewpoints, the thickness t and the angle α of the video light duplication portion and the refractive index n of the video light duplication portion may be determined so as to have an appropriate duplication interval.

Next, the installation angle α will be described. FIG. 10 shows the setting angle α dependence of the duplication interval at a certain thickness t. The refractive index n was calculated at 1.52 assuming general glass. The duplication interval L is a convex graph centered on about 50 degrees with respect to the installation angle α, and when α is 0 degrees and 90 degrees, the duplication interval L becomes 0. Therefore, in order for the video light duplication unit to duplicate the video light, the video light duplication unit must be installed at a predetermined angle, and the installation angle cannot be 90 degrees.

Further, the smaller the installation angle α, the smaller the width A shown in FIG. 8, the smaller the image display, the smaller the distance from the video light duplication section to the light guide plate input section, and the smaller the distance from the video light duplication section to the light guide plate. The efficiency of incident on the optical input unit 221 is improved. Therefore, it is preferable that α is smaller from the viewpoint of miniaturization of the entire image display and the efficiency of incident on the light input unit 221 of the light guide plate.

As shown in FIG. 10, the duplication interval L has a substantially symmetrical dependence on the installation angle α around about 50 degrees, and the same duplication interval L is obtained regardless of whether the installation angle α is reduced or increased from 50 degrees. Can be. However, increasing the installation angle is not desirable from the viewpoint of miniaturization and incident efficiency described above. Therefore, from the viewpoint of miniaturization of the image display device and the efficiency of incident from the image light duplication unit to the light guide plate, the installation angle α of the image light duplication unit may be 50 degrees or less.

Further, if the installation angle is too small, the deviation sensitivity such as the change in the duplication interval due to the installation deviation of the parts becomes large. Therefore, it is desirable that the installation angle α is 5 degrees or more.

When the installation angle α of the video light duplication unit is considered to be 50 degrees or less and 5 degrees or more for the above reason from the viewpoint of miniaturization of the video display device and the incident efficiency from the video light duplication unit to the light guide plate, duplication is performed. In order to obtain the effect of uniform brightness of the image, the condition that the duplication interval L is the minimum pupil size of 2 mm or less is that the thickness t is 18 mm or less in terms of the refractive index of general glass from the equation (9). Therefore, it is desirable that the thickness t is 18 mm or less in order to obtain the effect of uniform brightness of the image.

Next, the relationship between the reflectance of the partially reflecting surface and the amount of duplicated video light will be described. As shown in FIG. 9, the reflectance of the partially reflecting surface is R, and the amount of light of the image light incident on the image light duplication portion is _I0 . The amount of light of the plurality of duplicated video lights is described as In in the order of approaching from the end face 12 to the end face 13 side ( _n is a natural number of 1 or more and N or less). Then, the nth amount of light is given by the following equation (11).

のように書ける。

Can be written like this.

In order to display an image with uniform brightness for the user, it is desirable that the duplicated image light is emitted with a uniform amount of light. The adjacent light amount ratio K of the duplicated video light is R (= I _{k + 1} ÷ I _k ). Generally, if the light amount ratio of adjacent duplicated lights is 70% or more, the user can recognize the duplicated video light as a uniform image without feeling the difference in brightness. Therefore, it is desirable that the reflectance R of the partially reflecting surface is 70% or more.

In addition, the reflectance of the partially reflective surface was discussed with a constant reflectance, but the reflectance is made position-dependent with respect to the duplication direction of the image light duplication unit, and the reflectance decreases as the distance from the image projection module 131 increases. The amount of light of the plurality of video lights duplicated as the reflecting surface may be made uniform. As a result, the duplicated video light can be emitted with a uniform amount of light, and the duplicated video light can be more efficiently emitted to the light guide plate.

Further, although the video light duplication unit has been described with a single flat plate structure, the video light duplication unit 51 may be composed of two flat plates as shown in FIG. Similarly, the incident surface 11 is partially coated with a reflective coat to serve as a reflective surface. Further, the incident surface 11 and the second surface 14, which are the first surfaces substantially parallel to the incident surface, are coated with a reflection coat and are partially reflective surfaces. By forming the image light duplication unit with two flat plates, the number of partially reflecting surfaces can be increased, and the number of image light duplications can be increased. Therefore, the image can be made more uniform. Further, by making the thicknesses t1 and t2 of the two flat plates different, the video light can be duplicated at a plurality of intervals, which is more effective from the viewpoint of uniformizing the video. Further, although the two flat plates are shown in the figure, the structure is not necessarily limited to this, and there is no problem even if the number of plates is larger than the two.

Further, in order to make the brightness of the displayed image more uniform, a duplication prism 19 for duplicating the image light may be installed between the image projection module 131 and the image light duplication unit 132. FIG. 12 shows a configuration example in which the duplication prism 19 is installed. In FIG. 12, (a) is a view seen from the upper part (z direction) of the image light duplication unit 132, and (b) is a view seen from the x direction of the image light duplication unit 132.

As shown in FIG. 12B, the duplication prism 19 is provided with a plurality of reflective surfaces that reflect or partially reflect inside. The image light emitted from the image projection module 131 is incident on the duplication prism 19, and is reflected or partially reflected by the reflecting surface inside the duplication prism 19, so that the image light is duplicated and emitted to the image light duplication unit 132. With such a configuration, the number of duplicates of the image light incident on the light guide plate can be increased, and the brightness of the displayed image can be made more uniform.

It is preferable that the video light duplication unit 132 and the duplication prism 19 are arranged so that the duplication directions are different so that the display image brightness equalization effect due to duplication does not overlap. As a result, it is possible to efficiently obtain the effect of equalizing the brightness of the displayed image by duplication. FIG. 12 shows a case where the video light duplication unit 132 duplicates the video light in the x direction and the duplication prism 19 duplicates the video light in the z direction as an example.

Further, it is desirable that the duplication prism 19, the image light duplication portion 51, and the light guide plate 133 are arranged so that the duplication directions are different so that the display image brightness equalization effect due to duplication does not overlap. As a result, it is possible to efficiently obtain the effect of equalizing the brightness of the displayed image by duplication.

Further, as described above, it is desirable that the reproduction interval of the image light is 2 mm or less, which is the minimum pupil size of a person. Therefore, it is desirable that the distance Dr between the reflecting surfaces of the duplication prism 19 shown in FIG. 12 is 2 mm or less.

Further, in the duplicate prism 19 of the configuration example of FIG. 12, the example of two reflective surfaces inside the duplicate prism 19 is shown, but there is no problem even if the number of reflective surfaces is increased from two.

As described above, according to the present embodiment, it is possible to provide a light guide plate type video display device and a video display system capable of displaying a video having uniform brightness for the user.

FIG. 13 is a diagram showing a configuration example of the video display device 111 in this embodiment. In FIG. 13, (a) is a view seen from the upper part of the light guide plate 133, and (b) is a view seen from the front of the light guide plate 133.

In FIG. 13, the same configurations as those in FIG. 8 are designated by the same reference numerals, and the description thereof will be omitted. In FIG. 13, the difference from FIG. 8 is that the entrance surface and the emission surface of the video light duplication unit 52 are the same surface. With such a configuration, the image projection module 131 can be arranged along the light guide plate 133 by appropriately selecting the installation angle α, and there is an advantage that the image display device 111 becomes compact.

The image light duplication unit 52 in this embodiment will be described with reference to FIG. The image light duplication unit 52 has an incident surface 15 on which the image light emitted from the image projection module 131 is incident, and a first surface 16 substantially parallel to the incident surface 15. A reflective coat 7 is applied to the first surface 16, which is a reflective surface on which light is reflected. A reflection coat 8 is applied to a part of the incident surface 15, which is a partially reflecting surface through which light is reflected and transmitted.

In FIG. 14, the image light 5 emitted from the image projection module 131 is incident from the incident surface 15 of the image light duplication unit 52. The incident light is first reflected by the first surface 16 which is a partially reflecting surface. The light reflected by the first surface 16 travels toward the incident surface 15, and is reflected and transmitted by the incident surface 15 which is coated with the reflection coat 8 and is a partially reflecting surface. The image light transmitted through the incident surface 15 is emitted from the image light duplication unit 52. The light reflected by the incident surface 15 travels toward the first surface 16 and is reflected again by the first surface 16.

As described above, the video light incident on the video light duplication unit 52 repeats partial reflection and reflection, so that the video light 5 is duplicated in the direction in which the video duplication element is tilted with respect to the light guide plate (the x-axis direction in the figure). , Is emitted from the image light duplication unit 52. In the video light duplication unit of this embodiment, the entrance surface and the emission surface are the same surface. Then, by applying a reflection coating only to a part of the incident surface 15, only transmission occurs in the region of the incident surface 15 where the image light is incident, the reflection is prevented at the time of incidence, and the image light is efficiently duplicated. It can be incident on the portion 52.

Further, as shown in FIG. 15, a reflection prism 17 may be installed between the image projection module 131 and the image light duplication unit 132, and the image projection module 131 may be arranged along the light guide plate 133. By changing the traveling direction of the image projection module 131 by the reflection of the reflection surface 18 of the reflection prism 17, the image projection module 131 can be arranged along the light guide plate 133, and the entire image display device 111 is made smaller and the design is improved. can.

Although the examples have been described above, the present invention is not limited to the above-mentioned examples, and includes various modifications. For example, each of the above embodiments has been described in detail in order to explain the present invention in an easy-to-understand manner, and the present invention is not necessarily limited to the one including all the components described above. Further, it is possible to replace a part of the configuration of a certain embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of a certain embodiment. Further, it is possible to add / delete / replace a part of the configuration of each embodiment with another configuration.

2: Eyes, 3: Virtual image, 4: Head mount display (HMD), 5, 6: Video light, 7, 8: Reflective coat, 9: Rays, 10, 16: First surface, 11, 15: Incident surface , 12, 13: End face, 14: Second surface, 17: Reflective prism, 18: Reflective surface, 19: Replica prism, 20: Spot, 22: Video light input surface, 51, 52, 132: Video light duplication unit 110: Video display system, 111: Video display device, 112: Control device, 113: Video signal processing device, 114: Power supply device, 115: Storage device, 116: Sensing device, 117: Sensor input / output unit, 118: Communication device, 119: Communication input / output unit, 120: Audio processing device, 131: Image projection module, 133: Light guide plate, 201: Fiber scanning projector, 202: Mirror scanning projector, 221: Optical input unit, 222: Optical Output section

Claims (15)

It is a video display device that displays video.
An image projection module that scans light to generate image light,
An image light duplication unit that duplicates and emits the image light,
It has a light guide plate that duplicates and emits the image light from the image light duplication unit.
The light guide plate includes an optical input unit for incident video light.
The number of video lights emitted by the video light duplication unit is N, the spot diameter of the plurality of video lights emitted from the video light duplication unit at the optical input unit is D, and the minimum diameter size of the human pupil is set. A video display device characterized in that the relational expression of Dmin ≦ D × N is satisfied when Dmin is set. The video display device according to claim 1.
When the distance between the centers of the adjacent k-th and k + 1-th video lights emitted by the video light duplication unit is Lk (k is an integer of 1 or more and N-1 or less), Lk ≦ at least one k. An image display device characterized by satisfying D. The video display device according to claim 2.
When the number of duplicates of the image light by the light guide plate is M, the eye box is EB, the eye relief is ER, and the angle of view of the image projected by the image projection module is FOV, the following relational expression is satisfied. A featured video display device.
EB + 2 x ER x tan (FOV / 2) ≤ D x N x M It is a video display device that displays video.
An image projection module that scans light to generate image light,
An image light duplication unit that duplicates and emits the image light,
A light guide plate that duplicates and emits the image light from the image light duplication unit is provided.
The image light duplication unit has an incident surface and a partially reflecting surface on which the image light is incident, and is characterized in that a part of the incident surface is coated with a reflection. The video display device according to claim 4.
An image display device characterized in that the direction in which the light guide plate replicates image light and the direction in which the image light duplicating unit replicates image light are different. The video display device according to claim 5.
The light guide plate has a video light input surface provided with an optical input unit for incident video light.
The video light duplication unit is a video display device characterized in that the incident surface and the video light input surface are arranged at an angle α of 50 degrees or less. The video display device according to claim 6.
An image display device having a thickness t of the image optical duplication portion of 18 mm or less. The video display device according to claim 7.
When the spot diameter of the video light in the optical input unit is D, the thickness of the video light duplication unit is t, and the refractive index of the video light duplication unit is n, the following equation is satisfied. Display device.

The video display device according to claim 4.
An image display device characterized in that the reflectance of the partially reflecting surface is 70% or more. The video display device according to claim 4.
An image display device characterized in that the reflectance of the partially reflecting surface has a position dependence with respect to the duplication direction of the image light duplication unit and decreases as the distance from the image projection module increases. The video display device according to claim 4.
An image display device comprising a prism having a plurality of reflecting surfaces for replicating the image light between the image projection module and the image light duplicating unit. The video display device according to claim 4.
The image light duplication unit has an emission surface from which the image light is emitted, and the emission surface is the partial reflection surface substantially parallel to the incident surface. The video display device according to claim 4.
The image light duplication unit has an emission surface from which the image light is emitted, and the emission surface is the same surface as the incident surface and is the partial reflection surface. The video display device according to claim 4.
An image display device comprising a prism having a reflecting surface for reflecting the image light between the image projection module and the image light duplication unit. A video signal processing device that generates video signals and
It is equipped with a video display device that displays video based on the video signal.
The image display device includes an image projection module that scans light to generate image light.
An image light duplication unit that duplicates and emits the image light,
It has a light guide plate that duplicates and emits the image light from the image light duplication unit.
The light guide plate includes an optical input unit for incident video light.
The number of video lights emitted by the video light duplication unit is N, the spot diameter of the plurality of video lights emitted from the video light duplication unit at the optical input unit is D, and the minimum diameter size of the human pupil is set. A video display system characterized in that the relational expression of Dmin ≦ D × N is satisfied when Dmin is set.

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