JP2022120574A - head mounted display device - Google Patents

Abstract

To provide HMD that enables reduction in the cell size of MLA and increase in the use efficiency of light utilization without adversely affecting pictures.SOLUTION: A head mounted display device includes a video display device for generating a video, an illumination system for supplying illumination light to the video display device, and an optical element for guiding the illumination light to the video display device and causing the light from the video display device to enter a projection system. The illumination system has a microlens array, and the cell size of the microlens array is set so that the range of the illumination light to be supplied to the video display device is a predetermined range larger than a light receiving surface of the video display device. The microlens array has a holding structure the attitude of which is adjustable.SELECTED DRAWING: Figure 10

Description

The present invention relates to a head mount display (HMD: Head Mount Display, hereinafter referred to as HMD) that projects and displays a virtual image.

An HMD is a device that displays an image by generating a virtual image through a light guide element in the form of eyeglasses or goggles. 2. Description of the Related Art In HMDs, liquid crystal on silicon (LCOS), for example, is known as a video display device that modulates light incident from an illumination system based on a video signal to generate an image. LCOS has a liquid crystal between the pixel electrode for image generation and the common electrode, and by controlling the electric field between the electrodes for each pixel based on the image signal, the polarization corresponding to the change in the phase difference of the light that has passed through the liquid crystal It displays images by generating brightness and darkness depending on the angle. Also, a configuration using a microlens array (hereinafter referred to as MLA) is known to uniformize the intensity distribution of light supplied to the image display device.

There is Patent Document 1 as a background art in this technical field. In Patent Document 1, in an HMD consisting of an image display section and a light guide section, the image display section includes a light source section, a condenser lens, a color synthesizing section, an MLA, an imaging lens, and an imaging lens with a prism. , a reflector, a display, and a virtual image projector, the light beams from the light source are converted into substantially parallel light by a condenser lens, the light beams of each color are synthesized by the color synthesizing unit, and a uniform intensity distribution is produced by the MLA. A configuration is disclosed for generating and providing illumination light to a display via an imaging lens, an imaging lens with a prism, and a reflector.

WO2019/107044

There is a method of increasing the light utilization efficiency by reducing the size of the light flux condensed on the image display device by reducing the cell size of the MLA and increasing the amount of light supplied to the image display device. However, since this method reduces the size of the luminous flux, there is a problem that image defects may occur during the position adjustment of the image display device in the manufacturing process.

Patent Document 1 does not consider reducing the cell size of the MLA to increase the light utilization efficiency.

SUMMARY OF THE INVENTION An object of the present invention is to provide an HMD capable of reducing the cell size of an MLA and increasing the efficiency of light utilization without adversely affecting images.

To give an example, the present invention includes an image display device that generates an image, an illumination system that supplies illumination light to the image display device, and a projection system that guides the illumination light to the image display device and projects the light from the image display device. The illumination system has a microlens array, and the cell size of the microlens array is such that the range of the illumination light supplied to the image display device is the same as that of the image display device. The microlens array has a holding structure capable of adjusting its posture.

ADVANTAGE OF THE INVENTION According to this invention, the HMD which can reduce the cell size of MLA, and can improve the utilization efficiency of light can be provided, without a bad image.

1 is a schematic configuration diagram of a reflective image display section using LCOS in a conventional HMD; FIG. 1 is a schematic configuration diagram of a transmissive image display unit using an LCD in a conventional HMD; FIG. 1 is a schematic configuration diagram of a video display unit using DLP in a conventional HMD; FIG. It is a figure explaining the relationship between MLA cell size and the luminous flux on LCOS. FIG. 4 is a schematic diagram of the relationship between the MLA cell size and the flux magnitude on the LCOS; FIG. 4 is a diagram showing the relationship between the range (luminous flux) of light supplied to the LCOS and the rate of change in the amount of light; It is a figure explaining the dispersion|variation of the polarization angle of LCOS. It is a figure explaining the attachment gap of PBS. FIG. 10 is a diagram for explaining image loss caused by reducing the MLA cell size when the LCOS is rotationally adjusted; FIG. 10 is a diagram for explaining image dropout and rotation adjustment of the MLA caused by reducing the MLA cell size in the embodiment; It is a shape example of MLA in an Example. It is another shape example of the MLA in the embodiment. It is a schematic diagram explaining the shape of the mounting case which mounts MLA in an Example, and a fixing method. It is a schematic diagram explaining the adjustment method of MLA in an Example. 1 is a schematic configuration diagram of an image display unit of an HMD in an example; FIG. FIG. 2 is a schematic configuration diagram of a light-receiving surface peripheral portion of the image display device in the example. 4 is a processing flowchart of MLA rotation adjustment in the embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

First, the configuration of a conventional HMD, which is the premise of this embodiment, will be described.

FIG. 1 is a schematic configuration diagram of an image display unit in a conventional HMD. It should be noted that if one structure shown in FIG. 1 is provided, it becomes a monocular HMD, and if two structures are provided, it becomes a binocular HMD. is.

In FIG. 1, an image display unit 100 includes an illumination system 10, a polarizing optical element (PBS (Polarizing Beam Splitter) 20), an image display device 30, a projection system 40, and a light guide unit 50. ing. Note that FIG. 1 shows a case where the image display device 30 is an LCOS.

The illumination system 10 has a light source 11 and a light source 13, condenser lenses 12 and 14, a dichroic mirror 15, an MLA 16, a total reflection mirror 17, and an imaging lens . The illumination system 10 may omit some components or may include other components as long as the illumination system 10 can illuminate the image display device 30 via the PBS 20 .

In the illumination system 10, the light source 11 in the light source unit emits green light (G light), and the light source 13 includes a red light source and a blue light source mounted in the same package, and emits red light and blue light (R light). and B light). Note that FIG. 1 shows the light source 13 in which two color light sources are mounted in the same package as an example, but each of the three color light sources may be mounted in an independent package. Colored light sources may be integrated and implemented in one package.

Light emitted from the light source 11 enters the condensing lens 12 . The condensing lens 12 is arranged so that the light source 11 is positioned substantially at its synthetic focal position. A light beam emitted from the light source 11 enters the condenser lens 12 and becomes collimated light. Collimated light from light source 11 is emitted toward dichroic mirror 15 . Similarly, the light emitted from the light source 13 enters the condensing lens 14 to become collimated light and is emitted toward the dichroic mirror 15 . The dichroic mirror 15 aligns the optical axes of the R light, the B light, and the G light, synthesizes them, and synthesizes and emits the collimated light of each color.

The MLA 16 is an optical lens in which lenses each having a size on the order of micrometers are continuously arranged, and receives a substantially collimated light flux emitted from the dichroic mirror 15 . The approximately collimated light is generated by the condensing lenses 12 and 14, and is a collimated light beam having a spread of light corresponding to the light emitting area of the light source section. Therefore, when this light is collected by a lens provided on the incident side of the MLA 16, an image of the light source section is formed on the lens on the outgoing side of the MLA 16. FIG. A lens provided on the exit side of the MLA emits a light beam having a light distribution corresponding to the aperture shape of the lens provided on the entrance side of the MLA.

The light flux emitted from the MLA 16 is totally reflected by the total reflection mirror 17 and is incident on the imaging lens 18 after being bent at a substantially right angle. The imaging lens 18 forms an image toward the PBS 20 while condensing the collimated light. The formed image is obtained by superimposing the images of the apertures of the respective lenses provided on the incident side of the MLA 16 . Although the intensity distribution of the light that illuminates the aperture of the MLA 16 is not uniform, it is superimposed by the subsequent imaging lens 18 or the like, so that illumination light with a uniform intensity distribution can be provided.

The PBS 20 is an optical member made of a transparent material and having an incident surface, a reflecting surface, and an emitting surface. The reflective surface is inclined with respect to the optical axis of the imaging lens 18 and has polarization-selective reflective performance. That is, S-polarized light is reflected, but P-polarized light is transmitted. Therefore, when the luminous flux from the imaging lens 18 is P-polarized, the luminous flux from the imaging lens 18 passes through the reflecting surface and illuminates the image display device 30 .

The image display device 30 is an LCOS and is composed of a liquid crystal layer 32 and a display panel 33 . The display panel 33 reflects illumination light incident from the illumination system 10 . The liquid crystal layer 32 modulates and manipulates the polarized light of the illumination light incident from the illumination system 10 based on the video signal, thereby controlling the emitted light. Accordingly, the image display device 30 modulates the light incident from the illumination system 10 based on the image signal to generate image light. Image light generated by the image display device 30 enters the projection system 40 via the PBS 20 .

Projection system 40 projects an image of image display device 30 . The projection system 40 provides the image of the video display device 30 as a virtual image in order to form the image of the video display device 30 on the retina so that it exists at a desired distance from the user. Therefore, the image light from the projection system 40 is emitted to the light guide section 50 .

The light guide unit 50 takes in the image light generated by the image display device 30 from the projection system 40, internally reflects it, and guides it to the front of the user.

FIG. 2 is a schematic configuration diagram of an image display unit in a conventional HMD when the image display device is a transmissive LCD (Liquid Crystal Display). In FIG. 2, the same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. In FIG. 2, the difference from FIG. 1 is that the video display device 60 is an LCD, the total reflection mirror 17 is eliminated, the video display device 60 (LCD) to the light guide section 50 is straight, and the video display section 100 This is an example of an optical system that is made compact so as to fit the frame of spectacles.

FIG. 3 is a schematic configuration diagram of an image display unit in a conventional HMD when the image display device is DLP (Digital Light Processing) (registered trademark). In FIG. 3, the same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. 3 differs from FIG. 1 in that the video display device 31 is a DLP, has a triangular prism 21 instead of the PBS 20, and the illumination light is obliquely incident on the video display device 31. FIG. A DLP is an image display system using a digital mirror device (DMD), in which a plurality of fine mirrors are arranged for the number of display pixels, and by changing the angle of the mirrors, the brightness of the image display pixels is controlled.

FIG. 4 is a diagram illustrating the relationship between the MLA cell size and the luminous flux on the LCOS. In FIG. 4, the same components as those in FIG. 1 are denoted by the same reference numerals, and descriptions thereof are omitted. The relationship between the cell size and the range (luminous flux) of light supplied to the LCOS will be described with reference to FIG.

In FIG. 4, Wl, which is the range 35 of light supplied to the LCOS 30, is given by the following equation.
Wl=Wa×(f/fm),
Note that fm=R/(N-1)
Here, Wa: MLA cell size, f: focal length of imaging lens 18, fm: focal length of MLA 16, R: curvature of MLA 16, N: refractive index of MLA 16 From the above formula, range of light supplied to LCOS It can be seen that Wl is proportional to the MLA cell size Wa.

FIG. 5 is a schematic diagram of the relationship between the MLA cell size and the magnitude of the luminous flux on the LCOS. In FIG. 5, (a) is a schematic diagram when the cell size is reduced as indicated by 16-1 to 16-2 in the MLA 16. FIG. That is, the cell size range of the MLA is the same, but the cell size is reduced. (b) shows a light-receiving surface 34 of the LCOS 30 that receives illumination light supplied to the LCOS 30 and a range 35 of light supplied to the LCOS 30. When the MLA cell size is reduced, the range 35 of the luminous flux irradiated to the LCOS 30 The portion of the LCOS 30 protruding from the light-receiving surface 34 is reduced, and the luminous flux is narrowed, so that the light utilization rate is increased. Conversely, the tolerance of the light receiving surface 34 of the LCOS 30 with respect to the range 35 of light supplied to the LCOS 30 is reduced.

FIG. 6 is a diagram showing the relationship between the range (luminous flux) of light supplied to the LCOS and the light amount change rate.
(a) shows a case where the range 35 of light supplied to the LCOS 30 is the same size as the area of the light receiving surface 34 of the LCOS, and (b) shows a case where it is larger than the light receiving surface 34 of the LCOS. shows the result of simulating the light amount change rate in (a). In (b), the horizontal axis represents the range 35 (XL, YL) of light supplied to the LCOS when the area determined by the size (X, Y) of the light receiving surface 34 of the LCOS is taken as 100%, and the vertical axis. indicates the rate of change in the amount of light with which the light receiving surface 34 of the LCOS 30 is irradiated. As shown in (b), when the light range 35 increases to 119%, the light amount change rate decreases to 81%. Conversely, when the light range 35 becomes smaller, the light amount change rate is proportional to the increasing direction.

Next, the lack of image caused by reducing the MLA cell size is caused by the rotation of the LCOS.

FIG. 7 is a diagram for explaining variations in polarization angle of LCOS. In FIG. 7, the LCOS liquid crystal layer has variations in the polarization angle for each component, causing degradation in contrast (luminance ratio of all white/all black). As shown in (a), when the deviation of the polarization angle is θ degrees in the counterclockwise direction, the LCOS itself is adjusted by rotating in order to absorb the variation in the polarization angle that occurs as shown in (b). can be considered. Therefore, it is necessary to rotate the entire LCOS (video display device 30) clockwise by θ degrees. This also applies to LCDs having a liquid crystal layer as well.

FIG. 8 is a diagram for explaining misalignment of the PBS. In FIG. 8, if the PBS 20 is attached to the housing 120 in a floating state during attachment, the LCOS 30 must be rotationally adjusted to match the deviation.

Similarly, in the case of the DLP of FIG. 3 as well, if the triangular prism 21 is attached to the housing 120 in a floating state during attachment, the DLP 31 must be rotationally adjusted to match the deviation.

9A and 9B are diagrams for explaining image dropout caused by reducing the MLA cell size when the LCOS described in FIGS. 7 and 8 is rotationally adjusted.

In FIG. 9, (a) shows a case where the tolerance of the light receiving surface 34 of the LCOS 30 with respect to the range 35 of the light supplied to the LCOS 30 is large before the MLA cell size is reduced, and the rotation of the LCOS 30 is adjusted. Since the light-receiving surface 34 of the LCOS 30 is within the range 35 of the light supplied to the LCOS 30 even after the LCOS 30 is supplied, image loss does not occur. On the other hand, as shown in (b), when the MLA cell size is reduced in order to increase the light utilization rate, the tolerance of the light receiving surface 34 of the LCOS 30 with respect to the range 35 of light supplied to the LCOS 30 is reduced. When the rotation adjustment is performed, there is a problem that the light receiving surface 34 of the LCOS 30 protrudes from the range 35 of the light supplied to the LCOS 30, resulting in image loss. Note that LCDs and DLPs also have similar problems.

In view of the above problems, the present embodiment provides an HMD capable of reducing the cell size of the MLA without adversely affecting the image and increasing the light utilization efficiency by adjusting the position of the MLA. A specific example of this embodiment will be described below.

10A and 10B are diagrams for explaining image defect caused by reducing the MLA cell size and position adjustment of the MLA in this embodiment. In FIG. 10, as shown in (a) and (b), when light loss (image loss) occurs due to rotation adjustment of the LCOS, the MLA is rotated as shown in (c), and the light is supplied to the LCOS. By rotating the light receiving surface 34 of the LCOS in the same manner as the light receiving surface 34 of the LCOS, image loss is prevented.

Next, the necessary conditions and adjustment method for adjusting the MLA will be described.

FIG. 11 shows an example of the shape of the MLA in this embodiment. At present, as shown in (a), the outermost shape 16-3 of the MLA and the MLA cell range 16-4 are rectangular in shape, making it difficult to adjust the rotation. As an example of countermeasures, in (b) the outermost shape 16-3 is a circle and the shape of the MLA cell range 16-4 is a square, and in (c) the outermost shape 16-3 is partially arcuate, The shape of the MLA cell range 16-4 is a square, (d) the outermost shape 16-3 is a circle, the shape of the MLA cell range 16-4 is a circle, and (e) the outermost shape 16-3 is partially The shape has an arc, and the shape of the MLA cell range 16-4 is a circle. Countermeasure examples (b), (c), (d), and (e) have an MLA adjustment hole 16-5 in common.

FIG. 12 shows another shape example of the MLA in this embodiment. FIG. 12 shows a front view and a side view. In FIG. 11, the shape of the outermost shape 16-3 is a circle or an arc, but in FIG. 12, part of the MLA may be a circle or an arc. In (f), the outermost shape 16-3 is square, the MLA cell range 16-4 is circular, and has a cylindrical shape in the thickness direction. In (g), the outermost shape 16-3 is square, the MLA cell range 16-4 is arc-shaped, and has a cylindrical shape in the thickness direction. Countermeasure examples (f) and (g) have an MLA adjustment hole 16-5 in common.

Even if the shape of the MLA cell range is a square, a circle, or an arc, there is no problem in performance as long as the design value (F value) is satisfied.

FIG. 13 shows the shape and fixing method of the mounting case for mounting the MLA in the embodiment. The mounting case 130 is shaped to receive the MLA in a V shape. The mounting of the MLA will be described by taking FIG. 12(f), which is an example of the shape of the MLA, as an example. After that, the spring 16-6 is inserted and fixed between the mounting case 130 and the MLA. At this time, the spring presses the outermost shape 16-3 of the MLA so as not to block the passage of light. This also applies to FIG. 12(g). In the case of FIG. 11, the arc portion of the outermost shape 16-3 of the MLA is mounted on the V-shaped mounting case and similarly fixed with a spring.

FIG. 14 shows an MLA adjustment method in the example. Taking FIG. 12(f), which is an example of the shape of the MLA, as an example, an adjustment pin 16-7 is inserted into the MLA adjustment hole 16-5 to perform rotational adjustment. In this way, the MLA 16 has a holding structure capable of attitude adjustment.

FIG. 15 is a schematic configuration diagram of the image display unit of the HMD in this embodiment. In FIG. 15, the same components as in FIG. 1 are denoted by the same reference numerals, and descriptions thereof are omitted. 15 differs from FIG. 1 in that the MLA 16 is fixed to the mounting case 130 with a spring 16-6. Thus, even if the MLA 16 is fixed, it can be configured to rotate during rotation adjustment.

FIG. 16 is a schematic configuration diagram of a video unit of the video display device. There is a dummy area 36 (black display area) outside the light receiving surface 34 of the LCOS, and an electrode area 37 and an insulating film area (polyimide) 38 further outside thereof. When the light flux hits the electrode area 37 and the insulating film area 38, the light is scattered and reflected and displayed as stray light outside the image. The electrode area 37 is located at 110% or more when the dimension of the light receiving surface 34 (X, Y) of the LCOS is 100%. Normally, the area after the electrode area 37 is devised to block light, but if the cell size of the MLA is reduced and the range of light is reduced to 110% or less, stray light can be prevented without any devising for blocking light.

Note that the configuration of FIG. 16 also applies to the video display device 60 (LCD) and the video display device 31 (DLP).

FIG. 17 is a processing flowchart of MLA rotation adjustment in this embodiment. In FIG. 17, the MLA rotation adjustment is performed in the LCOS adjustment (position, rotation) process of the HMD manufacturing process. That is, in FIG. 17, when the LCOS adjustment is started (S101), first, in step S102, conventional LCOS focus adjustment in the optical axis direction and position adjustment in the rotational direction due to variations in positioning accuracy of components are performed. Then, in step S103, image missing is checked, and if there is image missing, MLA rotation adjustment is performed in step S104. Then, the process returns to step S103, and the MLA rotation adjustment is performed until the lack of image disappears. When the lack of image disappears, the LCOS adjustment is completed in step S105.

17 can be applied even when the image display device (LCOS) 30 is the image display device 60 (LCD) or the DLP 31, and the LCOS adjustment in FIG. 17 can be replaced with LCD adjustment or DLP adjustment.

As described above, according to the present embodiment, it is possible to provide an HMD capable of reducing the cell size of the MLA and increasing the light utilization efficiency without adversely affecting the image, and also as a countermeasure against stray light.

Although the embodiments have been described above, the present invention is not limited to the above-described embodiments, and includes various modifications. For example, the above-described embodiments have been described in detail in order to explain the present invention in an easy-to-understand manner, and are not necessarily limited to those having all the described configurations.

1: HMD, 10: illumination system, 16: microlens array (MLA), 16-1, 16-2: cell size, 16-3: outermost shape of MLA, 16-4: MLA cell range, 16-5: MLA adjustment hole, 16-6: spring, 16-7: adjustment pin, 18: imaging lens, 20: PBS, 21: triangular prism, 30: video display device (LCOS), 31: video display device (DLP) , 34: light receiving surface of LCOS, 35: range of light supplied to LCOS, 36: dummy area (black display area), 37: electrode area, 38: insulating film area (polyimide), 40: projection system, 50: Light guide part, 60: image display device (LCD), 100: image display part, 120: housing, 130: mounting case

Claims (8)

An image display device that generates an image, an illumination system that supplies illumination light to the image display device, and an optical element that guides the illumination light to the image display device and causes the light from the image display device to enter a projection system. A head-mounted display device comprising
The illumination system has a microlens array,
The cell size of the microlens array is configured such that the range of the irradiation light supplied to the image display device is a predetermined range larger than the light receiving surface of the image display device,
A head-mounted display device, wherein the microlens array has a holding structure capable of adjusting its attitude. In the head mounted display device according to claim 1,
When the area of the light receiving surface of the image display device is 100%,
The head mounted display device, wherein the predetermined range larger than the light receiving surface of the image display device is from 100% to 110%. In the head mounted display device according to claim 1,
A head-mounted display device, wherein the shape of the microlens array is a shape partially circular or partially arcuate. In the head mounted display device according to claim 3,
Having a mounting case for mounting the microlens array,
The head-mounted display device, wherein the mounting case has a V-shape, and the V-shape receives the shape of the microlens array having a circle or a partial arc. In the head mounted display device according to claim 4,
A head mount display device, wherein the microlens array is pressed and fixed to the mounting case by a pressing member. In the head mounted display device according to claim 5,
A head mounted display device, wherein the pressing member is a spring. In the head mounted display device according to claim 1,
The image display device is an LCOS or LCD,
A head mount display device, wherein the optical element is a PBS. In the head mounted display device according to claim 1,
The image display device is a DLP,
A head mount display device, wherein the optical element is a triangular prism.

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