JP7615732B2 - Eyepiece image display device - Google Patents

Description

The present invention relates to an eyepiece image display device.

In an eyepiece image display device that is used close to the eye, the use of a Fresnel lens has been proposed in order to reduce the size of the device (see Patent Document 1).
However, Fresnel lenses, which use refraction to deflect light, have limitations on the angle at which they can deflect light, and Fresnel lenses that use refraction also have limitations on the viewing angle.

Japanese Patent Application Publication No. 7-244246

The objective of the present invention is to provide a compact eyepiece image display device that can deflect light at a large angle to provide a large viewing angle.

The present invention solves the above problems by the following means. Note that, for ease of understanding, the following description will use symbols corresponding to the embodiments of the present invention, but the present invention is not limited to these.

The first invention is an eyepiece image display device (1) that includes a display element (10) and a substantially flat eyepiece optical element (20) that is arranged opposite the display surface side of the display element (10) and deflects light from the display element (10), the eyepiece optical element (20) being a Fresnel lens that includes a total reflection lens region (22) that totally reflects and deflects light.

The second invention is an eyepiece image display device (1) according to the first invention, characterized in that the eyepiece optical element (20) is provided with a refractive lens area (21) that is located closer to the center than the total reflection lens area (22) and that refracts and deflects light, the total reflection lens area (22) and the refractive lens area (21) can be divided by a boundary line, and when light that is perpendicularly incident on the surface of the eyepiece optical element (20) opposite the Fresnel lens surface is defined as perpendicular incident light, the direction in which the perpendicular incident light is deflected by the refractive lens area (21) at a position adjacent to the boundary line and the direction in which the perpendicular incident light is deflected by the total reflection lens area (22) at a position adjacent to the boundary line are substantially the same direction.

A third invention is an eyepiece image display device (1) according to the first or second invention, characterized in that the eyepiece optical element (20) is provided with a refractive lens region (21) that is located closer to the center than the total reflection lens region (22) and refracts and deflects light, the total reflection lens region (22) and the refractive lens region (21) can be divided by a boundary line, and if light that is perpendicularly incident on the surface of the eyepiece optical element (20) opposite the Fresnel lens surface is defined as perpendicular incident light, the proportion of light that is deflected and emitted by the refractive lens region (21) at a position adjacent to the boundary line and the proportion of light that is deflected and emitted by the total reflection lens region (22) at a position adjacent to the boundary line are substantially the same.

The fourth invention is an eyepiece image display device (1) according to the first invention, in which the eyepiece optical element (20) is provided with a refractive lens area (21) that is provided closer to the center than the total reflection lens area (22) and that refracts and deflects light, the total reflection lens area (22) and the refractive lens area (21) can be divided by a boundary line, and light that is perpendicularly incident on the surface of the eyepiece optical element (20) opposite to the Fresnel lens surface is defined as perpendicular incident light, and the perpendicular incident light is deflected by the refractive lens area (21) at a position adjacent to the boundary line. The eyepiece image display device (1) is characterized in that, when the angle of incidence of the perpendicular incident light on the refracting surface of the Fresnel lens shape provided in the lens area (21) is α1, the angle of incidence of the perpendicular incident light on the rising surface of the Fresnel lens shape provided in the total reflection lens area (22) at a position adjacent to the boundary line is α2, and the refractive index of the material constituting the eyepiece optical element (20) is N, the relationship of α1 = α2 = ASIN((SIN(90 + α1 - ASIN((SIN(α1)) x N)))/N) is satisfied.

The present invention makes it possible to provide a compact eyepiece image display device that can deflect light at a large angle to provide a large viewing angle.

1 is a diagram showing an outline of an eyepiece image display device according to the present invention; 2 is a cross-sectional view of the eyepiece optical element 20 taken along the line indicated by the arrows A--A in FIG. 2 is an enlarged cross-sectional view of a boundary portion between a refractive lens region 21 and a total reflection lens region 22. FIG.

The best mode for carrying out the present invention will be described below with reference to the drawings.

First Embodiment
FIG. 1 is a diagram showing an outline of an eyepiece image display device according to the present invention.
Note that the figures shown below, including FIG. 1, are schematic views, and the size and shape of each part are exaggerated or omitted as appropriate for ease of understanding.
In the following description, specific numerical values, shapes, materials, etc. are given, but these can be changed as appropriate.
In this specification, terms specifying shapes or geometric conditions, such as parallel and orthogonal, are intended to include not only their strict meanings but also states that have a similar optical function and have an error that can be considered as parallel or orthogonal.
In this specification, the terms plate, sheet, film, etc. are used, and in general usage, they are used in the order of thickness, plate, sheet, film, etc., and this specification follows that order. However, since such distinction in usage has no technical meaning, these terms can be used interchangeably as appropriate.
In this specification, the sheet surface refers to the surface of each sheet that is in the planar direction of the sheet when viewed as a whole. The same applies to plate surfaces and film surfaces.
In the present invention, the term "transparent" refers to a material that transmits at least light of a wavelength to be used. For example, even if a material does not transmit visible light, if it transmits infrared light, it is treated as transparent when used for infrared applications.
It should be noted that the specific numerical values specified in this specification and claims should be treated as including a general error range. In other words, a difference of about ±10% means that there is no substantial difference, and values set within a range slightly exceeding the numerical range of this invention should be interpreted as being substantially within the scope of this invention.

The eyepiece image display device 1 of this embodiment includes two sets of a display element 10 and an eyepiece optical element 20. The display element 10 and the eyepiece optical element 20 are held in their relative positions by a housing (not shown). This housing is also provided with a mounting member such as a belt (not shown), and the eyepiece image display device 1 is a head-mounted device known as a head-mounted display, which allows the user to view images while wearing it on their head.

The display element 10 is a small display element with a diagonal screen size of about 2 to 4 inches, and is configured using, for example, an LCD (liquid crystal display) or an OLED (organic light emitting diode). The display elements 10 are arranged with the centers of the display surfaces 10a spaced apart from each other by approximately 60 to 70 mm, in accordance with the interpupillary distance of the human eye.

The eyepiece optical element 20 is configured to have approximately the same size as the screen size of the display element 10, and is disposed along the display surface 10a of the display element 10, i.e., disposed facing the display surface 10a. The gap distance d between the display element 10 and the eyepiece optical element 20 is preferably 2 mm or less, and the display element 10 and the eyepiece optical element 20 may be bonded together to set the gap distance d between them to 0 mm. A smaller gap distance d is advantageous for overall miniaturization, and since the image light emitted from the display element 10 enters the eyepiece optical element 20 without spreading, the image light can be made to enter the eyepiece optical element 20 approximately perpendicularly.
In the following description, the side of the display element 10 from which image light is emitted is referred to as the observation side, and the opposite side is referred to as the back side.

Figure 2 is a cross-sectional view of the eyepiece optical element 20 taken along the position of the arrow A-A in Figure 1. The eyepiece optical element 20 is composed of a Fresnel lens that deflects the image light emitted by the display element 10 and allows the user to view an enlarged virtual image. More specifically, the eyepiece optical element 20 can be configured as a substantially flat Fresnel lens sheet on the observation side (Fresnel lens surface) in which a circular Fresnel lens shape in which a plurality of unit lenses are arranged concentrically is formed. Here, "substantially flat" means that the observation side surface on which the fine Fresnel lens shape is formed is flat when it is considered to be substantially flat.

The eyepiece optical element 20 can be formed, for example, from an ultraviolet-curable resin such as urethane acrylate or epoxy acrylate, but may also be formed from other ionizing radiation-curable resins such as electron beam-curable resins. The eyepiece optical element 20 can also be configured to include a substrate layer (not shown) as a base for forming the Fresnel lens shape. In this case, the eyepiece optical element 20 can be formed, for example, by an ultraviolet molding method in which one surface (the surface on the observation side) of the substrate layer is pressed against a mold filled with ultraviolet-curable resin to form a circular Fresnel lens shape, and the resin is irradiated with ultraviolet light to harden it, and then released from the mold. The method for forming the eyepiece optical element 20 may be selected as appropriate and is not limited to this.

The eyepiece optical element 20 of this embodiment includes a refractive lens area 21 and a total reflection lens area 22 .
The refractive lens region 21 is provided closer to the center than the total reflection lens region 22, and is a region that refracts and deflects light.
In the refractive lens region 21, unit lens shapes 210 are arranged concentrically from the center to the periphery. Each unit lens shape 210 has a rising surface 211 and a refractive surface 212 in the cross section shown in FIG.
The refractive lens region 21 refracts and deflects light, but the angle (α1 in FIG. 3 described below) that the refractive surface 212 makes with the plate surface (sheet surface) direction of the eyepiece optical element 20 increases toward the outer side, until it reaches an angle at which light perpendicularly incident on the plate surface of the eyepiece optical element 20 is totally reflected by the refractive surface 212. Therefore, there is a limit to the angle at which light perpendicularly incident on the plate surface of the eyepiece optical element 20 can be deflected by the refractive lens region 21 alone, and although this depends on the refractive index of the eyepiece optical element 20, the limit is approximately 40 degrees, or about 80 degrees in terms of the field of view.

Therefore, in this embodiment, a total reflection lens area 22 is further provided.
Total reflection lens region 22 is provided outside refractive lens region 21 and is a region that deflects light by total reflection. That is, in the Fresnel lens of this embodiment, the central portion where the deflection angle of light is small is composed of a refractive Fresnel lens, and the peripheral portion where light needs to be deflected greatly is composed of a total reflection Fresnel lens.
In total reflection lens region 22, unit lens shapes 220 are arranged concentrically from a position adjacent to refractive lens region 21 toward the periphery. Unit lens shape 220 has a rising surface 221 and a total reflection surface 222 in the cross section shown in FIG.
In the total reflection lens region 22 , light that is perpendicularly incident on the plate surface of the eyepiece optical element 20 is totally reflected at the total reflection surface 222 , and then refracted at the rising surface 221 before emerging.
By providing the total reflection lens region 22, it is possible to obtain a viewing angle that exceeds the viewing angle limit provided by the refractive lens region 21.

Here, the refractive lens region 21 and the total reflection lens region 22 have in common that they both deflect light before emitting it. However, the refractive lens region 21 refracts and deflects light, whereas the total reflection lens region 22 totally reflects light and then further refracts and deflects it, which is different. Therefore, at the boundary between the refractive lens region 21 and the total reflection lens region 22, if the directions and amounts of light emitted from the refractive lens region 21 and the total reflection lens region 22 are not aligned, the boundary will be visible, which is undesirable. Therefore, at the boundary between the refractive lens region 21 and the total reflection lens region 22, it is desirable that the directions of the light emitted from the refractive lens region 21 and the light emitted from the total reflection lens region 22 are approximately the same (called the direction condition), and further, it is desirable that the proportions of the emitted light are approximately the same (called the proportion condition).

FIG. 3 is an enlarged cross-sectional view of the boundary between the refractive lens region 21 and the total reflection lens region 22. As shown in FIG.
The boundary between the refractive lens region 21 and the total reflection lens region 22 is the position of a rising surface 221 of a unit lens shape 220 in the total reflection lens region 22 adjacent to a unit lens shape 210 in the refractive lens region 21 .

(Regarding directional conditions)
In order to make the boundary line invisible, first, the direction in which the vertically incident light is deflected by the refractive lens region 21 located adjacent to the boundary line and the direction in which the vertically incident light is deflected by the total reflection lens region 22 located adjacent to the boundary line must be substantially the same. That is, in FIG. 3, the angles β1 and β2, which are the directions in which the emitted light LA2 and the emitted light LB3 proceed, must be substantially the same, and therefore the emitted light LA2 and the emitted light LB3 proceed substantially parallel to each other.
Here, "angle β1 and angle β2 are substantially the same" does not necessarily mean that they are completely the same, but rather that some difference in angle due to variation is permitted. Specifically, for example, it is preferable that the absolute value of β1-β2 is within 2 degrees, and more preferably within 1 degree.
By satisfying this directional condition, the boundary can be made less noticeable.

(Regarding the ratio conditions)
In addition, in order to make the boundary line invisible, it is necessary that the proportion of light that is deflected and emitted by the refractive lens region 21 adjacent to the boundary line and the proportion of light that is deflected and emitted by the total reflection lens region 22 adjacent to the boundary line are approximately the same.
The loss of light entering the eyepiece optical element 20 is the same in the refractive lens region 21 and the total reflection lens region 22, so this will be excluded from the discussion. In the refractive lens region 21, when the light refracts at the refractive surface 212, a part of the light is reflected, resulting in a loss. On the other hand, in the total reflection lens region 22, since the total reflection is performed at the total reflection surface 222, no light is lost, but when the light refracts at the rising surface 221, a part of the light is reflected, resulting in a loss. Therefore, if the incidence angle α1 at which the perpendicular incident light is incident on the refractive surface 212 at a position adjacent to the boundary line and the incidence angle α2 at which the perpendicular incident light is incident on the rising surface 221 at a position adjacent to the boundary line are approximately the same, the proportions of light lost will be equal, and the proportions of light emitted from the adjacent unit lens shapes 210 and 220 can be equalized.
Here, the incidence angle α1 and the incidence angle α2 being substantially the same does not necessarily mean that they are completely the same, but rather that some difference in angle due to variation is allowed. Specifically, for example, it is preferable that the absolute value of α1-α2 is within 1 degree, and more preferably within 0.5 degrees.
By satisfying this ratio condition, the boundary can be made less noticeable.

(When both the direction and ratio conditions are met)
At least one of the above-mentioned direction condition and ratio condition must be satisfied, but it is more preferable to satisfy both conditions.
When the angles of the various parts are set as shown in FIG. 3 and the refractive index of the material that constitutes the eyepiece optical element 20 is N, the following relationship holds:
β1=90+α1-ASIN((SIN(α1))×N)
α2=ASIN((SIN(β2))/N)
If β1 = β2, then
α1=α2=ASIN((SIN(90+α1-ASIN((SIN(α1))×N)))/N)
This means that the following is satisfied.
Also,
δ-α2=90-δ
Therefore,
δ=(90+α2)/2
It becomes.

From the above formulas, in order to satisfy both the directional condition and the ratio condition, for example, when N = 1.49, α1 = α2 = 36.895 degrees and δ = 63.448 degrees should be set, and when N = 1.5, α1 = α2 = 36.544 degrees and δ = 63.272 degrees should be set. By satisfying both the directional condition and the ratio condition in this way, the eyepiece image display device 1 can provide an image with a wide viewing angle without any boundaries being visible.

As described above, the eyepiece image display device 1 of this embodiment is provided with the refractive lens area 21 and the total reflection lens area 22, and therefore can provide an image with a wide viewing angle.
Furthermore, by satisfying either the direction condition or the ratio condition, the boundary line between the refractive lens region 21 and the total reflection lens region 22 can be made inconspicuous.
Furthermore, by satisfying both the direction condition and the ratio condition, the boundary line between the refractive lens region 21 and the total reflection lens region 22 can be made invisible.
Furthermore, since it is not necessary to use a plurality of overlapping optical elements, a small-sized eyepiece image display device can be achieved.

(Modifications)
The present invention is not limited to the above-described embodiment, and various modifications and variations are possible, and these are also within the scope of the present invention.

(1) In the embodiment, the eyepiece image display device 1 has been described as a head-mounted device. However, the present invention is not limited to this, and may be configured to be held in the hand for observation, or may be configured to be fixed to a wall or various devices.

(2) In the embodiment, an eyepiece image display device 1 including two pairs of a display element 10 and an eyepiece optical element 20 has been described as an example. However, the present invention is not limited to this, and may be an eyepiece image display device including only one pair of a display element 10 and an eyepiece optical element 20.

The embodiments and variations can be used in any suitable combination, but detailed explanations will be omitted. Furthermore, the present invention is not limited to the embodiments described above.

REFERENCE SIGNS LIST 1 Eyepiece image display device 10 Display element 10a Display surface 20 Eyepiece optical element 21 Refraction lens region 22 Total reflection lens region 210 Unit lens shape 211 Upward facing surface 212 Refraction surface 220 Unit lens shape 221 Upward facing surface 222 Total reflection surface

Claims (4)

A display element;
an eyepiece optical element having a substantially flat plate shape, disposed opposite to a display surface side of the display element and deflecting light from the display element;
Equipped with
the eyepiece optical element is a Fresnel lens including a total reflection lens area that totally reflects and deflects light,
a gap between the display element and the eyepiece optical element is 2 mm or less;
the eyepiece optical element includes a refractive lens region that is disposed closer to the center than the total reflection lens region and that refracts and deflects light,
The total reflection lens region and the refractive lens region may be separated by a boundary line,
The light perpendicularly incident on the surface of the eyepiece optical element opposite to the Fresnel lens surface is defined as perpendicular incident light,
The incident angle of the perpendicular incident light on the refractive surface of the Fresnel lens shape provided in the refractive lens region at a position adjacent to the boundary line is defined as α1,
The incident angle of the perpendicular incident light on the rising surface of the Fresnel lens shape provided in the total reflection lens region at a position adjacent to the boundary line is defined as α2,
When the refractive index of the material constituting the eyepiece optical element is N,
α1=α2=ASIN((SIN(90+α1-ASIN((SIN(α1))×N)))/N)
An eyepiece image display device that satisfies the above relationship . 2. The eyepiece image display device according to claim 1,
The display element and the eyepiece optical element are cemented together. 3. The eyepiece image display device according to claim 1,
the eyepiece optical element includes a refractive lens region that is disposed closer to the center than the total reflection lens region and that refracts and deflects light,
The total reflection lens region and the refractive lens region may be separated by a boundary line,
If the light perpendicularly incident on the surface of the eyepiece optical element opposite to the Fresnel lens surface is defined as perpendicular incident light, then
a direction in which the vertically incident light is deflected by the refractive lens region at a position adjacent to the boundary line and a direction in which the vertically incident light is deflected by the total reflection lens region at a position adjacent to the boundary line are substantially the same direction;
An eyepiece image display device comprising: 4. The eyepiece image display device according to claim 1,
the eyepiece optical element includes a refractive lens region that is disposed closer to the center than the total reflection lens region and that refracts and deflects light,
The total reflection lens region and the refractive lens region may be separated by a boundary line,
If the light perpendicularly incident on the surface of the eyepiece optical element opposite to the Fresnel lens surface is defined as perpendicular incident light, then
a ratio of the perpendicular incident light deflected by the refractive lens region at a position adjacent to the boundary line and emitted is substantially equal to a ratio of the perpendicular incident light deflected by the total reflection lens region at a position adjacent to the boundary line and emitted;
An eyepiece image display device comprising:

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