JP2007010830A - Image display optical system and image display apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To moderately suppress the occurrence of a twin image while securing a wide viewing field angle and a wide exit pupil, regarding an image display optical system. <P>SOLUTION: The image display optical system includes; a substrate 1 to which a luminous flux from an image display element 2 is guided so as to form an optical path therein; and a plurality of parallel partial reflection surfaces 61 and 62 inserted into the optical path. The whole width δα of an angle difference between two or more continuous partial reflection surfaces 61 and 62 satisfies an inequality (1): δα×n<1. In the inequality (1), (n) denotes the refractive index of the substrate 1 and a unit of δα is a minute. When the inequality (1) is satisfied, viewing from an observation eye opposite to the partial reflection surface, the deviation δα×n of the twin image in the image display element is suppressed below as small as one pixel, then, the twin image becomes inconspicuous certainly. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image display optical system such as an image combiner, and an image display device such as a head mounted display and an eyeglass display.

One eyeglass display that displays an enlarged virtual image of an image display element superimposed on the scenery of the outside world is one in which the viewing angle (FOV) and the exit pupil are enlarged (Patent Document 1, etc.).
As described in FIG. 26 of Patent Document 1, etc., in this technique, a plurality of light beams reflected by the partial reflection surfaces are provided with a plurality of partial reflection surfaces (half mirrors) provided in parallel in the transparent substrate. To form one large exit pupil. If a plurality of partial reflection surfaces are provided in this way, the angle range of the guided light beam is also enlarged, so that the viewing angle is also enlarged simultaneously with the exit pupil.
Special table 2003-536102 gazette

  However, when the inventor actually produced a prototype and placed the observation eye on the exit pupil, it was found that the magnified virtual image of the image display element looks double, which is very troublesome. The cause is thought to be the manufacturing error of the board, but even if the manufacturing error is suppressed, the direct cause of the double image can be determined and taken into consideration when considering the ease of manufacturing and manufacturing cost. It is necessary to estimate whether it should be suppressed to the range.

The present invention has been made in view of such circumstances, and an object thereof is to provide an image display optical system capable of moderately suppressing the generation of a double image while ensuring a wide viewing angle and a wide exit pupil. To do.
It is another object of the present invention to provide an image display apparatus that has a wide viewing angle and a wide exit pupil, and is capable of moderately suppressing the generation of double images.

An image display optical system according to the present invention includes a substrate on which a light beam from an image display element is introduced to form an optical path therein, and a plurality of parallel partial reflection surfaces inserted into the optical path. The total width δα of the angle difference between two or more continuous partial reflection surfaces satisfies the following expression (1).
δα * n <1 (1)
Where “n” is the refractive index of the substrate and “δα” is in minutes.

Furthermore, it is preferable that the total width δα of the angle difference between the N or more continuous reflection surfaces expressed by the following formula (2) satisfies the above formula (1).
N = INT [2 / (T * tanα _2i )] + 2 (2)
However, “T” is the thickness of the substrate, “α _2i ” is the design value of the angle formed by the partial reflection surface and the normal of the substrate, and the function INT [A] of A is an integer part of A.

Furthermore, the total width δα of the angle difference may satisfy the following formula (3).
δα * <0.5 (3)
Furthermore, the total width δα of the angle difference may satisfy the following formula (4).
δα * n <0.2 (4)
When the substrate propagates while reflecting the light beam on the inner surface, the total width δα of the angle difference and the angle difference δθ of the substrate surface used for the inner surface reflection satisfy the following expression (5). .

(Δα + δθ) * n <1 (5)
However, the unit of “δθ” is minutes.
Further, the total width δα of the angle difference and the angle difference δθ of the substrate surface used for the internal reflection preferably satisfy the following expression (6).
(Δα + δθ) * n <0.5 (6)
Further, it is preferable that the total width δα of the angle difference and the angle difference δθ of the substrate surface used for the internal reflection satisfy the following expression (7).

(Δα + δθ) * n <0.2 (7)
The image display device of the present invention includes an image display element, a collimator that converts a light beam from the image display element into a parallel light beam, and the image display optical system of the present invention that guides the light beam. And
The image display device of the present invention may further include mounting means for mounting the image display element, the collimator, and the image display optical system on the observer's head in a predetermined positional relationship.

  According to the image display optical system of the present invention, it is possible to moderately suppress the occurrence of double images while ensuring a wide viewing angle and a wide exit pupil. In addition, according to the image display device of the present invention, the generation of double images can be moderately suppressed while having a wide viewing angle and a wide exit pupil.

[Principle of the present invention]
The principle of the present invention will be described with reference to FIG.
In FIG. 1A, the display light beam emitted from the image display element 2 is collimated by the collimator lens 4 and then enters the substrate 1. Of this display light beam, a certain light ray L1 having a certain angle of view propagates while being internally reflected in the substrate 1 and is reflected by parallel partial reflection mirrors 61 and 62 to become light rays L2 ′ and L3 ′. 1 to the outside, and simultaneously enter the observation eye.

If the angles of the two light beams L2 ′ and L3 ′ are the same, the observer sees the two light beams L2 ′ and L3 ′ as light beams having the same angle of view. On the other hand, if the angles of the two light beams L2 ′ and L3 ′ are shifted, the two light beams L2 ′ and L3 ′ appear as light beams having different angles of view to the observer. At this time, a double image is observed.
To simply avoid this double image, the angle difference δα between the partial reflection mirrors 61 and 62 may be made zero in order to make the angles of the two light beams L2 ′ and L3 ′ coincide.

However, the present inventor has found that the double image is surely inconspicuous if at least conditional expression (1) is satisfied. Further, the present inventor has found that it is more preferable that the conditional expression (3) is satisfied, and more preferably, the conditional expression (4) is satisfied.
δα * n <1 (1)
δα * n <0.5 (3)
δα * n <0.2 (4)
Here, “n” is the refractive index of the substrate.

(Derivation of conditional expressions (1), (3), (4))
The derivation process of conditional expressions (1), (3), and (4) is as follows.
First, when the angle difference between two light beams having different angles of view by k pixels in the display light beam incident on the substrate 1 is denoted by φ, the angle difference φ, the pixel pitch p of the image display element 2, and the focal point of the collimator lens 4. The relationship of the following formula (11) is established between the distances f.

k * p = f * tanφ (11)
Further, the following equation (12) is established between the angle difference φ and the angle difference φ _n within the substrate of the same two rays by Snell's law.
sinφ = n * sinφ _n (12)
Further, in a general image display element 2 used for an eyeglass display or the like, one side of the effective area is about several mm, and VGA or QVGA is adopted for the pixel arrangement. In that case, the pixel pitch p of the image display element 2 is about 10 μm. Further, the focal length f of the collimator lens 4 is generally about 20 mm from the size of the image display element 2 and the observation angle of view of the observer.

Therefore, p = 10μm, f = 20mm , and Sinfai～fai, an approximate expression of sin [phi _n to [phi] _n, the above Expression (11) is applied to (12). Then, when the units of the angle differences φ and φ _n are changed to [minutes] and the formula is simplified, it can be seen that the angle differences φ and φ _n are expressed as the following formula (13).
φ ≒ 2k,
φ _n ≒ 2k / n (13)
Therefore, if the angle difference between the two light beams L2 ′ and L3 ′ toward the observation eye is φ _n , the two light beams L2 ′ and L3 ′ are equivalent to k = (φ _n * n / 2) pixels for the observer. Only the light beam with the angle of view shifted appears. That is, the shift amount of the double image observed at this time is (φ _n * n / 2) pixels.

However, the present inventor considered that there was no problem at all when the shift amount (φ _n * n / 2) of the double image was not recognized by the observer (allowable range). As a result of experiments conducted by the present inventor, the permissible range was found to be within one pixel. Further, it has been found that it is preferably within 0.5 pixels, more preferably within 0.2 pixels.
Accordingly, a conditional expression for keeping the double image shift amount (φ _n * n / 2) within an allowable range (within 1 pixel, within 0.5 pixel, within 0.2 pixel) is as follows: 14), (15), and (16).

φ _n * n / 2 <1 (14)
φ _n * n / 2 <0.5 (15)
φ _n * n / 2 <0.2 (16)
Further, the angle difference φ _n between the two light beams L2 ′ and L3 ′ is twice the angle difference δα between the partial reflection mirrors 61 and 62, and φ _n = 2 * δα. Therefore, it is clear that the conditional expressions (1), (3), and (4) described above are derived from the expressions (14), (15), and (16).

(Derivation of conditional expressions (5), (6), (7))
Incidentally, the two light beams L2 ′ and L3 ′ shown in FIG. 1A have not only the same angle of view but also the same number of internal reflections in the substrate 1. Therefore, the parallelism between the two substrate surfaces A and A ′ used for the internal reflection has no influence on the angle difference φ _n between the two light beams L2 ′ and L3 ′.
However, actually, as shown in FIG. 1B, even if the angle of view is the same, two light beams L2 ′ and L3 ′ having different numbers of internal reflections may enter the observation eye at the same time.

In this case, since the parallelism of the surfaces A and A ′ used for the internal reflection affects the angle difference φ _n between the two light beams L2 ′ and L3 ′, a conditional expression for keeping the shift amount of the double image within an allowable range. Will be tougher.
Specifically, 2 light L2 ', L3' when the internal reflection times between different, the angle difference phi _n of 2 light L2 ', L3', and the angle difference δα partially reflecting mirror 61, the internal reflection The angle difference δθ between the provided surfaces A and A ′ is expressed by φ _n = 2 * (δα + δθ).

Therefore, in this case, the conditional expressions for keeping the double image shift amount within an allowable range (within 1 pixel, within 0.5 pixel, within 0.2 pixel) are the following expressions (5), (6 ), (7).
(Δα + δθ) * n <1 (5)
(Δα + δθ) * n <0.5 (6)
(Δα + δθ) * n <0.2 (7)
These conditional expressions (5), (6), and (7) are necessary because the distance D between the two light rays L2 ′ and L3 shown in FIG. And 2 mm). This is because if the distance D is narrower than the pupil diameter, the two light beams L2 ′ and L3 ′ may enter the pupil simultaneously.

On the other hand, when the distance D between the two light rays L2 ′ and L3 ′ shown in FIG. 1B is wider than the diameter (up to 2 mm) of the pupil of the observation eye, the conditional expressions (1), (3), (4) Is enough. This is because if the distance D is wider than the diameter of the pupil, there is no possibility that the two light beams L2 ′ and L3 ′ will enter the pupil of the observation eye at the same time.
(Derivation of interval D)
The formula for obtaining the distance D (when the sum of the incident angle and the reflection angle of the light beam of the display light beam in the partial reflection mirror is “acute angle”) will be described below.

In FIG. 2, light rays L2 ′ and L3 ′ are light rays having the same angle of view. The light beam L2 ′ is reflected by the first partial reflection mirror 61 after the internal reflection count n, and the light beam L3 ′ is reflected by the second partial reflection mirror 62 after the internal reflection count n + 2.
A point O in FIG. 2 is an origin (0, 0), a horizontal direction in FIG. 2 is an X direction, and a vertical direction in FIG. 2 is a Y direction.

At this time, the straight line R1 representing the second partial reflection mirror 62 is expressed by the following equation (21) by the design values α _2i of the arrangement angles α ₂₁ and α ₂₂ of the partial reflection mirrors 61 and 62. Here, “placement angle” is used to mean “angle formed with the substrate normal”.
y = x / tan α _2i (21)
Further, the straight line R2 representing the light beam that is the generation source of the light beam L3 ′ is expressed by the following equation (22) by the inner surface reflection angle α _T in the substrate 1 and the width D _{2 in} the x direction of one partial reflection mirror. Is done.

y = −x / tan α _T + D ₂ / tan α _T (22)
At this time, the x coordinate Xp of the intersection P between the straight line R1 and the straight line R2 is expressed by the following expression (23).
Xp = D ₂ * tan α _2i / (tan α _T + tan α _2i ) (23)
Further, if the coordinates of the generation source of the light beam L2 ′ are regarded as a point O ′ in FIG. 2, the following expression (24) is established.

D = D ₂ −Xp (24)
Further, the width D ₂ is expressed by the following expression (25) by the thickness T of the substrate 1 and the design value α _2i of the arrangement angle of the partial reflection mirrors 61 and 62.
D ₂ = T * tan α _2i (25)
Further, the inner surface reflection angle α _T is expressed by the following equation (26) by the arrangement angle α ₂ of the introduction mirror B that first reflects the light incident on the substrate 1.

α _T = 2 * (90 ° −α ₂ ) (26)
The following formula holds.
tan (90 ° −θ) = 1 / tan θ,
tan (2θ) = 2 * tan θ / [1- (tan θ) ² ] (27)
Further, when the sum of the incident angle and the reflection angle of the light beam at the partial reflection mirrors 61 and 62 is an “acute angle”, the following expression (28) is established.

α ₂ = α _2i (28)
When the above formulas (23), (24), (25), (26), (27), and (28) are rearranged, the interval D is expressed as the formula (29).
D = 2 * T * tan α _2i / [(tan α _2i ) ² +1] (29)
(Number of partial reflection mirrors, etc.)
In FIG. 1 and FIG. 2, the total number of partially reflecting mirrors is “2”, but in actuality it may be “3 or more”. In that case, each of the two continuous partial reflection mirrors must satisfy the above-described conditional expression so that the effect of reducing the double image is maintained even if the position of the observation eye changes.

  In addition, when the total number of partial reflection mirrors is “3 or more”, there is a possibility that rays having the same angle of view may simultaneously enter the pupil of the observation eye from two or more consecutive partial reflection mirrors. In that case, three or more continuous partial reflection mirrors must simultaneously satisfy the above-described conditional expression. That is, the full width δα of the angle difference between N consecutive partial reflection mirrors must satisfy the above-described conditional expression.

Here, the number N of partial reflection mirrors that should satisfy the conditional expression at the same time is expressed by the following expression (2).
N = INT [2 / (T * tanα _2i )] + 2 (2)
However, the function INT [A] of A is an integer part of A. The first term in the equation (2) indicates the number of partially reflecting mirrors that can simultaneously allow a light beam having a central field angle to enter the observer's pupil. The second term is a correction value for extending the formula for the central field angle to the peripheral field angle.

[First Embodiment]
A first embodiment of the present invention will be described with reference to FIGS. This embodiment is an embodiment of an eyeglass display.
FIG. 3 is an external view of the present eyeglass display. As shown in FIG. 3, the present eyeglass display is formed by fixing an image introducing unit U, an image display substrate 1 and the like to a frame F having a structure similar to that of a spectacle frame. When this eyeglass display is mounted on the observer's head by the frame F, the substrate 1 is disposed in front of the observation eye E, and the image introduction unit U is disposed at a position that does not obstruct the visual field of the observation eye E. .

  FIG. 4 is a schematic cross section of the optical system portion of the present eyeglass display. As shown in FIG. 4, the optical system portion includes an illumination optical system 3, an image display element 2, a collimator lens 4, a substrate 1, and the like. Among these, the illumination optical system 3, the image display element 2, and the collimator lens 4 are housed in the image introduction unit U. The optical member (here, the substrate 1) that is arranged in front of the observation eye E and superimposes the display light beam from the image display element 2 and the external light beam from the outside is a so-called “image combiner”.

  The image display element 2 is, for example, a transmissive LCD. One side of the effective area is about several mm, the pixel arrangement is VGA or QVGA, and the pixel pitch p is about 10 μm. The illumination optical system 3 is, for example, an optical system that combines an LED and a diffusion plate. The focal length f of the collimator lens 4 is about 20 mm. The substrate 1 is made of an optical material that is transparent to visible light, such as glass or plastic, and is a parallel plate in which the surface A ′ on the observer side and the surface A on the counter-observer side (external side) are parallel.

  Inside the substrate 1, an introduction mirror B which is a total reflection mirror and two partial reflection mirrors 61 and 62 parallel to each other are formed. Among these, the formation position of the introduction mirror B is in the vicinity of the position facing the image introduction unit U, and the posture thereof is inclined by a predetermined angle with respect to the surfaces A and A ′ of the substrate 1. Further, the portions where the partial reflection mirrors 61 and 62 are formed are in the vicinity of the position facing the observation eye E, and the posture thereof is inclined by a predetermined angle with respect to the surfaces A ′ and A of the substrate 1.

  In the above eyeglass display, the image display element 2 is illuminated from behind by the illumination optical system 3 and spatially modulates the incident light to generate a light beam for image display (display light beam). The display light beam becomes a parallel light beam in the collimator lens 4 and is guided into the substrate 1 from the surface A ′ of the substrate 1. In FIG. 4, only the display light beam having the central angle of view (only one representative light beam in the substrate 1) is shown.

  The display light beam incident on the inside of the substrate 1 is reflected by the introduction mirror B at a reflection angle smaller than 45 °, and then incident on the surface A ′ of the substrate 1 at an incident angle larger than the critical angle and totally reflected. Thereafter, the display light beam enters the surface A of the substrate 1 at the same incident angle and is totally reflected. Then, when the display light beam repeats internal reflection on the surfaces A ′ and A of the substrate 1 and propagates in the direction of the observation eye E, it sequentially enters the partial reflection mirrors 61 and 62 and receives the reflection action thereof. The reflected display light beam passes through the surface A ′ and enters the predetermined region EP outside the substrate 1.

Since the display light beam having a certain angle of view incident thereon is converted into a parallel light beam, each light beam of the parallel light beam is incident on the predetermined region EP at a common incident angle. In addition, the display light flux at each angle of view enters the predetermined area EP with a predetermined incident angle relationship.
When the pupil of the observation eye E is arranged at any location in such a predetermined area EP, the observer can observe the magnified virtual image of the image display element 2 at infinity on the outside world side. That is, the predetermined area EP functions as an exit pupil.

In addition, at least a part of the external light flux that arrives at the substrate 1 from the outside world passes through the substrate 1 and the partial reflection mirrors 61 and 62 and enters the exit pupil EP. Therefore, the observer can observe the scenery of the outside world together with the magnified virtual image.
In particular, in the present eyeglass display, since a plurality of partial reflection mirrors are provided, the exit pupil EP is correspondingly wide, and the angle range (that is, the viewing angle) of the display light beam that can reach the exit pupil EP is wide.

Here, in the present eyeglass display, as shown in FIG. 4, the posture of the partial reflection mirrors 61 and 62 reflects the display light beam immediately after being reflected by the surface A ′ on the viewer side toward the surface A ′. Is set. In this case, the sum of the incident angle and the reflection angle of the light rays in the partial reflection mirrors 61 and 62 is an acute angle, and the arrangement angles α ₂₁ and α ₂₂ of the partial reflection mirrors 61 and 62 are the arrangement of the introduction mirror B as described above. Same as angle α ₂ .

The partial reflection mirrors 61 and 62 in this posture reflect the light beam immediately after being reflected by the surface A ′, while transmitting the light beam immediately after being reflected by the surface A.
Therefore, the partial reflection mirrors 61 and 62 are given an angle-dependent reflectance characteristic. If there is angle dependency, it is possible to reflect one of two kinds of light beams having different angles with a predetermined reflectance and transmit the other with a transmittance of approximately 100%. The same reflecting film as that of the visible beam splitter can be applied to the reflecting surface having such an angle dependency. For the film formation, a known film formation method such as a vacuum evaporation method can be applied.

  In the above eyeglass display, when the distance D represented by the equation (29) is larger than 2 mm, if any one of the conditional equations (1), (3), (4) is satisfied, a double image The deviation is definitely not noticeable. On the other hand, when the distance D represented by the equation (29) is smaller than 2 mm, the deviation of the double image is surely conspicuous if any of the conditional equations (5), (6), and (7) is satisfied. Become.

Among these, when the conditional expression (1) or the conditional expression (5) is satisfied, the shift of the double image is suppressed to less than one pixel. Further, when the conditional expression (3) or the conditional expression (6) is satisfied, the shift of the double image is suppressed to less than 0.5 pixels. Further, when the conditional expression (4) or the conditional expression (7) is satisfied, the shift of the double image is suppressed to less than 0.2 pixels.
By these conditional expressions, this eyeglass display can moderately suppress the generation of double images while ensuring a wide viewing angle and a wide exit pupil.

In this eyeglass display, a transmissive LCD is used as the image display element 2. However, other types of image display elements such as a reflective LCD and a self-luminous element may be used.
In addition, the collimator lens 4 is used in this eyeglass display, but instead of the collimator lens 4, one or a plurality of optical surfaces having functions equivalent to those of the collimator lens 4 are introduced from the image display element 2 to the mirror B. You may provide in any location of the optical path of the display light beam until.

Further, in FIG. 3, the outline of the substrate 1 is arranged in the same manner as the spectacle lens, but may have other shapes as long as the optical path of the display light beam is secured.
3 and 4, the image display element 2 is disposed in the vicinity of the substrate 1. However, the image display element 2 is guided to the vicinity of the substrate 1 by a relay optical system at an appropriate position away from the substrate 1. Also good. Further, an aerial image may be formed at the same position using a scanning optical system.

3 and 4, the arrangement place of the image introduction unit U is on the observer side of the substrate 1, but it may be on the outside of the substrate 1. In that case, the direction of inclination of the introduction mirror B is reversed.
3 and 4, the arrangement place of the image introduction unit U is in the vicinity of the observer's temporal region. However, for example, the eyebrow of the observation eye E can be used as long as it does not interfere with the observer's field of view. It may be in the vicinity (upper front of the frame F).

(First example of the first embodiment)
Next, a first embodiment will be described.
In this example, each parameter was set as follows.
-Reflectivity / transmittance of the partial reflection mirror 61: 30% / 70%,
-Reflectivity / transmittance of the partial reflection mirror 62: 50% / 50%,
The refractive index n of the substrate 1 is 1.5168,
・ Thickness T of substrate 1: 4.5 mm,
-Arrangement angle α ₂ of introduction mirror B: 65 °,
・ Design value α _2i of the arrangement angle of the partial reflection mirror: 65 °,
-Internal reflection angle α _{T in} substrate 1: 50 °
In this embodiment, assuming that the amount of light incident on the partial reflection mirror 61 is 100%, 30% of the light is emitted to the observer side, and the remaining 70% is transmitted to the partial reflection mirror 62. Further, assuming that the amount of light incident on the partial reflection mirror 62 is 70%, 50% (that is, 70% × 50% = 35%) is emitted toward the viewer.

Further, in this embodiment, when each parameter is applied to the equation (29), it can be seen that the distance D = 3.4 mm. This distance D = 3.4 mm is larger than the diameter (up to 2 mm) of the pupil of the observation eye E.
Therefore, the conditional expression to be satisfied by the present embodiment may be any one of conditional expressions (1), (3), and (4).

In this embodiment, since the total number of partial reflection mirrors is “2”, there is no need to consider it. However, when each parameter is applied to the equation (2) as a trial, the partial reflection mirrors that should satisfy the conditional equation at the same time are considered. It can be seen that the number of sheets N = 2.
Next, the manufacturing method of the board | substrate 1 of a present Example is demonstrated.
In this manufacturing method, as shown in FIG. 5, a quadrangular prism part 11 is manufactured. The component 11 is a portion of the substrate 1 sandwiched between the partial reflection mirrors 61 and 62, and the surfaces 61 ′ and 62 ′ of the component 11 are surfaces to be the partial reflection mirrors 61 and 62.

FIG. 6 is a flowchart showing the procedure of the manufacturing method.
Step S11: The surfaces 71 and 72 of the part 11 are polished by a double-side polishing machine.
Step S12: The surfaces 61 ′ and 62 ′ of the part 11 are polished by a double-side polishing machine.
Step S13: The surfaces 81 and 82 of the part 11 are polished by a double-side polishing machine.
Step S14: A reflective film having an angle dependency is deposited on the surfaces 61 ′ and 62 ′ of the component 11 (partial reflection mirrors 61 and 62).

Step S15: A necessary surface of each part other than the part 11 is polished.
Step S16: A reflective film is deposited on a necessary surface of each component other than the component 11 (a surface to be the introduction mirror B).
Step S17: The part 11 and each other part are joined with an adhesive. The adhesive has the same refractive index as each component.

Step S18: An antireflection film is vapor-deposited on the surface to be the surface A on the outside and the surface A ′ on the viewer side of the joined parts. Before the vapor deposition, those surfaces are polished if necessary.
As described above, in this manufacturing method, the surfaces 61 ′ and 62 ′ of the component 11 are polished by the double-side polishing machine. Since the parallelism accuracy of the double-side polishing machine is very high, the declination of the surfaces 61 ′ and 62 ′ is suppressed to about 20 seconds in the prototype of this example.

When the declination angles of these surfaces 61 ′ and 62 ′ are ε, the angle difference δα between the partial reflection mirrors 61 and 62 formed thereon is δα = ε / (n−1). In this embodiment, since the refractive index n = 1.5168, the angle difference δα between the partial reflection mirrors 61 and 62 is δα = 39 seconds = 0.64 minutes. At this time, the shift amount of the double image (δα * n) = 0.98.
Therefore, according to this manufacturing method, the conditional expression (1) is satisfied, and the shift amount of the double image is suppressed to less than one pixel, specifically 0.98 pixels.

(Second example of the first embodiment)
Next, a second embodiment will be described.
In this example, each parameter was set as follows. The difference from the first embodiment is the reflectance of the partial reflection mirrors 61 and 62 and the thickness of the substrate 1.
-Reflectivity / transmittance of the partial reflection mirror 61: 30% / 70%,
-Reflectivity / transmittance of the partial reflection mirror 62: 30% / 70%,
-Refractive index n of substrate 1: 1.5168
・ Thickness T of substrate 1: 2.5 mm
-Arrangement angle α ₂ of introduction mirror B: 65 °,
・ Design value α _2i of the arrangement angle of the partial reflection mirror: 65 °,
-Internal reflection angle α _{T in} substrate 1: 50 °
In this embodiment, assuming that the amount of light incident on the partial reflection mirror 61 is 100%, 30% of the light is emitted to the observer side, and the remaining 70% is transmitted to the partial reflection mirror 62. Further, assuming that the amount of light incident on the partial reflection mirror 62 is 70%, 30% (that is, 70% × 70% = 21%) is emitted to the observer side.

Further, in this example, when each parameter is applied to the equation (29), it can be seen that the distance D = 1.5 mm. This distance D = 1.5 mm is smaller than the diameter (up to 2 mm) of the pupil of the observation eye E.
Therefore, the conditional expression to be satisfied by the present embodiment is any one of conditional expressions (5), (6), and (7).

In this embodiment, since the total number of partial reflection mirrors is “2”, it is needless to consider. However, when each parameter is applied to the expression (2) as a trial, the number N of partial reflection mirrors that should satisfy the conditional expression at the same time. It can be seen that = 2.
Next, the manufacturing method of the board | substrate 1 of a present Example is demonstrated. In this manufacturing method as well, as in the manufacturing method of the first embodiment, a rectangular column part 11 as shown in FIG. 5 is manufactured.

FIG. 7 is a flowchart showing the procedure of the manufacturing method.
As shown in FIG. 7, in the manufacturing method of the first embodiment (see FIG. 6), this manufacturing method is a finish polishing step (step S17) between the joining step (step S17) and the antireflection film deposition step (step S18). Step S21) is inserted. In this final polishing step (step S21), the surfaces to be the surfaces A and A ′ of the substrate 1 are polished by a double-side polishing machine.

In the present manufacturing method, since the finish polishing step (step S21) is added, an extra thickness is secured in advance for each polishing allowance in the finish polishing step (step S21), or the partial reflection mirror 61, It is necessary to secure an extra amount of duplication 62 (the amount of duplication seen from the observer side) in advance.
As described above, in this manufacturing method, the surfaces A and A ′ are polished on both sides with a double-side polishing machine, and then the antireflection film is deposited. Since the parallelism accuracy of the double-side polishing machine is very high, in the prototype of this example, the deflection angles of the surfaces A and A ′ were suppressed to about 5 seconds. Further, the deflection angles of the surfaces 61 ′ and 62 ′ were also suppressed to about 5 seconds.

At this time, the angle difference δα between the partial reflection mirrors 61 and 62 is 9.7 seconds = 0.16 minutes, and the angle difference between the surfaces A and A ′ is δθ = 0.16 minutes. Therefore, the double image shift amount (δα + δθ) * n = 0.49.
Therefore, according to this manufacturing method, the conditional expression (6) is satisfied, and the shift amount of the double image is suppressed to less than 0.5 pixels, specifically, to 0.49 pixels.

Note that the manufacturing method of this embodiment can also be applied to the manufacture of the substrate 1 of the first embodiment. In the manufacturing method of the first embodiment, when joining each component, there is a possibility that a step or an inclination is generated on the surfaces A and A ′ of the substrate 1 depending on the accuracy of each component, which may cause a double image. This is because is not zero.
[Second Embodiment]
A second embodiment of the present invention will be described with reference to FIGS. This embodiment is also an embodiment of an eyeglass display. Here, only differences from the eyeglass display of the first embodiment will be described.

  FIG. 8 is a schematic cross-sectional view of the optical system portion of the present eyeglass display. As shown in FIG. 8, the main difference is in the posture and the total number of partial reflection mirrors 91, 92,. The posture is such that the display light beam immediately after being reflected by the surface A on the outside world is reflected toward the surface A ′ on the viewer side. At this time, the sum of the incident angle and the reflection angle of the light beams in the partial reflection mirrors 91, 92,... Becomes “obtuse angle”, so that the reflectance required for the partial reflection mirrors 91, 92,. The angle characteristic approaches that of Fresnel reflection. Therefore, there is an advantage that the film configuration of the reflection film of the partial reflection mirrors 91, 92,.

Further, since the sum angle of the incident angle and the reflection angle of the light beams in the partial reflection mirrors 91, 92,... Is “obtuse angle”, the design value α _2i of the arrangement angle of the partial reflection mirrors 91, 92 _,. The additional angle of the arrangement angle α ₂ of the introduction mirror B, that is, α _2i = 90 ° −α ₂ .
Further, when the partial reflection mirrors 91, 92,... In this posture are viewed from the observer, they are smaller than those in the first embodiment, so the minimum required number K of partial reflection mirrors is necessary for the first embodiment. More than the minimum number.

The necessary minimum number K is the minimum number of partial reflection mirrors necessary for reliably guiding the display light beam reflected by the introduction mirror B, and is given by the following equation (30).
K = INT [2 * (tan α ₂ ) ² ] (30)
From Equation (30), in the present eyeglass display, for example, when the arrangement angle α ₂ of the introduction mirror B is set to 65 °, the minimum required number K = 9 (in the first embodiment, the minimum required number) K = 2).

Therefore, the total number of partial reflection mirrors of the present eyeglass display is set to “9”.
In this eyeglass display, the sum of the incident angle and the reflection angle of the light beam of the display light beam in the partial reflection mirrors 91, 92,... Is “obtuse angle”. ) And a different formula.

(Derivation of interval D)
The formula for obtaining the distance D (when the sum of the incident angle and the reflection angle of the light beam of the display light beam in the partial reflection mirror is “obtuse angle”) will be described below.
In FIG. 9, light rays L2 ′ and L3 ′ are light rays having the same angle of view. The light beam L2 ′ is reflected by a partial reflection mirror after the number of internal reflections n, and the light beam L3 ′ is reflected by an adjacent partial reflection mirror after the internal reflection frequency n + 2.

A point O in FIG. 9 is an origin (0, 0), a horizontal direction in FIG. 9 is an X direction, and a vertical direction in FIG. 9 is a Y direction. Further, the number of partial reflection mirrors that a light ray passing through the point O and traveling toward the plane A ′ crosses is m (m = 2 in FIG. 9) (including the reflection mirror at the point O).
At this time, a straight line R1 representing the adjacent partial reflection mirror is represented by the following expression (21 ′).

y = x / tan α _2i + D ₂ * (m−1) / tan α _2i (21 ′)
Further, a straight line R2 representing the light beam that is the generation source of the light beam L3 ′ is represented by the following expression (22 ′).
y = x / tan α _T (22 ′)
The x coordinate Xp of the intersection P between the straight line R1 and the straight line R2 is represented by the following expression (23 ′).

Xp = D ₂ * (m−1) * tan α _T / (tan α _2i −tan α _T )] (23 ′)
Further, assuming that the generation source of the light ray L2 ′ is a point O, the following expression (24 ′) is established.
D = | Xp | (24 ′)
Further, equations (25) and (26) are established.

D ₂ = T * tan α _2i (25)
α _T = 2 * (90 ° −α ₂ ) (26)
Further, since the sum of the incident angle and the reflection angle of the light beam of the display light beam in the partial reflection mirrors 91, 92,... Is “obtuse angle”, the following expression (28 ′) is established.
α ₂ = 90 ° −α _2i (28 ′)
When the above formulas (23 ′), (24 ′), (25), (26), and (28 ′) are arranged, the interval D is expressed by the following formula (29 ′).

D = 2 (m−1) * T * tan α _2i / [(tan α _2i ) ² +1] (29 ′)
Further, when the number m of partial reflection mirrors (the number of light beams traversed) is estimated as m = N−1 with respect to the number N of partial reflection mirrors (the number that should satisfy the conditional expression), the following expression (29 ″) is obtained. It is done.
D = 2 (N−2) * T * tan α _2i / [(tan α _2i ) ² +1] (29 ″)
(Example of the second embodiment)
Next, examples will be described.

In this example, each parameter was set as follows.
The refractive index n of the substrate 1 is 1.5168,
・ Thickness T of substrate 1: 3 mm,
-Arrangement angle α ₂ of introduction mirror B: 65 °
・ Design value α _2i of the arrangement angle of the partial reflection mirror: 25 °,
-Internal reflection angle α _{T in} substrate 1: 50 °,
Further, the reflection characteristics set for the partial reflection mirrors 91, 92,... Are as shown in FIG. In FIG. 10, “display light intensity” indicates reflectance, and “external light intensity” indicates transmittance.

In this embodiment, when each parameter is applied to the equation (29 ″), it can be seen that the distance D = 2.3 mm. This distance D = 2.3 mm is 2 mm (that is, the diameter of the pupil of the observation eye E). Larger than).
Therefore, the conditional expression to be satisfied by the present embodiment may be any one of conditional expressions (2), (3), and (4).

Further, in this embodiment, when each parameter is applied to the expression (2), it can be seen that the number N of partial reflection mirrors that should satisfy the conditional expression is N = 3.
Next, the manufacturing method of the board | substrate 1 of a present Example is demonstrated.
In the present manufacturing method, since the total number of the partial reflection mirrors is 9, as shown in FIG. 11, eight square pole parts 21-1, 21-2, 21-3,..., 21-8 are manufactured. To do. Except for the large number of parts, this is the same as the manufacturing method (FIG. 6) of the first example of the first embodiment.

  That is, the joint surfaces of the eight parts 21-1, 21-2,..., 21-8 should be polished by a double-side polishing machine to form the partial reflection mirrors 91, 92,. A reflective film is deposited on the nine joint surfaces. The vapor deposition surface is formed by joining each of the four parts 21-1, 21-3, 21-5, 21-7, which are arranged every other part, 91 ', 92', 93 ', 94', 95 ', 96 ', 97', 98 'and one joining surface 99' of the part 21-8.

After that, the parts 21-1, 21-2,..., 21-8 and other parts prepared in advance are joined with a predetermined adhesive. Further, among the parts after joining, the substrate 1 is completed by polishing each of the surfaces to be the outside surface A and the viewer side surface A ′ as necessary, and depositing an antireflection film thereon. To do.
Since the parallelism accuracy of the double-side polishing machine described above is very high, in the prototype of this embodiment, the arrangement angles α ₂₁ , α ₂₂ ,... Α ₂₉ (partial reflection mirrors 91, 92,. The measured value (unit: [°]) was as shown in FIG.

In this embodiment, since N = 3, the full width δα of the angle difference is calculated for each of the three consecutive partial reflection mirrors. FIG. 13 shows the calculated full width of the angle difference δα and the normal double image shift amount (δα * n). This deviation amount (δα * n) is obtained by converting the unit of the full width δα of the angle difference into minutes and then multiplying by the refractive index n.
As is apparent from FIG. 13, the double image shift amount (δα * n) is δα * n <0.2, which satisfies the conditional expression (4). Therefore, according to the present embodiment, the shift amount of the double image is suppressed to less than 0.2 pixels.

(Other)
In this example, the same manufacturing method (FIG. 6) as the first example of the first embodiment was applied, but the same manufacturing method (FIG. 7) as the second example of the first embodiment was used. May be applied.
Further, in this example, the deposition surface of the reflective film is the joint surface of every other component 21-1, 21-3, 21-5, 21-7, but as shown in FIG. It is good also as one joining surface of each of the components 21-1, 21-2, 21-3, 21-4, 21-5, 21-6, 21-7 to perform. Reference numerals 91 ′, 92 ′,..., 99 ′ in FIG.

  In that case, each of the components 21-1, 21-2, 21-3, 21-4, 21-5, 21-6, 21-7, 21-8 is an angle between the joint surface and the surface 102 adjacent thereto. Are manufactured with high precision so that When the components 21-1, 21-2, 21-3, 21-4, 21-5, 21-6, 21-7, 21-8 are joined after the reflective film is deposited, the respective surfaces are joined. If 102 is pressed against the common reference Sb, they can be aligned so that the parallelism of each joint surface becomes high.

[Others]
In each of the above embodiments, an eyeglass display capable of simultaneously observing the outside world and a virtual image has been described. However, the present invention can also be applied to a head mounted display that blocks the outside world.
The present invention can also be applied to a non-wearing type image display device. The non-wearable image display device is, for example, a large screen display provided with a number of partial reflection mirrors.

  The image display optical system of the present invention can also be used as an illumination optical system. In this illumination optical system, a light source is arranged instead of the image display element 2 and the exit pupil (symbol EP in FIG. 4) of the image display optical system is used as an illumination area. According to this image display optical system, each position of the illumination area can be illuminated with a light beam having a predetermined spread.

It is a figure explaining the principle of this invention. It is a figure explaining each parameter. It is an external view of the eyeglass display of 1st Embodiment. It is a schematic sectional drawing of the optical system part of the eyeglass display of 1st Embodiment. It is a figure explaining the manufacturing method of the 1st example of a 1st embodiment. It is a flowchart which shows the procedure of the manufacturing method of 1st Example of 1st Embodiment. It is a flowchart which shows the procedure of the manufacturing method of 2nd Example of 1st Embodiment. It is a schematic sectional drawing of the optical system part of the eyeglass display of 2nd Embodiment. It is a figure explaining each parameter of a 2nd embodiment. It is a figure which shows the reflective characteristic of the partial reflection mirror of the Example of 2nd Embodiment. It is a figure explaining the manufacturing method of the Example of 2nd Embodiment. It is a figure which shows the precision of the Example of 2nd Embodiment. It is a figure which shows the deviation | shift amount of the double image of the Example of 2nd Embodiment. It is a figure explaining the modification of the manufacturing method of the Example of 2nd Embodiment.

Explanation of symbols

1: substrate, 2: image display element, 3: illumination optical system, 4: collimator lens, B: introduction mirror, 61, 62, 91, 92, ...: partial reflection mirror, E: observation eye

Claims (9)

A substrate for introducing a light beam from the image display element to form an optical path therein;
In an image display optical system comprising a plurality of parallel partial reflection surfaces inserted in the optical path,
The image display optical system characterized in that the total width δα of the angle difference between the two or more continuous partial reflection surfaces satisfies the following expression (1).
δα * n <1 (1)
Where “n” is the refractive index of the substrate and “δα” is in minutes. The image display optical system according to claim 1,
An image display optical system characterized in that the total width δα of the angle difference between the N or more continuous reflecting surfaces represented by the following formula (2) satisfies the above formula (1).
N = INT [2 / (T * tanα _2i )] + 2 (2)
However, “T” is the thickness of the substrate, “α _2i ” is the design value of the angle formed by the partial reflection surface and the normal of the substrate, and the function INT [A] of A is an integer part of A. In the image display optical system according to claim 1 or 2,
The image display optical system characterized in that the full width δα of the angle difference satisfies the following expression (3).
δα * n <0.5 (3) In the image display optical system according to any one of claims 1 to 3,
The image display optical system characterized in that the full width δα of the angle difference satisfies the following expression (4).
δα * n <0.2 (4) The image display optical system according to claim 1,
The substrate propagates while internally reflecting the light beam,
The image display optical system characterized in that the total width δα of the angle difference and the angle difference δθ of the substrate surface used for the internal reflection satisfy the following expression (5).
(Δα + δθ) * n <1 (5)
However, the unit of “δθ” is minutes. In the image display optical system according to claim 5,
The image display optical system characterized in that the total width δα of the angle difference and the angle difference δθ of the substrate surface used for the internal reflection satisfy the following expression (6).
(Δα + δθ) * n <0.5 (6) In the image display optical system according to claim 5 or 6,
The image display optical system characterized in that the total width δα of the angle difference and the angle difference δθ of the substrate surface used for the internal reflection satisfy the following expression (7).
(Δα + δθ) * n <0.2 (7) An image display element;
A collimator for converting the light beam from the image display element into a parallel light beam;
An image display device comprising: the image display optical system according to claim 1 that guides the light flux. The image display device according to claim 8,
An image display apparatus, further comprising: a mounting unit that mounts the image display element, the collimator, and the image display optical system on a viewer's head in a predetermined positional relationship.

Images