JPH07333410A - Optical element of visual observation device of observation object - Google Patents

Abstract

PURPOSE:To obtain an erecting image without generating such trouble as flicker or distortion of the image with an optical element to be used for a device for visually observing an observation object as the image. CONSTITUTION:The respective prism parts P1 of a Fresnel prism P are composed of a face 1 on which light is made incident from outside, a face 2 from which the light is emitted outside the prism parts P1 after incidence via the incident face 1 and advance 10 the prism parts P1, a reincident face 3 on which the light from the exit face 2 is made incident into the same prism parts P1 and a final exit face 4 from which the light advancing in the prism parts P1 is finally emitted toward a direction of observing the observation object. The light emitted from the observation object advances to the respective prism parts P1 in row of A, B, C and maintains the row of A', B', C' even after emission from the respective prism parts P1. The image over the entire part erects. For example, the light of A passes a1 a2 before the incidence and has the same direction as a'1 a'2 after the emission from the prism parts P1 when the light advancing to the individual prism parts P1 is independently viewed. The image of the observation object viewed through the Fresnel prism P erects perfectly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical element used in a device for visually recognizing an observation object as an image, such as a blind spot observing device provided in a window of a vehicle.

[0002]

2. Description of the Related Art Conventionally, as an optical element used in a blind spot visual recognition device provided in a window portion of a vehicle, for example, as shown in FIG. There is a Fresnel prism 22 having irregularities in shape. This Fresnel prism 2
2 is disposed on the window glass 23 of the vehicle so that the uneven portion is located inside the vehicle compartment, that is, on the surface on the side where the Fresnel prism 22 emits light.

However, in a blind spot recognizing device to which such a Fresnel prism 22 is applied as an optical element, for example, as shown in FIG. Angle θ formed by the light from the part to be visually recognized with the vertical line a of the rear window 25
20 is big. As shown in FIG. 10, the incident angle θ21 when the light from the portion to be visually recognized is incident on the Fresnel prism 22 is equal to the angle θ20 and is large, and most of the light is reflected by the glass surface of the rear window 25 and visually The light hardly penetrates in the direction of the person's eye point, and although the optical path physically exists, as a result, there is a problem that it cannot be visually recognized.

Therefore, as shown in FIG. 12, the Fresnel prism 22 is placed outside the passenger compartment, that is, the Fresnel prism 22.
If it is arranged on the window glass 23 of the vehicle so that the concave-convex portion is located on the incident side of, the incident angle of light becomes small as θ22, and the amount of light entering the Fresnel prism 22 can be increased. Therefore, conventionally, a technique has been proposed in which light is captured by such a method to visually recognize an image. For example, Japanese Patent Laid-Open Nos. 59-29964 and 63-110434 disclose prisms. A technique has been disclosed in which light is totally reflected by a total reflection surface provided inside and is emitted in a viewing direction (see FIG. 13).

[0005]

However, the conventional techniques for visually observing an object to be observed have the following problems. That is, in the technique in which the light is totally reflected by the total reflection surface provided inside the prism and is emitted in the viewing direction, as shown in FIG. 13, the light emitted from the observation object is A, B, The entire image is upright because the A ', B', and C'arrangements are maintained even after the prism portion 26 enters each prism portion 26 and exits the prism portion 26. When the light entering the prism portion 26 is viewed alone, for example, with respect to the light A in the figure,
← a2, but after exiting from the prism portion 26, it becomes a'2 → a'1 and is inverted. Therefore, when the images emitted from the individual prism portions 6 are viewed, an extremely unnatural image of being inverted is obtained.

For this reason, in the prior art, the intervals between the Fresnel prisms, that is, the pitch, is made finer so that each image is made smaller than the size that can be recognized by the resolution of the naked eye of the human body, so that it is pseudo. The above problem is solved by making it look like an erect image. JP-A-59-29964 and JP-A-63-
This is possible because the technique described in Japanese Patent Laid-Open No. 110434 is intended for a large screen such as a rear projection type screen of a video projection television that is visually recognized at a long distance.

On the other hand, in FIG. 13, the angle θ23 formed by the normal line b of the reference surface 32 of the prism portion 26 and the incident light ray a1.
Becomes larger, the projected image portion 30 becomes smaller, the image gap 31 formed by each prism portion 26 becomes larger, and continuous images cannot be obtained. JP 63-
Japanese Patent Laid-Open No. 110434 uses a technique in which a second screen is provided on the viewing side and an image is thereby corrected.

However, since the blind spot recognizing device for a vehicle is not a large screen and can be visually recognized from a long distance so as to make it look like an erected image in a pseudo manner, problems such as image flicker, distortion, etc. occur. However, the above-mentioned conventional techniques cannot be applied to a blind spot visual recognition device. Therefore,
In view of the above conventional problems, the present invention provides an upright image without causing problems such as image flicker and distortion in an optical element used in an apparatus for visually observing an observation object. The purpose is to

[0009]

Therefore, the invention according to claim 1 is an optical element used in a device for visually observing an observation object as an image, in which light from the observation object enters from the outside of the optical element. Optical surface, a surface through which light enters from outside the optical element and travels inside the optical element, and exits to the outside of the optical element; and a surface on which light emitted from the optical element enters the same optical element again. And a surface from which the light that has traveled through the inside is emitted in the direction of observing the object to be observed,
In the optical path in which the light from the observation object travels in the observation direction, there is no reflection surface between the entrance surface and the exit surface of the optical element.

According to a second aspect of the present invention, at least one of the light incident surfaces is formed into a curved concave surface shape, and at least one of the light emission surfaces is formed into a curved convex surface shape. In the invention according to claim 3, at least one of the surfaces from which the light is emitted is formed into a curved concave surface shape.

According to a fourth aspect of the present invention, the device for visually observing an observation object as an image is a blind spot recognizing device provided in a window portion of a vehicle, and the optical element has an uneven portion on its incident side. The Fresnel prism is arranged.

[0012]

In the invention described in claim 1, the light emitted from the object to be observed enters the optical element in the order of A, B, and C, for example, A ', B
Since the arrangement of'and C'is maintained, the whole image is upright. Further, when the light entering each optical element is viewed alone, it is in the same direction before and after the incidence.

Therefore, the image of the observation object viewed through the optical element is completely upright. In the invention according to claim 2, for example, by forming the re-incident surface by the curved concave surface and the final exit surface by the curved convex surface group, the image obtained by the optical element becomes large, and the interval between the individual images becomes large. It is smaller than that of the invention according to claim 1.

In the invention according to claim 3, for example, the incident surface is formed by a curved concave surface, the exit surface is formed by a curved concave surface, the re-incident surface is formed by a curved concave surface, and the final exit surface is formed by a curved convex surface group. By doing so, the image obtained by the optical element becomes large, and the interval between the individual images becomes smaller than that of the invention according to claim 2. Claim 4
In the described invention, defects such as image flicker and distortion do not occur, and the blind spot can be reliably recognized.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the accompanying drawings. 1 and 2 show the configuration of a first embodiment of the invention described in claim 1. The optical element shown in this embodiment is a Fresnel prism P constituted by connecting a plurality of prism portions P1. In this embodiment, the Fresnel prism P is used in a blind spot visual recognition device provided in a window portion of a vehicle. It was done like this. In this case, the Fresnel prism P is arranged on the window glass of the vehicle so that the uneven portion is located outside the passenger compartment, that is, on the incident side of the Fresnel prism P.

In the figure, each prism portion P1 of the Fresnel prism P has a surface 1 on which light is incident from the outside of the prism portion P1 and an inside of the prism portion P1 after light is incident from the outside of the prism portion P1 through the incident surface 1. The surface 2 emitted to the outside of the prism portion P1 and the surface from which the light emitted from the emission surface 2 emitted from the prism portion P1 again enters the same prism portion P1, that is, the re-incident surface 3 and the prism portion P1. The light exiting in the direction of observing the object to be observed is finally emitted, that is, the final emission surface 4.

In the present embodiment, the final exit surface 4 is
It is formed by the surface of the Fresnel prism 5 for correcting the optical path. The final exit surface 4 may be formed of a cylindrical Fresnel lens surface instead of the Fresnel prism 5. Each of the incident surface 1, the exit surface 2 and the re-incident surface 3 is a flat surface.

Next, the uprightness of the image in the blind spot visual recognition apparatus using the Fresnel prism P having such a structure will be described. The light emitted from the observation object enters each prism portion P1 in the arrangement of A, B, and C and maintains the arrangement of A ′, B ′, and C ′ even after exiting each prism portion P1. Therefore, it can be seen that the whole image is upright. Looking at the light entering the individual prism portions P1 alone, for example, for the light of A in the figure, a1 ← a2 before the incidence and a′1 ← a′2 after the emission from the prism portion P1. It is in the same direction as.

Therefore, the image of the observation object viewed through the Fresnel prism P is completely upright. Next, the geometrical relationship of the optical paths will be described with reference to FIG. In the figure, the light 6 from the desired direction is incident on the incident surface 1 with an inclination of θ9 at an incident angle θ.
It is incident at 1. At this time, the refraction angle θ2 of the light refracted at the incident surface 1 is expressed by the following equation.

[0020]

[Equation 1]

The angle θ3 at which this light enters the exit surface 2
Is expressed by the following equation.

[0022]

[Equation 2]

The refraction angle θ4 when the light 6 is emitted from the exit surface 2 to the outside of the prism portion P1 is expressed by the following equation.

[0024]

[Equation 3]

The incident angle θ5 when the light 6 is incident on the re-incident surface 3 is represented by the following equation.

[0026]

[Equation 4]

The refraction angle θ6 of the light 6 on the re-incident surface 3 is expressed by the following equation.

[0028]

[Equation 5]

The incident angle θ7 when the light 6 is incident on the final exit surface 4 is expressed by the following equation.

[0030]

[Equation 6]

The refraction angle θ8 when the light 6 is emitted from the final emission surface 4 to the outside of the prism portion P1 is expressed by the following equation.

[0032]

[Equation 7]

Since the image erectivity and the geometrical relationship of the optical paths in the above-described embodiments are valid in all the other embodiments described below, the description thereof will be omitted in the following embodiments. FIG. 3 shows a second embodiment of the invention according to claim 1. In this embodiment, except that the final exit surface 4 is not a Fresnel prism 5 as in the first embodiment of FIG. 1 but a flat surface 7 for easy mounting on the glass surface, It is similar to the embodiment of.

FIG. 4 shows a first embodiment of the invention according to claim 2. The optical element shown in this embodiment is a prism lens PR configured by connecting a plurality of prism lens portions PR1. In this embodiment, this prism lens PR is a blind spot provided in a window portion of a vehicle. It is intended for use in a visual recognition device. In this case, the prism / lens PR is arranged so that the concave / convex portion is located outside the passenger compartment, that is, on the incident side of the prism / lens PR.

In this embodiment, the entrance surface 1 and the exit surface 2 are flat surfaces, the re-incident surface 3 is a curved concave surface, and the final exit surface 4 is a curved convex surface group. By thus forming the re-incident surface 3 by the curved concave surface and the final exit surface 4 by the curved convex surface group, the image obtained by each prism / lens portion PR1 becomes large, and the interval 11 between the individual images is increased.
Is smaller than the interval 11 of the first embodiment of the invention described in claim 1.

FIG. 5 illustrates how to determine the curved surface shapes of the re-incident surface 3 and the final exit surface 4.
The two optical paths 6A and 6B incident in parallel from the outside of the lens portion PR1 are parallel until they enter the re-incident surface 3, but they expand when they enter the re-incident surface 3. In order that the expanded optical path becomes parallel again after exiting the final exit surface 4, the inclination θ11A of the tangent line 3A at the entrance point of the re-incident surface 3 of the optical path 6A and the entrance point of the re-incident surface 3 of the optical path 6B. Tangent 3B
Of the tangent line 4A at the exit point of the final exit surface 4 of the optical path 6A, and the slope θ12B of the tangent line 4B at the exit point of the final exit surface 4 of the optical path 6B. In this way, the inclination of the tangent line at the incidence point of the re-incident surface 3 and the inclination of the tangent line at the emission point of the final emission surface 4 are determined so that all the optical paths 6 emerging from the final emission surface 4 are parallel. Thus, the curved surface shapes of the re-incident surface 3 and the final exit surface 4 are determined.

FIG. 6 shows a second embodiment of the invention described in claim 2. In this embodiment, the entrance surface 1 is formed by a curved concave surface, the exit surface 2 is formed by a curved convex surface, the re-incident surface 3 is formed by a flat surface, and the final exit surface 4 is formed.
Is the surface of the Fresnel prism 5 for optical path correction as shown in the figure,
Alternatively, it is configured by the surface of a cylindrical Fresnel lens.

Also in this embodiment, the image obtained by each prism / lens portion PR1 becomes large, and
The distance 11 between the two images is smaller than the distance 11 in the first embodiment of the invention. Further, in this embodiment, the inclination of the tangent line at the incident point of the entrance surface 1 and the inclination of the tangent line at the exit point of the exit surface 2 are set so that all the optical paths 6 exiting the exit surface 2 are parallel. By determining, the curved surface shapes of the entrance surface 1 and the exit surface 2 are determined.

FIG. 7 shows a third embodiment of the invention according to claim 2. In this embodiment, the entrance surface 1 is formed by a curved concave surface, the exit surface 2 is formed by a curved convex surface, the re-incident surface 3 is formed by a flat surface, and the final exit surface 4 is formed.
Has a flat surface so that it can be easily attached to the glass surface. In such an embodiment, the image obtained by each prism lens PR1 becomes large, and the interval 11 between the individual images becomes smaller than the interval 11 in the second embodiment of the invention described in claim 1.

Further, in this embodiment, similarly to the second embodiment of the invention described in claim 2, the entrance surface 1 and the exit surface 2 are provided.
The curved surface shape of is determined. FIG. 8 shows a fourth embodiment of the invention according to claim 2. In this example,
The entrance surface 1 is a curved concave surface, the exit surface 2 is a flat surface, and the re-incident surface 3 is a curved concave surface.
The final exit surface 4 is composed of a group of curved convex surfaces.

In this embodiment, the image obtained by each prism / lens section PR1 becomes large and
The distance 11 between the two images is smaller than the distance 11 in the third embodiment of the invention. In addition, in this embodiment, in the same manner as the first embodiment of the invention described in claim 1,
The curved surface shapes of the re-incident surface 3 and the final exit surface 4 are determined.

FIG. 9 shows a first embodiment of the invention described in claim 3. In this embodiment, the entrance surface 1 is a curved concave surface, the exit surface 2 is a curved concave surface, the re-incident surface 3 is a curved concave surface, and the final exit surface 4 is a curved convex surface group. . In such an embodiment, the image obtained by each prism / lens portion PR1 becomes large, and the interval 11 between the individual images becomes smaller than the interval 11 in the fourth embodiment of the invention described in claim 2.

Also, in this embodiment, the final exit surface 4
The incident surface 1 so that all the optical paths 6 that emit light are parallel.
Of the tangent line at the incident point of, the tangent line at the exit point of the exit surface 2, the tangent line at the entrance point of the re-incident surface 3, and the tangent slope at the exit point of the final exit surface 4. Thus, the curved surface shapes of the entrance surface 1, exit surface 2, re-incident surface 3, and final exit surface 4 are determined.

[0044]

As described above, according to the first aspect of the invention, the image of the observation object viewed through the optical element is completely upright, and no problems such as image flicker and distortion occur. According to the invention described in claim 2, the image obtained by the optical element becomes large, and the interval between the images can be made small.

According to the third aspect of the invention, the image obtained by the optical element becomes large, and the interval between the images becomes smaller. In the invention according to the fourth aspect, defects such as image flicker and distortion do not occur, and the blind spot can be reliably recognized.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an optical element showing a first embodiment of the invention according to claim 1.

FIG. 2 is an explanatory view of an optical path of an optical element of the same example.

FIG. 3 is a configuration diagram of an optical element showing a second embodiment of the invention according to claim 1;

FIG. 4 is a configuration diagram of an optical element showing a first embodiment of the invention according to claim 2;

FIG. 5 is an explanatory diagram of an optical path of the optical element according to the above embodiment.

FIG. 6 is a configuration diagram of an optical element showing a second embodiment of the invention according to claim 2;

FIG. 7 is a configuration diagram of an optical element showing a third embodiment of the invention according to claim 2;

FIG. 8 is a configuration diagram of an optical element showing a fourth embodiment of the invention according to claim 2;

FIG. 9 is a configuration diagram of an optical element showing a first embodiment of the invention according to claim 3;

FIG. 10 is a view showing a conventional example of an optical element used in a blind spot visual recognition device installed in a window portion of a vehicle.

FIG. 11 is a diagram illustrating a problem of the blind spot visual recognition device of the above.

FIG. 12 is a diagram showing a conventional example of an optical element used in another blind spot visual recognition device.

FIG. 13 is a view showing a conventional example of an optical element used in another blind spot recognition device.

[Explanation of symbols]

 P1 prism part P Fresnel prism 1 incident surface 2 exit surface 3 re-incident surface 4 final exit surface PR1 prism lens part PR prism lens

Claims (4)

[Claims] 1. An optical element used in a device for visually observing an observation object as an image, comprising: a surface on which light from the observation object enters from the outside of the optical element; and an optical element after the light enters from the outside of the optical element. The surface that travels inside the optical element and is emitted to the outside of the optical element, the surface where the light emitted from the optical element enters the same optical element again, and the direction in which the light that has passed through the optical element observes the observation target. And a surface which is emitted to the observation object, and in which there is no reflection surface between the entrance surface and the exit surface of the optical element in the optical path in which the light from the observation object travels in the observation direction. An optical element in a device for visually observing an observation target. 2. The observation according to claim 1, wherein at least one of the light incident surfaces is formed into a curved concave surface shape, and at least one of the light emission surfaces is formed into a curved convex surface shape. An optical element in a device for visually recognizing an object. 3. The optical element in the apparatus for visually observing an observation object according to claim 1, wherein at least one of the surfaces from which the light is emitted is formed in a curved concave surface shape. 4. A device for visually observing an observation object as an image is a blind spot recognizing device provided in a window portion of a vehicle, and an optical element is a Fresnel prism arranged such that an uneven portion is located on the incident side thereof. The optical element in the apparatus for visually observing an observation object according to claim 1, wherein