JP2000338313A - Color resolving prism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent even the generation of flare newly caused by a groove which is formed in order to fulfill the role of preventing a collision among prisms and the generation of flare in a color resolving prism. SOLUTION: In this color resolving prism 1 which is integrally formed by sticking plural prisms and resolves incident light from an image pickup lens into three primary colors, the groove 2 for preventing the collision among prisms and cutting the flare is formed on one of the prisms T1, T2 and T3, where the angles of opening parts of the grooves are set to be in a range of 30 deg.-45 deg..

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for preventing occurrence of flare in a color separation prism used in a video camera.

[0002]

2. Description of the Related Art As shown in FIGS. 7 and 8, a conventional color separation prism (prism block) a for a video camera includes three prisms T1, T2 and T3 and green, blue and red lights. Three image sensors (for example, CCD
Etc.) composed of Ig, Ib and Ir, each prism
The prism and the image sensor are fixed to each other with a transparent adhesive.

A dichroic film having a characteristic of reflecting green light is deposited on a second surface S2, which is an adhesive surface between the prisms T1 and T2, and the prism T1
A dichroic film having a property of reflecting blue light is deposited on a third surface S3, which is an adhesive surface between T2 and T3.

Light b that has passed through an imaging lens (not shown)
Is incident on the first surface S1 of the prism block a, only the green light is reflected on the second surface S2, undergoes total reflection on the first surface S1, and reaches the image sensor Ig dedicated to green light. Further, the blue light and the red light pass through the second surface S2, and only the blue light is reflected by the third surface S3, but the red light is transmitted as it is and reaches the image pickup device dedicated to each color light. Note that there is no particular limitation on the order of the color separation described above, and there is a case where color separation is performed in an order other than the above.

In the prism block a, it is inevitable that a dimensional error or the like occurs in the prisms T1, T2 and T3 in the manufacturing stage. Is corrected by sliding on the second surface S2 and the third surface S3, which are the bonding surfaces, respectively. At this time,
A groove c may be provided in the prism T1 in order to prevent the slidable prism T3 from colliding with the prism T1 to make it impossible to correct the optical path difference.

Further, when the groove c is provided in the prism T1, the irregular light beam sometimes plays a role of preventing the occurrence of flare due to reaching the image pickup device Ig for green light.

However, the groove c serves to prevent the collision between the prisms and the occurrence of flare. However, the groove c sometimes causes flare.

That is, as shown in FIG. 8, the shape of the groove c is
The angle is about 70 degrees, and the angle of the slope F from the deepest portion D to the entrance V has an inclination of about 40 degrees with respect to the optical axis Z.

Therefore, in the prism block a,
When a strong light source such as the sun is located at a position slightly deviated from the image frame due to a variation in the position or depth of the groove c due to a manufacturing error of the prism T1, a part of the light beam is part of the deepest portion D or the slope F of the groove c. And flare sometimes occurred. In particular, since the light ray L reflected on the second surface and the inclined surface F are almost parallel, the light reflected on the inclined surface F easily reaches the image pickup device Ig, which causes flare. Similarly, since the entrance V of the groove c is close to the reflection / transmission position of the light ray L,
When the intense light source is located at an upper position outside the image frame, a part of the light beam may be irregularly reflected at the entrance V of the groove c to generate a flare.

As described above, the groove c provided on the prism block a to prevent the collision between the prisms and the occurrence of flare sometimes causes a new flare.

[0011]

SUMMARY OF THE INVENTION In view of the above problems, the present invention provides a new flare caused by a groove provided to prevent collision between prisms and occurrence of flare in a color separation prism. It is another object of the present invention to prevent the occurrence of the problem.

[0012]

In order to solve the above-mentioned problems, a color separation prism according to the present invention comprises a plurality of prisms bonded and integrated, and a color separation for separating incident light from an imaging lens into three primary colors of light. In the prism, one of the prisms is formed with a groove for collision between the prisms and flare cutting, and the opening of the groove is formed in an angle range of 30 to 45 degrees.

Therefore, it is possible to prevent the occurrence of flare due to the collision between prisms and irregular light rays, and also to prevent the occurrence of new flare caused by providing grooves to prevent such collisions. It becomes possible.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the color separation prism of the present invention will be described with reference to the accompanying drawings.

In the color separation prism of the present invention, a plurality of prisms are adhered and integrated, and the incident light from the imaging lens is converted into light of three colors.
In a color separation prism that separates into primary colors, one of the prisms is formed with a groove for collision between the prisms and flare cutting, and the opening of the groove is formed at an angle of 30 to 45 degrees.
It is a range of degrees.

That is, the color separation prism (prism block) 1 for a video camera, as shown in FIGS. 1 to 4, avoids the collision between the prisms, and prevents the occurrence of flare due to irregular light rays. The purpose is to prevent the occurrence of new flares.

That is, the prism block 1 is composed of three prisms T1, T2 and T3 and three image pickup devices (for example, CCDs) Ig, Ib and Ir dedicated to green, blue and red light. Each other, the prism, and the image sensor are fixed to each other with a transparent adhesive.

A dichroic film having a characteristic of reflecting green light is deposited on a second surface S2, which is an adhesive surface between the prisms T1 and T2, and the prism T1
A dichroic film having a property of reflecting blue light is deposited on a third surface S3, which is an adhesive surface between T2 and T3.

Lights U and L passing through an imaging lens (not shown) enter the first surface S1 of the prism block 1,
Only the green light is reflected on the second surface S2 and totally reflected on the first surface S1, and reaches the image sensor Ig dedicated to green light. Further, the blue light and the red light are transmitted through the second surface S2,
At 3, only the blue light is reflected, but the red light is transmitted as it is, and reaches the image sensor dedicated to each color light. Note that there is no particular limitation on the order of the color separation described above, and there is a case where color separation is performed in an order other than the above.

In the prism block 1, dimensional errors and the like are unavoidable in the manufacturing stages of the prisms T1, T2 and T3. Therefore, the optical path difference of each color light due to the manufacturing errors is determined by the prisms T2 and T3. Is corrected by sliding on the second surface S2 and the third surface S3, which are the bonding surfaces, respectively. At this time,
A groove 2 is provided in the prism T1 in order to prevent the slidable prism T3 from colliding with the prism T1 to make it impossible to correct the optical path difference.

If the purpose is only to prevent the occurrence of flare due to irregular light, the shape of the groove should be as shown in FIG.
Also, like the groove 2A of the prism block 1A shown in FIG. 6, it is desirable that the angle of the opening is approximately 10 degrees in parallel with the optical axis Z.

This is because the light ray L reflected on the second surface S2 and the slope F of the groove 2A have a certain angle, so that even if there is a light ray reflected on the slope F, this is the light for green light. This is because it becomes difficult to reach the imaging element Ig.

Since the entrance V of the groove 2A and the reflection / transmission position of the light beam L on the second surface S2 are far apart, the groove 2A
New flare is unlikely to occur due to the entrance V.

In other words, as in the case of the groove 2A, the sharper the angle of the opening is, the less likely it is to be affected by manufacturing errors in the position and depth of the groove, and the flare caused by the provision of the groove 2A. This is advantageous for prevention of occurrence.

However, in the shape of the groove 2A, as shown in FIG. 6, since the angle of the opening is small, it is difficult to avoid the collision between the prisms when the prism 2 is moved for correcting the optical path difference. It is. In order to avoid the collision between the prisms and at the same time to prevent the occurrence of flare caused by the groove 2A, it is necessary to make the angle and the position appropriate.

The prism block 1 shown in FIGS. 1 and 2
Is that the distance between the deepest part D of the groove 2 of the prism T1 and the optical axis Z is equal to the light ray (upper) U and light ray (lower) reflected by the second surface S2.
A groove 2 is formed at a position substantially equal to the distance from one of the intersections with L to the optical axis Z from CR. The light ray (upper) U is a light flux that forms an image at 60% of the image height above the image sensor, and the light ray (lower) L forms an image at 60% of the image height below the image sensor. Light flux.

As described above, by making the distance between the intersection point CR and the deepest portion D from the optical axis Z, that is, their heights substantially the same, the groove 2 can be set deeper. It is possible to prevent the occurrence of flare due to irregular light rays.

As shown in FIG. 2, the groove 2 has an opening angle of 45 degrees and a slope F from the deepest part D to the entrance part V.
Is 15 degrees with respect to the optical axis Z.

As described above, by suppressing the angle of the opening of the groove 2 to 45 degrees, for example, even if the groove 2 is deepened or misaligned due to variations in manufacturing, the deepest part can be obtained. D can have a relatively large margin with respect to the light rays U and L. Even if a strong light source is positioned slightly outside the image frame, the occurrence of flare due to irregular reflection at the deepest portion D is reduced.

When the angle of the groove 2 is 45 degrees or more, the influence of the variation at the time of manufacturing on the occurrence of flare increases.

Further, the slope F from the deepest portion D of the groove 2 to the entrance portion V is formed at an angle of 15 degrees with respect to the optical axis Z. Accordingly, the distance between the entrance portion V and the light beam L can be sufficiently secured, so that irregular reflection at the entrance portion V hardly occurs, and the light beam reflected on the slope F hardly reaches the image sensor Ig. As described above, it is desirable that the inclination of the entrance portion of the groove 2 (the angle of the slope F with respect to the optical axis Z) is small, and if the inclination exceeds 15 degrees, the flare caused by the reflection at the entrance portion V of the groove 2 and the slope F is increased. Is more likely to occur, and conversely, if the angle is less than 10 degrees, the prism T1
Collision with T3 is difficult to avoid.

FIGS. 3 and 4 show that the angle of the opening portion of the groove 2 is 30 degrees, and the entrance portion V (slope F) from the deepest portion D to the optical axis Z.
14 shows a prism block 1 of a modified example in which the prism block 1 has an angle of 10 degrees with respect to.

As described above, in the prism block 1, the groove 2 is formed so that the shape of the opening has an appropriate angle, so that the distance between the entrance portion V of the groove 2 and the light beams U and L is increased. This allows a margin and makes it difficult for the reflected light on the slope F to reach the image pickup device Ig.

Accordingly, it is possible to prevent the occurrence of flare due to the provision of the groove 2, and to collide the prisms when moving the prisms in order to correct the optical path difference due to the manufacturing error of each prism. Can also be prevented.

It should be noted that the specific shapes and structures of the respective parts shown in the above-described embodiments are merely examples for embodying the present invention, and the technical features of the present invention will be described below. The scope should not be construed as limiting.

[0036]

As described above, the color separation prism according to the present invention is a color separation prism in which a plurality of prisms are bonded and integrated to separate incident light from an imaging lens into three primary colors of light. In one of them, a groove for collision between prisms and flare cutting is formed, and an opening portion of the groove is set in an angle range of 30 to 45 degrees. Flare can be prevented from being generated, and new flare can be prevented from being generated by providing a groove to prevent the flare.

According to the second aspect of the present invention, since the angle of the surface from the deepest part of the groove to the entrance is in the range of 10 to 15 degrees with respect to the optical axis, collision between prisms and a The generation of flare due to regular light rays can be prevented, and the generation of new flare caused by providing a groove to prevent these can be more effectively prevented.

[Brief description of the drawings]

FIG. 1 shows an embodiment of the color separation prism of the present invention together with FIG. 2 to FIG. 4, and FIG. 1 is a view schematically showing the whole.

FIG. 2 is an enlarged view showing a main part of FIG. 1;

FIG. 3 is a diagram schematically showing an entire modified example.

FIG. 4 is an enlarged view showing a main part of FIG. 3;

5 is a diagram for explaining a problem in forming a groove of a prism block together with FIG. 6, and FIG. 5 is a diagram schematically showing the whole;

FIG. 6 is an enlarged view of a main part of FIG. 5;

7 shows an example of a conventional prism block together with FIG. 8, and FIG. 7 is a view schematically showing the whole.

FIG. 8 is a partially enlarged view of FIG. 7;

[Explanation of symbols]

1: color separation prism, 2: groove, T1: prism, T2 ...
Prism, T3 ... Prism, D ... Deepest part (of groove), V ...
Entrance (of the groove)

Claims (2)

[Claims] 1. A color separation prism for bonding and integrating a plurality of prisms and separating incident light from an imaging lens into three primary colors of light, wherein one of the prisms includes collision between the prisms and flare. A color separation prism, wherein a groove for cutting is formed, and an opening portion of the groove has an angle in a range of 30 to 45 degrees. 2. The color separation prism according to claim 1, wherein the angle of the surface from the deepest portion of the groove to the entrance portion with respect to the optical axis is in a range of 10 degrees to 15 degrees.