JPH077125B2 - Three color separation optical device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup apparatus such as a television camera using three solid-state image pickup elements or image pickup tubes, and is installed directly at the rear of an objective lens system without a relay lens. The present invention relates to the three-color separation optical device.

2. Description of the Related Art Three-color separation optical systems used in color television cameras and the like are roughly classified into so-called relay lens type and prism type. Among them, as the prism type, a so-called Phillips type as shown in Japanese Patent Publication No. 38-23724 is often used.

FIG. 2 is a sectional view showing the structure of a conventional three-color separation optical system using a Phillips prism.

In FIG. 2, 1 is a first prism, 2 is a second prism, 3 is a third prism, 4 is an objective lens, 5 is a blue reflection dichroic mirror, 6 is a red reflection dichroic mirror, 7 is a blue trimming filter, and 8 is red. A trimming filter, 9 is a green trimming filter, 10 is an air gap, and 14, 15 and 16 are solid-state image sensors.

The operation of the three-color separation optical system configured as shown in FIG. 2 will be described below.

The incident light I that is incident perpendicularly on the incident surface of the first prism 1 from the objective lens 4 is reflected only on the blue light B by the blue reflection dichroic mirror 5. The reflected blue light B is totally reflected again at the boundary surface between the glass surface of the first prism 1 and the air, passes through the blue trimming filter 7, and then is emitted vertically to the solid-state imaging device 14. The transmitted light that has passed through the blue reflection dichroic mirror 5 is incident on the second prism 2, and only the red light R is reflected by the red reflection dichroic mirror 6. This reflected light is totally reflected by the boundary surface between the glass surface of the second prism 2 and the air gap 10, passes through the red trimming filter 8, and then is emitted vertically to the solid-state image sensor 15. The transmitted light that has passed through the red reflection dichroic mirror 5, that is, the green light G, passes through the third prism 3 as it is, passes through the green trimming filter 9, and then is vertically emitted to the solid-state image sensor 16.
Go to. Also, as the function of each trimming filter,
This is for finally controlling the wavelength range of the color light incident on the solid-state image sensor. In this way, blue, red, and green lights are obtained.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, in the above configuration, since a relatively thin oblique air layer is inserted in the optical path, dust is mixed into the air layer to split an image, and mechanical vibration causes the first prism and the second prism to be broken. There are problems such as color shading due to the deviation of parallelism of the image, double image generation, and assembly complexity. Therefore, in order to maintain stability, it is unavoidable that the price becomes expensive. there were.

In view of the above point, the present invention has an object to provide a three-color separation optical system in which an air layer is eliminated from the optical path and all obstacles caused by the air layer are removed.

Means for Solving the Problems In order to solve the above problems, the present invention is configured by laminating first, second and third prisms, and the first and second prisms and the second and third prisms are combined. Make sure that each prism
First and second dichroic mirrors are provided, the incident surface of the first prism is arranged so as to be perpendicular to the optical axis of the imaging lens, and the incident light is guided by the first dichroic mirror to the first dichroic mirror. The reflected light and the first transmitted light are decomposed, the first transmitted light is further decomposed into the second reflected light and the second transmitted light by the second dichroic mirror, and the second transmitted light is further decomposed. The third reflected light is reflected by the third prism to directly obtain the third reflected light, and the first, second, and third reflected lights are directly reflected on the emission surfaces of the first, second, and third prisms, respectively. It is a three-color separation optical system that emits light vertically.

Operation In the present invention, as shown in the above-mentioned configuration, since the first prism and the second prism and the second prism and the third prism are bonded together, image deterioration due to dust does not occur, and the bonding is prevented. The reflection and transmission of the dichroic mirror on the mating surface is performed uniformly both in the central portion and the peripheral portion, and stable three-color separation can be performed without causing color shading. Further, since the respective color lights are obtained by reflection once, they do not become mirror images of each other. For example, when solid-state image pickup devices are used as the image pickup device, the same type of solid-state image pickup device for each color light can be used.

Embodiment 1 FIG. 1 is a sectional view showing the structure of a three-color separation optical system according to an embodiment of the present invention.

In FIG. 1, 1 to 9 are the same as those shown in FIG. 2 of the conventional example, but the solid-state image pickup devices 10, 11 and 12 are different from the conventional solid-state image pickup device in the horizontal charge transfer direction. The opposite is true.

As shown in the figure, the first and second prisms 2 are line segments ab
In the surface shown in, the second prism 3 and the third prism 3 are line segments bc
In the surface shown in, the first and third prisms 1 and 3 are line segments bd
The surfaces shown in Fig. 2 are respectively laminated and closely joined. Further, a blue reflecting dichroic mirror 5 is provided on the bonding surface of the first prism 1 and the second prism 2, and a red reflecting dichroic mirror 6 is provided on the bonding surface of the second prism 2 and the third prism 3. In this embodiment, the objective lens 4
Is perpendicular to the incident surface of the first prism 1, and the angle between the normal of each dichroic mirror and the reflecting surface of the third prism 3 and the optical axis is 30 °.

The operation of the three-color separation optical system of the present embodiment configured as described above will be described below.

The light information I obtained via the objective lens 4 is incident vertically from the incident surface of the first prism 1, and only the blue light B is reflected by the blue reflection dichroic mirror 5 in the dotted line direction.
The reflected blue light B proceeds straight as it is and the first prism 1
The light is emitted perpendicularly from the emission surface of, goes through the blue trimming filter 7, and then goes to the solid-state imaging device 10. The light transmitted through the blue reflection dichroic mirror 5 enters the second prism 2,
Only the red light R is reflected by the red reflection dichroic mirror 6 in the direction of the alternate long and short dash line. The reflected red light goes straight as it is and is emitted vertically from the emission surface of the second prism 2, passes through the red trimming filter 8, and then goes to the solid-state imaging device 11. The light transmitted through the red reflection dichroic mirror 6, that is, the green light G, is incident on the third prism 3, is totally reflected by the boundary surface between the glass surface and the air, and is emitted perpendicularly from the emission surface of the third prism 3 to produce the green light. After passing through the trimming filter 9, it goes to the solid-state imaging device 12.

As described above, according to the present embodiment, the blue reflective dichroic mirror 5 and the red reflective dichroic mirror 6 are attached to the bonding surface of the first prism 1 and the second prism 2, respectively.
The blue dichroic mirror 5 is provided on the bonding surface of the prism 2 and the third prism 3 so that the reflected blue light and the red light are directly emitted from the emission surface of each prism without being reflected by the other surface. The green light transmitted through the red dichroic mirror 6 is totally reflected on the boundary surface between the glass and the air of the third prism 3 and is emitted from the exit surface of the prism, so that the air layer is conventionally formed on the prism and the prism. A stable three-color separation optical system can be provided by solving the problems caused by the air layer of the three-color separation optical system that had been waiting for the joining, such as image deterioration due to dust, color shading, and double image. It is possible and each color light is 1
Since it is obtained by being reflected once, there is an advantage that no boundary image relationship caused by a different number of reflections occurs, and therefore all three solid-state imaging devices of the same type can be used. The angle formed by the optical axis of the objective lens 4, the normal line of each dichroic mirror, and the reflecting surface of the third prism 3 may be selected to be an arbitrary angle that is less affected by polarized light, and the correspondence between each color light and the prism to be extracted. Needless to say, is optional.

EFFECTS OF THE INVENTION As described above, according to the present invention, the conventionally required air gap between prisms and prisms is eliminated, and image deterioration due to dust caused by the air layer, color shading, double images, etc. In addition to being able to solve the above problems, the same type of solid-state image pickup device can be used for detecting each color light, and its practical effect is great.

[Brief description of drawings]

FIG. 1 is a sectional view showing the structure of a three-color separating optical system according to an embodiment of the present invention, and FIG. 2 is a sectional view showing the structure of a conventional three-color separating optical system using a Phillips prism. 1 ... 1st prism, 2 ... 2nd prism, 3 ... 3rd
Prism, 4 ... Objective lens, 5 ... Blue reflective dichroic mirror, 6 ... Red reflective dichroic mirror,
7: Blue trimming filter, 8: Red trimming filter, 9: Green trimming filter, 10,
11, 12 …… Solid-state image sensor.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-50-159618 (JP, A) JP-A-51-92222 (JP, A) JP-A-51-81521 (JP, A) Actual development Sho-49- 92730 (JP, U)

Claims (1)

[Claims] 1. A first prism, a second prism, and a third prism, which are formed by bonding the first and second prisms, and the first and second prisms and the second and third prisms, respectively. The dichroic mirror is arranged so that the incident surface of the first prism is perpendicular to the optical axis of the imaging lens, and the incident light is converted into the first reflected light and the first reflected light by the first dichroic mirror. Of the transmitted light, the first transmitted light is further decomposed into second reflected light and second transmitted light by the second dichroic mirror, and the second transmitted light is further decomposed into the third prism. The first, second, and third reflected lights are directly reflected by the first, second, and third reflected lights, respectively.
A three-color separation optical device characterized in that the light is emitted perpendicularly to the respective exit surfaces of the second and third prisms.