JPH01103389A - Color separation prism - Google Patents

Abstract

PURPOSE:To attain high resolution for a picture by using a tightening member so as to clip a projection formed to a prism in parallel with an air gap so as to bond the prism thereby suppressing the deviation of resistoration to a small value. CONSTITUTION:An incident light 24 from a lens system 16 is separated into three colors in a prism group 1 and made incident as radiated lights 26, 27 to image pickup elements 20, 21, 22. Then outputs of the elements are synthesized to obtain a color picture. When thermal fluctuation is exerted, the movement widening the air gap 5 in parallel or in wedge shape is suppressed by the tightening member 10 fixing the prisms 2, 3 vertically to the gap 5. Then a recessed part 10a of the tightening member 10 is engaged by projections 8, 9 provided in parallel with the gap 5 of the prisms 2, 3 and the prisms 2, 3 are fixed. As a result, it is possible to suppress the deviation between the light beam 27 transiting through the gap 5 and the optical axis of the reflected light to reduce resistoration and to attain high resolution of the picture.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a color separation method for a color video camera in which incident light is divided into a plurality of optical paths by a group of prisms, and each light emitted from the group of prisms is received by a plurality of image sensors. It is about prisms.

2. Description of the Related Art The structure of a conventional color field prism of this type will be described with reference to FIGS. 7 and 8. Figures 7 and 8
The figure shows an example in which a conventional color separation prism is implemented in an imaging device generally used in a color video camera. The color separation prism 101 includes three prisms 102, 103, 1
04, and spacers 10 are provided on both sides between the prisms 102 and 103 to form an air gap 105.
6 is inserted, and the prisms 103 and 104 are bonded with adhesive 107.
are joined with. Furthermore, filters for color separation are formed on the exit surfaces of each of the prisms 102 to 1o4. The color separation prism 101 configured in this manner is fixed onto a prism base plate 108 with an adhesive 109. This prism base plate 1o8 is fixed to a frame 110 of a color video camera. A lens system 112 is arranged on the entrance surface III side of the prism 108, and this lens system]
]2 is fixed to the frame 110K. prism 1
Each exit surface 113, 114.11 of 02°103.104
Image sensors 116, 117, and 118 are arranged on the 5 side, and each of the image sensors 116 to 118 is fixed to the prism exit surfaces 113 to 115 with an adhesive 119 or the like.

Next, the operation of the above conventional example will be explained.

The incident light 12] from the lens system]12 is transmitted through the prism 102.
The reflected light 122 enters from the entrance surface 111 of the prism 102 and is separated into two colors at the air gap 105. One reflected light 122 is reflected again at the entrance surface 111 of the prism 102 and enters the image sensor 116 from the exit surface 113. The other transmitted light 123 is color-separated again at the adhesive surface 124 of the prisms 108 and 104.
One reflected light 125 is reflected again at the air gap 105 and enters the image sensor 117 from the exit surface 114 of the prism 10B. The other transmitted light 126 passes through the prism 10
The light enters the image sensor 118 through the exit surface 115 of No. 4.

In this way, the incident light 121 is separated into three colors by the color separation prism 101, and enters the image sensors 116 to 118. A color image can be obtained by combining these output signals.

Problems to be Solved by the Invention However, in the configuration of the conventional color separation prism 101, when thermal fluctuation occurs therein, the initial solid line state shifts to the chain line state as shown in FIG. That is, since the prisms 102 to 104 are triangular prisms, they do not expand and contract uniformly during thermal fluctuations, and the air gap 10
In case 5, there is an air layer and the bond between the two prisms 102 and 103 is not a perfect surface bond, so it is easy to move due to thermal fluctuations.Also, the adhesive 107 that fixes the prisms 103 and 104 is more sensitive to heat than the prism material. Since the coefficient of expansion is significantly large and the shell is soft, it is easily deformed.Furthermore, although the prism 102104 is fixed by the prism base plate 108, there is usually a difference in the coefficient of thermal expansion between the two. Therefore, the positional relationship of the prisms 102 to 104 is displaced.

This causes a phenomenon in which the optical axis 121 moves, causing a misregistration between the three image sensors 116 to 118, and deteriorating the resolution of the image.

The present invention solves the problems of the prior art as described above, and provides a color separation prism that can suppress misregistration to a small level, and therefore can improve the resolution of images. The purpose is to

Means for Solving the Problems and Technical Means of the Present Invention for Solving the Above Problems is to have an air gap at least at the junction of a group of prisms that divide incident light into a plurality of optical paths and emit them. The prism is joined by a fastening material that spans the joint in a direction perpendicular to the joint.

action The effect of this technical means is as follows.

That is, when the parts constituting the color separation prism and the bonding material undergo thermal fluctuations, they thermally expand and contract, but at this time, the displacement of the bonding surfaces between the prisms can be kept constant by the fastening material.

Example Hereinafter, embodiments of the present invention will be described based on the accompanying drawings.

First, a first embodiment of the present invention will be described.

1 and 2 show a color separation prism according to a first embodiment of the present invention, with FIG. 1 being a perspective view and FIG. 2 being a plan view with protrusions and fasteners removed.

As shown in FIGS. 1 and 2, the color separation prism 1 has three
This is a prism group composed of prisms 2, 3.4. Spacers 6 are inserted into both sides of the prisms 2 and 3 to form an air gap (fine distance) 5 of approximately I Qum. Prisms 3 and 4 are bonded together with adhesive 7. Filters for color separation are formed on the entrance and exit surfaces of each of the prisms 2-4. The prisms 2 and 3 are fixed by a fastener 10 that spans the joint forming the air gap 5 in a direction perpendicular to the prisms 2 and 3. That is, the prisms 2 and 3 are provided with protrusions 8 and 9 parallel to the air gap 5, and the recesses 10a of the fastening material 10 are engaged with these protrusions 8 and 9, so that the protrusions 8 and 9 are sandwiched by the fastening material 10. Embedded,
Fastener 0 is fixed with adhesive 11 so as to straddle both prisms 2 and 3, thereby fixing prisms 2 and 3. Color separation prism 1 configured in this way
is fixed onto the prism base plate 12 with an adhesive 13.

This prism base plate 12 is fixed to a frame 14 of a color video camera. A lens system 16 is arranged on the entrance surface 15 side of the prism 2, and this lens system 16 is fixed to the frame 14. A pickup element 20, 21, 22 is bonded to each exit surface 17, 18, 19 of the prism 2, 3, 4 via a bonding agent 23.

Next, the operation of the above embodiment will be explained.

As is clear from FIG. 2, the incident light 24 from the lens system 16 is separated into three colors in the prism group 1 as in the conventional example, and is outputted to the image sensor 20, 21 as the output light 25, 26, 27.
．． 22. The image pickup devices 20, 21 .
By combining the outputs of 22, a color image can be obtained. Here, when thermal fluctuation is applied, the fastening material 10 fixing the prism 2°3 in a direction perpendicular to the air gap 5 prevents the air gap 5 from expanding in parallel or into a wedge shape. Movement can be suppressed. As a result, it is possible to suppress the misalignment of the optical axes of the light ray 27 that passes through the air gap 5 and the light 25 that is reflected there, thereby making it possible to reduce registration and obtain a high-resolution image.

Note that by selecting a material with a low coefficient of thermal expansion, such as invar, as the material for the fastening material 10, it becomes possible to further reliably suppress the increase in the distance between the air gaps 5.

Next, a second embodiment of the present invention will be described.

FIG. 3 is a side view of essential parts showing a second embodiment of the present invention.

In this embodiment, on both sides of the prisms 2 and 3,
Projections 8 and 9 are provided parallel to the air gap 5, and the recesses 10a of the fastening material 10 are engaged with the projections 8 and 9 of each set, and the projections 8 and 9 are inserted into the fastening material 10, and the fastening material Apply adhesive 11 so that 10 straddles both prisms 2゜3.
The prisms 2 and 3 are fixed by this, and the other structure is the same as that of the first embodiment.

Next, a third embodiment of the present invention will be described.

FIG. 4 is a partially cutaway side view of essential parts showing a third embodiment of the present invention.

In this embodiment, the prisms 2 and 3 are provided with protrusions 8 and 9 parallel to the air gap 5, and these protrusions 8 and 9
The concave portion 10a of the fastening material 10 is engaged with the fastening material 10, the protrusions 8 and 9 are inserted into the fastening material 10, and the fastening material 10 is engaged with both prisms 2.
, 3 is fixed with a screw 28, thereby fixing the prisms 2 and 3, and the other structure is the same as that of the first embodiment.

Next, a fourth embodiment of the present invention will be described.

FIG. 5 is a plan view of essential parts showing a fourth embodiment of the present invention.

In this embodiment flJ, the fasteners 10 in the first embodiment are arranged and fixed at multiple locations (two locations in the illustrated example), and the other configurations are the same as in the first embodiment. It is.

Next, a fifth embodiment of the present invention will be described.

FIG. 6 is a side view of essential parts showing a fifth embodiment of the present invention.

In this embodiment, the rod-shaped fastening material 10 is
．． 3 and fixed with a bonding agent 29, and the other structure is the same as that of the first embodiment.

In each of the above embodiments, the prisms 2 and 3, which are joined with the air gap 5 and are most likely to cause misalignment of the optical axis, are joined by the fastening material 10. They may be joined using the fastening material 10 in the same manner as in the embodiment.

Effects of the Invention As described above, according to the present invention, among a group of prisms that divide incident light into a plurality of optical paths and emit them, at least a prism having an air gap at a joint part is straddled in a direction perpendicular to the joint part. Since it is fixed using a fastening material, it is possible to significantly reduce displacement of the optical axis due to thermal fluctuations compared to conventional color separation prisms, and it is possible to suppress misregistration between each image sensor. , Therefore, it is possible to maintain high image resolution.

[Brief explanation of the drawing]

1 and 2 show a color separation prism according to a first embodiment of the present invention, FIG. 1 is a perspective view [blank], FIG. FIG. 4 is a side view of the main part showing the second embodiment of the invention, FIG. 4 is a partially cutaway side view of the main part showing the third embodiment of the invention, and FIG. 5 is the fourth embodiment of the invention.
6 is a side view of essential parts showing a fifth embodiment of the present invention, FIGS. 7 and 8 show a conventional color separation prism, and FIG. 8 is a perspective view, and FIG. 8 is a plan view. 1... Prism group, 2-4... Prism, 5...
Air gap, 6... Spacer, 8, 9... Protrusion, 10... Fastening material, 1... Lens system, 20-22
...Photograph element. Name of agent: Patent attorney Toshio Nakao and 1 other list
l Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8

Claims (4)

[Claims] (1) Among the group of prisms that divide incident light into a plurality of optical paths and emit them, at least the prism having an air gap at the joint is fixed by a fastening material that straddles the joint in a direction perpendicular to the joint. color separation prism. (2) A color separation prism according to claim 1, characterized in that the prism is joined to the prism by sandwiching protrusions formed on the prism in parallel with the joining surface with fastening materials. (3) The color separation prism according to claim 1 or 2, wherein the fastening material is made of a low thermal expansion material. (4) The color separation prism according to claim 3, wherein the low thermal expansion material is invar.