JPH0868904A - Image pickup device - Google Patents

Abstract

PURPOSE: To prevent ghost from occurring by a light splitting prism by arranging an optical member forming an air gap making a priscribed angle (θ) with respect to a vertical axis to an image forming surface near the surface of the prism on an image pickup body. CONSTITUTION: This device is provided with the prism 2 having a semipermeable film, the prism 3 consisting of a triangle pole and a spacer 8 for making the air gap constant. Then, a light beam which is transmitted through a photographing lens 1 and whose angle is (α) is reflected on the surface 2a of the prism 2. At this time, when the refractive index of the prism is defined as (n), the incident light beam is not made incident on the image pickup body 5 because it is totally reflected on the surface 2a of the prism 2 if the angle (θ) satisfies the condition of an expression. When the angle (θ) is equal to or over the fixed angle, the light beam reflected on the surface 2a of the prism 2 is not made incident on the image pickup body 6. Therefore, when the angle (θ) is properly adjusted, the ghost light is prevented from being made incident on the image pickup bodies 5 and 6 by letting the light escape from a notched part 2d. Besides, it is good that the device is provided with a layer consisting of a material whose refractive index is low instead of the air gap.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to prevention of ghosts generated in a multi-plate type camera, and more particularly to an image pickup apparatus which prevents ghosts due to reflected light generated by a prism that splits a light beam to each image pickup body.

[0002]

2. Description of the Related Art FIG. 2 shows a main part of a conventional two-plate type camera. Reference numeral 1 is a taking lens, and only the rear end is drawn for convenience. 9
Is a prism having a semi-transmissive film 9b, and 9a is one of the light exit surfaces. 5 and 6 are image sensors such as solid-state image sensors,
Reference numerals 4 and 7 are units including a low-pass filter and protective glass for the image pickup body.

The light flux passing through the taking lens 1 is split into reflected light and transmitted light by the light splitting surface 9b of the prism 9.
The reflected light enters the image pickup body 5 and forms an image, while the transmitted light forms an image on the image pickup body 6.

In FIG. 2, among the light rays that have passed through the taking lens 1, the light rays that have entered at a certain angle α are internally reflected by the exit surface of the prism 9 and enter the image pickup body 6 to generate a ghost. There was a problem to say. Further, when the angle α is small, there is a problem that a part of the light incident on the exit surface is transmitted through this surface and is incident on the imaging body 5 as ghost light.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to prevent a ghost generated in a light splitting prism.

[0006]

SUMMARY OF THE INVENTION The present invention is an apparatus for splitting a light beam by a prism having a light splitting surface such as a semi-transmissive film and guiding the light beam to an image pickup body. By providing an air space having a predetermined angle θ with respect to the virtual axis, reflected light and transmitted light of the prism surface are prevented from entering the image pickup body as ghost light.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of the present invention. In FIG. 1, members designated by the same reference numerals as those in FIG. 2 are the same as those in FIG. In FIG. 1, 2 is a prism having a semi-transmissive film,
Reference numeral 3 is a prism formed of a triangular prism, and 8 is a spacer for keeping the air gap constant.

In FIG. 1, a photoelectric ray passing through the taking lens 1 and a ray having an angle α as shown in FIG.
Reflect at a. At this time, if the refractive index of the prism is n, the angle of θ is

[0009]

[Outside 2] In this case, the incident light ray is totally reflected by the surface 2a of the prism 2 and therefore does not enter the image pickup body 5. Further, as shown in the figure, the light ray reflected by the surface 2a of the prism 2 does not enter the image pickup body 6 as long as the angle θ is a certain value or more. Therefore, by appropriately adjusting the angle of θ, it is possible to prevent the ghost light from entering the imaging bodies 5 and 6 by allowing the light to escape from the cutout portion 2d.

For example, assuming that the distance from the surface 2c of the prism 2 to the image pickup body 6 is L and the distance from the lower end of the incident surface of the prism 2 to the lower end of the image pickup body 6 is h, the prism 2 has an angle α.
In order that the ghost light incident on

[0011]

[Outside 3] Should be satisfied. If h = 0, the above equation becomes

[0012]

[Outside 4] Becomes

One method is to provide a low refractive index material layer instead of providing an air gap, or to make the triangular prism columns 3 of a low refractive index material and bond them to the prism body.

[0014]

As described above, according to the present invention, it is possible to prevent the reflected light on the exit surface of the prism from entering the image pickup body and becoming a ghost with a simple structure, thereby improving the image pickup function.

[Brief description of drawings]

FIG. 1 is an optical sectional view showing an embodiment of the present invention.

FIG. 2 is an optical sectional view showing a conventional example.

[Explanation of symbols]

 1 Photographic lens 2 Light splitting prism 2b Light splitting surface 3 Triangular prism 5/6 Imager

Claims (2)

[Claims] 1. In a device for splitting a light beam by a prism having a light splitting surface and guiding it to an image pickup body, an air gap forming a predetermined angle θ with respect to an axis perpendicular to an image formation plane is provided in the vicinity of the image pickup body side surface of the prism. An image pickup device characterized in that a ghost is prevented by disposing an optical member to be formed. 2. With respect to the incident angle α of ghost light, the distance L from the front surface of the prism to the image pickup body, and the distance h from the lower end of the prism incident surface to the lower end of the image pickup body, The image pickup apparatus according to claim 1, wherein the image pickup apparatus is configured to satisfy the following condition.