JPH0486617A - Photographic optical system - Google Patents

Abstract

PURPOSE:To obtain the photographic optical system which is inexpensive and is adequate for a color video camera, etc., by disposing a holographic optical element (HOE) on the optical path behind a photographic lens and dividing the optical path to a plurality to introduce the optical paths to an image pickup element. CONSTITUTION:The photographic lens 1 is constituted of a zoom lens 6 and an imaging lens and the HOE 2 for splitting the optical path is disposed on the optical path behind the zoom lens 6. Imagl formation lenses 7, 8, 9 are respectively disposed on the optical path O1 of the zero order transmitted light thereof and the optical paths O2, O3 of the + or -1st order diffracted light. These lenses are so disposed that subject respectively is formed on the image pickup elements 3, 4, 5. The optical path is split to three paths by just one piece of the HOE 2 in this way and moreover, the HOE 2 is inexpensive.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a photographing optical system used in a color video camera or the like.

[Conventional technology]

This kind of traditional color video camera has red and green.

A color division filter consisting of a large number of unit color filters of the three primary colors of blue arranged in a mosaic or stripe pattern is placed in front of one image sensor to separate the light into the three primary colors and make them enter each unit pixel. As described in JP-A-58-48011 and JP-A-63-306412, a color signal is generated by separating light into three primary color lights using a plurality of mirrors and prisms and making them incident on three image pickup devices. I was getting it.

[Invention or problem to be solved]

However, there is a problem in that the color division filters, mirrors, and prisms mentioned above are expensive.

Therefore, holographic optical elements (holographic optical elements), which are inexpensive because it is possible to make replicas from plastic etc., have recently been developed.
It was revealed that HOEs (hereinafter referred to as HOEs) can be used as lenses, mirrors, and optical path splitting prisms by utilizing the diffraction effect of holograms. , Chapter 7 Application to hologram optical elements),
JP-A-1-311428, JP-A-63-2003
No. 28 discloses an example of use as an optical path splitting means. However, all of these examples are used in pickup optical systems for reading optical discs, and
Since it only handles light of a single wavelength, it was unsuitable for photographing optical systems such as color video cameras.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, it is an object of the present invention to provide a photographing optical system that is inexpensive by using an HOE and is suitable for color video cameras and the like.

[Means and effects for solving the problem] The photographing optical system according to the present invention includes: disposing at least one holographic optical element on the optical path behind the photographing lens, dividing the optical path into a plurality of parts, and transmitting the optical path to the imaging element. It is something that is guided.

This will be explained in detail below.

FIG. 1 is a conceptual diagram of a photographing optical system according to the present invention.

1 is a photographing lens, 2 is a HOE for optical path division arranged on the optical path behind the photographic lens 1, and the optical path O1 of the 0th-order transmitted light and the optical path 02, ○ of the 1st-order diffracted light are, for example, respectively. The light is guided to image sensors 3 and 4.5 having peak spectral sensitivities for G, R, and H light.

In addition, when an imaging device is arranged on the optical path of the diffracted light, it is preferable to arrange the imaging device so that the light having the wavelength of the peak value of the spectral sensitivity of the imaging device is directed toward approximately the center position of the imaging device.

That is, the HOE 2 has a diffraction effect, and the diffraction angle changes depending on the wavelength. Now, R, G, B in order of longest wavelength
When G is the reference wavelength, R, which has a longer wavelength than the reference wavelength G, is diffracted by the HOE 2 at a large angle, and conversely, the diffraction angle of B becomes small.

Therefore, as shown in FIG. 2, the image sensor 4 having a peak value of spectral sensitivity at R is arranged so that its center coincides with the direction in which R is diffracted, and similarly the image sensor 5 having a peak value of spectral sensitivity at B. By aligning the center with the direction in which B is diffracted, light can be used efficiently.

According to the above configuration, the optical path can be divided into three with only -HOE2, and the HOE2 is inexpensive.

Therefore, it is possible to obtain a photographing optical system that is inexpensive and suitable for color video cameras and the like.

〔Example〕

Hereinafter, the present invention will be described in detail based on the illustrated embodiment, in which the same members as those shown in FIGS. 1 and 2 are denoted by the same reference numerals.

FIG. 3 shows the first embodiment, which is a photographic lens l.
is composed of a zoom lens 6 and an imaging lens,
A HOE for optical path splitting is provided on the optical path behind the zoom lens 6.
2 is placed on the optical path 01 of the 0th-order transmitted light and the optical path 0.2 of the ±1st-order diffracted light. ．． Imaging lenses 7, 8, and 9 are arranged above 0°, respectively, so that the subject images are formed on the imaging elements 3 and 4.5, respectively.

Note that the optical paths 02, 0 . Upper image sensor 4, 5
As shown in FIG. 2, they are arranged so that the light having the wavelength of the peak value of the spectral sensitivity of each image sensor is directed toward the center position of each image sensor. Furthermore, in order to make each image sensor have different spectral sensitivities, different color filters may be placed in front of each image sensor.

Therefore, according to the above configuration, by using the HOE, it is possible to obtain a photographing optical system that is inexpensive and suitable for a micolor video camera or the like.

FIG. 4 shows a second embodiment, in which the photographic lens 1
The object image I formed by the relay lens IO is re-imaged on the image sensor using a relay lens IO, and an optical path splitting HO is provided on the optical path behind the front group 11 of the relay lens IO.
E2 is placed on the optical path O of its 0th-order transmitted light and on the optical path 0, . 0. Rear groups 12.degree. 13.14 of the relay lenses 10 are arranged above, respectively, so that object images are formed on the image pickup devices 3, 4.5, respectively. Furthermore, the optical path of the ±1st-order diffracted light is 0. ．． 0.
HOEs 15 and 16 are arranged above, and the optical path 02 is set so that the optical axis is almost parallel to the optical path 01 of the 0th-order transmitted light.
,0. is bent.

In addition, in each of the above embodiments, the optical path is divided into three directions, but
It doesn't matter if it's in two directions or something else. It goes without saying that the photographing optical system of the present invention can also be applied to cases where light other than visible light is used. It goes without saying that the photographing optical system of the present invention can be applied not only to color video cameras that use solid-state imaging devices such as CCDs, but also to cameras that use film, for example.

Furthermore, although a plurality of image sensors are used in each of the above embodiments, an HOE consisting of, for example, a large number of minute HOEs 2 arranged two-dimensionally is created, and this is combined into a single image sensor having a large number of pixels. It is also possible to place it in front of the filter and use it instead of a color division filter.

〔Effect of the invention〕

As described above, the photographing optical system according to the present invention has important practical advantages in that it is inexpensive due to the use of HOE and is suitable for color video cameras and the like.

[Brief explanation of drawings]

FIG. 1 is a conceptual diagram of the photographing optical system according to the present invention, FIG. 2 is a diagram showing the direction of diffracted light and the preferable positional relationship between the image sensor and FIG. 3, and FIG. and second
It is a figure showing an example. 1...Photographing lens, 2,15.16...HOE
. 3.4.5...Image sensor, 6...Zoom lens, 7.8.9...Imaging lens, 10...Relay lens, 1...Front group, ■

Claims (1)

[Claims] A photographing optical system in which at least one holographic optical element is arranged on an optical path behind a photographing lens, and the optical path is divided into a plurality of parts and guided to an image pickup element.