JP2001194516A - Light resolving optical system and image pickup optical system including it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light resolving optical system and an image pickup optical system including it, which suppress influence of ghost light caused by light outside an effective part reflected by a dielectric film and obtaining excellent pictures with a simple construction. SOLUTION: In the light resolving optical system which resolves an incident luminous flux into plural colors by using at least two prisms joined together or arranged with a micro interval in between along the optical axis in series and the dielectric films applied to the light exit surfaces of the at least two prisms, a light shielding member to shield the incident light is arranged on the region on which an incident flux outside the effective part is made incident the dielectric film only transmitting the colored light and the light exit surface of the prism.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light separation optical system used for an image pickup optical system such as a television camera and a video camera, and more particularly to a prism which separates a light beam from an objective lens into a plurality of color lights and separates each of the separated colors. The present invention relates to a photoresolving optical system configured to guide light to an image sensor and an imaging optical system including the same.

[0002]

2. Description of the Related Art Conventionally, in a color television camera or the like, a color separation optical system comprising a plurality of prisms is disposed as a color separation means between an objective lens and an image pickup device.

In this color separation optical system, a plurality of prisms of a predetermined shape having a dichroic dielectric film formed of a multilayer film on one surface are used, and are integrally combined with a predetermined relationship. Then, the light beam incident from the objective lens is decomposed into each color light through each prism, and is guided to a predetermined image sensor.

FIG. 4 shows a conventional color separation optical system having three prisms having such a configuration. In the figure, reference numeral 201 denotes a three-color separation optical system,
2, 203, 204, each prism 202, 203
Each of the reflecting surfaces 202b and 203b is provided with a dichroic dielectric film, and the exit surface 204b of the prism 204 is provided with a trimming dichroic dielectric film 30 having transmission characteristics as a trimming filter. Each dichroic dielectric film has a wavelength characteristic of reflecting or transmitting according to the wavelength of light, and separates each color component by reflecting (or transmitting) an incident light beam.

[0005] Each exit surface 20 of each prism 202, 203
Image sensors (CCDs) 211, 222, and 223 are arranged on the emission side 204b of the prism 204 and 2c and 203c, respectively.

In this configuration, a light beam from an objective lens (not shown) is incident on an incident surface 202a of a prism 202 and is reflected by a first surface on a reflecting surface 202b of a dichroic dielectric film.
Only the color light (blue) is reflected, and the other components are transmitted and color-separated. The luminous flux transmitted through the reflecting surface 202b is incident from an incident surface 203a of the prism 203,
Only the second color light (red) is reflected by the reflection surface 203b of the dichroic dielectric film, and the other light beams are transmitted. The light beam transmitted through the reflecting surface 203b of the prism 203 is incident from the incident surface 204a of the prism 204, and is transmitted through the output surface 204b of the trimming dichroic dielectric film 30 so as to be emitted while removing unnecessary color components. Then, the emitted light flux forms an image on the image sensor 223.
FIG. 5C shows the transmission characteristics of the trimming dichroic dielectric film 30.

In recent years, television cameras have come to use a projection method in which an intense light source, the sun, or the like is directly captured by an image pickup unit for a special effect. For this reason, flares and the like have been greatly improved in objective lenses used in CCD cameras.

[0008]

However, the improvement of the flare made in the above-described conventional photolytic optical system is substantially the same as the expansion of the dynamic range of a television camera in such a shooting state. The result was that the ghost light, which was hidden by the flare, was hard to see until now. Such ghost light cannot always be prevented if the dichroic dielectric films of the prisms 202 and 203 have a reflectance of 90% and a transmittance of 10%. It occurs when a component is present.

For example, red light having a wavelength of 620 nm is transmitted through the reflecting surface 202b of the prism 202 as described above.
Reflective surface 20 of dichroic dielectric film of prism 203
3b. At this time, assuming that there is no loss such as absorption in the dichroic dielectric film and the prism 202, about 95% of the 620 nm light flux is transmitted through the reflecting surface 202b and the reflecting surface 203b is transmitted as shown in FIG. Then, as shown in FIG. 5B, about 94% is reflected. That is, the remaining 6% of the light flux is transmitted and incident on the prism 204, and is emitted from the emission surface 204b of the trimming dichroic dielectric film 30.
Then, as shown in FIG. 5C, about 95% is reflected and reaches the reflection surface 203b again. The light beam that has reached the reflecting surface 203b is reflected by about 94% in the direction of the emission surface 204b, and the light beam that has reached the emission surface 204b is transmitted by about 5% and enters the image sensor 223 as ghost light. Although the intensity of the ghost light is 0.3% or less before entering the prism 201, as described above, there is a problem that the ghost light becomes noticeable due to a decrease in the flare of the lens.

Accordingly, the present invention suppresses the influence of ghost light caused by light outside the effective portion reflected by the dielectric film,
It is an object of the present invention to provide a photoresolving optical system having a simple configuration capable of obtaining a good image and an imaging optical system including the same.

[0011]

In order to achieve this object, the invention according to claim 1 comprises at least two prisms which are joined or arranged with a small gap in series along the optical axis; In a photo-resolving optical system that separates incident light into a plurality of colors using a dielectric film applied to the exit surfaces of two prisms, incident light is transmitted to the dielectric film that only transmits the color light. It is characterized in that the light-blocking member for blocking is arranged in a region where a light beam outside the effective portion enters.

A second aspect of the present invention is characterized in that, in the first aspect of the present invention, the light-shielding member is adhered to an exit surface of the prism on an incident light side of the dielectric film.

According to a third aspect of the present invention, in the first or second aspect, the light shielding member is provided on a surface of the dielectric film on an incident light side.

According to a fourth aspect of the present invention, there is provided an image pickup optical system according to any one of the first to third aspects, wherein the objective lens and a light beam from the objective lens are color-separated into a plurality of color lights. And characterized in that:

[0015]

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a cross-sectional view of a main part of an image pickup optical system including a photo decomposition optical system according to an embodiment of the present invention. FIG. 2 is a schematic view of a main part of the image pickup optical system showing an effective light beam of the photo decomposition optical system of FIG. FIG. 3
FIG. 4 is an explanatory diagram showing return ghost light outside the effective portion of the light beam.

In FIG. 1, reference numeral 101 denotes a photolytic optical system.
It has a first prism 102, a second prism 103, and a third prism 104, and each reflection surface 102b, 103b of each prism 102, 103 and an emission surface 104b of the prism 104.
Is provided with a dichroic dielectric film. Each dichroic dielectric film decomposes the incident light speed for each light component by reflection and transmission. Reference numeral 10 denotes an objective lens, which condenses a light beam from a subject (not shown) and causes the light beam to enter the photolytic optical system 101. 111, 112 and 113 are C
A light beam from the objective lens 10 is decomposed into three color lights by a light resolving optical system 101, and a subject image based on each color light is picked up by the image pickup elements 111, 112, and 11.
3 are imaged. The objective lens 10 and the optical resolution optical system 101 constitute an image pickup optical system.

The first prism 102 has an incident surface 102a on which a light beam from the objective lens 10 is incident, a reflecting surface 102b provided with a dichroic dielectric film, and a reflecting surface 102b.
And an emission surface 102c for emitting the first color light (blue) reflected by the light emission surface via the incident surface 102a.

The second prism 103 includes the first prism 10
2 is an incident surface 103a on which a light beam transmitted through the reflecting surface 102b is incident, and a reflecting surface 1 on which a dichroic dielectric film is applied.
03b, and an emission surface 103 for emitting the second color light (red) reflected by the reflection surface 103b via the incidence surface 103a.
c. Although not shown, the first prism 102
Reflective surface 102b and the incident surface 103 of the second prism 103
“a” is arranged at a minute air gap in order to utilize total reflection.

Similarly, the third prism 104 has a reflection surface 1
An incident surface 104a for receiving a light beam transmitted through the light-receiving surface 03b;
It has an emission surface 104b on which a dichroic dielectric film 25 that transmits the third color light (green) of the light flux incident from the incidence surface 104a is provided. In particular, the dichroic dielectric film 25 is a trimming dichroic dielectric film having a function as a trimming filter for transmitting unnecessary color components while extracting unnecessary third color light.

This trimming dichroic dielectric film 2
Numeral 5 is applied from the outside (outgoing light side) of the exit surface 104b of the third prism 104, is the light incident side of the trimming dichroic dielectric film 25, and is provided on the exit surface 104b.
The light-shielding member 20 is adhered thereon, that is, the light-shielding member 20 is provided so as to be sandwiched between the dielectric film 25 and the emission surface 104b.

As shown in FIG. 2, the light shielding member 20
Effective light flux L of trimming dichroic dielectric film 25
It is arranged only in a light region other than the above, that is, in a region outside the effective portion.

Next, the function of the light shielding member 20 in the above configuration will be described.

The return ghost light outside the effective portion of the emission surface 104b on which the trimming dichroic dielectric film 25 is applied is shown by oblique lines in FIG. This ghost light
Trimming dichroic dielectric film 25 (emission surface 104
b), the light is returned to the third prism 104, and is reflected again by the reflection surface 103b of the second prism 103 in the direction of the emission surface 104b, so that the trimming dichroic dielectric film 25 is formed.
(Emission surface 104b) to generate ghost light.

However, as shown in FIG. 2, the third prism 104 is transmitted through the reflecting surface 103b of the second prism 103.
All the light fluxes outside the effective portion which enter the inside are blocked by the light shielding member 20.
And the light does not reach the trimming dichroic dielectric film 25 on the exit surface 104b, so that reflected light (return light) from the trimming dichroic dielectric film 25 in this portion does not occur. For this reason, it is possible to prevent ghost light and flare light caused by the return light from entering the image sensor 113.

Therefore, in an image pickup optical system (image pickup apparatus) equipped with such a photoresolving optical system, no ghost light is present even in a situation where the ghost light has been used in the past and the photographing was suspended. It has become possible to take good images.

As described above, the light beam outside the effective portion incident on the dielectric film 25 is blocked by the light shielding member 20 so that the return light due to the trimming dichroic dielectric film 25 which can be originally ghost light is not generated. Ghost light is prevented from entering the image sensor.

As described above, the light shielding member 20 is provided with the third
Although it is adhered to the exit surface 104b of the prism 104,
Since there is such an adhesive surface with the glass member, there is also an advantage that a strong adhesive strength can be obtained.

In the above embodiment, the description has been made using the three light-resolving prisms 102, 103, and 104.
It goes without saying that the same effect can be obtained in other photo-decomposition optical systems that decompose a light beam into a plurality.

In this embodiment, the prism 10
Although the trimming dichroic dielectric film 25 was employed as the dielectric film applied to the emission surface 104b of No. 4, the same effect can be obtained regardless of whether the dielectric film used for this is a single-layer film or a multilayer film. it can. The material used for the light shielding member 20 may be any material that can block light, such as an organic film containing black carbon, a metal film, a dielectric film, a metal foil, and a resin film.

Further, in this embodiment, the light shielding member 20 is provided only on the exit surface 104b of the prism 104. However, the present invention is not limited to the purpose of preventing the generation of ghost light, but takes in only an effective light flux and removes unnecessary color components. For the purpose of removal, the trimming dichroic dielectric film 25 and the light shielding member 20 provided on the dielectric film 25 are moved to the image pickup devices 111 and 11.
2 can also be arranged at the front position or the like.

[0032]

According to the present invention, as described above, a light-blocking member that blocks incident light is provided between a dielectric film that only transmits color light and guides an image to an image pickup device and an exit surface of a prism. Since the light beam outside the effective portion is disposed only in the region where the light beam enters, the light beam outside the effective portion is blocked so as not to hit the dielectric film, and the generation of return light in the dielectric film is prevented. Therefore, the influence of the ghost light caused by the return light can be suppressed as much as possible, so that it is possible to provide an imaging optical system such as a television camera capable of obtaining a good image.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a main part of an imaging optical system including a photolytic optical system according to an embodiment of the present invention.

FIG. 2 is a schematic diagram of a main part of an imaging optical system showing an effective light beam of the photolytic optical system of FIG. 1;

FIG. 3 is an explanatory diagram showing return ghost light outside the effective portion of the light beam;

FIG. 4 is a schematic view of a main part showing a conventional photolytic optical system.

FIG. 5 is a characteristic diagram showing light transmission characteristics of a trimming dichroic dielectric film.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 101 Photo-resolution optical system 102 1st prism 103 2nd prism 104 3rd prism 102b, 103b Reflection surface 104b Emission surface 111, 112, 113 Image sensor 10 Objective lens 20 Shielding member 25 Trimming dichroic dielectric film

Claims (4)

[Claims] 1. Using at least two prisms joined or arranged in series with a small gap along an optical axis, and a dielectric film applied to an exit surface of the at least two prisms, In a photo-resolving optical system that separates an incident light beam into a plurality of light beams, a light-blocking member that blocks incident light is disposed between the dielectric film that only transmits the color light and the exit surface of the prism. A light-resolving optical system, wherein the light-resolving optical system is disposed in a region where the light flux of the light enters. 2. The photolytic optical system according to claim 1, wherein the light shielding member is bonded on an exit surface of the prism on an incident light side of the dielectric film. 3. The light shielding member is disposed on an incident light side of the dielectric film.
The photolytic optical system as described. 4. An objective lens, and a light separation optical system according to claim 1, which separates a light beam from the objective lens into a plurality of color lights. Imaging optics.