WO2018216386A1 - Color separation optical system, imaging unit, and imaging device - Google Patents

Abstract

The present invention provides a color separation optical system, an imaging unit, and an imaging device capable of suppressing color shading. A color separation optical system (10) is constituted by combining a first prism (12) for extracting B light, a second prism (14) for extracting R light, a third prism (16) for extracting IR light, and a fourth prism (18) for extracting G light. The first prism 12 reflects B light at the second surface (12b) thereof to separate B light. The second prism (14) reflects R light at the second surface (14b) thereof to separate R light. The third prism (16) reflects IR light at the second surface (16b) thereof to separate IR light. The color separation optical system (10) is constituted such that the second surface (16b) of the third prism maximizes the incidence angle of light passing through an optical axis Lz.

Description

Color separation optical system, imaging unit, and imaging apparatus

The present invention relates to a color separation optical system, an image pickup unit, and an image pickup apparatus, and in particular, a color separation optical system that separates an incident light beam into light of three color components in the visible region and light of one color component in the invisible region. The present invention relates to an imaging unit including the color separation optical system and an imaging apparatus including the imaging unit.

The light that has passed through the lens is R (R: Red), G (G: Green), B (B: Blue), and IR (IR: InfraRed / Infrared) by a color separation optical system. 4), an image pickup apparatus that picks up an RGB image and an IR image by individually receiving the decomposed lights with four image sensors (see, for example, Patent Document 1). -3 etc.). Here, the RGB image is an image in which one pixel is composed of three color component values of R, G, and B. The RGB image constitutes a so-called color image. An IR image is an image in which one pixel is composed of one color component value of IR.

JP 2016-178995 JP JP-A-2015-180864 JP 2017-29763 A

However, when the color separation optical system is used, there is a drawback that color shading occurs in the color image to be captured. Color shading is a phenomenon in which the top and bottom edges of a screen are colored even when white balance is achieved at the center of the screen. Color shading occurs due to the size of the incident angle on the color separation surface, and the amount of generation increases as the size increases. The color shading is visually recognized as color unevenness and greatly reduces the image quality.

The present invention has been made in view of such circumstances, and an object thereof is to provide a color separation optical system, an imaging unit, and an imaging apparatus that can suppress the occurrence of color shading.

Measures for solving the above problems are as follows.

(1) A color separation optical system that separates an incident light beam into light of three color components in the visible region and light of one color component in the invisible region, and reflects the light of the first color component in the visible region. A first visible light separation surface that separates and separates light of a second color component in the visible region, and a non-visible light separation surface that reflects and separates light in the non-visible region. On the optical axis, and the first visible light separating surface, the second visible light separating surface, and the invisible light separating surface, the surface having the maximum incident angle of light passing through the optical axis is the invisible light separating surface. There is a color separation optical system.

According to the present invention, the color separation optical system includes three separation surfaces, and separates the incident light beam into light of three color components in the visible region and light of one color component in the invisible region. The three separation surfaces include a first visible light separation surface, a second visible light separation surface, and a non-visible light separation surface. The first visible light separation surface separates the light of the first color component in the visible region. The second visible light separation surface separates the light of the second color component in the visible region. The non-visible light separation surface separates light in the non-visible region. The light transmitted through all the separation surfaces is separated as the light of the third color component in the visible region. Each separation surface selectively reflects light of a color component to be separated and separates it from light of other color components. At this time, each separation surface is arranged so that light of a color component to be separated is reflected in a predetermined direction. Therefore, each separation surface is disposed to be inclined with respect to the optical axis. In the color separation optical system of this aspect, the inclination of each separation surface is set so that the surface where the incident angle of light passing through the optical axis is the maximum among the three separation surfaces is the invisible light separation surface. Thereby, generation | occurrence | production of the color shading at the time of imaging the color image by visible light can be suppressed. Color shading occurs due to the size of the incident angle on the color separation surface, and the amount of generation increases as the size increases. By setting the surface where the incident angle of light passing through the optical axis is maximum as the non-visible light separating surface, the incident angle at the separating surface for separating the light of the color component in the visible region can be reduced. Thereby, generation | occurrence | production of the color shading at the time of imaging the color image by visible light can be suppressed.

(2) The non-visible light separation surface is disposed so as to be inclined to an angle at which all light is incident at an incident angle larger than the Brewster angle when a light flux having an F number of 2.0 is incident from the lens. The color separation optical system according to (1) above.

According to this aspect, the non-visible light separation surface is inclined and arranged as follows. That is, when a light flux having an F number of 2.0 is incident from the lens, all the light beams are arranged to be inclined at an incident angle larger than the Brewster angle. Here, the concept of “all light” includes a range that can be regarded as almost all. Thereby, it can suppress that a light quantity difference arises in a screen, when imaging the image by invisible light. The Brewster angle (polarization angle) is an incident angle at which the reflectance of p-polarized light becomes 0 at the interface between substances having different refractive indexes. When a light beam having an F number of 2.0 is incident from the lens, the Brewster is arranged by setting the angle at which all light is incident at an incident angle larger than the Brewster angle, and arranging the invisible light separation surface. Generation of light incident at an angle can be effectively suppressed. Thereby, even if it is a case where a light quantity difference arises, it can suppress to the level which does not have a problem practically.

(3) The invisible light separation surface is arranged to be inclined at an angle at which all light is incident at an incident angle larger than the Brewster angle when the light beam having the maximum aperture is incident from the lens. Color separation optical system.

According to this aspect, the non-visible light separation surface is inclined and arranged as follows. That is, when the light beam having the maximum aperture is incident from the lens, all the light beams are disposed so as to be inclined at an incident angle larger than the Brewster angle. Here, the concept of “all light” includes a range that can be regarded as almost all. Thereby, it can suppress that a light quantity difference arises in a screen, when imaging the image by invisible light.

(4) A first visible light reflecting surface that is reflected in a direction in which light of the first color component in the visible region separated by the first visible light separating surface is emitted, and a second visible region that is separated by the second visible light separating surface. The color separation optical system according to any one of (1) to (3), further including a second visible light reflecting surface that reflects the light of the color component in a direction in which the light is emitted.

According to this aspect, the first visible light reflecting surface that is reflected in the direction in which the light of the first color component in the visible region separated by the first visible light separating surface is emitted and the visible region that is separated by the second visible light separating surface. And a second visible light reflecting surface that reflects the second color component in the direction in which the light of the second color component is emitted. Thereby, it is possible to prevent the first color component image and the second color component image in the visible region from being taken out as mirror (inverted) images of the third color component image. Since each image can be taken out in a uniform manner, subsequent processing can be simplified. The light in the invisible region separated by the invisible light separation surface may be emitted as it is without being reflected, or may be further reflected and emitted. When the light is emitted without being reflected, the configuration of the color separation optical system can be simplified. On the other hand, when the light is further reflected and emitted, the invisible light image can be prevented from being taken out as a mirror image of the visible light image.

(5) The first visible light separation surface, the second visible light separation surface, and the non-visible light separation surface are arranged in order of the first visible light separation surface, the second visible light separation surface, and the non-visible light separation surface from the incident side. The color separation optical system according to any one of (1) to (4) above.

According to this aspect, the first visible light separation surface, the second visible light separation surface, and the non-visible light separation surface are the first visible light separation surface, the second visible light separation surface, and the non-visible light separation surface from the incident side. Arranged in order. By making the final separation surface a non-visible light separation surface, shading of color images can be reduced to a minimum.

(6) A first exit surface that emits light of the first color component in the visible region separated by the first incident surface on which the light flux from the lens is incident, the first visible light separation surface, and the first visible light separation surface. A first prism having a second incident surface that is joined to the first visible light separating surface and is transmitted through the first visible light separating surface, a second visible light separating surface, and a second visible light. A second prism having a second emission surface that emits light of the second color component in the visible region separated by the light separation surface, joined to the second visible light separation surface, and transmitted through the second visible light separation surface A third prism having a third incident surface on which a light beam is incident, a non-visible light separating surface, and a third emitting surface that emits light in a non-visible region separated by the non-visible light separating surface; A fourth incident surface that is joined to the separation surface and receives the light beam that has passed through the non-visible light separation surface, and emits light of the third color component in the visible region. The fourth emission surface and the fourth any one of the color separation optical system and the prism, the above (1) with a (3) having to be.

According to this aspect, the color separation optical system is configured by a so-called composite prism, and is configured by combining the first prism, the second prism, the third prism, and the fourth prism. The first prism emits the first color component light in the visible region separated by the first incident surface on which the light flux from the lens is incident, the first visible light separating surface, and the first visible light separating surface. And an exit surface. The second prism includes a second incident surface on which a light beam transmitted through the first visible light separation surface is incident, a second visible light separation surface, and a second color component in the visible region separated by the second visible light separation surface. A second emission surface that emits light. The third prism emits light in a non-visible region separated by the third incident surface on which the light beam transmitted through the second visible light separation surface is incident, the non-visible light separation surface, and the non-visible light separation surface. And an exit surface. The fourth prism includes a fourth incident surface on which a light beam that has passed through the non-visible light separation surface is incident, and a fourth emission surface that emits light of the third color component in the visible region. The first prism and the second prism are joined to each other between the first visible light separation surface of the first prism and the second incident surface of the second prism. The second prism and the third prism are joined to each other between the second visible light separation surface of the second prism and the third incident surface of the third prism. The third prism and the fourth prism are joined to each other between the invisible light separation surface of the third prism and the fourth incident surface of the fourth prism. The light beam from the lens first enters the first incident surface of the first prism. The light beam incident on the first incident surface is separated by selectively reflecting the light of the first color component in the visible region on the first visible light separation surface of the first prism. The separated light of the first color component in the visible region is emitted from the first emission surface of the first prism. The light beam that has passed through the first visible light separation surface of the first prism then enters the second incident surface of the second prism. The light beam incident on the second incident surface is separated by selectively reflecting the light of the second color component in the visible region on the second visible light separation surface of the second prism. The separated light of the second color component in the visible region is emitted from the second emission surface of the second prism. The light beam that has passed through the second visible light separation surface of the second prism then enters the third incident surface of the third prism. The light beam incident on the third incident surface is separated by selectively reflecting the light in the invisible region on the invisible light separation surface of the third prism. The separated light in the invisible region is emitted from the third emission surface of the third prism. The light beam that has passed through the invisible light separation surface of the third prism then enters the fourth incident surface of the fourth prism. The light beam incident on the fourth entrance surface is emitted from the fourth exit surface as light of the third color component in the visible region.

(7) The first prism causes the first color component light in the visible region separated by the first visible light separation surface to be totally reflected by the first incident surface and emitted from the first emission surface, and the second prism is The second incident surface is joined to the first visible light separating surface through the air gap, and the second color component light in the visible region separated by the second visible light separating surface is totally reflected by the second incident surface, (2) The color separation optical system according to (6), which is emitted from two emission surfaces.

According to this aspect, the first incident surface of the first prism and the second incident surface of the second prism are constituted by so-called total reflection surfaces. The light of the first color component in the visible region separated by the first visible light separation surface of the first prism is totally reflected by the first incidence surface and emitted from the first emission surface. The light of the second color component in the visible region separated by the second visible light separation surface of the second prism is totally reflected by the second incident surface and emitted from the second emission surface. The second prism is joined to the first prism via an air gap so that the second incident surface is configured as a total reflection surface.

(8) The color separation optical system according to any one of (1) to (7), wherein the invisible light separation surface separates infrared light.

According to this aspect, the invisible light separation surface separates infrared light (IR light). The light in the visible region can be separated into R light, G light, and B light, for example. In this case, for example, the B light is separated by the first visible light separation surface, and the R light is separated by the second visible light separation. Further, the light transmitted through all the separation surfaces is separated as G light.

(9) The color separation optical system according to any one of (1) to (8) above, a first visible light image sensor that receives light of the first color component in the visible region resolved by the color separation optical system, A second visible light image sensor that receives light of the second color component in the visible region resolved by the color separation optical system, and a third that receives light of the third color component in the visible region resolved by the color separation optical system. An imaging unit comprising: a visible light image sensor; and a non-visible light image sensor that receives light in a non-visible region separated by a color separation optical system.

According to this aspect, the color separation optical system is configured as the imaging unit including the image sensor. The color separation optical system includes a first visible light image sensor that receives light of the first color component in the separated visible region, a second visible light image sensor that receives light of the second color component in the visible region, and a visible light. A third visible light image sensor that receives light of the third color component in the region and a non-visible light image sensor that receives light in the invisible region are provided.

(10) An imaging apparatus comprising a housing, the imaging unit according to (9) housed in the housing, and a mount that is provided in the housing and on which a lens is detachably mounted.

According to this aspect, the imaging unit is incorporated in the imaging device capable of exchanging lenses. The lens is attached / detached via a mount provided in the housing.

(11) The imaging device according to (10), wherein the flange back has an air equivalent length of 12.5 mm or more and 19 mm or less.

According to this aspect, the flange back of the imaging device is configured with an air equivalent length of 12.5 mm or more and 19 mm or less. The flange back is a distance from the mount surface to the light receiving surface of the image sensor. For example, an imaging apparatus that employs a C mount or a CS mount corresponds to this. The C mount is a standard mount having an inner diameter of 24.4 mm (1 inch), a pitch of 0.794 mm (32 peaks / 1 inch), and a flange back of 17.526 mm (air conversion length). The CS mount has a C-mount flange back of 12.5 mm (air equivalent length).

According to the present invention, the occurrence of color shading can be suppressed.

The figure which shows an example of a structure of an imaging unit The figure which expanded the part of A, B, and C of FIG. The figure which shows the relationship of the incident angle of the light which injects into the 3rd prism 2nd surface from a lens. The figure which shows the structural example of the color separation optical system in the case of reflecting IR light twice and taking out The figure which expanded the part of A, B, and C of FIG. The figure which shows an example of a structure of a camera Block diagram showing the electrical configuration of the camera Block diagram of the main functions realized by the camera microcomputer The figure which shows an example of an electronic endoscope The block diagram which shows schematic structure of the display processing apparatus in the case of displaying an RGB image and IR image superimposed The figure which shows an example of a display of RGB image, IR image, and a synthesized image A table showing the relationship between the refractive index n1 of the third prism, the Brewster angle γ determined from the refractive index n1, and the condition of the incident angle that should be satisfied by the second surface of the third prism.

Hereinafter, preferred embodiments for carrying out the present invention will be described in detail with reference to the accompanying drawings.

◆◆ Color separation optical system and imaging unit ◆◆
[Configuration of color separation optical system and imaging unit]
FIG. 1 is a diagram illustrating an example of the configuration of the imaging unit.

The imaging unit 1 includes a color separation optical system 10 that decomposes an incident light beam into four color component lights, and four image sensors that individually receive the four color component lights separated by the color separation optical system 10. 30R, 30G, 30B, and 30IR.

<Color separation optics>
The color separation optical system 10 of this embodiment decomposes an incident light beam into R light (red light), G light (green light), B light (blue light), and IR light (infrared light). R light, G light, and B light are examples of light of three color components in the visible region. IR light is an example of light of a color component in a non-visible region.

As shown in FIG. 1, the color separation optical system 10 is configured by combining four prisms of a first prism 12, a second prism 14, a third prism 16, and a fourth prism 18. The four prisms are arranged in the order of the first prism 12, the second prism 14, the third prism 16, and the fourth prism 18 from the light incident side along the optical axis Lz. In the color separation optical system 10 of the present embodiment, the first prism 12 extracts the B light Lb, the second prism 14 extracts the R light Lr, the third prism 16 extracts the IR light Lir, and the fourth prism 18 extracts the G light Lg.

<First prism>
The first prism 12 is a prism that extracts the B light Lb. The first prism 12 has a first prism first surface 12a, a first prism second surface 12b, and a first prism third surface 12c.

The first prism first surface 12a functions as a first incident surface and a first visible light reflecting surface. The first prism first surface 12a is disposed on the optical axis Lz and is disposed orthogonal to the optical axis Lz. The light that has passed through the lens 2 first enters the first prism first surface 12a.

The first prism second surface 12b functions as a first visible light separation surface. The first prism second surface 12b is disposed on the optical axis Lz and is inclined with respect to the optical axis Lz.

FIG. 2 (A) is an enlarged view of a circle A indicated by a broken line in FIG. As shown in the drawing, the first prism second surface 12b is disposed to be inclined with respect to the optical axis Lz so that light passing through the optical axis Lz is incident at an incident angle α1.

B light reflecting dichroic film (not shown) is provided on the first prism second surface 12b. The B light reflecting dichroic film selectively reflects only the B light Lb, which is the light of the first color component in the visible region, and transmits the light of the other color components. By selectively reflecting only the B light Lb by the B light reflecting dichroic film, the B light Lb is separated from the incident light.

The B light Lb separated by the first prism second surface 12b is reflected toward the first prism first surface 12a. As described above, the first prism first surface 12a also functions as a first visible light reflecting surface. The B light Lb separated by the first prism second surface 12b is incident on the first prism first surface 12a at a predetermined incident angle. This incident angle is an angle at which the first prism first surface 12a is totally reflected. The first prism first surface 12a totally reflects the B light Lb separated by the first prism second surface 12b toward the first prism third surface 12c.

The first prism third surface 12c functions as a first emission surface. The B light Lb totally reflected by the first prism first surface 12a is emitted from the first prism third surface 12c.

B light trimming filter 20B is provided on the first prism third surface 12c. The B light trimming filter 20B cuts off extra color component light from the B light and improves the color reproducibility of the B light.

<Second prism>
The second prism 14 is a prism that extracts the R light Lr. The second prism 14 has a second prism first surface 14a, a second prism second surface 14b, and a second prism third surface 14c.

The second prism first surface 14a functions as a second incident surface and a second visible light reflecting surface. The second prism first surface 14a is disposed on the optical axis Lz and is inclined with respect to the optical axis Lz. The inclination angle is set to the same angle as the inclination angle of the first prism second surface 12b with respect to the optical axis Lz. That is, the second prism first surface 14a is disposed in parallel with the first prism second surface 12b.

The second prism first surface 14 a also functions as a joint surface with the first prism 12. The second prism first surface 14a is joined to the first prism second surface 12b via a frame-shaped spacer 22, for example. As a result, the first prism second surface 12 b and the second prism first surface 14 a are joined via the air gap 24. The light transmitted through the first prism second surface 12 b enters the second prism first surface 14 a through the air gap 24.

The second prism second surface 14b functions as a second visible light separation surface. The second prism second surface 14b is disposed on the optical axis Lz and is inclined with respect to the optical axis Lz.

FIG. 2B is an enlarged view of a circle B indicated by a broken line in FIG. As shown in the figure, the second prism second surface 14b is disposed to be inclined with respect to the optical axis Lz so that light passing through the optical axis Lz is incident at an incident angle α2.

The second prism second surface 14b is provided with an R light reflecting dichroic film (not shown). The R light reflecting dichroic film selectively reflects only the R light Lr, which is the light of the second color component in the visible region, and transmits the light of the other color components. By selectively reflecting only the R light Lr by the R light reflecting dichroic film, the R light Lr is separated from the incident light.

The R light Lr separated by the second prism second surface 14b is reflected toward the second prism first surface 14a. As described above, the second prism first surface 14a also functions as a second visible light reflecting surface. The R light Lr separated by the second prism second surface 14b is incident on the second prism first surface 14a at a predetermined incident angle. This incident angle is an angle at which the second prism first surface 14a is totally reflected. The second prism first surface 14a totally reflects the R light Lr separated by the second prism second surface 14b toward the second prism third surface 14c.

The second prism third surface 14c functions as a second emission surface. The R light Lr totally reflected by the second prism first surface 14a is emitted from the second prism third surface 14c.

The R prism trimming filter 20R is provided on the second prism third surface 14c. The R light trimming filter 20R cuts off extra color component light from the R light and improves the color reproducibility of the R light.

<Third prism>
The third prism 16 is a prism that extracts IR light Lir. The third prism 16 has a third prism first surface 16a, a third prism second surface 16b, and a third prism third surface 16c.

The third prism first surface 16a functions as a third incident surface. The third prism first surface 16a is disposed on the optical axis Lz and is inclined with respect to the optical axis Lz. The inclination angle is set to the same angle as the inclination angle of the second prism second surface 14b with respect to the optical axis Lz. That is, the third prism first surface 16a is disposed in parallel with the second prism second surface 14b.

The third prism first surface 16 a also functions as a joint surface with the second prism 14. The third prism first surface 16a is bonded to the second prism second surface 14b via an adhesive layer (not shown). Thereby, the 2nd prism 14 and the 3rd prism 16 are integrated. The light transmitted through the second prism second surface 14b is incident on the third prism first surface 16a.

The third prism second surface 16b functions as an invisible light separation surface. The third prism second surface 16b is disposed on the optical axis Lz and is inclined with respect to the optical axis Lz.

FIG. 2C is an enlarged view of a circle C indicated by a broken line in FIG. As shown in the figure, the third prism second surface 16b is disposed to be inclined with respect to the optical axis Lz so that light passing through the optical axis Lz is incident at an incident angle α3. The incident angle α3 is larger than the incident angle α1 on the first prism second surface 12b and the incident angle α2 on the second prism second surface 14b (α1 <α3 and α2 <α3). That is, in the color separation optical system 10 according to the present embodiment, the third prism second of the three separation surfaces (the first prism second surface 12b, the second prism second surface 14b, and the third prism second surface 16b). The incident angle α3 with respect to the two surfaces 16b is configured to be the largest. Thereby, it can suppress that color shading generate | occur | produces in a color image. This will be described in detail later.

The third prism second surface 16b is provided with an IR light reflecting dichroic film (not shown). The IR light reflecting dichroic film selectively reflects only the IR light Lir, which is light in a non-visible region, and transmits light of other color components. By selectively reflecting only the IR light Lir by the IR light reflecting dichroic film, the IR light Lir is separated from the incident light. The IR light Lir separated by the third prism second surface 16b is reflected toward the third prism third surface 16c.

The third prism third surface 16c functions as a third emission surface. The IR light Lir separated by the third prism second surface 16b is directly emitted from the third prism third surface 16c.

The third prism third surface 16c is provided with an IR light trimming filter 20IR. The IR light trimming filter 20IR can cut off light of an extra color component from the IR light and obtain IR light with a high S / N ratio.

<4th prism>
The fourth prism 18 is a prism that extracts the G light Lg. The fourth prism 18 has a fourth prism first surface 18a and a fourth prism second surface 18b.

The fourth prism first surface 18a functions as a fourth incident surface. The fourth prism first surface 18a is disposed on the optical axis Lz and is inclined with respect to the optical axis Lz. The inclination angle is set to the same angle as the inclination angle of the third prism second surface 16b with respect to the optical axis Lz. That is, the fourth prism first surface 18a is arranged in parallel with the third prism second surface 16b.

The fourth prism first surface 18 a also functions as a joint surface with the third prism 16. The fourth prism first surface 18a is joined to the third prism second surface 16b via an adhesive layer (not shown). Thereby, the third prism 16 and the fourth prism 18 are integrated. The light transmitted through the third prism second surface 16b is incident on the fourth prism first surface 18a.

The fourth prism second surface 18b functions as a fourth emission surface. The fourth prism second surface 18b is disposed on the optical axis Lz and is orthogonal to the optical axis Lz. The light incident on the fourth prism first surface 18a is emitted from the fourth prism third surface 18c as it is. Here, the light incident on the fourth prism first surface 18a is light obtained by separating the B light, the R light, and the IR light. The light obtained by separating the B light, R light, and IR light is emitted from the fourth prism second surface 18b as G light that is the third color component light in the visible region.

The G prism trimming filter 20G is provided on the fourth prism second surface 18b. The G light trimming filter 20G cuts extra color component light from the G light and improves the color reproducibility of the G light.

<Image sensor>
The four image sensors include a B light image sensor 30B that receives the B light Lb, an R light image sensor 30R that receives the R light Lr, a G light image sensor 30G that receives the G light Lg, and an IR light that receives the IR light Lir. The image sensor 30IR is configured. Each image sensor is composed of an area image sensor such as a CCD (Charged Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor).

<B light image sensor>
The B light image sensor 30B is an example of a first visible light image sensor. The B light image sensor 30B receives the B light Lb, which is the light of the first color component in the visible region, separated by the color separation optical system 10, converts it to an electrical signal, and outputs it. The B light image sensor 30B is attached to the first prism third surface 12c of the first prism 12 or the B light trimming filter 20B via a holder (not shown). The light receiving surface of the B light image sensor 30B is disposed on the optical axis of the B light Lb emitted from the first prism third surface 12c, and is disposed orthogonal to the optical axis.

<R light image sensor>
The R light image sensor 30R is an example of a second visible light image sensor. The R light image sensor 30R receives the R light Lr that is the light of the second color component in the visible region separated by the color separation optical system 10, converts it to an electrical signal, and outputs it. The R light image sensor 30R is attached to the second prism third surface 14c of the second prism 14 or the R light trimming filter 20R via a holder (not shown). The light receiving surface of the R light image sensor 30R is disposed on the optical axis of the R light Lr emitted from the second prism third surface 14c, and is disposed orthogonal to the optical axis.

<G light image sensor>
The G light image sensor 30G is an example of a third visible light image sensor. The G light image sensor 30G receives the G light Lg, which is the light of the third color component in the visible region, separated by the color separation optical system 10, converts it to an electrical signal, and outputs it. The G light image sensor 30G is attached to the fourth prism second surface 18b of the fourth prism 18 or the G light trimming filter 20G via a holder (not shown). The light receiving surface of the G light image sensor 30G is disposed on the optical axis of the G light Lg emitted from the fourth prism second surface 18b, and is disposed orthogonal to the optical axis.

<IR optical image sensor>
The IR light image sensor 30IR is an example of a non-visible light image sensor. The IR light image sensor 30IR receives IR light Lir which is light in a non-visible region separated by the color separation optical system 10, converts it to an electrical signal, and outputs it. The IR light image sensor 30IR is attached to the third prism third surface 16c of the third prism 16 or the IR light trimming filter 20IR via a holder (not shown). The light receiving surface of the IR light image sensor 30IR is disposed on the optical axis of the IR light Lir emitted from the third prism third surface 16c, and is disposed orthogonal to the optical axis.

[Operation of color separation optical system and imaging unit]
《Color separation》
In the imaging unit 1 of the present embodiment, the light passing through the lens 2 is decomposed into light of four color components (R light, G light, B light, and IR light) by the color separation optical system 10, and each light is converted into 4 Light is individually received by two image sensors (R light image sensor 30R, G light image sensor 30G, B light image sensor 30B, and IR light image sensor 30IR).

The light that has passed through the lens 2 first enters the first prism first surface 12a. As for the light incident on the first prism first surface 12a, only the B light Lb is selectively reflected on the first prism second surface 12b. As a result, the B light Lb is separated from the light incident on the first prism 12.

The separated B light Lb is reflected toward the first prism first surface 12a and is incident on the first prism first surface 12a. The B light Lb incident on the first prism first surface 12a is totally reflected by the first prism first surface 12a and emitted from the first prism third surface 12c. The B light Lb emitted from the first prism third surface 12c is incident on the light receiving surface of the B light image sensor 30B via the B light trimming filter 20B.

Light of color components other than the B light Lb passes through the first prism second surface 12 b and enters the second prism first surface 14 a through the air gap 24. Of the light incident on the second prism first surface 14a, only the R light Lr is selectively reflected by the second prism second surface 14b. Thereby, the R light Lr is separated from the light incident on the second prism 14.

The separated R light Lr is reflected toward the second prism first surface 14a and is incident on the second prism first surface 14a. The R light Lr incident on the second prism first surface 14a is totally reflected by the second prism first surface 14a and emitted from the second prism third surface 14c. The R light Lr emitted from the second prism third surface 14c enters the light receiving surface of the R light image sensor 30R via the R light trimming filter 20R.

Light of color components other than the R light Lr is transmitted through the second prism second surface 14b and is incident on the third prism first surface 16a. As for the light incident on the third prism first surface 16a, only the IR light Lir is selectively reflected on the third prism second surface 16b. Thereby, the IR light Lir is separated from the light incident on the third prism 16.

The separated IR light Lir is reflected toward the third prism third surface 16c and emitted from the third prism third surface 16c. The IR light Lir emitted from the third prism third surface 16c enters the light receiving surface of the IR light image sensor 30IR via the IR light trimming filter 20IR.

Light of color components other than the IR light Lir is transmitted through the third prism second surface 16b and is incident on the fourth prism first surface 18a. The light incident on the fourth prism first surface 18a is emitted from the fourth prism second surface 18b as it is as G light Lg. The G light Lg emitted from the fourth prism second surface 18b enters the light receiving surface of the G light image sensor 30G via the G light trimming filter 20G.

《Image generation》
As described above, according to the imaging unit 1 of the present embodiment, the light passing through the lens 2 is converted into light of four color components (R light, G light, B light, and IR light) by the color separation optical system 10. Each light can be individually received by four image sensors (R light image sensor 30R, G light image sensor 30G, B light image sensor 30B, and IR light image sensor 30IR).

RGB signals that are color images can be generated by processing signals output from the R light image sensor 30R, the G light image sensor 30G, and the B light image sensor 30B. Further, an IR image can be generated by processing a signal output from the IR light image sensor 30IR.

Since the IR light Lir is reflected and emitted only once, the image formed on the light receiving surface of the IR light image sensor 30IR is a mirror image (reverse image) with respect to the RGB image. Therefore, it is necessary to perform a required inversion process for the IR image. On the other hand, the color separation optical system 10 can be made compact by adopting a configuration in which the IR light Lir is reflected and extracted only once.

Incidentally, as described above, in the imaging unit 1 of the present embodiment, the first of the three separation surfaces (the first prism second surface 12b, the second prism second surface 14b, and the third prism second surface 16b). The third prism second surface 16b is configured such that the incident angle of light passing through the optical axis Lz is maximized (α1 <α3 and α2 <α3). The third prism second surface 16b is a surface that separates the IR light Lir. In this way, by configuring such that the incident angle of light passing through the optical axis Lz is maximized on the surface that separates the IR light Lir, occurrence of color shading in the RGB image can be effectively suppressed.

Color shading occurs due to the size of the incident angle on the color separation surface, and the larger the size, the larger the generation amount. The surface (first prism) that separates the light of the color component in the visible region by setting the surface having the maximum incident angle of the light passing through the optical axis Lz as the separation surface (third prism second surface 16b) of the IR light Lir. It can suppress that the incident angle to the surface of the 2nd surface 12b and the 2nd prism 2nd surface 14b) becomes large. As a result, the occurrence of color shading in the RGB image that is a color image can be suppressed, and a high quality color image can be generated.

[Preferred setting of IR light separation surface (third prism second surface)]
The third prism second surface 16b, which is a separation surface of the IR light Lir, is preferably set so as to avoid the incident angle from becoming a Brewster angle.

Here, the Brewster angle (polarization angle) is an incident angle at which the reflectance of p-polarized light becomes 0 at the interface between substances having different refractive indexes. The Brewster angle γ is obtained from the refractive indexes of the two substances, and is obtained by the formula γ = Arctan (n2 / n1). Here, n1 is the refractive index on the incident side, and n2 is the refractive index on the transmission side. For example, the refractive index of the third prism 16 (incidence-side refractive index n1) is 1.8, and the refractive index of the adhesive that joins the third prism 16 and the fourth prism 18 (transmission-side refractive index n2). Is 1.52, the Brewster angle in the third prism second surface 16b is approximately 40.18 degrees. When the incident angle is the Brewster angle, the angle formed between the transmitted light (refracted light) and the reflected light is 90 degrees.

When light is incident on the third prism second surface 16b at the Brewster angle, the amount of light of the separated IR light Lir decreases by the amount of the p-polarized component. Therefore, it is preferable to avoid the incident angle of the light incident on the third prism second surface 16b from becoming the Brewster angle. Thereby, it is possible to prevent a difference in the amount of light in the screen and to capture a high-quality IR image.

In order to avoid that the incident angle of the light incident on the second prism second surface 16b becomes the Brewster angle, for example, when the light beam having the maximum aperture is incident from the lens, almost all the light is less than the Brewster angle. The third prism second surface 16b may be set so as to be incident at a large incident angle.

FIG. 3 is a diagram showing the relationship of the incident angle of light incident on the second surface of the third prism from the lens. This figure shows an example when a light beam having a maximum aperture is incident.

As shown in the figure, when the third prism second surface 16b is inclined downward, the light incident at the largest incident angle passes through the lower end of the lens 2 and enters the third prism second surface 16b. It is. The third prism second surface 16b is set so that the incident angle αx of the light is larger than the Brewster angle. Thereby, all the light emitted from the lens 2 can be made incident on the third prism second surface 16b at an incident angle larger than the Brewster angle.

The conditions can also be specified as follows. When the light beam having the maximum aperture is incident from the lens 2, the maximum angle (expected angle) of the light beam with respect to the optical axis Lz is β, the Brewster angle at the second prism second surface 16 b is γ, and the third prism passes through the optical axis Lz. When the incident angle of the light incident on the second surface 16b is α3, the inclination of the third prism second surface 16b is set so as to satisfy the condition of α3> β + γ. Thereby, all the light from the lens 2 can be incident on the third prism second surface 16b at an incident angle larger than the Brewster angle. In addition, this makes it possible to prevent a light amount difference from occurring in the screen when capturing an IR image, and to capture a high-quality IR image.

Incidentally, in order to capture a high-quality IR image, it is preferable to set the inclination of the third prism second surface 16b so as to satisfy the above-described conditions.

However, when the imaging unit 1 is increased in size by setting in this way, it is possible to set the inclination of the third prism second surface 16b while allowing a light amount difference to occur under certain conditions. preferable. That is, it is preferable to allow the occurrence of a light amount difference at a level that does not significantly impair the image quality, and to set the inclination of the third prism second surface 16b.

As such a condition, for example, when a light flux having an F number of 2.0 is incident from the lens 2, the third prism 2nd so that almost all light is incident at an incident angle larger than the Brewster angle. The inclination of the surface 16b is set. Thus, for example, even when a light flux having an F number of less than 2.0 is incident, the amount of light incident at the Brewster angle can be suppressed to a slight amount, and the generated light amount difference has no practical problem. Can be suppressed to the level.

Here, the F number is defined as a value obtained by dividing the focal length of the lens by the effective aperture of the lens. The effective aperture is the diameter of the luminous flux of parallel rays incident on the lens from the point light source assuming a point light source located at infinity on the optical axis of the lens. If the F number is Fn, the focal length is f, and the effective aperture is Φ, then Fn = f / Φ.

There is a relationship of Fn = 1 / (2NA) between the F number and the image side NA (Numerical Aperture). The image side NA is defined as NA = Nsin θ using a half angle θ obtained by looking into the exit pupil from an image point on the optical axis. Where N is the refractive index of the medium around the image point, and is 1 for air. Therefore, the F number Fn has a relationship of Fn = 1 / (2Nsinθ).

As an example, consider a case where the Brewster angle γ on the second surface 16b of the third prism is about 40.18 degrees. The condition is that the refractive index n1 (incident side refractive index) of the third prism 16 is 1.8, and the refractive index n2 of the adhesive layer that joins the third prism 16 and the fourth prism 18 (on the transmission side). In this case, the refractive index is 1.52.

Assuming that the maximum angle (expected angle) β with respect to the optical axis Lz of the light beam when a light flux having an F number of 2.0 is incident from the lens 2, the third prism second surface 16b has the optical axis Lz as the optical axis Lz. The inclination may be set so that the incident angle α3 of the light passing through and incident on the second prism second surface 16b is larger than 48.16 degrees (β + γ = 7.98 + 40.18).

Since the incident angle is an angle formed by the incident ray with the normal line of the medium boundary surface at the incident point, the normal line of the third prism second surface 16b is larger than 48.16 degrees with respect to the optical axis Lz. The inclination may be set so that

[Modification of color separation optical system]
<A form in which IR light is reflected twice and extracted>
<Constitution>
In the above-described embodiment, the IR light is reflected once and extracted. However, like the B light and the R light, the IR light may be reflected and extracted twice. Thereby, the IR image can be taken out without making it a mirror image.

FIG. 4 is a diagram showing a configuration example of a color separation optical system when IR light is reflected twice and taken out.

The color separation optical system 10A of this example is different from the color separation optical system 10 of the above embodiment in that the third prism 16 and the second prism 14 are joined via the air gap 28. Hereinafter, this difference will be described.

As shown in FIG. 4, in the third prism 16 that is a prism for extracting the IR light Lir, the third prism first surface 16 a functions as a joint surface with the second prism 14. The third prism first surface 16a is joined to the second prism second surface 14b via a frame-shaped spacer 26, for example. As a result, the third prism 16 and the second prism 14 are joined via the air gap 28.

When the third prism 16 and the second prism 14 are joined via the air gap 28, the third prism first surface 16a functions as a total reflection surface. The third prism first surface 16a is set so that the IR light Lir reflected by the third prism second surface 16b is totally reflected in the direction of the third prism third surface 16c.

<Action>
The light that has passed through the lens 2 first enters the first prism first surface 12a. As for the light incident on the first prism first surface 12a, only the B light Lb is selectively reflected on the first prism second surface 12b. As a result, the B light Lb is separated from the light incident on the first prism 12.

The separated B light Lb is reflected toward the first prism first surface 12a and is incident on the first prism first surface 12a. The B light Lb incident on the first prism first surface 12a is totally reflected by the first prism first surface 12a and emitted from the first prism third surface 12c. The B light Lb emitted from the first prism third surface 12c is incident on the light receiving surface of the B light image sensor 30B via the B light trimming filter 20B.

Light of color components other than the B light Lb passes through the first prism second surface 12 b and enters the second prism first surface 14 a through the air gap 24. Of the light incident on the second prism first surface 14a, only the R light Lr is selectively reflected by the second prism second surface 14b. Thereby, the R light Lr is separated from the light incident on the second prism 14.

The separated R light Lr is reflected toward the second prism first surface 14a and is incident on the second prism first surface 14a. The R light Lr incident on the second prism first surface 14a is totally reflected by the second prism first surface 14a and emitted from the second prism third surface 14c. The R light Lr emitted from the second prism third surface 14c enters the light receiving surface of the R light image sensor 30R via the R light trimming filter 20R.

Light of color components other than the R light Lr is transmitted through the second prism second surface 14b and is incident on the third prism first surface 16a through the air gap 28. As for the light incident on the third prism first surface 16a, only the IR light Lir is selectively reflected on the third prism second surface 16b. Thereby, the IR light Lir is separated from the light incident on the third prism 16.

The separated IR light Lir is reflected toward the third prism first surface 16a and is incident on the third prism first surface 16a. The IR light Lir incident on the third prism first surface 16a is totally reflected by the third prism first surface 16a and emitted from the third prism third surface 16c. The IR light Lir emitted from the third prism third surface 16c enters the light receiving surface of the IR light image sensor 30IR via the IR light trimming filter 20IR.

Light of color components other than the IR light Lir is transmitted through the third prism second surface 16b and is incident on the fourth prism first surface 18a. The light incident on the fourth prism first surface 18a is emitted from the fourth prism second surface 18b as it is as G light Lg. The G light Lg emitted from the fourth prism second surface 18b enters the light receiving surface of the G light image sensor 30G via the G light trimming filter 20G.

As described above, the IR light Lir can be extracted without being reflected as a mirror image by reflecting the IR light Lir twice as in the case of the B light and the R light. Thereby, subsequent image processing can be simplified.

FIG. 5 is an enlarged view of circles A, B and C indicated by broken lines in FIG. 2A is an enlarged view of the circle A portion, FIG. 2B is an enlarged view of the circle B portion, and FIG. 2C is an enlarged view of the circle C portion.

Also in this example, the incident angle of light passing through the optical axis Lz among the three separation surfaces (the first prism second surface 12b, the second prism second surface 14b, and the third prism second surface 16b) is maximized. The surface is configured to be the third prism second surface 16b. Thereby, it can suppress that color shading generate | occur | produces in a color image.

<< Other color separation optical system modifications >>
<Separation order>
In the above embodiment, when the four color component lights of R light, G light, B light and IR light are separated from the incident light beam, they are separated in the order of B light, R light, IR light and G light. However, the order of separating the light of each color component is not limited to this. For example, it may be configured to separate in the order of IR light, B light, R light, and G light.

<Light to be separated (channel)>
In the above embodiment, R light, G light, and B light are separated from the incident light beam as light of three color components in the visible region. However, light separated as light of three color components in the visible region is However, the present invention is not limited to this. It can be set as appropriate according to the application.

In the above embodiment, the IR light is separated as the color component light in the invisible region. However, the light separated as the color component light in the invisible region is not limited to this. . It can be set as appropriate according to the application. For example, it can also be set as the structure which isolate | separates an ultraviolet light.

<Gapless configuration>
The color separation optical system can also be constituted by a so-called gapless prism. The gapless prism is a prism having a configuration not including an air gap. In a color separation optical system composed of gapless prisms, light is extracted from all prisms other than the first prism without being reflected only once.

Of the three separation surfaces (the first visible light separation surface, the second visible light separation surface, and the non-visible light separation surface) that are configured with a gapless prism, the surface that has the maximum incident angle of light passing through the optical axis is non-visible. It is configured to be a visible light separation surface. Thereby, it can suppress that color shading generate | occur | produces in a color image.

<Trimming filter>
In the above embodiment, the trimming filter is provided on the exit surface of each prism, but a configuration without the trimming filter is also possible. It is also possible to provide a trimming filter only for a specific exit surface.

◆◆ Camera ◆◆
[Camera configuration]
FIG. 6 is a diagram illustrating an example of the configuration of the camera.

The camera 100 is an example of an imaging device. The camera 100 according to the present embodiment is configured as a camera capable of exchanging lenses. In addition, the camera 100 of the present embodiment is configured as a camera that can capture RGB images and IR images by using the imaging unit 1.

The camera 100 includes a box-shaped housing 110, and the imaging unit 1 is accommodated in the housing 110. The imaging unit 1 is disposed at a predetermined position inside the housing 110 via a holder (not shown).

The housing 110 includes a camera-side mount 112 on the front part thereof. The camera side mount 112 is configured by a C mount. The C mount is a standard mount having an inner diameter of 24.4 mm (1 inch), a pitch of 0.794 mm (32 peaks / 1 inch), and a flange back of 17.526 mm (air conversion length). The flange back FB is the distance from the mount surface of the mount to the light receiving surface of the image sensor.

The imaging unit 1 is installed to meet the C-mount standard. Therefore, it is configured in a size that can satisfy the flange back condition in the C mount. For each of the image sensors 30R, 30B, 30G, and 30IR, an image sensor having an image size of 1 type (diagonal 16 mm) or less is used. In the present embodiment, an image sensor having an image size of 1/3 type (diagonal 6 mm) is used. Therefore, the color separation optical system 10 is configured to have a size that can satisfy the flange back condition in the C mount when a 1/3 type image sensor is used.

The imaging lens 200 is composed of a C-mount standard lens. The imaging lens 200 includes a C-mount standard lens-side mount 212 at the base end of the lens barrel 210.

[Electrical configuration of camera]
FIG. 7 is a block diagram showing the electrical configuration of the camera.

As shown in the figure, the camera 100 includes an R light image sensor driver 120R, a G light image sensor driver 120G, a B light image sensor driver 120B, an IR light image sensor driver 120IR, an R light analog signal processing unit 122R, and a G light analog. A signal processing unit 122G, a B optical analog signal processing unit 122B, an IR optical analog signal processing unit 122IR, a camera microcomputer 124, and the like are provided.

<Image sensor driver>
The R light image sensor driver 120R drives the R light image sensor 30R in response to a command from the camera microcomputer 124.

The G light image sensor driver 120G drives the G light image sensor 30G in response to a command from the camera microcomputer 124.

The B light image sensor driver 120B drives the B light image sensor 30B in response to a command from the camera microcomputer 124.

The IR light image sensor driver 120IR drives the IR light image sensor 30IR in response to a command from the camera microcomputer 124.

<< Analog signal processing section >>
The R light analog signal processing unit 122R takes in an analog image signal of R light for each pixel output from the R light image sensor 30R, and performs predetermined signal processing (for example, correlated double sampling processing, gain adjustment, etc.). The processed signal is converted into a digital signal and output. The digital image signal of the R light Lr output from the R light analog signal processing unit 122R is taken into the camera microcomputer 124.

The G light analog signal processing unit 122G takes in an analog image signal of G light for each pixel output from the G light image sensor 30G, performs predetermined signal processing, and converts the processed signal into a digital signal. Output. The digital image signal of the G light Lg output from the G light analog signal processing unit 122G is taken into the camera microcomputer 124.

The B light analog signal processing unit 122B takes in the B light analog image signal output from the B light image sensor 30B for each pixel, performs predetermined signal processing, and converts the processed signal into a digital signal. Output. The digital image signal of the B light Lb output from the B light analog signal processing unit 122B is captured by the camera microcomputer 124.

The IR light analog signal processing unit 122IR takes in an analog image signal of IR light for each pixel output from the IR light image sensor 30IR, performs predetermined signal processing, and converts the processed signal into a digital signal. Output. The digital image signal of the IR light Lir output from the IR light analog signal processing unit 122IR is taken into the camera microcomputer 124.

<Camera microcomputer>
The camera microcomputer 124 includes a microcomputer having a CPU (Central Processing Unit), a RAM (Random Access Memory), and a ROM (Read Only Memory). The camera microcomputer 124 implements various functions by executing predetermined programs. The program is stored in the ROM.

FIG. 8 is a block diagram of main functions realized by the camera microcomputer.

As shown in the figure, the camera microcomputer 124 executes a predetermined program, whereby an image sensor drive control unit 124a, an RGB image signal processing unit 124b, an IR image signal processing unit 124c, an RGB image signal output unit 124d, an IR It functions as the image signal output unit 124e and the like.

<Image sensor drive controller>
The image sensor drive control unit 124a includes the R light image sensor 30R and the G light image sensor 30G via the R light image sensor driver 120R, the G light image sensor driver 120G, the B light image sensor driver 120B, and the IR light image sensor driver 120IR. The B light image sensor 30B and the IR light image sensor 30IR are controlled to be driven.

<RGB image signal processor>
The RGB image signal processing unit 124b is configured to output the R light image signal, the B light image signal, and the G light output from the R light analog signal processing unit 122R, the G light analog signal processing unit 122G, and the B light analog signal processing unit 122B. An image signal is taken in and subjected to predetermined signal processing to generate an RGB image which is a color image.

<IR image signal processor>
The IR image signal processing unit 124c takes in the IR light image signal output from the IR light analog signal processing unit 122IR, performs predetermined signal processing, and generates an IR image.

Note that if the IR image is output as it is, it becomes a mirror image with respect to the RGB image, and is output after being subjected to a required inversion process.

<RGB image signal output unit>
The RGB image signal output unit 124 d causes the RGB image generated by the RGB image signal processing unit 124 b to be output from the RGB image signal output terminal 126.

<IR image signal output unit>
The IR image signal output unit 124e causes the IR image generated by the IR image signal processing unit 124c to be output from the IR image signal output terminal 128.

[Camera action]
The light that has passed through the imaging lens 200 is decomposed into R light, G light, B light, and IR light by the color separation optical system 10. The decomposed R light, G light, B light, and IR light are individually received by the R light image sensor 30R, the G light image sensor 30G, the B light image sensor 30B, and the IR light image sensor 30IR, respectively.

The R light image sensor 30R, the G light image sensor 30G, the B light image sensor 30B, and the IR light image sensor 30IR convert the received R light, G light, B light, and IR light into electrical signals and output them.

<< Output of RGB image >>
The electrical signals output from the R light image sensor 30R, the G light image sensor 30G, and the B light image sensor 30B are sent to the R light analog signal processing unit 122R, the G light analog signal processing unit 122G, and the B light analog signal processing unit 122B, respectively. It is captured. The R light analog signal processing unit 122R, the G light analog signal processing unit 122G, and the B light analog signal processing unit 122B perform predetermined signal processing on the captured R light, G light, and B light, and output them to the camera microcomputer 124. .

The camera microcomputer 124 applies predetermined R light image signals, B light image signals, and G light image signals captured from the R light analog signal processing unit 122R, the G light analog signal processing unit 122G, and the B light analog signal processing unit 122B. Thus, an RGB image that is a color image is generated and output from the RGB image signal output terminal 126.

For example, an RGB image monitor is connected to the RGB image signal output terminal 126. The captured RGB image is displayed on the monitor for this RGB image.

<Output IR image>
The electrical signal output from the IR light image sensor 30IR is taken into the IR light analog signal processing unit 122IR. The IR light analog signal processing unit 122IR performs predetermined signal processing on the captured IR light and outputs it to the camera microcomputer 124.

The camera microcomputer 124 performs predetermined signal processing on the IR light image signal captured from the IR light analog signal processing unit 122IR, generates an IR image, and outputs the IR image from the IR image signal output terminal 128.

For example, an IR image monitor is connected to the IR image signal output terminal 128. The captured IR image is displayed on the monitor for this IR image.

Note that it is also possible to output the IR image and the RGB image to a common monitor and switch the image to be displayed in accordance with an instruction from the user. It is also possible to display both in parallel on the same screen. Furthermore, it is possible to display both of them superimposed. This point will be described later.

[Modification of imaging device]
<Applying to a lens-integrated camera>
Although the case where the present invention is applied to an interchangeable lens camera has been described as an example in the above embodiment, the application of the present invention is not limited to this. The present invention can be similarly applied to a camera in which an imaging lens is integrally assembled with a housing.

The present invention can also be applied to an imaging apparatus configured to perform camera control, signal processing, and the like in separate units. For example, the present invention can also be applied to an imaging apparatus having a configuration in which a color separation optical system, an image sensor, and the like are incorporated in a camera head, and control and signal processing are performed by a camera control unit.

《Mount configuration》
In the above embodiment, the C mount is adopted as the mount for mounting the imaging lens, but the configuration of the mount is not limited to this. In addition, for example, a CS mount or the like can be employed. The CS mount has a C-mount flange back of 12.5 mm (air equivalent length).

It should be noted that the imaging unit can be made compact by adopting a configuration in which the IR light is reflected and extracted only once as in the imaging unit 1 of the above embodiment. Therefore, the imaging unit 1 according to the above embodiment works particularly effectively in an imaging apparatus that requires a compact imaging unit. An imaging device that is required to be compact is an imaging device having a flange back of 12.5 mm or more and 19 mm or less in terms of air, as in an imaging device that employs a C mount or CS mount.

<< Other Embodiments of Imaging Device >>
The imaging device can also be configured as an electronic endoscope, for example.

FIG. 9 is a diagram illustrating an example of an electronic endoscope.

The electronic endoscope 300 shown in the figure is a so-called rigid endoscope, and is configured as an electronic endoscope capable of capturing RGB images and IR images. The electronic endoscope 300 mainly includes a scope 310, a mount adapter 320, and a camera body 330.

Scope 310 is an insertion part into a body cavity. The scope 310 includes an observation window at the tip. The scope 310 includes a plurality of lens groups inside. The scope 310 forms an optical image of a subject observed from the observation window by a plurality of lens groups provided inside.

The mount adapter 320 is a member for attaching the scope 310 to the camera body 330. The mount adapter 320 includes a scope mounting unit at one end and a camera mounting unit at the other end. The scope mounting portion is a mounting portion of the scope 310, and the scope 310 is detachably mounted. The camera mounting part is a mounting part to the camera body 330. The camera mounting unit is configured by a mount corresponding to the mount provided in the camera body 330.

The camera body 330 has a housing 330a that can be grasped by a user's hand, and the imaging unit 1 is provided inside the housing 330a. The electrical configuration of the camera body 330 is substantially the same as the camera 100 of the above embodiment.

The housing 330 a is provided with a mount 332, and a mount adapter 320 is detachably attached to the mount 332. The mount 332 is constituted by a C mount, for example.

In surgery using an endoscope, a fluorescent substance, ICG (Indocyanine Green / Indocyanine Green), is administered into the body, and near-infrared light is applied to a site such as an excessively accumulated tumor to illuminate the affected area. The part to be included may be imaged. ICG is a substance that emits fluorescence with near-infrared light having a longer wavelength (for example, peak wavelength 835 nm) when excited with near-infrared light (for example, peak wavelength 805 nm, 750 to 810 nm).

According to the electronic endoscope 300 of this example, ICG is administered into the body, a near-infrared light is applied to a site (affected part) such as a tumor that has accumulated excessively, and the affected part is imaged, whereby a color image of the affected part is obtained. Simultaneously with the (RGB image), it is possible to capture an image (fluorescent image) in which the affected area is fluorescently emitted.

In this example, the case where ICG is administered as an optical contrast agent has been described as an example, but an optical contrast agent other than ICG may be administered. In this case, the spectral characteristic of the invisible light separation surface is set according to the wavelength of the excitation light for exciting the optical contrast agent.

In this example, a chemical that emits fluorescence in the wavelength region of infrared light is used. However, a chemical that emits fluorescence in the wavelength region of ultraviolet light may be used. In this case, the spectral characteristics are set so that the ultraviolet light is separated on the non-visible light separation surface.

<< Other examples of image output forms >>
According to the camera (imaging device) of the above embodiment, RGB images and IR images can be simultaneously captured on the same axis. The two images have no parallax and match with high accuracy. Therefore, both can be displayed in a superimposed manner.

FIG. 10 is a block diagram showing a schematic configuration of a display processing apparatus when displaying an RGB image and an IR image in a superimposed manner.

The display processing device 130 includes an image composition processing unit 130a and an image display control unit 130b. The display processing device 130 is configured by a computer. That is, the computer functions as the display processing device 130 by executing a predetermined program.

The image composition processing unit 130a acquires the RGB image signal and the IR image signal from the imaging device, and generates a composite image in which both are superimposed. The synthesis process is performed as follows, for example. First, the signal value of each pixel of the acquired RGB image signal and IR image signal is multiplied by a predetermined coefficient. Here, the signal value of each pixel of the RGB image signal is multiplied by the coefficient K1, and the signal value of each pixel of the IR image signal is multiplied by the coefficient K2. Next, the signal value of each pixel of the IR image signal after coefficient multiplication is added to the signal value of each pixel of the RGB image signal after coefficient multiplication. Addition is performed between corresponding pixels. Thereby, a composite image in which the RGB image and the IR image are superimposed is generated.

The reason why the RGB image signal and the IR image signal are multiplied by a coefficient is to prevent the signal value of each pixel after the addition from being saturated. Therefore, the coefficient K1 and the coefficient K2 are set to values that satisfy the relationship of K1 + K2 = 1. For example, K1 = 0.5 and K2 = 0.5 are set.

The image display control unit 130 b controls display of an image on the display device 134 based on the operation of the operation unit 132.

FIG. 11 is a diagram illustrating an example of display of an RGB image, an IR image, and a composite image. This figure shows an example of display of an electronic endoscope as an imaging apparatus. In particular, a display example of an image captured when ICG is administered into the body and near-infrared light is applied to the affected area to image the affected area is shown. In this case, a color image (RGB image) of the affected area and a fluorescent image (IR image) of the affected area are captured.

FIG. 11A shows an example of a color image (RGB image) of an affected area. FIG. 11B shows an example of a fluorescent image (IR image) of the affected area. FIG. 11C shows an example of a composite image.

The color image (RGB image) of the affected area shown in FIG. 11A and the fluorescence image (IR image) of the affected area shown in FIG. 11B are images without parallax. Therefore, the composite image illustrated in FIG. 11C is an image obtained by capturing the same part on the same axis. By displaying the composite image, it is possible to grasp at a glance where in the color image (RGB image) the light emitting portion in the fluorescence image (IR image) is present.

Display of RGB image, IR image, and composite image is switched by operation of the operation unit 132. The image display control unit 130 b switches display of an image on the display device 134 based on the operation of the operation unit 132.

In the example shown in FIG. 11, the RGB image, the IR image, and the composite image are each displayed independently, but can be displayed in combination. For example, three images can be simultaneously displayed on one screen. Also, two images arbitrarily combined on one screen can be displayed in parallel. For example, an RGB image and an IR image can be displayed in parallel.

In this example, the display processing device 130 is provided separately from the imaging device, but the function of the display processing device 130 may be incorporated into the imaging device.

Further, the display processing device 130 may have a function of performing signal processing on the RGB image and the IR image as necessary. For example, a function of performing processing for enhancing an outline of an RGB image, processing for coloring an IR image green or the like, processing for extracting a specific region, and the like may be provided.

As described above, the Brewster angle γ is obtained from the refractive index n1 of the incident-side substance and the refractive index n2 of the transmissive-side substance by the formula γ = Arctan (n2 / n1).

In the color separation optical system 10 having the configuration shown in FIG. 1, the relationship between the refractive index n1 (refractive index on the incident side) of the third prism 16 and the Brewster angle γ was determined. In addition, in each refractive index condition, when an F2.0 light beam and an F4.0 light beam were incident, a condition for entering the light beam while avoiding the Brewster angle was obtained. The condition for entering the incident light beam while avoiding the Brewster angle is defined as the condition of the incident angle α3 of the light passing through the optical axis Lz to the third prism second surface 16b, and as described above, α3 > Β + γ. When the maximum angle (expected angle) with respect to the optical axis Lz of the light beam when an F2.0 light beam is incident from the lens is βF2, the third prism second surface 16b is set to satisfy α3> βF2 + γ. If the maximum angle (expected angle) of the light beam with respect to the optical axis Lz when the F4.0 light beam is incident from the lens is βF4, the third prism second surface 16b is set to satisfy α3> βF4 + γ. .

FIG. 12 is a table showing the relationship between the refractive index n1 of the third prism, the Brewster angle γ determined from the refractive index n1, and the condition of the incident angle that should be satisfied by the second surface of the third prism.

The refractive index n1 of the third prism 16 is set to n1 = 1.65, 1.7, 1.8, 1.9, and 2. This is a refractive index value that can be taken as an example of the optical glass that is the material of the prism, and the maximum is 2.0. Note that the refractive index n2 of the adhesive layer (the refractive index of the material on the transmission side) is uniformly 1.52.

As shown in the table of FIG. 12, the Brewster angle γ increases as the refractive index n1 of the third prism increases.

Further, as shown in the table, βF2 + γ> βF4 + γ is always satisfied. Therefore, if the incident angle α3 of the second prism second surface 16b is set to avoid the Brewster angle γ for the light flux of F2.0, F4.0. This light beam can also be incident while avoiding the Brewster angle γ.

Note that the incident angle α3 of the third prism second surface 16b, which is a non-visible light separation surface, is incident on the first prism second surface 12b and the second prism second surface 14b, which are visible light separation surfaces. The condition is that the angles are larger than α1 and α2 (α3> α1 and α3> α2). Therefore, considering this point and considering compactness, it is preferable to set the incident angle α3 of the third prism second surface 16b to 47 degrees or more.

1 imaging unit 2 lens 10 color separation optical system 10A color separation optical system 12 first prism 12a first prism first surface 12b first prism second surface 12c first prism third surface 14 second prism 14a second prism first Surface 14b Second prism second surface 14c Second prism third surface 16 Third prism 16a Third prism first surface 16b Third prism second surface 16c Third prism third surface 18 Fourth prism 18a Fourth prism first Surface 18b Fourth prism second surface 18c Fourth prism third surface 20B B light trimming filter 20G G light trimming filter 20IR IR light trimming filter 20R R light trimming filter 22 Spacer 24 Air gap 26 Spacer 28 Air gap 30R R light image sensor 30G G light image sensor 30B B light image Sensor 30IR IR light image sensor 100 Camera 110 Housing 112 Camera side mount 120B B light image sensor driver 120G G light image sensor driver 120IR IR light image sensor driver 120R R light image sensor driver 122B B light analog signal processing unit 122G G light analog Signal processor 122IR IR optical analog signal processor 122R R optical analog signal processor 124 Camera microcomputer 124a Image sensor drive controller 124b RGB image signal processor 124c IR image signal processor 124d RGB image signal output unit 124e IR image signal output unit 126 RGB image signal output terminal 128 IR image signal output terminal 130 Display processing device 130a Image composition processing unit 130b Image display control unit 132 Operation unit 134 Display device 200 Imaging lens 210 Lens barrel 212 Lens side mount 300 Electronic endoscope 310 Scope 320 Mount adapter 330 Camera body 330a Case 332 Mount FB Flange back Lr R light Lg G light Lb B light Lir IR light Lz Optical axis α1 First prism first Incident angle to the second surface α2 Incident angle to the second prism second surface α3 Incident angle to the third prism second surface αx Incident angle to the third prism second surface

Claims (11)

1. A color separation optical system that separates an incident light beam into light of three color components in the visible region and light of one color component in the invisible region,
   A first visible light separation surface that reflects and separates light of the first color component in the visible region;
   A second visible light separation surface that reflects and separates light of the second color component in the visible region;
   A non-visible light separating surface that reflects and separates light in the non-visible region;
   On the optical axis,
   Of the first visible light separating surface, the second visible light separating surface, and the invisible light separating surface, the surface having the maximum incident angle of light passing through the optical axis is the invisible light separating surface.
   Color separation optical system.
2. The non-visible light separating surface is disposed so as to be inclined at an angle at which all light is incident at an incident angle larger than the Brewster angle when a light flux having an F number of 2.0 is incident from the lens.
   The color separation optical system according to claim 1.
3. The non-visible light separating surface is disposed so as to be inclined at an angle at which all light is incident at an incident angle larger than the Brewster angle when a light beam having a maximum aperture is incident from a lens.
   The color separation optical system according to claim 1.
4. A first visible light reflecting surface that reflects in the direction of emitting light of the first color component in the visible region separated by the first visible light separating surface;
   A second visible light reflecting surface that reflects in the direction of emitting light of the second color component in the visible region separated by the second visible light separating surface;
   The color separation optical system according to any one of claims 1 to 3, further comprising:
5. The first visible light separation surface, the second visible light separation surface, and the non-visible light separation surface are the first visible light separation surface, the second visible light separation surface, and the invisible light separation surface from the incident side. Arranged in order,
   The color separation optical system according to any one of claims 1 to 4.
6. A first incident surface on which a light beam from a lens is incident, the first visible light separating surface, and a first emitting surface that emits light of a first color component in a visible region separated by the first visible light separating surface; A first prism having
   The second visible light separation surface is joined to the first visible light separation surface and is separated by the second visible light separation surface, the second visible light separation surface, and the second visible light separation surface. A second prism having a second emission surface that emits the light of the second color component in the visible region,
   A third incident surface that is joined to the second visible light separation surface and receives a light beam that has passed through the second visible light separation surface, the non-visible light separation surface, and a non-visible light separated surface. A third prism having a third exit surface that emits light in the visible region;
   A fourth incident surface that is joined to the non-visible light separation surface and receives a light beam that has passed through the non-visible light separation surface; and a fourth emission surface that emits light of a third color component in the visible region. A fourth prism;
   The color separation optical system according to any one of claims 1 to 3, further comprising:
7. The first prism causes the first color component light in the visible region separated by the first visible light separation surface to be totally reflected by the first incident surface and emitted from the first emission surface,
   In the second prism, the second incident surface is joined to the first visible light separation surface via an air gap, and the second color component light in the visible region separated by the second visible light separation surface is transmitted to the second prism. 2 total reflection on the entrance surface, exit from the second exit surface,
   The color separation optical system according to claim 6.
8. The invisible light separation surface separates infrared light;
   The color separation optical system according to any one of claims 1 to 7.
9. The color separation optical system according to any one of claims 1 to 8,
   A first visible light image sensor that receives light of a first color component in the visible region separated by the color separation optical system;
   A second visible light image sensor that receives light of a second color component in the visible region resolved by the color separation optical system;
   A third visible light image sensor that receives light of a third color component in the visible region resolved by the color separation optical system;
   A non-visible light image sensor that receives light in a non-visible region separated by the color separation optical system;
   An imaging unit comprising
10. A housing,
    The imaging unit according to claim 9 housed in the housing;
    A mount provided in the housing, on which a lens is detachably mounted;
    An imaging apparatus comprising:
11. The flange back is 12.5 mm or more and 19 mm or less in terms of air.
    The imaging device according to claim 10.

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