JP2009075543A - Color separation optical system and imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce ghost/flare and also to obtain characteristics closer to ideal spectral characteristics so as to improve color reproductivity, compared to an existing wave-length selection method using a trimming filter with a dichroic film. <P>SOLUTION: A curve representing characteristics of a blue-light reflecting dichroic film DB and a curve representing characteristics of a red-light reflecting dichroic film DR are configured to have shapes close to ideal spectral characteristics of green. Accordingly, the characteristics approximated to the ideal spectral characteristics can be obtained without using a trimming filter having a dichroic film in an exiting surface of a prism. Since the trimming filter having the dichroic film is not required, the ghost/flare occurred due to the dichroic film of the trimming filter can be suppressed. Hereby, the imaging system having the ideal spectral characteristic with reduced ghost and flare can be embodied. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a color separation optical system that separates incident light into a plurality of color lights, and an imaging device that includes the color separation optical system.

  In general, an imaging apparatus such as a television camera or a video camera is provided with a color separation optical system. FIG. 43 shows a configuration example of a conventional color separation optical system. The color separation optical system 101 separates incident light L incident through the photographing lens 102 into three color light components of blue light LB, red light LR, and green light LG. Image pickup devices 4B, 4R, and 4G for each color light such as a CCD (Charge Coupled Device) are arranged at positions corresponding to the respective color lights separated by the color separation optical system 101. The color separation optical system 101 is called a Philips type color separation optical system, and in order from the light incident side along the optical axis Z1, the first prism 110, the second prism 120, and the third prism The first prism 110 extracts blue light LB, the second prism 120 extracts red light LR, and the third prism 130 extracts green light LG.

  A blue light reflecting dichroic film DB1 is formed on the reflection / transmission surface 111 of the first prism 110. On the reflection / transmission surface 121 of the second prism 120, a red light reflection dichroic film DR1 is formed. A trimming filter 151 is provided on the light exit surface of the first prism 110. A dichroic film 151 </ b> A is formed on the light exit surface of the trimming filter 151. Similarly, a trimming filter 152 formed with a dichroic film 152A is provided on the light exit surface of the second prism 120, and a trimming filter 153 formed with a dichroic film 153A is formed on the light exit surface of the third prism 130. Is provided. The trimming filters 151, 152, and 153 are provided to bring the spectral characteristics closer to the ideal characteristics, and spectral components of wavelength components that cannot be sufficiently shaped by the blue light reflecting dichroic film DB1 and the red light reflecting dichroic film DR1. Has the role of adjusting characteristics.

  FIG. 45 shows spectral characteristics that are generally ideal in a color imaging system for three colors of a red (R) component, a blue (B) component, and a green (G) component. Note that the ideal characteristics of FIG. 45 are normalized so that the maximum value of each color light component is 1, and the vertical axis indicates the transmittance intensity. This “ideal characteristic” is converted from the chromaticity coordinates of the three primary colors of the color reproduction medium, and can be obtained by primary conversion of the color matching function of the XYZ color system. Here, the “color reproduction medium” reproduces (displays) an image taken by the imaging device, and is a display device such as a liquid crystal monitor or a projector. FIG. 44 shows an example of chromaticity coordinates of the three primary colors R, G, and B for obtaining ideal characteristics. The three primary colors R, G, and B determine the color range that can be reproduced by the color reproduction medium.

  If the same characteristic as the ideal characteristic shown in FIG. 45 is obtained using the color separation optical system 101 shown in FIG. 43, ideal color reproduction can be performed. However, in practice, it is difficult to achieve the same characteristic as the ideal characteristic, and the design is such that the characteristic approximates the ideal characteristic. In the conventional color separation optical system 101, ideal characteristics are obtained by appropriately adjusting the dichroic films DB1 and DR1 formed on each prism and the dichroic films 151A, 152A, and 153A formed on the trimming filters 151, 152, and 153. It was designed to have approximate characteristics. FIG. 46 shows spectral transmission characteristics of a conventional general color separation optical system obtained by performing such a design.

  FIG. 47 shows a design example of the dichroic films DB1 and DR1 used in the conventional color separation optical system 101. As shown in FIG. 47, conventionally, as the dichroic films DB1 and DR1, the characteristic curve of wavelength vs. transmittance shows a sharp rise or fall compared to the ideal characteristic curve shown in FIG. Something with was used. Further, unnecessary wavelength components of light emitted from the exit surface of each prism are blocked using trimming filters 151, 152, 153 provided with dichroic films 151A, 152A, 153A.

As described above, conventionally, the characteristics are usually adjusted using various trimming filters. For example, Patent Document 1 proposes a method for improving the color reproduction by increasing the skin tone luminance level by using a trimming filter having special spectral transmission characteristics. In addition, instead of the dichroic film DR1, a half mirror is disposed on the joint surface between the second prism 120 and the third prism 130, and a dichroic film having transmission characteristics approximate to ideal characteristics is used as the trimming filters 152 and 153. A method of adjusting the transmission characteristics by applying such a method is known. FIG. 48 shows the spectral characteristics of a conventional color separation optical system approximated to ideal characteristics by performing such special adjustment.
JP-A-2005-208256

  However, in a conventional color separation optical system that uses a trimming filter with a dichroic film on the exit surface of the prism, the dichroic film has a wavelength range with high reflectivity as a characteristic of the dichroic film. There is a problem that multiple reflection occurs between the imaging surface and a ghost or flare, resulting in a deterioration in image quality. FIG. 49 shows, as an example, multiple reflection that occurs on the exit surface side of the third prism 130 that extracts the green light LG in the conventional color separation optical system 101. As shown in FIG. 49, the imaging device 4G includes an imaging surface 401G, a cover glass 402, and an extraction electrode 403. For example, part of the green light LG that has passed through the green trimming filter 153 is captured on the imaging surface 401G. The reflected light is reflected according to the wavelength selection characteristics of the dichroic film 153A of the trimming filter 153. In this way, multiple reflected light 160 is generated, resulting in ghost / flare. For this reason, conventionally, it has been difficult to realize an imaging system having ideal spectral characteristics with reduced ghost and flare.

  The present invention has been made in view of such a problem, and an object of the present invention is to reduce ghost and flare as compared with a conventional wavelength selection method using a trimming filter with a dichroic film, and to realize an ideal spectroscopic method. An object of the present invention is to provide a color separation optical system and an image pickup apparatus capable of obtaining characteristics close to characteristics and improving color reproducibility.

  A color separation optical system according to a first aspect of the present invention is a color separation optical system that decomposes incident light into at least three color light components of blue light, red light, and green light, sequentially from the light incident side. A first prism that has a first dichroic film and extracts a first color light component reflected by the first dichroic film; and a second dichroic film that passes through the first dichroic film and passes through the first dichroic film. At least a second prism for extracting the second color light component reflected by the second dichroic film, and a third prism for extracting the third color light component transmitted through the first and second dichroic films, The dichroic film is configured to reflect blue light as the first color light component, and the second dichroic film reflects red light or green light as the second color light component. Are those configured. In addition, the slope of the transmission characteristic curve indicating the transmittance with respect to the wavelength of the first dichroic film has a shape along the characteristic curve on the short wavelength side of the ideal green spectral characteristic, and the second dichroic film is red light. The slope of the transmission characteristic curve indicating the transmittance with respect to the wavelength of the dichroic film has a shape along the characteristic curve on the long wavelength side of the ideal green spectral characteristic, and the second dichroic film When the film reflects green light, the slope of the reflection characteristic curve indicating the reflectance with respect to the wavelength of the dichroic film has a shape that follows the characteristic curve on the long wavelength side of the ideal green spectral characteristic. It is what.

In the color separation optical system according to the first aspect of the present invention, the first dichroic film has a film configuration that reflects blue light as the first color light component, and blue light is extracted by the first prism. The second dichroic film has a film configuration that reflects red light or green light as the second color light component, and red light or green light is extracted by the second prism. From the third prism, a third color light component (color light different from the first color light component and the second color light component) transmitted through the first and second dichroic films is extracted.
In this case, the curve indicating the characteristic of the first dichroic film and the curve indicating the characteristic of the second dichroic film have a shape along the characteristic curve of the ideal green spectral characteristic. A characteristic close to ideal spectral characteristics can be obtained without using a trimming filter with a dichroic film on the exit surface. Since it is not necessary to use a trimming filter with a dichroic film, it is possible to suppress the occurrence of ghosts and flares conventionally caused by the dichroic film of the trimming filter. Thus, it is possible to realize an imaging system having ideal spectral characteristics with reduced ghost and flare.

  In the color separation optical system according to the first aspect of the present invention, when the first prism extracts blue light, the second prism extracts red light, and the third prism extracts green light, The dichroic film reflects blue light, and the slope of the transmission characteristic curve of the dichroic film is within the wavelength range of 430 nm to 670 nm in the form of the characteristic curve on the short wavelength side of the ideal green spectral characteristic. It is preferable to have a shape that changes from low transmittance to high transmittance. In addition, the second dichroic film reflects red light, and the slope of the transmission characteristic curve of the dichroic film is 430 nm or more and 670 nm or less in the form of the characteristic curve on the long wavelength side of the ideal green spectral characteristic. It is preferable to have a shape that changes from a high transmittance to a low transmittance within the wavelength range.

  In the case where the first prism extracts blue light, the second prism extracts red light, and the third prism extracts green light, the first prism has a third dichroic film, and the second prism and third A fourth prism that is disposed between the first and second prisms and extracts the fourth color light component transmitted through the first and second dichroic films may be further provided. In this case, the third dichroic film reflects a part of light in the wavelength region of 400 nm or more and 600 nm or less as the fourth color light component, and the third prism uses the first and second dichroic films. It is preferable that the green light that passes through and further passes through the third dichroic film is extracted.

  Further, in the color separation optical system according to the first aspect of the present invention, when the first prism extracts blue light, the second prism extracts green light, and the third prism extracts red light, The dichroic film 1 reflects blue light, and the slope of the transmission characteristic curve of the dichroic film is in the wavelength range of 430 nm to 670 nm in a form that follows the characteristic curve on the short wavelength side of the ideal green spectral characteristic. It is preferable to have a shape that changes from a low transmittance to a high transmittance. In addition, the second dichroic film reflects green light, and the slope of the reflection characteristic curve of the dichroic film is 430 nm or more and 670 nm or less in the form of the characteristic curve on the long wavelength side of the ideal green spectral characteristic. It is preferable to have a shape that changes from a high reflectance to a low reflectance within a wavelength range of.

  A color separation optical system according to a second aspect of the present invention is a color separation optical system that decomposes incident light into at least three color light components of blue light, red light, and green light, and sequentially from the light incident side. A first prism that has a first dichroic film and extracts a first color light component reflected by the first dichroic film; and a second dichroic film that passes through the first dichroic film and passes through the first dichroic film. At least a second prism for extracting the second color light component reflected by the second dichroic film, and a third prism for extracting the third color light component transmitted through the first and second dichroic films, The dichroic film is configured to reflect red light as the first color light component, and the second dichroic film reflects blue light or green light as the second color light component. Are those configured. In addition, the slope of the transmission characteristic curve indicating the transmittance with respect to the wavelength of the first dichroic film has a shape along the characteristic curve on the long wavelength side of the ideal green spectral characteristic, and the second dichroic film is blue light. The slope of the transmission characteristic curve indicating the transmittance with respect to the wavelength of the dichroic film has a shape along the characteristic curve on the short wavelength side of the ideal green spectral characteristic, and the second dichroic film When the film reflects green light, the slope of the reflection characteristic curve indicating the reflectivity with respect to the wavelength of the dichroic film has a shape along the characteristic curve on the short wavelength side of the ideal green spectral characteristic. It is what.

In the color separation optical system according to the second aspect of the present invention, the first dichroic film has a film configuration that reflects red light as the first color light component, and red light is extracted by the first prism. The second dichroic film has a film configuration that reflects blue light or green light as the second color light component, and blue light or green light is extracted by the second prism. From the third prism, a third color light component (color light different from the first color light component and the second color light component) transmitted through the first and second dichroic films is extracted.
In this case, the curve indicating the characteristic of the first dichroic film and the curve indicating the characteristic of the second dichroic film have a shape along the characteristic curve of the ideal green spectral characteristic. A characteristic close to ideal spectral characteristics can be obtained without using a trimming filter with a dichroic film on the exit surface. Since it is not necessary to use a trimming filter with a dichroic film, it is possible to suppress the occurrence of ghosts and flares conventionally caused by the dichroic film of the trimming filter. Thus, it is possible to realize an imaging system having ideal spectral characteristics with reduced ghost and flare.

  Further, in the color separation optical system according to the second aspect of the present invention, when the first prism extracts red light, the second prism extracts blue light, and the third prism extracts green light, The dichroic film 1 reflects red light, and the slope of the transmission characteristic curve of the dichroic film is in the wavelength range of 430 nm to 670 nm in a form that follows the characteristic curve on the long wavelength side of the ideal green spectral characteristic. It is preferable to have a shape that changes from high transmittance to low transmittance. Further, the second dichroic film reflects blue light, and the slope of the transmission characteristic curve of the dichroic film is 430 nm or more and 670 nm or less in a form along the characteristic curve on the short wavelength side of the ideal green spectral characteristic. It is preferable to have a shape that changes from a low transmittance to a high transmittance within the wavelength range.

  In the color separation optical system according to the second aspect of the present invention, when the first prism extracts red light, the second prism extracts green light, and the third prism extracts blue light, The dichroic film 1 reflects red light, and the slope of the transmission characteristic curve of the dichroic film is in the wavelength range of 430 nm to 670 nm in a form that follows the characteristic curve on the long wavelength side of the ideal green spectral characteristic. It is preferable to have a shape that changes from high transmittance to low transmittance. In addition, the second dichroic film reflects green light, and the slope of the reflection characteristic curve of the dichroic film is 430 nm or more and 670 nm or less in a form along the characteristic curve on the short wavelength side of the ideal green spectral characteristic. It is preferable to have a shape that changes from a low reflectance to a high reflectance within the wavelength range.

  A color separation optical system according to a third aspect of the present invention is a color separation optical system that decomposes incident light into at least three color light components of green light, blue light, and red light, and sequentially from the light incident side. A first prism that has a first dichroic film and extracts a first color light component reflected by the first dichroic film; and a second dichroic film that passes through the first dichroic film and passes through the first dichroic film. At least a second prism for extracting the second color light component reflected by the second dichroic film, and a third prism for extracting the third color light component transmitted through the first and second dichroic films, The dichroic film is configured to reflect green light as the first color light component, and the second dichroic film reflects blue light or red light as the second color light component. Are those configured. In addition, the slope of the reflection characteristic curve indicating the reflectivity with respect to the wavelength of the first dichroic film has a shape along the characteristic curve on the short wavelength side and the long wavelength side of the ideal green spectral characteristic. .

In the color separation optical system according to the third aspect of the present invention, the first dichroic film has a film configuration that reflects green light as the first color light component, and the first prism extracts green light. Further, the second dichroic film has a film configuration that reflects blue light or red light as the second color light component, and blue light or red light is extracted by the second prism. From the third prism, a third color light component (color light different from the first color light component and the second color light component) transmitted through the first and second dichroic films is extracted.
In this case, the trimming filter with the dichroic film is used on the exit surface of the prism because the curve indicating the characteristic of the first dichroic film has a shape that follows the characteristic curve of the ideal green spectral characteristic. Therefore, characteristics close to ideal spectral characteristics can be obtained. Since it is not necessary to use a trimming filter with a dichroic film, it is possible to suppress the occurrence of ghosts and flares conventionally caused by the dichroic film of the trimming filter. Thus, it is possible to realize an imaging system having ideal spectral characteristics with reduced ghost and flare.

  In the color separation optical system according to the third aspect of the present invention, in the portion where the slope of the reflection characteristic curve of the first dichroic film rises within the wavelength range of 430 nm or more and 670 nm or less, the ideal green spectral characteristic is short. A shape that changes from a low reflectance to a high reflectance along the characteristic curve on the wavelength side, and in the portion that falls within the wavelength range of 430 nm to 670 nm, the long wavelength side of the ideal green spectral characteristic It is preferable to have a shape that changes from a high reflectance to a low reflectance along the characteristic curve.

  In the color separation optical system according to the third aspect of the present invention, when the first prism extracts green light, the second prism extracts blue light, and the third prism extracts red light, The second dichroic film is configured to reflect blue light, and the slope of the transmission characteristic curve indicating the transmittance with respect to the wavelength of the dichroic film has a shape that follows the characteristic curve on the short wavelength side of the ideal red spectral characteristic. It is preferable to have.

  In the color separation optical system according to the third aspect of the present invention, when the first prism extracts green light, the second prism extracts red light, and the third prism extracts blue light, The second dichroic film is configured to reflect red light, and the slope of the reflection characteristic curve indicating the reflectance with respect to the wavelength of the dichroic film has a shape along the characteristic curve on the short wavelength side of the ideal red spectral characteristic. It is preferable to have.

Here, in the color separation optical system according to the first to third aspects of the present invention, the “ideal spectral characteristic” is an ideal characteristic represented by a color matching function of an RGB color system, for example. Alternatively, it may be an ideal characteristic converted from the chromaticity coordinates of the three primary colors of the color reproduction medium and indicated by the primary conversion of the color matching function of the XYZ color system.
Even if the ideal characteristics indicated by these color matching functions or the ideal characteristics indicated by the primary conversion of the color matching functions are subjected to conversion that can be inversely converted to further reduce negative values. good.

In the color separation optical system according to the first to third aspects of the present invention, the color separation optical system is disposed on at least one of the front side of the first prism or the exit surface side of the prism that extracts red light, and approximates the visibility. An absorption filter having characteristics may be further provided. Further, a coat type infrared cut filter that is disposed in front of the first prism and cuts infrared light may be further provided. Further, an ultraviolet cut filter that is disposed in front of the first prism and blocks ultraviolet light may be further provided. Moreover, you may further provide the depolarizing plate which arrange | positions ahead of the 1st prism and cancels the polarization | polarized-light in the specific direction of incident light. Further, an absorption filter that is disposed on the exit surface side of the prism that extracts red light, blocks blue light and green light, and transmits red light may be further provided.
As a result, it becomes easier to obtain characteristics close to ideal spectral characteristics.

  Further, an antireflection film may be provided on the exit surface of at least one prism. This is advantageous in reducing ghost and flare.

  A color separation optical system according to a fourth aspect of the present invention is a color separation optical system that decomposes incident light into at least three color light components of blue light, red light, and green light, and sequentially from the light incident side. A first prism that has a first dichroic film and extracts a first color light component reflected by the first dichroic film; and a second dichroic film that passes through the first dichroic film and passes through the first dichroic film. At least a second prism for extracting the second color light component reflected by the second dichroic film, and a third prism for extracting the third color light component transmitted through the first and second dichroic films, The dichroic film is configured to reflect blue light as the first color light component, and the second dichroic film reflects red light or green light as the second color light component. Are those configured. In addition, the slope of the transmission characteristic curve indicating the transmittance with respect to the wavelength of the first dichroic film has a shape substantially equal to the characteristic curve on the short wavelength side of the ideal green spectral characteristic, and the second dichroic film is red. When reflecting light, the slope of the transmission characteristic curve indicating the transmittance with respect to the wavelength of the dichroic film has a shape substantially equal to the characteristic curve on the long wavelength side of the ideal green spectral characteristic, and the second When the dichroic film reflects green light, the slope of the reflection characteristic curve indicating the reflectance with respect to the wavelength of the dichroic film has a shape approximately equal to the characteristic curve on the long wavelength side of the ideal green spectral characteristic. It is what you have.

In the color separation optical system according to the fourth aspect of the present invention, the first dichroic film has a film configuration that reflects blue light as the first color light component, and blue light is extracted by the first prism. The second dichroic film has a film configuration that reflects red light or green light as the second color light component, and red light or green light is extracted by the second prism. From the third prism, a third color light component (color light different from the first color light component and the second color light component) transmitted through the first and second dichroic films is extracted.
In this case, the curve indicating the characteristic of the first dichroic film and the curve indicating the characteristic of the second dichroic film have a shape substantially equal to the characteristic curve of the ideal green spectral characteristic. A characteristic close to the ideal spectral characteristic can be obtained without using a trimming filter with a dichroic film on the exit surface of the prism. Since it is not necessary to use a trimming filter with a dichroic film, it is possible to suppress the occurrence of ghosts and flares conventionally caused by the dichroic film of the trimming filter. Thus, it is possible to realize an imaging system having ideal spectral characteristics with reduced ghost and flare.

  A color separation optical system according to a fifth aspect of the present invention is a color separation optical system that decomposes incident light into at least three color light components of blue light, red light, and green light, and sequentially from the light incident side. A first prism that has a first dichroic film and extracts a first color light component reflected by the first dichroic film; and a second dichroic film that passes through the first dichroic film and passes through the first dichroic film. At least a second prism for extracting the second color light component reflected by the second dichroic film, and a third prism for extracting the third color light component transmitted through the first and second dichroic films, The dichroic film is configured to reflect red light as the first color light component, and the second dichroic film reflects blue light or green light as the second color light component. Are those configured. The slope of the transmission characteristic curve indicating the transmittance with respect to the wavelength of the first dichroic film has a shape substantially equal to the characteristic curve on the long wavelength side of the ideal green spectral characteristic, and the second dichroic film is blue. When reflecting light, the slope of the transmission characteristic curve indicating the transmittance with respect to the wavelength of the dichroic film has a shape approximately equal to the characteristic curve on the short wavelength side of the ideal green spectral characteristic, and the second When the dichroic film reflects green light, the slope of the reflection characteristic curve indicating the reflectance with respect to the wavelength of the dichroic film has a shape approximately equal to the characteristic curve on the short wavelength side of the ideal green spectral characteristic. It is what you have.

In the color separation optical system according to the fifth aspect of the present invention, the first dichroic film has a film configuration that reflects red light as the first color light component, and the first prism extracts red light. The second dichroic film has a film configuration that reflects blue light or green light as the second color light component, and blue light or green light is extracted by the second prism. From the third prism, a third color light component (color light different from the first color light component and the second color light component) transmitted through the first and second dichroic films is extracted.
In this case, the curve indicating the characteristic of the first dichroic film and the curve indicating the characteristic of the second dichroic film have a shape substantially equal to the characteristic curve of the ideal green spectral characteristic. A characteristic close to the ideal spectral characteristic can be obtained without using a trimming filter with a dichroic film on the exit surface of the prism. Since it is not necessary to use a trimming filter with a dichroic film, it is possible to suppress the occurrence of ghosts and flares conventionally caused by the dichroic film of the trimming filter. Thus, it is possible to realize an imaging system having ideal spectral characteristics with reduced ghost and flare.

  A color separation optical system according to a sixth aspect of the present invention is a color separation optical system that separates incident light into at least three color light components of green light, blue light, and red light, in order from the light incident side. A first prism that has a first dichroic film and extracts a first color light component reflected by the first dichroic film; and a second dichroic film that passes through the first dichroic film and passes through the first dichroic film. At least a second prism for extracting the second color light component reflected by the second dichroic film, and a third prism for extracting the third color light component transmitted through the first and second dichroic films, The dichroic film is configured to reflect green light as the first color light component, and the second dichroic film reflects blue light or red light as the second color light component. Are those configured. In addition, the slope of the reflection characteristic curve indicating the reflectance with respect to the wavelength of the first dichroic film has a shape substantially equal to the characteristic curve on the short wavelength side and the long wavelength side of the ideal green spectral characteristic. is there.

In the color separation optical system according to the sixth aspect of the present invention, the first dichroic film has a film configuration that reflects green light as the first color light component, and the first prism extracts green light. Further, the second dichroic film has a film configuration that reflects blue light or red light as the second color light component, and blue light or red light is extracted by the second prism. From the third prism, a third color light component (color light different from the first color light component and the second color light component) transmitted through the first and second dichroic films is extracted.
In this case, since the curve indicating the characteristic of the first dichroic film has a shape substantially equal to the characteristic curve of the ideal green spectral characteristic, a trimming filter with a dichroic film is formed on the exit surface of the prism. A characteristic close to the ideal spectral characteristic can be obtained without using it. Since it is not necessary to use a trimming filter with a dichroic film, it is possible to suppress the occurrence of ghosts and flares conventionally caused by the dichroic film of the trimming filter. Thus, it is possible to realize an imaging system having ideal spectral characteristics with reduced ghost and flare.

  Here, in the color separation optical system according to the fourth to sixth aspects of the present invention, the “shape substantially equal to the ideal characteristic curve of spectral characteristics” is, for example, a standardized predetermined ideal characteristic curve. The inclination of the characteristic curve is preferably within ± 10% with respect to the inclination.

An image pickup apparatus according to the present invention includes a color separation optical system according to any one of the first to third aspects of the present invention or a color separation optical system according to any one of the fourth to sixth aspects of the present invention, An image pickup device is provided corresponding to each color light separated by the color separation optical system and outputs an electric signal corresponding to each incident color light.
In the imaging apparatus according to the present invention, an imaging signal with high color reproducibility can be obtained based on each color light obtained by the color separation optical system of the present invention.
Further, in the image pickup apparatus according to the present invention, when the color separation optical system uses an ideal spectral characteristic having a characteristic that can be subjected to reverse conversion so as to reduce a negative value, it is obtained by the image pickup element. Based on the signal value, an arithmetic circuit that performs inverse transformation to reproduce a negative value in the ideal characteristic may be further provided.

  According to the color separation optical system of the first or fourth aspect of the present invention, the blue light reflected by the first dichroic film is extracted from the first prism as the first color light component, and the second dichroic is used. In a configuration in which red light or green light reflected by the film is extracted from the second prism as a second color light component, a curve indicating the characteristics of the first dichroic film and a curve indicating the characteristics of the second dichroic film are: Since it is configured to have a shape that conforms to the characteristic curve of the ideal green spectral characteristic or a shape that is substantially equal, the ideal spectral characteristic can be obtained without using a trimming filter with a dichroic film on the exit surface of the prism. It is possible to obtain characteristics close to. This makes it possible to reduce ghosts and flares compared to the conventional wavelength selection method using a trimming filter with a dichroic film, and to improve the color reproducibility by obtaining characteristics close to ideal spectral characteristics. Can do.

  According to the color separation optical system of the second or fifth aspect of the present invention, the red light reflected by the first dichroic film is extracted from the first prism as the first color light component, and the second dichroic is used. In a configuration in which blue light or green light reflected by the film is extracted from the second prism as a second color light component, a curve indicating the characteristics of the first dichroic film and a curve indicating the characteristics of the second dichroic film are: Since it is configured to have a shape that conforms to the characteristic curve of the ideal green spectral characteristic or a shape that is substantially equal, the ideal spectral characteristic can be obtained without using a trimming filter with a dichroic film on the exit surface of the prism. It is possible to obtain characteristics close to. This makes it possible to reduce ghosts and flares compared to the conventional wavelength selection method using a trimming filter with a dichroic film, and to improve the color reproducibility by obtaining characteristics close to ideal spectral characteristics. Can do.

  According to the color separation optical system of the third or sixth aspect of the present invention, the green light reflected by the first dichroic film is extracted from the first prism as the first color light component, and the second dichroic is used. In the configuration in which blue light or red light reflected by the film is extracted from the second prism as the second color light component, the curve indicating the characteristic of the first dichroic film follows the characteristic curve of the ideal green spectral characteristic. Since the configuration is such that it has a shape or substantially the same shape, it is possible to obtain characteristics close to ideal spectral characteristics without using a trimming filter with a dichroic film on the exit surface of the prism. This makes it possible to reduce ghosts and flares compared to the conventional wavelength selection method using a trimming filter with a dichroic film, and to improve the color reproducibility by obtaining characteristics close to ideal spectral characteristics. Can do.

  According to the image pickup apparatus of the present invention, since an image pickup signal corresponding to the color light obtained by the high-performance color separation optical system of the present invention is output, it is possible to perform image pickup with high color reproducibility.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[First Embodiment]

  FIG. 1 shows a main configuration of an imaging apparatus including a color separation optical system 1 according to the first embodiment of the present invention. This imaging device is used as an imaging part of a television camera, for example. The color separation optical system 1 separates the incident light L incident through the photographing lens 2 into three color light components of blue light LB, red light LR, and green light LG. Image pickup elements 4B, 4R, and 4G for each color light such as a CCD are arranged at positions corresponding to the respective color lights separated by the color separation optical system 1. The color separation optical system 1 is called a Philips type color separation optical system, and sequentially from the light incident side along the optical axis Z1, an IR (infrared) cut filter 3, a first prism 10, A second prism 20 and a third prism 30 are provided. The color separation optical system 1 in this embodiment is a configuration example in which the first prism 10 extracts blue light LB, the second prism 20 extracts red light LR, and the third prism 30 extracts green light LG.

  The first prism 10 has a first surface 11, a second surface 12, and a third surface 13. The third surface 13 of the first prism 10 is a light exit surface. A trimming filter 51 is provided on the exit surface. The trimming filter 51 is not provided with a dichroic film for characteristic adjustment which has been conventionally used. Instead, an antireflection film 51AR for preventing ghost and flare is provided on the light emission surface of the trimming filter 51. Is formed. Note that the antireflection film 51AR may be formed directly on the third surface 13 of the first prism 10 without providing the trimming filter 51.

  A blue light reflecting dichroic film DB as a first dichroic film is formed on the second surface 12 of the first prism 10. The blue light reflecting dichroic film DB has a film configuration that reflects the blue light LB as the first color light component and transmits the red light LR and the green light LG. The blue light reflecting dichroic film DB is an ideal in which the slope of the transmission characteristic curve indicating the transmittance with respect to the wavelength is converted from the chromaticity coordinates of the three primary colors of the color reproduction medium and is determined based on the color matching function of the XYZ color system. It has a shape along the characteristic curve on the short wavelength side of the green spectral characteristic. The “ideal characteristics” here are “target predetermined spectral characteristics”. For example, the characteristics as shown in FIG. 45, for example, which have been conventionally known, are converted from the chromaticity coordinates of the three primary colors of the color reproduction medium, and can be obtained by primary conversion of the color matching function of the XYZ color system. As the “ideal characteristic”, an ideal characteristic itself represented by a color matching function of the RGB color system may be used.

  FIG. 2A shows an example of a transmission characteristic curve of the blue light reflecting dichroic film DB in the configuration example of FIG. The blue light reflecting dichroic film DB has a transmission characteristic curve whose slope is in accordance with the characteristic curve on the short wavelength side of the ideal green spectral characteristic within a wavelength range of 430 nm to 670 nm. It is configured to have a shape that changes to rise. More specifically, the average slope value at which the transmission characteristic curve changes from 20% to 80% of the range between the lowest transmittance and the highest transmittance within a wavelength range of 430 nm to 670 nm is 0.2%. It is preferable to have a shape of (% / nm) or more and 2.0 (% / nm) or less.

  The second prism 20 has a first surface 21, a second surface 22, and a third surface 23. The second prism 20 is disposed with a predetermined air interval 10AG with respect to the first prism 10. More specifically, the first surface 21 of the second prism 20 and the second surface 12 of the first prism 10 are arranged to face each other with an air gap 10AG so as to be substantially parallel. The third surface 23 of the second prism 20 is a light exit surface. A trimming filter 52 is provided on the exit surface. Similar to the trimming filter 51 in the first prism 10, the trimming filter 52 is not provided with a dichroic film for characteristic adjustment. Instead, the trimming filter 52 has a light exit surface for preventing ghost and flare. An antireflection film 52AR is formed. Note that the antireflection film 52AR may be formed directly on the third surface 23 of the second prism 20 without providing the trimming filter 52.

  A red light reflecting dichroic film DR as a second dichroic film is formed on the second surface 22 of the second prism 20. The red light reflecting dichroic film DR has a film configuration that reflects the red light LR as the second color light component and transmits the green light LG. The red light reflecting dichroic film DR has a shape in which the slope of the transmission characteristic curve indicating the transmittance with respect to the wavelength follows the characteristic curve on the long wavelength side of the ideal green spectral characteristic described above.

  FIG. 2B shows an example of a transmission characteristic curve of the red light reflecting dichroic film DR in the configuration example of FIG. The red light reflecting dichroic film DR has a transmission characteristic curve whose slope is in line with the characteristic curve on the long wavelength side of the ideal green spectral characteristic within a wavelength range of 430 nm to 670 nm. It is configured to have a shape that changes to fall. More specifically, the average slope value at which the transmission characteristic curve changes from 80% to 20% of the range between the highest transmittance and the lowest transmittance within a wavelength range of 430 nm to 670 nm is −2. It preferably has a shape of 0 (% / nm) or more and -0.2 (% / nm) or less.

Further, the blue light reflecting dichroic film DB may have a shape substantially equal to the characteristic curve on the short wavelength side of the ideal green spectral characteristic. The red light reflecting dichroic film DR may have a shape in which the slope of the transmission characteristic curve indicating the transmittance with respect to the wavelength is substantially equal to the characteristic curve on the long wavelength side of the ideal green spectral characteristic.
Here, as the “shape substantially equal to the characteristic curve of the ideal spectral characteristic”, for example, the inclination of the characteristic curve with respect to the standardized predetermined ideal characteristic curve as shown in FIG. It is preferable that it is within ± 10%.

  The third prism 30 has a first surface 31 and a second surface 32. The third prism 30 is bonded to the second prism 20 via the red light reflecting dichroic film DR. More specifically, the second surface 22 of the second prism 20 and the first surface 31 of the third prism 30 are joined via the red light reflecting dichroic film DR. The second surface 32 of the third prism 30 is a light exit surface. A trimming filter 53 is provided on the exit surface. Similar to the trimming filter 51 in the first prism 10, the trimming filter 53 is not provided with a dichroic film for characteristic adjustment. Instead, the trimming filter 53 has a light exit surface for preventing ghost and flare. An antireflection film 53AR is formed. Note that the antireflection film 53AR may be formed directly on the second surface 32 of the third prism 30 without providing the trimming filter 53.

  The IR cut filter 3 is disposed on the front side of the first prism 10. The IR cut filter 3 is preferably composed of an absorptive filter having characteristics approximating to visual sensitivity in order to easily obtain characteristics close to ideal spectral characteristics. The “absorptive filter having characteristics approximating the visibility” referred to here is called a “visibility correction filter” and is a transmission that approximates the sensitivity characteristics of the human eye and attenuates from the green to the red wavelength. This is an absorptive filter that has a low transmittance and a low transmittance even in the infrared region. Note that the IR cut filter 3 may be disposed not on the front side of the first prism 10 but on the light exit surface side of a prism (second prism 20 in FIG. 1) that extracts red light. Further, the IR cut filter 3 may be disposed on both the front side of the first prism 10 and the light exit surface side of the prism that extracts red light. Further, when infrared light cannot be sufficiently removed only by the absorption filter, a coat type infrared cut filter that cuts infrared light may be further provided. FIG. 1 shows a configuration example in which a flat absorption filter is coated with a film 3R that cuts infrared light. However, in the case where the IR cut filter 3 is arranged on the light exit surface side of the prism that extracts red light, it is preferable that the IR cut coat is not applied and only the absorption filter is used. In that case, it is more preferable that the absorption filter is provided with an antireflection film.

  Although not shown, the color separation optical system 1 may further include an absorption type or coat type ultraviolet cut filter that is disposed in front of the first prism 10 and cuts ultraviolet light.

  Next, the operation of the imaging apparatus in the present embodiment, particularly the optical operation and effect of the color separation optical system 1 will be described.

  In this imaging apparatus, subject light from a subject (not shown) irradiated by a light source (not shown) is incident on the color separation optical system 1 via the photographing lens 2. In the color separation optical system 1, the incident light L is decomposed into three color light components of blue light LB, red light LR, and green light LG. More specifically, first, the blue light LB of the incident light L is reflected by the blue light reflecting dichroic film DB and extracted from the first prism 10 as the first color light component. Further, the red light LR that has passed through the blue light reflecting dichroic film DB is reflected by the red light reflecting dichroic film DR and is extracted from the second prism 20 as the second color light component. Further, the green light LG transmitted through the blue light reflecting dichroic film DB and the red light reflecting dichroic film DR is extracted from the third prism 30 as a third color light component. Each color light separated by the color separation optical system 1 enters the image pickup devices 4B, 4R, 4G provided corresponding to each color light. The imaging elements 4B, 4R, and 4G output an electrical signal corresponding to each incident color light as an imaging signal.

  In the present embodiment, the curve indicating the characteristic of the blue light reflecting dichroic film DB and the curve indicating the characteristic of the red light reflecting dichroic film DR have a shape along the characteristic curve of the ideal green spectral characteristic. Thus, characteristics close to ideal spectral characteristics can be obtained without using a trimming filter with a dichroic film on the exit surface of the prism. Since it is not necessary to use a trimming filter with a dichroic film, it is possible to suppress the occurrence of ghosts and flares conventionally caused by the dichroic film of the trimming filter. Thus, it is possible to realize an imaging system having ideal spectral characteristics with reduced ghost and flare.

Hereinafter, the spectral characteristics obtained by this embodiment will be shown by actual design examples.
FIG. 3 shows an example of spectral characteristics of optical elements other than the prism portion in the imaging apparatus. FIG. 3 shows a light source having a color temperature of 3200K (not shown), an imaging lens 2, an IR cut filter 3, and a CCD as the image sensors 4R, 4G, and 4B as characteristics of optical elements other than the prism portion. FIG. 4 shows characteristics of a specific design example of the blue light reflecting dichroic film DB and the red light reflecting dichroic film DR used in the color separation optical system 1 shown in FIG. The characteristics shown in FIG. 4 can be obtained by, for example, the film design specifically shown as numerical data in FIGS. However, the film material, the number of layers, and the film thickness of each layer are not limited to the examples of FIGS.

  FIG. 5 shows the spectral transmission characteristics of the entire prism portion (the first, second and third prisms 10, 20, 30) on which the film design shown in FIG. 4 is applied. FIG. 6 shows the overall spectral transmission characteristics of the entire optical system in the imaging apparatus, combining the characteristics of the optical elements other than the prism section shown in FIG. 3 and the characteristics of the entire prism section shown in FIG. ing.

  FIG. 7 shows characteristics obtained by normalizing the overall spectral transmission characteristics shown in FIG. 6, and the vertical axis shows the transmittance intensity. FIG. 7 also shows ideal characteristics (B0, R0, G0) and characteristics (B2, R2, G2) of general products when a conventional color separation optical system is used for comparison. Yes. Note that the ideal characteristics referred to here are those conventionally shown in FIG. FIG. 7 shows that the characteristics (B1, R1, G1) in the design example according to the present embodiment are closer to the ideal characteristics than the characteristics of the conventional general products.

  FIG. 8 is a u′v ′ chromaticity diagram showing the color reproducibility in the design example according to the present embodiment in comparison with the prior art. The horizontal axis represents the u ′ chromaticity coordinate value, and the vertical axis represents the v ′ chromaticity coordinate value. In the figure, a triangular area surrounded by a broken line connects the chromaticity coordinate values of the three primary colors R, G, and B of the color reproduction medium (monitor), and indicates a color range that can be reproduced on the color reproduction medium. . The closer to the triangle, the higher the saturation. 8 is hidden because the chromaticity coordinates are enlarged, the primary red color R coordinate point of the color reproduction medium is present in the upper right direction, and the primary blue color B coordinate point is in the lower left direction. Existing. In the figure, the coordinate point of the white circle “◯” in the triangular area indicates the object white color. Also, in the figure, coordinate points indicated by black triangles “▲” in the triangular area represent coordinate points of an arbitrary color according to the conventional configuration. Coordinate points indicated by white squares “□” represent coordinate points of an arbitrary color in the design example according to the present embodiment. In the conventional configuration and the design example according to the present embodiment, the deviation amount from the ideal point (reproduction color deviation amount) is indicated by a solid line connecting the coordinate points. In the conventional configuration, the reproduced color has moved in the red area in the upper right, but the design example according to the present embodiment is greatly improved. In the design example according to the present embodiment, as a whole balance, there is no place where the color moves from the ideal point, and the color reproducibility is improved. The average color difference for the seven colors B (blue), G (green), R (red), C (cyan), Y (yellow), M (magenta), and skin (skin color) is 8.84 to 7.37. Improved.

  FIG. 9 shows the amount of ghost generation in the color separation optical system 1 according to the present embodiment in comparison with the conventional configuration. Here, the conventional configuration is the case of the color separation optical system 101 including trimming filters 151, 152, 153 on which dichroic films 151A, 152A, 153A are formed as shown in FIG. In contrast, in the color separation optical system 1 according to the present embodiment, the anti-reflection films 51AR, 52AR, and 53AR for preventing ghost and flare are provided on the light exit surfaces of the trimming filters 51, 52, and 53 instead of the dichroic film. Is formed.

  FIG. 9 shows, as an example, the amount of ghost generated on the side where the green light LG is emitted. In FIG. 9, a curve denoted by reference numeral 95 indicates the transmittance of the green light LG between the trimming filter 153 in the conventional configuration and the trimming filter 53 in the present embodiment. A curve denoted by reference numeral 91 indicates the reflectance of the dichroic film 153A of the trimming filter 153 in the conventional configuration. A curve denoted by reference numeral 92 indicates the reflectance of the antireflection film 53AR of the trimming filter 53 in the present embodiment. The amount of ghost of the green light LG in the conventional configuration is obtained by multiplying the transmittance indicated by reference numeral 95 and the reflectance indicated by reference numeral 91. A curve denoted by reference numeral 93 represents the conventional ghost generation amount. On the other hand, the ghost generation amount of the green light LG in the present embodiment is obtained by multiplying the transmittance indicated by reference numeral 95 and the reflectance indicated by reference numeral 92. A curve denoted by reference numeral 94 indicates the amount of ghost generated in this embodiment. Compared with the prior art, the amount of ghost generation is greatly reduced in the present embodiment. Note that FIG. 9 shows an example of a general antireflection coating that reduces reflection in the entire visible light region as the antireflection film 53AR. However, an antireflection coating in a specific wavelength range that reduces the reflectance particularly in the wavelength band emitted from the prism exit surface may be used.

As described above, according to the color separation optical system 1 according to the present embodiment, ghosts and flares can be reduced as compared with the conventional wavelength selection method using a trimming filter with a dichroic film, and ideally. It is possible to improve the color reproducibility by obtaining a characteristic close to a typical spectral characteristic. Further, according to the imaging apparatus according to the present embodiment, since the imaging signal corresponding to the color light obtained by the high-performance color separation optical system 1 according to the present embodiment is output, the color reproducibility is improved. High imaging can be performed.
<Modification of the first embodiment>

Hereinafter, modified examples of the above-described color separation optical system 1 will be described. In the following modification, the same reference numerals are given to portions corresponding to the configuration example shown in FIG.
<< First Modification >>

  FIG. 12 shows the configuration of the color separation optical system 1-1 according to the first modification. The color separation optical system 1-1 is different from the color separation optical system 1 in FIG. The color separation optical system 1-1 is configured to extract blue light LB with the first prism 10, green light LG with the second prism 20, and red light LR with the third prism 30.

  In the color separation optical system 1-1 according to the present modification, a blue light reflecting dichroic film is used as the first dichroic film on the second surface 12 of the first prism 10 as in the color separation optical system 1 of FIG. DB is formed. FIG. 13A shows an example of the transmission characteristic curve of the blue light reflecting dichroic film DB in this modification, which is the same as the transmission characteristic curve shown in FIG.

  In the color separation optical system 1 of FIG. 1, the red light reflecting dichroic film DR is formed as the second dichroic film on the second surface 22 of the second prism 20, but the color separation according to this modification example. In the optical system 1-1, a green light reflecting dichroic film DG is formed as a second dichroic film instead of the red light reflecting dichroic film DR. The green light reflecting dichroic film DG is configured to reflect the green light LG as the second color light component and transmit the red light LR. In this modification, the green light reflecting dichroic film DG has a shape in which the slope of the reflection characteristic curve indicating the reflectance with respect to the wavelength follows the characteristic curve on the long wavelength side of the ideal green spectral characteristic.

  FIG. 13B shows an example of the reflection characteristic curve of the green light reflecting dichroic film DG in the configuration example of FIG. In this modification, the green light reflecting dichroic film DG is highly reflective within the wavelength range of 430 nm or more and 670 nm or less in the inclination of the reflection characteristic curve along the characteristic curve on the long wavelength side of the ideal green spectral characteristic. It is configured to have a shape that changes from a low rate to a low reflectivity. More specifically, the average slope value at which the reflection characteristic curve changes from 80% to 20% of the range between the highest reflectance and the lowest reflectance within the wavelength range of 430 nm to 670 nm is −2. It preferably has a shape of 0 (% / nm) or more and -0.2 (% / nm) or less.

In the present modification, the green light reflecting dichroic film DG has a shape in which the slope of the reflection characteristic curve indicating the reflectance with respect to the wavelength is substantially equal to the characteristic curve on the long wavelength side of the ideal green spectral characteristic. May be.
Here, as the “shape substantially equal to the characteristic curve of the ideal spectral characteristic”, for example, the inclination of the characteristic curve with respect to the standardized predetermined ideal characteristic curve as shown in FIG. It is preferable that it is within ± 10%.

  In the color separation optical system 1-1, first, the blue light LB of the incident light L is reflected by the blue light reflecting dichroic film DB and extracted from the first prism 10 as the first color light component. Further, the green light LG transmitted through the blue light reflecting dichroic film DB is reflected by the green light reflecting dichroic film DG and extracted from the second prism 20 as the second color light component. Further, the red light LR transmitted through the blue light reflecting dichroic film DB and the green light reflecting dichroic film DG is extracted from the third prism 30 as a third color light component.

In this modification, the curve indicating the characteristics of the blue light reflecting dichroic film DB and the curve indicating the characteristics of the green light reflecting dichroic film DG have shapes that conform to the characteristic curve of the ideal green spectral characteristic. Thus, characteristics close to ideal spectral characteristics can be obtained without using a trimming filter with a dichroic film on the exit surface of the prism. Since it is not necessary to use a trimming filter with a dichroic film, it is possible to suppress the occurrence of ghosts and flares conventionally caused by the dichroic film of the trimming filter. Thus, it is possible to realize an imaging system having ideal spectral characteristics with reduced ghost and flare. Other configurations, operations, and effects are the same as those of the color separation optical system 1 of FIG.
<< Second Modification >>

  FIG. 14 shows a configuration of a color separation optical system 1-2 according to the second modification. The color separation optical system 1-2 is different from the color separation optical system 1 shown in FIG. The color separation optical system 1-2 is configured to extract the red light LR with the first prism 10, the blue light LB with the second prism 20, and the green light LG with the third prism 30.

  In the color separation optical system 1 of FIG. 1, the blue light reflecting dichroic film DB is formed as the first dichroic film on the second surface 12 of the first prism 10. In the optical system 1-2, a red light reflecting dichroic film DR is formed instead of the blue light reflecting dichroic film DB. The red light reflecting dichroic film DR has a film configuration that reflects the red light LR as the first color light component and transmits the blue light LB and the green light LG. The red light reflecting dichroic film DR in the present modification example is different only in the surface of the prism on which the film is formed, and the characteristic itself is different from that of the red light reflecting dichroic film DR in the color separation optical system 1 in FIG. It is the same. The transmission characteristic curve is the same as the transmission characteristic curve shown in FIG.

  Further, in the color separation optical system 1 of FIG. 1, the red light reflecting dichroic film DR is formed as the second dichroic film on the second surface 22 of the second prism 20. In the color separation optical system 1-2, a blue light reflecting dichroic film DB is formed as a second dichroic film instead of the red light reflecting dichroic film DR. The blue light reflecting dichroic film DB is configured to reflect the blue light LB as the second color light component and transmit the green light LG. The blue light reflecting dichroic film DB in this modification example is different only in the surface of the prism on which the film is formed, and the characteristic itself is different from that of the blue light reflecting dichroic film DB in the color separation optical system 1 in FIG. It is the same. The transmission characteristic curve is the same as the transmission characteristic curve shown in FIG.

  In the color separation optical system 1-2, first, the red light LR of the incident light L is reflected by the red light reflecting dichroic film DR and extracted from the first prism 10 as the first color light component. Further, the blue light LB transmitted through the red light reflecting dichroic film DR is reflected by the blue light reflecting dichroic film DB, and is extracted from the second prism 20 as the second color light component. Further, the green light LG transmitted through the red light reflecting dichroic film DR and the blue light reflecting dichroic film DB is extracted from the third prism 30 as a third color light component.

In the present modification, the prism surfaces forming the red light reflecting dichroic film DR and the blue light reflecting dichroic film DB are different, and only the order of extracting each color light is different. This is the same as the color separation optical system 1.
<< Third Modification >>

  FIG. 15 shows a configuration of a color separation optical system 1-3 according to a third modification. The color separation optical system 1-3 is different from the color separation optical system 1 shown in FIG. The color separation optical system 1-3 is configured to extract red light LR with the first prism 10, green light LG with the second prism 20, and blue light LB with the third prism 30.

  In the color separation optical system 1 of FIG. 1, the blue light reflecting dichroic film DB is formed as the first dichroic film on the second surface 12 of the first prism 10. In the optical system 1-3, a red light reflecting dichroic film DR is formed instead of the blue light reflecting dichroic film DB. The red light reflecting dichroic film DR has a film configuration that reflects the red light LR as the first color light component and transmits the blue light LB and the green light LG. The red light reflecting dichroic film DR in the present modification is different from the color separation optical system 1 in FIG. 1 only in the surface of the prism on which the film is formed. This is the same as the red light reflecting dichroic film DR in the optical system 1. FIG. 16B shows an example of the transmission characteristic curve of the red light reflecting dichroic film DR in this modification, which is the same as the transmission characteristic curve shown in FIG.

  In the color separation optical system 1 of FIG. 1, the red light reflecting dichroic film DR is formed as the second dichroic film on the second surface 22 of the second prism 20, but the color separation according to this modification example. In the optical system 1-3, a green light reflecting dichroic film DG is formed as the second dichroic film instead of the red light reflecting dichroic film DR. The green light reflecting dichroic film DG has a film configuration that reflects the green light LG as the second color light component and transmits the blue light LB. In this modification, the green light reflecting dichroic film DG has a shape in which the slope of the reflection characteristic curve indicating the reflectance with respect to the wavelength follows the characteristic curve on the short wavelength side of the ideal green spectral characteristic.

  FIG. 16A shows an example of a reflection characteristic curve of the green light reflecting dichroic film DG in the configuration example of FIG. In this modification, the green light reflecting dichroic film DG has a low reflectance within a wavelength range of 430 nm or more and 670 nm or less in which the inclination of the reflection characteristic curve follows the characteristic curve on the short wavelength side of the ideal green spectral characteristic. It is configured to have a shape that changes from rising to high reflectance. More specifically, the average slope value at which the reflection characteristic curve changes from 20% to 80% of the range between the lowest reflectance and the highest reflectance within a wavelength range of 430 nm to 670 nm is 0.2%. It is preferable to have a shape of (% / nm) or more and 2.0 (% / nm) or less.

In this modification, the green light reflecting dichroic film DG has a shape in which the slope of the reflection characteristic curve indicating the reflectance with respect to the wavelength is substantially equal to the characteristic curve on the short wavelength side of the ideal green spectral characteristic. May be.
Here, as the “shape substantially equal to the characteristic curve of the ideal spectral characteristic”, for example, the inclination of the characteristic curve with respect to the standardized predetermined ideal characteristic curve as shown in FIG. It is preferable that it is within ± 10%.

  In the color separation optical system 1-3, first, the red light LR of the incident light L is reflected by the red light reflecting dichroic film DR and extracted from the first prism 10 as the first color light component. Further, the green light LG transmitted through the red light reflecting dichroic film DR is reflected by the green light reflecting dichroic film DG and extracted from the second prism 20 as the second color light component. Further, the blue light LB transmitted through the red light reflecting dichroic film DR and the green light reflecting dichroic film DG is extracted from the third prism 30 as a third color light component.

In this modification, the curve indicating the characteristic of the red light reflecting dichroic film DR and the curve indicating the characteristic of the green light reflecting dichroic film DG have shapes that conform to the characteristic curve of the ideal green spectral characteristic. Thus, characteristics close to ideal spectral characteristics can be obtained without using a trimming filter with a dichroic film on the exit surface of the prism. Since it is not necessary to use a trimming filter with a dichroic film, it is possible to suppress the occurrence of ghosts and flares conventionally caused by the dichroic film of the trimming filter. Thus, it is possible to realize an imaging system having ideal spectral characteristics with reduced ghost and flare. Other configurations, operations, and effects are the same as those of the color separation optical system 1 of FIG.
[Second Embodiment]

  Next, a second embodiment of the present invention will be described. In addition, the same code | symbol is attached | subjected to the component substantially the same as the said 1st Embodiment, and description is abbreviate | omitted suitably.

  FIG. 17 shows the configuration of a color separation optical system 1A according to the second embodiment of the present invention. The color separation optical system 1A is different from the color separation optical system 1 shown in FIG. In this color separation optical system 1A, the first prism 10 extracts green light LG, the second prism 20 extracts blue light LB, and the third prism 30 extracts red light LR.

  Further, in the color separation optical system 1 of FIG. 1, the blue light reflecting dichroic film DB is formed as the first dichroic film on the second surface 12 of the first prism 10, but in this embodiment, In the color separation optical system 1A, a green light reflecting dichroic film DG is formed instead of the blue light reflecting dichroic film DB. The green light reflecting dichroic film DG has a film configuration that reflects the green light LG as the first color light component and transmits the blue light LB and the red light LR. In the green light reflecting dichroic film DG in this modification, the inclination of the reflection characteristic curve indicating the reflectance with respect to the wavelength is converted from the chromaticity coordinates of the three primary colors of the color reproduction medium, and is determined based on the color matching function of the XYZ color system. It has a shape along the characteristic curve on the short wavelength side and long wavelength side of the ideal green spectral characteristic. The “ideal characteristic” here is a conventionally known characteristic as shown in FIG. 45, for example, as in the first embodiment, and is converted from the chromaticity coordinates of the three primary colors of the color reproduction medium. Then, it can be obtained by primary conversion of the color matching function of the XYZ color system. As the “ideal characteristic”, an ideal characteristic itself represented by a color matching function of the RGB color system may be used.

  18A and 18B show an example of the reflection characteristic curve of the green light reflecting dichroic film DG in the configuration example of FIG. The green light reflecting dichroic film DG has a short wavelength of an ideal green spectral characteristic, as shown in FIG. 18A, in the portion where the slope of the reflection characteristic curve rises within the wavelength range of 430 nm to 670 nm. It is configured to have a shape that changes from a low reflectance to a high reflectance along the characteristic curve on the side. More specifically, in the portion where the reflection characteristic curve changes from 20% to 80% of the range between the lowest reflectance and the highest reflectance within the wavelength range of 430 nm to 670 nm, the average slope value is 0. It preferably has a shape of 2 (% / nm) to 2.0 (% / nm).

  Further, as shown in FIG. 18B, at the portion falling within the wavelength range of 430 nm to 670 nm, the high reflectance is reduced from the high reflectance in the form of the characteristic curve on the long wavelength side of the ideal green spectral characteristic. It is configured to have a shape that changes to reflectivity. More specifically, in the wavelength range of 430 nm or more and 670 nm or less, the average slope value is −2.0 (% /%) at the portion where the range between 80% and 20% of the range between the highest reflectance and the lowest reflectance changes. nm) to −0.2 (% / nm) or less.

In the present embodiment, the green light reflecting dichroic film DG has a slope of the reflection characteristic curve indicating the reflectance with respect to the wavelength substantially equal to the characteristic curve on the short wavelength side and the long wavelength side of the ideal green spectral characteristic. It may have a shape.
Here, as the “shape substantially equal to the characteristic curve of the ideal spectral characteristic”, for example, the inclination of the characteristic curve with respect to the standardized predetermined ideal characteristic curve as shown in FIG. It is preferable that it is within ± 10%.

  In the color separation optical system 1 shown in FIG. 1, the red light reflecting dichroic film DR is formed on the second surface 22 of the second prism 20 as the second dichroic film. In the color separation optical system 1A, a blue light reflecting dichroic film DB is formed as the second dichroic film instead of the red light reflecting dichroic film DR. In the present embodiment, the blue light reflecting dichroic film DB has a film configuration that reflects the blue light LB as the second color light component and transmits the red light LR. In the blue light reflecting dichroic film DB in the present embodiment, the slope of the transmission characteristic curve indicating the transmittance with respect to the wavelength is converted from the chromaticity coordinates of the three primary colors of the color reproduction medium, based on the color matching function of the XYZ color system. It has a shape along the characteristic curve on the short wavelength side of the determined ideal red spectral characteristic. The “ideal characteristic” here is a conventionally known characteristic as shown in FIG. 45, for example, converted from the chromaticity coordinates of the three primary colors of the color reproduction medium, and the color matching function of the XYZ color system. Can be obtained by a linear transformation. As the “ideal characteristic”, an ideal characteristic itself represented by a color matching function of the RGB color system may be used.

  For reference, FIG. 19 shows characteristics of a specific design example of the green light reflecting dichroic film DG and the blue light reflecting dichroic film DB used in the color separation optical system 1A shown in FIG. In FIG. 19, the green light reflecting dichroic film DG shows reflection characteristics, and the blue light reflecting dichroic film DB shows transmission characteristics. FIG. 19 also shows the characteristics of the red light reflecting dichroic film DR in a modified example shown in FIG. 20 described later.

  In the color separation optical system 1A, first, the green light LG of the incident light L is reflected by the green light reflecting dichroic film DG and extracted from the first prism 10 as the first color light component. Further, the blue light LB transmitted through the green light reflecting dichroic film DG is reflected by the blue light reflecting dichroic film DB, and is extracted from the second prism 20 as the second color light component. Further, the red light LR transmitted through the green light reflecting dichroic film DG and the blue light reflecting dichroic film DB is extracted from the third prism 30 as a third color light component.

In the present embodiment, the curve indicating the characteristic of the green light reflecting dichroic film DG has a shape that follows the characteristic curve of the ideal green spectral characteristic, and the curve indicating the characteristic of the blue light reflecting dichroic film DB is ideal. Because it has a shape that follows the characteristic curve on the short wavelength side of typical red spectral characteristics, characteristics close to ideal spectral characteristics can be obtained without using a trimming filter with a dichroic film on the exit surface of the prism. It is done. Since it is not necessary to use a trimming filter with a dichroic film, it is possible to suppress the occurrence of ghosts and flares conventionally caused by the dichroic film of the trimming filter. Thus, it is possible to realize an imaging system having ideal spectral characteristics with reduced ghost and flare. Other configurations, operations, and effects are the same as those of the color separation optical system 1 of FIG. 1 in the first embodiment.
<Modification of Second Embodiment>

  Hereinafter, modifications of the above-described color separation optical system 1A will be described. In the following modified example, the same reference numerals are given to the portions corresponding to the configuration example shown in FIG.

  FIG. 20 shows a configuration of a color separation optical system 1A-1 according to this modification. This color separation optical system 1A-1 is different from the color separation optical system 1A shown in FIG. In this color separation optical system 1A-1, the first prism 10 extracts green light LG, the second prism 20 extracts red light LR, and the third prism 30 extracts blue light LB.

  In the color separation optical system 1A-1 according to this modification, the second surface 12 of the first prism 10 has a green light reflecting dichroic film as the first dichroic film, as in the color separation optical system 1 of FIG. DG is formed. The characteristics of the green light reflecting dichroic film DG in this modification are the same as those of the color separation optical system 1 in FIG. The reflection characteristic curve is the same as the reflection characteristic curve shown in FIGS.

  In the color separation optical system 1A of FIG. 17, the blue light reflecting dichroic film DB is formed as the second dichroic film on the second surface 22 of the second prism 20, but the color separation according to this modification example. In the optical system 1A-1, a red light reflecting dichroic film DR is formed as a second dichroic film instead of the blue light reflecting dichroic film DB. In the present embodiment, the red light reflecting dichroic film DR has a film configuration that reflects the red light LR as the second color light component and transmits the blue light LB. In the red light reflecting dichroic film DR in the present embodiment, the slope of the reflection characteristic curve indicating the reflectance with respect to the wavelength is converted from the chromaticity coordinates of the three primary colors of the color reproduction medium, based on the color matching function of the XYZ color system. It has a shape along the characteristic curve on the short wavelength side of the determined ideal red spectral characteristic. The “ideal characteristic” here is a conventionally known characteristic as shown in FIG. 45, for example, converted from the chromaticity coordinates of the three primary colors of the color reproduction medium, and the color matching function of the XYZ color system. Can be obtained by a linear transformation. As the “ideal characteristic”, an ideal characteristic itself represented by a color matching function of the RGB color system may be used.

  For reference, FIG. 19 shows characteristics in a specific design example of the green light reflecting dichroic film DG and the red light reflecting dichroic film DR used in the color separation optical system 1A-1 shown in FIG. In FIG. 19, the green light reflecting dichroic film DG shows reflection characteristics. The red light reflecting dichroic film DR also exhibits reflection characteristics.

  In the color separation optical system 1A-1, first, the green light LG of the incident light L is reflected by the green light reflecting dichroic film DG and extracted from the first prism 10 as the first color light component. The red light LR that has passed through the green light reflecting dichroic film DG is reflected by the red light reflecting dichroic film DR, and is extracted from the second prism 20 as the second color light component. Further, the blue light LB transmitted through the green light reflecting dichroic film DG and the red light reflecting dichroic film DR is extracted from the third prism 30 as a third color light component.

In the present embodiment, the curve indicating the characteristic of the green light reflecting dichroic film DG has a shape that follows the characteristic curve of the ideal green spectral characteristic, and the curve indicating the characteristic of the red light reflecting dichroic film DR is ideal. Because it has a shape that follows the characteristic curve on the short wavelength side of typical red spectral characteristics, characteristics close to ideal spectral characteristics can be obtained without using a trimming filter with a dichroic film on the exit surface of the prism. It is done. Since it is not necessary to use a trimming filter with a dichroic film, it is possible to suppress the occurrence of ghosts and flares conventionally caused by the dichroic film of the trimming filter. Thus, it is possible to realize an imaging system having ideal spectral characteristics with reduced ghost and flare. Other configurations, operations, and effects are the same as those of the color separation optical system 1 of FIG. 1 in the first embodiment.
[Third Embodiment]

  Next, a third embodiment of the present invention will be described. Note that components that are substantially the same as those in the first and second embodiments are given the same reference numerals, and descriptions thereof are omitted as appropriate.

  In the first and second embodiments described above, a configuration in which an air space 10AG is provided between the first prism 10 and the second prism 20, and a color separation optical system generally called a Philips type will be described as an example. However, the structure is not limited to the Philips type as long as it has a function of separating white light into three colors.

  FIG. 21 shows a configuration of a color separation optical system 1A-2 according to the third embodiment of the present invention. In the color separation optical system 1A-2, the air space 10AG is not provided between the first prism 10 and the second prism 20, and the second surface 12 of the first prism 10 and the second prism 12 The first surface 21 of the prism 20 is in direct contact with the green light reflecting dichroic film DG. Other configurations are basically the same as those of the color separation optical system 1A shown in FIG. That is, in the color separation optical system 1A-2, similarly to the color separation optical system 1A shown in FIG. 17, the first prism 10 uses green light LG, the second prism 20 uses blue light LB, and the third prism. 30 is configured to extract the red light LR. A green light reflecting dichroic film DG is formed as the first dichroic film, and a blue light reflecting dichroic film DB is formed as the second dichroic film. Also in this color separation optical system 1A-2, the green light reflection dichroic film DG and the blue light reflection dichroic film DB are made to be dichroic films having appropriate characteristics similarly to the color separation optical system 1A shown in FIG. A prism spectral characteristic approximate to the spectral characteristic shown in FIG. 5 can be obtained. In addition, it is possible to realize an imaging system having ideal spectral characteristics with reduced ghost and flare.

  FIG. 22 shows an example of the spectral transmission characteristics of the entire prism portion (the entire first, second and third prisms 10, 20, and 30) in the color separation optical system 1A-2. FIG. 23 shows film characteristics in a specific design example of the green light reflecting dichroic film DG and the blue light reflecting dichroic film DB in the color separation optical system 1A-2. The film characteristics shown in FIG. 23 are obtained, for example, by the film design specifically shown as numerical data in FIGS. However, the film substance, the number of layers, and the film thickness of each layer are not limited to the examples of FIGS. As can be seen from FIG. 22, in this color separation optical system 1A-2, characteristics equivalent to the spectral characteristics (FIG. 5) in the Philips configuration example are obtained.

Here, the configuration example in which the first prism 10 extracts the green light LG, the second prism 20 extracts the blue light LB, and the third prism 30 extracts the red light LR has been described. However, the first to third prisms 10 are described. , 20, and 30 are not limited to this. That is, for the other configuration examples of the Philips color separation optical system mentioned in the first and second embodiments, the first prism 10 and the second prism 10 are similar to the configuration example of FIG. A configuration in which the air gap 10AG between the prism 20 and the prism 20 is not provided can be employed.
[Fourth Embodiment]

  Next, a fourth embodiment of the present invention will be described. Note that components that are substantially the same as those in the first to third embodiments are denoted by the same reference numerals, and description thereof is omitted as appropriate.

  FIG. 26 shows a main configuration of an imaging apparatus including a color separation optical system 1B according to the fourth embodiment of the present invention. In the first to third embodiments, the example in which the incident light L is decomposed into the three color light components of the blue light LB, the red light LR, and the green light LG has been described. However, the color separation according to the present embodiment is described. The optical system 1B is a configuration example that decomposes into four color light components obtained by adding cyan as the fourth color light component.

  The color separation optical system 1B according to the present embodiment is a fourth prism 40 disposed between the second prism 20 and the third prism 30 with respect to the color separation optical system 1 shown in FIG. Is further provided. An image sensor 4C is provided on the light exit side of the fourth prism 40. The fourth prism 40 has a first surface 41, a second surface 42, and a third surface 43. The fourth prism 40 is arranged with a predetermined air interval with respect to the second prism 20. More specifically, the second surface 20 of the second prism 20 and the first surface 41 of the fourth prism 40 are arranged to face each other with an air space therebetween so as to be substantially parallel. The third surface 43 of the fourth prism 40 is a light exit surface. A trimming filter 54 is provided on the exit surface. Similar to the trimming filter 51 in the first prism 10, the trimming filter 54 is not provided with a dichroic film for characteristic adjustment. Instead, the trimming filter 54 has a light exit surface for preventing ghost and flare. An antireflection film 53AR is formed. Note that the antireflection film 53AR may be formed directly on the third surface 43 of the fourth prism 40 without providing the trimming filter 54.

  A cyan light reflecting dichroic film DC as a third dichroic film is formed on the second surface 22 of the fourth prism 40. The cyan light reflecting dichroic film DC has a film configuration that reflects cyan light LC as a fourth color light component and transmits green light LG. The cyan light reflecting dichroic film DC reflects a part of light in the cyan color region of 400 nm or more and 600 nm or less as the fourth color light component.

FIG. 27A is a specific design example of the blue light reflecting dichroic film DB, the red light reflecting dichroic film DR, and the cyan light reflecting dichroic film DC used in the color separation optical system 1B shown in FIG. The characteristics are shown. The characteristics of the blue light reflecting dichroic film DB and the red light reflecting dichroic film DR are the same as those in the color separation optical system 1 of FIG. 1 (FIG. 4). The characteristics of the cyan light reflecting dichroic film DC shown in FIG. 27A can be obtained by, for example, the film design specifically shown as numerical data in FIG. However, the film substance, the number of layers, and the film thickness of each layer are not limited to the example of FIG. In FIG. 27B, “Sub-H4” represents a substance H4 (manufactured by Merck & Co., Germany) whose main component is LaTiO ₃ .

  In the present embodiment, the third prism 30 is bonded to the fourth prism 40 via a cyan light reflecting dichroic film DC. More specifically, the second surface 42 of the fourth prism 40 and the first surface 31 of the third prism 30 are joined via a cyan light reflecting dichroic film DC. In the present embodiment, the third prism 30 is configured to take out green light that has passed through the blue light reflecting dichroic film DB and the red light reflecting dichroic film DR, and further has passed through the cyan light reflecting dichroic film DC.

In the image pickup apparatus including the color separation optical system 1B according to the present embodiment, four color light components obtained by adding cyan light LC as the fourth color light component in addition to the blue light LB, the red light LR, and the green light LG. By performing the imaging with, the ideal characteristics of the imaging system can be brought closer. In the ideal characteristics of the imaging system shown in FIG. 45, there are areas where the sensitivity is negative, and in particular, there are many areas where the red spectral characteristics are negative. This negative sensitivity region is difficult to reproduce by the usual three-color separation method. However, by acquiring the cyan light LC corresponding to the negative sensitivity region as the color light component, it is possible to reproduce the negative sensitivity portion by calculation on the imaging circuit side. That is, as shown in the following arithmetic expression, the characteristic value C obtained from the cyan light LC is appropriately optimized and subtracted from the characteristic value R obtained from the color-separated red light LR. A characteristic value R ′ that reproduces the sensitivity portion can be obtained.
R ′ = R−kC
However, k is an appropriate coefficient optimized to reproduce negative sensitivity.

Hereinafter, a design example in which negative sensitivity is actually reproduced will be described.
FIG. 28 shows the entire prism portion (first, second, third and fourth prisms 10, 20, 30) on which the film design shown in FIG. 27 is applied in the color separation optical system 1B according to the present embodiment. , 40 as a whole). FIG. 29 shows the overall spectral transmission characteristics of the entire optical system in the imaging apparatus, which combines the characteristics of the optical elements other than the prism section shown in FIG. 3 and the characteristics of the entire prism section shown in FIG. ing. In FIGS. 28 and 29, C indicates the spectral characteristics of cyan light LC.

  FIG. 30 shows characteristics obtained by normalizing the overall spectral transmission characteristics shown in FIG. FIG. 30 also shows ideal characteristics (B0, R0, G0) for comparison. Note that the ideal characteristics referred to here are those conventionally shown in FIG. In FIG. 30, B1, R1, G1, and C1 indicate characteristics directly obtained in the design example according to the present embodiment. In FIG. 30, C1 indicates the spectral characteristic of the cyan light LC. “R1-2C1” is a characteristic of R ′ obtained by the above-described optimized calculation. It can be seen that the characteristic of “R1-2C1” obtained by the calculation reproduces the negative sensitivity and is closer to the red ideal characteristic (R0).

  FIG. 31 is a u'v 'chromaticity diagram showing the color reproducibility in the design example according to the present embodiment in comparison with the conventional case, as in the case of FIG. In the figure, coordinate points indicated by black triangles “▲” represent coordinate points of an arbitrary color according to the conventional configuration. Coordinate points indicated by white squares “□” represent coordinate points of an arbitrary color in the design example according to the present embodiment. In the conventional configuration and the design example according to the present embodiment, the deviation amount from the ideal point (reproduction color deviation amount) is indicated by a solid line connecting the coordinate points. In the conventional configuration, the reproduced color protrudes in the upper right red region, but the design example according to the present embodiment is greatly improved. In the design example according to the present embodiment, as a whole balance, there is no place where the color moves from the ideal point and the color reproducibility is improved. In particular, the color reproducibility in cyan is improved. The average color difference of the seven colors B (blue), G (green), R (red), C (cyan), Y (yellow), M (magenta), and skin (skin color) is 8.84 to 5.96. Improved.

As described above, according to the color separation optical system 1B and the imaging apparatus according to the present embodiment, the fourth color light component is obtained. Therefore, the color separation optical system 1 according to the first embodiment is obtained. In addition, the color reproducibility can be further improved as compared with the imaging device.
[Fifth Embodiment]

  Next, a fifth embodiment of the present invention will be described. Note that components that are substantially the same as those in the first to fourth embodiments are given the same reference numerals, and descriptions thereof are omitted as appropriate.

  In each of the above embodiments, the characteristics of the dichroic film are designed to approximate the ideal characteristics shown in FIG. 45. However, in this embodiment, the ideal characteristics are obtained by further linearly transforming the ideal characteristics. The film design is performed using the spectral characteristics. This primary conversion is converted from the ideal characteristic itself shown by the color matching function of the RGB color system or the chromaticity coordinates of the three primary colors of the color reproduction medium, and the ideal shown by the primary conversion of the color matching function of the XYZ color system. This characteristic is obtained by performing a primary transformation that further reduces the negative value.

  FIG. 32A shows ideal spectral characteristics R (x), G (x), and B (x) before performing the primary conversion. This is substantially the same as the ideal characteristic shown in FIG. FIG. 32B shows conversion characteristics R ′ (x), G ′ (x), and B ′ obtained by linearly converting the ideal characteristics R (x), G (x), and B (x) of FIG. (X) is shown. Further, FIG. 33 shows characteristics obtained by standardizing the conversion characteristics R ′ (x), G ′ (x), and B ′ (x) of FIG. An example of this primary conversion operation is shown in [Equation 1]. M is a matrix that minimizes negative values as much as possible for the conversion characteristics R ′ (x), G ′ (x), and B ′ (x).

Here, by multiplying R ′ (x), G ′ (x), B ′ (x) by the inverse matrix M ⁻¹ , the original ideal characteristics R (x), G (x), B (x) are obtained. An approximate characteristic can be obtained. In each configuration example in the first and second embodiments, the characteristics of the dichroic film are represented by R ′ (x), G ′ (x), and B ′ (x) as ideal characteristics (standardized conversion ideals). The characteristics are approximated to R ′ (x), G ′ (x), and B ′ (x). Thereafter, the characteristics approximated to the original ideal characteristics R (x), G (x), and B (x) can be obtained by multiplying the inverse matrix M ⁻¹ by the calculation in the calculation circuit on the imaging apparatus side. . Here, since R ′ (x), G ′ (x), and B ′ (x) have such characteristics that negative values are reduced as much as possible, even if the color separation is performed for three colors, R ′. Reproduction of (x), G ′ (x), B ′ (x) is possible. The reproduced characteristics of R ′ (x), G ′ (x), and B ′ (x) are inversely calculated as described above in the arithmetic circuit on the imaging apparatus side, so that the original ideal characteristics R (x), G ( The characteristics approximated to x) and B (x) can be obtained. That is, even if the color separation of the three colors is performed, the negative sensitivity portion can be virtually reproduced.

  FIG. 34 shows a blue light reflecting dichroic film DB and red light that are designed with the conversion characteristics R ′ (x), G ′ (x), and B ′ (x) of FIG. 33 as ideal characteristics in the configuration example of FIG. The specific characteristic of the reflective dichroic film DR is shown.

  FIG. 35 shows the overall spectral transmission characteristics (B1, R1, G1) of the entire optical system in the imaging apparatus having the color separation optical system with the film design shown in FIG. FIG. 35 also shows ideal characteristics (B0, R0, G0) for comparison. The ideal characteristic here is the conversion ideal characteristic shown in FIG.

  FIG. 36 shows conversion characteristics (B1, R1, G1) obtained by further optimizing the characteristics in the design example shown in FIG. 35 by the inverse operation described above. FIG. 36 also shows ideal characteristics (B0, R0, G0) for comparison. The ideal characteristic here is a conventionally known characteristic shown in FIG. 45 (the above-described normal ideal characteristic before the primary conversion). As described above, according to the present embodiment, a negative sensitivity portion can be virtually reproduced without performing the four-color separation as in the fourth embodiment, and a characteristic close to a normal ideal characteristic is obtained. It is done.

  FIG. 37 is a u'v 'chromaticity diagram showing the color reproducibility in the design example according to the present embodiment in comparison with the conventional case, as in the case of FIG. In the figure, coordinate points indicated by black triangles “▲” represent coordinate points of an arbitrary color according to the conventional configuration. Coordinate points indicated by white squares “□” represent coordinate points of an arbitrary color in the design example according to the present embodiment. In the conventional configuration and the design example according to the present embodiment, the deviation amount from the ideal point (reproduction color deviation amount) is indicated by a solid line connecting the coordinate points. In the design example according to the present embodiment, the color reproducibility can be further improved as compared with the case where the film design based on the normal ideal characteristics shown in the first embodiment is performed. In particular, the color reproducibility in the cyan and green portions was stable. The average color difference for the seven colors B (blue), G (green), R (red), C (cyan), Y (yellow), M (magenta), and skin (skin color) is 8.84 to 2.95. Improved. The average color difference in the first embodiment shown in FIG. 8 is 7.37, and the average color difference can be further reduced.

Note that the present embodiment can be similarly applied to the respective modifications of the first embodiment. The present invention can be similarly applied to the configurations of the second and third embodiments. FIG. 38 shows a film configuration example of the dichroic film when applied to the configuration of the second embodiment. Instead of the film configuration shown in FIG. 19, a film configuration with the characteristics shown in FIG. 38 may be used.
[Sixth Embodiment]

  Next, a sixth embodiment of the present invention will be described. Note that components that are substantially the same as those in the first to fifth embodiments are given the same reference numerals, and descriptions thereof are omitted as appropriate.

  FIG. 39 shows the configuration of a color separation optical system 1A-3 according to the sixth embodiment of the present invention. The color separation optical system 1A-3 further includes a depolarization plate 55 disposed on the front side of the first prism 10 with respect to the color separation optical system 1A-2 shown in FIG. Other configurations are the same as those of the color separation optical system 1A-2 shown in FIG. The depolarization plate 55 is for depolarizing incident light in a specific direction.

  FIG. 40 shows an example of spectral transmission characteristics for each polarization component in the entire prism portion (the entire first, second and third prisms 10, 20, and 30) when the depolarization plate 55 is not provided. Yes. For example, when the incident light component is biased toward a specific linearly polarized light component, the spectral characteristics change as compared to the case where the incident light is in a non-polarized state. FIG. 40 shows the characteristics when linearly polarized light components (P-polarized light and S-polarized light) orthogonal to each other are incident as incident light. The characteristic when the incident light is non-polarized light is shown as (P + S) / 2. In the present embodiment, the depolarization plate 55 is disposed in front of the first prism 10, so that the polarization of incident light in a specific direction is eliminated, and is indicated by (P + S) / 2 in FIG. Such stable spectral characteristics can be obtained.

Similarly, in each configuration example in each of the other embodiments, the depolarization plate 55 may be provided in front of the first prism 10.
[Seventh Embodiment]

  Next, a seventh embodiment of the present invention will be described. Note that components that are substantially the same as those in the first to sixth embodiments are denoted by the same reference numerals, and description thereof is omitted as appropriate.

  FIG. 41 shows the configuration of a color separation optical system 1A-4 according to the seventh embodiment of the present invention. This color separation optical system 1A-4 is arranged on the exit surface side of a prism (third prism 30 in the arrangement example of FIG. 41) that extracts red light with respect to the color separation optical system 1A-2 shown in FIG. The characteristics of the trimming filter 53 ′ are characteristics of an absorption filter that blocks blue light and green light and transmits red light. Other configurations are the same as those of the color separation optical system 1A-2 shown in FIG.

  FIG. 42 shows the overall spectral transmission characteristics of the entire imaging optical system when the color separation optical system 1A-4 is applied to an imaging apparatus (characteristics indicated by R, G, and B in the figure). . FIG. 42 also shows the characteristics when the characteristics of the trimming filter 53 ′ are not the characteristics of the absorption filter that blocks blue light and green light for comparison (characteristics of solid line (TMRless) in the figure). . If the absorption filter characteristics are not satisfied, blue light and green light leak into the red image sensor 4R and unnecessary components are mixed, resulting in poor color reproducibility. In the present embodiment, by arranging the trimming filter 53 ′ having the absorption filter characteristic that blocks blue light and green light on the exit surface side of the prism that extracts red light, leakage of unnecessary components is prevented, Color reproducibility can be improved.

  Similarly, in each configuration example in each of the other embodiments, an absorption filter 56 may be provided on the exit surface side of the prism that extracts red light.

It is sectional drawing which shows the example of 1 structure of the imaging device provided with the color separation optical system which concerns on the 1st Embodiment of this invention. It is explanatory drawing about the characteristic (A) of the blue light reflection dichroic film | membrane DB used with the color separation optical system shown in FIG. 1, and the characteristic (B) of the red light reflection dichroic film | membrane DR. It is a characteristic view which shows the spectral characteristics of optical elements other than the prism part in the imaging device which concerns on the 1st Embodiment of this invention. FIG. 2 is a characteristic diagram showing a design example of a blue light reflecting dichroic film DB and a red light reflecting dichroic film DR used in the color separation optical system shown in FIG. 1. It is a characteristic view which shows the spectral characteristic of the prism part in the imaging device which concerns on the 1st Embodiment of this invention. It is a characteristic view which shows the comprehensive spectral characteristic of the optical system in the imaging device which concerns on the 1st Embodiment of this invention. FIG. 5 is a characteristic diagram showing normalized overall spectral characteristics in the first embodiment of the present invention compared with ideal characteristics and conventional characteristics. FIG. 5 is a u′v ′ chromaticity diagram showing the color reproducibility in the first embodiment of the present invention in comparison with the prior art. FIG. 5 is a characteristic diagram showing the amount of ghost generation in the color separation optical system according to the first embodiment of the present invention compared to the conventional art. It is a figure which shows the numerical example of the film | membrane design of the blue light reflection dichroic film | membrane DB used with the color separation optical system shown in FIG. It is a figure which shows the numerical example of the film | membrane design of the red light reflection dichroic film | membrane DR used with the color separation optical system shown in FIG. It is sectional drawing which shows the 1st modification of the imaging device provided with the color separation optical system which concerns on the 1st Embodiment of this invention. It is explanatory drawing about the characteristic (A) of the blue light reflection dichroic film | membrane DB used with the color separation optical system shown in FIG. 12, and the characteristic (B) of the green light reflection dichroic film | membrane DG. It is sectional drawing which shows the 2nd modification of the imaging device provided with the color separation optical system which concerns on the 1st Embodiment of this invention. It is sectional drawing which shows the 3rd modification of the imaging device provided with the color separation optical system which concerns on the 1st Embodiment of this invention. FIG. 16 is an explanatory diagram of a characteristic (A) of a green light reflecting dichroic film DG and a characteristic (B) of a red light reflecting dichroic film DR used in the color separation optical system shown in FIG. 15. It is sectional drawing which shows the example of 1 structure of the imaging device provided with the color separation optical system which concerns on the 2nd Embodiment of this invention. It is explanatory drawing about the characteristic (A) of the short wavelength side of the green light reflection dichroic film | membrane DG used with the color separation optical system which concerns on the 2nd Embodiment of this invention, and the characteristic (B) of the long wavelength side. It is a characteristic view which shows the example of a design of the dichroic film | membrane used with the color separation optical system which concerns on the 2nd Embodiment of this invention. It is sectional drawing which shows the modification of the imaging device provided with the color separation optical system which concerns on the 2nd Embodiment of this invention. It is sectional drawing which shows the example of 1 structure of the imaging device provided with the color separation optical system which concerns on the 3rd Embodiment of this invention. It is a characteristic view which shows the spectral characteristic of the prism part in the imaging device which concerns on the 3rd Embodiment of this invention. It is a characteristic view which shows the example of a design of the dichroic film | membrane used with the color separation optical system concerning the 3rd Embodiment of this invention. It is a figure which shows the specific numerical example which implement | achieves the characteristic of the green light reflection dichroic film | membrane DG shown in FIG. It is a figure which shows the specific numerical example which implement | achieves the characteristic of the blue light reflection dichroic film | membrane DB shown in FIG. It is sectional drawing which shows the example of 1 structure of the imaging device provided with the color separation optical system which concerns on the 4th Embodiment of this invention. It is a figure which shows an example of the characteristic figure and example of film | membrane data which show the design example of the dichroic film | membrane used with the color separation optical system which concerns on the 4th Embodiment of this invention. It is a characteristic view which shows the spectral characteristics of the prism part in the imaging device which concerns on the 4th Embodiment of this invention. It is a characteristic view which shows the comprehensive spectral characteristic of the optical system in the imaging device which concerns on the 4th Embodiment of this invention. It is the characteristic view which showed the standardized comprehensive spectral characteristic in the 4th Embodiment of this invention compared with the ideal characteristic and the conventional characteristic. FIG. 10 is a u′v ′ chromaticity diagram showing color reproducibility in a fourth embodiment of the present invention in comparison with the prior art. It is explanatory drawing about the ideal characteristic applied with the color separation optical system which concerns on the 5th Embodiment of this invention, (A) shows the ideal characteristic before conversion, (B) is the ideal characteristic after conversion. Indicates. It is a characteristic view which shows the normalized ideal characteristic applied with the color separation optical system which concerns on the 5th Embodiment of this invention. It is a characteristic view showing a design example of a blue light reflecting dichroic film DB and a red light reflecting dichroic film DR used in a color separation optical system according to a fifth embodiment of the present invention. FIG. 10 is a characteristic diagram showing the normalized overall spectral characteristic in the fifth embodiment of the present invention compared with the ideal characteristic subjected to the primary conversion. FIG. 36 is a characteristic diagram obtained by inversely transforming the normalized overall spectral characteristic in the fifth embodiment shown in FIG. 35 and comparing it with an ideal characteristic. FIG. 10 is a u′v ′ chromaticity diagram showing color reproducibility in a fifth embodiment of the present invention in comparison with the prior art. It is a characteristic view which shows the other structural example of the dichroic film | membrane used with the color separation optical system concerning the 5th Embodiment of this invention. It is sectional drawing which shows the example of 1 structure of the imaging device provided with the color separation optical system which concerns on the 6th Embodiment of this invention. It is a characteristic view which shows the spectral characteristic of the prism part in the imaging device which concerns on the 6th Embodiment of this invention. It is sectional drawing which shows one structural example of the imaging device provided with the color separation optical system which concerns on the 7th Embodiment of this invention. It is a characteristic view which shows the standardized comprehensive spectral characteristic in the imaging device which concerns on the 7th Embodiment of this invention. It is sectional drawing which shows the structural example of the conventional color separation optical system. It is an xy chromaticity diagram showing chromaticity coordinates of three primary colors for obtaining ideal characteristics. It is a characteristic view which shows the normalized ideal characteristic. It is a characteristic view which shows the spectral characteristic of the conventional general color separation optical system. It is a characteristic view which shows an example of the characteristic of the dichroic film | membrane used with the conventional color separation optical system. It is a characteristic view which shows the spectral characteristic approximated to the ideal characteristic in the conventional color separation optical system. It is explanatory drawing about the multiple reflection which arises in the conventional color separation optical system.

Explanation of symbols

  L ... incident light, LB ... blue light component, LR ... red light component, LG ... green light component, DB ... blue light reflecting dichroic film, DR ... red light reflecting dichroic film, DG ... green light reflecting dichroic film, DC ... cyan Color light reflecting dichroic film, 1,1-1,1-2,1-3,1A1,1A-1,1A-2,1A-3,1A-4,1B ... color separation optical system, 2 ... photographing lens, 3 ... IR cut filter, 4R, 4G, 4B, 4C ... imaging device, 10 ... first prism, 20 ... second prism, 30 ... third prism, 40 ... fourth prism, 51 ... first trimming Filter 52. Second trimming filter 53. Third trimming filter 51 AR First antireflection film 52 AR Second antireflection film 53 AR Third antireflection film 54 AR Fourth Anti-reflective Film, 55 ... depolarizer.

Claims (30)

A color separation optical system that decomposes incident light into at least three color light components of blue light, red light, and green light,
In order from the light incident side,
A first prism that has a first dichroic film and extracts a first color light component reflected by the first dichroic film;
A second prism that has a second dichroic film and extracts a second color light component transmitted through the first dichroic film and reflected by the second dichroic film;
And a third prism for extracting a third color light component that has passed through the first and second dichroic films,
The first dichroic film is configured to reflect blue light as the first color light component, and the second dichroic film reflects red light or green light as the second color light component. A film configuration, and
The slope of the transmission characteristic curve indicating the transmittance with respect to the wavelength of the first dichroic film has a shape along the characteristic curve on the short wavelength side of the ideal green spectral characteristic,
When the second dichroic film reflects red light, the slope of the transmission characteristic curve indicating the transmittance with respect to the wavelength of the dichroic film is the characteristic curve on the long wavelength side of the ideal green spectral characteristic. Has a shape along
When the second dichroic film reflects green light, the slope of the reflection characteristic curve indicating the reflectance with respect to the wavelength of the dichroic film is the characteristic curve on the long wavelength side of the ideal green spectral characteristic. A color separation optical system characterized by having a shape along. The first prism extracts blue light, the second prism extracts red light, and the third prism extracts green light.
The first dichroic film reflects blue light, and the slope of the transmission characteristic curve of the dichroic film is 430 nm or more and 670 nm or less in a form along the characteristic curve on the short wavelength side of the ideal green spectral characteristic. Has a shape that changes from low transmittance to high transmittance within the wavelength range of
The second dichroic film reflects red light, and the slope of the transmission characteristic curve of the dichroic film is 430 nm or more and 670 nm or less in the form of the characteristic curve on the long wavelength side of the ideal green spectral characteristic. 2. The color separation optical system according to claim 1, wherein the color separation optical system is configured to have a shape that changes from a high transmittance to a low transmittance within the wavelength range. Average slope in which the transmission characteristic curve of the first dichroic film reflecting blue light changes from 20% to 80% of the range between the lowest transmittance and the highest transmittance within a wavelength range of 430 nm to 670 nm. The shape has a value of 0.2 (% / nm) or more and 2.0 (% / nm) or less,
Average slope in which the transmission characteristic curve of the second dichroic film reflecting red light changes from 80% to 20% of the range between the highest transmittance and the lowest transmittance within a wavelength range of 430 nm to 670 nm. The color separation optical system according to claim 2, wherein the color separation optical system is configured to have a shape having a value of −2.0 (% / nm) or more and −0.2 (% / nm) or less. A fourth prism having a third dichroic film, which is arranged between the second prism and the third prism and extracts a fourth color light component transmitted through the first and second dichroic films; Further comprising
The third dichroic film reflects a part of light in a wavelength range of 400 nm to 600 nm as the fourth color light component,
The third prism is configured to take out green light that has passed through the first and second dichroic films and further has passed through the third dichroic film. The color separation optical system described. The first prism extracts blue light, the second prism extracts green light, and the third prism extracts red light.
The first dichroic film reflects blue light, and the slope of the transmission characteristic curve of the dichroic film is 430 nm or more and 670 nm or less in a form along the characteristic curve on the short wavelength side of the ideal green spectral characteristic. Has a shape that changes from low transmittance to high transmittance within the wavelength range of
The second dichroic film reflects green light, and the slope of the reflection characteristic curve of the dichroic film is 430 nm or more and 670 nm or less in the form of the characteristic curve on the long wavelength side of the ideal green spectral characteristic. 2. The color separation optical system according to claim 1, wherein the color separation optical system has a shape that changes from a high reflectance to a low reflectance within a wavelength range of 2. Average slope in which the transmission characteristic curve of the first dichroic film reflecting blue light changes from 20% to 80% of the range between the lowest transmittance and the highest transmittance within a wavelength range of 430 nm to 670 nm. The shape has a value of 0.2 (% / nm) or more and 2.0 (% / nm) or less,
The average slope at which the reflection characteristic curve of the second dichroic film reflecting green light changes from 80% to 20% of the range between the highest reflectance and the lowest reflectance within the wavelength range of 430 nm to 670 nm. The color separation optical system according to claim 5, wherein the color separation optical system has a shape having a value of −2.0 (% / nm) or more and −0.2 (% / nm) or less. A color separation optical system that decomposes incident light into at least three color light components of blue light, red light, and green light,
In order from the light incident side,
A first prism that has a first dichroic film and extracts a first color light component reflected by the first dichroic film;
A second prism that has a second dichroic film and extracts a second color light component transmitted through the first dichroic film and reflected by the second dichroic film;
And a third prism for extracting a third color light component that has passed through the first and second dichroic films,
The first dichroic film is configured to reflect red light as the first color light component, and the second dichroic film reflects blue light or green light as the second color light component. A film configuration, and
The slope of the transmission characteristic curve indicating the transmittance with respect to the wavelength of the first dichroic film has a shape along the characteristic curve on the long wavelength side of the ideal green spectral characteristic,
When the second dichroic film reflects blue light, the slope of the transmission characteristic curve indicating the transmittance with respect to the wavelength of the dichroic film becomes a characteristic curve on the short wavelength side of the ideal green spectral characteristic. Has a shape along
When the second dichroic film reflects green light, the slope of the reflection characteristic curve indicating the reflectance with respect to the wavelength of the dichroic film is the characteristic curve on the short wavelength side of the ideal green spectral characteristic. A color separation optical system characterized by having a shape along. The first prism extracts red light, the second prism extracts blue light, and the third prism extracts green light.
The first dichroic film reflects red light, and the slope of the transmission characteristic curve of the dichroic film is 430 nm or more and 670 nm or less in the form of the characteristic curve on the long wavelength side of the ideal green spectral characteristic. Having a shape that falls from high transmittance to low transmittance within the wavelength range of
The second dichroic film reflects blue light, and the slope of the transmission characteristic curve of the dichroic film is 430 nm or more and 670 nm or less in the form of the characteristic curve on the short wavelength side of the ideal green spectral characteristic. The color separation optical system according to claim 7, wherein the color separation optical system has a shape that rises from a low transmittance to a high transmittance within a wavelength range of. Average slope in which the transmission characteristic curve of the first dichroic film reflecting red light changes from 80% to 20% of the range between the highest transmittance and the lowest transmittance within the wavelength range of 430 nm to 670 nm. The shape has a value of −2.0 (% / nm) or more and −0.2 (% / nm) or less,
Average slope in which the transmission characteristic curve of the second dichroic film reflecting blue light changes from 20% to 80% of the range between the lowest transmittance and the highest transmittance within the wavelength range of 430 nm to 670 nm. The color separation optical system according to claim 8, wherein the color separation optical system has a shape having a value of 0.2 (% / nm) to 2.0 (% / nm). The first prism extracts red light, the second prism extracts green light, and the third prism extracts blue light.
The first dichroic film reflects red light, and the slope of the transmission characteristic curve of the dichroic film is 430 nm or more and 670 nm or less in the form of the characteristic curve on the long wavelength side of the ideal green spectral characteristic. Having a shape that falls from high transmittance to low transmittance within the wavelength range of
The second dichroic film reflects green light, and the slope of the reflection characteristic curve of the dichroic film is 430 nm or more and 670 nm or less in a form along the characteristic curve on the short wavelength side of the ideal green spectral characteristic. The color separation optical system according to claim 7, wherein the color separation optical system has a shape that rises from a low reflectance to a high reflectance within the wavelength range. Average slope in which the transmission characteristic curve of the first dichroic film reflecting red light changes from 80% to 20% of the range between the highest transmittance and the lowest transmittance within the wavelength range of 430 nm to 670 nm. The shape has a value of −2.0 (% / nm) or more and −0.2 (% / nm) or less,
The average slope at which the reflection characteristic curve of the second dichroic film reflecting green light changes from 20% to 80% of the range between the lowest reflectance and the highest reflectance within the wavelength range of 430 nm to 670 nm. The color separation optical system according to claim 10, wherein the color separation optical system has a shape having a value of 0.2 (% / nm) or more and 2.0 (% / nm) or less. A color separation optical system that decomposes incident light into at least three color light components of green light, blue light, and red light,
In order from the light incident side,
A first prism that has a first dichroic film and extracts a first color light component reflected by the first dichroic film;
A second prism that has a second dichroic film and extracts a second color light component transmitted through the first dichroic film and reflected by the second dichroic film;
And a third prism for extracting a third color light component that has passed through the first and second dichroic films,
The first dichroic film is configured to reflect green light as the first color light component, and the second dichroic film reflects blue light or red light as the second color light component. A film configuration, and
The slope of the reflection characteristic curve indicating the reflectance with respect to the wavelength of the first dichroic film has a shape along the characteristic curve on the short wavelength side and the long wavelength side of the ideal green spectral characteristic. Color separation optical system. In the portion where the slope of the reflection characteristic curve of the first dichroic film rises within the wavelength range of 430 nm or more and 670 nm or less, from the low reflectance in the form of the characteristic curve on the short wavelength side of the ideal green spectral characteristic. It has a shape that changes to high reflectivity,
The portion falling within the wavelength range of 430 nm to 670 nm has a shape that changes from a high reflectance to a low reflectance along the characteristic curve on the long wavelength side of the ideal green spectral characteristic. The color separation optical system according to claim 12. In the portion where the reflection characteristic curve of the first dichroic film changes from 20% to 80% of the range between the lowest reflectance and the highest reflectance within the wavelength range of 430 nm to 670 nm, the average slope value is 0. .2 (% / nm) or more and 2.0 (% / nm) or less,
Within the wavelength range of 430 nm or more and 670 nm or less, the average slope value is −2.0 (% / nm) or more and −0. The color separation optical system according to claim 13, wherein the color separation optical system has a shape of 2 (% / nm) or less. The first prism extracts green light, the second prism extracts blue light, and the third prism extracts red light.
The second dichroic film is configured to reflect blue light, and the slope of the transmission characteristic curve indicating the transmittance with respect to the wavelength of the dichroic film follows the characteristic curve on the short wavelength side of the ideal red spectral characteristic The color separation optical system according to claim 13 or 14, characterized by comprising: The first prism extracts green light, the second prism extracts red light, and the third prism extracts blue light.
The second dichroic film is configured to reflect red light, and the slope of the reflection characteristic curve indicating the reflectance with respect to the wavelength of the dichroic film is a shape that follows the characteristic curve on the short wavelength side of the ideal red spectral characteristic The color separation optical system according to claim 13 or 14, characterized by comprising: The color separation optical system according to claim 1, wherein the ideal spectral characteristic is an ideal characteristic represented by a color matching function of an RGB color system. The ideal spectral characteristic is an ideal characteristic that is converted from chromaticity coordinates of three primary colors of a color reproduction medium and is represented by a linear transformation of a color matching function of an XYZ color system. The color separation optical system according to any one of the above. The color separation optical according to claim 17 or 18, wherein the ideal spectral characteristic is a characteristic obtained by performing a conversion that can be inversely converted so as to further reduce a negative value with respect to the ideal characteristic. system. 2. An absorptive filter disposed on at least one of a front side of the first prism or an exit surface side of a prism for extracting red light and having characteristics approximating a visual sensitivity. 20. The color separation optical system according to any one of 19 above. 20. The color separation optical according to claim 1, further comprising a coat type infrared cut filter that is disposed in front of the first prism and cuts infrared light. system. The color separation optical system according to any one of claims 1 to 19, further comprising an ultraviolet cut filter that is disposed in front of the first prism and blocks ultraviolet light. The color separation optical system according to any one of claims 1 to 19, wherein an antireflection film is provided on an exit surface of at least one prism. The color separation according to any one of claims 1 to 19, further comprising a depolarization plate that is disposed in front of the first prism and depolarizes incident light in a specific direction. Optical system. 20. The apparatus according to claim 1, further comprising an absorption filter that is disposed on an exit surface side of the prism that extracts red light, blocks blue light and green light, and transmits red light. Color separation optical system. A color separation optical system that decomposes incident light into at least three color light components of blue light, red light, and green light,
In order from the light incident side,
A first prism that has a first dichroic film and extracts a first color light component reflected by the first dichroic film;
A second prism that has a second dichroic film and extracts a second color light component transmitted through the first dichroic film and reflected by the second dichroic film;
And a third prism for extracting a third color light component that has passed through the first and second dichroic films,
The first dichroic film is configured to reflect blue light as the first color light component, and the second dichroic film reflects red light or green light as the second color light component. A film configuration, and
The slope of the transmission characteristic curve indicating the transmittance with respect to the wavelength of the first dichroic film has a shape substantially equal to the characteristic curve on the short wavelength side of the ideal green spectral characteristic,
When the second dichroic film reflects red light, the slope of the transmission characteristic curve indicating the transmittance with respect to the wavelength of the dichroic film is the characteristic curve on the long wavelength side of the ideal green spectral characteristic. Have substantially the same shape,
When the second dichroic film reflects green light, the slope of the reflection characteristic curve indicating the reflectance with respect to the wavelength of the dichroic film is the characteristic curve on the long wavelength side of the ideal green spectral characteristic. Have approximately the same shape A color separation optical system that decomposes incident light into at least three color light components of blue light, red light, and green light,
In order from the light incident side,
A first prism that has a first dichroic film and extracts a first color light component reflected by the first dichroic film;
A second prism that has a second dichroic film and extracts a second color light component transmitted through the first dichroic film and reflected by the second dichroic film;
And a third prism for extracting a third color light component that has passed through the first and second dichroic films,
The first dichroic film is configured to reflect red light as the first color light component, and the second dichroic film reflects blue light or green light as the second color light component. A film configuration, and
The slope of the transmission characteristic curve indicating the transmittance with respect to the wavelength of the first dichroic film has a shape substantially equal to the characteristic curve on the long wavelength side of the ideal green spectral characteristic,
When the second dichroic film reflects blue light, the slope of the transmission characteristic curve indicating the transmittance with respect to the wavelength of the dichroic film becomes a characteristic curve on the short wavelength side of the ideal green spectral characteristic. Have substantially the same shape,
When the second dichroic film reflects green light, the slope of the reflection characteristic curve indicating the reflectance with respect to the wavelength of the dichroic film is the characteristic curve on the short wavelength side of the ideal green spectral characteristic. A color separation optical system characterized by having substantially the same shape. A color separation optical system that decomposes incident light into at least three color light components of green light, blue light, and red light,
In order from the light incident side,
A first prism that has a first dichroic film and extracts a first color light component reflected by the first dichroic film;
A second prism that has a second dichroic film and extracts a second color light component transmitted through the first dichroic film and reflected by the second dichroic film;
And a third prism for extracting a third color light component that has passed through the first and second dichroic films,
The first dichroic film is configured to reflect green light as the first color light component, and the second dichroic film reflects blue light or red light as the second color light component. A film configuration, and
The slope of the reflection characteristic curve indicating the reflectance with respect to the wavelength of the first dichroic film has a shape substantially equal to the characteristic curve on the short wavelength side and the long wavelength side of the ideal green spectral characteristic. Color separation optical system. A color separation optical system according to any one of claims 1 to 28;
An image pickup apparatus comprising: an image pickup device provided corresponding to each color light separated by the color separation optical system and outputting an electrical signal corresponding to each incident color light. The color separation optical system according to claim 19,
An image sensor that is provided corresponding to each color light separated by the color separation optical system according to claim 19 and that outputs an electrical signal corresponding to each incident color light;
30. The imaging apparatus according to claim 29, further comprising: an arithmetic circuit that performs an inverse transformation to reproduce a negative value in the ideal characteristic based on a signal value obtained by the imaging element.

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