JP2004289545A - Color separation optical system and image pickup device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a color separation optical system easily usable for infrared light at a low cost. <P>SOLUTION: Three prisms include, from the side for receiving incident light, a first prism 3R for red wavelength range light, a second prism 3B for blue wavelength range light and a third prism 3G for green wavelength range light. A dichroic film 4R for reflecting a region including the red wavelength range light and the infrared region light is provided on the first prism 3R. A dichroic film 4B for reflecting a region including the blue wavelength range light is provided on the second prism 3B. The optical system is for use of visible light by installing an infrared light cut filter 2, and for use of the infrared light by removing the cut filter 2. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a color separation optical system for separating incident light from a subject condensed by a lens into three primary color lights of red (R), green (G), and blue (B), and an imaging apparatus using the same. About.
[0002]
[Prior art]
2. Description of the Related Art An imaging apparatus such as a television camera includes a color separation optical system that uses three prisms for R, G, and B to separate incident light from a subject condensed by a lens into three primary color lights. . In this color separation optical system, R, G, and B are selectively reflected or transmitted by a dichroic film to obtain R, G, and B light (Patent Document 1). In Patent Document 1, three prisms for R, G, and B are arranged in the order of B, R, and G from the light incident side.
[0003]
The R, G, and B lights separated by the color separation optical system are each photoelectrically converted by a solid-state imaging device (CCD, C-MOS, or the like). Various signal processing is performed on the electric signals obtained from the respective solid-state imaging devices to generate, for example, a composite color video signal of the NTSC system. Since the solid-state imaging device has high sensitivity up to the infrared region, an infrared light cut filter is disposed in front of the prism to block the infrared region and improve color reproducibility.
[0004]
[Patent Document 1]
JP 2001-78216 A
[Problems to be solved by the invention]
Taking advantage of the characteristic of the solid-state imaging device having high sensitivity up to the infrared region, it is conceivable to remove the infrared light cut filter to obtain an infrared light imaging device. If an image pickup apparatus for infrared light is to be constructed using a color separation optical system in which three prisms are arranged in the order of B, R, and G as described in Patent Document 1, the first prism is B Therefore, it is necessary to extend the suppression characteristic on the long wavelength side of the dichroic film for B to the infrared region (900 nm or more). In this case, the number of layers of the dichroic film to be deposited is required to be 40 or more, the cost is increased, and the properties of the glass material of the prism may be deteriorated.
[0006]
The present invention has been made in view of such a problem, and an object of the present invention is to provide a color separation optical system that can be easily used for infrared light at low cost. It is another object of the present invention to provide an image pickup device that can be used for both visible light and infrared light and that is used for both visible light and infrared light.
[0007]
[Means for Solving the Problems]
The present invention has been made to solve the above-mentioned problems of the related art.
(A) In a color separation optical system that separates incident light into three primary color lights, a first prism (3R) for red wavelength light arranged in order from the side where the incident light is incident, a first prism for blue wavelength light. And two prisms (3B) and a third prism (3G) for green wavelength region light, and a region provided on the first prism and reflecting a region including red wavelength region light and infrared region light. A first dichroic film (4R), and a second dichroic film (4B) provided on the second prism and reflecting a region containing blue wavelength region light. Provide resolution optics,
(B) In an imaging apparatus for imaging incident light from a subject condensed by an imaging lens (1), a first prism (3R) for red wavelength light arranged in order from the imaging lens side; Three prisms including a second prism (3B) for light and a third prism (3G) for green wavelength light, and three prisms provided in the first prism, for red light and infrared light. A first dichroic film (4R) that reflects an area including the light, a second dichroic film (4B) provided on the second prism and reflecting an area including light in the blue wavelength range, It is an object of the present invention to provide an imaging apparatus characterized by comprising a detachable infrared light cut filter (2) disposed between the first prism and the first prism.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a color separation optical system according to the present invention and an imaging apparatus using the same will be described with reference to the accompanying drawings. FIG. 1 is a plan view showing an embodiment of a color separation optical system of the present invention and an image pickup apparatus using the same, FIG. 2 is a diagram showing reflection spectral characteristics of a dichroic film for R in the present invention, and FIG. FIG. 4 is a diagram showing the reflection spectral characteristics of the dichroic film for B in FIG. 4, FIG. 4 is a diagram showing the transmission spectral characteristics of the G prism in the present invention, and FIG. 5 is a diagram showing the overall spectral characteristics in the present invention.
[0009]
In FIG. 1, incident light indicated by a solid line from a subject condensed by a photographing lens 1 is incident on an R first prism 3R. An infrared cut filter 2 is selectively disposed between the taking lens 1 and the first prism 3R. That is, when the color separation optical system and the imaging device of the present invention are used for visible light, the infrared light cut filter 2 is used. The infrared light cut filter 2 is detachable. When the color separation optical system and the imaging device of the present invention are used for infrared light, the infrared light cut filter 2 is removed and a dummy filter (not shown) is used. ).
[0010]
The infrared light cut filter 2 and the dummy filter are arranged on a rectangular plate, and the plate is slid to switch between the infrared light cut filter 2 and the dummy filter. The infrared light cut filter 2 and the dummy filter may be switched by arranging the dummy filter 2 and the dummy filter and rotating the disk.
[0011]
The second prism 3B for B is joined to the first prism 3R via a minutely spaced air layer (not shown). An R dichroic film 4R is laminated on the reflection surface of the first prism 3R on the side of the second prism 3B. FIG. 2 shows the reflection spectral characteristics of the dichroic film 4R. As shown in FIG. 2, the reflection spectral characteristics of the dichroic film 4R extend not only in the red wavelength region but also in the long wavelength region to the infrared region (900 nm or more), and in the short wavelength region around 400 nm (equivalent to blue). ).
[0012]
When the infrared light cut filter 2 is not provided, the red wavelength region light and the infrared region light (infrared light) of the incident light are reflected by the dichroic film 4R and totally reflected by the front surface 3R1 of the first prism 3R. . When the infrared light cut filter 2 is provided, only the red wavelength region light is reflected by the dichroic film 4R and totally reflected by the front surface 3R1 of the first prism 3R. An R trimming filter 5R for removing extra color components is joined to the light exit surface of the first prism 3R.
[0013]
The R trimming filter 5R is not provided with a dichroic film for regulating the long wavelength side, but is merely provided with an antireflection film.
[0014]
The light totally reflected by the front surface 3R1 of the first prism 3R exits through the trimming filter 5R, and enters the image forming surface 6R1 of the R solid-state imaging device 6R. The description of the signal processing in the solid-state imaging device 6R and the signal processing in the subsequent stage is omitted.
[0015]
The third prism 3G for G is joined to the second prism 3B. On the reflection surface of the second prism 3B on the third prism 3G side, a dichroic film 4B for B is laminated. FIG. 3 shows the reflection spectral characteristics of the dichroic film 4B. The reflection spectral characteristic of the dichroic film 4B is a characteristic that suppresses light to around 600 nm on the long wavelength side, and a characteristic that reflects light in a blue wavelength range.
[0016]
Of the light transmitted through the dichroic film 4R, blue wavelength region light is reflected by the dichroic film 4B and totally reflected by the front surface 3B1 of the second prism 3B. A trimming filter 5B for B for removing an extra color component is joined to the emission surface of the blue light in the blue wavelength region of the second prism 3B. The trimming filter 5B has a configuration in which a dichroic film is laminated on colored glass. The trimming filter 5B constitutes a bandpass filter that regulates the short wavelength side with colored glass and the long wavelength side with the dichroic film.
[0017]
The blue wavelength region light totally reflected by the front surface 3B1 of the second prism 3B exits through the trimming filter 5B and enters the image forming surface 6B1 of the B solid-state imaging device 6B. The description of the signal processing in the solid-state imaging device 6R and the signal processing in the subsequent stage is omitted.
[0018]
The green wavelength region light transmitted without being reflected by the dichroic films 4R and 4B passes through the third prism 3G and is emitted. FIG. 4 shows transmission spectral characteristics of the third prism 3G (transmission characteristics of the dichroic films 4R and 4B). The solid line in FIG. 4 shows the transmission characteristics of the dichroic film 4B, and the broken line shows the transmission characteristics of the dichroic film 4R. With this characteristic, green wavelength band light can be obtained.
[0019]
A G trimming filter 5G for removing extra color components is joined to the emission surface of the third prism 3G for emitting green wavelength light. The trimming filter 5G has a configuration in which a dichroic film is laminated on colored glass. The trimming filter 5G constitutes a bandpass filter that regulates the short wavelength side with colored glass and the long wavelength side with the dichroic film.
[0020]
The green wavelength region light exits through the trimming filter 5G and enters the image forming surface 6G1 of the G solid-state imaging device 6G. Descriptions of the signal processing in the solid-state imaging device 6G and the signal processing in the subsequent stage are omitted.
[0021]
FIG. 5 shows the total spectral output characteristics (including the trimming filters 5R, 5B, 5G) in the present embodiment. In FIG. 5, the dashed line indicates the characteristics of the red wavelength region light and the infrared region light, the two-dot chain line indicates the characteristics of the blue wavelength region light, and the broken line indicates the characteristics of the green wavelength region light. The solid line shows the characteristics of the infrared light cut filter 2. When the infrared light cut filter 2 is arranged as shown in FIG. 1, the infrared region light is cut off, and a visible light imaging device can be obtained. When the infrared light cut filter 2 is removed, the imaging device can be used as a dual-purpose imaging device for infrared light.
[0022]
According to the present invention, the number of laminated dichroic films 4R for R is about 38, the number of laminated dichroic films 4B for B is about 25, and a color separation optical system for both visible light and infrared light. It can be an imaging device.
[0023]
【The invention's effect】
As described in detail above, the color separation optical system of the present invention and the imaging apparatus using the same can be easily used at low cost for infrared light, and can be used for either visible light or infrared light. You can also.
[Brief description of the drawings]
FIG. 1 is a plan view showing an embodiment of the present invention.
FIG. 2 is a diagram showing reflection spectral characteristics of a dichroic film for R in the present invention.
FIG. 3 is a diagram showing reflection spectral characteristics of a dichroic film for B in the present invention.
FIG. 4 is a diagram showing transmission spectral characteristics of a G prism according to the present invention.
FIG. 5 is a diagram showing overall spectral characteristics in the present invention.
[Explanation of symbols]
Reference Signs List 1 photographing lens 2 infrared light cut filter 3R first prism 3B second prism 3G third prism 4R, 4B dichroic films 5R, 5B, 5G trimming filters 6R, 6B, 6G solid-state imaging device

Claims (2)

In a color separation optical system that separates incident light into three primary color lights,
A first prism for red wavelength region light, a second prism for blue wavelength region light, and a third prism for green wavelength region light arranged in order from the side where the incident light is incident;
A first dichroic film provided on the first prism and reflecting a region including red wavelength region light and infrared region light;
A color separation optical system, comprising: a second dichroic film provided on the second prism and reflecting a region including blue wavelength region light. In an imaging device that captures incident light from a subject collected by a taking lens,
Three prisms including a first prism for red wavelength band light, a second prism for blue wavelength band light, and a third prism for green wavelength band light arranged in order from the photographing lens side;
A first dichroic film provided on the first prism and reflecting a region including red wavelength region light and infrared region light;
A second dichroic film provided on the second prism and reflecting a region including blue wavelength region light;
An image pickup apparatus, comprising: a detachable infrared light cut filter disposed between the photographing lens and the first prism.

Images