JPS59170734A - Multicolor resolving system - Google Patents

Abstract

PURPOSE:To distribute efficiently bands by combining plural sheets of spectroscopic filter groups of multilayered films and alotting the widths of the wavelength bands occupied by the spectral outputs of respective colors according to wavelengths. CONSTITUTION:Photoelectric converters 901-906 receive respectively the output light from spectrally divided channel 1 - channel 6. An incident ray 910 to, for example, the converter 903 of the channel 3 transmits through dichroic mirrors C, B, and is reflected by a dichroic mirror A and thereafter the ray is taken out through an interference filter 913 for shaping band. The spectral output determined by the product of the reflection or transmission characteristic of the dichroic mirrors existing on each optical path and the transmission characteristic of the interference filter for shaping the band in the terminal part appears similarly in the other channels as well.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a multicolor separation system used in color separation scanners, multispectral scanners (MSS), and the like.

Structure of Conventional Example and Its Problems Conventional color separation systems are generally three-color separation systems used in color photographic electrotransmission devices, color scanners for printing plates, and the like.

Color separation systems that perform multicolor separation of three or more colors include, for example, multispectral separation systems for remote sensing, which are mounted on aircraft and artificial satellites and used for resource exploration and oceanographic research. However, multispectral separation systems for remote sensing are complex and expensive optical systems that use prisms and diffraction gratings, or have a disadvantageous structure in which a large number of color separation cameras are arranged in parallel for each wavelength band. However, it is not a device for the general public.

On the other hand, Japanese Unexamined Patent Publication No. 107383/1983 describes a method for constructing a compact and efficient multispectral decomposition system. According to this, for example, as shown in FIG. 1, by combining five dichroic mirrors, the visible wavelength band can be separated into six channels of multi-bands. In FIG. 1, dichroic mirrors 1001 to 1005 are nonmetallic multilayer filters with special spectral wavelength characteristics, and a method of combining these is described. The incident light beam 1018 is split into six light beams by these five dichroic mirrors, and is further separated by an interference filter 10.
After passing through rays 06 to 1011, finally rays 1019 to 1024
Thus, the photoelectric conversion layers 1012 to 1017 of each channel
The light is received by the The wavelength selection characteristics of the final output light at this time are obtained from the composite characteristics of the dichroic mirror and interference filter placed on each optical path. The interference filters 1006 to 1011 are added for the purpose of compensating for the incomplete blocking characteristics of the dichroic mirror and for band shaping to correct the band separation characteristics.

That is, in the example of FIG. 1, it is described that by using a group of interference filters as shown in FIG. 2, the channel spectral characteristics shown in FIG. 3 can be finally obtained.

However, in the above method, the center wavelength and bandwidth of each channel are obtained as a result of a combination of filters selected through appropriate trial and error, and are not necessarily the optimal wavelength division. is not. As can be seen in Figure 2, the band shaping characteristics required for an interference filter are that the center wavelengths are not equally spaced, but as the spacing increases from short wavelengths to long wavelengths, the bandwidth tends to widen accordingly. It shows. This is generally a natural result considering the resonance characteristics of the dichroic ink mirror and the like, and in an interference filter with a multilayer film structure, the actual wavelength λ is the center wavelength λ. The phase normalized by, for example, λ/λ. A certain resonance characteristic is defined for . Therefore, if we describe the characteristics of a certain type of multilayer filter at the actual wavelength λ, its main reflection band, main transmission band, sub-reflection band, sub-transmission band, etc. will generally have a large spread in the long wavelength band and will be blocked. The characteristics also have a gentle slope. These characteristics are almost the same for the aforementioned dichroic mirror and for the shaping interference filter. Japanese Unexamined Patent Publication No. 1973-
In Publication No. 107383, the above-mentioned difference in band spread between the short wavelength band and the long wavelength band is not sufficiently taken into account, and the wavelength division method lacks rationality, resulting in wasteful use of the band. There is. FIG. 7 of Japanese Unexamined Patent Publication No. 53-107383 describes an even more remarkable example showing that wavelength division is not rational in the case of eight channels.

Purpose of the Invention The present invention +2.
This method is applied to No. 83 or a similar multicolor separation system to perform more rational wavelength division, and the purpose is to perform band allocation without waste.

Structure of the Invention The present invention is characterized in that incident light is split into a plurality of wavelength bands by a plurality of multilayer interference filters placed on the optical path, and the center wavelength and the bandwidth of each wavelength band are divided into wavelength-dependent distribution ratios. It is a combination of each filter so that

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described in detail below. Figure 4 shows
FIG. 3 is an explanatory diagram showing a basic wavelength band division method in the multicolor separation system of the present invention, and depicts ideal characteristics in which the co-transmittance of each channel is uniform. C indicates the center wavelength of the first channel, Δλl indicates its half-width, and wavelength range λ. ,. ~λma
x is divided so that each Δ2□ is adjacent to the other without a gap and has a steep blocking characteristic. In the present invention, as such an ideal wavelength division single force method, △λ□-1
Rather than uniform cutting, the bandwidth depends on the center wavelength λ.
The basic ability to think is to think differently. The basis for this is that a spectral filter with a steep cutoff characteristic and low loss (7) is best, and a nonmetallic multilayer filter is the best.When using this, the band characteristic is constant △λ□/λ. This is because the dimensions are determined to match the ratio.

The ratio of Δλ□/λ is determined by the structure of the multilayer film.

Figure 5 is an example of a multilayer interference filter for band shaping. λ4 = 546 nm, Δλ = 38 nm, and the band ratio △λi/λ, -1: o, o7 (7%) is the same as λ1. remains almost constant. Of course, regardless of the wavelength △
It is not impossible to realize a filter in which the absolute value of □λ□ is constant, but it would be necessary to design and manufacture a multilayer film with a different configuration for each λi, especially for a steep and wide-bandwidth type as shown in the example. It is not easy to obtain such characteristics.

Furthermore, FIG. 6 shows an example of the characteristics of a multilayer gicchroic mirror with steep cutoff characteristics, where 8TBIC is the center wavelength λ of the main reflection band. is 6oO26E50.600
Designed in nm. As is clear in this example, the half-value width Δλ of the main reflection band. λ. The ratio to Δλ. /λ.

−z λ at 0.115. It remains almost constant regardless of the 6th
In B and C of the figure, sub-reflection bands appear on the short wavelength side, respectively, and these spectral characteristics are based on the wavelength λ on the horizontal axis. Normalized by λ/2°■, in other words, they overlap on the same graph, and the display at the actual wavelength can be regarded as simply changing the scale of the axis in proportion to the wavelengthQ.Therefore, these Even when configuring a multicolor separation system by combining a dichroic ink mirror and a shaping interference filter, it is more natural to divide each channel so that △λ□/λ□ is a constant ratio. considered reasonable.

Based on the above basic idea, a specific band division method of the present invention will be explained next.

In the ideal diagram of Figure 4, △λ□/λ, =X (constant)...
- If (1) is set, the following formula holds true.

Σ △λ1−λmax−λmin ・・・・
...(2) 1=1 If we eliminate λ and △λ from these equations, then in Figure 9, 901 to 906 are the photoelectrons that receive the separated output lights of channels 1 to 6, respectively. It is a converter. For example, in the photoelectric converter 903 of channel 3,
After the incident light beam 910 passes through dichroic mirrors 〇 and B and is reflected by A, it passes through a band shaping interference filter 913.
It is taken out after passing through. Similarly for other channels,
A spectral output is determined by the product of the reflection/transmission characteristics of the dichroic mirrors present on each optical path and the transmission characteristics of the band-shaping interference filter at the end. Although the amplitude of each spectral output in Figure 9 differs for each channel due to the product of the number of mirrors passing through and their characteristics, the overall characteristics are approximately the same as the band division in Figure 7 with a 5 nm degree error due to the error in the center wavelength. can be realized.

Although this embodiment has a configuration different from that of the conventional example shown in FIG. 1, the visible range is divided into six channels as in FIG. 1. Regarding the dichroic mirror arrangement,
There may be other possible combinations.The difference between this embodiment and the conventional example shown in FIG. 1 lies in the wavelength selection method of each dichroic mirror and band shaping interference filter.
As illustrated in FIG. 7, more rational and efficient band division can be achieved than in FIG. 3.

Effects of the Invention As described above, according to the present invention, the wavelength range λ□ is used. ~'max and its division number N, the center wavelength λ and bandwidth Δλ of each spectral channel can be uniquely determined, and the bandwidth ratio Δλ /λ of each channel is constant, so multilayer Design and manufacture of membrane filters becomes easier. -! However, the resulting spectral characteristics have practical effects such as no waste in terms of band usage and the ability to construct an efficient multispectral decomposition system.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing an example of the configuration of a conventional multicolor separation system, Fig. 2 is a characteristic diagram of the band shaping filter shown in Fig. 1, Fig. 3 is a channel spectral characteristic diagram of Fig. 1, Figure 5 is an explanatory diagram of the band division method of the present invention, Figure 5 is an explanatory diagram of the characteristics of a band shaping interference filter, Figure 6 (C at Aλ), Kazumasa [7 Tomi' Example of wavelength characteristics of Kreuzk mirror, Figure FIG. 7 is a diagram showing an example of band division to which the present invention is applied, and FIG.
FIG. 9 is a characteristic diagram showing an example of a band shaping interference filter that satisfies the figure, and FIG. 9 is a characteristic diagram of a filter to which the present invention is applied. 901-906...Photoelectric converters, A, B, C. D, E... Dichroic mirror, 911-916
...Interference filter. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Fig. 4 Fig. 2 Fig. 3 Fig. 5 Fig. 416〃θ Zθ+D(HJ

Claims (1)

[Scope of Claims] (1) A multicolor separation system constructed by combining a group of a plurality of multilayer film spectral filters, and characterized in that the wavelength bandwidth occupied by the spectral output of each color is allocated depending on the wavelength. . (2) Multicolor separation according to claim 1, characterized in that the wavelength bandwidth occupied by the spectral output of each color is determined such that the half width thereof is continuous between adjacent colors without any gaps. system. (3) The multicolor separation system according to claim 1, wherein the wavelength bandwidth occupied by the spectral output of each color is determined to be a constant ratio with respect to its center wavelength. (4) The first claim characterized in that the wavelength bandwidth occupied by the spectral output of each color is determined in proportion to the wavelength.
The described multicolor separation system. (6) The multicolor separation system according to claim 1, wherein the group of multilayer film spectral filters includes a plurality of dichroic mirrors and a plurality of band shaping interference filters.