Original reading apparatus, having a filter, for reading a color original

A color original reading apparatus includes a filter having a long-wavelength invisible radiation absorption filter and a long-wavelength invisible radiation reflection filter, or includes a spectral distribution correction filter arranged in an optical path from an original illumination light source to a color image sensor via an original.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to an original reading apparatus for 
converting original information into an electrical signal and, more 
particularly, to an apparatus for reading a color original. 
2. Related Background Art 
A conventional apparatus is known wherein a small color separation filter 
for a plurality of colors is formed on a light-receiving surface of a 
solid-state image sensor such as a CCD having a plurality of photoelectric 
transducer elements. Image signals corresponding to the respective color 
components and generated by such an original reading apparatus must 
represent color separation images with good reproducibility. However, if 
such image signals are used to reproduce a color image in practice (by an 
electrophotographic system, an ink-jet system, or a thermal transfer 
system), the hues of the reproduced color image tend to be often different 
from those of the original color image. In other words, reproducibility of 
the image signals representing the original hue is poor. 
Extensive studies on poor reproducibility have been made, and the following 
facts are found. 
Each photoelectric transducer element of the solid-state color image sensor 
has good spectral sensitivity for visible radiation as well as invisible 
light having a long wavelength. A color separation filter of the 
solid-state color image sensor has a high transmissivity for the visible 
radiation as well as invisible light having a long wavelength. If an 
original illumination radiation source emits both visible light and 
invisible light having a long wavelength, the sensor detects both visible 
and invisible beams and generates an output representing the intensity of 
a mixture of the visible and invisible beams. The component corresponding 
to the visible beam cannot be distinguished from the component 
corresponding to the invisible beam according to this output. Therefore, 
the level of the output is different from that of a desired output signal 
corresponding to only the intensity of the visible beam. In this manner, 
the sensor detects the invisible light component and outputs the visible 
light component signal including the invisible radiation component. 
Therefore, the reproduced color image has different hues from those of the 
original color image. 
SUMMARY OF THE INVENTION 
According to an aspect of the present invention, a filter means for 
removing invisible radiation having a long wavelength is used in addition 
to the color separation filter. The long-wavelength invisible radiation 
filter means has a long-wavelength invisible radiation absorption filter 
portion and a long-wavelength invisible radiation reflecting filter 
portion, and thus a signal for accurate reproduction of the hues of the 
original can be formed. 
According to another aspect of the present invention, a spectral 
distribution correction filter means separate from the color separation 
filter in the color image sensor is used.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 shows an original reading apparatus according to an embodiment of 
the present invention. Referring to FIG. 1, a color original 0 is placed 
on an original table 1. An original illumination lamp 2 emits light, and 
the light is reflected by a reflecting mirror 3 so as to direct the 
reflected light toward the original 0. The reflecting mirror 3 prevents 
radiation heat of the lamp 2 from being directed toward an image sensor 5 
and a filter 6. The lamp 2 may be a fluorescent lamp of, e.g., a daylight 
color. The fluorescent lamp generally has a relatively low light emission 
amount and is not suitable for high-speed reading. The spectral 
characteristics of the fluorescent lamp represent line spectra, and the 
spectral width upon color separation is narrow, thus preventing high-speed 
reading. It is therefore difficult to obtain an image signal representing 
the accurate original hue. The lamp 2 therefore preferably comprises a 
lamp having a large light emission amount and a continuous spectral 
distribution such as is exemplified by a halogen lamp. The halogen lamp 
has a continuous spectral distribution of light emission and a large light 
emission amount, as shown in FIG. 3. However, as shown in FIG. 3, the 
halogen lamp emits large amounts of near-infrared and infrared rays as 
long-wavelength invisible radiation. Therefore, a large amount of these 
long-wavelength invisible radiation components are included in light 
reflected by the original. 
A focusing optical system 4 focuses a light image of the original 0 onto a 
solid-state color image sensor 5. The focusing optical system 4 comprises 
an array of focusing elements having a short focal length and a small 
diameter, such as distributed index lenses SELFOC (tradename) available 
from Nippon Sheet Glass Co., Ltd. or such as bar lenses. 
As shown in FIG. 2, in the solid-state color image sensor 5, small 
photoelectric transducer elements 521, 522, and 523 are arranged on a 
substrate 51 in the light-receiving portion along one direction (i.e., the 
main scanning direction). Small color separation filters 531, 532, and 533 
are adhered onto the light-receiving portion. A cyan (c) component passes 
through each filter 531; green (g), through each filter 532; and yellow 
(y), through each filter 533. In this embodiment, the filter 531 has the 
spectral transmissivity characteristics represented by a curve 17 in FIG. 
4; the filter 532, by a curve 18; and the filter 533, by a curve 16. Each 
photoelectric transducer element 521 receives the c component, each 
element 522. receives the g component, and each element 523 receives the y 
component. 
The color separation filters 521, 522, and 523 are adhered to the sensor 5 
by dyeing its light-receiving portion. Therefore, the respective 
photoelectric transducer elements are also dyed. More specifically, the 
filter 532 is formed by overlying the dyed filters 531 and 533. As shown 
in FIG. 4, the spectral transmissivity of the filter 532 is the product of 
the transmissivity curves 16 and 17 of the filters 531 and 532. However, 
the filter 532 may be formed by using the corresponding dye. The color 
separation filters may be formed on the light-receiving portion of the 
sensor 5 not by dyeing but by coating. The adjacent photoelectric 
transducer elements in FIG. 2 have color separation filters of different 
colors. This is because one photosensitive transducer element corresponds 
to one pixel in this embodiment. If one pixel corresponds to a plurality 
of photoelectric transducer elements, e.g., two elements, the adjacent 
photoelectric transducer elements constituting one pixel have color 
separation filters of the same color. In this case, the colors of the 
color separation filters are changed for every plurality of photosensitive 
transducer elements. 
If CCDs are used as the sensor, a plurality of CCDs are aligned in a 
direction (the main scanning direction) perpendicular to the surface of 
FIG. 1 to constitute a linear CCD image sensor (a so-called contact type 
CCD image sensor) fixed on a single support. Alternatively, a monolithic 
linear image sensor (the so-called contact type CCD image sensor) having a 
large number of photoelectric transducer elements may be formed on a 
single elongated substrate. The linear CCD image sensor having a plurality 
of CCDs arranged as described above is used in the embodiment of FIG. 1. 
The relative spectral sensitivity of each photoelectric transducer element 
of the sensor is shown in FIG. 5. 
As shown in FIG. 4, the color separation filters 531, 532, and 533 of the 
solid-state color image sensor 5 have a high transmissivity even in the 
wavelength range exceeding 700 nm. In other words, the color separation 
filters have a high transmissivity for long-wavelength invisible radiation 
including near-infrared and infrared radiation components beyond human hue 
discrimination capability. As shown in FIG. 5, the photoelectric 
transducer elements 521, 522, and 523 of the solid-state color image 
sensor 5 have sensitivity limitation components having wavelengths up to 
about 1,000 nm. The transducer elements 521, 522, and 523 therefore have 
considerably high sensitivity for the near-infrared and infrared 
components as long-wavelength invisible components. The halogen lamp used 
as the lamp 2 emits large amounts of the near-infrared and infrared 
components, as shown in FIG. 3. Therefore, the photosensitive transducer 
elements 521 detect the cyan component as well as the near-infrared and 
infrared components of the light emitted from the lamp 2 and reflected by 
the original 0. Thus, the output from the transducer element 521 
represents not only the light amount of the cyan component but a mixture 
of amounts of the cyan, near-infrared radiation, and infrared components. 
Similarly, the elements 522 and 523 generate outputs which represent not 
only the light amounts of green and yellow components but represent the 
radiation amounts including near-infrared and infrared noise components. 
However, the noise components cannot be discriminated as outputs 
corresponding to the cyan, green, and yellow light amounts. For this 
reason, a color image signal formed by a conventional original reading 
apparatus does not accurately correspond to the hues of the original 
(i.e., the hue sensed by the human eye). 
In the embodiment of FIG. 1, the filter 6 for removing the near-infrared 
and infrared components as the long-wavelength invisible radiation is 
arranged in an optical path. The detailed construction of the filter 6 is 
illustrated in FIG. 6. Referring to FIG. 6, a thin optical film 62 for 
reflecting near-infrared rays is deposited on a heat wave absorption glass 
substrate, which is an infrared radiation absorption filter, 61 to 
constitute an integral body of the infrared radiation absorption filter 61 
and the near-infrared light reflection filter 62. 
In this embodiment, phosphate (P.sub.2 O.sub.5) glass melted with ferrous 
oxide (FeO) is used for the filter 61. The filter 62 has a multilayer 
structure obtained by alternately stacking titanium oxide films 620 and 
silicon oxide films 621. The filter 62 is thus a thin optical film. This 
film is not transparent to human visual sensitivity and reflects and 
removes the near-infrared rays of 700 nm or more which do not contribute 
to hue discrimination. As shown in FIG. 7, the transmissivity of the 
near-infrared light reflection filter 62 is slightly increased at about 
850 nm. At the wavelength of about 850 nm, the spectral distribution of 
light emitted from the halogen lamp 2 and reflected by the original 0 has 
substantially a peak. For this reason, the light components of about 850 
nm cannot be sufficiently blocked by only the filter 62, and the signal 
representing the accurate hues of the original cannot be obtained. In 
addition to the filter 62, the infrared light absorption filter 61 having 
the transmissivity characteristics shown in FIG. 8 is used to completely 
shield the sensor 5 from the near-infrared and infrared rays. In other 
words, the infrared light absorption filter having the characteristics in 
FIG. 8 has considerably high transmissivities for the light components of 
about 700 nm to 900 nm which are beyond the hue discrimination capability. 
The halogen lamp 2 emits large amounts of the light components of about 
700 nm to 900 nm. If only the filter 61 is used, these long-wavelength 
components cannot be sufficiently blocked by the filter 61 and reach the 
sensor 5. In this manner, the image signal representing the accurate hues 
of the original cannot be produced. Therefore, the filter 61 is combined 
with the filter 62 having characteristics (FIG. 7) for eliminating the 
near-infrared rays of 700 nm or longer (these rays are beyond the human 
hue discrimination capability). Then, the sensor 5 is substantially 
shielded from the long-wavelength invisible light components. 
In the embodiment of FIG. 1, the near-infrared light reflection filter and 
the infrared light absorption filter are integrally formed by using a 
single glass plate. With this construction, the near-infrared and infrared 
light removal filter means has a small thickness and can be easily 
inserted in a short optical path between the array 4 and the sensor 5. 
However, the near-infrared light reflection filter 62 may be arranged 
separately from the infrared light absorption filter 61. 
By using the invisible light elimination filter 6, the noise components 
corresponding to the near-infrared and infrared rays which are beyond the 
human hue discrimination capability can be removed from the outputs of the 
photoelectric transducer elements 521, 522, and 523. Therefore, a color 
image signal representing the accurate hues of the original can be 
produced. 
An output from each photoelectric transducer element in the sensor 5 is 
processed by a circuit in FIG. 9. The output is converted into an image 
signal. More specifically, the outputs from the photoelectric transducer 
elements in the sensor 5 are extracted along the main scanning directions 
and are commonly applied to a variable amplifier 8. The output levels are 
controlled by the variable amplifier 8. A serial output signal from the 
sensor 5, i.e., a serial output signal from the amplifier 8 is a composite 
signal consisting of a signal (i.e., a c signal) corresponding to the 
outputs from the elements 521, a signal (i.e., a g signal) corresponding 
to the outputs from the elements 522, and a signal (i.e., a y signal) 
corresponding to the outputs from the elements 523. A sample/hold circuit 
9c separates the c signal form the composite signal. Similarly, a 
sample/hold circuit 9g separates the g signal from the composite signal, 
and a sample/hold circuit 9y separates the y signal therefrom. The 
components affixed by reference symbols c, g, and y are circuits for 
respectively processing the c, g, and y signals. 
The signals separated by the corresponding sample/hold circuits are 
amplified by amplifiers 10c, 10g, and 10y to identical levels. The 
amplifiers 10c 10g, and 10y can finely adjust the gains of the inputs. 
High-frequency noise components of the amplified image signals are then 
removed by low-pass filters 11c, 11g, and 11y. 
The c signal is the one corresponding to the complementary color of red, 
and the y signal is the one corresponding to the complementary color of 
blue. As is also apparent from the spectral distribution (FIG. 3) of the 
radiation emitted from the lamp 2, the transmissivity characteristic 
curves (FIG. 4) of the respective color separation filters, and the 
spectral sensitivity characteristic curve (FIG. 5) of the photoelectric 
transducer element, the c , g and y signals are not ideal signals obtained 
by using light components having flat spectral distributions and 
photoelectric transducer elements having flat spectral sensitivity. In 
order to obtain image signals accurately corresponding to the three 
primary colors, i.e., red (R), green (G), and blue (B), the c, g, and y 
signals are preferably processed on the basis of the corresponding 
spectral transmissivity and spectral sensitivity characteristics as 
follows: 
EQU R=c-A.sub.1 g (1) 
EQU G=g-A.sub.2 c-A.sub.3 y (2) 
EQU B=y-A.sub.4 g (3) 
where A.sub.1 to A.sub.4 are coefficients determined by the spectral 
distribution of the light emitted from the lamp 2 and reflected by the 
original, the spectral transmissivity distribution of the color separation 
filters used in the solid-state color image sensor 5, and the spectral 
sensitivity of the photoelectric transducer elements. In an apparatus 
having different reflected radiation spectral distributions, different 
spectral transmissivity distributions, and different spectral 
sensitivities, the corresponding different coefficients are determined. If 
the colors of the color separation filters are different from those used 
in this embodiment, different equations are established. It is essential 
to employ equations for providing signals accurately reproducing the three 
primary colors by using the output signals from the photoelectric 
transducer elements of the corresponding colors. 
In order to perform the above calculations, the c, g, and y signals are 
sequentially supplied to inverting amplifiers 12c, 12g, and 12y and 
inverting amplifiers 12c'. Clamp circuits 13c, 13g, and 13y and clamp 
circuits 13c', 13g', and 13y' clamp the signals to predetermined levels. 
An arithmetic circuit 14R calculates equation (1) and receives the signals 
from the amplifiers 12c' and 12g. An arithmetic circuit 14G calculates 
equation (2) and receives the signals from the amplifiers 12g', 12c, and 
12y . An arithmetic circuit 14B calculates equation (3) and receives the 
signals from the amplifiers 12y' and 12g. The arithmetic circuits 14R, 
14G, and 14B respectively generate a signal (i.e., an R signal) 
corresponding to red, a signal (i.e., a G signal) corresponding to green, 
and a signal (i.e., a B signal) corresponding to blue. The R, G, and B 
signals are amplified by amplifiers 15R, 15G, and 15B, respectively. The 
amplified signals are converted into digital signals by A/D 
analog-to-digital converters 16R, 16G, and 16B, respectively. These 
digital signals are sent as the image signals to the image reproduction 
apparatus. In the reproduction apparatus, a red image is formed by using 
the output image signal from the converter 16R. Similarly, a green image 
is formed by using the output image signal from the converter 16G, and a 
blue image is formed by using the output image signal from the converter 
16B. These red, green, and blue images overlap to form a multicolor image. 
The image reproduction apparatus uses a laser beam driven by the image 
signals, a light-emitting diode array, or a liquid crystal shutter array 
to expose a photosensitive body with light, thereby forming a latent 
image. The latent image on the photosensitive body is developed by toners 
of three colors. Alternatively, an ink-jet head or thermal head is driven 
by the image signals to form a multicolor image. Any type of image 
reproduction apparatus may be used, and a detailed description thereof 
will be omitted. 
The filter 6 is preferably arranged in the optical path between the array 4 
and the sensor 5, as shown in FIG. 1 since the filter 6 can be located 
away from the lamp 2 in the optical path, thereby minimizing degradation 
of the filter. In addition, the width of the filter can be preferably 
minimized. However, the filter may be arranged in the optical path between 
the lamp 2 and the original 0 or between the original 0 and the array 4. 
The color separation filters 531, 532, and 533 formed on the solid-state 
color image sensor 5 are respectively cyan, green, and yellow filters. 
However, red, green, and blue filters having the spectral transmissivities 
in FIG. 10 may be respectively used in place of the cyan, green, and 
yellow filters. In this case, outputs from the photosensitive transducer 
elements corresponding to the respective colors of the color separation 
filters may be processed by the same means as in the components 12, 12', 
13, 13', and 14 (the corresponding suffix is omitted) of FIG. 9. It is 
desirable to form image signals accurately representing the three primary 
colors of the original. For example, a red filter transmits not only a 
pure red beam but also a beam belonging to the green wavelength range. A 
green filter transmits not only a pure green beam but also beams belonging 
to the red and blue wavelengths ranges. A blue filter transmits not only 
pure blue beam but also beams belonging to the green wavelength range. 
Furthermore, the photosensitive transducer elements have sensitivity for 
the red, green, and blue wavelength ranges. If a predetermined value of 
the signal level from the photosensitive transducer element corresponding 
to the green filter is subtracted from the signals level for the green 
filter, an image signal representing the accurate red component of the 
original can be formed. Based upon the above assumptions, the following 
equations are given: 
EQU R=r-B.sub.1 g (4) 
EQU G=g-B.sub.2 r-B.sub.3 b (5) 
EQU B=b=B.sub.4 g (6) 
where r, g, and b are output signals from the photosensitive transducer 
elements corresponding to the red, green, and blue filters, respectively, 
and B1 to B4 are coefficients determined by the spectral distribution of 
the light emitted from the illumination lamp and reflected by the 
original, the transmissivity characteristics of each color separation 
filter, and the spectral sensitivity characteristics of the photoelectric 
transducer elements. 
It should be noted that the above calculations may be omitted. 
The red, green, and blue color separation filters have spectral 
transmissivity characteristics corresponding to the near-infrared and 
infrared rays as long-wavelength invisible radiation. According to this 
embodiment, since the filter for removing the long-wavelength invisible 
radiation is included, the R, G, and B signals are substantially free from 
the noise components corresponding to the invisible near-infrared and 
infrared rays. Therefore, the color image signal representing the accurate 
hues of the original can be produced. 
The number of colors of the color separation filters is 3 in this 
embodiment, but may be 4 or more. 
The transmissivity of each color separation filter in the color image 
sensor in this embodiment is substantially zero or very small. A halogen 
lamp having a small ratio of the near-ultraviolet and ultraviolet rays to 
the near-infrared and infrared rays in the spectral distribution of the 
light emitted from the lamp and reflected by the original is used. 
Therefore, the influence of the near-ultraviolet and ultraviolet rays as 
the short-wavelength invisible radiation on the signals corresponding to 
the colors of the color separation filters in the sensor can be neglected, 
and a near-ultraviolet and ultraviolet radiation elimination filter can be 
omitted. However, assuming that the photosensitive transducer elements 
have sufficiently high sensitivity for the near-ultraviolet and 
ultraviolet rays, that color separation filters have high transmissivities 
for the near-ultraviolet and ultraviolet rays, and that the ratio of the 
near-ultraviolet and ultraviolet rays to the near-infrared and infrared 
rays is high, the noise components corresponding to the near-ultraviolet 
and ultraviolet rays are mixed in the signals corresponding to the colors 
of the color separation filters. In order to prevent this, a filter is 
preferably arranged in an optical path to eliminate the near-ultraviolet 
and ultraviolet rays as short-wavelength invisible radiation. The filters 
having the characteristics in FIGS. 7 and 8 can substantially eliminate 
the near-ultraviolet and ultraviolet rays. More specifically, the filter 
62 reflects the near-ultraviolet rays and the filter 61 absorbs the 
ultraviolet rays. 
The means 1 to 7 in FIG. 1 are integrally mounted on a movable carriage 17. 
In the original read mode, the carriage 17 is moved in a subscanning 
direction (indicated by arrow A) substantially perpendicular to the 
longitudinal direction (i.e., the main scanning direction) of the sensor 
and scans the original. However, the original table 1 or the original 0 
itself may be moved in the subscanning direction to read the original. 
In an original reading apparatus of FIG. 11, a spectral distribution 
correction filter 7 is used in place of the invisible radiation removal 
filter 6 in the apparatus of FIG. 1. The spectral distribution correction 
filter means is used in the apparatus of FIG. 11 for the following reason. 
The spectral sensitivity of the photosensitive transducer elements in the 
solid-state color image sensor varies depending on the colors of the 
predetermined color separation filters. The transmissivities of the color 
separation filters in the sensor are different from each other according 
to different colors. Therefore, the spectral sensitivities of the sensor 
are different from each other according to the visible light components. 
Therefore, the outputs from the sensor are different from each other 
according to different visible light components. The levels of the output 
signals are conventionally adjusted by a plurality of amplifying means 
having different gains to obtain identical signal levels, thus 
complicating the circuit arrangement. In the apparatus of FIG. 11, a 
spectral distribution correction filter means is used to decrease the 
difference of levels of outputs from the color separation filters in the 
sensor, as compared with the case wherein such a filter means is not 
arranged. Therefore, the circuit arrangement can be simplified and the 
image signals accurately corresponding to the colors of the color 
separation filter can be produced. 
In the apparatus of FIG. 11, a signal processing means obtained by 
modifying the amplifiers 10c, 10g, and 10y in the circuit of FIG. 9 is 
used and operated according to the equations described above. 
As is apparent from the spectral transmissivity curves of the color 
separation filters in FIG. 4 and the spectral sensitivity curve of the 
photosensitive transducer element in FIG. 5, the total spectral 
sensitivity of the color image sensor which is expressed as the product of 
the transmissivities and the spectral sensitivity levels varies according 
to the color components. The spectral distribution of the light emitted 
from the original illumination lamp is not uniform, as shown in FIG. 3. If 
white paper having no image is used as an original, the level of an output 
from the elements 521 corresponding to cyan is considerably lower than 
that from the elements 522 corresponding to green, and is considerably 
lower than that from the elements 523 corresponding to yellow. In this 
case, in the circuit of FIG. 9, after the composite signal from the sensor 
5 is separated into the c, g and y signals, they must be input to 
amplifiers 10c, 10g, and 10y having large gain differences. However, when 
the amplifiers having large gain differences are used, the circuit 
arrangement becomes complicated. As shown in FIG. 11, the spectral 
distribution correction filter 7 is arranged in the optical path. In this 
embodiment wherein the original illumination lamp having the spectral 
distribution (FIG. 3) of the light emitted from the lamp, the color 
separation filters having the transmissivity curves (FIG. 4), and the 
photoelectric transducers having the spectral sensitivity curve (FIG. 5) 
are used, the filter having the transmissivity curve in FIG. 12 is used. 
The filter 7 is a bluish filter and is arranged in the optical path. An 
output level difference between the photoelectric transducer elements 521 
and 522, an output level difference between the photoelectric transducer 
elements 521 and 523, and hence an output level difference between the 
photoelectric transducer elements 522 and 523 are reduced as compared with 
the case wherein the filter 7 is not used. The output differences become 
substantially zero. Therefore, in the case of FIG. 9, the amplifiers 10c, 
10g, and 10y can have an identical arrangement with the gain 
fine-adjustment function and simplify the overall circuit. The output 
levels of the amplifiers 10c, 10g, and 10y are substantially the same. 
With this arrangement, a color image signal representing the accurate hues 
of the original can be produced. The transmissivity characteristics of the 
spectral distribution correction filter 7 are determined to minimize the 
output differences corresponding to the colors of the color separation 
filters in the sensor according to the transmissivity characteristics of 
the color separation filters in the solid-state color image sensor and the 
spectral sensitivity characteristics of the photoelectric transducer 
elements. The spectral distribution correction filter 7 may be a glass or 
gelatin filter dyed with phthalocyanine or the like. 
The filter 7 is preferably arranged in the optical path between the array 4 
and the sensor 5 in FIG. 11 since the filter 7 can then be located away 
from the lamp 2, thereby minimizing thermal degradation of the filter. At 
the same time, the filter width can be minimized. However, the filter 7 
may be arranged in the optical path between the lamp 2 and the original 0 
or between the original 0 and the array 4. 
The color separation filters 531, 532, and 533 formed on the solid-state 
image sensor 5 in the first embodiment are respectively cyan, green, and 
yellow filters. However, as noted red, green, and blue filters having the 
transmissivity characteristics in FIG. 10 may be respectively used in 
place of the cyan, green, and yellow filters. In this case, outputs from 
the photoelectric transducer elements for different colors in the sensor 
are preferably processed according to equations (4) to (6) to produce 
image signals representing the accurate hues of the three primary colors 
of the original. The transmissivity characteristics of the spectral 
distribution correction filter 7 are determined by the spectral 
distribution of the light emitted from the illumination lamp, the 
transmissivities of the color separation filters, and the spectral 
sensitivity characteristics of the colors of color separation in the same 
manner as in the previous embodiment. 
If the lamp having the characteristics (FIG. 3), the color separation 
filters having the characteristics (FIG. 10), and the photoelectric 
transducer elements having the characteristics (FIG. 5) are used, the 
spectral distribution correction filter 7 may have the transmissivity 
characteristics in FIG. 12. 
In an apparatus of FIG. 13, both the filters 6 and 7 are used. In this 
case, identical amplifiers with the gain fine-adjustment function can be 
used as the amplifiers 10c, 10g, and 10y in the signal processing means in 
FIG. 9. 
In the apparatus of FIG. 13, a dyed glass or gelatin filter can be used as 
the spectral distribution correction filter 7. The filter 7 may be 
arranged separately from the filter 6. However, in order to easily mount 
the filters 6 and 7 in a narrow optical path between the array 4 and the 
sensor 5, a dye such as phthalocyanine may be coated on a surface of the 
heat wave absorption glass substrate 61 which is opposite to its surface 
facing the near-infrared reflecting optical film 62, thereby constituting 
the filter 7 having transmissivity characteristics in FIG. 12. In this 
manner, the filters 6 and 7 are integrally formed to achieve a low-profile 
construction. The light without the near-infrared and infrared rays must 
be incident on the spectral distribution correction filter 7 so as to 
prevent the degradation of the filter. The filters 6 and 7 are arranged in 
the optical path between the array 4 and the sensor 5, as shown in FIG. 13 
so that the filters are located away from the lamp 2, thereby preventing 
thermal degradation of the filters. At the same time, the widths of the 
filters can be minimized. However, one or both the filters 6 and 7 may be 
located in the optical path between the lamp 2 and the original 0 or 
between the original 0 and the array 4.