JPH09163072A - Color image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the difference in output level among light receiving elements without increasing the production cost and to reduce the power consumption of a white light source. SOLUTION: Light receiving elements 3R, 3G, and 3R of R, G, and B are so arranged that the optical path length between the light receiving element of B having the lowest sensitivity out of light receiving elements 3R, 3G, and 3R of R, G, and B and a white light source 1 is shorter than any other optical path lengths between light receiving elements 3R and 3G and the white light source 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image reading device.

[0002]

2. Description of the Related Art As an example of a conventional color image reading apparatus, as shown in FIG. 3, one white light source 31 and a color CCD sensor 32 are provided, and a white light source 31 emits light and a reading object 33 is used. There is a type in which the reflected light is condensed by the lens 34 and is incident on the color CCD sensor 32.

However, as shown in FIG. 4, the light receiving elements 32 _R , 32 _G , and 32 _B of the color CCD sensor 32 have the lowest sensitivity for the blue or B light receiving element 32 _B and the green or G light receiving element. Although 32 _G and red, that is, the R light receiving element 32 _R are almost the same, the R light receiving element 3
2 _R is a little more sensitive.

[0004]

Therefore, in the conventional color image reading apparatus shown in FIG. 3, the light amount of the white light source 31 is determined according to the light receiving element 32 _B of _B having low sensitivity, and the white light source 31 is used. However, there is a problem that the power consumption is large. In addition, since there is a large difference in the levels of the RGB color signals depending on the colors, it is necessary to amplify the output of the _B light receiving element 32 _B with a large amplification factor when amplifying them and aligning the levels, which increases the noise level. There was also a problem. Moreover, the white light source 31 and each light receiving element 32
_No consideration is given to the optical path length between _R , 32 _G , and 32 _B, and as shown in FIG. 3, the optical path length between the _B light receiving element 32 _B having low sensitivity and the white light source 31 is the most In many cases, the light receiving elements 32 _R , 32 _G , and 32 _B are arranged so as to be long.

Therefore, as shown in FIG. 5, three light sources 31 _R , 31 _G and 31 _B of _R , _G and _B are provided, and each light source 31
A configuration has been proposed in which the amount of light is individually adjusted for each of _R , 31 _G , and 31 _B , but in this case, three light sources 31 are used.
_{Since R} , 31 _G and 31 _B are used, the manufacturing cost was high.

Further, as shown in FIG. 6, three monochrome
CCD sensor 35_R, 35_G, 35 _BAnd reflect the light of R
Filter 36_RAnd a filter 36 that reflects the G light
_GAnd monochrome separation by color separation.
Service 35_R, 35_G, 35_BIt is configured to prevent the sensitivity of
However, in this case, three monochrome
CCD sensor 35_R, 35_G, 35_BAnd two filters
36_R, 36_GBecause the manufacturing cost is high,
there were.

Further, as shown in FIG. 7, in addition to the white light source 31, a B light source 31 _B is separately provided to increase the amount of B light.
Since the light source 31 _B is used separately, the manufacturing cost was high.

The present invention has been proposed in view of the above points, and it is possible to reduce the difference in the output level from each light receiving element without increasing the manufacturing cost and to reduce the power consumption of the white light source. An object of the present invention is to provide a color image reading device that can be used.

[0009]

In order to achieve the above object, the color image reading apparatus of the invention described in claim 1 is
A color image reading apparatus having one white light source and R, G, B light receiving elements, and photoelectric conversion means for receiving the light emitted from the white light source and reflected by the surface of the object to be read. Therefore, the optical path length between the light receiving element having the lowest sensitivity among the R, G, and B light receiving elements and the white light source is shorter than the optical path length between any other light receiving element and the white light source. Thus, the R, G, and B light receiving elements are arranged.

A color image reading apparatus according to a second aspect of the invention has one white light source and R, G, and B light receiving elements, and the surface of the reading object is emitted from the white light source. A color image reading apparatus including a photoelectric conversion unit that receives the light reflected by, and the optical path length between the white light source and the most sensitive light receiving element among the R, G, and B light receiving elements is
Each of the R, G and B light receiving elements is arranged so as to be longer than the optical path length between any other light receiving element and the white light source.

Further, the color image reading apparatus of the invention described in claim 3 has one white light source and R, G, and B light receiving elements, and is emitted from the white light source and is on the surface of the object to be read. A color image reading apparatus including a photoelectric conversion unit that receives the light reflected by, and the optical path length between the light receiving element having the lowest sensitivity among the R, G, and B light receiving elements and the white light source is
The optical path length between any other light receiving element and the white light source is shorter than that, and the optical path length between the light receiving element having the highest sensitivity among the R, G, B light receiving elements and the white light source is Each of the R, G and B light receiving elements is arranged so as to be longer than the optical path length between any other light receiving element and the white light source.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be specifically described below with reference to the drawings.

FIG. 1 shows a color image reading apparatus according to the present invention.
FIG. 1 is a schematic configuration diagram of the color image reading device
Equipped with color light source 1, lens 2, and color CCD sensor 3
I have. The white light source 1 emits white light as an example of an object to be read.
The surface of the original 4 is irradiated. The lens 2 is
The light reflected on the surface is collected and enters the color CCD sensor 3.
To shoot. A color CCD cell as an example of photoelectric conversion means.
The sensor 3 is a light receiving element 3 for each of R, G and B._R, 3_G, 3_BTo
It is equipped with an anti-reflective light from the original 4 which is condensed by the lens 2.
It receives the emitted light and outputs RGB color signals. Light receiving element
3_R, 3_G, 3 _BIs white light in the left-right direction of FIG.
Light receiving element 3 in order from the source 1_B, Light receiving element 3_G， Photosensor
Child 3_RIt is arranged. White light source 1, lens 2, and
And the color CCD sensor 3 are arranged in a direction orthogonal to the plane of FIG.
Has a predetermined length and the light receiving element 3_R, 3_G, 3_B
Are arrayed in a direction orthogonal to the plane of FIG.
ing. Light receiving element 3_RHas a sensitivity peak for red light
doing. Light receiving element 3_GHas a peak sensitivity to green light
Have. Light receiving element 3_BHas a peak sensitivity to blue light
have. Place the original 4 on a transparent original table (not shown).
It is installed in the left and right direction of Fig. 1 by a feeding mechanism (not shown).
It is sent at a fixed pitch.

Next, the operation of the color image reading apparatus thus constructed will be described. The white light emitted from the white light source 1 strikes the surface of the original 4 and is reflected, is condensed by the lens 2, and enters the light receiving elements 3 _R , 3 _G , 3 _B of the color CCD sensor 3. As a result, each of the light receiving elements 3 _R , 3 _G , 3 _B outputs an RGB color signal according to the intensity of the R, G, B incident light. Here, each light 5 _R, 5 _G, the optical path length of 5 _B L _R that is incident is emitted from the white light source 1 to the light receiving elements _{3 R, 3 G, 3 B} , L G, when examined L _B, FIG. 2, the light receiving elements 3 _R , 3 _G ,
The optical path lengths L _R1 , L _G1 , and L _B1 from 3 _B to the surface of the original 4 are
Shortest optical path length L _G1 light 5 _G is the optical path length L _B1 in the optical path length L _R1 and the light 5 _B light 5 _R are the same length. Also, manuscript 4
The optical path lengths L _R2 , L _G2 , and L _B2 from the surface to the white light source 1 are
The light path length L _B2 of the light 5 _B is the shortest, and the light path length L _R2 of the light 5 _R is the longest. And the total optical path length L which is the sum of them
_R, L _G, L _B is the shortest optical path length L _B of the light 5 _B, the optical path length L _R of the light 5 _R longest. That is, the light path length L _B of the light 5 _B incident on the _B light receiving element 3 _B having the lowest sensitivity is the shortest, and the light path length L _R of the light 5 _R incident on the _R light receiving element 3 _R having the highest sensitivity is the shortest. The light receiving elements 3 _R , 3 _G and 3 _B are arranged so as to be long. Therefore, the light 5 _B incident on the _B light receiving element 3 _B having the lowest sensitivity is the strongest and the light 5 _R incident on the _R light receiving element 3 _R having the highest sensitivity is
Is the weakest. As a result, the low sensitivity of the light receiving element 3 _B is compensated by the intensity of the incident light 5 _B , and the light receiving elements 3 _R , 3 _G ,
The difference between the levels of the RGB color signals from 3 _B is reduced.

As described above, each of the R, G and B light receiving elements
3_R, 3_G, 3_BB light receiving element 3 with the lowest sensitivity
_BPath length L between the and white light source 1_BIs the shortest
One, the most sensitive light receiving element 3_RBetween the white light source 1 and
Optical path length L_REach of R, G and B light so that
Element 3_R, 3_G, 3_BAs the white light source is used,
Power can be reduced. That is, the intensity of light is the white light source 1
Since it is inversely proportional to the square of the distance, the optical path length L_BShorten
The light receiving element 3_BLight 5 incident on_BThe strength of
Can be strong Moreover, the reflected light from the original 4 is scattered light.
So that the white light source 1 illuminates the original 4 brightly.
Is important, but the optical path between the white light source 1 and the surface of the original 4
Long L_B2Light 5_BIs the shortest, so the original 4 is illuminated brightest.
Light 5_BIs the light receiving element 3_BIncident on. Therefore,
Light receiving element 3_BThe low sensitivity of the incident light 5 _BBy the strength of
Complementary, light receiving element 3_BThe level of the B color signal from
Since it becomes large, the light quantity of the white light source 1 can be made small.
Therefore, the power consumption of the white light source can be reduced.

Further, since the difference in level depending on the colors of the RGB color signals from the light receiving elements 3 _R , 3 _G and 3 _B becomes small, it is possible to reduce the difference in the amplification factor of each color when amplifying them, so that the amplification is performed. The difference in noise level can also be reduced.

Moreover, since it is not necessary to provide a plurality of light sources or filters for color separation, the manufacturing cost is not increased.

In the above embodiment, the R light receiving element 3 is used.
_Although the optical path length L _R of the light 5 _R incident on _R is set to be the longest, the difference in sensitivity between the _R light receiving element 3 _R and the G light receiving element 3 _G is not so large. optical path length L _G of the light 5 _G incident on _G may be is the longest.

In the above embodiment, the B light receiving element 3
_BLight 5 incident on_BOptical path length L_BTo be the shortest
However, in the future, other light receiving elements 3_R, 3_GThe sensitivity of
Up to B light receiving element 3_BAs the sensitivity of them exceeded those
In this case, the B light receiving element 3 _BLight 5 incident on_BOptical path
Long L_BShould be the longest.

[0020]

As described above, according to the color image reading apparatus of the present invention as set forth in claim 1, between the light receiving element having the lowest sensitivity among the R, G and B light receiving elements and the white light source. Since the R, G, and B light receiving elements are arranged so that the light path length is shorter than the light path length between any other light receiving element and the white light source, the low sensitivity of the light receiving element causes the incident light to fall. Since it can be compensated for by the strength of, the difference in the output level of each light receiving element can be reduced and the power consumption of the white light source can be reduced. Moreover, since it is not necessary to provide a plurality of light sources and filters for color separation, the manufacturing cost is not increased.

According to the color image reading apparatus of the invention described in claim 2, the optical path length between the white light source and the light receiving element having the highest sensitivity among the R, G and B light receiving elements is different. Since each of the R, G, and B light receiving elements is arranged so as to be longer than the optical path length between any of the light receiving elements and the white light source, the sensitivity of the light receiving element is appropriate depending on the weakness of the incident light. Therefore, the difference between the output levels of the light receiving elements can be reduced. Therefore, at the time of amplification for equalizing the output levels, the amplification factor of each color can be made relatively uniform, and the difference in noise level due to amplification can be reduced. Moreover, since it is not necessary to provide a plurality of light sources and filters for color separation, the manufacturing cost is not increased.

Further, according to the color image reading apparatus of the invention described in claim 3, the light path length between the light receiving element having the lowest sensitivity among the R, G and B light receiving elements and the white light source is different. Which is shorter than the optical path length between any of the light receiving elements and the white light source, and the optical path length between the light receiving element having the highest sensitivity among the R, G and B light receiving elements and the white light source is Since each of the R, G, and B light receiving elements is arranged so as to be longer than the optical path length between any of the light receiving elements and the white light source, the difference in sensitivity between the light receiving elements is properly adjusted depending on the intensity of the incident light. Since the correction can be performed, the difference between the output levels of the light receiving elements can be reduced most appropriately, and the power consumption of the white light source can be reduced. Moreover, since it is not necessary to provide a plurality of light sources and filters for color separation, the manufacturing cost is not increased.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a color image reading apparatus according to the present invention.

FIG. 2 is an explanatory diagram of an optical path length of incident light to each light receiving element included in the color image reading device according to the present invention.

FIG. 3 is a schematic configuration diagram of a conventional color image reading device.

FIG. 4 is an explanatory diagram of sensitivities of respective light receiving elements to colors.

FIG. 5 is a schematic configuration diagram of a conventional color image reading device.

FIG. 6 is a schematic configuration diagram of a conventional color image reading device.

FIG. 7 is a schematic configuration diagram of a conventional color image reading device.

[Explanation of symbols]

1 white light source 2 Lens 3 color CCD sensor 3 _R, 3 _G, 3 _B light-receiving element 4 document 5 _R, 5 _G, 5 _B light L _R, L _G, L _B pathlength

Claims (3)

[Claims] 1. A photoelectric conversion means for receiving light emitted from the white light source and reflected by a surface of a reading object, the photoelectric conversion means having one white light source and R, G, B light receiving elements. In the color image reading apparatus, the optical path length between the light receiving element having the lowest sensitivity among the R, G, B light receiving elements and the white light source is equal to that of any other light receiving element and the white light source. A color image reading device, wherein each of the R, G, and B light receiving elements is arranged so as to be shorter than the optical path length between them. 2. A photoelectric conversion means having one white light source and R, G, and B light receiving elements, and receiving the light emitted from the white light source and reflected on the surface of the object to be read. In the color image reading device, the optical path length between the light receiving element having the highest sensitivity among the R, G, B light receiving elements and the white light source is equal to that of any other light receiving element and the white light source. A color image reading device, wherein each of the R, G, and B light receiving elements is arranged so as to be longer than the optical path length between them. 3. A photoelectric conversion means having one white light source and R, G, B light receiving elements, and receiving the light emitted from the white light source and reflected on the surface of the object to be read. In the color image reading apparatus, the optical path length between the light receiving element having the lowest sensitivity among the R, G, B light receiving elements and the white light source is equal to that of any other light receiving element and the white light source. Shorter than the optical path length between
In addition, the optical path length between the light receiving element having the highest sensitivity among the R, G, and B light receiving elements and the white light source is longer than the optical path length between any other light receiving element and the white light source. A color image reading device in which the R, G, and B light receiving elements are arranged so as to be long.