JPH0443471B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a color image reading device.

FIG. 1 shows a schematic configuration of a conventional color image reading device. 1 is the original to be read, 7
2 is a halogen lamp, 2 is an imaging lens system, 3 is a 3P prism for color separation, and 4, 5, and 6 are imaging elements for blue, green, and red images, respectively. By the way, as shown in FIG. 2, which is an intensity spectral characteristic diagram of the halogen lamp 7, the intensity of the blue region is weaker than that of other color regions, and therefore the reading sensitivity, including the sensitivity of the image sensor, is also lower than that of FIG. 3. As shown in the figure, it tends to decrease in the blue region. Note that FIG. 3 shows an example of spectral sensitivity characteristics when a CCD is used as an image sensor.

For this reason, the voltage applied to the halogen lamp has traditionally been increased to increase the amount of light to compensate for the lack of sensitivity in the blue region. However, this is an unnecessary amount of light for the green and red areas, wastes power, and tends to cause saturation of the image sensor output, so an ND filter is installed in the optical path of the green and red areas. There was an inconvenience that I had to do.

The present invention has been proposed in view of the above points, and provides a color image that is equipped with a plurality of imaging optical systems having different lens apertures corresponding to the difference in reading sensitivity of each color region, and that makes it possible to correct the difference in reading sensitivity. The purpose is to provide a reading device.

Next, a color image reading device according to an embodiment of the present invention will be described. FIG. 4 is a schematic configuration diagram for explaining the principle of the present invention, with FIG. 4a being a top view and FIG. 4b being a side view. In the figure, 9 is an imaging lens system for red and green images;
is a color separation system for red and green images placed after the lens system 9; 5 is an image sensor placed on the green image plane; 6 is an image sensor placed on the red image plane; 10 is a blue image 11 is a color filter placed after the lens system 10 that does not pass any light other than blue; and 4 is an imaging element for blue images placed on the image plane of the lens system 10. Here, the aperture of the lens of the imaging lens system 10 is larger than that of the imaging lens system 9.

Next, the operation will be explained. The image of the document 1 illuminated by the halogen lamp 7 passes through the lens system 9, and is then separated into a red image and a green image by the color separation system 8, which are sent to the image sensors 6 and 5, respectively.
image is formed. On the other hand, the image of original 1 is captured by lens system 1.
After passing through the color filter 11 and the color filter 11, the image is formed on the image sensor 4 as a blue image. Since the lens aperture of the blue lens system 10 is made larger than the aperture of the lens of the lens system 9, it is possible to prevent the conventional case where the amount of blue light is weak and the sensitivity is lowered.

FIG. 5 is a schematic perspective view of a color image reading device according to an embodiment of the present invention. A document 1 is placed on a platen glass 14. halogen lamp 7
The illumination light from first illuminates part 1a of the manuscript,
The light is then guided by mirrors 14, 12, and 13 to an imaging lens system 10 for blue images and an imaging lens system 9 for red/green images. The light that has passed through the former passes through a color filter 11 and is sent to a blue image sensor 4.
The light passing through the latter is separated into colors by a red/green color separation system 8, and then images are formed on a green image pickup element 5 and a red image pickup element 6, respectively. The image is of a portion 1a of the original 1, and in order to obtain image information of the entire original 1, the halogen lamp 7 and mirrors 14, 12, and 13 are scanned in the direction of the arrow. Here, the halogen lamp 7 and the mirror 14, as well as the mirrors 12 and 13, move at the same speed, and the speed ratio between the mirror 14 and the mirrors 12 and 13 is as follows.
The ratio of 1:2 is set so that the optical path length from the first part 1a of the original to the image sensors 4, 5, and 6 does not change.

As explained above, according to the present invention, it is possible to correct the imbalance in sensitivity to a specific wavelength region caused by the spectral characteristics of a light source. It also prevents unnecessary energy consumption. Furthermore, since the lens systems are separated depending on the wavelength region, tolerance for chromatic aberration is increased. Furthermore, in the past, multiple image sensors were provided around one color separation system, making it difficult to arrange the position control mechanism for each image sensor, but in the present invention, the position of the image sensor is separated, making it easier. be.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of a conventional color image reading device, FIG. 2 is a spectral characteristic diagram of the intensity of a halogen lamp, FIG. 3 is a spectral characteristic diagram of the sensitivity of the reading device, and FIG. 4 is a diagram of the present invention. FIG. 5 is a schematic perspective view of a color image reading device according to an embodiment of the present invention. 1... Original, 2, 9, 10... Imaging lens system,
3...3P prism, 4-6...imaging element, 7...
Halogen lamp, 8... Red green color separation system, 11... Color filter, 12 to 14... Mirror, 15... Platen glass.

Claims (1)

[Scope of Claims] 1. In a color image reading device that forms a color original image using an imaging optical system, separates it into a plurality of color regions using a color separation system, and reads image information for each color region, reading each color region. A color image reading device comprising a plurality of the imaging optical systems having different lens apertures corresponding to sensitivity differences, and correcting the reading sensitivity differences. 2. The color image according to claim 1, wherein the plurality of imaging optical systems are an imaging optical system corresponding to a blue region and an imaging optical system corresponding to green and red regions. reading device.