JPH0195663A - Color picture reader - Google Patents

Abstract

PURPOSE:To obtain high reading accuracy while making constant an output signal for a red, a green and a blue obtained from the line sensor such as a CCD by using an optical member to improve a spectral illumination distribution mainly for a blue light area on an original surface. CONSTITUTION:A direct light flux from a light source 1 and an indirect light flux after the reflection of the direct light flux by a reflection mirror 4 illuminate an original surface 1, and a part of the light flux, which is not directly light-guided on the original surface 1, illuminates through an optical member possessing a high reflectance into the blue light area on the original surface. That is, the titled device is adjusted so that the spectral illumination distribution of the blue area on the original surface may be improved, and the spectral illumination distribution on the original surface 1 may be uniform as much as possible. Thus, the output signal for the red, green and blue obtained from the line sensor such as the CCD can be made approximately constant, and the high reading accuracy can be easily obtained.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a color image reading device, and particularly to a color image reading device that reads color image information on a document surface with high accuracy by using a line sensor equipped with color separation means. The present invention relates to a color image reading device suitable for a color scanner, a color facsimile, and the like.

(Prior art) Conventionally, color image information on the document surface is transmitted through an optical system.
Various devices have been proposed that form an image on the surface of a line sensor such as a CD and read color image information using the output signal from the line sensor at this time.

FIG. 7 is a schematic diagram of a conventional color image reading device. In the figure, a document surface 71 placed on a glass stand 72 is illuminated by a light beam from a light source 73 such as a halogen lamp.

Then, the color image information on the original surface 71 is transmitted through the scanning mirrors 74, 75, 76, and converted into a color image by the imaging lens 77.
The image is formed on the surface of a photoelectric conversion element 78, such as a CD, in which a plurality of light receiving elements are arranged in one dimension. For COD, for example, as shown in FIG. 8, R, G, and B filters are provided for each pixel 79, and reading is performed for each color.
A color image signal is obtained for the image.

In such conventional color image reading devices, a halogen lamp is used to illuminate the document surface, so the spectral illuminance distribution on the document surface is different from that in the red and green regions, for example, as shown in Figure 9. As a result, the intensity of the blue region becomes lower. For this reason, conventionally, in order to make the red, green, and blue output signals from the CCD constant, the blue output signal was amplified by an electrical correction means and adjusted to the reference level. However, when the blue output signal is amplified, noise is generated, and there is a problem that it is not possible to amplify the blue output signal too much.

On the other hand, in order to increase the amount of light in the blue region of the illumination system, three light sources for red, green, and blue are prepared as illumination light sources, and a color filter for each color light is placed in front of each of these light sources. There is also a method in which each light source is arranged and blinks at a different frequency. However, this method requires a mechanism for properly arranging and adjusting the three light sources, and for controlling the drive of each light source, resulting in a problem that the entire device becomes complicated.

(Problems to be Solved by the Invention) The present invention uses a line sensor such as a CCD that captures color image information on the document surface illuminated by an illumination means, and when reading the color image information in correspondence with each color light, mainly the blue color on the document surface is read. By using an optical member that improves the spectral illuminance distribution in the optical region, C
An object of the present invention is to provide a color image reading device that can obtain high reading accuracy by making output signals for red, green, and blue colors obtained from a line sensor such as an OD constant.

(Means for solving the problem) A document surface on which color image information is recorded is irradiated with a light beam from an illumination device, and the reflected light from the document surface is detected by a detection device via a color separation device. When reading color image information, a part of the light beam other than the light beam directly incident on the document surface from the illumination means is guided onto the document surface via an optical member having a high reflectance in the blue region. That's what I did.

(Embodiment) FIG. 1 is a schematic diagram of an optical system according to an embodiment of the present invention. In the figure, reference numeral 1 denotes a document on which color image information is recorded. There are two glass stands on which original 1 is placed. 3 is a light source such as a halogen lamp, and 4 is a reflecting shade, which is made of a concave mirror, a parabolic mirror, an elliptical mirror, etc. The light source 3 and the reflective shade 4 constitute one element of the illumination means 10. Reference numeral 5 denotes an optical member, which mainly consists of a plane mirror, a concave mirror, an ellipsoidal mirror, a parabolic mirror, etc., coated with a vapor-deposited film such as a dichroic film that reflects blue light with high reflectance. Reference numeral 6 denotes a first scanning mirror, which moves at a constant speed V in the direction of the arrow while being spaced apart from the document surface 1 at a constant distance. 7 is a second scanning mirror, which has two mirrors 7a and 7b and is similar to the first scanning mirror 6.
It scans in the same direction as at a constant speed of V/2. 8 is an eyepiece; 9 is a detection means such as a CCD; for example, a second
As shown in the figure, there are three line sensors 9a, 9 equipped with color separation means, such as color filters, set in front to have spectral sensitivities for the three primary colors red, green, and blue.
b, 9c.

FIG. 3 is an explanatory diagram when the document surface 1 is illuminated by the illumination means 10 and the optical member 5 in FIG. 1. In this embodiment, the document surface 1 is illuminated by the direct light beam from the light source 1 and the indirect light beam after being reflected by the reflecting mirror 4, and the direct light beam from the illumination means 10 is directly guided onto the document surface 1. A part of the light beam that is not reflected is illuminated onto the surface of the document via an optical member 5 having a high reflectance in the blue light region as shown in FIG. 4, for example.

This improves the spectral illuminance distribution in the blue region on the document surface, and adjusts the spectral illuminance distribution on the document surface 1 to be as uniform as possible.

In particular, in this embodiment, when a halogen lamp is used as a light source, the spectral reflectance characteristic of the optical member 5 is
As shown in the figure, using a reflective film that is within the range of plus or minus 10% of 92% at a wavelength of 400 nm, 74% at a wavelength of 450 nm, 57% at a wavelength of 500 nm, 46% at a wavelength of 550 nm, and 36% at a wavelength of 600 nm. is good.

In this embodiment, the apparatus configured as described above is used to
The top is scanned by the first scanning mirror 6 and the second scanning mirror 7, and the three line sensors 9a and 9b are scanned by the imaging lens 8.
, 9c, and sequentially reads color image information on the document surface 1. At this time, the color image information is read in red.

Three line sensors 9a for green and blue.

The output signals from 9b and 9c are provided under conditions such that the spectral characteristics are uniform as shown in FIG. 5, for example.

FIG. 6 is a schematic diagram of an optical system according to another embodiment of the present invention. In this embodiment, a 3P prism 61 is arranged behind the imaging lens 8 as a color separation means to separate the light beam from the imaging lens 8 into red, green, and blue, and each line sensor 9a
, 9b, and 9c. Other configurations are the first
It is exactly the same as the figure.

In this example, as a means to increase the spectral illuminance distribution in the blue region on the document surface, a vapor deposition film having a high reflectance in the blue region or a vapor deposition film that relatively lowers the reflectance of green and red compared to blue is used. A film may also be applied to the reflective shade 4.

Alternatively, one area of the reflective shade may be coated with a vapor-deposited film having a high reflectance particularly in the blue region.

(Effects of the Invention) According to the present invention, by using the optical member as described above and improving the spectral illumination distribution for the blue light region on the document surface, the red color obtained from a line sensor such as a CCD,
It is possible to achieve a color image reading device with a simple configuration that can easily obtain high reading accuracy in which the output signals for green and blue can be kept substantially constant.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an optical system according to an embodiment of the present invention, FIG.
3 is an explanatory diagram of a part of FIG. 1, FIG. 4 is an explanatory diagram of the spectral reflectance of the optical member in the present invention, and FIG. 5 is an explanatory diagram of the spectral reflectance of the optical member in the present invention. 6 is a schematic diagram of an optical system according to another embodiment of the present invention. FIG. 7 is a schematic diagram of a conventional color image reading device.
This figure is an explanatory diagram of a part of FIG. 7, and FIG. 9 is an explanatory diagram of the spectral illuminance distribution on the document surface when the color image reading device shown in FIG. 7 is used. In the figure, 1 is the document surface, 2 is the glass stand, 3 is the light source, 4 is the reflective shade, 5 is the optical member, 6 is the first scanning mirror, 7 is the second scanning mirror, 8 is the imaging lens, and 9 is the detection It is a means. Patent applicant Canon Co., Ltd. Chapter 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 400' 500 600
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Claims (1)

[Claims] When reading color image information by illuminating the document surface on which color image information is recorded with a light flux from the illumination means and detecting the reflected light from the document surface by the detection means via the color separation means, the illumination A color image reading device characterized in that a part of the light beam other than the light beam directly incident on the document surface from the means is guided onto the document surface via an optical member having a high reflectance in the blue region. .