JPH05110767A - Color original reader - Google Patents

Abstract

PURPOSE:To generate an accurate picture signal without an error in each component without complicated configuration by forming an image of a light of plural color components extracted by a color separate means having a different transmission rate of each color component at a prescribed rate to a photoelectric conversion means. CONSTITUTION:A reflected light from a light source 1 is reflected in a mirror 3, a color filter 4 is used to separate the light into red, green and blue components and the image of the light of each component obtained by the color filter 4 is formed on a line image sensor 6. The color filter 4 consists of a filter R, a filter G and a filter B and the type of material and the thickness of the filter are properly adjusted depending on the spectrum sensitivity characteristic and the spectrum distribution characteristic of the light source 2 and the transmission rate is relatively made different to cancel the ununiformed spectrum distribution of the light source 2 and the spectrum sensitivity of the line image sensor 6. Thus, an accurate picture signal is obtained without a correction circuit.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art In a facsimile machine or a digital copying machine, a line sensor formed by arranging a large number of photoelectric conversion elements one-dimensionally converts a reflected light image from an original into an electric signal to read the original. Further, when reading a color original, three filters (R filter, G filter, B filter) that transmit each of the red, green and blue light components are provided, and the line sensor is used while switching these three filters. By performing photoelectric conversion, a red signal (R signal), a green signal (G signal), and a blue signal (B signal) are obtained. Where R filter, G filter and B filter
The transmittances of the filters are equal to each other as shown in FIG.

However, the line sensor has a spectral sensitivity characteristic as shown in FIG. 6, for example, and the sensitivity for each wavelength is not uniform. The light source for illuminating the original is, for example, as shown in FIG.
It has a spectral distribution characteristic as shown in, and the amount of light is not uniform for each wavelength. Therefore, the spectral sensitivity characteristic of the entire device is as shown in FIG. 8, for example. As can be seen from this figure, there is a difference in the relative sensitivities of the red, green, and blue components, and even when the same brightness is read, the obtained signal level differs for each color. Therefore, an accurate image signal cannot be obtained.

[0004]

As described above, the conventional color original reading device has a problem that the spectral sensitivity characteristics of the entire device are biased and an accurate image signal cannot be obtained. It is conceivable to provide a correction circuit for correcting the signal obtained by the line sensor in order to eliminate this point, but the configuration becomes complicated.

The present invention has been made in consideration of such circumstances, and an object thereof is to generate an accurate image signal without error for each color component without complicating the configuration. An object of the present invention is to provide a color original reading device that can be used.

[0006]

SUMMARY OF THE INVENTION According to the present invention, the transmittance of each color component is changed at a predetermined ratio according to the spectral characteristics of other optical systems such as a light source and a line image sensor. Light of a plurality of color components extracted by the color separation means is focused on a photoelectric conversion means such as a line image sensor.

[0007]

By taking such means, the nonuniformity of the spectral characteristics of other optical systems such as the light source and the line image sensor is canceled by the difference in the transmittance of the color separation means.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 is a view showing the arrangement of the color document reading apparatus according to this embodiment. In the figure, 1 is a document to be read. A white light source 2 irradiates the original 1 with light. The reflected light from the light source 1 is reflected by the mirror 3 and then separated into red, green and blue components by the color filter 4. The light of each component obtained by the color filter 4 is imaged on the line image sensor 6 by the lens 5. The line image sensor 6 generates and outputs an electric signal corresponding to the optical image thus formed.

FIG. 3 is a diagram showing the structure of the color filter 4. As shown in this figure, the color filter 4 is configured by attaching an R filter 8, a G filter 9 and a B filter 10 to each of three parallel slits formed in the frame 7. The R filter 8 transmits a light component near 650 nm, that is, a red component. G filter 9 is 550n
It transmits the light component near m, that is, the green component. The B filter 10 transmits a light component near 450 nm, that is, a blue component. The materials and thicknesses of these filters are appropriately adjusted according to the spectral sensitivity characteristic of the line image sensor 6 and the spectral distribution characteristic of the light source 2, and the spectral sensitivity of the line image sensor 6 and the spectral distribution of the light source 2 are not uniform. The relative transmittance is made different so as to cancel out the difference. In this embodiment, the transmittance ratio of the R filter 8, the G filter 9 and the B filter 10 is [0.6: 0.5: 1]. The spectral transmittance characteristic of this color filter 4 is shown in FIG.

Next, the operation of the color original reading apparatus configured as described above will be described. First, R of the color filter 4
With the filter 8 positioned in the optical path, the reading surface (downward in the figure) of the original 1 is illuminated by the light source 2 while conveying the original 1 in the direction of arrow a in the figure. Then, the reflected light from the original 1 is photoelectrically converted by the line image sensor 6 to obtain an image signal for the red component.

The color filter 4 can be moved up and down by a solenoid (not shown) as shown by an arrow B in the figure. After obtaining the image signal for the red component as described above, the G filter is used. 9 and the B filter 10 are sequentially positioned in the optical path, and the same operations as described above are performed. As a result, image signals for the green component and the blue component are obtained.

Although the image signal for each color component is generated in this manner, the transmittances of the R filter 8, the G filter 9, and the B filter 10 constituting the color filter 4 are made different from each other. 7 shows the non-uniformity of the spectral sensitivity of the line image sensor 6 as shown in FIG.
The non-uniformity of the spectral distribution of the light source 2 as shown in FIG.
The spectral sensitivity characteristics as a whole are uniform as shown in FIG.

Thus, according to the present embodiment, the line image sensor 6 outputs signals of the same level regardless of color if the brightness is equivalent. Therefore, an accurate image signal can be obtained without a correction circuit.

The present invention is not limited to the above embodiment. For example, although a filter is used as the color separation means in the above embodiment, a prism or the like can be used.

In the above embodiment, the transmittance ratios of the R filter 8, G filter 9 and B filter 10 are [0.
6: 0.5: 1], but this changes depending on the spectral sensitivity characteristic of the line image sensor 6 and the spectral distribution characteristic of the light source 2. Further, the ratios of the transmittances of the R filter 8, the G filter 9, and the B filter 10 are not determined only in accordance with the spectral sensitivity characteristic of the line image sensor 6 and the spectral distribution characteristic of the light source 2, and if necessary, such as lenses. The characteristics of other factors should be considered. In addition, various modifications can be made without departing from the scope of the present invention.

[0016]

According to the present invention, the color separation means such as a color filter, in which the transmittance of each color component is varied at a predetermined ratio according to the spectral characteristics of another optical system such as a light source or a line image sensor. Since light of a plurality of color components extracted by is imaged on a photoelectric conversion means such as a line image sensor, an accurate image signal without error for each color component is generated without complicating the configuration. It becomes a color original reading device capable of performing.

[Brief description of drawings]

FIG. 1 is a diagram showing a spectral transmittance characteristic of a color filter applied to a color original reading apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a color original reading device according to an embodiment of the present invention.

3 is a diagram showing a specific configuration of a color filter 6 in FIG.

FIG. 4 is a diagram showing spectral sensitivity characteristics of the entire color document reading apparatus shown in FIG.

FIG. 5 is a diagram showing a spectral transmittance characteristic of a color filter applied to a conventional color original reading apparatus.

FIG. 6 is a diagram showing a spectral sensitivity characteristic of a line image sensor applied to a color original reading device.

FIG. 7 is a diagram showing a spectral distribution characteristic of a light source applied to a color original reading device.

FIG. 8 is a diagram showing a spectral sensitivity characteristic of the entire conventional color document reading apparatus.

[Explanation of symbols]

1 ... Original, 2 ... Light source, 3 ... Mirror, 4 ... Color filter, 5 ... Lens, 6 ... Line image sensor, 7 ... Frame,
8 ... R filter, 9 ... G filter, 10 ... B filter.

Claims (1)

[Claims] 1. Reflected light from a document to be read is separated into a plurality of color components by a color separation means and input to a photoelectric conversion means,
A color original reading device for generating an electric signal for each color component by photoelectric conversion means, wherein the color separation means has the transmittance of each color component varied at a predetermined ratio according to the spectral characteristics of other optical systems. A color original reading device characterized by the above.