JPH0937024A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To uniform an output voltage in simplified and inexpensive structure and to improve gradation reproducibility by providing a spectral correcting means in an optical path for correcting the spectral split of light made incident on a CCD image sensor into a certain direction so that the output value from the CCD image sensor concerning each spectral component can be averaged. SOLUTION: The light emitted from light sources 13 and 14 is transmitted through a light diffusion plate 28 and a multicolor original D, reflected on a reflection mirror 20, passed through an image forming lens 22 to a CCD image sensor 18 and inputted after the color is separated by a spectral filter mounted on respective line sensors 18R, 18G and 18B. Then spectral split filming is applied to the image forming lens 22 and light is made incident on the CCD image sensor 18 in the state of previously attenuating a color component corresponding to the line sensor having the highest spectral sensitivity so that the outputs of the respective line sensors 18R, 18G and 18B can be averaged. Therefore, the output values of respective spectral components can be averaged in a simple and inexpensive structure without performing any complicated control, and the output value of the CCD image sensor 18 can be made proper.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading device for reading an image of a multicolor original using a CCD image sensor.

[0002]

2. Description of the Related Art Conventionally, as an image reading apparatus as described above, while moving an original in a predetermined scanning direction for scanning, the original is illuminated by a light source such as a fluorescent lamp or a halogen lamp, and the illumination light is combined. It is generally known that an image is formed on a CCD image sensor by an image lens or the like (see, for example, JP-A-59-79676).

In such a CCD image sensor, when a light amount exceeding a permissible value is incident, the output voltage reaches a saturation voltage and accurate reading cannot be performed. Conversely, even when the light amount is excessively small, the output is output. Since the voltage is buried in the noise level, it becomes difficult to extract it as an effective output. For this reason, conventionally, an appropriate output is obtained by adjusting the exposure time of the original document or suppressing the amount of light incident on the CCD image sensor by providing a fixed diaphragm or an ND filter in the optical path from the original document to the CCD image sensor. Voltage is being secured.

[0004]

In recent years, as the CCD image sensor, blue, green, red (hereinafter, referred to as
The colors are called B, G, and R, respectively. The so-called three-line type in which the three line sensors with the filter of (1) are integrated has been provided. CC like this
If the D image sensor is used, it is possible to simultaneously read each color by scanning the original once, and the efficiency is dramatically improved.

However, in such a 3-line type CCD image sensor, there is a variation in the spectral sensitivity for each color of B, G and R, and there is a possibility that the output voltage may be significantly different accordingly. For example, in the example of FIG. 4, the output voltage of B is the highest and the output voltage of G is the lowest.

Therefore, when the light amount adjustment example is performed in the same manner as described above in this 3-line type CCD image sensor, for example, when the incident light amount is adjusted with reference to the output voltage for G, the output voltage for B reaches the saturation voltage. On the contrary, if the incident light amount is adjusted with reference to the output voltage for B, the output voltage for G may not be sufficiently obtained. That is, this 3-line type C
In the CD image sensor, since the spectral sensitivity of each line sensor varies, it is difficult to obtain an appropriate output voltage for all color components only by adjusting the light amount, and it is difficult to obtain good gradation reproducibility.

As a means for solving this inconvenience, Japanese Patent Laid-Open No. 6-78107 discloses that the charge accumulating time for each color of B, G and R is individually adjusted to make the output voltage uniform. However, with this means, the control of the charge storage time becomes complicated and the entire apparatus tends to be expensive. For this reason, it has been desired to develop a device that can make the output voltage uniform and improve the gradation reproducibility with a simpler and cheaper structure.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and a light source for illuminating a multicolor original and a spectral component for performing spectral analysis are provided according to the amount of received light. In an image reading apparatus including a CCD image sensor for outputting an electric signal of a different level and an image forming optical system for forming an illumination light flux of the multicolor original on the CCD image sensor, the light source is changed to the CCD image sensor. Spectral correction means for spectrally correcting the light incident on the CCD image sensor in the direction to reach the average value of the output value from the CCD image sensor for each spectral component is provided.

According to this structure, the light spectrally corrected by the spectral correction means is incident on the CCD image sensor, so that the output values of the CCD image sensor are averaged as compared with the case where the spectral correction is not performed. Therefore, the output values of the CCD image sensor for all spectral components can be easily adjusted to appropriate values.

Here, as the spectral correction means, a filter dedicated to spectral correction may be specially provided.
If the spectral coating is provided on the surface of the optical device provided in the area from the light source to the CCD image sensor, the structure is further simplified and the cost is reduced. Specifically, the location where the spectral coating is provided is the surface of the imaging lens forming the imaging optical system or the C from the original.
The surface of the heat ray cut filter or the reflection mirror provided in the optical path leading to the CD image sensor, the above CC
The surface of the cover glass of the D image sensor is suitable.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION One embodiment of the present invention is shown in FIGS.
This will be described with reference to FIG.

The image reading apparatus shown in FIG. 2 is provided with a base 10, a light source housing 12 is fixed on the base 10, and a first light source 13 and a second light source 14 are housed in the light source housing 12. Has been done. Light source housing 12
1 has a container shape extending in the depth direction of FIG. 1 and opening upward, and a light diffusing plate 28 is disposed on the upper surface thereof. The first light source 13 and the second light source 14 are constituted by a thin and long fluorescent lamp in the form shown here, and extend in parallel with the light source housing 12.

In the present invention, a single light source may be used regardless of the specific structure and number of the light irradiating means, or an illumination device other than a fluorescent lamp such as a halogen lamp may be used. is there.

Above the light source housing 12, a document holder (document supporting portion) 16 for holding a translucent multicolor document D is horizontally arranged. This document holder 16
Is slidably supported on the base 10 along a linear guide 30 extending in a direction orthogonal to the longitudinal direction of the light source housing 12 and both light sources 13 and 14, and a nut (not shown) is fixed to the bottom surface thereof. . Further, an original scanning motor 32 is fixed on the base plate 10, and a ball screw 34 extending parallel to the linear guide 30 is rotatably supported. The ball screw 34 outputs the original scanning motor 32. It is connected to the shaft and screwed to the nut. Therefore, the multicolor original D is scanned in the direction parallel to the linear guide 30 by the operation of the original scanning motor 32.

A CCD image sensor 18 is arranged at a position above the document holder 16 and at a position separated laterally. A so-called three-line type CCD image sensor 18 is used, and details thereof will be described later.

A reflection mirror 20 for reflecting the light transmitted through the document D from the light sources 13 and 14 is provided directly above the document holder 16. At a position between the reflection mirror 20 and the CCD image sensor 18, an image forming lens 22 for forming an image of the reflected light of the reflection mirror 20 on the CCD image sensor 18 is provided, and in front of the image forming lens 22. A heat ray cut filter 24 is provided. The heat ray cut filter 24 cuts a wavelength component having a predetermined value (for example, 700 nm) or more out of the light reflected by the reflection mirror 20, and smears (an image oozes out from the edge of the image due to this wavelength component, This is to prevent the occurrence of a phenomenon that the image is blurred as if it was dirty.

Next, the CCD image sensor 18 and the apparatus related thereto will be described with reference to FIG.

The CCD image sensor 18 includes R, G, B
Three line sensors 18R provided for each color of
18G and 18B are integrated, and each line sensor 18R, 18G, and 18B is equipped with a spectral filter that separates each color of R, G, and B, and the color component corresponding to each filter is provided to each line sensor 18R. , 18G, 18B
It is designed to be incident on. Each line sensor 18
The R, 18G, and 18B are configured to output a voltage according to the amount of incident light to the gradation correction means 46 via the A / D converter 44.

The control device 40 shown in the drawing is a document scanning motor 3
By outputting a control signal to 2, the document scanning motor 32 is operated to intermittently drive the document holder 16, and the driver 42 is provided with the line sensors 18R and 18R.
The G and 18B charge accumulation time designation signals are output. The driver 42 controls each line sensor 1 so that the charge storage time designated by the control device 40 can be obtained.
The drive signals (start signal and stop signal) are output to 8R, 18G, and 18B at a predetermined timing.

By the way, the CCD image sensor 18
Then, there is variation in the spectral sensitivity of each line sensor 18R, 18G, 18B. Therefore, in this image reading device,
On the surface of the imaging lens 22 shown in FIG. 1 and FIG. 2, the output voltage value of the line sensor having the lowest spectral sensitivity among the line sensors 18R, 18G and 18B is made to approach the output voltage value of the other line sensor. In addition, a spectral coating for attenuating the wavelength component of the color corresponding to the other line sensor to an appropriate degree is provided.

As the material of the spectral coating, the material generally used in the past can be applied as it is, and an interference filter or the like formed of a multilayer film is suitable.

Next, the operation of this device will be described.

A multicolor original D having a light transmitting property on the original holder 16
Is held, the first light source 13 and the second light source 14 are turned on in this state, and the multi-color original D is moved in the direction of arrow X in FIG. By doing so, the CCD image sensor 18
The original image is read by.

More specifically, the light emitted from the light sources 13 and 14 passes through the light diffusing plate 28 and the multicolor original D, is reflected by the reflecting mirror 20, and passes through the imaging lens 22 to the CCD.
Reaching the image sensor 18, each line sensor 18R, 1
Color separation is performed by the spectral filters attached to 8G and 18B, and the color separation is input. Each line sensor 1 receives this incident light
8R, 18G, and 18B perform photoelectric conversion, and the driver 42
The charge is accumulated for a time corresponding to the drive signal input from the device, and the voltage corresponding to the charge is output.

Here, in the conventional image reading apparatus, it was difficult to make the dynamic range of each line sensor proper due to the spectral sensitivity of each line sensor 18R, 18G, 18B. In the device at
Since the imaging lens 22 is provided with a spectral coating and light is incident on the CCD image sensor 18 in a state where the color component corresponding to the line sensor having the highest spectral sensitivity is attenuated in advance, each line sensor 18R, The output voltages of 18G and 18B are averaged (that is, the difference in spectral sensitivity characteristic is absorbed). Therefore, the output signal of the control device 40 is used to adjust the interval time (that is, the document exposure time) of intermittent document driving by the document scanning motor 32, and the driver 4 is controlled.
2 line signals 18R, 18G,
By collectively adjusting the charge storage time of 18B, the output voltage values of all the line sensors 18R, 18G, and 18B can be kept within a suitable range.

These line sensors 18R, 18G, 18
The output voltage of B is the amplifier and A / D converter 4 not shown.
4 is input to the gradation correction means 46. The gradation correction means 46 corrects the output signal for each color component in consideration of the spectral correction amount by the spectral coating.
The output signal of the gradation correction means 46 is transferred as image data to the image memory in the subsequent stage and written therein.

In this embodiment, the imaging lens 22
Is provided on the surface of other optical devices, for example, on the surface of the heat ray cut filter 24, the reflective surface of the reflection mirror 20, and the surface of the cover glass of the CCD image sensor 18, the spectral film is provided. Also, the same effect as described above can be obtained.

In addition to the above optical equipment, a filter dedicated to spectral correction may be provided in the optical path from the multicolor original D to the CCD image sensor 18.

[0029]

As described above, according to the present invention, a multicolor original is illuminated by a light source, and its image is displayed in a so-called multi-line type CC.
In an image reading device for reading with a D image sensor, the CCD image sensor is made to enter the CCD image sensor in the optical path from the light source to the CCD image sensor in a direction to average the output voltage value of the CCD image sensor for each color component. Since the spectral correction means for spectrally correcting the light that is emitted is provided, it is possible to average the output values for each spectral component with a simple and inexpensive structure without executing complicated control, and thus for all spectral components. The output value of the CCD image sensor can be kept within an appropriate range, and there is an effect that a good image can be read.

In particular, when the spectral correction means is provided with a spectral coating on an optical device provided in a region from the light source to the CCD image sensor, a filter or the like dedicated to spectral correction is not provided, There is an effect that the output values can be averaged with a simpler and cheaper structure.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional front view showing an embodiment of an image reading apparatus according to the present invention.

FIG. 2 is a perspective view of the image reading apparatus.

FIG. 3 is a block diagram showing a CCD image sensor provided in the image reading device and peripheral devices thereof.

FIG. 4 is a graph showing an example of incident light wavelength-relative sensitivity of a CCD image sensor.

[Explanation of symbols]

 13 First Light Source 14 Second Light Source 16 Document Holder (Document Support) 18 CCD Image Sensor 20 Reflecting Mirror 22 Imaging Lens 24 Heat Ray Cut Filter D Multicolor Document

Claims (6)

[Claims] 1. A light source for illuminating a multicolor original document, a CCD image sensor for performing spectral analysis and outputting an electric signal of a level corresponding to the amount of received light for each spectral component, and an illumination luminous flux of the multicolor original document for the CCD. In an image reading apparatus including an image forming optical system for forming an image on an image sensor, the light incident on the CCD image sensor in the optical path from the light source to the CCD image sensor is described above for each spectral component. An image reading apparatus comprising a spectral correction means for performing spectral correction in a direction in which output values from a CCD image sensor are averaged. 2. The image reading apparatus according to claim 1, wherein
An image reading apparatus characterized in that a spectral coating is provided on a surface of an optical device provided in a region from the light source to the CCD image sensor as the spectral correction means. 3. The image reading apparatus according to claim 2, wherein
An image reading apparatus characterized in that a spectral coating is provided on a surface of a lens constituting the imaging optical system as the spectral correction means. 4. The image reading device according to claim 2,
An image reading apparatus characterized in that a heat ray cut filter is provided in an optical path from the document to the CCD image sensor, and a spectral film is provided on a surface of the heat ray cut filter as the spectral correction means. 5. The image reading apparatus according to claim 2,
An image reading apparatus characterized in that a reflection mirror is provided in an optical path from the document to the CCD image sensor, and a spectral coating is provided on a reflection surface of the reflection mirror as the spectral correction means. 6. The image reading device according to claim 2,
An image reading device characterized in that a spectral coating is provided on a surface of a cover glass of the CCD image sensor as the spectral correction means.