JPH0937027A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To always provide the output of a CCD image sensor at a proper level by providing a variable diaphragm means in an optical path from a light source to the CCD image sensor for steplessly changing the quantity of light made incident on the CCD image sensor. SOLUTION: Concerning an image reader provided with light sources 13 and 14 with which an original D is irradiated, CCD image sensor 18 for outputting an electric signal at a level corresponding to the quantity of received light, and image forming optical system for forming the image of light flux, with which the original D is irradiated, on the CCD image sensor 18; in the optical path from the light sources 13 and 14 to the CCD image sensor 18, a variable diaphragm 26 is provided for steplessly changing the quantity of light made incident on the CCD image sensor 18. By such a constition since the quantity of light made incident on the CCD image sensor 18 is steplessly controlled by the variable diaphragm 26 while considering dispersion in the quality of the image forming optical system, etc., even when there is such dispersion, the output of the CCD image sensor 18 at the proper level can be always obtained and image reading can be satisfactorily performed.

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 that reads using a D 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.

Therefore, conventionally, after securing a sufficient amount of illumination light of the document, a fixed diaphragm or an ND filter or the like is provided in the optical path from the document to the CCD image sensor to provide an appropriate amount of light incident on the CCD image sensor. An appropriate output voltage is secured by narrowing down to the level.

[0005]

The factors that affect the amount of incident light are, in addition to the fixed diaphragm for adjusting the amount of light, the reflectance of the reflection mirror, the brightness of the imaging lens, and the CCD image. There is sensitivity of the sensor itself. There are variations in the quality of these optical components, and these variations may reach several tens of percent in some cases.
If there is such a large variation, it is impossible to deal with it with a single type fixed aperture, and even when dealing with a predetermined number of ND filters, since the transmittance is standardized, the above variation will occur. It is very difficult to fine-tune the amount of light in consideration. Further, in order to reduce the variation of the optical components, it is necessary to use extremely high-quality optical components, which results in a significant increase in cost.

Further, in recent years, as the CCD image sensor, three line sensors having filters of blue, green, and red (hereinafter, each color is referred to as B, G, and R, respectively) are integrated to form a single line sensor. A so-called 3-line type that enables simultaneous reading of each color by one time of original scanning has been provided, but in such a 3-line type CCD image sensor, for each color of B, G and R, There are variations in the spectral sensitivity of, and accordingly, a significant difference may occur in the output voltage. For example, in the example of FIG. 6, 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.

In view of the above circumstances, the present invention can easily and appropriately adjust the output value of the CCD image sensor without using high quality optical parts, and more preferably, a so-called multi-line type CCD image. An object of the present invention is to provide an image reading apparatus that can appropriately adjust the sensor output value regardless of the variation in the spectral sensitivity of each line sensor even when the sensor is used.

[0009]

According to the present invention, a light source for illuminating a document, a CCD image sensor for outputting an electric signal having a level corresponding to the amount of received light, and an illumination light flux of the document are imaged on the CCD image sensor. In the image reading apparatus including the image forming optical system, the variable diaphragm means for continuously changing the light amount of the light incident on the CCD image sensor in the optical path from the light source to the CCD image sensor. Is provided.

According to this structure, even if there are variations in the quality of the imaging optical system, the variable diaphragm means continuously adjusts the amount of light incident on the CCD image sensor in consideration of the variations. The output of the CCD image sensor at an appropriate level can always be obtained, and the image can be read well.

The location of the variable diaphragm means is not particularly limited. However, if the variable diaphragm means is incorporated into the lens barrel of the lens forming the image forming optical system, this lens barrel is supported by the variable diaphragm means. It can also be used as a member, and the relative positioning of the variable diaphragm means and the lens becomes more accurate.

Further, a light source for illuminating a multicolor original, a CCD image sensor for performing a spectrum and outputting an electric signal of a level corresponding to the amount of received light for each spectral component, and an illumination light flux of the multicolor original for the CCD. In an image reading apparatus having an image forming lens for forming an image on an image sensor, the light incident on the CCD image sensor is described above for each spectral component in the optical path from the light source to the CCD image sensor. By providing the spectral correction means for spectrally correcting the output value from the CCD image sensor in the direction of averaging and the variable diaphragm means together, the output value of the CCD image sensor is averaged by the spectral correction means. By adjusting the light amount by the variable diaphragm means, all output values can be increased or decreased collectively. Therefore, even if there are variations in the spectral sensitivities of the CCD image sensor, all output values can be kept within an appropriate range. Also,
By adjusting the variable diaphragm in the opening direction, it is possible to adjust the output voltage level of the CCD image sensor, which is lowered by the spectral correction, to be increased on average.

In this case, a filter or the like dedicated to spectral correction may be specially provided as the spectral correction means, but the spectral correction is performed on the surface of an optical device provided in a region from the light source to the CCD image sensor. If the coating is provided, the structure becomes simpler and cheaper.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION One embodiment of the present invention is shown in FIGS.
A description will be given based on FIG.

The image reading apparatus shown in FIG. 2 includes 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 configuration and number of light irradiation 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 apart from it laterally. A so-called 3-line type CCD image sensor 18 is used, and the 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.

Further, as a feature of this apparatus, as shown in FIG. 3, a variable diaphragm 26 is integrally incorporated in the lens barrel 22a of the imaging lens 22. This variable diaphragm 26
Are equivalent to those used as diaphragms and shutters in a normal camera, and a plurality of blades 23 (five in the illustrated example) arranged in the circumferential direction as shown in FIG.
And a rotary cylinder 25. A pin 23a is provided so as to project from the inner edge of each blade 23, and each blade 23 is supported on the side of the lens barrel 22a so as to be swingable about this pin 23a. Further, an elongated hole 23b is formed in each blade 23 at a position slightly apart from the pin 23a.

On the other hand, the rotary barrel 25 is composed of the lens barrel 22a.
The blade 25 is rotatably mounted, and a pin 25b fitted in the elongated hole 23b of each of the blades 23 is provided on the inner peripheral edge of the pin 25b. Therefore, the rotation of the rotary cylinder 25 causes the blades 23 to simultaneously swing in the same direction by the same amount, whereby the central opening area surrounded by the blades 23, that is, the diaphragm area is continuously changed. .

On the outer peripheral surface of the rotary cylinder 25, tooth portions 25a which form a timing pulley are formed. on the other hand,
A pulse motor 27 shown in FIG. 3 is provided on the side of the image forming lens 22, and a timing belt 29 is stretched between the timing pulley 27a fixed to the output shaft of the pulse motor 27 and the tooth portion 25a. There is. Therefore, by operating the pulse motor 27, it is possible to rotationally drive the rotary cylinder 25, that is, to adjust the aperture area (substantially stepless adjustment).

In the present invention, regardless of the specific configuration of the variable diaphragm means, various known ones can be applied within the range in which the amount of light incident on the CCD image sensor can be adjusted steplessly. As described above, the variable diaphragm means is used as the imaging lens 2
If it is incorporated in the second lens barrel 22a, this lens barrel 22
a can also be used as a support member for the variable diaphragm 26, and
There is an advantage that relative positioning between the variable diaphragm 26 and the imaging lens 22 becomes more accurate and easy.

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, those generally used in the past can be applied as they are, 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 diffusion plate 28 and the multicolor original D, is reflected by the reflection mirror 20, and is transmitted 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).

While averaging the output voltage in this way,
The diaphragm area of the variable diaphragm 26 is adjusted to an appropriate area by operating the pulse motor 27 in advance (that is, C
By adjusting the amount of light incident on the CD image sensor 18 to an appropriate amount), all the line sensors 18R, 1R
The output voltage values of 8G and 18B can be kept within a suitable range. The variable diaphragm 26 is capable of continuously adjusting the amount of incident light by rotating the rotary cylinder 25 in a stepless manner. Therefore, the variable mirror 26, optical devices such as the reflection mirror 20 and the imaging lens 22, and C.
Even if there are variations in the characteristics of the CD image sensor 18, the amount of light incident on the CCD image sensor 18 can be easily and finely adjusted to an appropriate amount in consideration of this variation.

The line sensors 18R, 18G,
The output voltage of 18B is input to the gradation correction means 46 via an amplifier (not shown) and the A / D converter 44. 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, a spectral coating is provided on the surface of the imaging lens 22, but the surface of other optical equipment,
For example, a spectral film may be provided on the surface of the heat ray cut filter 24, the reflective surface of the reflection mirror 20, or the surface of the cover glass of the CCD image sensor 18, or a filter dedicated to spectral correction may be provided separately from these optical devices. It may be interposed in the optical path from the multicolor original D to the CCD image sensor 18.

Further, instead of simultaneously reading each color component of the image of the multicolor original D by the three-line CCD image sensor as described above, when reading an image of a black-and-white original by an ordinary one-line CCD image sensor, The variable diaphragm is also used when the image of the multicolor original is read by interposing the spectral filters for R, G, and B between the multicolor original and the one-line CCD image sensor while exchanging them one by one. By providing 26, the effect that the output voltage of the CCD image sensor can be easily adjusted to an appropriate value can be obtained. Further, the present invention is not limited to the transillumination type illumination of the original document, but can be applied to the illumination of the original reflection type.

[0037]

As described above, according to the present invention, in the optical path from the light source illuminating the original to the CCD image sensor for image reading, the amount of light incident on the CCD image sensor is steplessly changed. Since the variable diaphragm means for changing is provided, even if there are variations in the quality of the image forming optical system, etc., in consideration of this variation, the variable diaphragm means continuously changes the amount of light incident on the CCD image sensor. By making fine adjustments, the output of the CCD image sensor at an appropriate level can always be obtained, and there is an effect that image reading can be performed satisfactorily.

Here, if the variable diaphragm means is incorporated into the lens barrel of the lens forming the image forming optical system, this lens barrel can also be used as a supporting member of the variable diaphragm means, and further,
The effect that the relative positioning between the variable diaphragm means and the lens can be performed more accurately and easily can be obtained.

Further, in an image reading apparatus in which a multicolor original is illuminated by a light source and an image thereof is read by a so-called multi-line type CCD image sensor, the CC from the light source is used.
Spectral correction means for spectrally correcting the light incident on the CCD image sensor in the direction of averaging the output voltage values of the CCD image sensor for each color component in the optical path to the D image sensor, and the variable diaphragm. If the means is also provided, the output values for the respective spectral components are averaged by a simple and inexpensive structure in which only the spectral correction means is provided, and then the stepless light amount adjustment by the variable diaphragm means is performed. By doing so, even when the spectral sensitivity of the CCD image sensor varies, the output values of the CCD image sensor for all spectral components can be kept within an appropriate range, and there is an effect that good image reading can be performed.

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 perspective view of an imaging lens provided in the image reading apparatus.

FIG. 4 is a front view of a variable diaphragm incorporated in the lens barrel of the imaging lens.

FIG. 5 is a block diagram showing a CCD image sensor provided in the image reading device and peripheral devices thereof.

FIG. 6 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 18 CCD Image Sensor 20 Reflecting Mirror 22 Imaging Lens 22a Lens Tube 24 Heat Ray Cut Filter 26 Variable Aperture D Multicolor Original

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location // G03B 9/02 H04N 1/04 D

Claims (4)

[Claims] 1. A light source for illuminating a document, a CCD image sensor for outputting an electric signal at a level according to the amount of received light, and an image forming optical system for forming an illumination light beam of the document on the CCD image sensor. Image reading device,
An image reading apparatus comprising variable diaphragm means for continuously changing the amount of light incident on the CCD image sensor in an optical path from the light source to the CCD image sensor. 2. 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. Spectral correction means for spectrally correcting the output values from the CCD image sensor in the direction of averaging, and the CCD
An image reading apparatus, comprising: variable diaphragm means for continuously changing the amount of light incident on an image sensor. 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 an optical device provided in a region from the light source to the CCD image sensor as the spectral correction means. 4. The image reading apparatus according to claim 1, wherein the variable diaphragm means is incorporated in a lens barrel of a lens forming the image forming optical system.