JPH053545A - Photoelectric conversion device - Google Patents

Abstract

(57) [Abstract] [Purpose] It is possible to cope with multi-gradation and high quality by correcting the error of the reproduction density caused by the sensitivity characteristic of the reading sensor. A photoelectric conversion device comprising: a light source for irradiating an object to be read with light; and a reading sensor arranged in a row and receiving image information light reflected from the object to be read are different from each other. Means for generating respective correction signals corresponding to a plurality of reflectances of the object to be read, means for storing the correction signals generated by the correction signal generation means, and correction means stored in the storage means And means for correcting the reproduction density of the image information read by the reading sensor based on the signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoelectric conversion device for irradiating an object to be read with light and reading the scattered light with a reading sensor.

[0002]

2. Description of the Related Art Recently, with the spread of so-called electronic office machines such as facsimiles and image readers, the demand for compact and low-cost image input devices has increased. Therefore, there is a demand for a contact image sensor having high reading resolution, capable of reading at high speed, and having good gradation characteristics. As such a contact type image sensor, a sensor using a reading sensor made of a semiconductor layer such as amorphous silicon is generally used. FIG. 16 is a schematic sectional view of the conventional contact image sensor, and FIG. 17 is a schematic circuit diagram of the contact image sensor. As shown in FIG. 16, the sensor substrate 1 is composed of a transparent substrate 2 serving as a transparent substrate, a light-shielding layer 3, and a transparent protective layer 4, and a reading sensor 5 is formed on the light-shielding layer 3. The light emitted from the light source 6 passes through the window 14 and is incident on the original 8 that is brought into close contact with the transparent protective layer 4 by the roller 7, and a part of the original surface scattered light 9 that changes depending on the image information is read as image information. It is incident on the sensor 5. A plurality of the reading sensors 5 are arranged in the form of an array.
In FIG. 7, S _{1 to} S _n are shown. The n value, which is the number of sensors, is usually about 1728 bits for the A4 version and about 2048 bits for the B4 version with a resolution of 8 pel / mm. A voltage is applied to the reading sensors S _{1 to} S _n by the sensor bias power supply 15, light incident on the reading sensors S _{1 to} S _n is converted into a current, and the reading sensor output processing circuit 11, Amplifier circuit 12, A / D converter 13
Are sequentially output as digital signals. Further, the sensitivity of the reading sensor with respect to the document density and the light amount of the light source for illuminating the document usually have some variations between bits. Therefore, some conventional photoelectric conversion devices are provided with a bit correction circuit for correcting the variation. FIG. 18 is a schematic circuit diagram of a contact image sensor having the conventional bit correction circuit. Bit This bit correction circuit, comprising previously by read plain white so-called white reference document 10 the reading sensor S ₁ to S _n of the light amount variation of the information reading sensitivity variation and the document illumination light source of the sensor The output is stored in the memory 16 as a correction signal.
Next, the read signal at the time of reading the original is calculated by the divider 17
By dividing by the correction signal stored in the memory 16, a standardized and corrected output signal can be obtained.

[0003]

However, in general, the reading sensor has a non-linear sensitivity characteristic with respect to the document density, as shown by A in FIG. Therefore, in the conventional photoelectric conversion device using only the white reference original, the relationship between the original density and the corrected read output is linear as shown by B in FIG. In this case, the output of the reading sensor for the document density T ₁ in FIG. 19 is S. Therefore, as shown in FIG. 20, the density of the document reproduced from this is T ₂ , which is significantly different from the density T ₁ of the read document. After such correction, when the read signal is used as an input image signal of a facsimile, for example, the non-linearity of the sensitivity of the reading sensor with respect to the document density causes an error (T) as shown in FIG. ₂ -T ₁₎ appears as. Therefore, particularly when halftone display such as the dither method or the error diffusion method is performed, the reproducibility of halftone images is significantly reduced, which hinders multi-gradation and high quality of images.

The present invention has been made in order to solve such a problem, and its purpose is to effectively correct the error of the reproduction density due to the sensitivity characteristic of the reading sensor, to increase the number of gradations and to increase the gradation. It is an object of the present invention to provide a photoelectric conversion device capable of sufficiently dealing with quality.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a light source for irradiating an object to be read with light, and a plurality of light sources arranged in a line for receiving image information light reflected from the object to be read. In a photoelectric conversion device including a reading sensor, means for generating correction signals corresponding to a plurality of reflectances of different read objects, and correction signals generated by the correction signal generation means And a means for correcting the reproduction density of the image information read by the reading sensor based on the correction signal stored in the storage means. To be achieved.

[0006]

Embodiments of the present invention will now be described in detail with reference to the drawings. [First Embodiment] FIG. 1 is a block diagram showing an embodiment of the photoelectric conversion device of the present invention, and FIG. 2 is a block diagram showing the electric circuit configuration thereof. 1 and 2, the same parts as those of the conventional device are designated by the same reference numerals, and the description thereof will be omitted in this embodiment. In the figure, 18 is a flat plate-shaped white member whose surface is coated with white so that the reflectance is 100%, and 19 is a flat plate-shaped gray member fixed to the white member 18.
The reflectance of the gray member 19 is based on the white standard (reflectance 100%).
And the black reference (reflectance 0%). Reference numeral 20 denotes an arm-shaped holding member provided with an elongated hole 20b, which has a structure capable of rotating about a rotating shaft 20a at the upper end. Further, the pin 19a provided at the end of the gray member 19 is inserted into the elongated hole 20b, and the holding member 20 rotates about the rotation shaft 20a, so that the white member 18 and the gray member 19 are transparent and protected. 4 is configured to move in the left-right direction in the drawing. Reference numerals 21 and 22 denote storage circuits for storing the correction signals. The storage circuit 21 stores the correction signal obtained by reflection on the white member 18, and the storage circuit 22 stores the correction signal obtained by reflection on the gray member 19. From the function, the storage circuit 21 will be referred to as a white memory, and the storage circuit 22 will be referred to as a gray memory. Further, 23 is an arithmetic processing circuit for processing a read signal from the original document and a correction signal of each memory to correct the reproduction density of the original document, and 33 to 35 are switches. The correction process of the arithmetic processing circuit 23 will be described later in detail.

Next, the operation of this embodiment will be described. First,
The holding member 2 is controlled by a control signal from a control circuit (not shown).
0 is driven to rotate by a predetermined angle, and the white member 18 is set so as to be located on the lower surface of the roller 7 as shown in FIG. On the other hand, the switch 34 shown in FIG. 2 is controlled to be on, and the other switches 33 and 35 are controlled to be off. In this state, the light from the light source 6 passes through the transparent substrate 2, the window 14, and the transparent protective layer 4, and is irradiated onto the white member 18. White member 18
The light 31 scattered by is incident on the reading sensor 5 through the transparent protective layer 4. The scattered light 31 is used as the first correction information light, and photoelectrically converted light is used as the first correction signal. The correction information light incident on each of the reading sensors S _{1 to} S _n is converted into a current by each sensor and then sequentially output by the reading sensor output processing circuit 11. At this time, the first correction signal, which is the read information of the white member 18, is the switch 34.
Is closed, it is stored as correction information in the white memory 21.

When the storage of the first correction signal is completed, the holding member 20 is driven to further rotate, and the gray member 19 is set so as to be located on the lower surface of the roller 7 as shown in FIG. At the same time, the switch 35 shown in FIG. 2 is controlled to be turned on, and the other switches 33 and 34 are controlled to be turned off. In this state, light is emitted from the light source 6 in exactly the same manner as described above, and the scattered light 32 scattered by the gray member 19 enters the reading sensor 5. The scattered light 32 is used as second correction information light, and photoelectrically converted light is used as a second correction signal. The correction information light 32 incident on each of the reading sensors S _{1 to} S _n is converted into a current and then sequentially output by the reading sensor output processing circuit 11. Since the switch 35 is closed, the second correction signal thus obtained is
It is stored in the gray memory 22 as correction information. First of all
And, the operation of storing the second correction signal in the memory is completed.

When the storage of the correction signal is completed, the next step is to read the original. When reading a document, the holding member 20 is driven as shown in FIG. 5, and the white member 18 and the gray member 19 are returned to their original positions again. As a result, the white member 18
Then, the gray member 19 is moved away from the lower surface of the roller 7, and the document reading standby state is set. At the same time, the switch 33 shown in FIG. 2 is controlled to be turned on and the other switches 34 and 35 are turned off. In this state, as shown in FIG. 5, the original 8 is conveyed on the transparent protective layer 4 at a constant speed by the original feeding operation of the roller 8. On the other hand, light is continuously emitted from the light source 6 toward the document 8 and scattered on the document surface at a reflectance according to image information. The original surface scattered light 9 is sequentially incident on the reading sensor 5 as image information, converted into a current by each of the reading sensors S _{1 to} S _n , and then sequentially read by the reading sensor output processing circuit 11. It is output for each line. At this time, since the switch 33 is turned on, the read signal is sent to the arithmetic processing circuit 23, and the correction process of the original read signal is executed using the first and second correction signals. The correction process will be described below.

First, the reading signal of the original is the arithmetic processing circuit 2.
When input to 3, the correction information corresponding to the reading sensors S _{1 to} S _n is called from the white memory 21 and the gray memory 22 and sent to the arithmetic processing circuit 23. Here, the output (sensitivity) characteristic of the reading sensor with respect to the document density is generally shown in FIG.
It is non-linear as shown in. In FIG. 6, G indicates the reflectance of the gray member 19, and the sensor output corresponding to this is H.
Is. The reflectance of the white member 18 is 100%, and the sensor output at this time is 100%. Arithmetic processing circuit 2
3, the reproduction density is determined by the linear approximation method with respect to the sensor output based on the first and second correction signals obtained by using the two reflecting members having different reflectances as described above. to correct. That is, the arithmetic processing circuit 23 approximates the output of the image information by the straight line B connecting the point G and the 100% point, and sends this to the image forming unit (not shown) as the output after the correction of the reproduction density.
As a result, when a document having a density of T ₁ is read as shown in FIG. 7, the density reproduced by the corrected output is T ₃ , and the error is T ₃ −T ₁ . Thus, in this embodiment it is possible to sufficiently reduce the error compared to the conventional error T ₂ -T ₁ described in FIG 20. In addition, gray member 1
The error can be further reduced by bringing the reflectance of 9 close to the reflectance T ₁ of the image information of the document. In addition, it is generally known that in a reading sensor using amorphous silicon, the sensor output is proportional to the γth power of the incident light amount, but as shown in FIG. 6, the sensor output is proportional to the γth power of the incident light amount. If it is known in advance that γ can be determined from the output when the white member 18 and the gray member 19 are read. Therefore, in this case, the calculation processing shown in FIG.
As shown in, it is possible to correct the density of the read document with almost no error. [Second Embodiment] FIG. 9 is a block diagram showing a second embodiment of the present invention. In this embodiment, the white member 18 and the gray member 1
Instead of 9, one reference diffusion member 25 is provided. The reference diffusion member 25 is manufactured so that the reflectance thereof is uniform on any surface. Further, the reference diffusion member 25 is driven by the holding member 20 in the same manner as in the above-described embodiment,
It is configured so as to be movable in the left-right direction on the transparent protective layer 4. On the other hand, the light source 6 is composed of a large number of light emitting elements (light emitting diodes) LEDs arranged along the arrangement direction of the reading sensor as shown in FIG. 10. In this embodiment, the power source voltage of the light emitting elements is changed. It can be switched to two stages. That is, by switching the switch 24 to a or b, the power supply voltage can be varied and the light amount of the light emitting element can be adjusted.

Next is the operation. First, when reading the correction signal, the holding member 20 is driven to position the reference diffusion member 25 on the lower surface of the roller 7. Further, the switch 24 shown in FIG. 10 is connected to the side a, the switch 34 is turned on, and the switches 33 and 35 are turned off. As a result, the light source 6 is turned on at the maximum voltage, and the correction information obtained from the reflected light of the reference diffusion member 25 is stored in the white memory 21 as the first correction signal. Next, with the reference diffusion member 25 as it is,
The switch 24 is connected to the b side, the switch 35 is turned on, and the switches 33 and 34 are turned off. As a result, the light amount of the light source 6 decreases, and the correction information obtained from the reflected light of the reference diffusion member 25 at this time is stored in the gray memory 22 as a second correction signal. That is, in the first embodiment, the correction signal is obtained by using the reflecting members having different reflectances, but in the present embodiment, the reflectance of the reflecting member is constant and the correction signal corresponding to the reflectance is obtained by changing the light amount of the light source. Is to get. When reading a document, the reference diffusion member 25 is moved away from the lower surface of the roller, the switch 24 is again connected to the side a, the switch 33 is turned on, and the switches 34 and 35 are turned off. The read image information is sent to the arithmetic processing circuit 23 and subjected to correction processing. The correction process is exactly the same as in the first embodiment. [Third Embodiment] FIG. 11 is a block diagram showing a third embodiment of the present invention. This embodiment corresponds to the light source 6 shown in the second embodiment.
It is an example in which the dimming effect of (1) is performed using a dimming member. That is, this is an example in which the thin plate-shaped light reducing member 26 having a predetermined light transmittance is disposed above the light source 6, and the light amount of the light source 6 is changed by the light reducing action of the light reducing member 26. The pin-shaped end portion 26a of the light-reducing member 26 is provided in the elongated hole 2 of the arm-shaped holding member 27.
The light-attenuating member 26 can be moved in the left-right direction by being inserted through 7a and rotating the holding member 27 about the rotating shaft 27b. Therefore, when the dimming member 26 is located above the light source 6, the dimming action of the dimming member 26 can reduce the amount of light reaching the upper side.
The other structure is the same as that of the second embodiment.

In the present embodiment, first, as shown in FIG. 12, the reference diffusion member 25 is positioned on the lower surface of the roller 7, the light source 6 is turned on in this state, and the obtained correction information is stored in the white memory 21. Next, as shown in FIG. 13, the reference diffusion member 2
In the state 5 as it is, the dimming member 26 is positioned on the optical path of the light source 6. As a result, the light of the light source 6 is reduced by the light reducing member 26.
The correction information obtained from the reflected light is reduced by a predetermined amount by the dimming action of the light and is incident on the reference diffusing member 25.
Store in 2. The correction information at this time is exactly the same as the correction information obtained by dimming the light from the light source in the second embodiment. When reading a document, the reference diffusion member 25 and the dimming member 26 are returned to their original positions again as shown in FIG. The read image information is sent to the arithmetic processing circuit 23, and the same correction processing as in the first embodiment is performed. [Fourth Embodiment] FIG. 14 is a block diagram showing a fourth embodiment of the present invention. This embodiment is an example in which an arithmetic processing circuit is configured in an analog manner using a ladder resistor 28, a comparator 29, and a decoder 30. Even in this example,
When the sensitivity characteristic of the reading sensor with respect to the document density is non-linear as shown in FIG. 6, the read document density can be effectively corrected as shown in FIG. [Fifth Embodiment] FIG. 15 is a block diagram showing a fifth embodiment of the present invention. In this embodiment, in addition to the above two correction signals, the correction signal at the time of reading the black reference, that is, the reflectance is 0%.
In this example, the correction process is performed using the correction signal when The black reference correction signal is stored in the black memory 37.
In this embodiment, since the offset output at the time of reading the black reference can be corrected by performing the arithmetic processing using the correction signal of the black reference, the error can be further reduced as compared with the above embodiments.

[0013]

As described above, according to the present invention, it is possible to effectively correct the non-linearity of the sensitivity of the reading sensor with respect to the document density, and to reproduce the image more faithfully. Therefore, even in the case of reproducing an image with multiple gradations, it is possible to reproduce an image with high quality without lowering the reproducibility of halftone as in the conventional case.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a photoelectric conversion device of the present invention.

FIG. 2 is a block diagram showing an electrical circuit configuration of the embodiment of FIG.

FIG. 3 is a configuration diagram showing a state when a first correction signal is generated using a white member.

FIG. 4 is a configuration diagram showing a state when a second correction signal is generated using a gray member.

FIG. 5 is a configuration diagram showing a state at the time of reading a document.

FIG. 6 is an output (sensitivity) with respect to the document density of the reading sensor.
It is a characteristic view showing a characteristic.

FIG. 7 is a diagram showing a document density after correction with respect to a sensor output of an arithmetic processing circuit.

FIG. 8 shows the correction characteristics of the arithmetic processing circuit obtained by determining γ from the first and second correction signals when it is known in advance that the sensor output is proportional to the γ-th power of the incident light amount. It is a figure.

FIG. 9 is a configuration diagram showing a second embodiment of the present invention.

10 is a block diagram showing an electrical circuit configuration of the embodiment of FIG.

FIG. 11 is a configuration diagram showing a third embodiment of the present invention.

12 is a configuration diagram showing a state when a correction signal is generated using the reference diffusion member in the embodiment of FIG. 11. FIG.

FIG. 13 is a configuration diagram showing a state when a correction signal is generated in a state where the light of the light source is reduced by the light reducing member in the embodiment of FIG.

FIG. 14 is a block diagram showing a fourth embodiment of the present invention.

FIG. 15 is a block diagram showing a fifth embodiment of the present invention.

FIG. 16 is a configuration diagram showing a conventional photoelectric conversion device.

FIG. 17 is a block diagram showing an electrical circuit configuration of the conventional device.

FIG. 18 is a block diagram showing a conventional photoelectric conversion device provided with a bit correction circuit.

FIG. 19 is a diagram showing a non-linear sensitivity characteristic of a reading sensor with respect to a document density.

20 is a diagram showing correction characteristics of the bit correction circuit of FIG.

[Explanation of symbols]

1 sensor board 2 transparent substrate 3 Light-shielding layer 5 Reading sensor 6 light source 7 Laura 8 manuscript 11 Reading sensor output processing circuit 18 White member 19 Gray member 21 white memory 22 Ash memory 25 Standard diffusion member 26 Dimming member

Claims (8)

[Claims] 1. A photoelectric conversion device comprising a light source for irradiating an object to be read with light, and a reading sensor arranged in a plurality of rows and receiving image information light reflected from the object to be read, Means for generating respective correction signals corresponding to a plurality of reflectances of different read objects, means for storing the correction signals generated by the correction signal generation means, and storage means And a means for correcting the reproduction density of the image information read by the reading sensor on the basis of the correction signal. 2. The correction signal generating means corresponds to a plurality of reflectances by irradiating a plurality of reflecting members each having a different reflectance with light from a light source and reading the reflected light with a reading sensor. The photoelectric conversion device according to claim 1, wherein the correction signal is generated. 3. The correction signal generating means includes a reflecting member having a predetermined reflectance and a light adjusting means for varying the light amount of the light source in a plurality of steps, and each light amount of the light source reflected by the reflecting member. The photoelectric conversion device according to claim 1, wherein a correction signal corresponding to a plurality of reflectances is generated by reading each of the reflected lights at 1 and 2 by a reading sensor. 4. The correction signal generating means includes a reflecting member having a predetermined reflectance and a dimming member for dimming the light amount of the light source, and the dimming member switches the light amount of the light source in a plurality of steps. The photoelectric conversion device according to claim 1, wherein a correction signal corresponding to a plurality of reflectances is generated by reading the reflected light of each light amount reflected by the reflecting member with a reading sensor. 5. The photoelectric conversion device according to claim 1, wherein the plurality of reflectances are reflectances other than the black reference, wherein the reflectances are substantially 0%. 6. The correction means corrects the reproduction density of the read object by linearly approximating the nonlinearity of the sensitivity characteristic of the reading sensor based on the correction signals corresponding to the plurality of reflectances. The photoelectric conversion device according to claim 1. 7. The correction means calculates γ from the correction signal when the output of the reading sensor is proportional to the γth power of the incident light amount, and reproduces the read object based on the obtained γ. The photoelectric conversion device according to claim 1, wherein the density is corrected. 8. A correction signal corresponding to a black reference having a reflectance of approximately 0% is generated, and the offset amount of the reading sensor during black reference reading is corrected based on the correction signal. The photoelectric conversion device according to claim 1.