JP2003274114A - Image reader - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image reader which obtains an image of high quality by adjusting the supply energy to a light source to stabilize the output level of an image signal. <P>SOLUTION: In the image reader 1, a light source driving circuit 3 is controlled by a control part 2, and a light source 7 of an image sensor 6 is driven by the light source driving circuit 3, and light from the light source 7 is radiated to a document, and a sensor driving circuit 5 is controlled by the control part 2 to drive a sensor 8 of the image sensor 6, and the reflected light from the document is photoelectrically converted by the sensor 8, thus reading an image of the document. The control part 2 adjusts the supply energy to the light source 7 through the light source driving circuit 3 to perform light quantity adjustment processing for controlling the peak value of an image signal from the sensor 8 to a fixed value. Consequently, the level of the image signal is stabilized without an influence of individual differences or environmental change of the image sensor 6, and the image quality of the read image is kept high and fixed. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus, and more particularly, to adjusting the energy supplied to a light source to keep the output level of an image signal constant and to be influenced by the individual sensors and environmental changes. The present invention relates to an image reading device capable of keeping the image quality of a read image constant.

[0002]

2. Description of the Related Art In general, an image reading apparatus uses an LED (Ligh Light).
A light emitting element array such as a t Emitting Diode array is used as a light source, and the original is irradiated with light from the light source, and reflected light from the original is incident on a photoelectric conversion element such as a CCD (Charge Coupled Device) to generate a photoelectric conversion element. The image of the original is read by converting it into an electric signal.

In the image reading apparatus, it is important that the light amount of the LED used as the light source is appropriate in order to read the image of the original in good condition.

However, in a contact image sensor using such an LED light source, when the light source is driven at a constant voltage, the supplied energy varies and the image sensor also varies in sensitivity, so the level of the photoelectrically converted image signal is increased. Variation, it becomes difficult to keep the image quality constant, and it is affected by the usage environment, especially the temperature.

Therefore, conventionally, in the image reading in which an original image is photoelectrically read by an image sensor and the output signal of the image sensor is converted into a digital signal, the amount of incident light to the image sensor is adjusted by adjusting the transmittance in the optical path, An image in which at least one of reading condition control in an image sensor and intensity adjustment of an output signal from the image sensor is used, and the maximum value of the signal when converted into a digital signal is constant regardless of the original image. A reading method has been proposed (see Japanese Patent Laid-Open No. 11-308415).

That is, according to this prior art, at least one of the amount of light incident on the image sensor, the control of the reading condition in the image sensor, and the intensity adjustment of the output signal from the image sensor is performed.
In order to improve the image quality, the maximum value of the image signal when converted into a digital signal is made constant regardless of the original image.

[0007]

However, since at least one of the amount of light incident on the image sensor, the reading condition control in the image sensor, and the intensity adjustment of the output signal from the image sensor is performed, the cost becomes high, In particular,
In the image reading apparatus using the contact image sensor using the LED light source, it is required to improve the image quality at low cost. Further, although the LED array generates a light amount that is substantially proportional to the supplied energy, the shape of the light amount distribution is not always constant, and the above-mentioned conventional technique can appropriately solve such a problem. However, it was necessary to make improvements in order to improve the image quality.

Therefore, in the invention according to claim 1, the light source drive circuit is controlled by the control means, the light source of the image sensor is driven by the light source drive circuit, and the light from the light source is applied to the original for control. When the sensor of the image sensor is driven by controlling the sensor driving circuit and the reflected light from the original is photoelectrically converted by the sensor to read the image of the original, the control means sets the peak of the image signal output by the sensor. Depending on the value, the energy supplied to the light source is adjusted via the light source drive circuit, and the light amount adjustment processing is performed to control the peak value of the image signal from the sensor to a constant value, thereby making the difference between the individual image sensors. It is an object of the present invention to provide an image reading device that can keep the image signal level constant and keep the image quality of a read image high in quality and constant without being affected by changes in the environment.

According to a second aspect of the present invention, the control means drives the light source with the supply energy set through the light source drive circuit, and the peak value of the image signal output from the sensor when the light source is driven with the set supply energy. Is detected and the light amount adjustment processing is performed based on the peak value, thereby absorbing the error in the peak value due to the change in the light amount distribution caused by changing the energy supplied to the light source, and further improving the image quality of the read image. It is an object of the present invention to provide an image reading device which can maintain high quality and more constant.

That is, although a light source such as an LED generates a light quantity that is substantially proportional to the supplied energy in a predetermined operating range, the shape of the light quantity distribution is not always constant and the desired light quantity may not be obtained.

However, as in the invention of this claim, the peak value of the sensor output of the light source of the energy supplied after the adjustment is detected, and the supplied energy is finely adjusted again to set the expected light amount. Therefore, the image quality can be further improved.

According to a third aspect of the present invention, the control means calculates the energy supplied to the light source as a ratio to the reading time for one line, and performs the light amount adjustment process to adjust the energy supplied by the lighting duty. It is an object of the present invention to provide an image reading device that can make an adjustment circuit simple and easy, can inexpensively and stably maintain the image quality of a read image at high quality and constant.

According to a fourth aspect of the present invention, the control means integrates various controls by detecting the presence or absence of abnormality of the image sensor during the light amount adjustment processing period, so that the read image of the read image can be stably obtained at low cost. It is an object of the present invention to provide an image reading device capable of keeping the image quality high and constant.

[0014]

According to another aspect of the present invention, there is provided an image reading apparatus, wherein a control means controls a light source driving circuit to drive the light source of an image sensor by the light source driving circuit. Image reading that irradiates the original with light, drives the sensor of the image sensor by controlling the sensor drive circuit with the control unit, photoelectrically converts the reflected light from the original with the sensor, and reads the image of the original In the device, the control means adjusts the energy supplied to the light source via the light source drive circuit according to the peak value of the image signal output from the sensor, and the peak of the image signal from the sensor. The above object is achieved by performing the light amount adjustment processing for controlling the value to a constant value.

According to the above arrangement, the light source drive circuit is controlled by the control means, the light source of the image sensor is driven by the light source drive circuit, the light from the light source is applied to the document, and the sensor drive is performed by the control means. When the sensor of the image sensor is driven by controlling the circuit and the reflected light from the original is photoelectrically converted by the sensor to read the image of the original, the control means responds to the peak value of the image signal output from the sensor. By adjusting the energy supplied to the light source via the light source drive circuit and performing the light amount adjustment process that controls the peak value of the image signal from the sensor to a constant value, it affects the differences between image sensors and changes in the environment. The level of the image signal can be made constant without being affected, and the image quality of the read image can be kept high and constant.

In this case, for example, as described in claim 2, the control means drives the light source with the set supply energy via the light source drive circuit, and controls the light source with the set supply energy. The peak value of the image signal output by the sensor may be detected during driving, and the light amount adjustment process may be performed based on the peak value.

According to the above construction, the control means drives the light source with the supply energy set through the light source drive circuit, and detects the peak value of the image signal output from the sensor when the light source is driven with the set supply energy. However, since the light amount adjustment processing is performed based on the peak value, it is possible to absorb the error in the peak value due to the change in the light amount distribution due to the change in the energy supplied to the light source, and to further improve the image quality of the read image. It can be kept high quality and even more consistent.

Further, for example, as described in claim 3, the control means calculates the energy supplied to the light source as a ratio to the reading time of one line and performs the light amount adjustment processing. Good.

According to the above construction, the control means calculates the energy supplied to the light source as a ratio to the reading time of one line and performs the light amount adjustment processing. Therefore, the energy supplied is adjusted by the lighting duty to adjust the adjustment circuit. The image quality of the read image can be kept high and constant, inexpensively and stably.

Further, for example, as described in claim 4, the control means may detect whether or not there is an abnormality in the image sensor during the light amount adjustment processing period.

According to the above arrangement, the control means detects whether or not there is an abnormality in the image sensor during the light amount adjustment processing period, so that various controls can be integrated, and the read image can be stably obtained at low cost. The image quality can be kept high and constant.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

Since the embodiments described below are preferable specific examples of the present invention, various technically preferable limitations are given, but the scope of the present invention is particularly limited in the following description. The present invention is not limited to these embodiments unless there is a statement to limit the invention.

1 to 4 are views showing an embodiment of the image reading apparatus of the present invention, and FIG. 1 shows an image reading apparatus 1 to which the embodiment of the image reading apparatus of the present invention is applied. It is a block diagram of an essential part.

In FIG. 1, the image reading apparatus 1 includes a control unit 2, a light source drive circuit 3, an AD converter 4, a sensor drive circuit 5, an image sensor 6 and the like.

The image sensor 6 includes a light source 7, a sensor 8 and an optical system (not shown). The light source 7 uses an LED array or the like and irradiates the image surface of the document with light.

The light source 7 is turned on by the light source drive circuit 3, and the light source drive circuit 3 is drive-controlled by the control unit 2.

As the sensor 8, a CCD or the like is used, and the reflected light emitted from the light source 7 and reflected by the image surface of the original is incident on the sensor 8 through an optical system (not shown). When the sensor 8 is driven by the sensor drive circuit 5, the sensor 8 photoelectrically converts incident light and outputs an analog electric signal to the AD converter 4.

The AD converter 4 receives the reference voltage Vref for designating the operating range from the control unit 2, compares the analog electric signal (image signal) input from the sensor 8 with the reference voltage Vref, and converts it into a digital signal. , And outputs a digital image signal to the control unit 2.

The sensor drive circuit 5 drives the sensor 8 under the control of the controller 2.

The control unit (control means) 2 controls the drive of the light source drive circuit 3 and the sensor drive circuit 5, and at the same time AD
The reference voltage Vref of the converter 4 is set to control the operation of the image reading device 1. The control unit 2 sets the reference voltage Vref at a predetermined voltage interval.

The control unit 2 detects the peak value of the image signal digitized by the AD converter 4, and when detecting the peak value, a white reference plate (not shown) provided facing the image sensor 6 is provided. Is read by the sensor 8. Further, the control unit 2 determines the reference voltage Vref by the peak value of the analog electric signal (image signal) read by the image sensor 6 and input from the sensor 8 to the AD converter 4 before the actual image reading operation. A light amount adjustment process is executed to control the lighting period of the light source 7 so that the peak value of the analog electric signal becomes constant.

Next, the operation of this embodiment will be described. In the image reading apparatus 1 of the present embodiment, the control unit 2 adjusts the supply energy supplied to the light source 7 according to the peak value of the image signal obtained from the sensor 8 of the image sensor 6, and the sensor 8 concerned. The light source drive circuit 3 is controlled so that the peak value of the image signal from is a constant value.

That is, the control unit 2 to the AD converter 4
Of the reference voltage Vref output to the image sensor 6 and the analog image signal from the sensor 8 of the image sensor 6 digitally converted by the reference voltage Vref.
Have a relationship as shown in FIG.

In FIG. 2, the reference voltage Vref
Specifies the operating range of the AD converter 4, and Vfr is A
The maximum voltage Vtg of the reference voltage Vref at which the D converter 4 can operate is the reference voltage Vref at which the target value of the peak value of the output of the sensor 8 (sensor output) is 90%.
Is. That is, 90% of Vtg is the target value to be set as the peak value.

In the image reading apparatus 1, when the light source 7 is turned on and the sensor 8 is driven, the image signal photoelectrically converted from the sensor 8 is input to the AD converter 4, and the analog image signal is
The digital value is converted by the D converter 4 to obtain the peak value Vp1.

The control unit 2 controls the obtained peak value Vp1.
Is 90% of Vtg of the reference voltage Vref (Vtg × 9
If it is lower than 0%), the reading operation is performed under the same lighting condition as shown in FIG. Further, when the control value is 90% or more of the maximum value Vfr of the reference voltage Vref, the control unit 2 may exceed the operating range of the AD converter 4, so the light amount is determined to be excessive and the image sensor 6 is determined to be abnormal. . Then, the control unit 2 sets the peak value Vp1 to 90% (Vfr * 9) of the maximum value Vfr of the reference voltage Vref.
When it is between 0%) and 90% of Vtg (Vtg * 90%), the light amount adjustment described below is performed.

Then, the control unit 2 adjusts the light quantity of the light source 7 of the image sensor 6 as shown in FIG.

That is, the control unit 2 sets the ratio of the lighting time to the reading time of one line (lighting duty) according to the ratio between the peak value Vp1 and Vtg * 85% obtained previously. The lighting duty obtained here is Duty1
And turn on the light source 7 with the lighting duty Duty1,
The peak value is read again, and this peak value is set to Vp2.

In FIG. 3A, the peak value Vp2 is Vtg * 85.
%, The reading operation is performed under the lighting condition of the lighting duty Duty1.

Further, in FIG. 3B, the peak value Vp2 is Vtg.
* 85% or more is shown, and the reference voltage Vref at this time is set to Vref2. Where Vref2
Is a value that can be set to a value higher than the value obtained by dividing Vp2 by 90%.

Further, FIG. 3C shows the lighting duty D.
It is an explanatory view of setting of uty3. That is, Vp2 and Vtg
* The lighting duty is calculated from the 85% ratio, and this ratio is used as the lighting duty Duty2.
The light source 7 is turned on at y2, the peak value is read again, and this peak value is set to Vp3. In FIG. 3 (c), the peak value Vp3 is shown at a position lower than Vtg * 85%, but this is not always the case, and Vtg *
It may be higher than 85%.

However, the reference voltage Vref is V
Since it remains ref2, it does not exceed the operating range of the AD converter 4.

Then, the control unit 2 performs the above-mentioned light amount adjustment with reference to FIG.
As shown in. That is, the control unit 2 sets the reference voltage Vref of the AD converter 4 to the maximum value Vfr and the lighting duty Duty to 100% (step S101).

Next, the control unit 2 drives the sensor 8 via the sensor drive circuit 5 to turn on the light source 7, and the photoelectric conversion output (analog image signal) from the sensor 8 is digitalized by the AD converter 4. Then, the peak value Vp1 is read (step S102).

The control unit 2 sets the acquired peak value Vp1 to Vtg.
It is checked whether the value divided by is 90% or less of the maximum value Vfr of the reference voltage Vref (Vp1 / Vtg)> 90%) (step S103). If 90% or less, the peak value Vp1 is 90% of Vtg. Since it is the following, the reference voltage Vref is set to Vtg, and the light amount adjustment processing ends (step S104).

In step S103, the acquired peak value V
When the value obtained by dividing p1 by Vtg is 90% or more of the maximum value Vfr of the reference voltage Vref, the control unit 2 divides the peak value Vp1 by the maximum value Vfr, and this peak value Vp1 is the maximum value Vfr. The divided value is 90% or more (Vp1 / Vfr)> 90%)
It is checked whether or not (step S105).

If the value obtained by dividing the peak value Vp1 by the maximum value Vfr is 90% or more in step S105, the control unit 2
Determines that the light amount has exceeded, and determines that the image sensor 6 is abnormal (step S106).

In step S105, if the value obtained by dividing the peak value Vp1 by the maximum value Vfr is 90% or less, the control unit 2
Is a lighting duty Duty1 (Duty = (Vtg × Vtg * 85% obtained by dividing Vtg * 85% by the peak value Vp1.
85%) / Vp1) as the lighting duty (step S1
07), the light source 7 is turned on with the lighting duty Duty, and the peak value Vp2 is read (step S108).

Next, the control unit 2 sets the peak value Vp2 to 90%.
The value Vref2, which is close to and is higher than the value divided by, is set as the reference voltage of the AD converter 4 (step S1).
09), and it is checked whether the set reference voltage Vref2 has become Vtg (step S110).

In step S110, the reference voltage V
When ref2 becomes Vtg, the control unit 2 ends the light amount adjustment.

In step S110, the reference voltage V
When ref2 is not Vtg, the control unit 2 determines the lighting duty Dut from the ratio of the peak value Vp2 and Vtg * 85%.
y2 is calculated (Duty2 = (Duty1 × (Vtg × 85
% / Vref2) × 3FFh) / Vp2), and the light amount adjustment processing is ended (step S111).

As described above, in the image reading apparatus 1 according to the present embodiment, the control unit 2 controls the light source drive circuit 3 so that the light source drive circuit 3 drives the light source 7 of the image sensor 6 to drive the light source 7.
The document is irradiated with light from the sensor, and the control unit 2 causes the sensor drive circuit 5 to illuminate.
When the sensor 8 of the image sensor 6 is driven to photoelectrically convert the reflected light from the document by the sensor 8 to read the image of the document, the control unit 2 causes the peak of the image signal output from the sensor 8. According to the value, the energy supplied to the light source 7 is adjusted via the light source drive circuit 3 to perform a light amount adjustment process for controlling the peak value of the image signal from the sensor 8 to a constant value.

Therefore, the level of the image signal can be made constant without being affected by the difference between the image sensors 6 and the environmental change, and the image quality of the read image can be kept high and constant. it can.

Further, the image reading apparatus 1 of the present embodiment is
The control unit 2 drives the light source 7 with the supply energy set through the light source drive circuit 3, detects the peak value of the image signal output from the sensor 8 when the light source 7 is driven with the set supply energy, and detects the peak. The light amount adjustment process is performed based on the value.

Therefore, it is possible to absorb the error of the peak value due to the variation of the light amount distribution due to the change of the energy supplied to the light source 7, and to maintain the image quality of the read image at a higher quality and more constant. You can

Further, the image reading apparatus 1 of the present embodiment
In the above, the control unit 2 calculates the energy supplied to the light source 7 as a ratio to the reading time of one line, and performs the light amount adjustment processing.

Therefore, the supply energy can be adjusted by the lighting duty to make the adjusting circuit simple and easy, and the image quality of the read image can be kept high and constant at low cost and stably. it can.

Further, the image reading apparatus 1 of the present embodiment is
The control unit 2 controls the image sensor 6 during the light amount adjustment processing period.
The presence or absence of abnormality is detected.

Therefore, various controls can be integrated, and the image quality of the read image can be kept high and constant at low cost and stably.

Although the invention made by the present inventor has been specifically described based on the preferred embodiments, the present invention is not limited to the above embodiments, and various modifications are possible without departing from the scope of the invention. It goes without saying that it can be changed.

[0062]

According to the image reading apparatus of the present invention, the light source drive circuit is controlled by the control means, the light source of the image sensor is driven by the light source drive circuit, and the light from the light source is emitted. When the document is irradiated and the sensor driving circuit is controlled by the control unit to drive the sensor of the image sensor, and the reflected light from the document is photoelectrically converted by the sensor to read the image of the document, the control unit controls the sensor Depending on the peak value of the output image signal, the energy supplied to the light source is adjusted via the light source drive circuit, and the light amount adjustment process is performed to control the peak value of the image signal from the sensor to a constant value. The level of the image signal can be made constant without being affected by the difference between the sensors and the environmental change, and the image quality of the read image can be kept high and constant.

According to the image reading apparatus of the second aspect of the present invention, the control means drives the light source with the supply energy set through the light source drive circuit, and outputs the sensor when the light source is driven with the set supply energy. The peak value of the image signal to be detected is detected, and the light amount adjustment process is performed based on the peak value. Therefore, it is possible to absorb the error in the peak value due to the change in the light amount distribution due to the change in the energy supplied to the light source, The image quality of the read image can be maintained at a higher quality and more constant.

According to the image reading apparatus of the third aspect of the present invention, the control means calculates the energy supplied to the light source as a ratio to the reading time of one line and performs the light amount adjustment processing, so that the light is supplied at the lighting duty. The energy can be adjusted to make the adjustment circuit simple and easy, and the image quality of the read image can be kept high and constant at low cost and stably.

According to the image reading apparatus of the fourth aspect of the present invention, the control means detects the presence or absence of abnormality of the image sensor during the light amount adjustment processing period, so that various controls can be integrated and the cost can be reduced. Further, it is possible to stably and stably maintain the image quality of the read image with high quality.

[Brief description of drawings]

FIG. 1 is a block diagram of a main part of an image reading apparatus to which an embodiment of an image reading apparatus of the present invention is applied.

FIG. 2 is a diagram showing a relationship between a reference voltage output from an AD converter by a control unit of the image reading apparatus in FIG. 1 and a peak value of an image signal obtained by digitally converting an analog image signal from a sensor with the reference voltage.

FIG. 3 is an explanatory diagram of a light amount adjustment process of a light source of the image sensor by the control unit of FIG. 1.

4 is a flowchart showing a light amount adjustment process of a light source of the image sensor by the control unit of FIG.

[Explanation of symbols]

1 Image reading device 2 control unit 3 Light source drive circuit 4 AD converter 5 Sensor drive circuit 6 image sensor 7 light source 8 sensors

Claims (4)

[Claims] 1. A light source drive circuit is controlled by a control means, a light source of an image sensor is driven by the light source drive circuit to illuminate a document with light from the light source, and the sensor drive circuit is controlled by the control means. In the image reading device that drives the sensor of the image sensor to photoelectrically convert the reflected light from the document by the sensor to read the image of the document, the control unit outputs the image signal output from the sensor. According to the peak value of, the energy supplied to the light source is adjusted via the light source drive circuit, and a light amount adjustment process is performed to control the peak value of the image signal from the sensor to a constant value. Image reading device. 2. The control means drives the light source with the set supply energy via the light source drive circuit, and the peak of the image signal output from the sensor when the light source is driven with the set supply energy. The image reading apparatus according to claim 1, wherein a value is detected and the light amount adjustment process is performed based on the peak value. 3. The image according to claim 1 or 2, wherein the control means calculates the energy supplied to the light source as a ratio to the reading time of one line and performs the light amount adjustment processing. Reader. 4. The image reading apparatus according to claim 1, wherein the control unit detects whether or not there is an abnormality in the image sensor during the light amount adjustment processing period.