JPH0923309A - Image read sensor driving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To adjust the output timing of a driving pulse to a sensor so that a stable video signal can be obtained even at the time of high-speed driving of a contact sensor. SOLUTION: The driving pulse (CLK signal) outputted from a driving pulse output part 11 is combined with a select signal (SL signal) outputted from a select signal output part 12 and is branched and outputted to a first NAND circuit 13 and a second NAND circuit 14. A path B1 which passes from the first NAND circuit 13 as it is and a path B2 which passes a delay circuit 16 from the second NAND circuit 14 are finally combined by a final NAND circuit 17 to generate two CLKDLY signals which drive the contact sensor. If a level difference occurs in the video output waveform, one of these CLKDLY signals is properly selected to drive the contact sensor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading sensor driving device applied to a document reading device such as a facsimile machine, a copying machine, and a scanner for scanning a document.

[0002]

2. Description of the Related Art Conventionally, as an image reading sensor in a document reading device, an imaging lens, a CCD (charge coupled device) is used.
A CCD reading sensor including a line sensor and the like is known. This CCD reading sensor generally has a stable period in the video output waveform, and an analog signal is output during this stable period.
The video signal is converted into a digital signal by an A / D converter. In this type of reading sensor, various proposals have been made and implemented in order to satisfactorily process the video signal obtained by the CCD.

In the invention disclosed in Japanese Patent Laid-Open No. 1-318467, if the output level of a video signal is a prescribed value, the video signal is amplified and then output, and the sensitivity of a light receiving element such as a CCD is poor, or a light source is used. If the illuminance is low and the output level is low, a configuration is proposed in which the gain control circuit amplifies and then outputs after passing through a noise filter.

In the invention of Japanese Patent Application Laid-Open No. 1-218271, an output of a pixel having the maximum bright output is detected using a photodetector circuit, a difference from the dark output is obtained, and the difference (dynamic range) is defined. We propose a configuration to control the storage time so that

Further, in recent years, as an image reading sensor, an image forming element composed of a small lens group having a short focus along a main scanning direction of an image reading portion and a plurality of reading semiconductor sensors arrayed continuously are provided. A so-called contact sensor, which is installed, tends to be used. This contact sensor has a much smaller area and volume than the CCD reading sensor including the above-mentioned imaging lens and CCD, and the space and size of the entire apparatus can be reduced.

[0006]

In the CCD reading sensor described above, since the image to be read is formed on the CCD by the image forming lens, the scale of the CCD of one pixel can be reduced by the magnification. Since the sensor has a configuration in which a plurality of reading semiconductor sensors having a length corresponding to the document size width are arranged in one line in the main scanning direction, the scale per pixel must be the same size and becomes large. Will end up. Therefore, in the contact sensor, it takes time for the amount of charge accumulated in the photo element forming each pixel to be sufficiently saturated, and there are constraints such as that the wiring becomes longer than in the CCD reading sensor. High speed drive is not possible compared to CCD reading sensor.

However, in a facsimile machine, a copying machine or the like, it is a product claim that the user is restrained for a long time when reading a document. Therefore, it is necessary to enable high speed driving even if a contact sensor is used.

FIG. 8 is an output waveform diagram and a timing chart when the contact sensor is actually driven at high speed. Charge is accumulated in the photo element while the CLK (driving clock) signal (FIG. 8 (b)) is LOW. The HIGH period is a reset period in which the charge accumulated in the photo element is discharged. As in the video output waveform of FIG. 8A, there is no stable period in the charge period during high speed driving, so A / D conversion is performed at an appropriate timing (arrow of ADSMPL in FIG. 8C). Timing).

However, since there are variations in the characteristics of the contact sensor lots, it is not always possible to obtain the same level of video output. Further, as shown in FIG. 8A, since the video output has a waveform having a slope, when the level is high, the dynamic range of the A / D converter is exceeded and the gradation is lost. There is a risk
On the contrary, when the level is low, there is a problem that the dynamic range becomes narrow and the S / N ratio becomes worse.

The invention described in the above-mentioned publication cannot cope with such a problem because it is premised that the video output waveform is stable.

Therefore, the present invention provides an image reading sensor driving device in which the output timing of a driving pulse to the sensor can be adjusted so that a stable video signal can be obtained even when the contact sensor is driven at a high speed. With the goal.

[0012]

In order to achieve the above-mentioned object, the present invention provides a plurality of image-forming elements consisting of a small-lens group having a short focus and arranged continuously along the main scanning direction of an image reading portion. In the image reading sensor driving device that outputs a driving pulse to the image reading sensor having the read semiconductor sensor installed,
The present invention is characterized in that a case where the drive pulse is directly output and a case where the drive pulse is output through a delay circuit composed of a capacitor and a resistor are selectable.

In the image reading apparatus, resistors having different resistance values are connected in parallel to the drive pulse output section for outputting the drive pulse to the image reading sensor,
Further, a switch is connected to each resistor in series, and further, there is provided a selection means for turning on / off each switch to select a resistor through which the drive pulse from the drive pulse output section passes, and output from the selected resistor. The drive pulse thus generated is output to the image reading sensor via the buffer.

In the image reading apparatus, a resistor is connected to a drive pulse output section for outputting a drive pulse to the image reading sensor, bypass capacitors having different capacities are connected, and each bypass capacitor is connected to the bypass capacitor. A switch is connected in series, and further, there is provided selection means for turning on / off each switch and selecting a bypass capacitor through which the drive pulse from the drive pulse output section passes.
The drive pulse output through the delay circuit including the selected bypass capacitor and the resistor is output to the image reading sensor via the buffer.

Further, in the image reading apparatus, the drive pulse output section for outputting the drive pulse to the image reading sensor is connected in parallel with the buffer connection sections having different numbers of buffer connections, and the buffer connection section is provided with a switch. Are connected in series, and further, there is provided a selection means for turning on / off each switch to select a buffer connection part through which the drive pulse from the drive pulse output part passes, and the drive pulse output from the selected buffer connection part. Is output to the image reading sensor via the final stage buffer.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram for explaining the overall configuration of the first embodiment of the present invention. 1 is a known contact sensor, 2 is a contact sensor 1 based on a reference drive pulse (CLK signal). A CLK selection unit for appropriately selecting and outputting a drive pulse (CLKDLY signal) for driving the detector 3, and a detection unit 3 for detecting various signals from the video signal obtained by the contact sensor 1 driven based on the CLKDLY signal. Is an A / D that converts the analog video signal into a digital signal
It is a converter.

FIG. 2 is a circuit diagram of the CKL selection unit in the first embodiment, 11 is a drive pulse (CLK signal) output unit, and 1 is a drive pulse (CLK signal) output unit.
2 is a selection signal (SL signal) output unit, 13 is a drive pulse output unit 11
A first NAND circuit connected to the selection signal output unit 12 and a second NAND circuit 14 connected to the selection signal output unit 12 via the inverter 15 and a drive pulse output unit 11; A delay circuit (integrator circuit) composed of a resistor R and a capacitor C connected to the second NAND circuit 14,
Reference numeral 17 is a final NAND circuit that receives the drive pulse from the first NAND circuit 13 or the drive pulse from the second NAND circuit 14 via the delay circuit 16, and 18 outputs the CLKDLY signal that directly drives the contact sensor 1. It is an output unit that does.

Next, the operation of the first embodiment having the above structure will be described. The first to combine the CLK signal with the SL signal
A path that branches and outputs to the NAND circuit 13 and the second NAND circuit 14 and directly passes through the first NAND circuit 13.
B1 and the path from the second NAND circuit 14 through the delay circuit 16
The final NAND circuit 17 is combined with B2 and CL
Generate a KDLY signal.

FIG. 3 is a timing chart for explaining the operation in the first embodiment, in which the CLK signal (see FIG.
For (b)), the timing of A / D conversion by the A / D converter 4 is assumed to be the position indicated by the arrow in ADSMPL (FIG. 3 (a)). When the SL signal is HIGH, the first NA
Since the output of the ND circuit 13 becomes valid and the path B1 is selected, the CLKDLY.H signal with a small delay amount with respect to the CLK signal is output from the output unit 18 via the final NAND circuit 17 (Fig. 3 (c)). However, if the SL signal is LOW, the second
Since the output of the NAND circuit 14 becomes valid, the output passes through the delay circuit 16, and the CLKDLY · L signal with a relatively large delay is output from the output unit 18.
(Fig. 3 (e)).

By driving the contact sensor 1 based on the CLKDLY.H signal and the CLKDLY.L signal, a delay occurs in the video output waveform as shown in FIGS. 3D and 3F. Therefore, as described above, even if there is a level difference in the sloped video output waveform due to variations in the characteristics of the contact sensor, it is possible to cause a delay in the video output waveform by appropriately selecting the CLKDLY signal. A /
Stable A / D conversion is performed by the D converter 4, and good image output is performed.

The selection of the SL signal in the selection signal output section 12 is performed as shown in the flowchart of FIG. That is, the maximum output value V in the read signal of the known white reference plate, which is read when the shading correction is performed by the detection unit 3 in FIG. 1, is detected, and this maximum output value V and a value V _S which is defined in advance. Are compared (S1), and the SL signal is scanned (S2) until the relationship of the following (Equation 1) is satisfied (S1).

[0023]

[Number 1] _{| V-V S | <ΔV} ( although, [Delta] V certain constant) Then, employing the SL signal when the condition is satisfied in (Equation 1) (S3).

FIG. 5 shows CKL in the second embodiment of the present invention.
It is a circuit diagram of the selection unit, 21 is a drive pulse (CLK signal) output unit, R ₁ ~ R ₄ are connected in parallel to the drive pulse output unit 21 resistors of different resistance values (relationship of resistance values R ₁
<R ₂ <R ₃ <R ₄ ), 22a to 22d are switches connected in series to the resistors R _{1 to} R ₄ , and 23a to 23d are switches 22a to 2
2d is selectively turned on / off, and a selection signal (SL signal) output section for selecting the resistors R _{1 to} R ₄ through which the driving pulse passes, 24 is output from the selected resistors R _{1 to} R ₄ part A buffer for receiving the driving pulse, 25 is a CL for directly driving the contact sensor 1
This is the output unit that outputs the KDLY signal.

Next, the operation of the second embodiment having the above structure will be described. Path to which each resistor R _{1 to} R ₄ is connected
In B1 to B4, the delay characteristic differs depending on the difference in the resistance value. Therefore, the output of buffer 24 is
The delayed CLKDLY signal is different for each of the paths B1 to B4.
The path B1 has the smallest delay amount and the path B4 has the largest delay amount.

The selection of the SL signal in the selection signal output sections 23a-23d for deciding the on / off of the switches 22a-22d is as follows.
Similar to the above-described operation, the maximum output value V in the read signal of the known white reference plate read when performing the shading correction by the detection unit 3 in FIG. 1 is detected, and the maximum output value V is detected.
Is compared with a value V _S defined in advance, and the SL signal is scanned until the relationship of (Equation 1) is satisfied.

Specifically, first, the switch 22a set by default is in the ON state (all other switches are OFF), and the bright output maximum value V at this time is detected by the detection unit 3
If it does not satisfy (Equation 1) above,
The switch 22a in the path B1 is turned off and the switch 22b in the path B2 is turned on, and the detection is performed in the same manner. This detection is sequentially repeated in the paths B3 and B4 until the relationship of (Equation 1) is satisfied, and the SL signal when the condition of (Equation 1) is satisfied is adopted.

FIG. 6 is a CKL in the third embodiment of the present invention.
It is a circuit diagram of the selection unit, 31 is a drive pulse (CLK signal) output unit, R is a resistor connected to the drive pulse output unit 31, C ₁
To C ₄ are connected to the resistor R, and the bypass capacitors having different capacities (the relationship between the capacitance values of the capacitors is C ₁ <
C ₂ <C ₃ <C ₄ ), 32a to 32d are bypass capacitors C ₁
The switches 33a to 33d connected in series to C ₄ to C ₄ selectively turn on and off the switches 32a to 32d to select the bypass capacitors C _{1 to} C ₄ through which the driving pulse passes (SL signal). ) output unit, 34 is a buffer for receiving a drive pulse outputted from the bypass capacitor C ₁ -C ₄ portions is selected, 35 is an output unit for outputting CLKDLY signal for driving the contact sensor 1 directly.

Next, the operation of the third embodiment having the above structure will be described. In the path B1~B4 each bypass capacitor C ₁ -C ₄ are connected, the time constant of the integrating circuit consisting of a resistor R τ (= CR) becomes _{τ 1 <τ 2 <τ 3} <τ 4 respectively Therefore, the delay characteristic varies depending on the difference in the time constant. Therefore, the output of buffer 34 is
~ It becomes a delayed CLKDLY signal that differs for each B4. The path B1 has the smallest delay amount and the path B4 has the largest delay amount.

The selection of the SL signal in the selection signal output sections 33a to 33d for deciding on / off of the switches 32a to 32d is as follows.
Similar to the above-mentioned operation, the maximum output value V in the read signal of the known white reference plate read when performing the shading correction by the detection unit 3 in FIG. 1 is detected, and the maximum output value V is detected.
Is compared with a value V _S defined in advance, and the SL signal is scanned until the relationship of (Equation 1) is satisfied.

Specifically, first, the switch 32a set by default is in the on state (all other switches are off), and the bright output maximum value V at this time is detected by the detection unit 3
If it does not satisfy (Equation 1) above,
The switch 32a in the path B1 is turned off and the switch 32b in the path B2 is turned on, and the detection is performed in the same manner. This detection is sequentially repeated in the paths B3 and B4 until the relationship of (Equation 1) is satisfied, and the SL signal when the condition of (Equation 1) is satisfied is adopted.

FIG. 7 shows CKL in the fourth embodiment of the present invention.
It is a circuit diagram of the selection unit, 41 is a drive pulse (CLK signal) output unit, Bf _{1 to} Bf ₆ are paths connected to the drive pulse output unit 41.
A different number of buffers (0-3 in the figure) are installed for each of B1 to B4, 42a to 42d are switches connected in series to each path B1 to B4, and 43a to 43d are each switch 42a to 42d. Selection signal (SL signal) output section that selectively turns on / off the path B1 to B4 through which the drive pulse passes, 44 is the selected path B1 to B4.
Final buffer to receive drive pulse output from B4, 45
Is an output unit that outputs a CLKDLY signal that directly drives the contact sensor 1.

Next, the operation of the above-described fourth embodiment will be described. Assuming that the delay amount Δt of each Bf _{1 to} Bf ₆ is constant, the delay amount is zero in the path B1, the delay amount is Δt in the path B2, the delay amount is 2 × Δt in the path B3, and the delay amount is 3 in the path B4. × Δt. Therefore, the output of the buffer 44 becomes a delayed CLKDLY signal which is different for each of the paths B1 to B4. The path B1 has the smallest delay amount and the path B4 has the largest delay amount.

The selection of the SL signal in the selection signal output sections 33a to 33d for deciding on / off of the switches 32a to 32d is as follows.
Since the operation is the same as that described above, the description thereof will be omitted.

[0035]

As described above, according to the image reading sensor driving device of the present invention, when the contact sensor is driven at a high speed, a stable region cannot be obtained in its output waveform. Further, even if the output level varies, the drive pulse can be appropriately delayed in an analog manner, so that the signal processing can be performed in a stable state and a good video output can be obtained.

According to the present invention, when the contact sensor is driven at a high speed, a stable region cannot be obtained in the output waveform of the contact sensor, and even if the output level varies, the drive pulse is made in fine steps. Can be appropriately delayed in an analog manner, so that signal processing can be performed in a stable state according to the output situation, and a better video output can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram for explaining an overall configuration of a first embodiment of an image reading sensor driving device of the present invention.

FIG. 2 is a circuit diagram of a CLK selection unit according to the first embodiment of the present invention.

FIG. 3 is a timing chart for explaining an operation in the first embodiment of the present invention.

FIG. 4 is a flowchart regarding selection of SL signals in the first embodiment of the present invention.

FIG. 5 is a circuit diagram of a CLK selection unit according to the second embodiment of the present invention.

FIG. 6 is a circuit diagram of a CLK selection unit according to a third embodiment of the present invention.

FIG. 7 is a circuit diagram of a CLK selection unit according to a fourth embodiment of the present invention.

FIG. 8 is a diagram illustrating output waveforms and timings when the contact sensor is driven at high speed.

[Explanation of symbols]

1 ... Adhesion sensor, 2 ... Drive pulse selection unit, 3 ... Detection unit, 4 ... A / D converter, 11, 21 ... Drive pulse output unit, 12, 23a-23d, 33a-33d, 43a-43d ... Selection signal Output section, 13, 14, 17 ... NAND circuit, 15 ... Inverter, 16 ... Delay circuit, 18, 25, 35, 45 ... Output section, 22a
~ 22d, 32a ~ 32d, 42a ~ 42d ... switch, 24, 34, 4
4, Bf _{1 to} Bf ₆ ... Buffer, R, R _{1 to} R ₄ ... Resistor,
C ₁ ~C ₄ ... bypass capacitor.

Claims (4)

[Claims] 1. An image reading sensor comprising an image-forming element including a small-focus small lens group and a plurality of reading semiconductor sensors arranged in series along a main scanning direction of an image reading portion. On the other hand, in an image reading sensor driving device that outputs a driving pulse, a case where the driving pulse is directly output to the image reading sensor, and a case where the driving pulse is output through a delay circuit including a capacitor and a resistor An image reading sensor driving device characterized in that cases can be selected. 2. An image reading sensor comprising an image-forming element composed of a small lens group having a short focus and a plurality of reading semiconductor sensors arranged in series along the main scanning direction of the image reading portion. On the other hand, in an image reading sensor driving device that outputs a driving pulse, resistors having different resistance values are connected in parallel to a driving pulse output unit that outputs a driving pulse to the image reading sensor, and Switch in series and turn on each switch.
A selection means is provided for selecting a resistor which is turned off and through which the drive pulse from the drive pulse output section passes, and the drive pulse output from the selected resistor is output to the image reading sensor via a buffer. Image reading sensor driving device. 3. An image reading sensor comprising an image forming element composed of a small lens group having a short focus and a plurality of reading semiconductor sensors continuously arranged along the main scanning direction of the image reading portion. On the other hand, in an image reading sensor driving device that outputs a driving pulse, a resistor is connected to a driving pulse output unit that outputs a driving pulse to the image reading sensor, and bypass capacitors of different capacities are connected. Further, a switch is connected in series to each bypass capacitor, and further, there is provided selection means for turning on / off each switch to select a bypass capacitor through which the drive pulse from the drive pulse output section passes, and the selected bypass capacitor and The drive pulse output through the delay circuit including the resistor is output to the image reading sensor via the buffer. An image reading sensor driving device characterized by the above. 4. An image reading sensor comprising an image-forming element formed of a small lens group having a short focus and a plurality of reading semiconductor sensors arranged in series along the main scanning direction of the image reading portion. On the other hand, in the image reading sensor driving device that outputs the driving pulse, the driving pulse output unit that outputs the driving pulse to the image reading sensor, the buffer connection unit different in the number of buffer connections are connected in parallel, and Connect a switch in series to each buffer connection,
Further, there is provided a selection means for turning on / off each switch to select a buffer connection part through which the drive pulse from the drive pulse output part passes, and the drive pulse output from the selected buffer connection part is passed through the final stage buffer. The image reading sensor driving device is characterized by outputting the image reading sensor to the image reading sensor.