JPH11215316A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain level adjustment of a video input signal when an original is read with an inexpensive and simple reader configuration by using plural analog switches for adjusting the current of an LED array. SOLUTION: A light emitted from an LED array 11 is emitted onto an original, an A/D converter 2 converts an analog video input signal resulting from its reflected light into a digital video input signal and is given to an image processing controller 5. The controller 5 detects a peak level of the converted video input signal, and a CPU 7 discriminates whether or not the detected peak level has reached a prescribed level. When the peak level is not a prescribed level, an LED current adjustment circuit 3 adjusts the current of the LED array through the on/off control of plural analog switches.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image reading apparatus having a scanner device using an LED array as a light source.

[0002]

2. Description of the Related Art Conventionally, an average value of a plurality of continuous images in a main scanning direction of a document within a predetermined number of pixels has been detected, and DA
By the feedback from the converter,
An image reading apparatus (for example, Japanese Patent Application Laid-Open No. HEI 6-189132) capable of performing optimal AD conversion by adjusting the amplification factor of the amplification means and the reference of the A / D converter.
And the like, and gain adjustment using an operational amplifier or LE using a D / A converter is known.
The level of the video input signal was adjusted by adjusting the current of the D array.

[0003]

However, if the level of the video input signal is adjusted by the gain adjustment using an operational amplifier as in the prior art, the adjustment range becomes narrow, and D
Adjusting the level of the video input signal by adjusting the current of the LED array using the / A converter has a problem that an expensive and complicated device configuration is required. In addition, there has been a problem that it takes time and effort to change the circuit according to the scanner characteristics when adjusting the gain.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and the current adjustment of an LED array using a plurality of analog switches makes it possible to adjust the level of a video input signal at the time of reading a document at low cost and in a simple manner. It is intended to be able to be performed by an apparatus configuration.

[0005]

According to the present invention, there is provided an image reading apparatus for irradiating a document with light emitted from an LED array and reading an image of the document based on the reflected light. Means for converting an optical video input signal from analog to digital, means for detecting the peak level of the video input signal converted by the means, and means for determining whether the peak level detected by the means is a predetermined value And means for adjusting the current of the LED array by on / off control of a plurality of analog switches when the peak level is not a predetermined value.

It is preferable to provide a means for changing the adjustment curve of the current of the LED array and a means for changing a control method for adjusting the current of the LED array. In addition, the above LED
It is preferable to provide means for controlling turning on and off of the array by on / off control of one analog switch.

[0007]

Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of an image reading apparatus according to an embodiment of the present invention, FIG. 2 is a detailed configuration diagram of the LED current adjustment circuit, and FIG. 3 is a flowchart showing LED current adjustment processing in this image reading apparatus. It is.

This image reading apparatus has a configuration as shown in FIG. 1. A scanner apparatus 1 uses an optical sensor 10 such as a contact sensor or a CCD, and an LED array 1 as a light source.
1, the original is irradiated with light from the LED array 11, the reflected light is received by the optical sensor 10, and the amount of reflection of the received reflected light is converted into an electric signal, thereby forming an image on the original. The reading is performed, and the read analog video signal is output to the A / D converter 2.

The A / D converter 2 converts an analog video signal input from the optical sensor 10 into an 8-bit digital video signal and outputs the digital video signal to the image processing controller 5. The LED current adjusting circuit 3 has a circuit configuration as shown in FIG. 2, and adjusts a current value of the LED array 11 of the scanner device 1 according to the present invention. The timing generator 4 outputs a drive signal suitable for the scanner device 1 and drives the scanner device 1.

The image processing controller 5 applies dark output correction processing, shading correction processing, peak level correction processing to the digital video signal input from the A / D converter 2.
Various correction processes such as a gamma correction process and an automatic density adjustment process are performed, and the digital video signal is finally converted into binary data of “black” and “white” and output to the RAM 9.
The parallel port interface 6 outputs “0” and “1” electric signals to the LED current adjustment circuit 3.

The CPU 7 is a microcomputer that controls the entire apparatus such as the image processing controller 5 and the like. R
The OM 8 is a memory that stores a firmware program for controlling the entire device by the CPU 7. RAM9 is C
A memory that provides a work area when the PU 7 executes various control processes and stores binarized data output from the image processing controller 5.

Next, the processing of the image processing apparatus will be described. When the apparatus power is turned on, the timing generator 4 outputs a drive signal to the optical sensor 10 according to the specifications of the scanner. The optical sensor 10 enters an operating state in response to the drive signal, and executes a command for collecting shading correction data before reading a document. Collection of data used for shading correction is L
One line is read with the ED array 11 turned off, and the dark output data of the read data is stored in the RAM 9.
To be stored.

[0013] Then, after several lines have been synced,
The bright output data is read with the array 11 turned on. At this time, the image processing controller 5 detects a peak value in one line, and when the peak value is a predetermined value,
The shading correction data is taken in the next line. On the other hand, when it is not the predetermined value, the setting value of the LED current adjustment of the LED current adjustment circuit 3 is changed, and the LED current adjustment processing is continued so that the peak value becomes the predetermined value.

That is, as shown in FIG. 3, in step (indicated by "S" in the figure) 1, a white reference original is set, and the process proceeds to step 2 to capture dark output data. Then, the process proceeds to step 4 to fetch the peak level (peak value) of bright output data in one line read from the document, and proceeds to step 5 to determine whether the peak level is a predetermined value.

If the peak level is not the predetermined value in the determination at step 5, the process proceeds to step 6 to change the setting of the LED current value, and returns to step 5 to repeat the above determination again. Step 9 if value
Then, go to step 7 to store and save the set value of the LED current adjustment in the RAM. Then, go to step 7 to take in the shading data, go to step 8, and turn off the LED light source.
This processing ends.

In this way, the process of adjusting the LED current value so that the peak value becomes a predetermined value while the set value of the LED current is initially maximized and decremented one by one is performed.

At the time of the above adjustment processing, the LED current adjustment circuit 3
As shown in FIG. 2, a control signal "0" or "1" output from a parallel port of the parallel port interface 6 is transmitted to a plurality of analog switch control terminals LEDCNT0.
To each of the analog switches SW0
~ SW4 is turned on or off, and each analog switch S
Each resistor R0 connected to both ends of W0 to SW4 respectively
By short-circuiting or opening R4, the input level of the operational amplifier input section OP is changed to change the set value of the LED current value, thereby adjusting the LED current.

The connection and resistance value of the LED current adjusting circuit 3 are variable, and can be adjusted according to the characteristics of each type of scanner. Also, by storing the set value of the LED current when the peak level reaches a predetermined value in the RAM 9, the set value stored in the RAM 9 is always stored when the power is turned on, unless a command for collecting shading correction data is executed next time. Can be read to set the LED current value.

Further, in order to change the control according to the type of the scanner, it is preferable to input a switch signal for identifying the scanner to the input section of the parallel port interface 6 so as to adapt the scanner control procedure based on the switch signal. .

For example, in the case of a scanner having a large LED current value, a state where the LED current value is maximized is set to a default setting value, and the setting value is gradually reduced when adjusting the LED current. Accordingly, the time required for collecting the shading correction data can be reduced. When the adjustment interval becomes large when the current value is large, L
The ED current adjustment circuit 3 is changed to a circuit having a curve that is optimal for the adjustment of the LED current, and the control procedure is also adjusted by skipping one predetermined current range and one by one in the other current ranges. It is preferable to change the control procedure of the LED current adjustment.

In this image reading apparatus, LED current adjustment can be set only by controlling on / off of a plurality of analog switches, and it is possible to correct variations in video input signals with an inexpensive and simple apparatus configuration. In addition, since the circuit is shared, adjustment and control according to the characteristics of the scanner device can be realized only by changing the mounted components. In addition, LE
When the D array is turned off, it is possible to eliminate a problem that the D array is not completely turned off even if the level is adjusted to the lowest level.

[0022]

As described above, according to the image reading apparatus of the first aspect of the present invention, since the current adjustment of the LED array is performed by controlling the on / off of the plurality of analog switches, the apparatus is inexpensive and simple. It is possible to adjust the level of a video input signal when reading a document.

Further, according to the image reading apparatus of the second aspect,
An optimum circuit configuration and an LED current adjustment value can be set according to the characteristics of the scanner device. Further, according to the image reading apparatus of the third aspect, when the current adjustment of the LED array is set to the minimum level, the LED array can be completely turned off.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an image reading apparatus according to an embodiment of the present invention.

FIG. 2 is a detailed configuration diagram of an LED current adjustment circuit of the image reading apparatus shown in FIG.

FIG. 3 is a flowchart illustrating an LED current adjustment process in the image reading apparatus illustrated in FIG. 1;

[Explanation of symbols]

 1: Scanner device 2: A / D converter 3: LED current adjusting circuit 4: Timing generator 5: Image processing controller 6: Parallel port interface 7: CPU 8: ROM 9: RAM 10: Optical sensor 11: LED array

Claims (3)

[Claims] 1. An image reading apparatus that irradiates a document with light emitted from an LED array and reads an image of the document based on the reflected light, a unit that converts a video input signal of the reflected light from analog to digital, Means for detecting the peak level of the video input signal converted by the means, means for determining whether the peak level detected by the means is a predetermined value, and when the peak level is not the predetermined value, Means for adjusting the current of the LED array by on / off control of a plurality of analog switches. 2. The image reading apparatus according to claim 1, further comprising: means for changing a current adjustment curve of the LED array; and means for changing a current adjustment control method of the LED array. Image reading device. 3. The image reading apparatus according to claim 1, further comprising means for controlling turning on and off of the LED array by on / off control of one analog switch.