JP2604943B2 - Image reading device - Google Patents

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 for reading an original while illuminating a portion to be read in a facsimile apparatus or the like.

[0002]

2. Description of the Related Art In an image reading apparatus used in a facsimile apparatus or the like, as shown in FIG. 3, a light source 5 for illuminating a reading scanning range 4 of the image sensor 3 together with an optical system 2 and a line image sensor 3. The document 1 fed and driven in the sub-scanning direction Y is read line by line from the main scanning direction X.

As shown in FIG. 4, the illumination light source 4 is constituted by a plurality of light emitting units L1 to Ln, and each of the light emitting units L1 to Ln is constituted by one or a plurality of LEDs (light emitting diodes). Each of the light emitting units L1 to Ln is driven to be lit by the drive circuit 81.

Here, in this conventional apparatus, as shown in FIG. 5, the light emitting units L1 to Ln forming the illumination light source 4 are:
When the reading operation of the image sensor 3 is being performed, the driving circuit 81 is turned on all at once to illuminate the reading scanning range of the image sensor 3.

[0005]

However, according to this configuration, the power consumption of the illumination light source is large, which is a major factor that hinders the reduction in power consumption of this type of device. was there.

The above problem occurs for the following reasons. That is, since the illumination light source 5 needs to illuminate at least the entire scanning range of the line image sensor 3, it is configured using a large number of light emitting elements such as LEDs (light emitting diodes). Considerable high power is consumed.

However, in order to reliably read the image sensor 3, it is necessary to illuminate the reading portion with a certain brightness or more.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above-described problems, and has as its object to provide an image reading apparatus that provides a necessary illuminance to a reading portion of an image sensor and that consumes much less power. .

[0009]

According to the present invention, there is provided an image sensor for reading and scanning an original or the like.
A clock generating means for generating a pixel cycle clock and a line synchronization clock for defining a read operation timing of the image sensor; and a reading scan range of the image sensor sequentially for each light emission unit having a plurality of the pixel cycle clocks as one unit. A light source to be illuminated, a pixel cycle clock generated by the clock generation means , and a line
A counter for counting the synchronous clock and a counter for this counter
The light source is turned on until the numerical value reaches a first predetermined value.
And more than half of the first predetermined value and
The second predetermined value set below the first predetermined value is counted.
Each time the light source is turned on corresponding to the scanning range
Driving means for lighting, and detecting the line synchronization signal
The count value of the counter is reset, and the next
Configuration of control means for controlling lighting of the light source of the line
It is provided with.

[0010]

According to the present invention, the pixel period clock is generated by the above configuration.
The image sensor reads the information based on the
Illuminates the reading range with a light source and counts the pixel cycle clock
And the count value of this counter reaches a first predetermined value.
Until the reading scan range is illuminated with the light source until
It is set to be greater than half of the fixed value and less than the first predetermined value.
Reading each time the second predetermined value is counted
Turn on the light source corresponding to the scanning range, and
When detected, the count value of the counter is reset and the next line
The lighting control of the light source is performed.

[0011]

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

In the drawings, the same reference numerals indicate the same or corresponding parts. FIG. 1 shows a schematic configuration of an image reading apparatus according to an embodiment of the present invention. Reference numeral 3 denotes a line image sensor for reading and scanning a document 1 fed and driven in a sub-scanning direction in a main scanning direction. Is a reading scanning range (main scanning range) of the image sensor 3, 5 is a light source for illuminating a reading portion of the image sensor 3, 6 is a reading control circuit for controlling a reading operation of the line image sensor 21, and CK1 and CK2 are A pixel synchronization clock and a line synchronization clock for defining the reading operation timing of the sensor 6, a counter 7 for counting the scanning position on the main scanning line of the line image sensor 3 by the clocks CK 1 and CK 2, and a counter 8 for the scanning According to the count value of the counter 7, that is, the reading scanning position of the image sensor 3, the light emitting units L1 to L A selection drive circuit for selectively lighting the.

Here, the counter 7 is incremented (Cin) by the pixel synchronization clock CK1 and reset (R) by the line synchronization clock CK2 to indicate the actual reading scanning position of the line image sensor 3. The data is output as a binary-coded count value. Selective drive circuit 8
Decodes the count value output from the counter 7 into an alternative selection signal, and outputs each of the light emitting units L1
To Ln are selectively driven for lighting.

The operation of the image reading apparatus configured as described above will be described below. In the above-described apparatus, as shown in FIG.
As for n, only those optically corresponding to the reading scanning position of the line image sensor 3 are selectively turned on by the pixel synchronization clock CK1 and the line synchronization clock CK2. That is, when the line image sensor 3 is reading and scanning the range illuminated by a specific light emitting unit, only the light emitting units contributing to the illumination at the read scanning position are selectively turned on. Other light emitting units are turned off. In this way,
While the light emitting units that are turned on are sequentially changed in accordance with the reading scanning position of the image sensor, the entire reading scanning range of the image sensor is illuminated.

[0015] Thus, while giving the necessary illuminance to the reading portion of the image sensor, the light-emitting units that are turned on at the same time are limited to only the portion necessary for the reading operation of the image sensor, and the power for illumination is greatly reduced. Reduced. At the same time, since the number of light-emitting units that are turned on at the same time is small, the output current capacity of the power supply device only needs to be prepared by the number of light-emitting units that are turned on at the same time.

The lighting of the light emitting units L1 to Ln is as follows.
In order to eliminate variations in the illuminance due to the reading scanning position, for example, as shown in FIG.
, L2, L2 and L3,...) May be partially overlapped. Further, as the illumination light source, a light emitting element or unit other than the LED can be used as long as it can be instantaneously activated.

[0017]

According to the present invention, as described above, the pixel period
Counter is counted by the counter, and the first predetermined value is counted.
During this time, the light source is turned on, and the light source is more than half of the first predetermined value.
And a second predetermined value set below the first predetermined value.
When the value is counted, the adjacent light sources are sequentially turned on
Turn on only the light emitting unit corresponding to the scanning position
Power consumption for emitting light.
It can be. Partial overlap
At this time, only one light source
Lighting time can be provided to reduce power consumption
Is what you can do. Also detects line sync signal
Then, the counter value is reset and the light of the next line is reset.
By controlling the power source, the control configuration for each line can be simplified.
Can be easier.

[Brief description of the drawings]

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

FIG. 2 is a timing chart showing a lighting state of each light emitting unit of an illumination light source in the device of the present invention.

FIG. 3 is a schematic diagram showing an example of an arrangement of an image sensor and an illumination light source.

FIG. 4 is a schematic configuration diagram of a conventional image reading apparatus.

FIG. 5 is a timing chart showing a lighting state of each light emitting unit of an illumination light source in a conventional device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Original 3 Line image sensor 4 Reading scanning range 5 Illumination light source L1-Ln Light emitting unit 6 Reading control circuit 7 Counter 8 Selection drive circuit

Claims (1)

(57) [Claims] An image sensor for reading and scanning an original or the like, a pixel cycle clock for defining a read operation timing of the image sensor, a clock generating means for generating a line synchronization clock, and the pixel cycle clock A light source for sequentially illuminating the reading scan range of the image sensor in units of light emission with one unit of a plurality of clocks, a pixel cycle clock generated by the clock generating means ,
Counter for counting the in-sync clock and this counter
The light source is turned on until the count value of the light source reaches a first predetermined value.
And more than half of the first predetermined value,
A second predetermined value which is set below the first predetermined value
Each time the light source is counted, the light source
Driving means for lighting the line, and detecting the line synchronization signal.
Resetting the count value of the counter,
And a control unit for controlling the lighting of the light source of the next line .