JPS6032471A - Original reading device - Google Patents

Abstract

PURPOSE:To eliminate wasteful power consumption by controlling the light emission of plural light emission elements of a light emission element array, and thereby making exposure of the part of picture to be read. CONSTITUTION:An original 401 is carried in the direction of the arrow by carrying rollers 405, 406 of an original reading device, and light from plural light emission diode (LED) array 402 is irradiated onto the original 401. Reflected light from the original 401 is projected onto an image sensor 403 and converted to an electric signal corresponding to the intensity of incident light, and outputted. Power source is supplied from a power source 408 in parallel to each LED of the array 402 through a resistance R. Another terminal of each LED is connected to a data selector 407 by selector lines SEL1-N. An address counter 406 that counts basic clock f0 from an oscillator 405 is connected to the selector 407. The output of the counter 406 is added to the selector 407 as an address, lines SEL1-N are selected and enabled. Thus, only the part of a picture to be read is exposed to reduce power consumption.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a document reading device that photoelectrically reads a document image.

Conventional technology It is known to photoelectrically read original images using an image sensor such as 3D. Therefore, it is effective in the field of image processing.

In a reading device that performs such a reading operation, uniform exposure is performed over the entire document, regardless of the size of the document. Therefore, even when reading a small original such as a postcard, areas other than the original are also exposed. Therefore, the light source is driven more than necessary, resulting in wasted power.

Purpose The present invention has been made in view of the above points, and it is an object of the present invention to provide a document reading device that can prevent unnecessary exposure and save power with a simple configuration. The present invention will be explained in more detail using the following.

FIG. 1 is a diagram showing the configuration of a document reading device to which the present invention is applied. In the figure, 401 is a document with the image surface to be read facing upward. 04o2 is an LED array in which a plurality of LEDs (light emitting diodes) are arranged over a length that covers at least the width of the original 5401. be. 4
03 is an image sensor made of a photoelectric conversion member made of cadmium sulfide Gas or the like. 405 and 406 are a pair of transport rollers for moving the original in the direction of the arrow.

A document 401 that is moved in the direction of the arrow by a pair of transport rollers 405 and 406 is illuminated by an LED array 402 via, for example, a rod array lens. The light reflected from the original 4 [ ] 1 by this irradiation enters the image sensor 403 and is converted into an electrical signal according to the intensity of the incident light 0ξ
As a result, the original 401 is read line by line.

FIG. 2 shows the general configuration of the LED array 4[]2(7). 200 is a substrate (wafer), the substrate 200
A light emitting material O'1 such as GaAθ is formed thereon.

Reference numeral 201 denotes N electrodes, and N light emitting parts 20 are installed in this ton field.
2 is formed in a staggered pattern as shown in the figure;). This light emitting part 2
02 has a high density, for example, 16 elements or more per 1 mm. The surface density matches the resolution of the image sensor 403.

FIG. 3 shows a drive circuit for the LED array 402.

A power supply 408 supplies power to each LED of the LED array 402 in parallel via a resistor R. The other terminals of the LED array are the select lines 5ELI to N of the data selector 407.
It is connected to the. 405 is an oscillator that outputs the basic clock fo, and 406 is an address counter that outputs address data for selecting the lit LED by counting the basic clock fo from the oscillator 405. Data selector 407 energizes the select line corresponding to the busy LED to be lit based on the address data from the address counter 406. This allows the selected LE
Power is supplied to D, and the LED lights up. In this way, each LED of the LED array 402 is individually selected to turn on or off. The image sensor 403 is shaped like a single plate, as shown in Figure 6, and depends on the intensity of light incident on that position. Charge is accumulated in a corresponding distribution. This accumulated charge is transferred in the direction of the arrow and amplified by a predetermined amount by an amplifier 404, and then output from the output terminal OUT.
output as an image signal.

FIG. 4 shows a timing chart related to LED lighting selection. As shown in the figure, the basic clock f.

At the rising edge of , sequentially select 1s EL1~N becomes an electric current~・ku0 As a result, N LEDs are sequentially lit. Figure 5 shows the relationship between the LED light emitting elements and the applied current. 0 or Figure 6 t'', L 1! : D array 402
is used as the photoelectric conversion element 702, and generally Gu,
It is said that speeding up can be achieved by mixing CI and Se. Note that 701 is an electrode.

The maximum sensitivity peak is around 555 nm, which is the KLED
In order to achieve wavelength matching with the array, it is said that liquid phase epitaxy (LPE)) N junction formation using a GaP system is recommended for LEDs.

Now, assume that the width of the document to be read is 1/2 of the maximum readable width. In this case, it is not necessary to light up all N LEDs. Therefore, in order to light up N/2 LEDs, the address counter 406 outputs the 5IZE signal 1tc.
, controls the address to the data selector 407.

In accordance with the address corresponding to this size, the data selector 407 outputs only the necessary selection signals SEL1 to SELN to the I and ED array 02 in order to light up only the necessary LEDs.

As a result, only the necessary LEDs among the N LEDs of the LED array 402, in this case, only J/2 LEDs are lit.

In order to selectively light up the necessary LEDs, in addition to this, a means for individually gating the sequentially output select signals SEL i to N is provided, and if necessary, the SEL signal sE
It is also possible to avoid applying L to the LED 7 ray 402.

Effects As explained above, according to the present invention, since the original exposure l] can be controlled according to the size of the original, unnecessary lighting is not performed, and wasteful consumption of power can be prevented.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a document reading device to which the present invention is applied, M2
Figure 6 is a configuration diagram of the LED array, Figure 6 is a drive circuit diagram of the LED array, Figure 4 is a timing chart diagram showing the signal output of each part in Figure 3, Figure 5 is a diagram showing the light emission characteristics of the LED, Figure 6 is a diagram showing the relationship between the light emission of the LED and the sensitivity of the image sensor, and Figure 7 is a configuration diagram of the image sensor.
401 is a document, 402 is an LED array, and 406 is an image sensor. Applicant Canon Co., Ltd.

Claims (1)

[Claims] a light-emitting element array for document exposure consisting of a plurality of light-emitting elements;
an image sensor that reads an image of the original based on light reflected from the original, and exposes only the image portion to be read by controlling the light emitting operation of the light emitting elements of the light emitting element array. Device.