JPS61179665A - Method for controlling received light quantity of photodetector - Google Patents

Abstract

PURPOSE:To decrease the variance in received light quantity of a photodetector by allowing the photodetector to detect the information of a reference original obtained from the rays of light lighting a light emitting element at a reference lighting voltage and generating a correcting voltage to correct the deviation of the detected voltage of the said photodetector from a reference output voltage of the photodetector. CONSTITUTION:Each light emitting element reads a reference original and a correction voltage controlling the luminous quantity in the relation corresponding one to one to each light emitting element 10 is stored in a memory 22 as a digital value. Then a signal from a control circuit 14 is used to read the correction voltage of an address location designated in the memory 22, the signal is converted into the power voltage of a corresponding light emitting element, that is, a lighting voltage by a D/A converter circuit 24, the voltage is fed to the designated dot of the light emitting element array 10 via a light emitting element drive circuit 12. Thus, each dot of the light emitting element array 10 is controlled by power voltage information stored in the memory 22 coming from the luminous quantity in advance and the variance in the received light quantity of the photodetector caused by all circuits in a reader including the light emitting array, an optical system circuit and a light receiving system circuit is decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention provides a light emitting element array I-h in an optical reading device.
The present invention relates to a method for reducing variations in the amount of light received by a light receiving element when reading with a dice.

(Prior Art) Optical reading devices have conventionally been incorporated into many information devices including facsimile machines. These optical reading devices use a light emitting element array, which is made up of a large number of light emitting elements such as light emitting diodes and liquid crystal switches arranged in a straight line, as a light source.The light from this light emitting element array is applied to the document, and the light reflected from the document or Information is read by detecting the transmitted light with light receiving elements arranged corresponding to each light emitting element (for example,
Proceedings of the 11th (Showa 58) National Conference of the Society of Image Electronics Engineers,
34, p1-4).

However, if there are variations in the amount of light emitted from each light emitting element (referred to as C dots), a difference in brightness will occur between each dot. For example, when printed out using a facsimile machine, density unevenness will occur in the reproduced information. Put it away.

Therefore, in the past, a laser trimming device was used to
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A method is used in which the amount of current supplied to each element is individually adjusted to equalize the amount of light emitted from each element.

(Problems to be Solved by the Invention) However, with the trimming method, determining the trimming value is complicated, the trimming accuracy is not sufficient, and moreover, a trimming device must be installed, so it is not easy to use. The drawback was that it could not be implemented.

Furthermore, this trimming method has the disadvantage that it is not possible to reset the amount of light emitted, and therefore it is not possible to deal with changes in the amount of light emitted.

Furthermore, the trimming method is a correction for the light emitting element array itself, and uses a lens etc. added at the subsequent stage to compensate for variations in the amount of light received due to the influence of the optical system circuit and the light receiving system circuit using the light receiving element. The drawback was that it was not possible.

In view of these conventional drawbacks, it is an object of the present invention to reduce variations in the amount of light received by light receiving elements caused by the light emitting element array, optical system circuit, light receiving system circuit, and other circuits. Another object of the present invention is to provide a method for controlling the amount of light received by a light receiving element, which allows the control to be performed at all times.

(Means for Solving the Problem) In order to achieve this object, according to the method of the present invention, when reading document information with a reading light receiving element in an optical reading device using light from a light emitting element array, In order to control the amount of light received by the light-receiving element, the light-receiving element detects the information of the reference document using light emitted from the light-emitting element at a reference emission voltage;
A correction voltage is formed by correcting the amount of deviation of the detection voltage of the light receiving element from a reference output voltage of the light receiving element, and the corrected voltage is stored in the address position of the light emitting element in a memory.1 When reading a normal document, The present invention is characterized in that a correction voltage stored in a corresponding address position of a memory is read out for each light emitting element, and the light emission voltage of the light emitting element is controlled in accordance with the correction voltage.

In this case, the reference original can be an original that has an optically uniform surface and has uniform reflectance or transmittance over its entire surface.

Further, the reference light emission voltage when reading the reference original is set to the same constant power supply voltage for each light emitting element.

Further, the reference output voltage from the light-receiving element is an ideal detection voltage when there is no influence due to the light-emitting element, optical system circuit, light-receiving system circuit, etc. when the reference emission voltage is applied to the light-emitting element.

(Operation) FIG. 1 is a block diagram of an optical reading device for explaining the present invention in detail.

IO is a light emitting element array, 12 is this light emitting element array 10
A light emitting element drive circuit for individually causing each light emitting element (representatively shown as 10) to emit light, for example, is composed of a power supply voltage circuit and a switch circuit, and 14 is a control for controlling this light emitting element drive circuit 12. In the circuit, the light emitting element 21 n L= @ ce to be caused to emit light by this control circuit 14
+Gaya 1 no 1. It is configured to emit light. moreover.

16 is an optical system circuit, 1B is a reading light receiving element, and the light from the light emitting element array 10 is used to transmit document information to the light receiving element 1.
8, the light receiving system circuit 20 appropriately amplifies the signal, and outputs the signal. Note that these configurations are the same as the conventional ones, so a detailed explanation thereof will be omitted.

In the method of the present invention, a reference document is read by each light emitting element, and a correction voltage for controlling the amount of light emitted by each light emitting element 10 in one-to-one correspondence is stored in the memory 22 as a digital value. Therefore, in response to a signal from the control circuit 14, the correction voltage value at the specified address position in the memory 22 is read out and converted into the power supply voltage of the corresponding light emitting element, that is, the light emitting voltage in the Il/A conversion circuit 24, and the light emitting element driving circuit 12 to designated dots of the light emitting element array 1G. In this case, the correction voltage value may correspond to the light emission voltage, or the correction voltage value may provide the amount of correction to the reference light emission voltage.

Incidentally, 26 is an A/D conversion circuit for converting the correction voltage into a digital value in order to store it in the memory 22.

In this way, the amount of light emitted by each dot of one light emitting element array lO is controlled by the power supply voltage value information stored in advance in the memory 22, and therefore the reading device including the light emitting element array, optical system circuit, light receiving system circuit, etc. It is possible to reduce variations in the amount of light received by the light receiving elements due to all the circuits.

Further, since the settings can be made again by rewriting the contents of the memory at any time, it is possible to easily deal with changes in the amount of received light.

(Example) Hereinafter, a method for controlling the amount of light received by a light receiving element of the present invention will be described with reference to the drawings. In the figure, the same components as those shown in FIG. 1 will be described with the same reference numerals.

First, one light emitting element array 10, an optical circuit te, and a manuscript 28
FIG. 2 schematically shows an example of the arrangement of the light receiving element 18. The light from the light emitting element is connected as a spot on the document 28 by the optical circuit 16, and the reflected light is transmitted to the light receiving element 1.
8 and is configured to be able to read information on the document 28.

FIG. 3 is a diagram specifically showing a control system for explaining the control method of the present invention.

First, the case of storing the correction voltage in the memory 22 will be explained. Connect the switch 30 to the reference light emission voltage Vc side,
0 where the power supply voltage applied to the light emitting element array lO is kept constant.
Next, a signal from the control circuit 14 connects the first switch of the light emitting element driving circuit 12 including a switch circuit to cause the first light emitting element, for example, a light emitting diode, to emit light.

The reference document is read by this light emission, and the reflected light is detected by a light receiving element 18 such as a photodiode. This detected current is changed into a detected voltage Vd by a current-voltage conversion circuit 32.

At this time, if the detected voltage from the light receiving element 1B when there is no variation in the amount of light received due to the constituent components of the optical reading device is taken as the reference output voltage, then when reading this reference document, it is not affected by such variations. The detection voltage corresponding to the amount of received light deviates from the reference output voltage.

This detected voltage Vd is converted into a correction voltage VL by an arithmetic circuit 34. This conversion is performed, for example, according to the conversion characteristics shown in the straight lines in Figure 4. In the figure, the horizontal axis represents the detection voltage Vd, and the vertical axis represents the correction voltage VL, which in this case is applied to the light emitting element. The voltage to be measured is shown below. According to this conversion characteristic, when the amount of light emitted from the light emitting diode 10 is small and the dot is dark, and therefore the detected voltage value Vd obtained from the photodiode 18 is small, the light emitting voltage to be applied to one light emitting diode is greatly increased. On the other hand, if the dot becomes too bright due to the large amount of light emitted from the light emitting diode 10 and the voltage value d detected by the photodiode 18 is large, the voltage applied to the light emitting diode 10 is increased. It acts to lower the required light emission voltage and reduce the amount of light emitted by the light emitting diode.

Note that the slope of the straight line I that gives this conversion characteristic changes depending on the characteristics of the light emitting element used.

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LE Todoroki/n Digitized by alternating circuit 2B, memory 2
It is stored at address 1 of 2 as a VLI. This address is specified by the control circuit 14.

Next, the control circuit 14 switches the light emitting element drive circuit 12 to the second switch, and the second light emitting diode (
The dot) is caused to emit light and stored as the correction voltage VL2 in the corresponding address 2 of the memory 22 in the same manner as described above. Similarly, for the third, fourth, . . . fist and all light emitting diodes (dots), a correction voltage of a magnitude that increases or decreases in the opposite direction to the increase or decrease direction of the detection voltage Vd is applied one-to-one to a predetermined address in the memory 22. They are stored sequentially due to the relationship.

The relationships as described above are shown in FIGS. 5(A) and (B).
Figure 5 (A) shows the relationship between the dot number (horizontal axis) and the detected voltage (vertical axis), and Figure 5 (B) shows the relationship between the dot number (horizontal axis) and the correction voltage VL. It shows a relationship. In this case, the variations shown in FIG. 5(A) are caused by all the circuits in the reader system, including variations in the amount of light emitted from each dot of the light emitting element array, the influence of optical system circuits such as lenses, and the influence of light receiving system circuits. Therefore, according to the method according to the present invention, it is possible to reduce the variation in the amount of received light caused by all the circuits.

Next, a case in which pattern information actually drawn on a document is read will be briefly explained.

In FIG. 3, the switch 30 is set to the voltage VL side. A signal from the control circuit 14 causes the light emitting element drive circuit 1 to
2, the first dot Dl of the light emitting element array IO is selected. At the same time, the corrected voltage value vLl at address 1 of the memory 22 is read out and converted into an analog value by the D/A conversion circuit 24. The current is amplified by the amplifier circuit 3B, and this value VLI is applied to the power supply voltage VLI at the first dot D1.
LI, that is, the 0th-order second driver (D2) applied as the light-emission voltage is selected, and the light-emission voltage VL2 is similarly applied to it. The above operation is repeated for each dot in the same way, and by detecting the reflected light on the document surface,
It is possible to read pattern information drawn on manuscripts.

(Effects of the Invention) As described above, according to the present invention, it is possible to reduce variations in the amount of light received by all the circuits of the optical reading device including the light emitting element array, the optical system circuit, the light receiving system circuit, and the like.

Further, since the settings can be made again by rewriting the contents of the memory at any time, it is possible to easily deal with changes in the amount of received light.

[Brief explanation of the drawing]

FIG. 1 is a block diagram for explaining the principle of a method for controlling the amount of light received by a light receiving element according to the present invention. Fig. 2 is a diagram used to explain the present invention, Fig. 3 is a diagram showing a control system for carrying out the method of this invention, and Fig. 4 is a diagram showing the detection voltage of the photodiode and correction used to explain the invention. Figure 5 (A) and (B) are diagrams showing the relationship between the dots of the light emitting element array and the detection voltage and correction voltage of the photodiode, respectively, used to explain the present invention. . DESCRIPTION OF SYMBOLS 10... Light emitting element array, 12... Light emitting element drive circuit 14... Control circuit, 16... Optical system circuit 1B... Light receiving element for reading, 20... Light receiving system circuit 22... Memory, 24...D/A conversion circuit 26...A/D conversion circuit, 28...Original 30
...Switch, 32...Current voltage conversion circuit 34...Arithmetic circuit, 36...Amplification circuit DI
, 02. ...Fist...Light-emitting diode. Patent applicant: Oki Electric Industry Co., Ltd. Figure 1 Figure 2 Figure 2B: Soot Figure 5 Dot fleas

Claims (1)

[Scope of Claims] When controlling the amount of light received by a reading light receiving element when document information is read by a reading light receiving element using light from a light emitting element array in an optical reading device, the light emitting element is controlled at a reference light emitting voltage. The information on the reference document is detected by the light-receiving element using the emitted light.
A correction voltage is formed by correcting the amount of deviation of the detection voltage of the light-receiving element from a reference output voltage of the light-receiving element, and the correction voltage is stored in the address position of the light-emitting element in a memory, and when reading a normal document. A method for controlling the amount of light received by a light receiving element, comprising reading out a correction voltage stored in a corresponding address position of a memory for each light emitting element, and controlling the light emission voltage of the light emitting element in accordance with the correction voltage.