JP2000351232A - Quantity-of-light control system in multibeam drawing/ recording apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain desired quantity of light on a drawing surface by perfectly correcting the irregularity caused by the individual difference between LEDs or the elements in a quantity-of-light control part. SOLUTION: A quantity-of-light control system 50 has a light emitting circuit for turning on drawing LEDs 3 and a quantity-of-light control part 2 for controlling the quantity of light of a light emitting diode and the quantity-of-light control part 2 is equipped with a light emitting current control means for changing the current flowing to the light emitting circuit corresponding to an applied voltage and further equipped with a means for correcting the individual difference between the drawing LEDs 3 to convert quantity-of-light indicating data for obtaining desired quantity of light inputted from the outside to 'light emitting current indicating data' indicating a current necessary for emitting light from all of the drawing LEDs 3 in desired quantity and a means for correcting the individual difference of the quantity-of-light control part to convert the light emitting current indicating data to 'applied voltage data' indicating voltage necessary for allowing a desired light emitting current to flow.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting diode (hereinafter, referred to as an LED) in a multi-beam drawing / recording apparatus.
The light amount control system.

[0002]

2. Description of the Related Art This type of multi-beam image recording apparatus is
For example, it is disclosed in JP-A-8-310195.
In the device disclosed in this publication, a plurality of LEDs having predetermined peak wavelengths of emission light are used to irradiate a beam onto a screen of a photosensitive material, and the photosensitive material is relatively moved with respect to the LED group. Thus, a two-dimensional image is drawn.

In such a multi-beam image recording apparatus, the individual characteristics of the LEDs vary, so that even if the same amount of current is applied, the light amount of the beam emitted from each LED varies, resulting in a drawback on the drawing surface. This makes it impossible to draw a highly accurate and uniform line. Therefore, it is necessary to control the amount of light of each LED according to the characteristics of each LED.
Therefore, conventionally, a light amount control unit for controlling the light amount is provided for each LED, and the light amount control for emitting a desired light amount has been performed.

[0004] However, other elements provided inside a light quantity control unit for controlling the light quantity of the LED and used for converting a voltage output from a D / A converter or a D / A converter into a current. And the like, there is an individual difference, and the individual light amount also causes variation in the light amount of the beam emitted from the LED. Therefore, when performing high-precision drawing using a multi-beam recording device, not only variations in light amount due to individual characteristics of each LED but also variations in light amount due to characteristics of various elements in each light amount control unit are considered. It is necessary to control the light amount.

[0005]

SUMMARY OF THE INVENTION In view of the above circumstances, the present invention corrects all variations caused by individual differences between LEDs and light quantity control units, and obtains a desired light quantity at the LED light emission stage. It is an object of the present invention to provide a light amount control system in a multi-beam image recording apparatus that can perform the above operation.

[0006]

Therefore, a light amount control system in a multi-beam image recording apparatus according to the present invention comprises a light emitting circuit for turning on a drawing LED and a light amount for controlling a light emitting amount of a light emitting diode. A control unit. The light amount control unit includes a light emission current control unit that changes a current flowing in the light emitting circuit in accordance with an applied voltage. The light amount control system according to the present invention further includes light amount instruction data for obtaining a desired light amount input from outside,
Means for converting the individual differences of the drawing LEDs into “light emission current instruction data” for instructing a current necessary to emit a desired light amount from all the drawing LEDs, and controlling the light emission current instruction data for light amount control Means for correcting the individual difference of the unit and converting the voltage into “applied voltage data” indicating a voltage necessary for flowing a desired light emission current.

More specifically, the light-emission current control means is a photocoupler comprising a light-emitting element that emits a light amount corresponding to the applied voltage, and a photoelectric conversion element that generates a control current corresponding to the light amount. It is desirable.

With these configurations, the drawing LED
In addition, since the correction of the variation of the light amount due to the individual difference of the light amount control unit is performed inside the light amount control unit, the drawing LED can emit the light amount as instructed, and the light amount from the outside of the apparatus can be controlled. Instruction becomes easy.

[0009]

FIG. 1 is a diagram showing a light quantity control system 50 according to an embodiment of the present invention. Light intensity control system 5
0 is a main CPU 1, a light amount control unit 2, a drawing LED 3,
An LED power supply 4 and a driver 5 are provided. Main CP
U1 is an element for instructing each circuit of the apparatus and controlling the entire apparatus. In the present embodiment, U1 outputs data for controlling blinking of the drawing LED 3 to the driver 5 based on drawing information input from outside the apparatus. Then, it outputs light amount instruction data to the light amount control unit 2.

The driver 5 controls the drawing LED 3 and the LE according to the data for controlling the blinking sent from the main CPU 1.
A circuit (hereinafter referred to as a light emitting circuit) connecting to the D power supply 4 is connected / disconnected. That is, when the driver 5 connects the light emitting circuit, a current flows from the LED power supply 4 to the drawing LED 3, and the drawing LED 3 is turned on. However, when the driver 5 cuts off the light emitting circuit, the LED power supply 4
3, the current stops flowing, and the drawing LED 3 is turned off.

The light amount control unit 2 comprises a control unit CPU 21, a non-volatile memory 22, a D / A converter 23, an amplifier 24, and a photocoupler 25. Controlling. In this embodiment, since the driver 5 and the light amount control unit 2 each control one drawing LED 3, the light amount control system 50 is provided with the driver 5 and the light amount control unit 2 by the number of LEDs. Will be.

The photocoupler 25 includes a control LED 26 and a photoelectric conversion element 27.
In the / A converter 23, a collector and an emitter provided in the photoelectric conversion element 27 are connected to a light emitting circuit, respectively. The control LED 26 emits a light amount corresponding to an applied voltage (hereinafter, referred to as a control voltage), and a photoelectric conversion element 27 disposed oppositely supplies a current corresponding to the emitted light amount (hereinafter, referred to as a control current). Flows, and the drawing LED 3
Light is emitted in an amount corresponding to the control current. That is, when the driver 5 is connected to the light emitting circuit, the control current flowing through the drawing LED 3 can be controlled by changing the control voltage applied to the control LED 26 of the photocoupler 25,
The amount of emitted light can be changed.

In this light amount control system 50, correction is performed to eliminate variations in light amount caused by individual differences between the drawing LEDs 3 and each light amount control unit 2, and as a result, the light amount instruction data and the actual light emission amount match. I want to be in a relationship.

When a desired light amount is input to the apparatus at the time of drawing, the main CPU 1 transmits light amount instruction data corresponding to the desired light amount to the control unit CPU 21 in the light amount control unit 2. The control unit CPU 21 first performs an operation (hereinafter, referred to as a first operation) for correcting a variation in light amount due to the characteristics of each drawing LED 3. The control current and light amount flowing for a certain drawing LED 3 have a relationship as shown in FIG.
Although the relationship shown in FIG. 2 is applied to any of the drawing LEDs 3, the actual amount of light obtained by the supplied current value differs depending on the characteristics of each drawing LED 3.
Therefore, in the first operation, the light amount instruction data is stored in each drawing LE.
On a conversion table having a light quantity / current characteristic curve for D3 (FIG. 2), the data is converted into data (hereinafter referred to as light emission current instruction data) corresponding to a control current value required to obtain a desired light quantity.

For this reason, the current value passed through each of the drawing LEDs 3 and the irradiated light amount are measured in advance, and a conversion table based on the light amount / current characteristic curve created based on the measurement result is stored in the nonvolatile memory 22. deep. FIG. 3 shows a conversion table having a light quantity / current characteristic curve for a certain drawing LED 3, and the vertical axis shows light quantity instruction data.
The horizontal axis indicates the emission current instruction data. Assuming that the maximum value of the current used for each drawing LED 3 is 24 mA, which is 80% of the absolute rating, in order to ensure safety when using the recording device, the current instruction data “FF” is 24 mA and the current instruction data “00” is the same. "Represents 0 mA.

The control unit CPU 21 performs the first operation using the conversion table created for each drawing LED 3, thereby correcting variations caused by individual differences of each drawing LED 3. . That is,
The light intensity instruction data is converted into light emission current instruction data for accurately instructing a value of a control current for each drawing LED 3 necessary for obtaining a desired light intensity.

If the light quantity / current characteristic curve can be represented by a relational expression, each drawing LE
The first operation can be performed by using the relational expression instead of the conversion table created in advance for each D3.

When the emission current instruction data is created by the first operation, the control unit CPU 21 then determines the individual differences of the elements such as the D / A converter 23 and the photocoupler 25, that is, the individual differences of the light amount control units 2. An operation (hereinafter, referred to as a second operation) for correcting the resulting variation in the amount of light is performed.

As shown in FIG. 4, the value of the control current flowing through the drawing LED 3 and the value of the control voltage generated in the light amount control unit 2 have a substantially linear relationship. However, as described above, since each light amount control unit 2 has an individual difference, it is necessary for the control current indicated by the emission current instruction data created by the first operation to flow to the drawing LED 3 accurately. The value of the control voltage differs for each light amount control unit 2. Therefore, in the second operation, the light emission current instruction data for each of the drawing LEDs 3 is transferred to the drawing LE
D3 is converted into applied voltage data indicating a value of a control voltage required to flow a desired control current.

FIG. 5 shows a state of the second operation in the control unit CPU 21, and FIG. 5-1 shows a relationship between a control current flowing through the drawing LED 3 and applied voltage data indicating a value of the control voltage. FIG. 5-2 shows the relationship between the emission current instruction data and the applied voltage data. Control unit CPU2
In order to enable the second work to be performed, each drawing L
When the applied voltage data input to the light amount control unit 2 when the current of the maximum value (24 mA) flows for each of the EDs 3 and the current flowing to the drawing LED 3 are gradually reduced thereafter, and become the minimum value (0 mA) And the applied voltage data input to the light amount control unit 2 are stored in the nonvolatile memory 22.

Here, assuming that the applied voltage data at 0 mA is applied voltage data α and the applied voltage data at 24 mA is applied voltage data β, the range V between the applied voltage data α and β is LED 3 for drawing that is in charge of unit 2
The range of the control voltage generated for controlling the amount of light of the control signal is shown.

Here, the values of the applied voltage data α and the applied voltage data β of each light quantity control unit 2 are shifted to the left and right by the characteristics of each light quantity control unit, so that the range V differs for each light quantity control unit 2. However, the light emission current instruction data “00” created in the first operation has 0 mA, and the same data “FF”
Is data corresponding to 24 mA, so that the emission current instruction data “00” can always be converted into the applied voltage data α and the emission current instruction data “FF” can be converted into the applied voltage data β in a one-to-one manner. Further, since the control current and the control voltage indicated by the applied voltage data have a linear relationship (FIG. 5A), if two points on the straight line (here, the applied voltage data α and the applied voltage data β) are known, Even if the emission current instruction data takes another value, it is possible to convert the data into the applied voltage data on a one-to-one basis within the range V.

By the second operation, it is possible to correct the variation in the light amount caused by the fact that a desired control current does not flow through the drawing LED 3 due to the individual difference of the light amount control unit 2. Further, since the applied voltage data α and the applied voltage data β are stored in the nonvolatile memory 22 of each light quantity control unit 2 as described above, there is no need to worry about individual differences of each light quantity control unit 2, and the light quantity control The section 2 can be made compatible.

When the second operation is completed, the control unit CPU 21 transmits the generated applied voltage data to the D / A converter 23. The D / A converter 23 performs digital / analog conversion on the obtained applied voltage data to convert the applied voltage data into a control voltage corresponding to the value indicated by the applied voltage data on a one-to-one basis.

A control current controlled by the control voltage via the photocoupler 25 controls the amount of light emitted from the drawing LED 3 and causes the drawing LED 3 to emit the same amount of light as indicated by the light amount instruction data. become.

FIG. 6 summarizes the data flow resulting from the above conversion work. That is, the light amount instruction data transmitted from the main CPU 1 is replaced by light emission current instruction data in consideration of the characteristics of the corresponding drawing LED 3 by the first operation of the control unit CPU 21, and the light emission current instruction data is By two operations, the voltage is converted into applied voltage data in consideration of the individual difference of the light amount control unit.
The applied voltage data is converted into a corresponding control voltage by digital / analog conversion using the D / A converter 23. The photocoupler 25 generates a control current based on the applied control voltage and supplies the control current to the drawing LED 3. With the above operation, the desired light amount, that is, the light amount indicated by the light amount instruction data is emitted from the drawing LED 3.

FIG. 7 is a flow chart showing a process of controlling the light quantity in the light quantity control section 2. L for drawing
The light quantity control of the beam emitted from the ED 3 is performed as follows. First, the light amount instruction data is sent to the main CPU.
Then, it is determined whether or not transmission has been performed from No. 1 (S1).

When the light amount control unit 2 receives the light amount instruction data (YES: S1), the control unit CPU 21 performs the first and second operations described above (S2), and applies the applied voltage via the emission current instruction data. Create data. The D / A converter 23 outputs a control voltage corresponding to the created applied voltage data (S3). The control voltage is applied to the control LED 26 in the photocoupler 25 via the amplifier 24,
The photoelectric conversion element 27 in the photocoupler 25 generates a control current corresponding to the control voltage (S4).

If the light-emitting circuit is connected by the driver 5, the above-described control current for producing a desired light amount flows through the drawing LED 3, and the light amount is accurately controlled.

The above is the description of the embodiment of the present invention. Note that each drawing LED 3, a conversion table having a light amount / current characteristic curve different depending on the light amount control unit 2, and the applied voltage data α and the applied voltage data β are adjusted at the time of shipment adjustment and when each drawing LED and the light amount control unit are replaced. Sometimes you need to measure and prepare.

In this embodiment, the drawing LED 3 is used.
Although the photocoupler 25 is used for controlling the light amount, the present invention is not limited to this, and an element having the same function, for example, a transistor can also be used. Even when a transistor is used, individual differences in the light amount control unit 2 occur due to variations in element characteristics. Therefore, by performing a conversion operation in the same manner as in the present embodiment, it is possible to obtain a desired amount of light emitted from the drawing LED 3. Light quantity.

[0032]

As described above, the light amount instruction data given from the CPU is transmitted to the drawing LED in each light amount control unit.
In addition, by performing the correction in consideration of the individual difference of the light amount control unit, the light amount as indicated by the light amount instruction data can be obtained in the light emission stage of the drawing LED.

[Brief description of the drawings]

FIG. 1 is a diagram showing a circuit of a light amount control system according to an embodiment.

FIG. 2 is a graph showing a relationship between a control current flowing through a certain LED and a light emission amount of the LED.

FIG. 3 is a conversion table having a light quantity / current characteristic curve of a certain LED;

FIG. 4 is a graph showing a relationship between a control current flowing through an LED and a control voltage generated in a light amount control unit.

FIG. 5 is a diagram illustrating a state of a second operation of the embodiment.

FIG. 6 is a diagram showing a data flow according to the embodiment of the present invention.

FIG. 7 is a flowchart showing a process of controlling the light amount according to the embodiment of the present invention.

[Description of Signs] 1 Main CPU 2 Light intensity control unit 3 Drawing LED 4 LED power supply 5 Driver 21 Control unit CPU 22 Non-volatile memory 23 D / A converter 24 Amplifier 25 Photocoupler 50 Light intensity control system

Claims (2)

[Claims] 1. A multi-beam image recording apparatus having a plurality of light emitting diodes for irradiating a beam for exposing a surface to be scanned, a light emitting circuit for causing the light emitting diodes to emit light, and a light emitting circuit for controlling a light emitting amount of the light emitting diodes. A light amount control unit for changing a current of the light emitting circuit in accordance with an applied voltage; and a light amount for obtaining a desired light amount input from outside. Means for converting the instruction data into light emission current instruction data necessary to emit a desired light amount by correcting the individual difference of the light emitting diode; and correcting the light emission current instruction data for the individual difference of the light amount control unit. And means for converting the applied voltage data to the light-emitting current control means necessary for causing a desired light-emitting current to flow. Light control system in the apparatus. 2. The light-emitting device according to claim 1, wherein the light-emitting current control unit includes a light-emitting element that emits a light amount corresponding to the applied voltage, and a photoelectric conversion element that generates the current corresponding to the light amount. Item 2. A light amount control system in the multi-beam image recording apparatus according to Item 1.