JP2000355121A - Method for controlling light quantity by using vf value in multi-beam plotting/recording apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light quantity control system and a light quantity control method capable of controlling a light quantity by using a VF value which is a common value for indicating a predetermined light quantity to any multi-beam plotting/recording apparatus. SOLUTION: In a multi-beam plotting/recording apparatus, a VF value-light quantity characteristic curve is formed by each LED based on an actual measured result. Each of the VF value-light quantity characteristic curve is divided into areas each in which a relationship between the VF value and light quantity can be changed in a linear fashion in an inputted tolerance range and reference light quantity data for designating the light quantity data obtained on an plotting screen to be a reference light quantity. When a VF value corresponding to a desired light quantity is inputted at the plotting time, desired light quantity designation data for designating the light quantity obtained on the plotting screen to be the desired light quantity is formed based on the reference light quantity data, then the light quantity is controlled in accordance with the desired light quantity designation data.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a light quantity of a light emitting diode (hereinafter, referred to as an LED) in a multi-beam image recording apparatus.

[0002]

2. Description of the Related Art Conventionally, when fabricating a circuit board, one is required.
2. Description of the Related Art A laser image recording apparatus that forms a precise circuit pattern on a photosensitive material by scanning a laser on the photosensitive material is used. Since the laser image recording apparatus has one light source, an optical filter (variable filter) that can change the transmittance is arranged near the light source, and the user can obtain a desired light amount at the time of drawing. By inputting an appropriate VF value (set value of the transmittance of the variable filter) from outside, the light amount is controlled by changing the transmittance of the variable filter.

[0003] A multi-beam image recording apparatus using a plurality of LEDs arranged in a light source section has also been used for producing a circuit board. Using LED,
The multi-beam image recording device displays L on the screen of the photosensitive material.
A circuit pattern is created by irradiating a beam emitted from the ED and moving the photosensitive material relative to the LED group.

[0004] Such a multi-beam image recording apparatus using a plurality of LEDs does not have a variable filter. However, if a desired light amount can be specified by inputting a VF value, a user can use the variable filter. There is an advantage that the light amount control can be performed using the same data and data as when the light amount control is performed.

Therefore, the VF value corresponding to the desired light quantity is set to LE
When input is made to the multi-beam image recording apparatus using D, the light amount control is performed by changing the voltage applied from the power supply to each LED according to the input VF value.

However, even if the power supply voltage is changed to a certain value in accordance with the input VF value, each LED has its own characteristics due to individual differences of LEDs and variations in characteristics of elements in the light amount control circuit. The way of changing the light quantity is different. In other words, there is a problem that the amount of light emitted from all the LEDs does not reach the desired amount even though the VF value corresponding to the desired amount of light is input.

In order to solve the above problems, for example, a proposal by the present applicant (filing date: June 11, 1999, inventor: Takashi Okuyama, title of invention: light quantity control in a multi-beam drawing / recording apparatus) System).

[0008] According to the light quantity control system according to the above proposal, the amount of light of the beam emitted from the LED due to individual differences between the LEDs and the characteristics of the elements constituting the light quantity control circuit is stored in the internal nonvolatile memory. Correction data for correcting the variation is stored in advance. Therefore, at the time of drawing, the CPU for light amount control reads out the correction data from the non-volatile memory, creates light amount instruction data for instructing the LED to emit a desired light amount, and according to the light amount instruction data,
Each light amount control circuit can perform light amount control, and the light amount of the beam emitted from the LED can be set to a desired light amount.

In this light amount control system, an LED
The amount of light emitted from the LED is controlled by changing the current flowing through the LED.
The problem of light quantity control by an applied voltage such as a change in the light emission quantity from the ED is also solved. As described above, in the multi-beam drawing recording apparatus equipped with the light amount control system that controls the light amount by changing the current flowing through the LED, the light amount is controlled by changing the LED current according to the input VF value. It will be.

[0010] However, even if various proposals including the above-mentioned proposal are adopted and the light quantity of the beam emitted from the LED can be set to a desired light quantity corresponding to the input VF value, Due to structural errors such as LED mounting errors or individual differences such as the optical system through which the beam emitted from the LED passes through to the drawing surface, the amount of light actually obtained on the drawing surface is the desired light amount. The problem remains that it does not occur.

[0011]

SUMMARY OF THE INVENTION In view of the above circumstances, the present invention provides a multi-beam drawing / recording apparatus capable of accurately obtaining a desired light amount indicated by an input VF value on a drawing surface. An object is to provide a light amount control method.

[0012]

For this purpose, a plurality of LEDs are provided.
And a light quantity control circuit of the same number as the LEDs, and having data for correcting variations in light quantity caused by these individual differences. , The VF value / light amount characteristic curve is created for each LED, and the VF value and the light amount change linearly within an arbitrarily set allowable range. Divide into available areas. In each area, based on a measurement result obtained by actually turning on an LED, light amount instruction data (hereinafter referred to as reference light amount data) for setting a light amount obtained on a drawing surface to a light amount corresponding to a reference VF value. Create).

At the time of drawing, by multiplying the reference light amount data by the ratio of the VF value corresponding to the input desired light amount and the reference VF value, the light amount obtained on the drawing surface can be made the desired light amount. Light amount instruction data (hereinafter referred to as desired light amount instruction data) is created. Light amount control is performed based on the desired light amount instruction data so that a desired light amount is always obtained on the drawing surface.

According to this light amount control method, the light amount on the drawing surface of the beam emitted from the LED when the VF value is input coincides with the desired light amount. Can be controlled to obtain a desired light amount.

More specifically, it is desirable that the reference VF value is an intermediate value of each area. In the present invention, the reference light amount data is X, the VF value input at the time of drawing is VF _n , and the reference VF value is VF _n . Assuming that the VF value is VF _ref , the desired light amount instruction data D can be expressed by D = X · (VF _n / VF _ref ).

In the light amount control method according to the present invention, the light amount is controlled by changing the current flowing through the LED according to the input VF value according to the above proposal.

[0017]

Embodiments of the present invention will be described below. FIG. 1 is a diagram showing a light amount control system 10. The light quantity control system 10 includes a light quantity control CPU 1, a light quantity control circuit 3, a nonvolatile memory 2, an LED 4, an LED power supply 5,
It comprises a drive circuit 6 and a light amount detection unit 20. The light amount detection unit 20 includes a photo sensor 7, an amplification circuit 8, an A / D
It comprises a converter 9. Incidentally, since the light amount control circuit 3 and the drive circuit 6 are connected to one LED 4 for each circuit, the number of the mounted LEDs 4 is provided in an actual device.

Since the non-volatile memory 2 varies in light quantity for each LED 4 due to the characteristics of the LED 4 and the elements constituting the light quantity control circuit 3, corrections made to eliminate the variation in light quantity due to these properties are provided. Data is stored in advance for the number of LEDs 4 mounted on the apparatus.

When data representing a desired light amount is transmitted from a main CPU (not shown), the light amount control CPU 1 reads out the correction data from the nonvolatile memory 2 and instructs to emit the desired light amount. Light amount instruction data is created for all four LEDs and transmitted to each light amount control circuit 3.

The light amount control circuit 3 includes a connected LED.
Reference numeral 4 plays a role of controlling the light amount so as to emit a desired light amount. That is, the light amount control circuit 3 performs the LE control according to the light amount instruction data transmitted from the light amount control CPU 1.
By changing the value of the current flowing through D4, the LED 4 emits a desired amount of light.

The drive circuit 6 includes a main CP (not shown).
In accordance with the drawing data from U, the circuit provided with the LEDs 4 is intermittently turned on and off to blink each LED 4.

The photo sensor 7 of the light amount detecting section 20 is composed of a photoelectric conversion element such as a phototransistor or a photodiode, and is provided on a movable table (not shown) on which a photosensitive material is arranged at the time of drawing. It is provided in a position that does not hinder the operation. When detecting the amount of light, the light emitted from the LED 4 is transmitted through an optical system or the like provided between the drawing surface by relatively moving the light source unit provided with the LED 4 and the movable table. Then, the light can be received by the photo sensor 7. That is, the photo sensor 7 can receive the same light amount as the light amount obtained on the drawing surface at the time of drawing, convert the light amount into a current, and detect it.

FIG. 2 is a graph showing the relationship between the input VF value and the amount of light actually obtained on the drawing surface for a specific LED 4 provided in a certain multi-beam drawing recording apparatus. The horizontal axis represents the input VF value, and the vertical axis represents the amount of light obtained on the drawing surface. Here, the VF value 0% corresponds to the light amount 0, and the VF value 100% corresponds to the maximum light amount that the LED 4 of the device can emit.

As shown in FIG. 2, the relationship between the two
In many cases, the beam does not have a linear relationship due to an individual difference of an optical system that is transmitted before the beam irradiated from the optical system is exposed to the drawing surface. In addition, since the above-mentioned causes vary in degree depending on the mounting state of the used LEDs 4 and each optical system, the amount of light actually obtained on the drawing surface by inputting a certain VF value is constant for all the LEDs 4. However, it is different for each LED 4. Therefore, when a VF value is input from the outside in advance, the amount of light actually obtained on the drawing surface is measured, and each LE is calculated based on the measurement result.
A VF value / light amount characteristic curve of D4 is created. In addition, VF value /
The operations described below, including the operation of creating the light amount characteristic curve, are all performed by the light amount control CPU 1 except where otherwise noted.

When an individual characteristic curve is created for each LED 4, an approximation is taken based on the VF value / light amount characteristic curve. When the VF value is changed, the light amount becomes linear within an allowable range arbitrarily set by the user. It is divided into areas that can change (hereinafter, referred to as linear areas). FIG.
3 is a graph showing a state in which the VF value / light amount characteristic curve of the LED 4 having the VF value / light amount characteristic shown in FIG. 2 is divided into linear areas. In FIG. 3, a specific LED
The VF value / light amount characteristic curve for the two linear areas (area A: 0% to 4%) within a certain allowable range.
9%, area B: 50% to 100%).

Since the number of linear areas changes depending on the VF value / light amount characteristic, it differs for each LED. Also, since the number of linear areas changes depending on the allowable range to be set, if the allowable range when creating the linear area of each LED is set small, the number of linear areas increases,
The error of the light amount becomes small. On the other hand, if the allowable range is set large, the setting work can be speeded up as the number of linear areas decreases. Therefore, it is desirable to set the allowable range according to the needs of the user.

After dividing the VF value / light amount characteristic curve into linear areas, a VF value as a reference (hereinafter referred to as a reference VF value) and a light amount corresponding to the reference VF value (hereinafter referred to as a reference light amount) are provided for each area. ) Is determined, and when a reference VF value is input, reference light amount data is generated such that the light amount obtained on the drawing surface becomes the reference light amount. Hereinafter, a specific LED 4 divided into areas as shown in FIG. 3 will be described.

The reference VF value of the area A is set to 25% which is a VF value corresponding to the middle of the area. Here, the reference VF
The value is set to the VF value corresponding to the middle of the area. For example, when the VF value corresponding to one end of the area is set as the reference VF value, if the VF value at the other end is input, the desired light amount instruction data is created. This is because when doing so, the error increases.

The CPU 1 for controlling the light amount has a reference VF value of 25%.
_Is determined as L _ref based on the graph of FIG. 3, and the light amount instruction data x corresponding to the reference light amount L _ref is determined.
Is transmitted to the light quantity control circuit 3. Light intensity control circuit 3
Controls the light emission amount of the specific LED 4 according to the light amount instruction data x.

The light quantity instruction data x created here is data for instructing the specific LED 4 to output the reference light quantity L _ref , but the light transmitted from the LED until the beam is exposed on the drawing surface. This data does not take into account any variation in light amount due to individual differences of the system (not shown). Therefore, the light amount of the beam immediately after irradiation from the specific LED 4 is exactly the reference light amount L.
It has a _ref, but the amount of light obtained on the drawing surface is not necessarily the reference light quantity L _ref.

Light emitted from a specific LED 4 and transmitted through an optical system or the like provided between the drawing surface and the drawing surface is converted by the photo sensor 7 into a corresponding current. The generated current is amplified by the amplifier circuit 8, converted into a digital signal by the A / D converter 9, and fed back to the light amount control CPU 1. Light amount control CPU1 is the amount instruction data x, by multiplying the coefficients created in the amount of light and the reference light quantity L _ref measurement results, in particular LED4 area A, to create a reference light quantity data X _A.

[0032] Based on the actual measurement result, reference light quantity data X _A created, unlike light quantity instruction data x, the optical system in until drawing surface with specific LED4 characteristics and device structural of For this reason, the data is considered so as not to cause a variation in the light amount on the drawing surface, and the data is such that a desired light amount can be obtained on the drawing surface.

The CPU 1 for controlling the light quantity controls the reference light quantity data X
_{With the} light amount control based on _A , the specific LED 4 is turned on again, and it is determined whether or not the light amount actually obtained on the drawing surface matches the input reference light amount. If the measured amount of light does not match the reference amount of light is again carried out the task of creating a reference light quantity data, if the measured light amount is equal to the reference amount of light, specific reference light quantity data X _A created Reference light amount L in area A of LED 4
_ref , that is, light amount instruction data corresponding to the reference VF value of 25%.

Similarly, for area B, the reference VF value is determined to be 75%, which is the intermediate value of the area, and the corresponding reference light amount is determined based on the graph of FIG. Then, to create a reference light quantity data X _B based on the result of actual measurement.

As described above, the CPU for controlling the amount of light
The light amount instruction data created in step 1 is used to correct individual differences of elements and the like in the circuit by the correction data.
The light quantity of the beam emitted from the LED 4 has a linear relationship. The VF value naturally changes linearly with the light amount in the linear area. From these relationships, the VF input at the time of drawing from the reference VF value
It can be seen that the rate of increase to the value is equal to the rate of increase from the reference light quantity data to the desired light quantity instruction data.

That is, the desired light amount instruction data is set to D, the reference light amount data is set to X, and the VF value input at the time of drawing is set to V
Assuming that F _n and the reference VF value are VF _ref , D: X = VF _n : VF _ref (1) By converting the expression (1) into the following expression, D = X ・ (VF _n / VF _ref ) (2), a calculation expression (2) for obtaining the desired light amount instruction data D can be created.

Therefore, if the VF value input at the time of drawing belongs to the area A for the specific LED 4, the desired light amount instruction data is obtained from the formula (2) as follows: D = X _A · (VF _n / 25) it can, VF value input at the time of drawing is desired quantity instruction data if it belongs to the area B can likewise be obtained by _{D = X B · (VF n} / 75).

Since the desired light amount instruction data D created by the calculation formula (2) is created based on the reference light amount data X, the characteristics of the optical system between the specific LED 4 and the drawing surface and the device For structural reasons, the data is considered so as not to cause a variation in the amount of light on the drawing surface, and the data has a desired light amount on the drawing surface. Further, since the reference light amount data X is a fixed value which is determined in advance for each linear area of each LED 4, the desired light amount instruction data D depends on the ratio formed by the reference VF value and the input VF value. In other words, it is possible to control the amount of light obtained on the drawing surface to a desired amount by using the VF value.

FIG. 4 shows a specific LED based on the above operation.
4 is a table summarizing area A and area B. This table is stored in the nonvolatile memory 2 connected to the light amount control CPU 1 as data relating to the specific LED 4. With respect to the other LEDs 4, the same operation is performed for each of the divided areas, and a table similar to that of FIG.
The data relating to the ED 4 is stored in the nonvolatile memory 2.

At the time of drawing, a VF value corresponding to a desired light quantity is input. Then, the CPU 1 for controlling the amount of light
For each case, it is determined based on the data stored in the nonvolatile memory 2 to which linear area the input VF value belongs. Then, data (reference light amount data and ratio in FIG. 4) relating to the linear area determined to belong to the input VF value is read out, and the calculation formula (2) is executed to obtain the desired light amount instruction data of each LED 4. It is created and transmitted to each light amount control circuit 3.

Each light amount control circuit 3 controls the light emission amount of the connected LED 4 according to the transmitted desired light amount instruction data. As a result, the amount of light when the beam emitted from the LED 4 is exposed on the drawing surface depends on the input VF
A light amount corresponding to the value, that is, a desired light amount is obtained.

The above is the present embodiment of the present invention. still,
The above-mentioned work is basically performed at the time of product shipment or LE
It is sufficient to use a new LED, such as when replacing D, but if it is used for a long period of time, the LED and other elements in the device will deteriorate, so higher-precision drawing will always be possible. To do this, it is desirable to periodically perform the above-described operation and update the data stored in the nonvolatile memory.

[0043]

As described above, the VF value / light amount characteristic curve of each LED is divided into areas in which the VF value and the actual light amount can change linearly within a certain allowable range, and the VF value and the light amount are plotted. When a VF value corresponding to a desired light amount is input by associating the light amount instruction data with an LED, an LED
The amount of light on the drawing surface of the beam irradiated from can be matched with the desired amount of light.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a light amount control system according to an embodiment.

FIG. 2 is a diagram showing a VF value / light amount characteristic curve of a specific LED.

FIG. 3 is a diagram in which a VF value / light amount characteristic curve of FIG. 2 is divided by a linear area.

FIG. 4 is a table showing the contents of a linear area in FIG. 3;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light amount control CPU 2 Non-volatile memory 3 Light amount control circuit 4 LED 5 LED power supply 6 Drive circuit 7 Photosensor 8 Amplification circuit 9 A / D converter 10 Light amount control system 20 Light amount detection unit

Claims (3)

[Claims] 1. A multiple light emitting device comprising: a plurality of light emitting diodes; and the same number of light quantity control circuits as the light emitting diodes, and having data for correcting variations in light quantity caused by individual differences between the light emitting diodes and the light quantity control circuits. In the beam drawing recording device, a VF value / light quantity characteristic curve for each light emitting diode is created based on the measurement result obtained by inputting a VF value and sequentially lighting the respective light emitting diodes, and forming each VF value. / The light amount characteristic curve is divided into areas in which the VF value and the light amount can linearly change within the input allowable range, and the light amount obtained on the drawing surface is referred to as a reference VF.
Reference light amount data instructing the light amount corresponding to the value is created, and when a VF value corresponding to a desired light amount is input at the time of drawing, the light amount obtained on the drawing surface is determined based on the reference light amount data. A light amount control data based on a VF value in a multi-beam drawing / recording apparatus, wherein light amount instruction data for obtaining the desired light amount is generated, and light amount control is performed in accordance with the light amount instruction data for obtaining the desired light amount. . 2. The light amount control method according to claim 1, wherein the reference VF value is an intermediate value between the respective areas. 3. The light amount instruction data for obtaining the desired light amount is set to D for the light amount instruction data for obtaining the desired light amount, the reference light amount data is set to X, and the VF value input at the time of drawing is set to VF. ₃ , wherein D = X · (VF _n / VF _ref ) where _{n is} a reference VF value and VF _ref is a reference value.
3. A light amount control method based on a VF value in the multi-beam image recording apparatus according to 1.