JPH0255158A - Optical printer - Google Patents

Abstract

PURPOSE:To maintain the intensity of a light constant even at any temperature by storing in advance the light emitting time of a light emitting diode array at a temperature in a ROM, and reading the stored value to vary the light emission. CONSTITUTION:When the temperature of a light emitting diode array 2 rises, the output of a temperature sensor 3 also rises, corresponding data stored in advance at a predetermined address corresponding to digital data A/D-converted by an A/C converter 4 from this output is read from a ROM 5, the light emitting time of the array 2 is prolonged, and so corrected in a direction for increasing the quality of emitting light reduced by the temperature rise. If the temperature falls, the output of the sensor 3 drops, the light emitting time of the diode 2 is reduced by the reverse operation to the above, and so corrected in a direction for decreasing the intensity of the light increased by the temperature fall so far.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an optical printer device, and in particular, a light emitting diode array consisting of a plurality of light emitting diodes serving as a point light source is arranged in an exposure section, and the light emitting diode array blinks. The present invention relates to an optical printer device that forms an image by using the following method.

[Conventional technology]

FIG. 4 is a block diagram showing a conventional optical printer device disclosed in, for example, Japanese Unexamined Patent Publication No. 59-202879. It is installed on the substrate 1 together with the temperature sensor 3. This temperature sensor 3 detects the temperature of the light emitting diode array as the temperature of the substrate. 10 is a subtracter that calculates the difference between the output voltage V obtained from the temperature sensor 3 and the reference voltage Vc, and 11 generates a positive or negative current (the absolute value II+ of the current is about 5 mA) according to the input voltage from the subtracter 10. 8 is a constant current source that supplies a constant current; 12 is an adder to which current is supplied from both the constant current source 8 and the voltage/current converter 11; this adder 1
2, the current input from the voltage-current converter 11 is added to or subtracted from the constant current obtained from the constant current source, and the calculated output is supplied to the light emitting diode array 2.

Note that the subtractor 10. Voltage current converter 11. The constant current source 8 and the adder 12 constitute a light emission amount control circuit B that controls the light emission amount of the light emitting diode array 2.

Next, the operation will be explained. Since the light emitting diode array 2 has a characteristic that the light intensity decreases as the temperature rises, the current supplied to the light emitting diode array 2 is adjusted by utilizing the property of the temperature sensor that the output voltage increases as the temperature rises. By adjusting the light intensity, you can control the light intensity.

That is, first, by setting the value of the reference voltage Vc corresponding to the operating reference temperature of each light emitting diode, and supplying this reference voltage Vc to the subtracter 10, the subtracter 10
Then, the difference with the output voltage V obtained from the temperature sensor 3 is calculated, and the calculated value is supplied to the voltage-current converter 11. The voltage-current converter 11 generates positive and negative currents according to the calculated values, and supplies the generated currents to the adder 12. For example, when the temperature of the light emitting diode array 2 is higher than the set temperature, a positive differential pressure value is obtained from the subtracter 10, so the voltage-current converter 11 generates a corresponding positive current and adds it. 12. Therefore, in the adder 12, the current generated by the voltage-current converter 11 increases with respect to the constant current, and a current larger by the added amount is supplied to the light emitting diode array 2, and the output from the light emitting diode array 2 increases. Suppresses a decrease in the light intensity of light.

Also, contrary to the above case, the light emitting diode array 2
If the temperature at is lower than the set temperature, then adder 1
2, a current smaller than the constant current is supplied to the light emitting diode array 2, thereby suppressing the output light from becoming excessive.

[Problem to be solved by the invention]

Since the conventional optical printer device is configured as described above, it is not difficult to arbitrarily set the amount of change in current with respect to the temperature of the light emitting diode array 2, and the light emitting diode array 2 is configured according to the input current. As increases,
Since the light output does not increase linearly, there have been problems such as the inability to perform light intensity correction as desired.

This invention was made in order to solve the above-mentioned problems, and has a simple circuit configuration. Furthermore, it is possible to arbitrarily set the amount of correction for the amount of light emitted by the light emitting diode array in response to temperature changes, and it can be adjusted to any temperature. It is an object of the present invention to provide an optical printer device that can perform desired light amount correction even when the amount of light is changed.

[Means to solve the problem]

The optical printer device according to the present invention includes a light emission amount control circuit that controls the amount of light emission of the light emitting diode array, and a memory that outputs light emission time data corresponding to the temperature of the light emitting diode array, and a memory that outputs light emission time data corresponding to the temperature of the light emitting diode array. and a drive circuit for driving the light emitting diode array.

[Effect]

The light emitting amount control circuit of the light emitting diode array in this invention converts the output of the temperature sensor from analog to digital,
The digital value is input to a ROMK that stores information on how to change the light emitting time with respect to temperature, and the output data of the ROM is compared with the value of a counter that operates at a constant cycle. By controlling the current supply time to the light emitting diode array according to the output data, the light emitting time of the light emitting diode array is changed according to the temperature, thereby controlling the amount of light.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure, 3 is a temperature sensor as shown in FIG. 2 attached to the substrate 1 for mounting the light emitting diode array 2;
4 is the output of the temperature sensor 3, that is, an analog/digital converter (hereinafter referred to as
5 is a read-only memory (hereinafter referred to as RO) that stores how much time the light emitting diode array 2 should emit light according to the detected temperature.
6 is a counter that operates at a constant cycle; 7 is a comparator that compares the output of ROM 5 and the output of counter 6, and outputs @1" if the output of counter 6 is smaller than the output of ROM 5; 8 is a constant current source that supplies a constant level of current to the light emitting diode array 2; 9 is a constant current source 8;
This transistor serves as a drive circuit for the light emitting diode array 2 and prohibits supplying the output current to the light emitting diode array 2 during the period when the output of the regulator T is 10''. Device 4, ROM5,
The counter 6° comparator T and constant current source 8 constitute a light emission amount control circuit A.

Next, the operation will be explained. The temperature data of the light emitting diode array 2 detected by the temperature sensor 3 is first
The data is converted into a digital value by the D converter 4 and input to a predetermined address in the ROM 5. The setting value of the light emitting time at the detected temperature is written in the corresponding address of the ROM 5, and this setting value is read out at a certain timing and is sent to a controller 7 (later T) that compares the magnitude relationship between the digital values. is input.

A counter 6 that operates at a constant cycle is connected to the other input of the comparator 7, and when the counter value is smaller than the output of the ROM 5, the
1" is output, and if it is larger, 10" is output. This output is then input to transistor 9. The transistor 9 is turned on when the output of the comparator 7 is 111, and the output current of the constant current source 8 is supplied to the light emitting diode array 2 through the transistor 9, and the light emitting diode array 2 emits light. On the other hand, the transistor 9 is turned off when the output of the comparator T becomes O'', and the output current of the constant current source 8 is not supplied to the light emitting diode array 2, so that the output of the comparator 7 becomes 10.
No light is emitted during period 9.

According to the above), if the output data of the ROM 5 continues to be a larger value than the output of the counter 6, the comparator 7 will write "
1@ is output for a long period of time, and therefore the light emitting time of the light emitting diode array 2 becomes long. On the other hand, if the output data of the ROM 5 is p smaller than the output of the counter 6, the period during which the comparator 7 outputs 111 will not be short, and therefore the light emitting time of the light emitting diode array 2 will be short.

The light emission intensity of the light emitting diode array 2 is proportional to its light emission time, so if the output data of the ROM 5 is large, the light emission intensity will be proportionally strong, and if the output data is small, the light emission intensity will also be proportional to it. becomes smaller.

In this way, if the output of the temperature sensor 3 increases as the temperature rises, then as the temperature rises, the ROM 5 will output corresponding data to compensate for the deterioration in light intensity that accompanies the temperature rise. Become. As the temperature of the light emitting diode array 2 rises, the output of the temperature sensor 3 also rises, and this output is converted into digital data by the A/D converter 4. is read out from the ROM 5, the light emitting time of the light emitting diode array 2 is extended, and a correction process is executed in the direction of increasing the amount of light emitted, which has decreased due to the temperature rise.

Furthermore, when the temperature falls, the output from the temperature sensor 3 falls, and the light emitting diode 2 operates in the opposite manner to the above.
The correction process will be performed in the direction of reducing the light emission time and the light intensity, which has been increasing due to the temperature drop.

In addition, by changing the value written to ROM 5,
It goes without saying that the amount of temperature correction of the light intensity can be easily changed depending on the temperature characteristics of the temperature sensor 3 and the light emitting diode array 2.

Furthermore, even if the counter 6 is a countdown type counter or the temperature sensor 3 output decreases as the temperature rises, the contents of the ROM 5 can be configured such that the larger the input data, the smaller the output data. ,
Similarly to the above, the light intensity can be kept constant regardless of the temperature of the light emitting diode array 2.

FIG. 3 shows another embodiment of the present invention, in which numerals 2 to 9 are blocks similar to those described above. Reference numeral 13 is a latch that temporarily holds external input data, which is input to the ROM 5 together with the output of the A/D converter 4.

Accordingly, by setting input data to the siratch 13 using, for example, a microprocessor that controls an optical printer device, it is possible to change the read data of the ROM 5 even at the same detected temperature. Thereby, by writing several types of data into the ROM 5, it becomes possible to freely control the emission intensity with respect to temperature from the outside.

〔Effect of the invention〕

As described above, according to this invention, the light emitting time of the light emitting diode array with respect to temperature is stored in advance in ROM K, and the stored value is read out to change the light emitting time. The light emitting time value can be changed by simply rewriting the ROM, and since the light intensity of the light emitting diode array is controlled by the light emitting time of the light emitting diode array, the light intensity can be kept constant regardless of the temperature. It has the effect of getting something.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an optical printer according to an embodiment of the present invention, FIG. 2 is a perspective view showing an exposure source structure of a light emitting diode array used in the present invention and a conventional optical printer, and FIG. FIG. 4 is a block diagram showing another embodiment of the invention. FIG. 4 is a block diagram showing a conventional optical printer device. 2 is a light emitting diode array, 5 is a memory (read-only memory), 9 is a drive circuit (transistor), and A is a light emission amount control circuit. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] A light emitting diode array consisting of a plurality of light emitting diodes, a temperature sensor that detects the temperature of this light emitting diode array, and an amount of light emitted by this light emitting diode array based on the output of this temperature sensor regardless of changes in the temperature of the light emitting diode array. In an optical printer device, the light emission amount control circuit is equipped with a memory that outputs optimum light emission time data corresponding to the temperature of the light emitting diode array, and the output time data. and a drive circuit that drives the light emitting diode array during the time.