KR100541945B1 - LD beam power and temperature control apparatus and method - Google Patents

Abstract

The present invention relates to an apparatus and method for driving a laser diode by calculating an optimal driving voltage by simultaneously controlling the optical power and temperature of the laser diode by using a purge controller.

According to the present invention, a monitor current measuring unit measuring a monitor current generated from a laser diode, a comparator comparing the monitor current with a reference optical power, and a comparison error between the reference optical power value and the output optical power value measured from the comparator An optical power controller for controlling the driving voltage to be 0, a thermistor for measuring the temperature of the laser diode, a comparator for comparing the actual temperature and the reference temperature of the laser diode, a comparison of the reference temperature measured from the comparator and the actual laser diode temperature A temperature controller for controlling a driving voltage so that an error is 0, a purge controller for calculating an optimum output voltage using the outputs of the optical power controller and the temperature controller as input variables, and an LD for driving a laser diode according to the output value of the purge controller. Ray driven by the driving circuit and the LD driving circuit The optical power and simultaneous temperature control apparatus of a laser diode comprising a diode is provided.

On the other hand, adjusting the driving voltage in the optical power controller so that the comparison error between the monitor current of the laser diode and the reference optical power is 0, and the driving voltage in the temperature controller so that the comparison error between the actual temperature and the reference temperature of the laser diode is 0. Adjusting, purging each input variable using the membership function set with the output voltage of the optical power controller and the output voltage of the temperature controller as input variables, fuzzy rule experimentally obtained purge optical power and temperature Calculating an output voltage by substituting a base table, calculating an optimum output voltage by unpurging the calculated output voltage to an actual value, and driving a laser diode using the optimum output voltage. A method of simultaneously controlling the optical power and temperature of a laser diode comprising the step of Ulreo is provided.

According to the present invention, by controlling the optical power and the temperature of the laser diode at the same time, there is an effect that can be applied to the laser diode an optimum driving voltage that can maintain the proper temperature, the appropriate optical power.

Laser Diode, Optical Power, Temperature, Fuzzy Control

Description

Optical power and temperature control apparatus and method for laser diode

1A is a block diagram of an APC (Auto Power Controller) system which conventionally individually controls only optical power of a laser diode.

1B is a block diagram of a conventional ATC (Auto Temperature Controller) system for individually controlling only the temperature of a laser diode;

2 is a block diagram showing the configuration of a control unit for simultaneously controlling the optical power and temperature of a laser diode according to the present invention;

Figure 3a is an algorithm for the simultaneous optical power and temperature control method according to the present invention,

Figure 3b is a block diagram briefly showing a fuzzy control step of the steps of the present method;

4 is a graph of respective membership functions defined for temperature and optical power input in the purge step of FIG.

5 is a table of fuzzy rule bases used in the purge control step of FIG.

And,

6 is an output membership function graph obtained through the fuzzy rule base.

The present invention relates to an apparatus and method for simultaneously controlling the optical power and temperature of a laser diode in a laser scanning unit of a laser printer.

The laser printer uses a laser scanning unit to form an image transmitted from a computer onto a drum, toss the toner, and then presses the drum onto paper, thereby fixing the toner.

The laser diode used in the laser scanning unit is a diode that emits a laser when the input voltage exceeds a predetermined value, and the optical power and its temperature of the laser diode change according to the driving voltage. In other words, when the driving voltage is high, the optical power and the temperature of the diode itself increase, and when the driving voltage is low, the temperature decreases.

On the other hand, the laser diode generates heat only by the driving itself, and the laser scanning unit is sealed to protect the interior from external foreign matters, and thus, since the cooling is not performed by itself, the diode element is continuously printed. There is a risk of being damaged by heat. The LSU used in most low-cost laser printers does not have a means such as a FAN that can physically lower the temperature of the laser diode. Therefore, in order to prevent damage to the device, the LSU has to lower the driving voltage to lower the temperature.

On the other hand, it is not possible to excessively lower the driving voltage in order to lower the temperature. Therefore, it is necessary to control the driving voltage so that the printing can be performed in an optimal state and the stability of the device can be achieved.

Conventionally, the optical power and temperature of the laser diode are individually controlled through an APC (Auto Power Controller) and an ATC (Auto Temperature Controller).

As shown in FIG. 1, FIG. 1A shows an APC and FIG. 1B shows a simple block diagram of the structure of the ATC.

1A, it can be seen that the configuration for adjusting the optical power of the laser diode 40 is implemented in a kind of feedback form. That is, a monitor current measuring unit 50 measuring a constant monitor current from a laser diode and measuring the amount of light actually output, a comparator 10 comparing the amount of light measured from the monitor current measuring unit 50 with a reference optical power, An optical power controller 20 that adjusts an output voltage so that the comparison error measured by the comparator 10 becomes 0, and a laser diode (LD) driving circuit which drives a laser diode according to the output voltage adjusted by the optical power controller. It consists of a structure including (30).

On the other hand, Figure 1b is a block diagram showing a configuration for adjusting the temperature of the laser diode 90, according to the drawing, the thermistor 100 for measuring the temperature of the laser diode 90, based on the temperature measured from the thermistor Comparator 60 to compare the temperature, the temperature controller 70 to adjust the output voltage so that the comparison error measured by the comparator is 0, the laser driving the laser diode by the output voltage adjusted by the temperature controller 70 It consists of a structure including a diode (LD) driving circuit (80).

In such individual optical power and temperature control situations, the APC increases the driving voltage of the laser diode to increase the optical power, while the ATC may control the laser diode to lower the voltage to lower the temperature. In this case, since the actions of both controllers are opposite, it is difficult to apply a stable driving voltage, and thus there is a problem that the optimum driving voltage is not applied.

In order to solve the above problems, the present invention provides an apparatus and method for outputting an optimal driving voltage in consideration of optical power and temperature simultaneously by integrally controlling the optical power and temperature of a laser diode which has been independently controlled in one controller. It aims to provide.

In order to achieve the above object, the laser scanning unit according to the present invention, the monitor current measuring unit for calculating the output optical power by measuring the monitor current generated in the laser diode, a first comparing the monitor current and the reference optical power A comparator, an optical power controller for controlling a driving voltage such that a comparison error between the reference optical power and the output optical power measured from the first comparator is zero, a thermistor measuring the actual temperature of the laser diode, and an actual temperature of the laser diode A second comparator comparing the reference temperature, a temperature controller controlling the driving voltage such that the comparison error between the laser diode actual temperature and the reference temperature measured from the second comparator is zero, and an output variable of the optical power controller and the temperature controller. To an output value of the purge controller, A LD driver circuit for driving the laser diode la and is characterized in that it comprises a laser diode driven by a driving circuit to the LD.

On the other hand, the optical power and temperature control method simultaneously in the laser scanning unit according to the present invention, the step of adjusting the driving voltage in the optical power controller so that the comparison error of the output optical power and the reference optical power of the laser diode is 0, the laser diode Adjusting the driving voltage in the temperature controller so that the comparison error of the actual temperature and the reference temperature is 0, fuzzy terminology using the membership function set by using the output voltage of the optical power controller and the output voltage of the temperature controller as input variables A fuzzy conversion step of converting, connecting fuzzy input variables with fuzzy output terms using a pre-written fuzzy rule base, and an unpurging step of converting fuzzy output terms obtained from the fuzzy rule base into a specific output voltage; Driving the laser diode using the specific output voltage. Characterized in that it also.

Hereinafter, with reference to the accompanying drawings will be described in detail with respect to the optical power and temperature control device and control method of the laser diode of the present invention.

2 is a block diagram showing a configuration of a control device according to the present invention. Referring to the drawings, first, a laser diode 250 is basically configured, and an output optical power is measured by measuring a thermistor (280) for measuring the temperature of the laser diode and a monitor current of the laser diode (250). The monitor current measuring unit 290 is configured.

Meanwhile, a first comparator 210 configured to compare the output optical power measured by the monitor current measuring unit 290 with a preset reference optical power is configured and output voltage according to the result measured by the first comparator 210. The optical power controller 220 to adjust the configuration is configured. Specifically, the optical power controller 220 controls the output voltage when the output optical power is higher than the reference optical power and lowers the output voltage, and increases the output voltage when the output optical power is low, so that the output optical power is as close to the reference optical power as possible. Control as possible.

In addition, the temperature controller adjusts the output voltage according to the result measured from the second comparator 260 and the second comparator 260 comparing the actual temperature of the laser diode measured by the thermistor 280 with a preset reference temperature. 270 is configured. In detail, the temperature controller 270 controls the output voltage when the actual temperature of the laser diode is higher than the reference temperature, and lowers the output voltage when the laser diode is lower than the reference temperature.

The output voltage regulated from the optical power controller 220 and the temperature controller 270 is readjusted to the optimum output voltage by the purge controller. The purge controller 230 purges the outputs from the optical power controller 220 and the temperature controller 270 as input variables, calculates an output voltage according to the fuzzy rule base, and defuses again. The optimum output voltage will be calculated. A detailed description of the purge control method will be given later.

According to the optimum voltage calculated from the purge controller 230, the LD driving circuit 240 applies a driving voltage to the laser diode 250, and the laser diode focuses light on the drum to perform a writing step. do.

On the other hand, the optical power and temperature simultaneous control method according to the present invention is shown in Figure 3a the algorithm. Referring to the drawings, first, the thermistor 280 and the monitor current measuring unit 290 is subjected to the step of measuring the output optical power and temperature of the laser diode (S310).

When the optical power and temperature are measured, the APC and ATC output voltages are calculated by comparing the reference optical power value and the temperature (S320). The optical power comparison is performed through the first comparator 210, and the optical power controller 220 is configured such that the preset reference optical power is equal to the output optical power measured from the monitor current measuring unit 290 as much as possible. The APC output voltage is adjusted so that the comparison error of the one comparator 210 approaches zero. Similarly, the temperature controller 270 adjusts the ATC output voltage such that the actual temperature measured by the thermistor 280 is equal to the preset reference temperature as much as possible, that is, the comparison error of the second comparator 260 is close to zero. .

In general, the APC output voltage and the ATC output voltage have different values, and through fuzzy control, an appropriate output voltage corresponding to the middle of both output voltages should be calculated. This process is a fuzzy control step (S330). A detailed process of the purge control is illustrated in FIG. 3B.

That is, first, the APC output value (voltage) and the ATC output value (voltage) are two input variables, and then purged (S410). The fuzzy step converts the input variables into fuzzy terms. This conversion is done by an input membership function. The input membership functions for the two input variables, namely ATC and APC output voltages, are shown in Figs. 4 (a) and 4 (b), respectively.

Referring to the case of the specific ATC output voltage A and APC output voltage B in the drawing, the ATC output voltage A is a case where the actual temperature is the same as the reference temperature, with zero being 100%, and the APC output voltage B is based on the actual optical power. It can be said that about 50% of the temperature is the same, but about 10% means that the voltage slightly exceeded. That is, the ATC output voltage is converted to a fuzzy term of zero, the APC output voltage is zero 50%, and the PS 10%.

The next step is to connect the fuzzy input variables with fuzzy output terms (S420). The rule base is created based on experimental data. On this rule basis, a simple one-to-one relationship or several input / output relationships can be established. According to an embodiment of the present invention, the rule base shown in FIG. 5 may be used. If A and B are input variables based on the rule base, it can be seen that a plurality of input / output relationships are formed between the input and the output. . That is, since the temperature is zero and the optical power is zero 50% and positive small 10%, the output variables are zero 50% and PS 10%. In an embodiment of the present invention, the case in which either the ATC output voltage or the APC output voltage corresponds to Negative Large or Negative Medium is not prepared, but may be written with reference to experimental data when necessary.

The last step of the fuzzy control step is an unfuzzy step of converting fuzzy output terms generated in the rule base to a specific output value (S430). Unpurging is done in almost the reverse order of the purge process. Fig. 6 shows a graph of the output membership function obtained for the present invention. The transformed fuzzy terms are converted into specific output values through the output membership function of FIG. 6. There are several ways to switch, but if one uses the center of gravity conversion, it can be expressed by the following equation.

In the above formula, Vo is the optimum output voltage, ST (zero), ST (PS), ST (PL) is the output membership function value at zero, PS, PL 100%, respectively, mo1, mo2 and mo3 represent the membership function values of zero, PS and PL of the fuzzy rule base, respectively. By the above formula, an appropriate level of output voltage can be calculated based on the ratio of each state.

On the other hand, if the optimum output voltage is calculated through the purge control step (S330), the LD driving circuit applies the calculated output voltage to the laser diode to drive the laser diode (S340).

The foregoing detailed description of the invention has been presented for purposes of illustration and description, and is not intended to limit the invention thereto. In view of the above description, those skilled in the art can make improvements and modifications without departing from the spirit and scope of the present invention.

According to the present invention, by controlling the optical power and temperature of the laser diode simultaneously in one controller, there is an effect that the optimum driving voltage can be applied to the laser diode to have a constant optical power while maintaining the proper temperature of the laser diode. .

Claims (4)

In the laser diode driving device for supplying a driving voltage for driving a laser diode, An optical power controller comparing an output optical power of the laser diode with a predetermined reference optical power and calculating an APC (Auto Power Controller) output value; A temperature controller which calculates an ATC (Auto Temperature Controller) output value by comparing the actual temperature of the laser diode with a predetermined reference temperature; A fuzzy controller configured to calculate an optimal value of the driving voltage by performing fuzzy control using each of the APC output value and the ATC output value as an input variable; And, And an LD driving circuit for driving the laser diode by outputting a driving voltage having the magnitude calculated by the purge controller. The method of claim 1, A monitor current measuring unit which calculates an output optical power by measuring a monitor current generated by the laser diode; A thermistor for measuring the actual temperature of the laser diode; A first comparator comparing the output optical power measured by the monitor current measuring unit with the reference optical power; and And a second comparator for comparing the laser diode actual temperature measured by the thermistor with a reference temperature. In the laser diode driving method for driving a laser diode by supplying a driving voltage of a predetermined size, Calculating an APC (Auto Power Controller) output value by comparing the output optical power of the laser diode with a predetermined reference optical power; Calculating an ATC (Auto Temperature Controller) output value by comparing the actual temperature of the laser diode with a predetermined reference temperature; Calculating an optimal value of the driving voltage by performing fuzzy control using the APC output value and the ATC output value as input variables; And, And driving the laser diode by outputting a driving voltage having the calculated magnitude. The method of claim 3, The calculating of the optimal driving voltage by performing the purge control, A fuzzy step of converting each input variable into fuzzy terms using a preset membership function; Associating fuzzy input variables with fuzzy output terms using a pre-written fuzzy rule base; and And a non-fuzzy step of converting the fuzzy output terms obtained from the fuzzy rule base to a specific output value.

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