JPS5896794A - Method of photo output stabilization for laser diode and device thereof - Google Patents

Abstract

PURPOSE:To obtain the stabilized photo output as well as to extend the life of the titled device by a method wherein the driving current level is determined at the starting point of scanning in such a manner that the photo output intensity of a laser diode will be brought to a constant level, while the temperature of the diode is detected, and when the temperature became higher than the prescribed one, the device is cooled using an electron cooler. CONSTITUTION:A constant output driving circuit 1 is connected to an electron cooler 3, consisting of a Peltier element and a high heat conductive material 3 provided with a laser diode 2 and a heat sensitive element 4 on the surface, is placed in the cooler 3. Then, the output of the heatsensitive element 4 is sent to a temperature controlling circuit 6 through the intermediary of an amplifier 5, and a part of the output of the circuit is fed back to the cooler 3 by the microprocessor 7 which is connected to the temperature controlling circuit 6. Thus, the drivng current level is determined at the starting point of scanning so that the photo output intensity will be brought to a constant level, and when the temperature detected by the element 4 became higher than the prescribed temperature, the diode 2 is cooled by the cooler 3.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a method of modulating the output laser beam of a sea 1f diode (hereinafter referred to as 1-1) and irradiating it onto the surface of an image carrier to form an image. The present invention relates to a method and device for stabilizing LD light output for use in a beam image forming apparatus and the like.

11], the supply current rapidly increases to 1, exceeding the threshold value 1tl+. 11) is driven by a current 1 novel in the @ range that shows this rapid increase, but the threshold [[11 is l tlcc ex1+ (T' / -l” c
) However, TC; characteristic hybrid τ depends on 1Ii2 degrees 1 of LD, as shown. Therefore, even if the LD is driven with a constant current, 1
As the temperature of O increases to 10M, the optical output decreases, and conversely, as the temperature decreases, the optical output increases. If the temperature reaches M 'T', the LD output (light output) may exceed the maximum rating. In order to
[1] Detect the output and set it to L so that it matches the reference value.
There is a control method that keeps the drive current level of D constant (there is a control method that keeps the drive current level constant).

However, even if 1., heto) 0 or (J), the temperature rises due to self-heating of 11), which causes the threshold value 111]
-As the temperature rises, the lifespans of L and D decrease dramatically.

Now, control the LD bias current and configuration so that it is always constant! A method of doing this is also being considered. However, this method involves heating and cooling using positive and negative power supplies to keep the temperature constant, and there is a problem in that the circuit configuration becomes complicated.

1) An object of the present invention is to provide a method and device for stabilizing the optical output of a laser diode, which can easily achieve stable light use and also prevent the decrease in life as described in 1.1].

The method of the present invention to achieve this object determines the driving current level of the SE11 diode at the start of scanning so that the optical output intensity of the RAKE diode is at a constant level, and also detects the tlii degree of the laser diode. , when the temperature is higher than the set temperature of 10 J, the laser diode is cooled by 1 J to the laser diode optical cooling device. 11 electric coolers installed on a good thermal conductor integrated with the electronic cooler, the rake with the number attached to the electronic cooler.
A heat-sensitive element that indirectly detects the temperature of the diode drives the laser diode at the start of scanning so that the light output intensity of the laser diode remains at a constant level. The present invention is characterized in that it includes a control means for determining the flow rate of the Ii flow.

The following is a detailed description of the present invention with reference to the drawings.

FIG. 1 is a schematic diagram showing the main parts of an embodiment of a device implementing the method for stabilizing the optical output of a laser diode according to the present invention. In the figure, 1 is to 1〕0 circuit, 2 is △PC
Circuit 1 t: J: LD driven by beam, 3 beams, D
2 and a thermal conductor 8 integrated with the heat-sensitive element described below: J ray 11) An electronic cooler for cooling the temperature of 2, and 7 is used for the Pelchi 1 element. The Pelder element is a type of PN junction semiconductor element, and can perform either heating or cooling depending on the direction of current flow, but in the present invention, only the cooling function is performed. 4 is a heat-sensitive cord attached to the heat conductor 8 integrated with ]-02 and having one thread;
It detects the IJ)2's dryness through the IJ), converts it into an electrical signal, and sends it out. Reference numeral 5 denotes an amplifier which appropriately amplifies the output of the heat sensitive element 4 and guides it to the temperature control circuit 6. The temperature control circuit (3) compares the value of the preset temperature 1o with the value of the temperature 1'fT of ID2 given by the amplifier 5, and drives the perdeg J rate 3 from T>T'Otr. It operates so that the temperature of [, D2 becomes below TO. When T;≦-[0, the temperature ready signal ("
The control circuit 7 determines that the image forming operation is possible, and appropriately drives each section including 1-D2.

As this control circuit 7, a microphone 1-1 plug or the like is used. After that, due to self-heating of D2, etc., "r >-ro",-1"oJ, a little bit ^^
While the temperature is below To11, the image forming operation state is enabled, a humidity rare signal is sent to the control circuit 7, and the temperature is lowered by the operation of the Vertier element 3.

FIG. 2 is an explanatory diagram τ゛, 21 of an embodiment of the △PC circuit 1.
1-D2 is a photodetector such as a photodiode that takes out a part of the output and detects the optical output intensity; 22 is the photodetector 2;
23 is a differential amplifier that takes the difference between the reference voltage Vref and the output of amplifier 22, amplifies it appropriately and outputs it, and 24 is a differential amplifier that amplifies the output of differential amplifier 23. This is a sample and hold circuit that performs a hole recovery. The sample hold circuit 24 is set to operate in synchronization with the ripple hold signal S/H provided by the control circuit 7.

25 is an L f) driver, and a ripple hold circuit 24
1-02 is driven at a current level corresponding to the output J voltage, and this drive WI current turns ON-OFF' F in response to a modulation signal (ON/OFF signal based on image information).

In such a closed-loop A130 circuit, by appropriately selecting the amplification factor of the amplifier 22, the difference between the two input signals of the differential amplifier 23 becomes zero.
A constant level of light output of 2 is obtained. The scratch number hold circuit 24 was set up here because of the following five hits. The light output intensity of the L-C, which is driven by an irregular modulation signal whose average level is not constant, such as the L/-17 printer, remains constant even if APC control is performed during the image formation period. There is no level controlled protection. Therefore, during the period of one main scan or one page scan when the L-D temperature does not change much, and also at the start of scanning before the image information output laser beam irradiates the image carrier, There is a need to automatically adjust and fix the B1 power level.Therefore, sample hold circuit 2
The drive current level was determined at the start of the scan by crossing 7I, and the current level was set to continue around until the scan was completed, so that a modulated beam with a constant optical output could be fired. It's IJ.

According to the apparatus of the present invention having such a configuration, 1+scanning or 1
At the initial stage of each page scan, the optical output intensity level of [-D2 is automatically adjusted and fixed at a constant level of T corresponding to the reference value. In this case, 0shi1. , I) When the temperature 1 of 2 is higher than 0, the temperature control circuit 6 causes the Pelch element T to
! -3 is activated, the cold air IJ operation is performed, and the temperature of L1]2 is lowered to To.

After the temperature of L, D2 is controlled to 10, 1VIl
The lt11 circuit 7 receives 'tF given from the temperature control circuit 6.
=A IGt Ready 11; Detects No. P1 and starts image forming operation, knowing that it is ready for image forming operation by pulling the image information output. 1. , D2 is self-heating τ
Even if the current I'f, . In addition, the set moisture level To in this case is approximately 20.
Set to -30'C 1. ,, D 2's λ is preventing the decline in life.

By the way, in the embodiment of J above, the optical output intensity of 11)2 was directly monitored and the optical output intensity was controlled to a constant level, but this is limited to 11). 1 based on which relationship first) to control a 1 no (also) -
stomach. FIG. 3 is a diagram showing the relationship between temperature T and drive current [d at constant optical output.

It can be seen that if the current 1d relative to J is determined at a certain temperature based on this relationship and l-02 is driven with the current 2 of A, a constant level of optical output can always be obtained. FIG. 4 is an explanatory diagram showing an embodiment for realizing this method, and 41 is a temperature measuring circuit that measures the temperature of the LD 2 via a good thermal conductor 8 integrated with the Beltier element 3, converts it into a voltage signal, and outputs it. , 42 is a function generator which converts the output Vs of the temperature measuring circuit 41 shown in FIG.
This converts it into voltage characteristics. The curve itself shown in FIG. 5(b) exactly matches the curve in FIG. 3.

Reference numeral 43 denotes an adder that adds the off-hit voltage VOS to the output vO of the function generator 42 and outputs the result.The relationship between the output V and the temperature T is as shown in (c) of FIG. This is similar to the relationship shown in Figure 3. The L[) driver 25 drives LD2 at a current level proportional to the output V of the adder 43. As a result, L.D.
By determining the temperature T of 2 and automatically changing the drive current level accordingly, it is possible to obtain a constant light output. As the function generator 42, it is of course possible to use a well-known diode polygonal line approximation circuit or a digital polygonal line approximation circuit.

As explained above, according to the present invention, the optical output intensity level of the ID is kept constant at the first 1 to 11 steps of scanning, and the temperature of 1-1] is kept lower than the set temperature If T O until 1-1. In this case, the cold M1 device is activated to control the temperature to less than 1.
Since one forming operation is performed only when the temperature of [) is below TO, it is possible to form an image with stable to constant light output while reducing the lifetime of [() by 11 points. Furthermore, since there is no need to use a heating power source, the configuration becomes simpler.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing an embodiment of an apparatus for implementing the method for stabilizing the light output of a sea die according to the present invention;
Fig. 2 is an explanatory diagram of an embodiment of the △PG circuit, Fig. 3 is a diagram of the temperature and current f1 of the LD at a constant optical output level, and Fig. 4 is another embodiment of the main part of the device according to the present invention. There is a diagram showing the characteristics of the signals of the six sections Jl; IJ in Fig. 4. 1...APC circuit 2...River, 1〕3...Electronic cooler 4...Thermal elephant I5.22...Amplifier
6...Temperature control circuit 7...Control circuit 21...Photodetector 23...Differential amplifier 24...
...Sample hold circuit 25...ID driver 41...Temperature measurement circuit 42...
・Function generator 43... Adder patent applicant Roku Konishi photo - Business stock payment agent Rito Ben Sokuju
Tsukishima Mutsu Tomari Atsushi (a) ■ (c) Figure 5 (b)

Claims (8)

[Claims] (1) When the drive current level of the laser diode is determined at the start of scanning so that the optical output intensity of the laser diode is constant 1 novel, the concentration of the laser diode is detected and the flood polishing is set at -. A method for stabilizing the optical output of a laser diode, characterized in that when the hot water temperature is higher than TO, the laser diode is cooled by a thermoelectric cooler. (2) As a method of controlling the optical output intensity to a constant level, a Rayleigh diode drive current level is determined so that a monitored output of the laser diode matches a reference value. A method for stabilizing the optical output of the 1 nose diode described above. (3) 7J method to keep the light output intensity at a constant level, detect the temperature of the Rayleigh diode, and set the light output intensity to a constant level by Δ3(J) based on the relationship between temperature and drive current. (The method for stabilizing the optical output of a laser diode according to claim 1, characterized in that the drive current level for firing is determined. (4) The method for stabilizing the optical output of a sea 1f die A-de as set forth in claim 1, wherein the set temperature 10 is 20.about.30.degree. (5) A method for stabilizing a laser diode according to claim 1, characterized in that the distribution cooler is a Peltier element. (6) A thermoelectric cooler installed on a thermally good conductor integrated with a Rayleigh diode, and a thermoelectric cooler mounted on the thermoelectric cooler (
= J t) A heat-sensitive element that indirectly detects the temperature of the laser diode A and a laser diode at the start of scanning so that the leading horn intensity of the 17-ray diode is at a constant level. A device for stabilizing the optical output of a laser diode, characterized in that it comprises a control means for determining the drive current level of the laser diode. (7) Claim 0, characterized in that the control means is means for detecting a part of the optical output of the laser diode and determining the driving current level so as to match the reference tin. Optical output stabilization device for a laser diode described above, 1 (8) The control means may be used for sale of laser diodes.
Particular feature ii' characterized by a means for storing the relationship between temperature and drive current at constant intensity and determining the drive current level for m degrees of the ray IJ' die A-D based on this relationship.
F. An optical output stabilizing device for a laser diode according to claim 6.