JPS6349422B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image forming apparatus that forms images using a semiconductor laser.

As shown in FIG. 1, a semiconductor laser device (hereinafter referred to as an LD device) has a positive electrode contact 1, a P layer 2,
N layer 3, negative electrode contact 4, reflective surface 7 and P
It has a power source 5, a heat sink 6, etc. for flowing current through the -N junction.

When a large amount of minority carriers are injected to form a population inversion by passing a DC current through the above P-N junction, this state is unstable and the holes in the valence band are removed within 10 ^-9 to ^{10 -8} seconds. and a photon with energy corresponding to the level difference is emitted.At this time, stimulated emission becomes possible, and if the conditions are met, laser oscillation occurs. The semiconductor materials used in lasers are CdS,
ZnTe, CdSe, GaAs ₁ −xPx, GaAs, GaAlAs,
InP, InSb, and PbTe are listed.

Early LD devices were limited to pulse oscillation at a low duty ratio at room temperature, and continuous operation was inconceivable, but in the 1970s, the development of double heterostructures made continuous operation possible. Summer. Figure 2 shows such a double heterostructure LD.
8 indicates a positive electrode contact,
9 is a P-GaAs layer, 10 is a P-GaAlAs layer, 11
12 is a P-GaAs layer, 12 is an n-GaAlAs layer, and 13 is an n-GaAs layer 14 is a contact for a negative electrode.

The double heterostructure that was made possible achieved good results by confining the carrier and light in the direction of current flow, so to speak, in the vertical direction by providing junctions of materials with large band gaps on both sides of the light emitting part. However, by performing these confinement in the lateral direction using techniques such as mesa etching, it is possible to achieve a single mode, lower current operation, and increase the output density. The maximum continuous oscillation output currently available is about 20mW. In order to operate an LD element continuously at room temperature, it is currently necessary to mount it on a heat sink to effectively dissipate the heat generated inside the diode.

FIG. 3 is a partially cutaway perspective view showing an example of the internal structure of a conventional commercially available semiconductor laser generator. 15 is an LD element with a size of 0.5 mm or less, and one side of the electrode is welded to the heat sink 16 with indium solder or the like. A lead wire 17 is bonded to the other electrode. The heat sink 16 is sealed from the outside air by being fixed to a metal seal 18 having a dustproof glass 18a and mounting screws 18b with indium solder or the like.

Although the LD element operates in continuous oscillation at room temperature,
Fluctuations in external temperature and junction temperature due to longer modulation times cause variations in light output. In order to perform beam intensity modulation in addition to pulse modulation, it is necessary to suppress the fluctuation ratio of the light emission output to 1% or less. In addition, in the case of pulse modulation, even if the incident energy level is set within the saturated region of the recording sensitivity of the recording medium, experimental results show that it is necessary to keep the variation ratio below 10%.

In order to control this temperature fluctuation, temperature has conventionally been detected using a temperature sensing element such as a thermistor. However, temperature sensing elements such as thermistors
It was only possible to detect the temperature around the LD element, but not the actual junction temperature. The thermistor also has the disadvantage of slow response time. Furthermore, in a laser storage device, the temperature of the LD element is unknown immediately after the power is turned on, so if recording is continued with the laser, the beam intensity will fluctuate greatly.

The present invention has been devised in view of the above-mentioned points, and it is an object of the present invention to provide an image forming apparatus capable of producing stable image signals.

That is, the present invention includes a semiconductor laser, a means for supplying a drive current to the semiconductor laser, a detection means for detecting the temperature of the semiconductor laser, and a detection output of the semiconductor laser according to a detection output of the detection means. a control means for controlling a temperature; and before the start of recording by the semiconductor laser, the supply means performs temperature control while supplying the drive current at a predetermined timing, and the detection output of the detection means reaches a predetermined value. and means for outputting a permission signal for permitting the semiconductor laser to start recording an image when the range is set within the range.

As a result, more stable image recording can be performed than in the case where the temperature of the semiconductor laser is simply controlled.

FIG. 4 shows an explanatory diagram of temperature control in this embodiment. In Fig. 4, 20 is a heat sink;
21 is a metal piece made of a material having good thermal conductivity and electrical conductivity, such as pure copper; 22 is a thermoelectric cooling element, here a Peltier element; 23 is a terminal plate;
4 is an insulating board such as a ceramic insulating board that has good thermal conductivity but is a poor electrical conductor; 26 is an LD element; 25 and 27 are terminal boards for the LD element 26;
8 is a resistor, 29 is a switch, 30 and 31 are terminals, 32 is a temperature detection circuit, 33 is a temperature control circuit,
V indicates a power source.

It is well known that the terminal voltage of an LD element when a constant forward current is applied to its terminals is correlated to the junction temperature of the LD element. This property is the same whether the LD element is emitting laser oscillation or not. Here, it is assumed that the junction temperature is detected when the LD element 26 is not laser oscillating. Switch 29 is connected to either terminal 30 or 31. When the switch 29 is connected to the terminal 31 side, a current sufficient to perform laser oscillation flows through the LD element 26, and the LD element 26 performs laser oscillation. When the switch 29 is connected to the terminal 30 side, the current flowing through the LD element 26 is resistor 2
8, an insufficient current flows to perform laser oscillation. The terminal voltage of the LD element 26 at this time is input to the temperature detection circuit 32. The temperature detection circuit 32 controls the temperature control circuit 3 to cool down the LD element 26 if the junction temperature is higher than the standard operating temperature.
3, and if the temperature is lower than the standard operating temperature, a signal is sent to the temperature control circuit 33 to heat it. The temperature control circuit 33 is used to flow current to the Peltier element 22 via the terminal plates 21 and 23 when cooling the LD element 26. Peltier element 2
When 2 is energized, a heat radiation phenomenon occurs at the joint surface with the terminal board 23, and the heat is radiated from the heat sink 20, and the terminal board 2
An endothermic phenomenon occurs at the junction surface with 1 and cools the LD element. Conversely, when heating the LD element 26, current is passed through the Peltier element 22 in the opposite direction. Then, a heat absorption phenomenon occurs in the Peltier element 22 at the joint surface with the terminal plate 23, and a heat radiation phenomenon occurs at the joint surface with the terminal plate 21, heating the LD element. In the present description, both heating and cooling have been described, but since the temperature of a semiconductor laser generally increases when it oscillates, only cooling may be performed.

A preferred example for carrying out the present invention described above will now be described in detail.

A laser recording apparatus using the temperature control device for a semiconductor laser element of the present invention will be explained based on FIG. Reference numeral 101 denotes a recording unit using an electrophotographic process, which includes a photosensitive drum 102, a developing device 103, a heat fixing device 104, a charger 105, a paper feed mechanism 106, a recording paper 106a, etc., and is a recording unit that uses a known electrophotographic process based on image light. The electronic latent image formed on the surface of the photosensitive drum 102 by the process is transferred to a charging device 105 and a developing device 103.
The latent image is visualized by the latent image, and an image based on the latent image is printed out on recording paper 106a fed by the paper feeding mechanism 106. Inside the recording paper 101, various optical elements and an optical mounting table 107 for mounting the optical elements are housed. The optical mounting table 1
07, the LD element 108, which is a light source for inputting the image information beam to the photosensitive drum 102;
Transmits a part of the laser beam emitted from the LD element,
A semi-transparent mirror 109 that partially reflects the semi-transparent mirror 109
a beam intensity detection device 110 that inputs and detects the beam light reflected from the semi-transparent mirror 109; a reflecting mirror 11 that bends the beam light that has passed through the semi-transparent mirror 109;
1. Beam expander lens 1 that expands the diameter of the beam reflected from the reflecting mirror 111
12, a galvanometer mirror scanner 113 for scanning the beam onto the surface of the photosensitive drum 102;
An imaging lens 114 for forming an image of the light beam scanned by the scanner 113 on the photosensitive drum surface, an imaging lens 114 provided near the start of scanning of the scanning beam emitted from the imaging lens 114, and reflecting the scanning beam. A beam position detection mirror 115 for detecting the beam position and a beam position detection device 116 for detecting the beam light from the mirror 115 and generating a cueing signal are provided. The lower case 117 houses a power supply section 118, a sequence control circuit section 119, and an image signal control circuit section 120. A plate 121 having a mounting hole for the expander lens 112 on the surface of the optical mounting table 107, a plate 122 having a mounting hole for the imaging lens, a hole for setting the optical axis, and a light detection plate on the back side of the hole. A plate 123 with a container 123a is mechanically positioned and fixed such that the centers of the holes are optically aligned.

Further, a disc 124 having a hole for setting an optical axis is removably fitted to the tip of the expander lens 112 so that the center of the hole coincides with the optical axis of the expander lens 112. A wavelength of 8000 is applied all around the holes of the plate 123 and the disc 124.
A phosphor is provided that emits visible light when excited by ~9000 Å light.

The position of the laser beam image can be observed by removing the galvanometer mirror scanner 113 and projecting the image of the laser beam emitted from the expander lens 112 onto the phosphor surface provided on the plate 123. . Further, the direction of the laser beam is made parallel to the optical axis of the expander lens 112 by rotating the reflecting surface of the reflecting mirror 111. As a result of the optical path adjusting means causing the entire luminous flux of the laser beam to pass through the holes in the plate 123 and the disc 124, the output of the photodetector 123a provided on the plate 123 becomes maximum. By knowing the output of the photodetector 123a, it is possible to confirm that the optical path has been set correctly. A plate 125 having a long hole for passing the scanning beam on the surface of the optical stage 107 between the imaging lens 114 and the photosensitive drum 102 is arranged such that the center of the short side of the long hole is aligned with the scanning plane of the imaging lens 114. They are mechanically positioned and fixed so that their centers coincide. The phosphor is disposed around the elongated hole, and the scanning beam is emitted from the phosphor on the plate 125.
The position on the surface is detected.

Next, the operation from receiving graphic/character information from a computer to producing a desired hard copy using the apparatus shown in this embodiment will be explained with reference to FIG. Information from the computer 201 is input into the interface circuit 202 of the apparatus in a predetermined format, either directly or via a storage medium such as a magnetic tape or a magnetic disk. Various instructions from the computer are decoded and executed by instruction execution circuit 204. Data is stored in data memory 203 in fixed amounts. In the case of character information, the data format is given as a binary code, and in the case of graphic information, it is data of image units that make up a figure, or data of lines that make up a figure (so-called vector data). ). These modes are specified in advance of the data, and the instruction execution circuit 204 controls the data memory 20 to process the data according to the specified mode.
3. Control the line data generator 206. A line data generator 206 generates final data for one scan line.

That is, when data is given in character code,
Either read the character pattern from the character generator 205, line up the character pattern for one line and buffer it, or buffer the character code for one line and sequentially read the character pattern from the character generator 205 and buffer it for one scan line. The final data for modulating the laser beam is sequentially created. Even when the data is graphic information, the data is converted into scan line data to create final data for sequentially modulating the laser beam for one scan line. The data for one scan line is 1
The signal is alternately inputted under the control of a buffer switch control circuit 209 to a first line buffer 207 and a second line buffer 208, which are composed of a shift register or the like having a number of bits equal to the number of pixels for a scan line.

Furthermore, the data of the first line buffer 207 and the second line buffer 208 are transmitted to the beam detector 11.
Using the beam detection signal from 6 (shown in FIG. 5) as a trigger signal, one bit for one scan line is sequentially read out and applied to the laser modulation control circuit 211. While the reflective surface of the scanner 113 scans the photosensitive drum along a line perpendicular to the rotation direction,
A signal 211a from the laser modulation control circuit 211 is transmitted to the laser oscillator 108 via the temperature control circuit 216.
A bright and dark pattern of one scan line is applied to the photosensitive drum 102. 1st and 2nd
Data is read out alternately from line buffers 207 and 208 under the control of buffer switch control circuit 209. That is, while reading from one line buffer, writing is occurring to the other line buffer. This method allows data to be applied to the modulator without fail when the scanner 112 sweeps over the photosensitive drum 102 with very short intervals between the first and subsequent scans. While scanning one scan line, the photosensitive drum 102 continues to rotate at a constant speed and moves by an appropriate scan line interval.

Further, the printer control circuit 212 that controls the printing unit 101 includes an instruction execution circuit 204.
When a start command is received from , printer operation is started and printer ready signal 212
a, a scan ready 213a derived from a scanner drive circuit 213 that controls the scanner 113, and a laser operating temperature ready 216a derived from a temperature control circuit 216, which are returned to the instruction execution circuit 204. When a signal is applied to the laser oscillator 108 and the first data of one page is written to the photosensitive drum, the timing is set so that the written data is transferred exactly to the beginning of the page at the transfer position. Then, the plain paper recording paper 106a is sent out by the paper feeding device 106.

Thus, the character/graphic information from the computer 201 is output as a clear hard copy on plain paper.

Next, the operation of the temperature control circuit 216 will be explained.

In Figures 7 and 8, TR1 and TR2 are switching elements, here switching transistors, TR3, TR4, TR5, and TR6 are transistors, INV is an inverter, MSM1, MSM
2 is monostable multivibrator, L is LD element SH
1 is sampling and hold circuit, AMP1
is a differential amplifier, R1 and R2 are resistors, LS1 is a voltage level selection circuit, and PD is a Peltier element.

Dot signal 2 from laser modulation control circuit 211
11a is applied to input terminal a. When the pulse modulation signal 211a is at the "1" level, the transistor TR1 is turned on, a current capable of laser oscillation flows through the LD element L, and the LD element L performs laser oscillation to perform recording on the photosensitive drum. Furthermore, when the signal 211a is at the "0" level, the transistor TR1 is not turned on and the transistor TR1 is turned on via the inverter INV.
2 turns on. Therefore, a preset current flows through the LD element L. The resistor R1 functions to lower the current value flowing through the LD element L than when laser oscillation is performed. For this reason, the LD element L functions as a normal diode. The forward voltage applied to the LD element L is correlated to the junction temperature of the LD element L. A voltage Ed that is the sum of this forward voltage, a voltage drop across the resistor R1 due to a preset current, and a saturated collector-emitter voltage of the transistor TR2 is input to a terminal d of the sampling and hold circuit SH1. On the other hand, the pulse modulation signal 211a is input as a sampling signal to the C terminal of the sampling and hold circuit SH1 via the inverter INV and the monostable multivibrators MSM1 and MSM2. This signal waveform is indicated by Ec, and the sampling signal Ec is a signal with a pulse interval ω ₂ delayed by a time ω ₁ from the fall time of the signal 211a. Said circuit
SH1 detects the voltage Ed when the sampling signal Ec is applied, outputs the voltage Ed from the output terminal e, and holds the voltage Ed until the next sampling signal Ec is applied. This timekeeping voltage waveform, ie, the output voltage Ef from the terminal e, is input to the input terminal f of the differential amplifier AMP1. A preset voltage Eg is input to the other input terminal g of the amplifier AMP1. This set voltage Eg is variable by a variable resistor R2. Here, when a constant current is applied, the forward voltage of the LD element L is lower as the junction temperature is higher, and the lower the junction temperature is, the higher the output is. Therefore, if the output of the LD element L decreases due to aging, the above setting It is also possible to lower the voltage Eg and keep the output stable. Further, by providing a laser output detection means and a control circuit, it is possible to automatically control the set voltage Eg and keep the output stable.

The amplifier AMP2 has two output terminals h and i, and the output voltages Eh and Ei are in opposite phases. In other words, the holding voltage is higher than the set voltage Eg.
When Ef is higher, the terminal voltage Eh of the output terminal h becomes positive, and the terminal voltage Ei of the output terminal i becomes the voltage Eh.
The absolute value is the same, but the voltage is negative. Conversely, if the set voltage Eg is higher than the holding voltage Ef, the voltage Ei
becomes positive and voltage Eh becomes negative. First, when the junction temperature of the LD element L becomes higher than the standard operating temperature, the forward voltage increases, the holding voltage Ef becomes higher than the set voltage Eg, the voltage Eh becomes positive, and the voltage Ei becomes negative.
As a result, transistors TR4 and TR5 turn on, and current flows through the Peltier device PD in the direction of arrow j.
Cool the LD element L. Conversely, when the junction temperature of the LD element L becomes lower, the holding voltage Ef becomes lower than the set voltage Fg, the voltage Eh becomes negative, and the voltage Ei becomes positive. As a result transistors TR3 and TR6
turns on, current flows through the Peltier element PD in the direction of arrow k, and heats the LD element L. The temperature of the LD element L is controlled by the method described above.

Next, the control timing will be explained using the time chart shown in FIG. In Fig. 8, the horizontal axis represents the time axis, and the vertical axis of DP represents the laser beam applied to the photosensitive drum 10 by the galvanomirror scanner.
2, PO is approximately the center position of the photosensitive drum 102, and P1 is the center position of the photosensitive drum 102.
and P2 indicates the maximum displacement position of the laser beam on the photosensitive drum 102. P3 to P4 are beam position detection mirrors 11 on the photosensitive drum 102
5, and the output signal BP of the beam position detection device 116 is output during the time when the beam hits the mirror, for example, from time T ₂ to time T ₃ . P5 to P
Reference numeral 6 indicates the position where the image signal is actually recorded on the photosensitive drum 102 by the beam, and the recording is performed, for example, between times T4 and T5.

In this embodiment, when the sampling signal Ec is input to the circuit SH1 when the LD element L is not oscillating, that is, when the voltage Ed is at the el level, ω _1, the temperature of the junction of the LD element L is controlled by detecting the beam position after the LD element L finishes recording _one scanning line. It is also possible to detect the temperature of the junction of the LD element only until time _T2 when oscillation starts. This detects that the direction of the current flowing through the galvano mirror scanner is reversed at position P ₂ on the drum,
The temperature of the junction of the LD element is detected by inputting the detection signal to the circuit SH1 as a sampling signal.

It is also possible to detect the junction temperature only from time _T3 when the LD element stops laser oscillation for beam position detection to time _T4 when recording for one scanning line is started. This is possible by inputting the sampling signal to the circuit SH1 after a time ω ₁ has elapsed from the fall time T ₃ of the beam position detection signal BP. Furthermore, in this embodiment, the junction temperature is detected when the voltage Ed is at the el level, but the junction temperature of the LD element L is also detected when the voltage Ed is at the eh level, that is, when the LD element L is performing laser oscillation. It is also possible to do so. This is possible by switching the timing so that the sampling signal is input to the circuit SH1 when the voltage Ed is at the eh level.

Next, the operation of the laser recording apparatus after it is powered on will be described with reference to FIGS. 7 and 9. Immediately after the power is turned on, the junction temperature of the LD element L is unknown, so if laser recording is performed as it is, the beam intensity will fluctuate greatly. To prevent this, input the temperature ready detection signal Sq from terminal q. This signal is designed to repeatedly generate a pulse with a pulse width ω ₃ at time T ₀₀ immediately after the power is turned on. At this time, the laser pulse modulation signal 211a is at terminal a.
is not entered. Therefore, transistor TR1
is not turned on and the LD element L does not oscillate. Further, since the transistor TR2 is turned on only when the pulse of the signal Sq is applied, a voltage Ed correlated to the junction temperature of the LD element L is inputted to the terminal d of the sampling and hold circuit SH1. On the other hand, the pulse of the signal Sq is a monostable multivibrator.
The sampling signal EC is inputted to the terminal C of the circuit SH1 via MSM1 and MSM2. The circuit SH1 converts the voltage Ed when the pulse of the sampling signal Ec starts to the next sampling signal Ec.
Hold until the pulse is generated. This holding voltage waveform is indicated by Ef and is the input terminal f of the differential amplifier AMP1.
is input. A preset voltage Eg is input to the other input terminal g of the amplifier AMP1, and the amplifier AMP1 maintains a holding voltage Ef.
The voltage difference between Eg and set voltage Eg is amplified and output from output terminals h and i. As mentioned above, the amplifier
The output voltages Eh and Ei of AMP1 have opposite phases. When the holding voltage Ef differs from the set voltage Eg at time T ₀₁ or T ₀₂ , the voltage level selection circuit LS1 connected to the output terminal h does not output the laser operating temperature ready signal 216a. That is, the circuit
LS1 does not output the ready signal 216a unless the absolute value of the output voltage Eh falls within a preset tolerance range. When the output voltage Eh reaches a level within the permissible range, for example at time T ₀₃ , the ready signal 216a is output and transmitted to the instruction execution circuit 204. After the power is turned on, the LD element L is cooled or heated by the Peltier element PD until the time _T03 , so that the temperature of the junction of the LD element L approaches the laser operating temperature. When the ready signal 216a is output and transmitted to the instruction execution circuit, an image signal is recorded on the photosensitive drum 102 by the method described above.

Next, other embodiments of the present invention will be described.

In the laser recording device and temperature control circuit described above, data for one scan line was laser recorded using a number of bits equal to the number of pixels for one scan line. , Line Batsuhua 207,
It is also possible to control the beam intensity by storing the information in a memory such as 208. Laser modulation circuit 2
Temperature control when a pulse modulation signal S1 and a beam intensity modulation signal S2 are input from No. 11 will be described below. Here, FIG. 10 shows the pulse modulation signal S
1 shows a temperature control circuit diagram when a beam intensity modulation signal S2 is input together with 1.

In Figures 10 and 11, TR7 and
TR8 is a switching element, here it is a switching transistor, TR9 is a transistor, AMP
2 is an amplifier, D is a diode, R3, R4, R
5, R6, R7, R8, R9, and R10 represent resistances, and those having the same function as in the temperature control circuit diagram of FIG. 5 are marked with a dash "'".

The beam intensity modulation signal S2 controls the current flowing through the LD element when the laser is oscillating, thereby controlling the oscillation intensity. First, when the pulse modulation signal S1 is at the "1" level, the signal S1 passes through the inverter INV', so the transistors TR7 and TR8 are not turned on. On the other hand, the intensity modulation signal S
2 is amplified by amplifier AMP2 and transmitted to point u. Here, it is assumed that the potential at point u does not exceed the bias voltage _V4 of transistor TR7. Since the transistor TR7 is in an off state, the potential Ev at point v is equal to the potential at point u, transistor TR9 is turned on, and a current sufficient to perform laser oscillation flows through the LD element L', causing the LD element L' to perform laser oscillation. be.
The amount of current flowing through the LD element L' is controlled by the base voltage Ev of the transistor TR9. Voltage Ev is point u
Therefore, the amount of current flowing through the LD element L' is ultimately controlled by the beam intensity modulation signal.

Next, the operation when the pulse modulation signal S1 is at the "0" level, that is, when the LD element L' is not oscillating, will be described.

Since the pulse modulation signal S1 passes through the inverter INV, the transistors TR7 and TR8 are turned on.
When the transistor TR7 is turned on, the potential at point v becomes almost 0, so the transistor TR9 is not turned on. Also, the signal 211a passed through the inverter INV'
are monostable multivibrator MSM1, MSM2
Sampling and hold circuit through SH
It is input as a sampling signal Ec' to the c' terminal of 1'. When transistor TR8 turns on, the LD element
A preset current flows through L′, and LD
Element L′ does not oscillate as a laser and functions as an ordinary diode. The forward voltage of LD element L′ is
Correlating with the junction temperature of L', the voltage Ed', which is the sum of the forward voltage, the voltage drop across the resistor R8, and the saturated collector-emitter voltage of the transistor TR8, is input to the sampling-and-hold circuit SH1'. This is as stated when explaining FIG.

Since the operation of the temperature control circuit shown in FIG. 10 is exactly the same as that described in FIG. 7, the description thereof will be omitted here. Furthermore, since the temperature detection timing is completely the same, it will be omitted.

As explained above, according to this embodiment, it is possible to directly and easily detect the junction temperature of the LD element, and to determine the thermal resistance from the temperature control element, such as a Peltier element, to the LD element and further to the junction. It is possible to always keep the junction temperature constant regardless of the temperature. Furthermore, since there is no need to use a temperature sensing element such as a thermistor, the device can be made smaller and simpler, leading to lower costs. Moreover, the timing of humidity control is not delayed due to the response time of the temperature sensing element. When the present invention is applied to a recording device using a semiconductor laser, it is possible to record on a recording medium such as a photosensitive drum with a beam of stable output.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a semiconductor laser device, FIG. 2 is a perspective view of a double heterostructure semiconductor laser device,
FIG. 3 is a partially cutaway perspective view of a conventional semiconductor laser generator, FIG. 4 is an explanatory diagram of temperature control in this embodiment, FIG. 5 is a perspective view of a recording device using the present invention, and FIG. The figure is a block diagram of the control system of the recording device shown in FIG. 5, FIG. 7 is a temperature control circuit diagram of the recording device shown in FIG. 5, FIG. 8 is a timing chart of each part of the control circuit of FIG. 7, and FIG. 7 is a timing chart of each part of the control circuit of FIG. 7 immediately after power is turned on, FIG. 10 is a circuit diagram of another embodiment of the temperature control circuit, and FIG. 11 is a timing chart of each part of the control circuit of FIG. 10. show. In the figure, 102 is a photosensitive drum, 108 is a laser generator, 113 is a galvanomirror scanner, 1
15 is a beam position detection mirror, 116 is a beam position detector, 211 is a laser modulation control circuit, 216
216a is a temperature control circuit, 216a is a laser operating temperature ready signal, L and L' are LD elements, PD and PD' are Peltier elements, and SH1 and SH1' are sampling and hold circuits, respectively.

Claims (1)

[Claims] 1. A semiconductor laser, means for supplying a drive current to the semiconductor laser, a detection means for detecting the temperature of the semiconductor laser, and controlling the temperature of the semiconductor laser according to a detection output of the detection means. a control means, and before the start of recording by the semiconductor laser, the supply means supplies the driving current at a predetermined timing and the control means performs temperature control, and the detection output of the detection means is set within a predetermined range. An image forming apparatus comprising: means for outputting a permission signal for permitting the semiconductor laser to start recording an image when the semiconductor laser is activated.