JP2000263847A - Image-forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize highly accurate temperature regulation with low ripple by performing temperature regulation only in a specified region of main scan based on the temperature of a laser unit if the laser unit reaches a specified temperature lower than a target level when it is controlled to the target temperature. SOLUTION: When an image is formed, an image write timing control circuit 101 drives a semiconductor laser 201 to modulate depending on magenta, cyan, yellow and black image signals. A photosensitive drum 105 is scanned with a laser beam through a polygon mirror 103 and an f-θ lens 104 and an electrostatic latent image is formed on the photosensitive drum 105. A thermistor defects surface temperature of the semiconductor laser 201 and a heater is controlled such that the semiconductor laser 201 has a regulated temperature. When the unit 201 reaches a specified temperature lower than a target level, temperature regulation is performed only in a specified region of main scan which is switched depending on the temperature of the semiconductor laser 201.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus provided with a laser scanning device.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic image forming apparatus, a laser beam is scanned over a photoreceptor, and the intensity of the laser beam and the lighting time for each pixel are modulated according to the value of an input signal. An electrostatic latent image is formed on the photoreceptor. The electrostatic latent image on the photoreceptor is developed by a developing device and is transferred to a recording medium, fixed, or transferred once to an intermediate transfer member, and then transferred to a recording medium and fixed through an electrophotographic process to be finally output. It becomes an image.

[0003] The semiconductor laser has a function of detecting the light emission intensity of the laser using a photodiode built in the unit and outputting a current corresponding to the intensity. This is fed back to the control circuit of the laser to control the emission intensity to be always a predetermined value.
ontorol) is commonly used. APC using FIG.
An example of the operation will be briefly described.

The current flowing through the semiconductor laser 201 is roughly classified into two types, a driving current by controlling the transistor 203 and a bias current by controlling the transistor 204. The bias current is set to a value immediately before the semiconductor laser 201 emits laser light, that is, a value near a threshold current, so that the bias current always flows through the semiconductor laser 201. This bias current is controlled so that the light emission intensity of the laser becomes constant. The drive current is set to a fixed value such that the semiconductor laser 201 emits laser light. At the time of image formation, a pulse signal corresponding to the image is applied to the base of the transistor 203, and is determined by the pulse peak value and the resistor 205. Is the drive current.

The photodiode 202 is a semiconductor laser 2
01 provided in the same case as the semiconductor laser 201.
A part of the laser light is incident. The photodiode 202 on which the laser light is incident outputs a current corresponding to the intensity of the laser light. The current / voltage converter 207 converts the output current of the photodiode 202 into a voltage signal having a predetermined amplification factor. A switch 208 is controlled by a control unit (not shown).
Turned on during C control. When the switch 208 is turned on, the hold capacitor 209 outputs the current-to-voltage converter 207.
Is accumulated so as to be equal to the output voltage. The adder 210 operates from the predetermined voltage value V ₀ to the hold capacitor 2.
The hold voltage value V ₁ of the 09 outputs a voltage value obtained by subtracting. The output of the adder is applied to the base of the transistor 204 via the buffer amplifier 211, and the voltage value and the current value determined by the resistor 206 become the bias current.

As described above, the emission intensity of the semiconductor laser 201 is determined by the sum of the driving current and the bias current. FIG.
In the method (1), since the drive current is a fixed value, the intensity fluctuation of the laser beam due to a temperature change or a temporal change is performed by controlling a bias current.

Next, the operation of the APC will be described.

At the time of image formation, the semiconductor laser 201 is driven by a laser drive signal 301 shown in FIG. Where BD
At the time of lighting, the laser continues to be turned on for a predetermined time in the non-image area in order to generate a horizontal synchronization signal serving as a reference for writing a horizontal image signal. In synchronization with the lighting of the BD, the control unit sends the APC mode signal 302
Turn on 8. The photodiode 202 receives the laser beam of the semiconductor laser 201 when the BD is turned on, and outputs a current value corresponding to the laser beam. The output converted to a voltage signal by the current-to-voltage converter 207 is stored as an electric charge in the hold capacitor 209 via the switch 208 in the ON state.
During D lighting, the output voltage is equal to the output voltage of the current-voltage converter 207. The switch 208 is opened again a predetermined time earlier than the end of the BD lighting, but the output voltage of the current-voltage converter 207 is held by the hold capacitor 209. A predetermined voltage V ₀ is input to one of two inputs of the adder 210. On the other hand, the voltage value V ₁ held by the hold capacitor 209 is input. The adder 210 outputs (V ₀ −V ₁ ). The bias current is determined by (V ₀ −V ₁ ). That is, the semiconductor laser 201
Is smaller than usual, V ₁ is small and (V ₀
−V ₁ ) increases, and the bias current increases. Also, if the reverse to the emission intensity is greater than normal, V ₁ is large, has become (V ₀ -V ₁₎ becomes large, the bias current decreases.

However, even if the light emission intensity is the same due to the temperature characteristic of the light emission intensity detection photodiode, the detection current varies due to the ambient temperature of the laser unit. As a result, there is a problem that the light emission intensity of the laser changes depending on the ambient temperature, which affects an image.

Therefore, in order to solve the above-mentioned problem, the temperature may be adjusted by a heater or the like in order to keep the semiconductor laser at a predetermined temperature. FIG. 1 shows a semiconductor laser temperature adjusting mechanism mounted. A unit 201 including a semiconductor laser and a photodiode is fixed to a disk-shaped base 12 in such a manner that electrodes are passed through holes formed in the center of the base 12. A thermistor 14 for detecting the surface temperature of the case is fixed to the case of the semiconductor laser unit 201 so as to contact the case. The control unit 400 shown in FIG. 4 is connected to both ends of the thermistor 14. Base 12
, A disc-shaped on-surface heater 13 is fixed so as to contact the base 12. This is a position where the vicinity of the semiconductor laser unit 201 fixed to the base 12 is heated. Since the base 12 is made of a material having sufficiently good heat conduction, the heater 13
It is possible to heat the case 1 immediately. The heater 13 is connected to a power supply in the control unit 400 as shown in FIG. 4, and the power supply can be turned on / off by the control unit 400.

That is, when the case surface temperature of the semiconductor laser unit 201 detected by the thermistor 14 is lower than a predetermined value, the power supply for the heater is turned on, and when it is higher than the predetermined value, the power supply for the heater is turned off. Also, heater 1
The reference temperature for controlling 3 is determined, for example, as follows. Assuming that the difference between the temperature at the place where the semiconductor laser unit 201 is mounted in the device and the ambient temperature is Δα (° C.), the control temperature T is T = k + Δα (the maximum temperature k (° C.) in the operating temperature range of the device. ° C).

When k = 35 (° C.) and Δα = 5 (° C.), the control temperature T of the semiconductor laser 201 is T = 3
5 + 5 ° C.

FIG. 4 shows a control section 400 of the heater. 5V
Is divided by the thermistor 14 and the resistor 405, and the divided voltage is compared with the reference voltage generated by the resistors 401 and 402 by the comparator 403. Since the resistance value of the thermistor 14 changes according to the case surface temperature of the semiconductor laser unit 201, the voltage divided by the thermistor 403 changes according to the temperature of the semiconductor laser 201. The values of the resistors 401, 402, and 405 are determined according to the thermistor 14 when the semiconductor laser 201 reaches the control temperature T.
And the voltage divided by the resistor 405 and the reference voltage are set to be the same. When the temperature falls below the control temperature T, the comparator 403 turns on the transistor 404 and the heater 13
Is supplied with power. When the voltage exceeds the control voltage T, the comparator 403 turns off the transistor 404 and the heater 13
The temperature adjustment is performed by shutting off the power supply.

FIG. 5 is a graph showing an example of a temperature change of an output current when a photodiode built in a semiconductor laser unit detects laser light having a certain light emission intensity.

When the operating temperature range of the device is 10 ° C. to 35 ° C., the temperature rise at the semiconductor laser mounting position is reduced by 5 ° C.
Then, the operating temperature range of the semiconductor laser is 15 ° C. to 4 ° C.
0 ° C. According to the characteristics shown in FIG. 5, the output current fluctuation of the photodiode in this range has a maximum fluctuation of about 3% based on the measured value at 25 ° C. When the temperature adjustment control value of the heater is set to 40 ° C. and the allowable range is set to ± 5 ° C., the output current fluctuation of the photodiode can be suppressed within a maximum of about 1% based on the measured value at 40 ° C.

[0016]

Conventionally, laser temperature adjustment has been performed regardless of whether an image is being formed. Since the current path of the heater is arranged near the current path of the laser, induction by a relatively large current flowing when the heater is turned on or off may affect the laser drive current. Specifically, the disturbance of the laser drive current for this guidance disturbs the laser light waveform that determines the image quality.
That is, since the heater is repeatedly turned off and on during image formation, there is a possibility that the current of the heater may affect the image.

Further, the temperature adjustment is not performed only for the laser, but for the base and the lens barrel to which the heater is attached. For this reason, the heat capacity is increased, the response speed of the heat is reduced, and as a result, the cycle of turning on and off the heater is lengthened, and the laser temperature may have a large ripple component. FIG. 14 shows this state. Assuming that the control temperature is T, a large ripple component exists even after reaching T as shown in FIG. This ripple component causes a change in the laser power and degrades the image quality.

According to the present invention, there is provided an image forming apparatus capable of performing high-precision temperature adjustment with a small amount of ripple, eliminating the influence of heater on / off due to temperature adjustment on image formation, and performing stable image formation with a laser light amount. The purpose is to provide.

[0019]

An image forming apparatus according to the present invention comprises: a photosensitive member for forming an image by irradiating a laser beam;
A laser unit including a laser light source that emits the laser light by a drive current and an optical sensor that monitors the amount of the laser light; a laser control unit that modulates the laser light according to an image signal; and an output of the optical sensor. A laser light amount correction unit that controls a laser drive current based on the laser light, a scanning unit that performs a main scan of the area including the surface of the photoconductor with the laser light, and a scan start reference signal by detecting the laser light that is main-scanned. Scanning start signal generating means for generating the laser unit, further comprising a temperature control means for controlling the temperature of the laser unit to a target temperature, the temperature control means the laser unit is higher than the target temperature When a low predetermined temperature is reached, temperature control is performed only in a specific area of the main scan determined by the scan start reference signal, And it switches the constant region by the temperature of the laser unit.

Further, in the image forming apparatus according to the present invention, in the above-described image forming apparatus, the specific area is switched within the non-image forming section according to the temperature of the laser unit.

Further, an image forming apparatus according to the present invention is characterized in that in the above-described image forming apparatus, the temperature control means includes a heating means.

Further, in the image forming apparatus according to the present invention, in the above-mentioned image forming apparatus, the temperature control means includes a cooling means.

Further, in the image forming apparatus according to the present invention, in the above-described image forming apparatus, the temperature control means always performs temperature control until the laser unit reaches a predetermined temperature lower than the target temperature. I do.

[0024]

FIG. 6 is an example of the configuration of a printer unit of an image forming apparatus according to the present invention, and FIG. 7 is a timing chart thereof. 6, an image signal sent from an external device such as an image scanner or a computer (not shown) is sent to an image writing timing control circuit 101. The image writing timing control circuit 101 includes magenta (M),
The semiconductor laser 201 is modulated and driven according to image signals of cyan (C), yellow (Y), and black (BK). The laser light is reflected by the rotating polygon mirror 103 and f
The fθ correction is performed by the −θ lens 104, and the photosensitive drum 1
05 is scanned. Thus, an electrostatic latent image is formed on the photosensitive drum 105.

The photosensitive drum 105 is driven to rotate clockwise by a drum motor 115 via a gear belt 116, and the transfer drum 108 is synchronized with the photosensitive drum 105 because the transfer drum 108 is connected to the photosensitive drum 105 via a gear (not shown). It is driven to rotate in the direction of the counterclockwise arrow (sub running). A drum motor 115 that rotationally drives the photosensitive drum 105 is rotationally driven by dividing a clock of an oscillator 112 by a frequency dividing circuit 117 and sending the divided clock to a PLL circuit 118 as a motor driving pulse (reference CLK). The PLL circuit 117 detects a phase difference and a frequency deviation between the FG pulse and the reference CLK so that the phase of the motor FG pulse from the drum motor 115 matches the phase of the reference CLK, compares them, and compares them.
PLL control for controlling the drive voltage to 5 is performed.

The polygon motor 106 is rotationally driven by dividing the frequency of the clock of the oscillator 112 by the frequency dividing circuit 113 and sending it to the PLL circuit 114 as a motor driving pulse (reference CLK). The PLL circuit 114 detects a phase difference and a frequency deviation between the FG pulse and the reference CLK so that the phase of the motor FG pulse from the polygon motor matches the phase of the reference CLK, and compares them to control the drive voltage to the polygon motor 106. Is performed. BD sensor 107
Is provided near the scanning start position of one line of laser light,
The line scanning of the laser beam is detected, and a scanning start reference signal (BD signal) of each line having the same cycle as shown in FIG. 7B is generated. Magenta (M), cyan (C), yellow (Y), and black (BK) developing units (not shown) are provided around the photoconductor 105, and four developing units are provided while the photosensitive drum 105 rotates four times. Alternately contact the photosensitive drum 105 and develop with toner corresponding to the M, C, Y, and BK electrostatic latent images formed on the photosensitive drum. Recording paper 109 fed from a paper cassette (not shown) is wound around a transfer drum 108, and a toner image developed by a developing device is transferred. In the transfer drum 108, there is a sensor 110 for generating an ITOP signal indicating the leading end position of the recording paper 109 on the transfer drum 108, and a flag 111 fixed in the transfer drum 108 by rotation of the transfer drum 108 is detected by the sensor 11
0, so that ITO for each color as shown in FIG.
A P signal is created. After the four colors of M, C, Y, and BK are sequentially transferred in this manner, the sheet passes through a fixing unit (not shown) and is discharged.

Since the temperature adjusting mechanism of the semiconductor laser is the same as that of the conventional example shown in FIG. 1, its explanation is omitted, and the same reference numerals are used in this embodiment. In the present embodiment, a three-stage temperature adjustment method is switched according to the temperature of the semiconductor laser. That is, assuming that the temperature adjustment set temperature is T, the heater is always turned on up to a temperature T ′, which is a value slightly smaller than the temperature ripple component when the semiconductor laser 201 reaches T from the temperature adjustment temperature T. When the temperature becomes equal to or higher than the temperature T ', a predetermined logic H which can be set in synchronization with the BD lighting until the temperature T is reached.
Turn on the heater in the section. This logical H section is longer when the temperature of the laser is considerably lower than T, and shorter when the temperature of the laser approaches T. That is, the length of the logic H section for turning on the heater is changed according to the temperature. When the temperature reaches the temperature T, thereafter, the heater is turned off if the temperature is equal to or higher than the temperature T, and the heater is turned on only in a settable logic H section synchronized with the BD if the temperature is equal to or lower than the temperature T, thereby performing temperature adjustment.

As a result, as shown in FIG. 11, the temperature reaches the temperature T 'with a steep gradient up to the temperature T', reaches the temperature T with a gentle gradient up to the temperature T, and is thereafter maintained at the temperature T with a small ripple. When the temperature is adjusted only to turn on the heater in the logic H section of the fixed area synchronized with the BD lighting, the temperature changes as shown in FIG. This is because when the image is not formed or in the non-image area during the image formation, the laser is turned off or only the bias is turned on, so that the amount of temperature rise by the laser drive is small, and the ripple component is smaller than that during the image formation. It becomes large or the time until the temperature converges becomes long.

During the image formation, the influence of the heater ON / OFF can be eliminated by setting a predetermined logical H section which can be set in synchronization with the BD lighting around the non-image portion of the main scanning. That is, as shown in the timing chart of FIG. 10, image forming / forming at the maximum recording paper size determined in synchronization with BD lighting /
By outputting the logic H only in the non-image area such as A or B in the non-image area, that is, by enabling the temperature adjustment, the influence of heater ON / OFF can be eliminated. Since the heater ON time is short and the temperature of the laser does not reach the set temperature T, there is no problem if the recording paper is small even if this temperature adjustment section (logical H section) slightly enters the image area as shown at C. Is a marginal area and is not likely to cause a problem.

FIG. 8 shows a temperature adjustment control section of the semiconductor laser of this embodiment. First, control until reaching the temperature T 'will be described. Since the resistance value of the thermistor 14 changes according to the case surface temperature of the semiconductor laser 201, the voltage divided by the thermistor 14 and the resistor 814 changes according to the temperature of the semiconductor laser 201. The values of the resistors 815, 816, 817 are
When the temperature of the thermistor 14 becomes equal to the temperature T 'obtained by subtracting a value slightly larger than the temperature ripple component when the temperature 1 reaches the temperature T from the temperature regulation temperature T, the voltage divided by the thermistor 14 and the resistor 814 is equal to the reference voltage. Is set to Comparator 815
Until the temperature T ′, the transistor 814 is kept turned on to output the logic H to the OR gate 808, and power is supplied to the heater 13.

Next, the temperatures T 'to T will be described. The values of the resistors 811 and 812 are
Is set such that the voltage divided by the thermistor 14 and the resistor 815 when the temperature reaches the temperature adjustment temperature T becomes equal to the reference voltage. Therefore, the comparator 813 continues to output the logic H to the AND gate 807 until the temperature reaches the temperature adjustment temperature T. Therefore, power is supplied to the heater 13 only when the output of the inverter 806 that outputs a settable predetermined logical H section synchronized with the BD lighting is H.

The output in a predetermined settable logic H section in synchronization with the BD lighting is produced as follows. The counter 801 counts the clock from the crystal oscillator 802, and when an image is formed, the BD sensor 1 selected by the selector 820 according to an image forming signal from a control unit (not shown).
07 is reset by the main scanning start reference signal (BD). Since the BD signal is not output except during image formation, the BD signal is reset by a ripple carry from a counter 821 that counts a clock output from the oscillator 802. The counter 821 is preset so that ripple carry is generated at substantially the same cycle as the BD cycle. The value of the counter 801 is calculated by the comparators 803 and 8
04 is input. A value determined according to the area in the main scanning direction in which the heater is turned on is input to the comparators 803 and 804 by the heater-on area determining unit 810.

The analog voltage divided by the resistor 814 and the thermistor 14 is supplied to the heater-on area determination section 810 by A.
The value digitized by the / D converter 809 is input. The heater-on area determining unit 810 determines whether the semiconductor laser 20
The set value is output to the comparators 803 and 804 in synchronization with the BD signal so that the heater-on region is changed according to the temperature of 1. The heater-on area determining unit 810 includes, for example, an LUT
(Look Up Table) and outputs a value determined according to a digital value from the A / D converter 809 indicating the temperature of the semiconductor laser. An example of this LUT is shown below.

[0034]

[Table 1] If the laser case temperature is lower than T-5 ° C., the heater ON region is set to 60% of the BD cycle. Therefore, assuming that the comparators 803 and 804 are 8-bit inputs, 4Chex and B2hex are respectively input. If the laser case temperature is equal to or higher than T-5 and lower than T-2, the comparator 803 sets the heater ON region to 30% of the BD cycle.
And 804, 26 hex and D8 hex are input, respectively. If the laser case temperature is T-2 or more and less than T, 06h
If ex and F8hex are equal to or higher than T ° C., 00hex is input to both.

In the above, the value to be output to the comparators 803 and 804 is determined based on the absolute value of the temperature of the laser 201. However, the value to be output to the comparator may be determined while observing the absolute value and the variation width of the digital value.

The comparator 803 receives a set value indicating the starting point at which the main scanning heater is inhibited from being turned on, and the comparator 804 receives a set value indicating the starting point at which the main scanning is turned on. The JK-FF 805 is set by the comparator 803 when the set value of the input B of the comparator 803 becomes equal to the value of the counter 801, and when the set value of the input B of the comparator 804 becomes equal to the value of the counter 801. Comparator 804
, The logic H is maintained in the heater-on prohibition region in the main scanning. Inverter 806 is J
By inverting the signal from the K-FF 805, the logic H is output to the AND gate 807 in the heater-on area in the main scanning.
Output to In this way, a settable predetermined logical H section synchronized with the BD lighting is created.

FIG. 9 is a timing chart of a settable predetermined logical H section in synchronization with the BD lighting during image formation. When the BD signal rises, the counter 801 counts the clock. When the counter value becomes equal to the set value A indicating the start point at which the scanning temperature adjustment is prohibited, the comparator 803 outputs a pulse to start the main scanning temperature adjustment. When the set value B representing the point becomes the same, the comparator 804 outputs a pulse. JK-FF805
Is set and reset by this output, and outputs a logic H during this time. Since the output of the JK-FF is inverted by the inverter 806, the heater can be turned on only in the temperature adjustment permission area.

Once the temperature reaches the temperature T and becomes equal to or higher than the temperature adjustment temperature T, the comparator 813 outputs a logic L to the AND gate 807, and the power supply of the heater 13 is cut off. Heater 1
When the temperature of the laser 3 becomes lower than the temperature T by turning off the heater 3, the temperature is adjusted such that the heater is turned on in a predetermined logic H section that differs depending on the case temperature of the laser synchronized with the BD lighting.

FIG. 10 is a timing chart of a settable predetermined logical H section in synchronization with the BD lighting during image formation. The counter 801 is activated by the rising edge of the BD signal.
Counts the clock, and when the value becomes the same as the set value indicating the starting point at which the scanning heater is inhibited, the comparator 803 outputs a pulse, and becomes equal to the set value indicating the starting point at which the main scanning heater is turned on. The comparator 804 outputs a pulse. The JK-FF 805 is set and reset by this output, and outputs a logic H during this time. This J by the inverter 806
The output of the K-FF 805 is inverted. This is mainly for setting the non-image area of the main scan to the heater-on area.

FIG. 12 is a timing chart showing the transition state of the case temperature of the semiconductor laser 201 and the timing in which the region where the main scanning heater is turned on changes depending on the laser temperature. When the temperature of the laser is equal to or lower than T-5 ° C., a logic H section (output of the inverter 806) for turning on the heater synchronized with the BD is 60% of the BD cycle. T- at T-5 ° C or higher
When the temperature is lower than 2 ° C., the logic H section (the output of the inverter 806) in which the heater synchronized with the BD is turned on is 30% of the BD cycle.
, And 5% at T-2 ° C or higher and lower than T ° C. That is, as the temperature approaches the temperature T, the logic H section (output of the inverter 806) in which the heater synchronized with the BD is turned on becomes shorter. When the temperature exceeds T, the output of the comparator 803, which inhibits the heater from being turned on, changes from logic H to L, and the heater 13 is turned off regardless of the output of the inverter 806.

In the above embodiment, the temperature is adjusted using the heater. However, a cooling unit using the Peltier effect can be used instead of the heater. In this case, the control temperature is set, for example, near the lower limit of the temperature range of the semiconductor laser 201.

As described above, once the temperature adjustment point is reached, the temperature is adjusted only in a part of one line in the main scanning, so that the heater can be turned on and off at a fast cycle, and as a result, the temperature can be adjusted more finely, that is, the ripple can be adjusted. Temperature adjustment can be performed.

Further, by setting the heater-on area at the center of the non-image area of the main scanning, the influence on the laser control due to the heater on-off can be eliminated, and an image can be formed with a stable laser light amount.

[0044]

As described above, by adjusting the temperature of the semiconductor laser at the time of image formation in synchronization with the main scanning start signal, it is possible to perform the temperature adjustment with a small amount of ripple components and high accuracy, and the influence of the temperature adjustment on and off of the heater. Is eliminated, and an image can be formed with a stable laser light amount.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a laser temperature adjusting mechanism according to the present invention and a conventional example.

FIG. 2 is a circuit diagram of a circuit for performing APC of a laser according to the present invention and a conventional example.

FIG. 3 is a timing chart showing the timing at which laser APC is performed in the present invention and the conventional example.

FIG. 4 is a circuit diagram of a laser temperature adjustment controller according to a conventional example.

FIG. 5 is a graph showing temperature characteristics of a photodiode built in a laser according to the present invention and a conventional example.

FIG. 6 is a conceptual diagram illustrating an image forming apparatus according to an embodiment of the present invention and a conventional example.

FIG. 7 shows a BD and an I according to an embodiment of the present invention and a conventional example.
It is a timing chart showing the timing of TOP.

FIG. 8 is a circuit diagram of a laser temperature adjustment control unit according to the embodiment of the present invention.

FIG. 9 is a timing chart showing timing along a main scanning image area of the laser temperature adjustment control unit according to the embodiment of the present invention.

FIG. 10 is a timing chart illustrating a laser temperature adjustable region according to an embodiment of the present invention.

FIG. 11 is a graph showing transition of laser temperature by laser temperature adjustment according to the embodiment of the present invention.

FIG. 12 is a diagram illustrating a state in which a heater-on area in main scanning changes depending on a laser temperature in the embodiment of the present invention.

FIG. 13 is a diagram illustrating a change in laser temperature when a heater is turned on in a logic H section only in a certain area synchronized with BD light emission according to an embodiment of the present invention.

FIG. 14 is a graph showing transition of laser temperature due to laser temperature adjustment according to a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 12 Base 13 Heater 14 Thermistor 15 Heater electrode 16 Collimator lens 17 Lens barrel 107 BD sensor 201 Semiconductor laser unit 801, 821 Counter 803, 804 Comparator 810 Heater ON area determination part 813, 815 Comparator 820 Selector

Claims (5)

[Claims] A laser unit comprising: a photoreceptor that forms an image by irradiating a laser beam; a laser light source that emits the laser beam by a driving current; and an optical sensor that monitors a light amount of the laser beam; Laser control means for modulating the laser light in response thereto; a laser light amount correction section for controlling the drive current based on the output of the optical sensor; and scanning means for main-scanning the laser light in an area including on the photoconductor. And a scanning start signal generating means for generating a scanning start reference signal by detecting the main scanning laser beam. A temperature control for controlling a temperature of the laser unit to a target temperature. The temperature control means starts the scanning when the laser unit reaches a predetermined temperature lower than the target temperature. It performed only in certain areas of the main scanning determined by quasi-signal, the image forming apparatus characterized by switching the specified region by the temperature of the laser unit. 2. The image forming apparatus according to claim 1, wherein the specific area is switched in the non-image forming section according to a temperature of the laser unit. 3. The image forming apparatus according to claim 1, wherein the temperature control unit includes a heating unit. 4. The image forming apparatus according to claim 1, wherein the temperature control unit includes a cooling unit. 5. The image according to claim 1, wherein the temperature control means always performs temperature control until the laser unit reaches a predetermined temperature lower than the target temperature. Forming equipment.