JP2002307751A - Image recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image recorder in which a high quality print image having no image defect (image quality defect), e.g. uneven density of image due to droop phenomenon, can be obtained even when a halftone image is formed. SOLUTION: Prior to recording specified image data, the time when a semiconductor laser (e.g. a laser diode) lights substantially continuously is calculated from that image data. When the calculated time is longer than a specified value, an extra automatic quantity of light regulating operation is added independently from a normal automatic quantity of light regulating operation. Consequently, output of optical beam being emitted from the semiconductor laser is kept at a substantially constant level.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image recording apparatus, and more particularly to an image recording apparatus for forming an electrostatic latent image on an image carrier by turning on / off a semiconductor laser in an exposure unit according to image data. Equipment related.

[0002]

2. Description of the Related Art In recent years, many image forming apparatuses such as printers use a laser diode. A laser beam is emitted from the laser diode based on a drive current for driving the laser diode.

[0003] In a laser diode, the light conversion efficiency, which is the efficiency of conversion from a drive current to laser light, is very sensitive to temperature, and the temperature dependence of the amount of laser light is large.
Specifically, of the driving current, energy that does not contribute to the emission of laser light is converted into heat. Due to this heat, the temperature of the laser diode itself increases, and a droop phenomenon, which is a phenomenon in which the amount of laser light emitted from the laser diode decreases, may occur.

In order to suppress the occurrence of such a droop phenomenon, in the technique described in Japanese Patent Application Laid-Open No. 5-83503 (hereinafter referred to as Prior Art 1), one continuous exposure time of a light source with respect to an exposure repetition cycle is taken. The ratio (duty) is 9
It is configured to be 0% or less, preferably 75% or less. In Prior Art 1, a light source having a large droop is exposed at a low duty, and a light source having a small droop is exposed at a high duty.

In the technique described in Japanese Patent Application Laid-Open No. 10-135558 (hereinafter referred to as Prior Art 2), prior to image recording of predetermined image data, an image within a certain range close to the image data is obtained. The bias current added to the drive current for recording data is controlled, and the light amount of the light beam is controlled to be substantially constant.

[0006]

In recent years, colorization and high image quality of printers have been advanced, and there is a demand for outputting various images. Often, the entire image area is light-colored, and a dark solid image is drawn thereon. In such an image, an image that is continuously lit during a halftone with a small duty is output when viewed in each scanning of the laser light. Regarding the operation after the continuous lighting, it is necessary to draw a halftone image in which the density unevenness of the image is easily detected due to the fluctuation of the laser light amount after the laser diode itself generates heat by the continuous lighting and the output decreases. Generally, in human vision, it is difficult to detect density unevenness of an image when a dark color image is drawn even if a decrease in laser light amount occurs. However, human vision has a feature that when a light-colored image such as a halftone is drawn, density unevenness of the image is easily detected due to a change in the amount of laser light. Therefore, immediately after the continuous lighting, a decrease in the amount of laser light occurs, and in a halftone image of a light color, density unevenness of the image due to a change in the amount of laser light is conspicuous. When a dark color image is drawn, the temperature of the laser diode rises, and then the temperature of the laser diode falls over time, and as a defect in image quality (image quality defect), the extremely pale color gradually becomes pale. It often changed, resulting in an image that looks like a tail.

In the prior art 1, when the light amount is finely adjusted by the pulse width modulation method, the ratio of the fineness of the fine adjustment is determined by how fine one pixel can be. At this time, since the duty can be used only up to 75%, it is not possible to express a halftone image smoothly, and the image quality is reduced. Even if the duty is 90%,
As compared with the case where the duty is 75%, the image quality is inevitably reduced, though the degree is different.

In the prior art 2, since the bias current is determined by the on / off time ratio of the image data, for example, when the duty is 90%, the on-off state does not easily occur even though the droop phenomenon hardly occurs. The droop correction for increasing the bias current is performed because the off-time ratio is high. Further, a circuit for calculating the on / off time ratio and a circuit for increasing / decreasing the bias current are required to be added.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and has high quality without image quality defects (image quality defects) such as uneven image density due to a droop phenomenon even when a halftone image is formed. An object of the present invention is to provide an image recording device capable of obtaining a print image.

[0010]

According to a first aspect of the present invention, there is provided an image recording apparatus for forming an electrostatic latent image on an image carrier by turning on / off a semiconductor laser in exposure means in accordance with image data. The apparatus is characterized in that an automatic light amount control operation is performed inside the image recording area, separately from a normal automatic light amount control operation performed outside the image recording area.

According to the first aspect of the present invention, the automatic light amount control operation is performed inside the image recording area, separately from the normal automatic light amount control operation performed outside the image recording area. As a result, it is possible to correct the light amount fluctuation in one scan, and it is possible to prevent an image quality defect (image quality defect) due to density unevenness in one scan.

According to a second aspect of the present invention, there is provided an image recording apparatus for forming an electrostatic latent image on an image carrier by turning on / off a semiconductor laser in an exposure unit according to image data. Prior to image recording, continuous lighting time measuring means for measuring the time of this image data to be lighted almost continuously, comparing means for comparing the measured continuous lighting time with a predetermined reference time, and continuous lighting time When the time is longer than the reference time, an additional means for newly adding an automatic light amount control operation separately from the normal automatic light amount control operation is provided.

According to the second aspect of the present invention, predetermined image data is converted from this image data prior to image recording.
The time during which the semiconductor laser (for example, a laser diode) is turned on almost continuously is calculated. When the time obtained by the above calculation is longer than a predetermined value, a new automatic light amount adjusting operation is added separately from the normal automatic light amount adjusting operation. As a result, the output of the light beam emitted from the semiconductor laser can be kept substantially constant, and the image quality defect due to the droop phenomenon can be prevented.

According to a third aspect of the present invention, in the second aspect of the present invention, there is further provided an analyzing means for analyzing the image data prior to the image recording of the image data, and the adding means comprises When it is determined that a halftone image continues after lighting, an automatic light amount control operation is added during the continuous lighting period.

According to the third aspect of the present invention, the image data is analyzed prior to the recording of the predetermined image data, and when it is determined that the halftone image continues after the continuous lighting, during the continuous lighting period. , An automatic light amount adjustment operation is added. Accordingly, since the automatic light amount adjustment operation is added only to the halftone image in which the image quality defect due to the droop phenomenon is easily detected, for example, it is possible to reduce the load on a controller that controls the automatic light amount adjustment operation.

According to a fourth aspect of the present invention, in the second or third aspect of the present invention, there is further provided a timing determining means for ending the added automatic light amount control operation simultaneously with the end of the continuous lighting. And

According to the fourth aspect of the present invention, the added automatic exposure adjusting operation is completed simultaneously with the end of the continuous lighting.
This makes it possible to operate the semiconductor light quantity fluctuation correction at an effective timing. Particularly, in the image recording area, when recording a halftone image after the semiconductor laser is continuously turned on, the output of the light beam emitted from the semiconductor laser is substantially constant before the recording of the halftone image is started. Therefore, it is possible to prevent image quality defects such as tail lines from occurring.

According to a fifth aspect of the present invention, in the second to fourth aspects, a temperature detecting means is provided near the semiconductor laser, and an automatic light amount control operation is added based on the detection result. It is characterized by further comprising means for changing a reference time to be compared by the comparing means for determination.

According to the present invention, the temperature near the semiconductor laser is detected. Based on the result of the detection,
The continuous lighting time of the automatic light amount adjustment operation addition determination is changed. Specifically, at a high temperature at which the droop phenomenon is likely to occur, the continuous lighting time used for the automatic light amount adjustment operation addition determination is shortened. This increases the number of times the automatic light amount adjustment operation is added per scan. For this reason, the output of the light beam emitted from the semiconductor laser can be kept substantially constant, and the image quality defect due to the droop phenomenon can be prevented.

According to a sixth aspect of the present invention, in accordance with the second to fifth aspects of the present invention, there is provided a semiconductor laser output detecting means, and an automatic light amount control operation additional determination is performed based on the detection result. Therefore, it is characterized by having means for changing the reference time.

According to the invention, the output of the semiconductor laser is detected. Based on the detection result, the continuous lighting time of the automatic light amount adjustment operation addition determination changes. Specifically, at a low output in which the droop phenomenon is likely to occur, the continuous lighting time of the automatic light amount adjustment operation addition determination is shortened.
This increases the number of times the automatic light amount adjustment operation is added per scan. For this reason, the output of the light beam emitted from the semiconductor laser can be kept substantially constant, and the image quality defect due to the droop phenomenon can be prevented.

[0022]

Embodiments of the present invention will be described below in detail with reference to the drawings. The present embodiment relates to a laser diode (Laser) incorporated in an image recording apparatus.
Diode, hereinafter abbreviated as LD. ) To which the present invention is applied.

FIG. 1 schematically shows an image recording apparatus 10 according to the present embodiment.

The image recording apparatus 10 includes an optical scanning device 12 for scanning a laser beam, and a photosensitive member 14 on which an electrostatic latent image is formed by the laser beam emitted from the optical scanning device 12. ing.

The optical scanning device 12 has a laser diode (Laser Diode) for emitting a laser beam.
16 (hereinafter, abbreviated as LD16).

The optical scanning device 12 includes the LD
A rotary polygon mirror 18 for deflecting the laser beam emitted from the light source 16 is provided.

Further, the optical scanning device 12 is provided with a reflection mirror 20 for reflecting the laser beam deflected by the rotary polygon mirror 18 toward the photosensitive member 14.

When the laser beam reflected by the reflection mirror 20 is irradiated on the photoconductor 14 while the photoconductor 14 is rotating in the direction of arrow A, an electrostatic latent image is formed. Has become.

In the vicinity of the surface of the photosensitive member 14 on which the electrostatic latent image is formed, a charging member 22 for charging the surface of the photosensitive member 14 on which the electrostatic latent image is formed is provided.

Toner is attached to an electrostatic latent image formed on the photosensitive member 14 at a position downstream of the position of the photosensitive member 14 in the direction of arrow A, which is the direction of rotation of the photosensitive member 14, and the electrostatic latent image is formed. A developing device 24 for developing the latent image is provided.

Further, the image recording apparatus 10 is provided with a transfer member 26 for transferring an image developed by using the toner on the photosensitive member 14 by the developing device 24.

Further, on the downstream side of the position of the developing device 24 in the direction of the arrow A, which is the rotation direction of the photosensitive member 14,
A transfer charging member 28 for transferring an image developed on the photoconductor 14 by the developing device 24 from the surface of the photoconductor 14 to the transfer member 26 is provided.

Further, after the toner is transferred to the transfer member 26, the toner remains on the photosensitive member 14 downstream of the position of the transfer charging member 28 in the direction of the arrow A which is the rotation direction of the photosensitive member 12. Cleaner 3 that removes toner
0 is provided.

Further, the image recording apparatus 10 is provided with a fixing device 32 for melting and fixing the toner to the transfer body 26.

The transfer member 26 on which the toner is fixed by the fixing device 32 is conveyed in the direction of arrow C, and is discharged outside the image recording apparatus 10.

All of these operations are controlled by a control device (not shown).

FIG. 2 schematically shows the optical scanning device 12.

The optical scanning device 12 is provided with a collimator lens 34 for converting the laser beam emitted from the LD 16 from a diverging light beam to a parallel light beam.

Further, the optical scanning device 12 is provided with a cylinder lens 36 for converging the laser beam emitted through the collimator lens 34 in the sub-scanning direction.

The rotary polygon mirror 18 is adapted to rotate at a high speed in the direction of arrow D.

Further, on the peripheral surface of the rotary polygon mirror 18,
A reflection surface 18A formed of a regular polygon (a regular hexagon in the present embodiment) for reflecting the laser beam is provided.

The laser beam passing through the cylinder lens 36 is incident on the reflecting surface 18A of the rotating polygon mirror 18 rotating at high speed in the direction of arrow D. Thereby, the incident angle of the laser beam incident on the reflection surface 18A changes continuously, and the laser beam is deflected.

In the traveling direction of the laser beam deflected by the rotary polygon mirror 18, an fθ lens 38 for making the scanning speed of the laser beam on the photosensitive member 14 uniform is used.
Is provided.

The fθ lens 38 is a first lens 38A
And a second lens 38B.

The laser beam transmitted through the fθ lens 38 is bent by the above-mentioned reflecting mirror 20 and is reflected toward the photoconductor 14.

Further, the optical scanning device 12 is provided with a photodetector 40 for detecting the timing of starting the image writing of the laser beam by the optical scanning device 12.

A mirror 41 is provided at a position where the image writing of the laser beam by the optical scanning device 12 is started.

The laser beam reflected by the mirror 41 is incident on the photodetector 40, and the image writing start timing is detected.

When the image writing start timing is detected, an SOS (Start Of Scan) signal indicating that the image writing start timing has been detected.
n) A signal is output from the photodetector 40.

Next, a case where an automatic light amount adjusting operation (hereinafter, referred to as APC) is added will be described.

FIG. 3 shows a block diagram of the droop improving device 42.

The droop improving device 42 is provided with a memory 44 for temporarily storing image data.

The memory 44 temporarily stores image data of an image to be printed in the case of a printer, and image data input by an image reading device in the case of a digital copying machine.

The memory 44 includes the memory 4
4 is connected to an image data determination unit 46 that determines the contents of the image data stored in the storage unit 4.

In the image data determination section 46, prior to the determination of the image data, the droop characteristic of the LD 16 used in advance is measured. After the droop characteristic is measured, the continuous lighting time at which a defect in image quality (image quality defect) occurs is determined. After the continuous lighting time is determined, an APC addition reference time t (ref) is set as a reference for determining whether to add APC.

The APC addition reference time t (ref) is
The length is set short for an LD with a bad droop characteristic, and set long for an LD with a good droop characteristic.

The image data determination section 46 includes an LD 16
Lighting signal detection circuit 4 for detecting a lighting signal, which is a signal for lighting the light, from the image data stored in the memory 44.
8 are provided.

The lighting signal detecting circuit 48 is connected to a lighting time measuring circuit 50 for measuring the lighting time of the lighting signal detected by the lighting signal detecting circuit 48. In the lighting time measuring circuit 50, the memory 44
The continuous lighting time t (c) per scanning line of the laser beam scanned based on the image data stored in the storage device is measured.

The lighting time measuring circuit 50 is connected to an APC addition determining section 52 for determining whether or not to add APC.

In the APC addition determining section 52, the AP
The length of the C addition determination reference time t (ref) is compared with the length of the continuous lighting time t (c).

In the APC addition determining section 52, if the result of the comparison is t (c) <t (ref), no APC is added and the result of the comparison is t (c) ≧ t (c). In the case of t (ref), APC is added.

When the APC addition determining section 52 determines that the APC is to be added, the APC addition timing is calculated so that the APC addition timing coincides.

The APC addition determining section 52 is connected to an M / C state determining section 54 for determining the state of the inside of the image recording apparatus 10 (hereinafter referred to as M / C).

The M / C state determination section 54 includes an LD 16
An LD vicinity temperature detection circuit 56 for detecting a temperature near
An LD output detection circuit 58 for detecting the output of the laser beam emitted from the LD 16 is provided.

The LD proximity temperature detection circuit 56 and the L
The D output detection circuit 58 is connected to the APC addition determination section 52, respectively.

In the APC addition determining section 52, the LD
When the temperature in the vicinity of the LD 16 detected by the nearby temperature detection circuit 56 is higher than a predetermined temperature,
The APC addition determination reference time t (ref) is set shorter than the APC addition determination reference time t (ref) set by the image data determination unit 46.

When the output of the laser beam detected by the LD output detection circuit 58 is lower than a predetermined output value, the APC addition determination section 52 sets the APC addition determination reference time t ( ref) is set shorter than the APC addition determination reference time t (ref) set by the image data determination unit 46.

As a result, it is determined that the environment is such that an image quality defect due to the droop phenomenon is likely to occur, and the number of times of adding the APC per one scan of the laser beam increases by shortening the APC addition determination time t (ref). Thus, image defects due to droop can be prevented.

That is, the temperature near the LD 16 and the LD
The APC addition determination time is changed from both the output of the laser beam emitted from the APC 16 and the output of the laser beam. In this case, the AP
The value after changing the C addition time t (ref) is t ′ (re
Assuming that f), t ′ (ref) = A × t (ref) × (output of laser beam emitted from LD 16 / temperature near LD 16). The APC addition determination time after the change is proportional to the output of the laser beam emitted from the LD 16,
It is inversely proportional to the temperature near the LD 16. Here, A is a constant that varies depending on the type of LD.

T ′ (ref) obtained as described above
Is the APC after changing the APC addition time t (ref).
It is set as the PC addition determination reference time t (ref) (t (ref) ← t ′ (ref)).

Further, the APC addition determining section 52
An APC timing calculator 60 for calculating the timing of adding a PC is connected.

The APC timing calculation section 60 has S
AP from when OS signal is detected until APC ends
APC end time calculation circuit 62 for calculating C end time Te
An APC time Ta calculating circuit 64 for calculating an APC time Ta which is a time for adding an APC; and a time obtained by subtracting the APC time Ta from the APC end time Te, and the APC time from when the SOS signal is detected. APC start time (Te-Ta) which is the time until the start of
APC start time (Te-Ta) calculation circuit 66 for calculating
And are provided.

The APC start time (Te-Ta) calculated by the APC start time (Te-Ta) calculation circuit 66
Based on a), a PCONT signal is generated as a reference for the timing of APC addition.

Further, the APC timing calculation section 60 outputs an APC timing based on the generated PCONT signal.
An APC addition control unit 68 for controlling the addition of the APC is connected.

Further, the APC addition control section 68 includes:
An LD drive circuit 70 that outputs a drive current for driving the LD 16 is connected. The LD 16 is connected to the LD drive circuit 70, and the LD 16 is driven according to the drive current output from the LD drive circuit 70.

The APC addition control unit 68 controls the PCO
APC is added based on the NT signal, and the LD driving circuit 60
, The light amount of the LD 16 can be kept substantially constant.

Further, the image data judgment section 46 is provided with a halftone detecting circuit 72 for detecting a place where a halftone occurs after the LD 16 is continuously turned on before the LD 16 is turned on continuously. Before the LD 16 is continuously turned on, the halftone detection circuit 72 detects a place where halftone occurs after the LD 16 is continuously turned on, and APC is added only to a place where an image quality defect due to a droop phenomenon is likely to appear. Done. In a controller with a slow processing speed or a controller that controls many ports at once, there is a concern that adding a large number of APCs will reduce the processing speed.
Is performed, it is possible to prevent such a decrease in processing speed.

FIG. 4 shows an APC addition sequence.

Here, VDATA is an LD on / off signal for recording an image and for APC. The PCONT signal is a signal indicating the timing of APC addition. Further, the H level signal indicates an off state, and the L level signal indicates an on state.

When the PCONT signal is an L level signal, the APC operates.

Here, the SOS signal is a signal based on image writing. In the APC addition, APC is added when an APC start time (Te-Ta), which is a time from the detection of the SOS signal to the start of the APC, has elapsed.

This PCONT signal is transmitted to the APC controller 6.
8 to control the LD drive circuit 70. The LD drive circuit 70 is driven in this manner, and an APC is added so that the output of the laser beam emitted from the LD 16 becomes substantially constant.

Particularly, in the image recording area, the LD 16
When the halftone image is recorded after the is continuously turned on, the above-described addition of the APC to the normal APC operation is performed, so that an image quality defect (image quality defect) such as a tailing line is generated.
Can be prevented from occurring.

Next, the operation of the present embodiment will be described.

FIG. 5 shows a flowchart of the APC adding operation according to the present embodiment.

Image data is input (step 10).
0), the process proceeds to step 102, the image data is temporarily stored in the memory 44, and the process proceeds to step 104.

In step 104, a lighting signal per scan is detected from the image data. When the detection is completed, the process proceeds to step 106.

In step 106, the lighting time per one scan based on the lighting signal is measured. When the measurement is completed, the process proceeds to step 108.

In step 108, it is determined whether or not there is a halftone image in the image recorded based on the image data. If the determination is affirmative, the process proceeds to step 110, and if the determination is negative, the process proceeds to step 132 described below.

If the determination is affirmative, the process proceeds to step 110.
In step 110, the temperature near the LD 16 is detected. When the detection of the temperature near the LD 16 is completed, the process proceeds to step 112.

In step 112, step 1
It is determined whether or not the temperature near the LD 16 detected at 10 is higher than a predetermined temperature. If the determination is affirmative, the process proceeds to step 114, and if the determination is negative, step 116 described below is performed.
Move to

If the determination at step 112 is affirmative, the routine proceeds to step 114, where the APC addition determination time t (ref) is made shorter than a preset time,
Move to step 116.

In step 116, it is determined whether the output of the LD 16 is lower than a predetermined output value. If the determination is affirmative, the process proceeds to step 118, and if the determination is negative, the process proceeds to step 120 described below.

If the determination at step 116 is affirmative, the routine proceeds to step 118, where it is determined whether or not the time is shorter than the APC addition determination time t (ref).
If the determination is affirmative, the process proceeds to step 120, and if the determination is negative, the process proceeds to step 132 described below.

If the determination in step 120 is affirmative, the process proceeds to step 122, where the APC end time Te is calculated, and the process proceeds to step 124.

At step 124, the APC addition time Ta is calculated, and the routine goes to step 126.

In step 126, the time (Te-Ta) obtained by subtracting the APC addition time Ta from the APC end time Te is calculated as the APC start time, and the routine proceeds to step 128.

At step 128, a PCONT signal is generated based on the APC start time (Te-Ta), and the routine goes to step 130.

In step 130, step 1
AP based on the PCONT signal generated at 28
C is added. When the APC is added, the process proceeds to step 132.

In step 132, the LD is calculated based on the drive current obtained by adding the APC to the normal APC operation.
16 is driven.

Here, as shown in FIG. 4, when the halftone image is recorded after the LD 16 is continuously turned on in the image recording area, the above-described APC is added to the normal APC operation. Since the output of the laser beam emitted from the LD 16 becomes substantially constant, it is possible to prevent image quality defects (image quality defects) such as tail lines from occurring.

Step 108 or Step 1
When the process proceeds from step 20 to step 132, the LD 16 is driven without adding the APC.

When the process proceeds from step 130 to step 132, APC is added and LD1 is added.
6 is driven.

When the driving of the LD 16 is completed in step 132, the process proceeds to step 134, and the image recording for one scan is completed.

The effects of the present embodiment will be described below.

FIG. 6 shows a temperature change of the LD 16.

The temperature of the LD 16 rises due to self-heating according to the continuous lighting time of the LD 16.

The rate at which the temperature rises becomes steeper as the duty becomes higher, and the saturation temperature becomes higher.

FIG. 7 shows a change in the output of the laser beam emitted from the LD 16.

The output of the laser beam emitted from the LD 16 decreases as the temperature rises.

The rate of this decrease becomes steeper as the duty becomes higher. That is, when the continuous lighting of the LD 16 continues, the output of the laser beam gradually decreases.

FIG. 8 shows a temperature change of the LD 16 when the continuous lighting time of the LD 16 is short.

A is set according to the length of the continuous lighting time of the LD 16.
The effect of adding a PC is different. When the continuous lighting time of the LD 16 is short, the temperature rise of the LD 16 is low. When the duty other than the continuous lighting is small, the temperature may be lower than immediately after the continuous lighting of the LD 16 is completed. When the duty is large, the temperature rise slope is gentler than when the LD 16 is continuously turned on, but the temperature rise of the LD 16 continues.

As shown in FIG.
When the duty is small, the output of the laser beam is recovered from the output, and when the duty is large, the output continues to decrease. If you add APC here,
When the duty is small, the output gradually increases in a direction larger than the set value. However, when the decrease in the output due to the continuous lighting of the LD 16 is large, the amount of change in the decrease in the output of the laser beam emitted from the LD 16 is small as compared with the decrease in the output before the APC is added.
The improvement effect by adding PC can be obtained. When the duty is large, the output continues to decrease even after APC is added.
C The amount of decrease in the output is smaller than before the addition,
The improvement effect by adding PC can be obtained.

As shown in FIG. 10, when the lighting time is long, the temperature rise of the LD 16 is large. If the duty other than the continuous lighting of the LD 16 is small, the LD 16
The temperature may drop immediately after the continuous lighting of. However, the temperature of the LD 16 remains higher than before the LD 16 is continuously turned on. When the duty of the portion other than the continuous lighting of the LD 16 is large, the slope of the temperature rise becomes gentler than in the case of the continuous lighting. However, it can be seen that the temperature rise continues.

[0116] As shown in FIG.
When the duty is small, the output of the set laser beam is recovered from the output of the laser beam, and when the duty is large, the output of the laser beam emitted from the LD 16 continues to decrease.

When the duty is small when APC is added, the output of the laser beam emitted from the LD 16 gradually increases in a direction larger than the set value. However, the amount by which the output of the laser beam fluctuates due to the rise is small, and almost reaches the target set value.

When the duty is large, the output of the laser beam continues to decrease even after the addition of the APC, but the decrease is small compared to before the addition of the APC, and the improvement effect by the addition of the APC is obtained.

According to the present embodiment, by adding the above-described APC to the normal APC operation, when the halftone image is recorded after the LD 16 is continuously turned on in the image recording area, Since the output of the laser beam emitted from the LD 16 becomes substantially constant, it is possible to prevent image quality defects (image quality defects) such as tail lines from occurring.

[0120]

As described above, according to the present invention, there is an excellent effect that an image quality defect due to a droop phenomenon of a semiconductor laser can be easily removed.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an image recording apparatus according to the present embodiment.

FIG. 2 is a schematic diagram of an optical scanning device according to the present embodiment.

FIG. 3 is a schematic diagram of a droop improvement device according to the present embodiment.

FIG. 4 is a diagram showing a light amount addition sequence for droop improvement according to the present embodiment.

FIG. 5 is a sequence diagram of APC addition according to the present embodiment.

FIG. 6 is a diagram showing a temperature change of an LD.

FIG. 7 is a diagram showing a change in output of a laser beam emitted from an LD.

FIG. 8 is a diagram showing a temperature change of an LD when a continuous lighting time is short.

FIG. 9 is a diagram showing a change in light output of an LD when the continuous lighting time is short.

FIG. 10 is a diagram showing a temperature change of an LD when a continuous lighting time is long.

FIG. 11 is a diagram showing a change in light output of an LD when a continuous lighting time is long.

[Explanation of symbols]

 Reference Signs List 10 image recording device 44 memory 46 image data determination unit 48 lighting signal detection circuit 50 lighting time measurement circuit 52 APC addition determination unit 54 M / C state determination unit 56 LD temperature detection circuit 58 LD output detection circuit 60 APC timing calculation unit 68 APC control unit 70 LD drive circuit 72 Halftone detection circuit

 ────────────────────────────────────────────────── ─── Continued on the front page F-term (reference) 2C362 AA03 AA54 AA55 AA56 AA59 AA63 CA14 5C051 AA02 CA07 DA01 DB02 DB30 DE30 EA02 FA01 5C072 AA03 BA20 HA02 HB04 XA05 5C074 AA02 BB03 DD03 EE06 EE11 HH07 GA04

Claims (6)

[Claims] 1. An image recording apparatus for forming an electrostatic latent image on an image carrier by turning on / off a semiconductor laser in an exposure unit according to image data. An image recording apparatus that performs an automatic light amount control operation in an image recording area separately from a control operation. 2. An image recording apparatus for forming an electrostatic latent image on an image carrier by turning on / off a semiconductor laser in exposure means in accordance with image data, the image recording apparatus comprising: A continuous lighting time measuring means for measuring the time of this image data which is lit almost continuously; a comparing means for comparing the measured continuous lighting time with a predetermined reference time; usually, when the continuous lighting time is longer than the reference time, An additional means for newly adding an automatic light amount control operation separately from the automatic light amount control operation of the above (1). 3. The image processing apparatus according to claim 1, further comprising an analyzing unit configured to analyze the image data prior to the image recording of the image data, wherein the additional unit is configured to perform the continuous lighting when it is determined that the continuous lighting is followed by the halftone image. 3. The image recording apparatus according to claim 2, wherein an automatic light amount control operation is added during the period. 4. The image recording apparatus according to claim 2, further comprising timing determining means for terminating the added automatic light amount control operation simultaneously with the end of the continuous lighting. 5. A semiconductor device comprising: a temperature detecting means in the vicinity of the semiconductor laser; and a means for changing a reference time compared by the comparing means based on a result of the detection. The image recording apparatus according to claim 2, wherein 6. The semiconductor laser according to claim 2, further comprising: means for detecting an output of the semiconductor laser; and means for changing a reference time for automatic light quantity control operation addition determination based on the detection result. 6. The image recording apparatus according to 5.