JPH11345998A - Luminous quantity controlling method, image forming method and image forming equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively control luminous quantity of two light emitting parts in a short time by using a single light detecting means, and reduce error. SOLUTION: One light emitting part LD1 is made to emit a light. The light is detected by a photodiode PD. The detected value is compared with a reference voltage Vref by a comparator 23. The difference is stored in one sample hold capacitor 27, and the luminous quantity of the light emitting part LD1 is controlled. In the same manner, the other light emitting part LD2 is made to emit a light. The light is detected by the photodiode PD. The detected value is compared with the reference voltage Vref by a comparator 24. The difference is stored in the other sample hold capacitor 28, and the luminous quantity of the light emitting part LD2 is controlled. The light emitting and sampling of both the light emitting parts LD1, LD2 are periodically performed with different phases, so that operations of different timing are enabled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a method for controlling a light emission amount of two light emitting units, an image forming method, and an image forming apparatus.

[0002]

2. Description of the Related Art Conventionally, an image forming apparatus such as a laser printer is provided with a light emitting means such as a semiconductor laser, and the light from the light emitting means is reflected by a rotating polygon mirror (polygon mirror) to form a light on a photosensitive drum. Image. Then, toner is attached to an exposed portion (or a non-exposed portion) on the photosensitive drum, and the toner is further applied to a recording medium (recording paper, etc.).
Is transferred to In order to improve the quality of an image to be formed, it is desired that the amount of light for exposing the photosensitive drum is sufficient. Therefore, light from the light emitting means is reflected by a mirror or the like and is incident on a light detecting means (photodiode). Based on the output of the light detecting means, light quantity control for controlling the amount of light emitted from the light emitting means is performed. .

As a light emitting means of such a conventional image recording apparatus, a semiconductor laser which emits a single beam is generally used.
As the definition becomes higher, the use of a multi-beam semiconductor laser having a plurality of light emitting units is being studied.

[0004]

SUMMARY OF THE INVENTION Conventional commercially available 2
The beam semiconductor laser has two laser emission units and one photodiode for monitoring the laser light. In this semiconductor laser,
When performing light amount control for setting the laser light amount of each laser light emitting unit to a predetermined light amount, it is necessary to separately input light from both light emitting units to the photodiode. In other words, when light from both light-emitting portions is incident on the photodiode at the same time, even if the total light amount does not match the predetermined light amount and there is an error, it is necessary to adjust the drive current of either of the two light-emitting portions. It is impossible to control the amount of light because it is not known.
Even if the light amount of each light emitting unit includes an error, if the total light amount of both light emitting units coincides with the predetermined light amount, the light emitting unit is regarded as normal, so that appropriate control cannot be performed. Therefore, when performing light amount control, it is necessary to individually apply a current to each laser light emitting unit. While a drive current is applied to one laser light emitting unit and light amount control is performed, the other laser light emitting unit is used. The light emitting unit needs to be turned off.

[0005] Further, light quantity control by sample hold,
That is, when a method of driving the light emitting units while holding the voltage corresponding to the light emitting unit drive current when the predetermined light amount is obtained in the sample and hold capacitor is performed for each light emitting unit, the light amount of one light emitting unit is During the control (while the voltage for driving one light emitting unit is sampled and held in the capacitor), the voltage for driving the other light emitting unit must be stored in another storage means. No. Further, when the storage means is configured on hardware, it is necessary to use a large-capacity holding capacitor, and the response of the light quantity control is poor and the control operation is slow.

Accordingly, an object of the present invention is to provide a light emission amount control method capable of controlling the light emission amounts of two light emitting units efficiently and in a short time with a small error by using a single light detecting means. An object of the present invention is to provide an image forming method including an amount control method and an image forming apparatus.

[0007]

A feature of the present invention is a light emission amount control method for simultaneously controlling the light emission amounts of two light emitting units by a single light detecting means, wherein light emitted from one of the light emitting units is controlled. Is periodically sampled using the light detection means,
The resulting data is stored in one of the sample-and-hold capacitors, and the light emission of the one light emitting unit is controlled based on the stored data, and the light from the other light emitting unit is detected using the light detection unit. Periodically sampling, storing the resulting data in the other sample and hold capacitor, controlling the light emission of the other light emitting unit based on the stored data, and controlling the light emitting and sampling period of the one light emitting unit. The phase of the light emission and sampling of the other light emitting unit is different from the phase of the light emission and sampling of the other light emitting unit, and the light emission and sampling of the two light emitting units are always performed at different timings.

When the light from the one light emitting section is detected by a single reference position detecting means, the light emission and sampling of the one light emitting section are performed, and the light from the other light emitting section is detected by the reference position detecting means. When light emission is detected, the timing of light emission and sampling of the two light emitting units may be made different by performing light emission and sampling of the other light emitting unit.

Further, when the light from the one light emitting section is detected by a single reference position detecting means, the light emission and sampling of the one light emitting section are performed, and from the time when the light from the one light emitting section is detected. The light emission and sampling of the two light emitting units may be made different by performing light emission and sampling of the other light emitting unit after a predetermined time has elapsed.

[0010] The two light emitting units may be semiconductor laser light emitting units, the light detecting means may be a photodiode, and the semiconductor laser light emitting unit and the photodiode may be formed in a single semiconductor laser unit. .

Light emission and sampling of the one light emitting unit are continuously performed, and thereafter light emission and sampling of the one light emitting unit are periodically performed, and light emission and sampling of the other light emitting unit are performed on the one light emitting unit. And the light emission and sampling of the two light emitting units may be performed periodically and at different phases.

Another feature of the present invention is that the light from the two light emitting units is reflected by a rotating polygon mirror to expose the outer peripheral portion of the photosensitive drum, and toner is attached to the outer peripheral portion of the photosensitive drum. In the image recording method of transferring to a recording medium,
When the light emission amount control method of periodically emitting light and sampling of the two light emitting units at different phases is performed when light from the light emitting unit is incident outside the image forming area of the photosensitive drum. is there.

When the light from the one light emitting section is incident on the image forming area of the photosensitive drum, the light emitting section and the sampling of the one light emitting section are continuously performed. When light is incident outside the image forming area of the photosensitive drum and light from the other light emitting section is incident on the image forming area of the photosensitive drum, light emission and sampling of the one light emitting section are performed. Is performed periodically, and the light emission and sampling of the other light emitting unit are performed in a phase opposite to that of the one light emitting unit, and light from both light emitting units is incident outside the image forming area of the photosensitive drum. In this case, light emission and sampling of both light emitting units may be performed periodically and at different phases.

Still another feature of the present invention is that two light-emitting portions, a rotary polygon mirror that receives and reflects light from the light-emitting portion, and receives light reflected by the rotary polygon mirror to receive light at the light receiving point. In an image forming apparatus having a photosensitive drum for forming a corresponding image, a single light detecting unit for detecting light from each of the light emitting units, and a pair of samples provided corresponding to the both light emitting units A hold capacitor, using the light detection unit to sample light from the one light emitting unit, storing the resulting data in one of the sample and hold capacitors, and storing the one light emission based on the stored data. Control the amount of light emitted from the light emitting unit, sample the light from the other light emitting unit using the light detection unit, and store the resulting data in the other sample and hold capacitor. A light emission control unit for controlling the light emission amount of the other light emitting unit based on the stored data; and causing the light emission and sampling of the two light emitting units to be performed periodically and at different phases, so that the light emission of the two light emitting units is performed. And the light emission control means and the control means for controlling the light emission unit so that sampling is always performed at different timings.

[0015] When the reference position detecting means detects the light from the one light emitting unit, the control unit performs light emission and sampling of the one light emitting unit. The light-emitting control unit and the light-emitting unit may be configured so that when the reference position detecting unit detects light from the other light-emitting unit, the other light-emitting unit emits light and performs sampling.

Further, there is provided a single reference position detecting means, and when the control means detects the light from the one light emitting section, the light emitting section and the sampling of the one light emitting section are performed. The light emission control unit and the light emission unit may be configured so that light emission and sampling of the other light emission unit are performed after a lapse of a predetermined time from the point in time when light from the one light emission unit is detected. .

[0017] The two light-emitting portions may be semiconductor laser light-emitting portions, the light detecting means may be a photodiode, and the semiconductor laser light-emitting portion and the photodiode may be formed in a single semiconductor laser unit. .

The control means continuously emits and samples the light from the one light emitting section, then periodically emits and samples the light from the one light emitting section, and emits and samples the light from the other light emitting section. A configuration in which the sampling is performed in an opposite phase to the one light emitting unit, and thereafter, the light emission control unit and the light emitting unit are controlled such that light emission and sampling of the two light emitting units are performed periodically and at different phases. It may be.

When the light from the light emitting section is incident on the photosensitive drum outside the image forming area,
The light emission control unit and the light emission unit may be controlled so that light emission and sampling of the two light emission units are performed periodically and at different phases.

When the light from the one light emitting unit is incident on the image forming area of the photosensitive drum, the control unit continuously emits light and samples the one light emitting unit. When light from one light emitting unit is incident outside the image forming area of the photosensitive drum, and light from the other light emitting unit is incident on the image forming area of the photosensitive drum, Light emission and sampling of the light emitting unit are periodically performed, and light emission and sampling of the other light emitting unit are performed in a phase opposite to that of the one light emitting unit. The light emission control unit and the light emission unit are controlled such that light emission and sampling of both light emission units are performed periodically and at different phases when the light is incident outside the image forming area. It may be.

According to the present invention, the light from the two light emitting units is detected by a single light detecting means. Although this detection result is output as one pulse wave, the light emission of both light emitting units is performed periodically and at mutually different phases, so that they are always performed at different timings. Therefore, by performing sampling in correspondence with the light emission timing, one pulse wave can be divided into light emission by one light emission part and light emission by the other light emission part by the timing. Data can be stored on separate sample and hold capacitors.

The setting is simple if the timing of detection from both light emitting units by the reference position detecting means is used as a trigger for the timing of light emission and sampling.

[0023]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic diagram showing a basic configuration of an image forming apparatus according to a first embodiment of the present invention, FIG. 2 is a block diagram showing a control relationship thereof, and FIG. 3 is a circuit diagram thereof.

As shown in FIG. 1, the image forming apparatus of this embodiment includes a semiconductor laser unit 1 which is a light emitting unit and a light detecting unit, a collimator lens 2, an aperture 3,
Cylinder lens 4, polygon mirror 5, which is a rotating polygon mirror, tilt correction lens 6, fθ lens 7, folding mirror 8, photosensitive drum 9, folding mirror 10
, A lens 11 and a reference position detection sensor 12.

The semiconductor laser unit 1 has two light emitting portions LD1 and LD2 shown in FIGS. 2 and 3 and can emit two laser beams (laser light).
A photodiode PD serving as a light detection unit is incorporated and integrated, and is driven by a light amount control unit 32 and a control unit 31 shown in FIGS. Light emitting units LD1, LD2
A power supply (not shown) is connected to the photodiode PD. The collimator lens 2 changes the laser light emitted from the semiconductor laser unit 1 into substantially parallel light. The aperture 3 determines the amount of the captured laser light transmitted through the collimator lens 2. The cylinder lens 4 forms an image of the laser beam transmitted through the aperture 3 on the outer peripheral surface of the polygon mirror 5. The outer peripheral surface of the polygon mirror 5 is a mirror surface, and is rotated by a motor (not shown). The tilt correction lens 6 corrects the tilt of the light reflected by the polygon mirror 5. lens 7 performs a correction for enlarging the laser beam transmitted through the tilt correction lens 6 and transferring it to the entire width of the image forming area. Folded mirror 8
Guides the laser light enlarged and corrected by the fθ lens 7 to the outer peripheral surface of the photosensitive drum 9. The photoreceptor drum 9 has a photoreceptor provided on an outer peripheral surface, and a portion where laser light is incident via the return mirror 8 is exposed. Then, although not shown, the toner is attracted to only the exposed portions (or only the unexposed portions) by static electricity, and the toner is transferred to a recording medium and subjected to a fixing process to perform image recording. That is, an image corresponding to the portion of the outer peripheral surface of the photosensitive drum 9 where the laser light is incident is formed on the recording medium.

The folding mirror 10 is arranged at a predetermined position (side of the folding mirror 8) outside the image forming area of the photosensitive drum 9, and reflects reflected light directed outside the image forming area by the polygon mirror 5. The light is reflected toward a reference position detection sensor (reference position detection means) 12. Lens 1
1 converges the light reflected by the folding mirror 10 on the light detection portion of the reference position detection sensor 12. The reference position detection sensor 12 detects that the laser light is applied to the reference position in the main scanning direction, and outputs a signal serving as a reference for adjusting the timing of laser light irradiation for image formation (FIG. 2).

According to this image forming apparatus, a collimator lens 2, an aperture 3,
The laser light emitted through the cylinder lens 4 is reflected by the rotating polygon mirror 5 and is incident on the photosensitive drum on the outer peripheral surface of the photosensitive drum 9 via the tilt correction lens 6, the fθ lens 7, and the return mirror 8. Let it. Then, toner is attached to an exposed portion (laser beam incident portion) of the photosensitive drum 9, and the toner is transferred to a recording medium such as a recording medium, and the toner is fixed on the recording medium. Image formation is performed in this manner. By irradiating the semiconductor laser unit 1 with laser light at an appropriate timing in synchronization with the rotation of the polygon mirror 5, a desired image can be formed.

As shown in FIG. 2, the semiconductor laser unit 1 of the present embodiment has two light emitting units LD1, LD2 and a photodiode PD, and is controlled by a light emission control unit 31. Further, the light emission control means 31 includes a control means 32
Is controlled by Also, the reference position detection sensor 12
The control means 32 is connected to be able to supply a reference position detection result.

FIG. 3 shows a specific circuit configuration of the semiconductor laser unit 1 and the emission control means 32 of the present embodiment.

The semiconductor laser unit 1 has laser light emitting units LD1 and LD2 and a photodiode PD. Then, the laser light emitted from the light emitting units LD1 and LD2 is reflected by a reflection mirror (not shown) or the like and is incident on the photodiode PD.

The light emission control means 32 comprises an independent light emission control unit 33 of the light emission unit LD1 and a light emission control unit 34 of the light emission unit LD2. The two light emission control units 33 and 34 are respectively detection result processing units 33a and 34a. And drive units 33b, 34
b.

First, the configuration of the detection result processing sections 33a and 34a will be described. The output unit of the photodiode PD branches into two systems, and the detection result processing units 33a and 33
4a. For details, see Photodiode P
The output of D is connected to adjustment variable resistors VR1 and VR2 via switches 13 and 14, and
From R1 and VR2, comparators (error amplifiers) 23 and 24
Are connected to one terminal. Although not described in detail, a reference voltage Vref is input to the other terminals of the comparators 23 and 24. From the comparators 23 and 24, the variable resistor VR
1 and VR2, and a voltage corresponding to the difference between the reference voltage Vref and the reference voltage Vref is output to the sample and hold capacitors 27 and 28 via the switches 25 and 26. The switches 13 and 14 are provided with signal input terminals 21 and 22 for inputting a switching signal, and the switches 25 and 26 are provided with signal input terminals 29 and 30 for inputting a sampling start signal. The switching signal and the sampling start signal are supplied from the control unit 31 shown in FIG.

Next, the driving units 33b and 34b will be described. The aforementioned sample and hold capacitors 27 and 28
Are connected to variable constant current sources 19 and 20, and the variable constant current sources 19 and 20 are connected to the emitter terminals of the driving transistors 15 and 16, respectively. This drive transistor 1
A data signal is input to base terminals 17 and 18 of the light-emitting portions LD to be driven.
1 and LD2 are connected to each other. The data signal is supplied from the control unit 31 shown in FIG.

Next, the operation of the light emission control means 32 will be described. When a switching signal is input from the control means 31 (see FIG. 2) to the signal input terminals 21 and 22 of the detection result processing units 33a and 34a, the switches 13 and 14 are turned on, and the output of the photodiode PD is changed to the variable resistance VR1. VR2. In the variable resistors VR1 and VR2, the output (detection current) of the photodiode PD is converted into a voltage.
Then, the comparators 23 and 24 compare the voltages from the photodiode PD and the variable resistors VR1 and VR2 with the reference voltage Vref. When a sampling start signal is input to the signal input terminals 29 and 30 from the control means 31 (see FIG. 2), the switches 25 and 26 are turned on, and the voltages from the photodiode PD and the variable resistors VR1 and VR2 and the reference voltage Vref. Are stored (held) in the sample and hold capacitors 27 and 28.

The voltages stored (held) in the sample and hold capacitors 27 and 28 are applied to the drive units 33b and 34b.
Are supplied to the variable constant current sources 19 and 20, respectively, and the variable constant current sources 19 and 20 supply the current adjusted to the magnitude corresponding to this voltage to the emitter terminals of the driving transistors 15 and 16. At this time, when a data signal is input from control means 31 (see FIG. 2) to base terminals 17 and 18 of drive transistors 15 and 16, this drive transistor 1
5 and 16 are turned on, and the current adjusted by the variable constant current sources 19 and 20 is supplied to the light emitting units LD1 and LD2.
Then, the light emitting units LD1 and LD2 are driven, and the laser light is emitted. Since the laser light emitted from the light emitting units LD1 and LD2 is detected by the photodiode PD, the detection result by the photodiode PD is fed back to the drive current of the light emitting units LD1 and LD2 by the operation described above. .

Next, a method of actually controlling the light emission amounts of the light emitting units LD1 and LD2 in the image forming apparatus of the present embodiment will be described more specifically with reference to time charts shown in FIGS. All of these time charts are shown in positive logic.

At time t0, the drive motor (not shown) is turned on, and the rotation of the polygon mirror 5 is started. Then, at time t1, a data signal is supplied from the control unit 31 to the base terminal 17 of the drive transistor 15 of the light emission control unit 33 for the light emitting unit LD1, the drive transistor 15 is turned on, and a drive current is supplied to the light emitting unit LD1. The light is supplied and the light emitting unit LD1 emits light. At the same timing (time t1), a switching signal is supplied from the control unit 31 to the signal input terminal 21 of the switch 13 of the light emission control unit 33. Thereby, the light emitted from the light emitting unit LD1 as described above is
The detection current detected by the photodiode PD is supplied to the variable resistor VR <b> 1, converted into a voltage value, and supplied to the comparator 23. In the comparator 23, this voltage value is compared with the reference voltage Vref, and the difference between the two voltages is output. Further, at the same timing (time t1), the control unit 3 is connected to the signal input terminal 29 of the switch 25 of the light emission control unit 33.
1 supplies a sampling start signal to the switch 25.
Turns on. Thereby, the voltage output from the comparator 23 is stored (held) in the sample-and-hold capacitor 27 and is supplied to the variable constant current source 19. The variable constant current source 19 changes the current value in accordance with the voltage, and since the drive transistor 17 is turned on as described above, the changed current is supplied to the light emitting unit LD1. Therefore, the driving current of the light emitting unit LD1 is changed in real time according to the light detection result by the photodiode PD, and the light emission amount is corrected.

Thereafter, at time t2, the reference position detection sensor 12 starts detecting the laser beam from the light emitting section LD1. That is, it is detected whether or not the laser beam from the light emitting unit LD1 is located at the reference position (the folding mirror 10) outside the image forming area. In the example shown in FIG.
In, the laser light from the light emitting section LD1 is not detected by the reference position detection sensor 12. After that, the laser beam is periodically detected.

Then, at time t3, the reference position detection sensor 12 first detects the laser beam from the light emitting section LD1. That is, it is detected that the laser beam from the light emitting unit LD1 has reached outside the image forming area. Therefore, the supply of the sampling start signal from the control means 31 to the signal input terminal 29 of the switch 25 is stopped, and the sample and hold capacitor 27 is kept in the hold state. At the same time, the supply of the data signal to the base terminal 17 of the drive capacitor 15 is stopped, and the light emission of the light emitting unit LD1 is stopped. At the same time, the supply of the switching signal to the signal input terminal 21 of the switch 13 is stopped, and the output of the photodiode PD is output to the light emitting unit LD1.
Is not supplied to the light emission control unit 33. After time t3,
Reference position detection sensor 12 for laser light from light emitting section LD1
, The data signal, the switching signal, and the sampling start signal are supplied from the control unit 31 in synchronization with the periodic detection, and the light emission of the light emitting unit LD1 and the light emission of the output of the photodiode PD are performed. The supply to the control unit 33 and the sampling by the sample and hold capacitor 27 are periodically performed. However, these are very short,
At other times, no light is emitted, the output of the photodiode PD is not supplied to the light emission control unit 33, and the sample-and-hold capacitor 27 is held.

On the other hand, at time t3, a data signal is supplied from the control means 31 to the base terminal 18 of the drive transistor 16 of the light emission control section 34 for the light emission section LD2,
The drive transistor 16 turns on, and the light emitting unit LD2 emits light. Further, at time t3, the switch 14 of the light emission control unit 34
The switching signal is supplied from the control means 31 to the signal input terminal 22 of the. Thereby, the output (detection current) of the photodiode PD is supplied to the variable resistor VR2, converted into a voltage value, and supplied to the comparator 24. In the comparator 24, this voltage value is compared with the reference voltage Vref, and the difference between the two voltages is output. Further, at time t3, the light emission control unit 3
4 is connected to the signal input terminal 30 of the switch 26 by the control means 31.
Supplies a sampling start signal, and the switch 26 is turned on. As a result, the voltage output from the comparator 24 is stored (held) in the sample and hold capacitor 28 and is supplied to the variable constant current source 20. The variable constant current source 20 changes the current value according to the voltage and supplies the current value to the light emitting unit LD2. Accordingly, the light emission amount of the light emitting unit LD2 is corrected in real time according to the light detection result by the photodiode PD.

However, during a short period during which the laser beam from the light emitting section LD1 is detected by the reference position detection sensor 12, a data signal is supplied to the base terminal 18, a switching signal is supplied to the signal input terminal 22, and sampling is started. The supply of the signal to the signal input terminal 30 is stopped, the light emission of the light emitting unit LD2, the supply of the output of the photodiode PD to the light emission control unit 34, and the sampling by the sample and hold capacitor 28 are not performed. The output of the diode PD is supplied to the light emission control unit 33 and sampling by the sample and hold capacitor 27 is performed. That is, after time t3, the sample and hold capacitor 2
8, while controlling the light emission amount of the light emitting unit LD2 using the sample and hold capacitor 27 and periodically holding the light emitting unit LD1 in the hold state for a short time, and controlling the light emission amount of the light emitting unit LD2. Hold state. It should be noted that each signal is not simultaneously supplied to both light emission control units from the control signal.

Thereafter, at time t4, the reference position detection sensor 12 starts detecting the laser beam from the light emitting section LD2. That is, it is detected whether or not the laser beam from the light emitting unit LD2 is located at the reference position (the folding mirror 10) outside the image forming area. In the example shown in FIG.
Previously, the laser light from the light emitting unit LD2 was not detected by the reference position detection sensor 12. Thereafter, the laser beam is periodically detected. However, the detection of the laser beam from the light-emitting unit LD2 and the detection of the laser beam from the light-emitting unit LD1 are performed by the control unit 31 so that the timing always deviates (so that the phases are different). Set the detection timing of

At time t5, the reference position detection sensor 12 detects the laser beam from the light emitting unit LD2, and detects that the laser beam from the light emitting unit LD2 has reached outside the image forming area. Therefore, the supply of the sampling start signal from the control means 31 to the signal input terminal 30 of the switch 26 is stopped, and the sample and hold capacitor 28 is kept in the hold state. At the same time, the supply of the data signal to the base terminal 18 of the drive capacitor 16 is stopped, and the light emitting unit LD
The light emission of 2 is stopped. At the same time, the supply of the switching signal to the signal input terminal 22 of the switch 14 is stopped, and the output of the photodiode PD is not supplied to the light emission control unit 33 of the light emitting unit LD2. After time t5, the periodic detection of the laser beam from the light emitting unit LD2 by the reference position detection sensor 12 continues, and in synchronization with the periodic detection, the data signal, the switching signal, and the sampling start signal from the control unit 31. To periodically emit light from the light emitting unit LD2, supply the output of the photodiode PD to the light emission control unit 34, and perform sampling by the sample and hold capacitor 28. However, these are very short periods, and the other times are non-light emitting, non-supply of the output of the photodiode PD to the light emitting control unit 34, and the sample-and-hold capacitor 28 is kept in the holding state.

That is, after time t5, the light emission of the light emitting section LD1 for a short time, the supply of the output of the photodiode PD to the light emission control section 33, and the sampling by the sample-and-hold capacitor 27 are periodically performed, and the phase different from this. The light emission of the light emitting unit LD2 and the photodiode P
The supply of the output of D to the light emission control unit 34 and the sampling by the sample and hold capacitor 28 are periodically performed.
At other times, the sample and hold capacitors 27,
28 are kept in a hold state. The light emitting units LD1, L
D2 emission, supply of output of photodiode PD to emission control units 33 and 34, sample-and-hold capacitor 2
Sampling by 7 and 28 is not performed simultaneously.

Although the output itself of the photodiode PD is one data, the output is output to one of the light emission control units 33 and 34 in synchronization with the light emission of the two light emitting units LD1 and LD2 at periodic and mutually different phases. And sample data for controlling the light emission amount of the light emitting unit LD1 held by the sample and hold capacitor 27, and for controlling the light emission amount of the light emitting unit LD2 to be held by the sample and hold capacitor 28. And sample data. Both light emitting parts LD1, LD2
The light emission and sampling by the sampling and holding capacitors 2 are always performed at different timings.
The data to be held at 7, 28 is not confused or disturbed.

That is, according to this method, a single photodiode PD is used, and in a series of operations of scanning two beams by a polygon mirror, two light emitting units L are used.
Both D1 and LD2 can control the light emission amount. Each light emitting unit L
The control of the light emission amounts of D1 and LD2 can be performed more efficiently as compared with a case where the control is performed separately by shifting the time by one. Moreover, since the light emitting units LD1 and LD2 do not emit light at the same time during the light emission amount control, the light detection result by the photodiode PD does not change significantly.

After time t5, both the laser beam from the light emitting section LD1 and the laser beam from the light emitting section LD2 scan outside the image forming area. However, when the two laser beams again irradiate the image forming area, the data signals are supplied to the light emission control units 33 and 34 not periodically as described above but according to the image to be formed. In this case, sampling may be performed occasionally at an appropriate timing,
It may be kept in the hold state.

In the above description, the pulse width of each signal is assumed to be the same, but in this case, if there is a slight timing error, both light emitting units LD1 and LD
2 emits light at the same time, the photodiode PD detects the total light amount of the laser light of both light-emitting portions, and a voltage based on the detected light amount is sampled.

Therefore, as shown in FIG. 5, the pulse width of each signal is changed little by little. That is, if the pulse width (time) of the sampling start signal is a1, the pulse width (time) of the data signal is b1, and the pulse width (time) of the switching signal 21 is c1, the relationship a1 <b1 <c1 is established. I have. Then, the control means 31 is set so that signals are output in order from the one with the largest pulse width.

Therefore, at time t10 shown in FIG.
When the reference position detection sensor 12 detects the laser beam from the light emitting unit LD1, first, the output of the photodiode PD is supplied to the light emission control unit 33 by a switching signal. then,
The light emitting unit LD1 emits light according to the data signal. then,
Sampling using the sample and hold capacitor 27 is performed by the sampling start signal. Then, at time t11, the reference position detection sensor 12 switches to the light emitting unit LD.
Upon detection of the laser light from 2, the supply to the light emission control unit 33 is stopped in the order of the sampling signal, the data signal, and the switching signal. Then, at time t11, the output of the photodiode PD is supplied to the light emission control unit 34 by the switching signal, and the light emitting unit LD2 emits light by the data signal. Then, sampling using the sample and hold capacitor 28 is performed according to the sampling start signal.

As described above, by providing a time lag by changing the pulse width of each signal, the light emitting section LD1 always emits light during sampling using the sample and hold capacitor 27 (while the sampling signal is being supplied). And the light emitting section LD2 never emits light. Conversely, during sampling using the sample and hold capacitor 28 (while the sampling signal is being supplied), the light emitting unit LD2 always emits light, and the light emitting unit LD1 never emits light. In the former case, the output of the photodiode PD is always supplied to the light emission control unit 33,
In the latter case, the output of the photodiode PD is always supplied to the light emission control unit 34. Also, both sampling operations are not performed simultaneously. Furthermore, it is almost impossible for both light emitting portions LD1 and Ld2 to emit light at the same time. Thereby, appropriate sampling can be performed.

The method of supplying each signal with the output of the reference position detection sensor 12 as a trigger is not limited to the examples shown in FIGS.

FIG. 6 is a timing chart of a light emission amount control method according to the second embodiment of the present invention.
The configuration of the image forming apparatus is the same as that of the first embodiment shown in FIGS.

In this embodiment, FIG.
Is the same as the first embodiment shown in FIG. After that, the reference position detection sensor 12 detects only the laser beam from the light emitting unit LD1, but does not detect the laser beam from the light emitting unit LD2. However, the reference position detection sensor 12 is a light emitting unit LD.
A sampling operation for controlling the light emission amount of the light emitting unit LD2 is performed in the same manner as in the first embodiment, using a point in time when a predetermined time has elapsed from the timing of detecting the laser light from No. 1 as a trigger. Accordingly, at times t4 'and t5' shown in FIG.
Means a point in time when a predetermined time set in advance has elapsed from time t3. The broken line in the reference position detection time chart of FIG. 6 is a point in time when a predetermined time has elapsed from the timing when the reference position detection sensor 12 detects the laser beam from the light emitting unit LD1. Since the positional relationship between the light emitting units LD1 and LD2 is known, the time difference between the light beam scanning from the light emitting unit LD1 and the light beam scanning from the light emitting unit LD2 can be obtained in advance. Therefore, by setting an appropriate time, the reference position detection sensor 1
2 does not detect the laser beam from the light-emitting unit LD2, and the two light-emitting units LD1 and LD1 have the same accuracy as in the first embodiment.
The light emission amount accuracy of the LD 2 is possible.

[0056]

According to the present invention, both light emitting units emit light in a series of two beam scanning operations using a light emitting unit having two light emitting units and a single light detecting unit. Thus, it is possible to efficiently control the light emission amount of each light emitting unit one by one with a time lag, and to perform the light emission control more efficiently and in a shorter time.

Moreover, since the light emitting sections do not emit light simultaneously during the light emission amount control, the light detection result by the light detection means does not greatly change and no error occurs in the light emission amount control.

[Brief description of the drawings]

FIG. 1 is a perspective view of a main part of an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a block diagram of the first embodiment.

FIG. 3 is a circuit diagram illustrating a light emission control unit according to the first embodiment.

FIG. 4 is a timing chart illustrating a light emission amount control method according to the first embodiment.

FIG. 5 is an enlarged explanatory diagram for explaining in more detail the light emission amount control method shown in the timing chart of FIG. 4;

FIG. 6 is a timing chart illustrating a light emission amount control method according to a second embodiment.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 semiconductor laser unit 2 collimator lens 3 aperture 4 cylinder lens 5 polygon mirror (rotating polygon mirror) 6 tilt correction lens 7 fθ lens 8 folding mirror 9 photosensitive drum 10 folding mirror 11 lens 12 reference position detection sensor (reference position detecting means) 13, 14 Switch 15, 16 Driving transistor 17, 18 Base terminal 19, 20 Variable type constant current source 21, 22 Signal input terminal 23, 24 Comparator (error amplifier) 25, 26 Switch 27, 28 Sample hold capacitor 29, 30 Signal input terminal 31 Control means 32 Light emission control means 33, 34 Light emission control section 33a, 34a Detection result processing section 33b, 34b Drive section LD1, LD2 Semiconductor laser light emission section PD Photodiode (light detection means) VR1, VR2 Variable resistance ref reference voltage

Claims (14)

[Claims] 1. A light emission amount control method for simultaneously controlling the light emission amounts of two light emitting units by a single light detecting unit, wherein light from one of the light emitting units is periodically controlled by using the light detecting unit. And stores the resulting data in one of the sample and hold capacitors, controls the light emission of the one light emitting unit based on the stored data, and detects the light from the other light emitting unit in the light detection. Means for periodically sampling, storing the resulting data in the other sample and hold capacitor, controlling the light emission of the other light emitting unit based on the stored data, and controlling the light emission of the one light emitting unit. And the sampling period,
A light emission amount control method, characterized in that the phase of the light emission and sampling of the other light emitting unit is different from the phase of the light emission and sampling of the other light emitting unit, and the light emission and sampling of both light emitting units are always performed at different timings. 2. When light from said one light emitting unit is detected by a single reference position detecting means, light emission and sampling of said one light emitting unit are performed. By detecting the light of the other light emission and sampling of the other light emitting unit,
The light emission amount control method according to claim 1, wherein timings of light emission and sampling of the two light emitting units are different. 3. When the light from the one light emitting unit is detected by a single reference position detecting means, light emission and sampling of the one light emitting unit are performed, and from the time when the light from the one light emitting unit is detected. 2. The light emission amount control method according to claim 1, wherein the light emission and sampling of the other light emitting units are made different by performing light emission and sampling of the other light emitting unit after a predetermined time has elapsed. 4. The semiconductor laser light emitting section, wherein the two light emitting sections are semiconductor laser light emitting sections, the light detecting means is a photodiode, and the semiconductor laser light emitting section and the photodiode are formed in a single semiconductor laser unit. Claim 1
3. The light emission amount control method according to claim 3. 5. The light emission and sampling of the one light emitting unit are continuously performed, and thereafter, the light emission and sampling of the one light emitting unit are periodically performed, and the light emission and sampling of the other light emitting unit are performed by the one light emitting unit. The method according to any one of claims 1 to 4, wherein light emission and sampling of the two light emitting units are periodically performed at different phases from each other. 6. An image recording method in which light from both light emitting units is reflected by a rotary polygon mirror to expose an outer peripheral portion of a photosensitive drum, and toner is attached to the outer peripheral portion of the photosensitive drum and transferred to a recording medium. The method according to any one of claims 1 to 5, wherein when the light from the light emitting unit is incident outside the image forming area of the photoconductor drum, light emission and sampling of the two light emitting units are performed periodically and at mutually different phases. An image recording method, wherein the light emission amount control method according to claim 1 is performed. 7. An image recording method in which light from the two light emitting units is reflected by a rotary polygon mirror to expose an outer peripheral portion of a photosensitive drum, and toner is attached to the outer peripheral portion of the photosensitive drum and transferred to a recording medium. In the above, when light from the one light emitting unit is incident on the image forming area of the photoconductor drum, light emission and sampling of the one light emitting unit are continuously performed, and light from the one light emitting unit is provided. Is incident outside the image forming area of the photosensitive drum, and when light from the other light emitting unit is incident on the image forming area of the photosensitive drum,
Light emission and sampling of the one light emitting unit are periodically performed, and light emission and sampling of the other light emitting unit are performed in a phase opposite to that of the one light emitting unit. 6. An image recording method according to claim 5, wherein when the light is incident outside the image forming area of the drum, light emission and sampling of both light emitting units are performed periodically and at mutually different phases. . 8. A light emitting unit, a rotary polygon mirror that receives and reflects light from the light emitting unit, and a light that receives light reflected by the rotary polygon mirror and forms an image corresponding to the light receiving point. An image forming apparatus having a body drum, comprising: a single light detection unit that detects light from each of the light emitting units; and a pair of sample and hold capacitors provided corresponding to the two light emitting units, The light from the one light emitting unit is sampled using the light detection unit, and the resulting data is stored in one of the sample and hold capacitors, and the light emission amount of the one light emitting unit is determined based on the stored data. While controlling, the light from the other light emitting unit is sampled using the light detecting means, and the resulting data is stored in the other sample and hold capacitor, and based on the stored data, Light emission control means for controlling the light emission amount of the other light emitting unit; and by causing the light emission and sampling of the two light emitting units to be performed periodically and at different phases, the light emission and sampling of the two light emitting units are always at different timings. An image forming apparatus comprising: the light emission control unit and a control unit that controls the light emission unit so as to be performed. 9. A single reference position detecting means, wherein the control means performs light emission and sampling of the one light emitting part when the reference position detecting means detects light from the one light emitting part. 9. The light emitting control unit and the light emitting unit according to claim 8, wherein when the reference position detecting unit detects light from the other light emitting unit, the light emitting control unit and the light emitting unit are controlled such that light emission and sampling of the other light emitting unit are performed. Image forming device. 10. A single reference position detecting means, wherein said control means emits light and samples said one light emitting part when said reference position detecting means detects light from said one light emitting part. 9. The light-emitting control unit and the light-emitting unit according to claim 8, wherein the light-emitting control unit and the light-emitting unit are controlled such that light-emission and sampling of the other light-emitting unit are performed after a lapse of a predetermined time from a point in time when light from the one light-emitting unit is detected. Image forming device. 11. The semiconductor laser light emitting unit, wherein the two light emitting units are semiconductor laser light emitting units, the light detecting means is a photodiode, and the semiconductor laser light emitting unit and the photodiode are formed in a single semiconductor laser unit. Claim 8
The image forming apparatus according to any one of claims 10 to 10. 12. The control means according to claim 1, wherein light emission and sampling of said one light emitting unit are continuously performed.
The light emission and sampling of the one light emitting unit are periodically performed, and the light emission and sampling of the other light emitting unit are performed in a phase opposite to that of the one light emitting unit. Thereafter, the light emission and sampling of the two light emitting units are performed. 12. The light emission control means and the light emission section are controlled so that the light emission control is performed periodically and at mutually different phases.
The image forming apparatus according to claim 1. 13. When the light from the light emitting unit is incident outside the image forming area of the photoconductor drum, the control unit periodically emits light and samples the light emitting units at different phases from each other. The image forming apparatus according to claim 8, wherein the light emission control unit and the light emitting unit are controlled so as to be performed. 14. The control unit according to claim 1, wherein when the light from the one light emitting unit is incident on an image forming area of the photosensitive drum, the light emitting unit and the sampling of the one light emitting unit are continuously performed. When light from the one light emitting unit is incident outside the image forming area of the photosensitive drum, and light from the other light emitting unit is incident on the image forming area of the photosensitive drum, Light emission and sampling of one light emitting unit are periodically performed, and light emission and sampling of the other light emitting unit are performed in a phase opposite to that of the one light emitting unit. A request to control the light emission control unit and the light emission unit so that light emission and sampling of both light emission units are performed periodically and at mutually different phases when the light is incident outside the image forming area of the body drum. An image forming apparatus according to claim 13.