JP2012113233A - Light beam scanner, image forming device, and light beam scanning method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an unnecessary light beam from being projected onto a photosensitive member in a light beam scanning device and to prevent deterioration of a light source and a photosensitive member. At the time of start-up until the beam scanning operation state is stabilized, it is provided at a predetermined position in the scanning path, and the period during which the LD is forcibly lit at the detection timing of the synchronous detection sensor for detecting the scanning light beam It is determined based on (rise), and forcible lighting is performed during that period (S102, 103). After the operation state of the light beam scanning is stabilized, the operation is switched to the operation for determining the LD forcible lighting period based on the synchronization detection signal, and the forcible lighting is performed (S105, 106).
[Selection] Figure 5

Description

  The present invention relates to a light beam scanning method for periodically scanning a light beam emitted from a light source. More specifically, the present invention relates to a synchronization signal necessary for controlling exposure of a predetermined position of a photoconductor by periodic scanning of the light beam. The present invention relates to a light beam scanning device, a light beam scanning method, and an image forming apparatus having the light beam scanning device that eliminate unnecessary light source lighting when the light beam detector is provided.

In an image forming apparatus called an electrophotographic printer, a so-called digital copying machine, or a multifunction machine, a light source such as a laser (LD: Laser Diode) capable of lighting control is used today, and the light beam emitted from the light source periodically For example, a method of scanning an exposure surface (image surface) of a photoconductor to generate an electrostatic latent image on the exposure surface of the photoconductor is widely used.
In the scanning of the light beam, a mirror having a reflecting surface that receives the light beam from the light source is used, and the light beam is deflected by rotating the mirror, thereby scanning the light beam in a line.
The mirror is rotated by rotating a polygon mirror in one direction with a stepping motor (hereinafter referred to as “polygon method”) and a method of resonating a torsion bar equipped with a mirror (usually having one reflecting surface) (hereinafter referred to as “polygon method”). , "Galbano method") is mainly adopted. In any method, the rotation is performed by the operation unit (motor or the like) receiving the input of the drive signal.

The scanning light beam is detected by a light beam detector provided at a predetermined position in the scanning path. The detection signal of the light beam detector is used as a synchronization signal (reference signal) necessary for the control of exposing a predetermined position of the photosensitive member when the scanning state rises to a constant period and becomes a normal operation state.
On the other hand, the detection signal of the light beam detector is also used when adjusting the operation of the light beam to a scanning state of a predetermined period when the light beam scanning device is activated. For example, in a galvano scanning optical system created by MEMS (Micro Electro Mechanical Systems), feedback control using this detection signal has already been performed in order to adjust the amplitude of the vibrating mirror to be constant. In this adjustment, a method is employed in which the control operation is performed by forcibly turning on the light source during the period from when the vibrating mirror is activated to when the target scanning state is ensured.

However, when the method of adjusting to a predetermined scanning state using the detection signal of the light beam detector at the time of starting the light beam scanning device, etc., during the adjustment operation, it is usually more excessive than in normal operation. There is a problem that an unnecessary light beam is projected onto the photosensitive member with a light amount, which causes deterioration of the light source and the photosensitive member.
In Patent Document 1, in order to prevent deterioration of the photosensitive member caused by an unnecessary light beam at the time of starting the light beam scanning device, the light source passes through a sensor that outputs a synchronization signal when the light source is turned on. Controlling lighting is described.

However, in the above conventional technique, an unnecessary light beam is projected onto the photoconductor during the adjustment operation after the light source is turned on, and thus the above-described problem cannot be solved sufficiently.
The present invention has been made to solve the above-described problems of the prior art, and an object of the present invention is to perform an adjustment operation for setting a scanning state of a predetermined cycle from the start of a light beam scanning device that periodically scans a light beam emitted from a light source. It is to prevent the light beam and the photosensitive member from being deteriorated by preventing the light beam from being unnecessarily projected onto the photosensitive member, including during the process.

The present invention relates to a light beam scanning apparatus, a light source capable of lighting control for emitting a light beam, a mirror having a reflecting surface for receiving the light beam emitted from the light source, and an operation that operates upon receiving a drive signal. A light beam scanning means for periodically scanning the light beam reflected by the reflecting surface on a path passing through a predetermined exposure area by rotating the mirror by the operating section, and a period by the light beam scanning means. A light beam detecting means for detecting a projection light beam at a predetermined position on a path outside the predetermined exposure area of the scanned light beam and outputting a synchronization signal; and a phase of a drive signal of the operating portion of the light beam scanning means. Based on the above, a lighting control signal for turning on the light source is generated only when the light beam scanned by the light beam scanning unit is projected to the light beam detecting unit. Characterized in that and means.
In the present invention, a mirror having a reflecting surface that receives a light beam emitted from a light source that can be turned on is rotated by an operation of an operation unit that receives a drive signal, so that a predetermined exposure region and a region outside the predetermined exposure region are rotated. A light beam scanning method for periodically scanning a light beam reflected by the reflecting surface on a path passing through a light beam detecting means for detecting a projection light beam and outputting a synchronization signal, wherein the operating unit for displacing the mirror On the basis of the phase of the drive signal, a lighting control signal for turning on the light source is generated only at the timing when the periodically scanned light beam is projected to the light beam detecting means.

  According to the present invention, the light beam is not unnecessarily projected onto the photosensitive member, including during the adjustment operation for setting the scanning state in a predetermined cycle from the time when the light beam scanning device is started, and the light source and the photosensitive member are deteriorated. Can be prevented.

It is a figure which shows schematic structure of the light beam scanning apparatus which concerns on this invention. It is a block diagram which shows schematic structure of the control system of a light beam scanning apparatus (FIG. 1). It is a diagram explaining the LD forced lighting control signal generated based on the drive signal of the vibrating mirror that performs galvano scanning. It is a diagram explaining the LD forced lighting control signal of the next period generated based on the synchronous detection signal of the current period in the galvano scanning. FIG. 3 is a control flow chart of lighting of a light source from activation to termination of a light beam scanning device (galvano method) in an image forming apparatus. It is a diagram explaining the LD forced lighting control signal generated based on the drive signal of the mirror that performs polygonal scanning. FIG. 6 is a diagram for explaining a light LD forced lighting control signal of the next period generated based on a synchronization detection signal of the current period in polygon scanning. FIG. 3 is a control flow chart of lighting of a light source from start to end of a light beam scanning device (polygon method) in an image forming apparatus.

Embodiments according to the present invention will be described below with reference to the accompanying drawings.
The light beam scanning apparatus according to this embodiment is based on a method in which a light beam is line-scanned at a predetermined period by rotation of a mirror having a reflecting surface that receives a light beam emitted from a light source.
In this embodiment, as a light beam scanning device applied to an electrophotographic image forming apparatus (printer, digital copying machine, multifunction device, etc.), the light beam scanning device performs line scanning of the photosensitive member with a light beam. A mode for generating an electrostatic latent image will be described as an example.

A light beam scanning device applied to an image forming apparatus includes a synchronization detection sensor (light beam detection means) that detects a scanning light beam at a predetermined position on a scanning path and outputs a synchronization signal. This synchronization detection signal (hereinafter also referred to as “detection sensor output”) serves as a reference signal for normal image formation, and the light beam is raised to a predetermined scanning state at the time of start-up, and this scanning state at the time of operation. It is used for adjustment to maintain.
In the present embodiment, when the scanning light beam is projected to the synchronization detection sensor that outputs the synchronization detection signal used as described above, the control for lighting the light source only at the projection timing is performed by the method described below. Thus, the light beam is not unnecessarily projected onto the photosensitive member, and the light source and the photosensitive member are prevented from being deteriorated.
Since the galvano method and the polygon method are mainly employed as the light beam scanning method, each of the following embodiments will be described as Embodiments 1 and 2.

[Embodiment 1]
This embodiment relates to a galvano-type light beam scanning apparatus.
The galvano system has a structure in which a vibrator that integrates a reflecting surface (usually a single plane mirror) that receives a light beam from a light source is attached to the main body via a torsion bar. By the rotation, line scanning in the forward and reverse directions is performed at a constant cycle.
As a mirror (hereinafter referred to as “vibrating mirror”) used in the galvano system, a vibrating mirror manufactured by MEMS can be used. Among this type of oscillating mirror, a so-called moving coil type MEMS oscillating mirror in which a magnet is provided on the fixed (main body) side and a coil is formed on a vibrator that integrates a reflecting surface supported by a beam (torsion bar). Here it is used. According to this MEMS oscillating mirror, the mirror surface size can be reduced, and the torsional (rotation) vibration can be made by utilizing resonance, so that it can operate at high speed, but has low noise and low power consumption. There is.

“Schematic configuration of light beam scanning device”
FIG. 1 is a diagram illustrating a schematic configuration of a light beam scanning apparatus according to the present embodiment.
In FIG. 1, a laser beam emitted by an LD in an LD unit 1 including an LD as a light source, an LD driving unit, and the like is converted into a parallel beam by a collimator lens (not shown), and is projected onto the reflecting surface portion 21 of the vibrating mirror 2. When the MEMS oscillating mirror is employed as the oscillating mirror 2, the mirror driving control unit 24 controls the driving of the moving coil as the mirror driving unit 23, and the reflecting surface unit 21 (vibrator) is driven by the driving force transmitted from the mirror driving unit 23. By resonating, the reflecting surface portion 21 rotates and vibrates (rotates in the forward and reverse directions indicated by arrows in FIG. 1).

After the light beam projected on the reflection surface portion 21 is deflected and scanned by the vibration of the vibration mirror 2, the light beam image is projected onto the charged surface of the drum-shaped photoconductor 5 through the imaging lens 3 and the reflection mirror 4. Form an image. The laser light emitted from the LD is modulated based on the image signal, repeatedly turned on and off, and scanned in the main scanning direction repeatedly forward and backward as indicated by arrows in FIG. Simultaneously with this scanning, the photosensitive member 5 is rotated and sub-scanning is performed to form a two-dimensional electrostatic latent image based on the image signal on the surface of the photosensitive member 5 (hereinafter, this operation is also referred to as “optical writing”). ).
In addition, a synchronization detection sensor at a predetermined position outside the scanning area of the photoconductor 5 on the scanning path of the light beam, that is, a light beam that is scanned by repeating the main scanning direction forward and backward as shown in FIG. A front-end synchronization detection sensor SP6 and a rear-end synchronization detection sensor EP7 that detect the position are arranged. The signals detected by these sensors are used as control signals for performing normal optical writing on the basis of this signal as a synchronizing signal of a periodically scanned light beam (see “Control System of Light Beam Scanning Device” below). "See description.)

  After forming the electrostatic latent image, the electrostatic latent image formed on the photoconductor 5 is processed according to an image forming process of an electrophotographic image forming apparatus. That is, the electrostatic latent image on the photoconductor 5 is developed with a charged developer (toner), and then a transfer material such as transfer paper to which a charge opposite to the developer is applied to the photoconductor 5 at the transfer portion. The developer is transferred onto a transfer material (usually a paper medium) by being in close contact. In addition, after the transfer material is separated from the photoreceptor 5, the developer is heated and pressed in the fixing unit, whereby the developer is fused and fixed on the transfer material, thereby completing the image forming process.

"Control system of light beam scanning device"
A control system of the light beam scanning apparatus will be described.
FIG. 2 is a block diagram showing a schematic configuration of a control system of the light beam scanning apparatus shown in FIG.
The control system shown in FIG. 2 includes a configuration related to the drive control of the mirror drive unit 23 and the lighting control of the LD in the LD unit 1 shown in FIG. Control of the mirror drive unit 23 starts up the light beam scanning device so as to be in a predetermined scanning state that enables a normal image forming operation, and maintains the scanning state during operation so that the vibrating mirror 2 is maintained. Adjust the operation. The LD lighting control operates when a scanning light beam is projected onto the synchronization detection sensor and optical writing is performed in order to obtain the output of the synchronization detection signal.
Therefore, the control system shown in FIG. 2 includes a mirror drive unit 23 and a mirror drive control unit 24 that drive the vibrating mirror 2 (see FIG. 1) to be controlled, and an LD drive unit 12 that drives the control target LD 11 and LD 11. (See LD unit 1 in FIG. 1).

2 is under the control of a printer control unit 30 which is a main control unit of the image forming apparatus, a mirror drive control unit 24, an LD drive unit 12, a synchronization detection signal generation unit 15, a writing system. The clock generation unit 18, the phase synchronization clock generation unit 17, and the synchronization detection lighting control unit 16 are set to control the drive control of the vibrating mirror 2 and the lighting control operation of the LD 11. Note that the printer control unit 30 and the above-described units under the control of the printer control unit 30 can be implemented by a computer and software (program) driven by the computer.
The outputs of the synchronization detection sensors 6 and 7 (refer to the front-end synchronization detection sensor SP6 and the rear-end synchronization detection sensor EP7 in FIG. 1) are output as the synchronization detection signal DETP via the synchronization detection signal generation unit 15 and the phase synchronization clock generation unit 17 and It is used in each of the synchronization detection lighting control units 16.
The mirror drive control unit 24 outputs a mirror drive signal MD consisting of a periodic pulse (rectangular wave) determined according to the instructed control condition to a moving coil as the mirror drive unit 23 to drive the vibrating mirror 2. Further, the mirror drive control unit 24 outputs the synchronization signal MDS of the mirror drive signal MD to the synchronization detection lighting control unit 16.

The LD driving unit 12 controls lighting by controlling the current flowing through the LD 11 according to the image signal or the LD forced lighting signal BD, and generates a light beam.
The synchronization detection sensors 6 and 7 output a signal generated when a PD (photodiode) which is an optical sensor unit receives the light beam when the light beam scanned by the vibration mirror 2 passes. The synchronization detection signal generation unit 15 receives signal inputs from the synchronization detection sensors 6 and 7 and outputs a synchronization detection signal DETP serving as a reference for image writing to the phase synchronization clock generation unit 17 and the synchronization detection lighting control unit 16. .

The write clock generator 18 generates a clock WCLK for controlling the lighting of the LD 11 and outputs the clock WCLK to the phase synchronization clock generator 17. The phase synchronization clock generation unit 17 receives the synchronization detection signal DETP and the clock WCLK, and outputs the clock CLK synchronized with the timing of the synchronization detection signal DETP to the LD drive unit 12 and the synchronization detection lighting control unit 16.
The synchronization detection lighting control unit 16 turns on the LD forced lighting signal BD for a predetermined period when the synchronization detection sensors 6 and 7 detect the synchronization detection signal DETP, and instructs the LD driving unit 12 to turn on the LD 11. To do.
This LD forcible lighting control is performed based on the synchronization signal MDS of the mirror drive signal MD, the synchronization detection signal DETP, and the clock CLK generated by the phase synchronization clock generator 17 in accordance with the control instruction of the printer controller 30. This LD forcible lighting control is an operation specific to this embodiment, and will be described in detail in an operation example of “LD forcible lighting control” below.

Further, the LD 11 is controlled to be turned on according to an image signal input according to the clock CLK under the control of the LD driving unit 12 and emits a light beam of an optical pulse train. The timing to start writing in accordance with the image signal is based on the timing at which the synchronization detection signal DETP is detected, and the elapsed time set in units of the number of clocks from the timing in consideration of the arrangement of the optical elements of the light beam scanning device. The image can be formed in a predetermined arrangement on the paper medium.
The printer control unit 30 sets the amplitude of the oscillating mirror 2 according to, for example, printing conditions, and the mirror drive control unit 24 performs control to oscillate the oscillating mirror 2 with a predetermined amplitude according to the setting of the printer control unit 30. . The light beam of the optical pulse train emitted from the LD 11 is deflected by the oscillating mirror 2, and image writing is started from the adjusted predetermined position on the photosensitive member 5. Note that the amplitude of the oscillating mirror 2 is adjusted at a necessary timing at the time of start-up after activation and at the time of optical writing operation.

“LD forced lighting control”
Next, an operation example of LD forced lighting control will be described.
The operation example described below is an example in which when the scanning light beam is projected to the synchronization detection sensors 6 and 7, the LD 11 is forcibly turned on at a scanning timing that makes it possible to eliminate unnecessary light beam emission. is there.
For this purpose, the LD 11 is forcibly lit only at the scanning timing at which the scanning light beam is projected to the synchronization detection sensors 6 and 7, and the drive signal MD (actually, the mirror drive signal MD for operating the vibrating mirror 2 used for scanning). The control signal for forced lighting is generated on the basis of the phase of “the driving signal MD” for the sake of convenience.
By generating the LD forcible lighting control signal BD for performing the LD forcible lighting control at the timing as described above, it becomes possible to eliminate the exposure of the photoconductor 5 by the light beam that is unnecessary for the startup after the startup. Moreover, by generating the LD forced lighting control signal BD based on the phase of the drive signal MD for operating the oscillating mirror 2, the intended lighting timing can be set appropriately.

FIG. 3 is a diagram for explaining the LD forced lighting control signal BD generated based on the drive signal MD of the oscillating mirror 2.
When a moving coil type MEMS oscillating mirror is used as a galvano-type mirror, the drive signal MD is a rectangular wave, as shown by “mirror drive signal” in FIG. The rectangular wave has an operation cycle of the oscillating mirror 2 and has a waveform in which the peak values are normally equal and the timings of rising (rising) and falling (+) voltage are alternately present.

The light beam reflected by the oscillating mirror 2 to which a positive voltage is applied to the moving coil and a positive rotational force is applied during the period from the rise to the fall of the drive signal scans the photoconductor 5 in the positive direction (see FIG. 1, see).
In a period in which a plus voltage is applied as the drive signal MD, it is a timing that can be detected by the rear-end synchronization detection sensor EP7. In other words, a period that starts after “t1” time after the drive signal MD by the positive voltage rises and ends after “t1” time and after “t2” time is a timing at which the rear-end synchronization detection sensor EP7 can detect. Therefore, only during this period, the LD compulsory lighting signal BD (this signal is referred to as “rear end synchronous lighting signal”) that enables the rear end synchronization detection is output, and the LD 11 is turned on. It should be noted that the period during which the rear end synchronized lighting signal is output usually does not pass the period in which the plus voltage is applied as the drive signal MD.

On the other hand, during the period from the rise to the fall of the drive signal MD, a negative voltage is applied to the moving coil, and the light beam reflected by the oscillating mirror 2 to which a reverse rotational force is applied, scans the photoconductor 5 in the reverse direction. (See FIG. 1).
In a period in which a negative voltage is applied as the drive signal MD, it is a timing that can be detected by the tip synchronization detection sensor SP6. In other words, a period that starts after “t1 ′” time after the drive signal MD with a negative voltage rises and ends after “t1 ′” time and after “t2 ′” time is a timing that can be detected by the tip synchronization detection sensor SP6. is there. Therefore, only during this period, the LD forcible lighting signal BD (this signal is referred to as “tip synchronized lighting signal”) that enables tip synchronization detection is output, and the LD 11 is lit. It should be noted that the period during which the tip synchronous lighting signal is output usually does not pass the period during which a negative voltage is applied as the drive signal MD.

For example, the rear end synchronized lighting signal and the front end synchronized lighting signal shown in FIG. 3 are output only at timings that can be detected by the synchronization detection sensors 6 and 7 as operations at startup after startup. ing.
At the time of start-up after startup, the amplitude of the oscillating mirror 2 gradually increases as shown by the light beam position in the figure, and the LD 11 lit by the rear end synchronized lighting signal and the front end synchronized lighting signal in the second period. It is shown that the light beam is detected by the rear end synchronization detection sensor EP7 and the front end synchronization detection sensor SP6. In addition, the signal detected at this time is in a state shown as a rear end synchronization detection sensor output and a front end synchronization detection sensor output.

By the method shown in FIG. 3, the operation of outputting the rear end synchronized lighting signal and the front end synchronized lighting signal as the LD forced lighting control signal BD can be performed from the beginning to the end.
However, the output period of the LD forcible lighting control signal BD determined in advance at “t1” and “t2” is determined to be longer in consideration of the fact that various operating conditions fluctuate during startup after startup. Therefore, when the operation state of the light beam scanning is stabilized once it stands up, there is room for optimizing the setting of the output period suitable for the original purpose of eliminating unnecessary lighting. That is, when the operation state of the light beam scanning is stabilized after rising, the rise time of the mirror drive signal MD, which has been used as the reference time for defining the output period of the LD forced lighting control signal BD so far, By changing the operation at the time of outputting the synchronization detection signal DETP and switching the operation to shorten the output period of the LD forced lighting control signal BD, unnecessary lighting time of the LD 11 can be shortened, and no detection omission occurs. An appropriate output period of the LD forced lighting control signal BD can be determined.

FIG. 4 is a diagram for explaining the LD forced lighting control signal BD of the next cycle generated based on the synchronization detection signal of the current cycle when the operation of the light beam scanning is stable.
In FIG. 4, when the operation state of the light beam scanning is stabilized, the amplitude and period of the vibrating mirror 2 do not change so much as shown in the light beam position in the figure, and are synchronized with a substantially constant time of each period. The light beams are scanned in a state in which the light beams are detected by the detection sensors 6 and 7 (the rear end synchronization detection sensor EP7 and the front end synchronization detection sensor SP6).
In such a stable operation state, the reference time for determining the output period of the LD forced lighting control signal BD (synchronization detection lighting signal) is set to the time when the synchronization detection signals DETP of the synchronization detection sensors 6 and 7 are output. As shown in the case of the end synchronization detection sensor output, this synchronization detection sensor output starts after a predetermined time “t3” and ends after “t3” time and further “t4” time (shorter than “t2” in FIG. 3). The trailing edge synchronous lighting signal ON period in which the period can be detected by the trailing edge synchronization detection sensor EP7 can be determined. For the tip synchronization detection sensor SP6, the tip synchronization lighting signal ON period can be determined by the same method.

“Light source lighting control flow”
Next, the control operation of the light beam scanning device in the image forming apparatus accompanied with the “LD forced lighting control” will be described.
FIG. 5 is a control flow chart of lighting of the light source from the start to the end of the light beam scanning device in the image forming apparatus. This control flow is executed when the printer control unit 30 receives an input of a job requesting print output, for example.
When the printer control unit 30 receives an input of a job requesting print output, the printer control unit 30 starts the control flow shown in FIG. 5 and first starts driving the vibrating mirror 2 (step S101).

With reference to FIG. 3 in the “LD forcible lighting control” described above, the operation at the start-up until the vibration of the vibration mirror 2 is stabilized until the vibration of the vibration mirror 2 is started, that is, the operation state of the light beam scanning is stabilized. The LD forced lighting control operation (that is, the lighting operation performed by determining the ON periods of the synchronous lighting signals “t2” and “t2 ′” based on the drive signal MD of the vibrating mirror 2) is performed.
In the control flow of FIG. 5, the LD 11 is turned on after “t1” after the drive signal MD of the oscillating mirror 2 rises (step S102), and the synchronous lighting signal ON period determined as the “t2” time from the lighting of the LD11. After the elapse of time, the LD 11 is turned off (step S103).

Next, whether or not the light beam scanning operation has started and is in a stable state is confirmed by examining whether or not a predetermined synchronization detection signal DETP has been obtained (step S104).
For this confirmation, in a state where the operation of the light beam scanning is stable, a method of checking the presence or absence of the detection signal DETP by providing the sensor in advance at a position where the detection signal DETP of the synchronization detection sensors 6 and 7 is output, Alternatively, a method of checking whether or not the detection signals DETP of the synchronization detection sensors 6 and 7 are output at a predetermined timing as the output timing of the synchronization detection signal DETP in a state where the operation of the light beam scanning is stable is used.
If the predetermined synchronization detection signal DETP is not obtained in step S104 (step S104-NO), the light beam scanning operation has not reached a stable state, so the LD forced lighting control operation in steps S102 and S103 is performed with the light beam scanning. Repeat until the operating state of is stable.

On the other hand, when the predetermined synchronization detection signal DETP is obtained in step S104 (step S104-YES), the light beam scanning operation state is determined based on the determination that the light beam scanning operation is stable. As the operation to be performed after the stabilization, the LD forced lighting control operation described with reference to FIG. 4 in the “LD forced lighting control” (that is, the “t4” ON period of the synchronous lighting signal is set based on the synchronization detection signal). Lighting operation).
In the control flow of FIG. 5, the LD 11 is turned on after “t3” time has elapsed since the synchronization detection signal DETP was output (step S105), and the synchronous lighting signal ON period determined as “t4” time from the turning on of the LD 11 After the elapse of time, the LD 11 is turned off (step S106).

Since the operation up to step S106 is in an operation state in which the light beam scanning device can perform the image forming operation normally, the control proceeds to the optical writing, and the electrostatic latent image is applied to the photosensitive member 5 by the light beam scanning device. After the image is formed, the electrostatic latent image formed on the photoconductor 5 is subjected to an image forming process according to an electrophotographic image forming process (step S107).
When print output is performed through the image forming process, the processing of the requested job is completed, so the LD 11 is turned off, and this control flow ends.

According to this embodiment, the LD forced lighting control operation described with reference to FIG. 3 (that is, based on the drive signal MD of the oscillating mirror 2, the synchronous lighting signal is turned on starting after “t1” and “t1 ′”. By performing a lighting operation performed for a predetermined period, the photosensitive member 5 is not exposed by an unnecessary light beam at the time of start-up after startup, so that the deterioration of the photosensitive member 5 and the LD 11 can be prevented. By generating the LD forcible lighting control signal BD based on the phase of the drive signal MD for operating the oscillating mirror 2, the intended lighting timing can be set appropriately, so that the degradation of the LD 11 can be further reduced.
Further, when the light beam scanning becomes stable after the start-up, the LD forced lighting control operation described with reference to FIG. 4 (that is, the “t4” ON period of the synchronous lighting signal is set based on the synchronous detection signal). By performing the predetermined lighting operation), the output period of the LD forcible lighting control signal BD can be further shortened, and appropriate LD forcible lighting can be performed without causing detection omission.

[Embodiment 2]
This embodiment relates to a polygonal light beam scanning apparatus.
“Schematic configuration of light beam scanning device”
The polygon type light beam scanning apparatus basically has the same configuration as the configuration shown in FIG. 1 (FIG. 1) except for the mirror in the galvano mode of [Embodiment 1]. That is, the polygon type light beam scanning apparatus can be implemented by a configuration in which the oscillating mirror 2 and the mirror driving unit 23 in the configuration of FIG. 1 are replaced with a polygon mirror and a stepping motor adopted in the polygon method. Therefore, the configuration other than the mirror is referred to the above description regarding FIG. 1, and the description is omitted here.

The polygon system is a scanning system that receives a light beam from a light source with a rotating polygon mirror (polyhedral reflector) and deflects the light beam. The polygon mirror is rotated at a constant speed by a stepping motor, and the working reflecting surface is switched. Line scanning is performed at a period of.
The scanning period of the light beam can be changed by controlling the rotation speed of the stepping motor.
In the light beam scanning by the polygon mirror rotating at a constant speed, the light beam projected on each reflecting surface of the polygon mirror is deflected and scanned, and then projected on the charged surface of the drum-shaped photoconductor 5, and the vibrating mirror. As in the case of 2, scanning is periodically performed in one main scanning direction without forward and reverse scanning directions. Simultaneously with this scanning, the photosensitive member 5 is rotated and sub-scanning is performed to form a two-dimensional electrostatic latent image based on the image signal on the surface of the photosensitive member (hereinafter, this operation is also referred to as “optical writing”).
Further, one synchronization detection sensor is basically arranged at a predetermined position outside the front end of the photosensitive member 5 on the scanning path of the light beam (hereinafter, the synchronization detection sensor is referred to as “tip synchronization detection sensor SP6” in FIG. 1). ). A signal detected by this sensor is used as a synchronization signal of a periodically scanned light beam for control for performing normal optical writing on the basis of this signal.

  After forming the electrostatic latent image, the electrostatic latent image formed on the photoconductor 5 is processed according to an image forming process of an electrophotographic image forming apparatus. That is, the electrostatic latent image on the photoconductor 5 is developed with a charged developer (toner), and then a transfer material such as transfer paper to which a charge opposite to the developer is applied in the transfer portion is in close contact with the photoconductor. As a result, the developer is transferred onto a transfer material (usually a paper medium). In addition, after the transfer material is separated from the photoreceptor 5, the developer is heated and pressed in the fixing unit, whereby the developer is fused and fixed on the transfer material, thereby completing the image forming process.

"Control system of light beam scanning device"
A control system of the light beam scanning apparatus of this embodiment will be described.
The control system of the light beam scanning apparatus of this embodiment has basically the same configuration as the control system shown in FIG. 2 in the galvano system of [Embodiment 1] except for the following parts. In other words, since the polygon type light beam scanning apparatus employs a polygon mirror and a stepping motor, the mirror drive unit 23 and the mirror drive control unit 24 have a configuration adapted to drive control of the stepping motor and the stepping motor. It will be. The mirror drive control unit 24 outputs a mirror drive signal (a drive signal of a stepping motor that operates the mirror) MD and a synchronization signal MDS of the drive signal in the same manner as in the above embodiment. The number of synchronization detection sensors used is basically one (hereinafter, the synchronization detection sensor is referred to as “synchronization detection sensor 6” in FIG. 2).
In addition, about the structure of a common part other than the above, it shall refer to the said description regarding FIG. 2, and description is abbreviate | omitted here.

“LD forced lighting control”
Next, an operation example of LD forced lighting control will be described.
Hereinafter, an operation example in which the LD 11 is forcibly turned on at a scanning timing that can eliminate unnecessary light beam emission when a scanning light beam is projected onto the synchronization detection sensor 6 will be described.
In this example, the LD 11 is forcibly lit only at the scanning timing when the scanning light beam is projected to the synchronization detection sensor 6 and the drive signal MD (actually, the synchronization signal MDS of the mirror drive signal MD is used to operate the polygon mirror used for scanning). However, for the convenience of explanation, the control signal for forced lighting is generated based on the phase of “drive signal MD”).

Since the relationship between the phase of the drive signal MD and the position of the light beam does not change during operation and is fixed, the position on the scanning path of the light beam at a specific phase of the drive signal MD of the polygon mirror is also specified. . The synchronization detection sensor 6 is provided at a predetermined position on the scanning path of the light beam. Therefore, if the polygon mirror has a constant rotation speed, the position of the synchronization detection sensor 6 on the scanning path corresponding to the specific phase of the drive signal MD, that is, the timing of the LD forced lighting control signal BD is specified by the drive signal MD. It can be determined by the time from the phase.
Note that the relationship between the phase of the drive signal MD and the generation timing of the synchronization detection signal differs depending on the rotation angle rotated by the stepping motor and the attachment angle of the reflecting surface of the polygon mirror, so the drive signal MD and the synchronization detection signal in the operating state are different. The generated angle is obtained in advance, the data is held, and the timing for turning on the light source is calculated according to the rotation speed (rotation speed) of the stepping motor at the start of operation.
By generating the LD forcible lighting control signal BD for performing the LD forcible lighting control at the timing determined as described above, it is possible to eliminate the exposure of the photoconductor 5 due to the light beam unnecessary for the startup after the start-up. In addition, the intended lighting timing can be set appropriately.

FIG. 6 is a diagram illustrating the LD forced lighting control signal BD generated based on the polygon mirror drive signal MD.
When a polygon mirror is used, the drive signal MD is a rectangular wave as shown by “drive signal” in FIG. In the example of FIG. 6, the rectangular wave of the drive signal MD has the same period as the period of switching of the reflection surface of the polygon mirror, and the crest values are equal and the rising and falling edges of the plus (+) and minus (−) voltages alternately. This waveform has the timing of.

The phase of the drive signal MD for determining the forced lighting timing may basically be either a rising or falling edge of a rectangular wave. In this embodiment, as shown in FIG. 6, the phase of the drive signal MD that is further away from the LD forced lighting control period (tip synchronized lighting signal ON period), that is, after the drive signal MD by a positive voltage falls. The period starting after time t5 and ending after time t6 after time t5 is a timing at which the tip synchronization detection sensor SP6 can detect. Therefore, only during this period, the LD forced lighting signal BD (tip synchronized lighting signal) that enables the tip synchronized detection is output, and the LD 11 is lit.
The LD forced lighting signal BD is repeatedly output based on the same phase of the drive signal MD.

The tip synchronous lighting signal shown in FIG. 6 shows an example that is output only at a timing that can be detected by the synchronous detection sensor 6, for example, as a startup operation after startup.
When starting up after startup, it is a time until the polygon mirror reaches a stable desired rotational speed, and the rotational speed gradually approaches a constant value. During this time, “t5” time after the drive signal MD falls. The lighting timing is determined by the time of the LD compulsory lighting signal BD that starts and ends after “t6” time and after “t6” time, and the scanning position of the light beam to be turned on is not constant and varies. As a result, as shown in FIG. 6, the tip synchronization detection sensor output (synchronization detection signal DETP) in the tip synchronization detection sensor SP6 does not have a constant period.
For this reason, a margin that can be detected by the tip synchronization detection sensor SP6 even if the scanning position fluctuates is added to the output period of the LD forced lighting control signal BD.

By the method shown in FIG. 6, the operation of outputting the front end synchronized lighting signal as the LD forced lighting control signal BD can be performed from the beginning to the end.
However, when starting up after startup, the output period of the LD forcible lighting control signal BD is determined in advance with a margin in consideration of the fact that various operating conditions such as fluctuations in the rotational speed fluctuate. When the operation state of the light beam scanning is stabilized, such as once rising and the rotation speed reaching a desired value, there is room for optimizing the setting of the output period suitable for the original purpose of eliminating unnecessary lighting. That is, when the operation state of light beam scanning is stabilized after rising, the synchronization detection sensor 6 indicates when the drive signal MD falls (rises), which has been the reference time for defining the output period of the LD forced lighting control signal BD. By changing the operation when the synchronization detection signal DETP is output and switching the operation for shortening the output period of the LD forced lighting control signal BD, unnecessary lighting time of the LD 11 can be shortened, and detection omission may occur. An appropriate output period of the LD forced lighting control signal BD can be determined.

FIG. 7 is a diagram for explaining the LD forced lighting control signal BD of the next cycle generated based on the synchronization detection signal of the current cycle when the operation of the light beam scanning is stable.
In FIG. 7, when the operation state of the light beam scanning is stabilized, as shown in the light beam position in the figure, the rotation speed does not change so much, and the tip synchronization detection sensor SP6 is detected at a substantially constant time of each cycle. The light beam is scanned in a state where the light beam is detected.
In such a stable operation state, the reference time for determining the output period of the LD forced lighting control signal BD (synchronization detection lighting signal) is set to the time of output of the synchronization detection signal DETP of the synchronization detection sensor 6, that is, the tip synchronization detection of FIG. As shown in the sensor output, leading edge synchronization detection is started after a predetermined time “t7” from this synchronization detection sensor output and ends after “t7” time and further “t8” time (shorter than “t6” in FIG. 6). The tip synchronous lighting signal ON period during which detection by the sensor SP6 is possible can be determined.

“Light source lighting control flow”
Next, the control operation of the light beam scanning device in the image forming apparatus with the “LD forced lighting control” of the present embodiment will be described.
FIG. 8 is a control flow chart of lighting of the light source from the start to the end of the light beam scanning device in the image forming apparatus of this embodiment. This control flow is performed when the printer control unit 30 receives an input of a job requesting print output, for example.
When the printer control unit 30 receives an input of a job requesting print output, the printer control unit 30 starts the control flow shown in FIG. 8 and first starts driving the polygon mirror (step S201).

With reference to FIG. 6 in the above-mentioned “LD forced lighting control”, an operation at the time of starting until the polygon mirror rotation speed is stabilized after the polygon mirror driving is started, that is, the operation state of the light beam scanning is stabilized. The LD forced lighting control operation (that is, the lighting operation performed by determining the ON period of “t6” of the synchronous lighting signal based on the driving signal MD of the polygon mirror) is performed.
In the control flow of FIG. 8, the LD 11 is turned on after “t5” after the drive signal MD of the polygon mirror falls (step S202), and the synchronous lighting signal (LD) defined as “t6” time from the turning on of the LD 11 After the elapse of the forced lighting control signal BD) ON period, the LD 11 is turned off (step S203).

Next, it is confirmed whether or not a predetermined synchronization detection signal DETP is obtained by checking whether or not the light beam scanning operation has started and is in a stable operation state (step S204).
In this confirmation, in the state where the operation of the light beam scanning is stable, the synchronization detection is performed at a timing (time interval corresponding to the rotational speed at the time of stability) that is predetermined as the output timing of the detection signal DETP of the synchronization detection sensor 6. A method of checking whether or not the detection signal DETP of the sensor 6 is output is used.
If the predetermined synchronization detection signal DETP is not obtained in step S204 (step S204-NO), since the light beam scanning has not reached a stable operation state, the LD forced lighting control operation in steps S202 and S203 is performed. Repeat until the operating condition is stable.

On the other hand, when the predetermined synchronization detection signal DETP is obtained in step S204 (step S204-YES), the light beam scanning operation state is determined based on the determination that the light beam scanning is in a stable operation state. As the operation to be performed after the stabilization, the LD forced lighting control operation described with reference to FIG. 7 in the “LD forced lighting control” of the present embodiment (that is, “t8 of the synchronous lighting signal based on the synchronous detection signal”). “Lighting operation performed by setting an ON period”.
In the control flow of FIG. 8, the LD 11 is turned on after the elapse of “t7” time from the output of the synchronization detection signal DETP (step S205), and the synchronous lighting signal ON period determined as the “t8” time from the turning on of the LD 11 After the elapse of time, the LD 11 is turned off (step S206).

Since the operation up to step S206 is in an operation state in which the light beam scanning apparatus can normally perform the image forming operation, the control shifts to the optical writing, and the light beam scanning apparatus causes the electrostatic latent image on the photoconductor 5. After the image is formed, the electrostatic latent image formed on the photoreceptor 5 is subjected to an image forming process according to an electrophotographic image forming process (step S207).
When the print output is performed through the image forming process, the processing of the requested job is completed, so the LD 11 is turned off and the control flow ends (step S208).

According to the present embodiment, the LD forcible lighting control operation described with reference to FIG. 6 (that is, the lighting operation performed by determining the ON period of “t6” of the synchronous lighting signal based on the driving signal MD of the polygon mirror) By performing the above, the photosensitive member 5 is not exposed by an unnecessary light beam at the time of start-up after startup, so that the deterioration of the photosensitive member 5 and the LD 11 can be prevented, and the driving for operating the polygon mirror is performed. By generating the LD forced lighting control signal BD based on the phase of the signal MD, the intended lighting timing can be set appropriately, and the degradation of the LD 11 can be further reduced.
Further, when the light beam scanning is in a stable operation state after startup, the LD forced lighting control operation described with reference to FIG. 7 (that is, the synchronous lighting signal starting after “t7” based on the synchronous detection signal). By performing the lighting operation performed by setting the ON period of time, the output period of the LD forcible lighting control signal BD can be further shortened, and appropriate LD forcible lighting can be performed without causing detection failure.

  2 .. Vibrating mirror, 5 .. Photoconductor, 6 .. Front end synchronization detection sensor SP, 7. Control unit, 23..Mirror drive unit, 30..Printer control unit.

JP 2005-305782 A

Claims (5)

A light source capable of lighting control that emits a light beam;
A mirror having a reflecting surface for receiving a light beam emitted from the light source and an operation unit that operates in response to an input of a drive signal, and the mirror is rotated by the operation unit, so that the path passes through a predetermined exposure region; A light beam scanning means for periodically scanning the light beam reflected by the reflecting surface;
A light beam detecting means for detecting a projection light beam at a predetermined position on a path outside the predetermined exposure area of the light beam periodically scanned by the light beam scanning means and outputting a synchronization signal;
A lighting control signal for turning on the light source only at the timing when the light beam scanned by the light beam scanning unit is projected to the light beam detecting unit based on the phase of the drive signal of the operating unit of the light beam scanning unit. And a light beam scanning device. The light beam scanning device according to claim 1.
The light beam scanning device includes a component in which a rotary vibrator and a mirror as the operating unit are integrated. The light beam scanning device according to claim 1.
The light beam scanning unit includes a motor as the operating unit and a polygon mirror rotated by the motor as constituent elements.   An image forming apparatus comprising: the light beam scanning device according to claim 1, wherein the object to be scanned in the predetermined exposure region is a photoconductor that generates an image by light beam exposure. By rotating a mirror having a reflecting surface that receives a light beam emitted by a light source that can be turned on by an operation unit that receives an input of a drive signal, a projection light beam is emitted outside the predetermined exposure area and the predetermined exposure area. A light beam scanning method for periodically scanning a light beam reflected by the reflecting surface on a path passing through a light beam detecting means for detecting and outputting a synchronization signal,
A lighting control signal for turning on the light source is generated based on the phase of the drive signal of the actuating unit that displaces the mirror, only when the light beam that is periodically scanned is projected to the light beam detecting means. A light beam scanning method.

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