JP2008096936A - Optical writing apparatus and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical writing apparatus in which an initialization operation is properly performed to determine an appropriate electric current for lighting laser even when the scanning period time for specular reflection state is remarkably reduced due to increase in speed of an image forming apparatus, and to provide an image forming apparatus. <P>SOLUTION: When respective electric current values are determined, a scanning time for a line is made longer than the execution time for determining the electric current value. Concretely, the rotation speed of a deflection means which scans the laser light from a laser when the respective electric current values are determined is made slower than the rotation speed of the deflection means in image forming (S102), and the period of the laser light scanning is made long. Thus, the initialization operation is properly performed to determine the appropriate electric current for lighting the semiconductor laser even when the scanning period time for the specular reflection state is remarkably reduced due to increase in speed of an image forming apparatus. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical writing apparatus and an image forming apparatus that form a latent image on a photosensitive member by deflecting and scanning laser light emitted from a laser by a deflecting unit.

  2. Description of the Related Art Conventionally, in an image forming apparatus that forms an electrostatic latent image by irradiating a photosensitive member with light emitted from a semiconductor laser, an initialization operation for determining a current value for turning on the semiconductor laser is required. In this initialization operation, the semiconductor laser is turned on with a two-stage current value, and the amount of light at that time is detected by a light amount sensor provided inside the semiconductor laser unit. This is a step of calculating an appropriate current value for lighting (see Patent Documents 1 and 2).

JP 2004-153118 A JP 2005-129842 A

  By the way, in such an image forming apparatus, the semiconductor laser light is reflected by the polygon mirror, and is irradiated onto the photoconductor through a plurality of lenses and a reflecting mirror. In this case, if the laser light is reflected by the polygon mirror under the optical conditions of regular reflection (incident angle 90 degrees), the reflected light returns directly into the semiconductor laser unit and is detected by the light quantity sensor. This phenomenon is called return light. Since this return light is generated every scanning cycle by the polygon mirror, the above-described initialization operation is performed within a scanning time of one cycle which becomes a regular reflection condition.

  However, in recent years, with an increase in the speed of an image forming apparatus, the time of one scanning period that becomes a regular reflection condition has been remarkably shortened by means such as increasing the number of polygon mirrors and increasing the rotational speed. As a result, the return light generated during the initialization operation of the semiconductor laser is also detected by the light quantity sensor, and there is a problem that the lighting current of the semiconductor laser cannot be obtained appropriately.

  The present invention has been made in view of the above, and an appropriate current value for turning on the laser is obtained even when the time of one scanning period that becomes a regular reflection condition is significantly shortened by speeding up the image forming apparatus. It is an object to provide an optical writing apparatus and an image forming apparatus that can appropriately execute an initialization operation to be determined.

  In order to solve the above-described problems and achieve the object, the invention according to claim 1 is an optical writing apparatus for forming a latent image on a photosensitive member by deflecting and scanning a laser beam emitted from a laser by a deflecting unit. A current value determining means for determining a threshold current value at which the laser starts to emit light and a bias current value for enabling the laser to emit light immediately after a light emission command is received; and At the time of determination, the rotation speed of the deflection unit is set higher than the rotation speed of the deflection unit during image formation so that the scanning time of one line by the deflection unit becomes longer than the execution time of the current value determination process. And a scanning time extension means for setting it late.

  According to a second aspect of the present invention, in the optical writing apparatus according to the first aspect, the light amount of the laser when the current value determining means determines the current values is set to the light amount of the laser during image formation. A light amount adjusting means for reducing the amount of light is provided.

  According to a third aspect of the present invention, in the optical writing device according to the first aspect, the first optical path blocking means for blocking the optical path from the deflecting means to the photoconductor during execution of the current value determining means. Prepare.

  According to a fourth aspect of the present invention, in the optical writing apparatus according to the first aspect of the present invention, the optical value writing means further comprises a second optical path blocking means for blocking an optical path from the laser to the deflecting means during execution of the current value determining means. .

  According to a fifth aspect of the present invention, there is provided an image forming apparatus comprising: a photosensitive member; a charging device that uniformly charges the surface of the photosensitive member; and exposing the photosensitive member after the uniform charging to form an electrostatic latent image. The optical writing device according to claim 1, a developing device for developing an electrostatic latent image formed on the photoconductor, and a transfer for transferring the developed image from the photoconductor to a recording medium. And a fixing device for fixing the developed image transferred to the recording medium.

  According to the present invention, when each current value is determined, the rotation speed of the deflecting unit that scans the laser beam is made slower than the rotation speed of the deflecting unit at the time of image formation, and the execution time of each current value determination process By making the scanning time of one line longer than that, it is suitable for turning on the laser even if the time of one scanning period that becomes a specular reflection condition becomes remarkably short by speeding up the image forming apparatus. There exists an effect that the initialization operation | movement which determines an electric current value can be performed appropriately.

  Exemplary embodiments of an optical writing apparatus and an image forming apparatus according to the present invention are explained in detail below with reference to the accompanying drawings.

[First Embodiment]
A first embodiment of the present invention will be described with reference to FIGS. In this embodiment, as an image forming apparatus, an electrophotographic system is formed in which a laser image is irradiated on a photosensitive drum to form an electrostatic latent image, and then a toner image corresponding to the electrostatic latent image is formed on a paper medium. This is an example in which an image forming apparatus employing the above is applied.

  FIG. 1 is a longitudinal front view showing the internal structure of the image forming apparatus according to the first embodiment of the present invention. As shown in FIG. 1, the image forming apparatus includes a scanner unit 23 that is an apparatus that captures an image from a paper document, and an engine unit 200 that forms an image captured by the scanner unit 23.

  The scanner unit 23 is a part that converts the information of the document 100 into an image signal by scanning and exposing the document 100 placed on the document table 110. Inside the scanner unit 23, scan exposure is performed by an exposure lamp 120 movable along the document table 110. The reflected light of the document 100 is photoelectrically converted by the CCD sensor 180 after passing through the carriage mirror 130, the first half scan mirror 140 and the second half scan mirror 150, the imaging mirror 160, and the optical lens 170, and then the intensity of the reflected light is increased. It becomes an electric signal according to. The image signal generated by the photoelectric conversion is subjected to image processing by the image processing unit 20 (see FIG. 3), and then transmitted to the engine unit 200.

  In the engine unit 200, the photoconductor drum 5 that rotates uniformly and is uniformly charged by the charging charger 202, which is a charging device, is exposed with laser light from the semiconductor laser exposure device 201 to generate an electrostatic latent image. The electrostatic latent image generated on the photosensitive drum 5 is developed with toner by the developing device 203 to become a visualized toner image.

  On the other hand, the transfer paper 207 which has been fed and conveyed from the paper feed tray 205 in advance by the paper feed roller 204 and has been waiting by the registration roller 206 is conveyed in synchronism with the drive of the photosensitive drum 5 and transferred by the transfer device. The toner on the photosensitive drum 5 is electrostatically transferred to the transfer paper 207 by the charger 208, and the transfer paper 207 is separated from the photosensitive drum 5 by the paper separation charger 209. After the separation, the toner image on the transfer paper 207 is heated and fixed by the fixing device 210 and discharged to the discharge tray 212 by the discharge roller 211. On the other hand, the toner image remaining on the photosensitive drum 5 after electrostatic transfer is pressed against and removed from the photosensitive drum 5 by the cleaning device 213, and the photosensitive drum 5 is neutralized by the irradiation light of the neutralizing lamp 214. As described above, the image forming apparatus forms an image by repeating these series of processes.

  The configuration of the semiconductor laser exposure apparatus 201, which is an optical writing apparatus in the present embodiment, will be described below with reference to FIGS.

  FIG. 2 is a schematic diagram schematically showing the configuration of the semiconductor laser exposure apparatus 201. As shown in FIG. 2, the semiconductor laser exposure apparatus 201 is an optical apparatus configured so that laser light scans in a direction perpendicular to the rotation direction on the photosensitive drum 5, and a laser diode 8 (FIG. 3). And LD unit 1 that emits laser light from the laser diode 8 and includes a LD driver 9 (see FIG. 3) that performs lighting control of the laser diode 8, adjustment of the light amount, and the like, and a polygon that is deflection means for deflecting and scanning the laser light A mirror (rotating polygonal mirror) 2, an f-θ lens 3 that is an imaging lens for converging laser light, a reflection mirror 4, a photosensitive drum 5, a synchronization detection mirror 6, and a light receiving element 7 that detects laser light for synchronization detection. Consists of The laser light of the laser diode 8 lit by the current supplied from the LD driver 9 is reflected by the polygon mirror 2, condensed by the f-θ lens 3, reflected by the reflection mirror 4, and then the photosensitive drum 5. Is irradiated. In addition, a synchronization detection mirror 6 is disposed on a scanning line deviated from the laser beam path irradiated onto the photosensitive drum 5. The laser beam reflected by the synchronization detection mirror 6 is detected by the light receiving element 7 in order to detect the scanning period of the laser beam.

  FIG. 3 is a block diagram showing a reading control system of the image forming apparatus. As shown in FIG. 3, in addition to the scanner unit 23 (semiconductor laser exposure apparatus 201), the image forming apparatus includes an image processing unit 20 that is a processing unit that generates a writing signal from image data, and a display unit for an operator. And an operation / display unit 21 serving as input means, a controller 22 serving as a device for controlling image data fetching, and the like, and a network I / F 24 that receives print requests from the outside.

  In addition to the configuration described above, the semiconductor laser exposure apparatus 201 is a circuit that controls the photodiode 25 that converts the amount of light into a voltage value in response to light emitted by the laser diode 8 itself, and a circuit that controls the semiconductor laser exposure apparatus 201. 15. A polygon motor 10 for rotating the polygon mirror 2 and a polygon motor driver 11 for controlling the rotation of the polygon motor 10 are provided.

  The control unit 15 controls the operation of the laser diode 8 and the polygon mirror 2 for the initialization operation and image formation of the semiconductor laser, and is a read-only storage that stores the rotational speed value of the polygon mirror 2 and a control program. ROM (Read Only Memory) 16, RAM (Random Access Memory) 17, CPU (Central Processing Unit) 18 that executes a control program, and writing that is a dedicated IC that controls writing by laser light It is composed of a control ASIC (Application Specific Integrated Circuit) 19. With such a configuration, the CPU 18 operates while using the work area of the RAM 17 based on the program stored in the ROM 16, whereby the write control ASIC 19 controls the operations of the LD driver 9 and the polygon motor driver 11.

Here, an initialization operation (current value determining means) controlled by the write control ASIC 19 and executed by the LD driver 9 will be described. In the initialization operation, the LD driver 9 determines the bias current value (I _b ) and the current at which the laser diode 8 starts to emit light (threshold current) from the relationship between the amount of current supplied to the laser diode 8 and the amount of light of the laser diode 8 at that time. : I _th ). The bias current is a current value obtained by subtracting a predetermined current value (I _sub ) from the threshold current I _th , so that light can be emitted immediately when a light emission command is received (the response of the laser diode 8 is improved). This is the current that is set to the last value at which the laser diode 8 does not emit light and is kept in standby. Initializing operation by the LD driver 9 detects the bias current value I _b and the threshold current I _th based on the amount of current supplied to the laser diode 8 and the amount at that time.

It will be described in detail with reference to the graph of FIG. 4 the initialization operation for detecting a bias current I _b and the threshold current I _th based on the amount of current supplied to the laser diode 8 and the amount at that time.

As shown in FIG. 4, first, the laser diode 8 is turned on with two-stage current values I _A and I _B , respectively. The photodiode 25 detects the laser light quantity when the laser diode 8 is turned on as L _A and L _B , respectively. The two-stage current values I _A and I _B are determined at the design stage. However, if the amount of light irradiated onto the photosensitive drum 5 is too high, light fatigue of the photosensitive drum 5 may occur. As a result, the replacement life of the photosensitive drum 5 is shortened. In addition, if the amount of light is too low, there is a concern that the accuracy of current value calculation may be reduced. Therefore, it is necessary to determine the current values I _A and I _B while taking into consideration the light fatigue of the photosensitive drum 5 and the current value calculation accuracy. Figure 4 on the graph, A point _{(I A, L A),} B point (I _B, L _B) from the two points, the straight line C is obtained by the equation (1).

In Equation 1, the bias current value I _b when the light amount becomes 0 is calculated. Therefore, the current value I _b can be obtained from the formula 2 by substituting (I _b , 0) into the formula 1 and modifying it.

The bias current I _b is a limit to oscillate the laser diode 8, the laser diode 8 is turned on at the stage beyond the bias current I _b. Therefore, in the off state of the laser diode 8 in advance by supplying a bias current I _b from the LD driver 9 switches the threshold current I _th by directing the light. By such current control, the lighting response of the laser diode 8 can be operated under the shortest condition.

Next, a threshold current I _th for obtaining the light amount L _th to which the photosensitive drum 5 reacts is calculated. The threshold current I _th is a value for generating an optimum light amount when forming an image on the photosensitive drum 5. If the light amount is too high, light fatigue of the photosensitive drum 5 occurs, and the photosensitive drum. Thus, the replacement life of 5 is shortened. On the other hand, if the amount of light is too low, the contrast between the image area and the non-image area on the electrostatic latent image cannot be obtained, which adversely affects image formation. Therefore, the optimum value of the threshold current I _th is determined by the initialization operation after the print start command of each image forming apparatus is issued. The threshold current I _th can be obtained from Equation 3 by substituting (I _th , L _th ) into Equation 1 for deformation.

The light amount L _th is the photosensitivity of the photosensitive drum 5, the output light amount of the laser diode 8, the reflectance of the polygon mirror 2 and the reflection mirror 4 in the laser light path, the transmittance of the f-θ lens 3, and the laser light. The optimum value is determined at the design stage in consideration of individual differences in the components such as the photosensitivity of the photodiode 25 to be detected. As described above, the initialization operation is a step of determining an optimum current value for operating the laser diode 8 by supplying a predetermined current to the laser diode 8 and detecting the amount of output light. This is indispensable for the drive of 8.

However, in the semiconductor laser exposure apparatus 201, the laser light from the laser diode 8 is reflected by the polygon mirror 2 and is irradiated to the photosensitive drum 5 through the f-θ lens 3 and the reflection mirror 4. In this case, when the laser light is reflected by the polygon mirror 2 under the optical conditions of regular reflection (incident angle 90 degrees), the reflected light returns directly to the inside of the LD unit 1 and is detected by the photodiode 25. Become. This phenomenon is called return light. If return light enters during the initialization operation described above, it is determined that the light is emitted more than the original light amount (A_error in FIG. 4), and the bias current value I _b and threshold current I _th may be detected incorrectly. If the erroneously detected bias current value I _b _error is passed, more current flows than the normal bias current I _b , and the photosensitive drum 5 always reacts, resulting in a background stain image.

To solve this problem, by initiating the initializing operation immediately after the return light, the return light during the detection of the bias current value I _b and the threshold current I _th is to reduce the possibility of incoming It is considered. FIG. 5 is a timing chart showing the relationship between the return light timing and the time required for current detection in the conventional initialization operation. As shown in FIG. 5, if the execution time of the initialization operation described above is shorter than the laser light scanning time for one line in which return light is generated, the possibility of return light entering the current detection period is low. This means that the initialization operation is performed.

  However, with the recent increase in the speed of image forming apparatuses, the time required for one scanning period for regular reflection conditions has been significantly shortened by means such as increasing the number of polygon mirrors 2 and increasing the rotational speed. As a result, as shown in FIG. 6, if the scanning time of one line is shortened, return light is generated during the initialization operation, and in addition to the light emission of the laser diode 8, the return light is also detected by the photodiode 25. There is a problem that the lighting current of 8 cannot be properly obtained.

  Therefore, in the present embodiment, the rotational speed of the polygon motor 10 is determined such that the scanning time for one line is longer than the execution time of the initialization operation at the design stage, and is determined only during the initialization operation. The rotation of the polygon motor 10 is controlled by the rotation speed. Here, scanning time extending means is realized.

  Here, FIG. 7 is a flowchart showing the flow of initialization operation processing by the write control ASIC 19. As shown in FIG. 7, first, when a copy request is sent from the operation / display unit 21 or a print request is sent from the network I / F 24, the write control ASIC 19 receives a print operation start command (step S100). The writing control ASIC 19 transmits a control signal to the polygon motor driver 11 so that the polygon motor 10 performs an initialization operation (step S101). The polygon motor driver 11 that has received the control signal for the initialization operation initializes the rotation speed of the polygon motor 10 according to the rotation speed value stored in the ROM 16 (the rotation speed of the polygon motor 10 during the initialization operation). Set the speed to That is, the rotational speed value (the rotational speed of the polygon motor 10 during the initialization operation) stored in the ROM 16 is such that the scanning time for one line is longer than the execution time of the initialization operation. .

  Regarding the setting of the rotation speed of the polygon motor 10, by inputting a control signal to the polygon motor driver 11, a rotation signal for setting the rotation speed is transmitted to the polygon motor 10, and the polygon is rotated at a desired rotation speed according to the control signal. The mirror 2 is rotated. Therefore, the rotation speed of the polygon mirror 2 suitable for the initialization operation is determined by the number of faces of the polygon mirror 2 that affects the scanning time of one line, the scanning distance of one line, and the CPU processing that affects the execution time of the initialization operation. Since it varies depending on conditions such as speed, ROM and RAM sizes, program size, etc., these conditions should be taken into consideration in the design stage.

  Next, after confirming that the rotation speed of the polygon motor 10 is set to the rotation speed of the initialization operation (Yes in step S102), the laser diode 8 is set to have a light quantity during the initialization operation (less than the light quantity of the laser diode 8 during image formation). The setting operation is instructed to start the initialization operation (step S103). Thus, by making the light quantity of the laser diode 8 when determining each current value smaller than the light quantity of the laser diode 8 at the time of image formation, generation of light fatigue in the photosensitive drum 5 irradiated with the laser light is prevented. It can be reduced to a minimum. Here, a light amount adjusting means is realized.

  When the initialization operation is executed and it is confirmed that the process has been completed (Yes in step S104), the polygon motor driver 11 stores the polygon according to the rotational speed value stored in the ROM 16 (the rotational speed of the polygon motor 10 during image formation). A control signal is transmitted so that the motor 10 performs a rotating operation during image formation (step S105).

  After confirming that the polygon motor 10 has been set to the rotation speed at the time of image formation (Yes in step S106), the laser diode 8 is set to the light amount at the time of image formation, and then a control signal for starting image formation is transmitted ( Step S107).

  As described above, according to the present embodiment, during the execution of the initialization operation for determining the optimum current value for turning on the laser diode 8, the scanning time of one line is longer than the execution time of the current value determination process. By making the length longer, an appropriate current value is determined for turning on the laser diode 8 even if the time of one scanning period that becomes a specular reflection condition is significantly shortened by speeding up the image forming apparatus. The initialization operation can be executed properly.

[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIGS. The same parts as those in the first embodiment described above are denoted by the same reference numerals, and description thereof is also omitted.

  FIG. 8 is a schematic diagram schematically showing the configuration of the semiconductor laser exposure apparatus 201 of the image forming apparatus according to the second embodiment of the present invention. As shown in FIG. 8, the semiconductor laser exposure apparatus 201 of the present embodiment is provided with a laser light blocking mechanism 12A. The laser beam blocking mechanism 12A functions to block the laser beam emitted from the laser diode 8 from being irradiated on the photosensitive drum 5 after being reflected by the polygon mirror 2.

  Although the laser light blocking mechanism 12A is installed between the reflection mirror 4 and the photosensitive drum 5 as an example, the laser light is reflected by the polygon mirror 2 and then irradiated to the photosensitive drum 5. It may be placed anywhere in the laser beam path, and the position of the technology does not depend on the position. Although not specifically illustrated, the laser light blocking mechanism 12A is assumed to be a mechanical shutter, but its configuration is not particularly limited, and the availability of the technology does not depend on it.

  FIG. 9 is a block diagram illustrating a reading control system of the image forming apparatus. As shown in FIG. 9, the semiconductor laser exposure apparatus 201 of the image forming apparatus drives a laser beam blocking mechanism 12A, a blocking mechanism control motor 13A, and a blocking mechanism control motor 13A in addition to the configuration in the first embodiment. A shut-off mechanism control motor driver 14A, which is a circuit, is provided. The control unit 15 has the same configuration as that of the first embodiment, but the write control ASIC 19 includes a cutoff mechanism control motor in addition to the LD driver 9 and the polygon motor driver 11 described in the first embodiment. The operation of the driver 14A is also controlled. The interruption mechanism control motor driver 14A, to which the control signal is transmitted from the writing control ASIC 19, controls the interruption mechanism control motor 13 to instruct the laser light interruption mechanism 12A to cut off or open the laser light path.

  Here, FIG. 10 is a flowchart showing the flow of initialization operation processing by the write control ASIC 19. As shown in FIG. 10, first, when a copy request is sent from the operation / display unit 21 or a print request is sent from the network I / F 24, the write control ASIC 19 receives a print operation start command (step S200). The writing control ASIC 19 transmits a control signal to the blocking mechanism control motor driver 14 so that the laser beam blocking mechanism 12A blocks the laser beam path (step S201). The cutoff mechanism control motor driver 14A to which the laser beam cutoff control signal is transmitted drives the cutoff mechanism control motor 13A so that the laser beam cutoff mechanism 12A blocks the laser beam path. Here, the first optical path blocking means is realized.

  Thereafter, after confirming that the laser beam blocking mechanism 12A has blocked the laser beam path (Yes in step S202), a control signal is transmitted to the polygon motor driver 11 so that the polygon motor 10 performs an initialization operation (step S203). . The polygon motor driver 11 that has received the control signal for the initialization operation initializes the rotation speed of the polygon motor 10 according to the rotation speed value stored in the ROM 16 (the rotation speed of the polygon motor 10 during the initialization operation). Set the speed to That is, the rotational speed value (the rotational speed of the polygon motor 10 during the initialization operation) stored in the ROM 16 is such that the scanning time for one line is longer than the execution time of the initialization operation. .

  Regarding the setting of the rotation speed of the polygon motor 10, by inputting a control signal to the polygon motor driver 11, a rotation signal for setting the rotation speed is transmitted to the polygon motor 10, and the polygon is rotated at a desired rotation speed according to the control signal. The mirror 2 is rotated. Therefore, the rotation speed of the polygon mirror 2 suitable for the initialization operation is determined by the number of faces of the polygon mirror 2 that affects the scanning time of one line, the scanning distance of one line, and the CPU processing that affects the execution time of the initialization operation. Since it varies depending on conditions such as speed, ROM and RAM sizes, program size, etc., these conditions should be taken into consideration in the design stage.

  Next, after confirming that the rotation speed of the polygon motor 10 is set to the rotation speed of the initialization operation (Yes in step S204), the laser diode 8 is set to have a light quantity during the initialization operation (less than the light quantity of the laser diode 8 during image formation). A small amount of light is set to instruct the start of the initialization operation (step S205). An initialization operation is executed, and it is confirmed that the operation has been completed (step S206). After completing the initialization operation, the polygon motor driver 11 is caused to rotate at the rotational speed at the time of image formation according to the rotational speed value (the rotational speed of the polygon motor 10 at the time of image formation) stored in the ROM 16. A control signal is transmitted to (step S207).

  After confirming that the polygon motor 10 has been set to the rotation speed at the time of image formation (Yes in step S208), a control signal is transmitted to the cutoff mechanism control motor driver 14A so that the laser beam cutoff mechanism 12A opens the laser beam path. (Step S209). The shut-off mechanism control motor driver 14A, to which the laser light path opening control signal is transmitted, drives the shut-off mechanism control motor 13A so that the laser light shut-off mechanism 12A opens the laser light path. After confirming that the laser beam blocking mechanism 12A has opened the laser beam path (Yes in step S210), the laser diode 8 is set to a light amount for image formation and a control signal for starting image formation is transmitted (step S211).

  As described above, according to the present embodiment, during the execution of the initialization operation for determining the optimum current value for turning on the laser diode 8, the rotation speed of the polygon motor 10 is reduced and the laser light blocking mechanism 12A is used. By operating, it is possible to prevent erroneous detection of the amount of light due to specularly reflected light (90-degree incident light) of the polygon mirror 2 and to prevent light fatigue from occurring on the photosensitive drum 5 irradiated with laser light.

  In this embodiment, the blocking mechanism control motor 13A is driven to move the laser beam blocking mechanism 12A. However, the present invention is not limited to this, and the laser beam blocking mechanism 12A is moved using a solenoid or the like. You may make it let it.

  In this embodiment, in step S205, the laser diode 8 is set to a light amount at the time of the initialization operation (a light amount smaller than the light amount of the laser diode 8 at the time of image formation) to instruct the start of the initialization operation. However, it is not limited to this. When the laser light blocking mechanism 12A is used, the photoconductor drum 5 does not cause light fatigue due to the laser light, so it is not always necessary to set the light amount at the time of initialization. In step S205, the light amount at the time of image formation is set. It may be set to instruct the start of the initialization operation.

[Third Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIGS. The same parts as those in the first embodiment described above are denoted by the same reference numerals, and description thereof is also omitted.

  FIG. 11 is a schematic diagram schematically showing a configuration of a semiconductor laser exposure apparatus 201 of the image forming apparatus according to the third embodiment of the present invention. As shown in FIG. 11, in the semiconductor laser exposure apparatus 201 of the present embodiment, a laser light blocking mechanism 12 </ b> B is provided between the laser diode 8 and the polygon mirror 2. That is, the laser light blocking mechanism 12B is disposed on the optical path until the laser light emitted from the laser diode 8 is reflected by the polygon mirror 2.

  FIG. 12 is a block diagram illustrating a reading control system of the image forming apparatus. As shown in FIG. 12, the semiconductor laser exposure apparatus 201 of the image forming apparatus drives a laser light blocking mechanism 12B, a blocking mechanism control motor 13B, and a blocking mechanism control motor 13B in addition to the configuration in the first embodiment. A shut-off mechanism control motor driver 14B, which is a circuit, is provided. The control unit 15 has the same configuration as that of the first embodiment, but the write control ASIC 19 includes a cutoff mechanism control motor in addition to the LD driver 9 and the polygon motor driver 11 described in the first embodiment. The operation of the driver 14B is also controlled. The shut-off mechanism control motor driver 14B that has received the control signal from the write control ASIC 19 controls the shut-off mechanism control motor 13B to instruct the laser light shut-off mechanism 12B to shut off or open the laser light path.

  Here, FIG. 13 is a flowchart showing the flow of initialization operation processing by the write control ASIC 19. As shown in FIG. 13, first, when a copy request is sent from the operation / display unit 21 or a print request is sent from the network I / F 24, the write control ASIC 19 receives a print operation start command (step S300). The write control ASIC 19 transmits a control signal to the blocking mechanism control motor driver 14B so that the laser beam blocking mechanism 12B blocks the laser beam path (step S301). The cutoff mechanism control motor driver 14B, to which the laser beam cutoff control signal is transmitted, drives the cutoff mechanism control motor 13B so that the laser beam cutoff mechanism 12B blocks the laser beam path. Here, the second optical path blocking means is realized.

  Thereafter, after confirming that the laser beam blocking mechanism 12B has blocked the laser beam path (Yes in step S302), the laser diode 8 has a light amount during the initialization operation (a light amount smaller than the light amount of the laser diode 8 during image formation). Setting is instructed to start the initialization operation (step S303).

  After executing the initialization operation and confirming that it has been completed (Yes in step S304), the rotation speed set by the polygon motor 10 (for example, the speed at initialization (the scanning time of one line is more suitable for the initialization operation). (Rotation speed that is longer than the execution time)) (Yes in step S305), a control signal is sent to the cutoff mechanism control motor driver 14B so that the laser beam cutoff mechanism 12B opens the laser beam path. Transmit (step S306).

  The cutoff mechanism control motor driver 14B, which has received the laser light path opening control signal, drives the cutoff mechanism control motor 13B so that the laser light cutoff mechanism 12B opens the laser optical path. After confirming that the laser beam blocking mechanism 12B has opened the laser beam path (Yes in step S307), the laser diode 8 is set to the light amount for image formation and image formation is started (step S308).

  As described above, according to the present embodiment, during the execution of the initialization operation for determining the optimum current value for turning on the laser diode 8, the laser light is arranged in the optical path until it is reflected by the polygon mirror 2. Since the light from the laser diode 8 does not reach the polygon mirror 2 by operating the laser light blocking mechanism 12B, the return light disappears. Therefore, the light quantity error caused by the regular reflection light (90-degree incident light) of the polygon mirror 2 is eliminated. Detection can be prevented in advance.

  In this embodiment, the blocking mechanism control motor 13B is driven to move the laser beam blocking mechanism 12B. However, the present invention is not limited to this, and the laser beam blocking mechanism 12B is moved using a solenoid or the like. You may make it let it.

  Further, in the present embodiment, in step S303, the laser diode 8 is set to a light amount during the initialization operation (a light amount smaller than the light amount of the laser diode 8 during image formation) to instruct the start of the initialization operation. However, it is not limited to this. When the laser light blocking mechanism 12B is used, the photoconductive drum 5 does not cause light fatigue due to the laser light, and therefore it is not always necessary to set the light amount at the time of initialization. In step S303, the light amount at the time of image formation is set. It may be set to instruct the start of the initialization operation.

  Further, in the present embodiment, the number of rotations set by the polygon motor 10 (for example, speed at initialization (rotation speed at which the scanning time of one line is longer than the execution time of the initialization operation)). When it has been confirmed that (Yes in step S305), the control signal is transmitted to the blocking mechanism control motor driver 14B so that the laser beam blocking mechanism 12B opens the laser beam path (step S306). However, it is not limited to this. When the laser light blocking mechanism 12B is provided between the laser diode 8 and the polygon mirror 2, the laser light is not reflected by the polygon mirror 2, so that no return light is generated, and one line scanning time. It is not always necessary to set the polygon motor 10 to the speed at the time of initialization, and when it is confirmed in Step S305 that the rotation speed at the time of image formation has been reached (Yes in Step S305), the laser is not required. A control signal may be transmitted to the blocking mechanism control motor driver 14B so that the light blocking mechanism 12B opens the laser beam path (step S306).

1 is a longitudinal front view showing an internal structure of an image forming apparatus according to a first embodiment of the present invention. It is a schematic diagram which shows schematically the structure of a semiconductor laser exposure apparatus. 2 is a block diagram illustrating a reading control system of the image forming apparatus. FIG. It is a graph which shows the electric current detection result by the initialization operation | movement which LD driver performs. It is a timing chart which shows the relationship between the timing of the return light in the conventional initialization operation | movement, and the time required for electric current detection. It is a timing chart which shows the relationship between the timing of the return light in the conventional initialization operation | movement, and the time required for electric current detection. It is a flowchart which shows the flow of the initialization operation | movement process by write control ASIC. It is a schematic diagram which shows schematically the structure of the semiconductor laser exposure apparatus of the image forming apparatus concerning the 2nd Embodiment of this invention. 2 is a block diagram illustrating a reading control system of the image forming apparatus. FIG. It is a flowchart which shows the flow of the initialization operation | movement process by write control ASIC. It is a schematic diagram which shows schematically the structure of the semiconductor laser exposure apparatus of the image forming apparatus concerning the 3rd Embodiment of this invention. 2 is a block diagram illustrating a reading control system of the image forming apparatus. FIG. It is a flowchart which shows the flow of the initialization operation | movement process by write control ASIC.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Deflection means 5 Photoconductor 8 Laser 201 Optical writing apparatus 202 Charging apparatus 203 Developing apparatus 208 Transfer apparatus 210 Fixing apparatus

Claims (5)

An optical writing device for forming a latent image on a photosensitive member by deflecting and scanning laser light emitted from a laser by a deflecting unit,
Current value determining means for determining a threshold current value at which the laser starts to emit light and a bias current value that enables the laser to emit light immediately after a light emission command is received;
When determining each current value by the current value determining means, the rotational speed of the deflecting means is set so that the scanning time of one line by the deflecting means is longer than the execution time of the current value determining process. Scanning time extension means for setting slower than the rotation speed of the deflection means at the time of formation;
An optical writing device comprising: A light amount adjusting unit configured to reduce the light amount of the laser when the current value determining unit determines the current values to be smaller than the light amount of the laser during image formation;
The optical writing device according to claim 1. During execution of the current value determining means, a first optical path blocking means for blocking an optical path from the deflecting means to the photoconductor is provided.
The optical writing device according to claim 1. During the execution of the current value determining means, a second optical path blocking means for blocking an optical path from the laser to the deflection means is provided.
The optical writing device according to claim 1. A photoreceptor,
A charging device for uniformly charging the surface of the photoreceptor;
The optical writing device according to claim 1, wherein the photosensitive member after uniform charging is exposed to form an electrostatic latent image;
A developing device for developing the electrostatic latent image formed on the photoreceptor;
A transfer device for transferring a developed image from the photoreceptor to a recording medium;
A fixing device for fixing the developed image transferred to the recording medium;
An image forming apparatus comprising:

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