JP5707759B2 - Light quantity control device, optical scanning device, and image forming apparatus - Google Patents

Description

  The present invention relates to a light amount control device, an optical scanning device, and an image forming apparatus.

  Patent Document 1 discloses a light detection unit that detects the light amounts of a plurality of light beams, and a plurality of light beams of the plurality of light beams so that the light amount becomes a predetermined target light amount based on the light amounts detected by the light detection unit. A light amount control means for controlling each light quantity, and at the time of light quantity control by the light quantity control means, the light quantity of the plurality of light beams converges to the target light quantity depending on whether the number of the plurality of light beams is 2n or odd number Thus, there is described a light amount control device including lighting control means for controlling lighting of the plurality of light beams.

  Patent Document 2 discloses a total light amount detecting means for detecting the total light amount of a plurality of light beams output simultaneously from a light source that has a plurality of light emitting elements and generates a plurality of light beams, and a light emitting element of the light source. A light intensity balance unit that preliminarily adjusts a variation in emission intensity for each light source, and a plurality of light emitting elements of the light source that have been adjusted for variation in emission intensity by the light intensity balance unit are simultaneously turned on, A light emission intensity control apparatus comprising: a control unit that detects a total light emission amount by the total light amount detection unit and adjusts a total light emission amount of the light emitting elements of the light source based on a detection value of the total light amount detection unit. The control means compares the detection value of the total light quantity detected by the total light quantity detection means with a reference value, and determines the light intensity of the light emitting element of the light source based on the comparison result of the comparison means. It has a light intensity setting means for constant, wherein the light intensity setting means, the emission intensity control apparatus characterized by independently setting the light intensity of each light-emitting element is described.

JP 2006-140421 A

Japanese Patent No. 3503301

  The present invention uses a reference voltage obtained by performing light amount control on the reference light emitting element, and shortens the light amount control time as compared with the case where the light amount control of other light emitting elements is not performed, and the accuracy of controlling the light amount is improved. An object of the present invention is to provide an improved light quantity control device, optical scanning device, and image forming apparatus.

To achieve the above object, the light quantity control device according to claim 1, and detecting means for detecting the originating light intensity of the light emitting element, in the initial light amount control process, based on the light emission amount detected by said detection means, emission amount of the reference light-emitting element of the multiple light-emitting elements, a voltage applied to the reference light-emitting element such that the predetermined amount of light emission, light emission voltage and the reference light-emitting element corresponding to the reference current And a first control unit that controls the reference light emitting element when the light emission amount of the reference light emitting element becomes the predetermined light emission amount by the control of the first control unit. first storage means for storing the applied voltage as the reference voltage, the plurality the light emitting amount of the reference light-emitting element when the reference voltage is applied to the front SL by applying the reference voltage stored in the first storage unit to emit each light emitting element A second storage means for storing for each light emission element a first voltage corresponding to the difference or ratio between the light emission amount of each light-emitting element when, during the processing image forming driving, the reference current of the plurality of light emitting elements and a voltage corresponding to the value obtained by dividing by the number and the value obtained by dividing the number of first voltage the plurality of light emitting elements, each is applied the addition to the reference voltage generated for each of the plurality of light emitting elements said a plurality of light emitting elements were simultaneously emitted, the value of the current corresponding to the detected light intensity divided by the number of the plurality of light emitting elements by the detection means, said current corresponding to the first voltage the plurality of light emitting elements and a value obtained by dividing the number of, adding to the calculated light receiving current for each of the plurality of light emitting elements, light emission amount of each pre-Symbol plurality of light emitting elements such that the voltage corresponding to the photocurrent becomes the reference voltage a second control means for simultaneously controlling the voltage corresponding to the photocurrent is the ginseng By multiplying the voltage applied to each of the plurality of light emitting elements when was the voltage by the number of the plurality of light emitting elements, and a generating means for generating a driving voltage of each of the plurality of light emitting elements.

The light quantity control device according to claim 2 is the light quantity control device according to claim 1, wherein the second control means sets the light emission amount for each of the plurality of light emitting elements for each line based on image data. Control is performed for each light emitting element, and for the second and subsequent lines, the voltage applied to each light emitting element when the voltage corresponding to the light receiving current becomes the reference voltage by the control of the first line is used as the reference voltage. voltage controls the light emission amount for each previous SL plurality of light emitting elements so that the reference voltage corresponding to.

  According to a third aspect of the present invention, there is provided an optical scanning device comprising: a plurality of light emitting elements; and a light amount control device according to the first or second aspect that controls light emission amounts of the plurality of light emitting elements.

  According to a fourth aspect of the present invention, there is provided an image forming apparatus according to the third aspect, and a photoconductor exposed by a beam emitted from a plurality of light emitting elements provided in the optical scanning apparatus based on image data. .

The light quantity control device according to claim 5, a detecting means for detecting the light emission amount of a plurality of light emitting elements, in the initial light amount control process, based on the light emission amount detected in the previous SL detecting means, said plurality of light emitting elements First control means for controlling the light emission amount when light is emitted by applying a voltage to the reference light emitting element, and the reference light emission by the control of the first control means. First storage means for storing, as a reference voltage, a voltage applied to the reference light emitting element when the light emission amount of the element becomes the predetermined light emission amount, the light emission amount of the reference light emitting element, and the reference light emitting element A light emitting element other than the reference light emitting element has a first voltage corresponding to a difference or a ratio with a light emission amount of the light emitting element when light is emitted by applying the reference voltage stored in the first storage unit to a light emitting element other than a second storage means for storing for each, During processing the imaging drive, the light emission amount of the reference light-emitting element to emit light by applying a voltage includes a second control means for controlling so that said predetermined amount of light emission, and the reference voltage, the first It calculates a correction value voltage according to the voltage and the difference or ratio of the light emission amount of the reference light-emitting element to emit light is applied in the said predetermined amount of light emission by control of second control means, the correction value voltage / Correction voltage generation means for generating a correction voltage corrected by calculating the reference voltage × the first voltage + the first voltage for each of the plurality of light emitting elements, and light emission by the control of the second control means Drive voltage generating means for generating, as the drive voltage for each of the plurality of light emitting elements, a drive voltage obtained by correcting the voltage applied when the light emission amount of the reference light emitting element becomes the predetermined light emission amount with the correction voltage; Prepare.

  An optical scanning device according to a sixth aspect includes a plurality of light emitting elements and a light amount control device according to the fifth aspect that controls light emission amounts of the plurality of light emitting elements.

  According to a seventh aspect of the present invention, there is provided an image forming apparatus according to the sixth aspect, and a photoconductor exposed by a beam emitted from a plurality of light emitting elements provided in the optical scanning apparatus based on image data. .

According to the first, second, third, fourth, fifth, sixth, and seventh aspects of the present invention, the reference voltage obtained by performing the light amount control on the reference light emitting element is used. Thus, the light amount control time is shortened and the accuracy of controlling the light amount is improved as compared with the case where the light amount control of other light emitting elements is not performed.

It is a top view which shows schematic structure of an example of the optical scanning device concerning 1st Embodiment. It is the schematic which shows the structure of an example of the laser array of the optical scanning device shown in FIG. 1 is a functional block diagram illustrating a schematic configuration of an example of an image forming apparatus according to a first embodiment. FIG. 3 is a circuit diagram of a specific example of a drive circuit unit according to the first embodiment. It is a flowchart of an example of the flow of the light quantity control process in the light quantity control apparatus which concerns on 1st Embodiment. It is an example of the timing chart of the light quantity control process which concerns on 1st Embodiment. It is a flowchart of an example of the flow of initial APC which concerns on 1st Embodiment. FIG. 5 is a circuit diagram showing a current flow in light amount feedback control of a reference light emitting element in initial APC according to the first embodiment. It is explanatory drawing for demonstrating the relationship between the voltage conversion value of the light reception current of MPD in the case of performing the feedback control which concerns on 1st Embodiment, and time. FIG. 6 is a circuit diagram showing a current flow when holding a voltage including a variation in light emission amount of each light emitting element in the initial APC according to the first embodiment. It is explanatory drawing for demonstrating the specific example of the light-emission quantity of the light emitting element CH at the time of performing forced lighting which concerns on 1st Embodiment. 4 is a flowchart of an example of a flow of processing at the time of image formation driving according to the first embodiment. It is explanatory drawing for demonstrating the light emission amount for each light emitting element CH in RUN-APC which concerns on 1st Embodiment. It is a circuit diagram showing a current flow in RUN-APC on the first line according to the first embodiment. It is explanatory drawing for demonstrating the relationship between the light reception light quantity in the case of RUN-APC which concerns on 1st Embodiment, and the light reception light quantity at the time of a modulation | alteration. FIG. 3 is a circuit diagram illustrating a current flow in a modulation process according to the first embodiment. FIG. 3 is a circuit diagram of a specific example of a drive potential generation block according to the first embodiment. It is the circuit diagram which showed the flow of the electric current in RUN-APC other than the 1st line which concerns on 1st Embodiment. It is a functional block diagram showing a schematic configuration of an example of an image forming apparatus according to a second embodiment. It is a functional block diagram which shows schematic structure of an example of the module which concerns on 2nd Embodiment. It is a circuit diagram of a specific example of a feedback control unit according to the second embodiment. It is explanatory drawing for demonstrating the specific example of the light-emission quantity of the light emitting element which concerns on 2nd Embodiment. 10 is a flowchart of an example of a flow of processing at the time of image formation driving according to the second embodiment.

  [First Embodiment]

  Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings. Here, as a specific example, an optical scanning device that scans and exposes a photosensitive member with laser beams emitted from a plurality of light emitting elements (hereinafter simply referred to as “beams”), and the light quantity of the light emitting elements is represented by APC (Auto A description will be given of a case where the present invention is applied to a light amount control device that performs power control (automatic light amount control) and an image forming apparatus in which the photosensitive member is scanned and exposed by the optical scanning device.

  First, the optical scanning device according to the present embodiment will be described. FIG. 1 is a plan view showing a schematic configuration of an example of an optical scanning device according to the present embodiment. As shown in FIG. 1, the optical scanning device 10 includes a surface emitting laser array 12 that emits a plurality of beams by a plurality (N) of light emitting elements, and a polygon that scans the plurality of beams in the main scanning direction. And a mirror 24. The laser array 12 is attached to the circuit board 14. Although the laser array 12 generates a plurality of beams, FIG. 1 shows only one beam for simplification.

In the laser array 12, as shown in FIG. 2, a plurality (N) of light emitting elements (CH) such as laser diodes are two-dimensionally arranged. Hereinafter, these CHs are referred to as CH0 to CHn-1, and beams emitted from each of these CHs are referred to as a 0th beam to an n-1th beam. In addition, when distinguishing each light emitting element, it demonstrates by attaching | subjecting the number which identifies each light emitting element after code | symbol CH, and when naming generically without distinguishing each, each light emitting element is identified. The description of numbers is omitted. Similarly, other components provided for the light emitting elements (for example, a module 48 in FIG. 3 to be described later) are also collectively referred to, and the description of the numbers for identifying the individual light emitting elements is omitted.

The beam emitted from the laser array 12 is converted into substantially parallel light by the collimator lens 16. The half mirror 18 separates a part of the beam and guides it to a monitor photodiode (MPD) 20 which is an element for detecting the amount of received light. Unlike the edge emitting laser, the laser array 12 cannot emit a beam (back beam) from the rear side of the resonator. Therefore, in order to obtain a monitor signal for light quantity control, a part of the beam emitted from the laser array 12 is separated by the half mirror 18 and then guided to the MPD 20 as described above.

On the other hand, the beam that has passed through the half mirror 18 is imaged into a long line in the main scanning direction in the vicinity of the reflecting surface of the polygon mirror 24 by the cylindrical lens 22 having power only in the sub-scanning direction, and is incident on the polygon mirror 24. .

The polygon mirror 24 is rotated by a motor (not shown) to deflect and reflect the incident beam in the main scanning direction. Then, the beam deflected and reflected by the polygon mirror 24 is imaged on the photosensitive member 6 (see FIG. 3) in the main scanning direction by the fθ lens 26 having power only in the main scanning direction, and on the photosensitive member 6. An image is formed so as to move at a substantially constant speed.

The beam that has passed through the fθ lens 26 is imaged on the photoconductor 6 by a cylindrical mirror 28 having power only in the sub-scanning direction, and an electrostatic latent image corresponding to the image signal of the corresponding color is formed on the photoconductor 6. Is done.

Further, since the optical scanning device 10 needs to synchronize the scanning start on each reflecting surface of the polygon mirror 24, the pickup mirror 30 that reflects the beam before the scanning start and the beam reflected by the pickup mirror 30 are reflected. And a main scanning synchronization sensor 32 to detect, and the main scanning synchronization signal output from the main scanning synchronization sensor 32 synchronizes the writing timing in the main scanning direction.

  Next, an image forming apparatus including the optical scanning device 10 of the present embodiment and a light amount control device that controls the light amount of the light emitting element CH of the optical scanning device 10 will be described.

  FIG. 3 is a functional block diagram showing a schematic configuration of an example of the image forming apparatus 1 according to the present embodiment. The image forming apparatus 1 according to the present embodiment includes an image forming control unit 2 and an image forming unit 4 that forms an image based on image data signals output from the image forming control unit 2 and various control signals. ing.

  The image forming unit 4 includes an optical scanning device 10 and a photoconductor 6 that is scanned and exposed by the optical scanning device 10.

  The optical scanning device 10 according to the present embodiment includes a light amount control device 40 and N light emitting elements CH whose light emission amounts are controlled by the light amount control device 40.

  The light quantity control device 40 of this embodiment includes a control unit 42, a drive circuit unit 44, and an MPD. The control unit 42 has a function of controlling the entire light amount control device 40, and includes a memory including a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory), and an HDD (Hard Disk Drive). And a non-volatile storage unit such as a flash memory. The control unit 42 outputs an image data signal, a main scanning synchronization signal, a control signal, and the like to the drive circuit unit 44, and controls on / off of a switching element SW (detailed later) provided in the drive circuit unit 44. Has the function to perform.

The drive circuit unit 44 includes one common module 46 provided in common for all (N in the present embodiment) light emitting elements CH, and a module 48 (48 _{0 to} 48 provided for each light emitting element CH. _n-1 ).

  FIG. 4 shows a circuit diagram of a specific example of the drive circuit unit 44 of the present embodiment. The drive circuit unit 44 includes a reference power supply 50, a Vref × 1 / N reference current generation block 52, an MPD light reception current × 1 / N generation block 54, a 1 / N initial APC differential current calculation block 56, and a 1 / N RUN-APC. Differential current calculation block 58, RUN-APC reference current generation block 60, RUN-APC light reception current generation block 62, drive potential generation block 64, APC-AMP 66, operational amplifiers 68, 70, 72, potential storage units 74, 76, 78 79, switching elements SW1 to 15 and the like.

  The reference power supply 50 provided in the common module 46 has a function of supplying a reference light amount (current corresponding to the reference light amount, which corresponds to the MPD light receiving current of the reference light amount in this embodiment) serving as a reference current Vref. is there. The Vref × 1 / N reference current generation block 52 has a function of generating a 1 / N current of the reference light amount Vref as a reference current. The MPD light reception current × 1 / N generation block 54 has a function of generating a current 1 / N of the MPD light reception current.

  The differential current calculation block 56 for 1 / N initial APC provided in the module 48 is a difference between the voltage Vpd of the MPD received light amount and the light emitting amount (target light amount) of the reference light emitting element CH0 in the initial APC (detailed later). 1 / N has a function of calculating a differential current for initial APC. The 1 / N RUN-APC differential current calculation block 58 has a function of generating a RUN-APC differential current. The RUN-APC reference current generation block 60 generates a RUN-APC based on the current generated by the Vref × 1 / N reference current generation block 52 and the current calculated by the 1 / N initial APC differential current calculation block 56. It has a function of generating a reference current for the hour. The RUN-APC light reception current generation block 62 is based on the MPD light reception current × 1 / N generation block 54 and the current calculated by the 1 / N RUN-APC differential current calculation block 58. It has a function of generating a light receiving current at the time. The drive potential generation block 64 has a function of generating a drive potential of the light emitting element CH based on the potential stored in the potential storage unit 78.

  The APC-AMP 66 has a function of performing feedback control so that the reference current and the light-receiving current from the MPD match during APC, and uses a so-called operational amplifier.

  Each of the potential storage units 74, 76, 78, and 79 has a function of storing a potential. In this embodiment, sample hold capacitors (hereinafter simply referred to as capacitors) C1 to C4 are used as a specific example. However, it is not limited to the capacitor C.

  The switching elements SW1 to SW15 have a function of being turned on / off by the control of the control unit 42 in order to supply current (potential) to the above-described functional units during each control process (details will be described later). There are no particular limitations on what elements are used, and any element can be used as long as the current path can be switched.

  Next, the APC (light quantity control) operation in the light quantity control device 40 of the present embodiment will be described in detail. Here, a case where the light emitting element CH0 is used as a reference light emitting element will be described in detail as a specific example. FIG. 5 shows a flowchart of an example of the flow of the light amount control process in the light amount control device 40 of the present embodiment. An example of a timing chart of the light amount control process is shown in FIG. In the present embodiment, light amount control is performed in the main scanning signal interval based on the main scanning synchronization signal.

  In step 1000, an initial light amount control process (initial APC, initial APC) is performed. When an instruction for image formation is given, initial APC is executed first, feedback control of the light amount of the reference light emitting element CH0, and the light emission amount of each of the light emitting elements CH1 to n-1 and the reference light emitting element CH0 (light reception of MPD). A process of holding the differential voltage corresponding to the difference of the (quantity) is performed.

  In the next step 1002, image formation driving processing (light quantity control processing: RUN-APC, modulation processing) is performed for each line based on the image data. For each line, RUN-APC is performed in a non-image forming area other than the image forming area before image formation, and after the light amount control, a modulation process is performed to scan and expose the photoreceptor 6.

  In the next step 1004, it is determined whether or not the processing in step 1002 has been completed for all lines. If there is a line that has not been completed yet, the result is negative and the process returns to step 1002 to repeat the image formation drive process. On the other hand, when all the lines have been completed, the determination is affirmed and the present process is terminated.

  Next, each process will be described in detail.

  The initial APC (step 1000 in FIG. 5) will be described. FIG. 7 shows a flowchart of an example of the flow of initial APC.

  First, the light amount control of the reference light emitting element CH0 is performed. At this time, the switching elements SW1, 2, 4, 5, and 6 are turned on. In addition, SW3 is connected to the terminal a and turned on, SW7 is connected to the terminal b and turned on, and SW8 is connected to the terminal a and turned on. The current flow in this case is indicated by a thick line in the circuit diagram of the light quantity control device 40 in FIG.

  First, the reference light emitting element CH0 is turned on with reference current = reference light quantity Vref (step 2000). Based on the light receiving amount (light receiving current) of the MPD at this time, feedback control is performed by the APC-AMP 66 (step 2002). It is determined whether the received light amount of the MPD has reached the target light amount (in this embodiment, as a specific example, 1 mW) (step 2004). If it has not yet reached the target light amount, the result is negative and the process returns to step 2002 for feedback. When the control is repeated and the target light amount is reached, the process proceeds to the next process. FIG. 9 shows the relationship between the voltage conversion value of the light receiving current of the MPD and time when feedback control is performed. As shown in FIG. 9, in the feedback control, it gradually approaches (converges) toward the target light amount value.

  In the present embodiment, when the light emission amount of the reference light emitting element CH0 (MPD received light amount) reaches the target light amount, all the switching elements SW are turned off. As a result, the drive voltage Vv0 of the reference light emitting element CH0 at this time is held in the capacitor C1 of the potential storage unit 74 (step 2006).

  Next, a process of holding a voltage including variation in the amount of light emission between the reference light emitting element CH0 and each of the light emitting devices CH1 to n-1 (holding the light emission amount of each of the light emitting elements CH1 to n-1 having variation as a potential). I do. At this time, the switching element SW9 is turned on. SW7 is connected to the terminal a and is turned on. The current flow in this case is indicated by a thick line in the circuit diagram of the light quantity control device 40 in FIG.

  The drive voltage Vv0 held in the capacitor C1 of the potential storage unit 74 is applied to one of the other light emitting elements CH1 to n−1 to forcibly light it (step 2008). In this embodiment, applying the drive voltage of the reference light emitting element CH0 and lighting the other light emitting elements CH1 to CH-1 in this manner is called forced lighting. FIG. 11 shows a specific example of the light emission amount of the light emitting element CH when forced lighting is performed. In the reference light emitting device CH0, the light emission amount is 1 mW. For example, if a current of 100 μA flows, the light emission device CH1 has a light emission amount of 1.1 mW, and the 0.1 mW light emission amount is larger than that of the reference light emitting device CH0. The received light current is 10 μA higher. In the light emitting element CH2, the light emission amount is 0.9 mW, the 0.1 mW light emission amount is insufficient as compared with the reference light emitting element CH0, and the light receiving current is 10 μA less. The light receiving current of the MPD at the time of forced lighting is held by the voltage Vpd obtained by IV (current-voltage) conversion by the load Z in the capacitor C4 of the potential storage unit 79 (step 2010). Further, the light amount difference voltage Vs (Vs = 1 mW) corresponding to the difference between the voltage Vpd held in the potential storage unit 79 and the voltage corresponding to the light emission amount of the reference light emitting element CH0 (here, the target light amount is 1 mW). May be calculated (step 2012), and the light amount difference voltage Vs may be held in the 1 / N initial APC differential current calculation block 56 (step 2014).

  It is determined whether or not potentials having variations are held for all the light emitting elements CH1 to n-1 except the reference light emitting element CH0 (step 2016). If not yet completed, the processing from step 2008 to step 2010 is used as a reference. The process is repeated when all the light emitting elements CH1 to n-1 except the light emitting element CH0 are repeatedly held, and potentials having variations with respect to all the light emitting elements CH1 to n-1 are held.

  As described above, in the present embodiment, in the initial APC, only the reference light emitting element CH0 performs the light amount control process with feedback control, and the other light emitting elements CH1 to n-1 have the reference light emitting element CH0 when forcedly lit. A potential corresponding to the light emission amount of each light emitting element having variation with respect to the light emission amount is held for each light emitting element.

  Next, the image formation driving process (step 1002 in FIG. 5) will be described. FIG. 12 shows a flowchart of an example of the flow of processing during image formation driving.

  In the image formation driving process of this embodiment, RUN-APC and modulation processing are performed for each line. In the RUN-APC of the present embodiment, more specifically, the light emission amount for each light emitting element CH is 1 / N so that the total light emission amount of all the light emitting elements CH becomes the target light amount (1 mW). X Feedback control is performed so that the target light amount (1 mW) is obtained (see FIG. 13). Note that the RUN-APC method differs depending on whether the first line or other lines.

  Therefore, in this process, first, it is determined whether it is the first line (step 3000). If it is the first line, the switching elements SW4, 10 are first turned on for RUN-APC. Further, SW3 is connected to the terminal a and is turned on, and SW11 is connected to the terminal a and is turned on. The current flow in this case is indicated by a thick line in the circuit diagram of the light quantity control device 40 in FIG.

  For the first line, a current obtained by 1 / N the reference light amount Vref generated by the Vref × 1 / N reference current generation block 52 and a light amount difference voltage generated by the 1 / N initial APC differential current calculation block 56. The RUN-APC reference current generation block 60 adds 1 / N of the current corresponding to Vs to generate a reference current in RUN-APC (step 3002). Furthermore, IV conversion is performed by the load Z, and a reference potential input to the non-inverting terminal of the APC-AMP 66 is generated. The switching element SW4 is turned on, and all the light emitting elements CH are turned on by the reference potential (step 3004).

  Furthermore, the switching elements SW12 and 13 are turned on. SW7 is connected to the terminal c and turned on, and SW8 is connected to the terminal b and turned on. The flow of the light receiving current from the MPD is indicated by a bold line in the circuit diagram of the light quantity control device 40 in FIG. 14 in the same manner as the flow of the reference current. Thereafter, the amount of light received from the MPD is calculated by 1 / N of the MPD light reception current × 1 / N generation block 54 and the current assigned to each light emitting element CH and the 1 / N initial APC differential current calculation block 56. Based on the current corresponding to the calculated light amount difference voltage Vs, the RUN-APC light reception current generation block 62 generates a light reception current at the time of RUN-APC. The generated light receiving current is IV converted by the load Z to become a light receiving potential, and the light receiving potential is input to the inverting terminal of the APC-AMP 66. Further, feedback control is performed by the APC-AMP 66 so that the received light potential becomes the reference potential (step 3006), and the feedback control is repeated until the received light potential becomes the reference potential (step 3008).

  Note that feedback control for setting the light receiving potential to the reference potential is performed simultaneously for all the light emitting elements CH and is performed until each of them converges. By this feedback control, the drive potential (APC drive potential) Vapc of the light emitting element is held in the capacitor C3 of the potential storage unit 78 (step 3018).

  When the light receiving potential is equal to the reference potential in all the light emitting elements CH, the switching elements SW7, 8, 12, and 13 are turned off. As a result, the APC drive potential Vapc held in the capacitor C3 of the potential storage unit 78 is held in the capacitor C2 of the potential storage unit 76 (step 3020).

  After RUN-APC is completed in this way and the light receiving potential is set to the reference potential, modulation processing (processing for scanning and exposing the image forming area of the photoconductor 6 based on the image data to form an image) is performed. Do. In the present embodiment, in the modulation process, specifically, as shown in FIG. 15, in the case of RUN-APC, since the 1 / N light amount is used as the reference light amount, the light amount at the time of modulation is RUN-APC. A driving potential V obtained by multiplying the APC driving potential Vapc by N times is generated for each light emitting element CH so that the received light amount is N times, and the driving potential V is applied to cause each light emitting element CH to emit light. . Thereby, the light emission amounts of all the light emitting elements CH become the same.

  Specifically, simultaneously with all the light emitting elements CH, the switching elements SW14 and 15 are turned on, and the APC drive potential Vapc held in the capacitor C3 of the potential storage unit 78 is multiplied by N by the drive potential generation block 64 to drive the drive potential. V is generated (step 3022) and applied to the light emitting element CH. The current flow at this time is indicated by a thick line in the circuit diagram of the light quantity control device 40 in FIG. A circuit diagram of a specific example of the drive potential generation block 64 is shown in FIG.

  The drive potential generation block 64 of this embodiment includes an operational amplifier 80, a current mirror circuit 82, a load Z, and a capacitor C5. The APC drive potential Vapc is multiplied by N by the current mirror circuit 82, converted to IV by the load Z, becomes the drive voltage V, and is held in the capacitor C5. The capacitor C5 is a specific example of the potential storage means, and is not limited to the capacitor (sample hold capacitor).

  When the RUN-APC for one line and the modulation process are completed, it is determined whether or not all lines have been completed (step 3024). If completed, the process ends. If not, the process proceeds to step 3000. Returning to RUN-APC processing and modulation processing other than the first line.

  For RUN-APC, SW3 is connected to terminal b and turned on, and SW11 is connected to terminal b and turned on. The current flow in this case is indicated by a thick line in the circuit diagram of the light quantity control device 40 in FIG.

  The APC drive potential Vapc held in the capacitor C2 of the potential storage unit 76 is input to the non-inverting terminal of the APC-AMP 66 as a reference potential (step 3010). The switching element SW4 is turned on, and all the light emitting elements CH are turned on by the reference potential (step 3012).

  Furthermore, the switching elements SW12 and 13 are turned on. SW7 is connected to the terminal c and turned on, and SW8 is connected to the terminal b and turned on. The flow of the light receiving current from the MPD is indicated by a bold line in the circuit diagram of the light quantity control device 40 in FIG. 18, similarly to the flow of the reference current. Thereafter, the potential (APC drive potential Vapc of the reference light emitting element CH0) held in the capacitor C2 of the potential storage unit 76 of the reference light emitting element CH0 in the 1 / N RUN-APC differential current calculation block 58, and each light emitting element CH A differential current generated according to the difference from the potential stored in the capacitor C2 of its own potential storage unit 76 (APC drive potential Vapc of each light emitting element itself) is generated, and the generated differential current is calculated from the MPD. The RUN-APC light reception current generation block 62 performs the RUN-APC based on the current assigned to each light emitting element CH calculated by multiplying the light reception amount by 1 / N in the MPD light reception current 1 / N generation block 54. The received light current is generated. The generated light receiving current is IV converted by the load Z to become a light receiving potential, and the light receiving potential is input to the inverting terminal of the APC-AMP 66. Further, feedback control is performed by the APC-AMP 66 so that the received light potential becomes the reference potential (step 3014), and the feedback control is repeated until the received light potential becomes the reference potential (step 3016). The feedback control is the same as in the first line. By the feedback control, the drive potential (APC drive potential) Vapc of the light emitting element is held again in the capacitor C3 of the potential storage unit 78 (step 3018).

  When the light receiving potential is equal to the reference potential in all the light emitting elements CH, the switching elements SW7, 8, 12, and 13 are turned off. As a result, the APC drive potential Vapc held in the capacitor C3 of the potential storage unit 78 is again held in the capacitor C2 of the potential storage unit 76 (step 3020).

  In this way, after RUN-APC is completed and the light receiving potential is set to the reference potential, the modulation processing is executed in the same manner as the first line.

  As described above, in the present embodiment, in the initial APC, only the reference light emitting element CH0 is caused to emit light by applying the reference potential Vref, and the reference potential = received light amount (APC-AMP 66 based on the received light amount from the MPD). The other light emitting elements CH1 to n-1 are controlled in the amount of light emission when forcedly lit with the drive voltage Vv0 of the reference light emitting element CH0 when the reference potential is equal to the light receiving potential. A potential including variation with respect to the light emission amount of the reference light emitting element CH0 (here, the target light amount of 1 mW) is held.

  As described above, in the initial APC of the present embodiment, only the reference light emitting element CH0 performs feedback control, and the other light emitting elements CH1 to n-1 perform forced lighting and do not perform feedback control. Such time is shortened.

  In the image formation driving process, RUN-APC and modulation processing are performed. In RUN-APC, on the first line, the reference potential is generated so that the total light emission amount of all the light emitting elements CH becomes the target light emission amount (1 mW), and all the light emitting elements CH are turned on at the same time. The received light amount assigned to each light emitting element CH is calculated from the amount and the variation Vs of the emitted light amount for each light emitting element CH held in the initial APC, so that the reference potential = the received light amount (the received light potential). The feedback control is performed simultaneously on all the light emitting elements CH. Further, the APC driving potential Vapc applied to each light emitting element CH when the reference potential = light receiving potential is held, and the APC driving potential Vapc is held as the driving potential for the next line for each light emitting element CH. Keep it. In the first line and thereafter, the drive potential for the next line that is held is set as the reference potential, and feedback control is performed simultaneously for all the light emitting elements CH so that the reference potential = the light receiving potential as in the first line.

  In the modulation process, a driving potential V obtained by multiplying the APC driving potential Vapc by N is generated for each light emitting element CH and applied to the light emitting element CH to emit light.

  As described above, in the RUN-APC in the image formation driving process according to the present embodiment, all the light emitting elements CH emit light simultaneously, and feedback control is performed so that the total light emission amount becomes the target light amount. Since the amount of light per control is reduced, the time required for feedback control is shortened, and the amount of light received by the MPD during APC control is reduced, so even when the light emission amount of the light emitting element CH is much larger than the target light amount, Problems such as the saturation of MPD due to excessive light reception are suppressed. Further, since all the light emitting elements use the same amount of light that is 1 / N of the target light amount as a target value, variations in feedback convergence time are suppressed, and the time for feedback control is further shortened.

  Therefore, the light quantity control device 40 of the present embodiment shortens the light quantity control time and improves the accuracy of controlling the light quantity. In addition, since the light amount control time during RUN-APC is shortened, the modulation time (image formation time) for each line is secured for a long time.

  In the present embodiment, in the initial APC, the difference is calculated as the variation in the light emission amount of each light emitting element. However, the present invention is not limited to this, and the light emission amount of the reference light emitting element CH0, the light emission amount of each light emitting element, and Variation may be obtained depending on the ratio.

  In the present embodiment, in RUN-APC, the light amount is controlled so that the total light emission amount of all the light emitting elements CH becomes the target light amount. However, the present invention is not limited to this, and the MPD is smaller than the total light emission amount. There is no particular limitation as long as the amount of light enables feedback control considering performance and performance such as APC-AMP 66. Note that it is preferable to control the light amount so that the total light emission amount of all the light emitting elements CH becomes the target light amount as in the present embodiment, because there are advantages such as a simple circuit configuration.

    [Second Embodiment]

  Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings. In addition, since this Embodiment contains the structure and operation | movement substantially the same as 1st Embodiment, the same code | symbol is attached | subjected to the same part and detailed description is abbreviate | omitted.

  Since the schematic configuration of the optical scanning device 10 of the present embodiment is the same as that of the first embodiment, description thereof is omitted. FIG. 19 is a functional block diagram showing a schematic configuration of an example of the image forming apparatus 101 according to the present embodiment. The image forming apparatus 101 according to the present embodiment includes an image forming control unit 102 and an image forming unit 104 that forms an image based on image data signals output from the image forming control unit 102 and various control signals. ing. The image forming unit 104 includes an optical scanning device 110 and a photoconductor 106.

  The optical scanning device 110 according to the present embodiment includes a light amount control device 140 and N light emitting elements CH whose light emission amounts are controlled by the light amount control device 140. The light amount control device 140 according to the present embodiment and the light amount control device 40 according to the first embodiment operate in substantially the same manner in the initial APC, but the processing during image formation driving is different. The configuration is different. The drive circuit unit 144 of this embodiment includes a module 148 for each light emitting element.

  A functional block diagram showing a schematic configuration of an example of the module 148 of the present embodiment is shown in FIG. The module 148 of the present embodiment includes a feedback control unit 150, a light emission amount difference potential generation unit 152, a difference potential storage unit 154, a correction voltage generation unit 156, a correction difference voltage generation unit 158, and a drive potential generation unit 160. It is configured.

  The feedback control unit 150 according to the present embodiment performs feedback control so that the light emission amount of the light emitting element CH (light reception amount from the MPD) becomes the target light amount, and drives the light emitting element CH when the target light amount is reached. It has a function of holding the potential Vvo. A circuit diagram of a specific example of the feedback control unit 150 is shown in FIG. The feedback control unit 150 includes APC-AMP1, an operational amplifier 170, a potential storage unit 174, a potential storage unit 178, and switching elements SW104 and 109.

  A non-inverting terminal of the APC-AMP 166 is supplied with a reference light potential Vref that is a target light amount (here, 1 mW) as a reference potential. When the SW 104 is turned on, a voltage is applied to the light emitting element CH, and the light emitting element CH emits light. As a result, a light reception current based on the amount of light received from the MPD is input to the inverting terminal of the APC-AMP 166. The APC-AMP 166 has a function of performing feedback control so that reference potential = target light amount (1 mW). The potential storage means 178 has a function of holding the drive potential Vv0 applied to the light emitting element CH when the reference potential = target light quantity (1 mW). In the present embodiment, as a specific example, a capacitor C103 is used. At this time, the SW 109 is turned on / off, whereby the drive potential Vv 0 is held in the capacitor C 101 of the potential storage means 174.

  The light emission amount difference potential generation unit 152 includes the light emission amount of the reference light emitting element CH0 that emits light at the drive potential Vv0 and the light emission amount of the light emitting elements CH01 to n-1 other than the reference light emitting element that emits light at the drive potential Vv0. The difference potential storage unit 154 has a function of storing the difference potential Vs generated by the light emission amount difference potential generation unit 152. Specifically, the difference potential storage unit 154 has a function of generating the difference potential Vs corresponding to the difference. As in other potential storage units, a sample hold capacitor is used.

  The correction value voltage generation unit 156 has a function of generating the correction value voltage Vh of the drive potential Vv0 that fluctuates due to a change with time of a capacitor or the like that stores the potential. The correction difference voltage generation unit 158 has a function of generating a correction difference voltage Vhs obtained by correcting the difference potential Vs of each light emitting element based on the correction value voltage Vh generated by the correction voltage generation unit 156. The drive potential generation unit 160 has a function of generating the drive potential V of each light emitting element CH based on the correction difference voltage Vhs generated by the correction difference voltage generation unit 158 and the drive potential Vv0.

  Next, an APC (light quantity control) operation in the light quantity control device 140 of the present embodiment will be described in detail. Here, as in the first embodiment, the case where the light emitting element CH0 is the reference light emitting element will be described in detail as a specific example. The overall flow (see FIG. 5) and timing (see FIG. 6) of the light quantity control processing in the light quantity control device 140 of the present embodiment are substantially the same as those in the first embodiment, and the description thereof will be omitted.

  In addition, the operation of the initial APC according to the present embodiment is substantially the same as the process flow of the initial APC according to the first embodiment (see FIG. 7). The reference light emitting element CH0 is caused to emit light, and the feedback control unit 150 performs control so that the received light amount = the target light amount (1 mW) (FIG. 7, steps 2000 to 2004), and the drive voltage Vvo of the reference light emitting element ahead is set to the potential. The data is held in the capacitor C101 of the storage unit 174 and the capacitor C103 of the potential storage unit 178 (FIG. 7, step 2006). In the present embodiment, the voltage held in the potential storage means 174 corresponds to the light receiving amount (light receiving potential) Vp0 of the MPD when the reference light emitting element emits light with the drive voltage Vv0.

  The other light emitting elements are forcibly lit at the drive voltage Vv0, and the light emission amount difference potential generation unit 152 causes the difference potential Vs between the light emission amount (MPD light reception amount) Vpd of each light emitting element and the light reception amount Vpd0 of the reference light emitting element CH0. Is generated and held in the differential potential storage unit 154 for all the light emitting elements (FIG. 7, Step 2008 to Step 2016).

  A specific example of the light emission amount of the light emitting element CH when forced lighting is performed is shown in FIG. In the initial APC, as shown in FIG. 22, the differential potential Vs based on the difference in the light emission amount is held for each light emitting element CH.

  As described above, also in the present embodiment, as in the first embodiment, in the initial APC, only the reference light emitting element CH0 performs the light amount control process with feedback control, and the other light emitting elements CH1 to n-1 are forced. A potential corresponding to the light emission amount of each light-emitting element having a variation with respect to the light emission amount of the reference light-emitting element CH0 when turned on is held for each light-emitting element.

  Next, the image formation driving process (FIG. 5, step 1002) of the present embodiment will be described. FIG. 23 shows a flowchart of an example of the flow of processing during image formation driving.

  In the image formation driving process of this embodiment, RUN-APC and modulation processing are performed for each line. In the RUN-APC of the present embodiment, the drive voltage Vv0 of the reference light emitting element CH0 changes from that at the initial APC due to a change in capacitance due to a change with time of the capacitor that holds the potential or a temperature change of the light emitting element CH0. Therefore, the amount of change is obtained as a correction value voltage. In general, since the light-emitting element CH is considered to have the same characteristics with respect to environmental changes, the other light-emitting elements CH1 to n-1 are considered to have undergone similar changes due to changes over time. Then, the process of correcting the differential voltage Vs with the correction value voltage obtained by the reference light emitting element CH0 is performed. Further, in the modulation process, a process of generating the drive potential V of the light emitting element CH using the corrected differential voltage (corrected differential voltage Vhs) is performed.

  First, a reference potential = a reference light potential Vref is applied to light the reference light-emitting element CH0 (step 4000). Based on the received light amount of MPD, feedback control is performed (step 4002), and the process is repeated until the received light amount = target light amount (1 mW) (step 4004).

  The drive voltage Vv0run of the reference light emitting element CH0 when the amount of received light is equal to the target light quantity is held (step 4006), and the difference between the drive voltage Vv0 and the drive voltage Vv0run at the initial APC is calculated as the correction value voltage Vh. (Step 4008).

  Further, based on the correction value voltage Vh, the light amount difference voltage Vs of each of the light emitting elements CH1 to n-1 is corrected to calculate the correction difference voltage Vhs (step 4010). Specifically, Vhs = Vh / Vv0 × Vs + Vs. The correction differential voltage Vhs is applied to each light emitting element CH1 to n-1.

  Further, in the modulation process, the drive potential V of each light emitting element CH is generated based on the corrected differential voltage Vhs (step 4012). Specifically, V = Vv0 in the reference light emitting element, and V = Vv / (MPD light receiving potential at the time of applying Vv + Vhs) in the other light emitting elements CH1 to n-1. These processes are repeated for all the lines, and when all the lines are completed, this process is terminated (step 4014).

  As described above, in the present embodiment, in the initial APC, only the reference light emitting element CH0 is caused to emit light by applying the reference potential Vref, and the reference potential = light receiving amount ( The other light emitting elements CH1 to n-1 are controlled in the amount of light emission when forcedly lit with the drive voltage Vv0 of the reference light emitting element CH0 when the reference potential is equal to the light receiving potential. A potential including variation with respect to the light emission amount of the reference light emitting element CH0 (here, the target light amount of 1 mW) is held.

  As described above, in the initial APC of the present embodiment, only the reference light emitting element CH0 performs feedback control, and the other light emitting elements CH1 to n-1 perform forced lighting and do not perform feedback control. Such time is shortened.

  As described above, in the RUN-APC in the image formation driving process according to the present embodiment, feedback control is performed so that only the reference light emitting element CH0 has the target light amount, and correction indicating the amount of change in the drive voltage Vs in consideration of changes over time and the like. The value voltage Vh is calculated, and regarding the other light emitting elements CH1 to n-1, it is considered that the same change has occurred, and the light amount difference voltage Vs held in the initial APC is corrected based on the correction value voltage Vh. Accordingly, since only the reference light emitting element CH0 performs feedback control, the time required for feedback control is shortened.

  Therefore, the light quantity control device 140 of the present embodiment shortens the light quantity control time and improves the accuracy of controlling the light quantity. In addition, since the light amount control time during RUN-APC is shortened, the modulation time (image formation time) for each line is secured for a long time.

  In the first embodiment and the second embodiment described above, the reference light emitting element is the light emitting element CH0. However, the present invention is not limited to this, and other light emitting elements CH may be used. In addition, it is preferable that the standard is the most standard light amount and current amount among the plurality of light emitting elements. Further, instead of using the same light emitting element CH as a reference every time, the most preferable one may be selected according to the time. For example, a standard light amount (ideal value) is stored in the storage unit of the control unit 42 (control unit 142), and the light closest to the standard light amount is used as a reference, or all the light emitting elements CH emit light. It may be based on a value closest to the average amount of light.

DESCRIPTION OF SYMBOLS 1,101 Image forming apparatus 10, 110 Optical scanning device 40, 140 Light quantity control apparatus

Claims (7)

Detecting means for detecting the originating light intensity of the light emitting element,
In the initial light amount control process, based on the luminescence amount detected by the detection means, the light emission amount of the reference light-emitting element of the multiple light-emitting element, the reference light-emitting element such that the predetermined light emission amount First control means for controlling a voltage to be applied based on a voltage according to a reference current and a voltage according to the light emission amount of the reference light emitting element;
First storage means for storing, as a reference voltage, a voltage applied to the reference light emitting element when the light emission amount of the reference light emitting element reaches the predetermined light emission amount under the control of the first control means;
And the light emission amount of the reference light-emitting element in the case of applying the reference voltage, before SL of each light-emitting element when by applying the reference voltage stored emit light each of the plurality of light emitting elements in the first storage means second memory means for storing a first voltage corresponding to the difference or ratio between the light emission amount for each light emission element,
During processing the image forming drive adds a voltage corresponding to the reference current divided by the number of the plurality of light emitting elements, and a value obtained by dividing the number of the first voltage the plurality of light emitting elements Applying a reference voltage generated for each of the plurality of light emitting elements to cause the plurality of light emitting elements to emit light simultaneously ,
The addition value of the current corresponding to the detected light intensity divided by the number of the plurality of light emitting elements by the detection means, and a value obtained by dividing the number of said first plurality of light emitting elements a current corresponding to the voltage a second control means for calculating the photocurrent for each of the plurality of light emitting elements, simultaneously controls before Symbol plurality of the light emission amount of each light emitting device such that the voltage corresponding to the photocurrent becomes the reference voltage and,
By multiplying the voltage which the voltage corresponding to the photocurrent is applied to the each of the plurality of light emitting elements when became the reference voltage by the number of the plurality of light emitting elements, generates a driving voltage of each of the plurality of light emitting elements Generating means for
A light quantity control device comprising: The second control means controls the light emission amount for each of the plurality of light emitting elements for each of the plurality of light emitting elements for each line based on image data, and for the second and subsequent lines, the light receiving current is controlled by controlling the first line. each light-emitting element to the applied voltage as the reference voltage, the light emission amount of each pre-Symbol plurality of light emitting elements so that a voltage corresponding to the photocurrent becomes the reference voltage when the voltage becomes the reference voltage corresponding to To control the
The light quantity control device according to claim 1. A plurality of light emitting elements;
The light quantity control device according to claim 1 or 2, wherein the light emission amount of the plurality of light emitting elements is controlled.
An optical scanning device comprising: An optical scanning device according to claim 3,
A photosensitive member exposed by a beam emitted from a plurality of light emitting elements provided in the optical scanning device based on image data;
An image forming apparatus. Detecting means for detecting the amount of light emitted from the plurality of light emitting elements;
In the initial light amount control process, based on the light emission amount detected by the detection means, the light emission amount when light is emitted by applying a voltage corresponding to a reference current to the reference light emitting element of the plurality of light emitting elements, First control means for controlling the light emission amount to be predetermined;
First storage means for storing, as a reference voltage, a voltage applied to the reference light emitting element when the light emission amount of the reference light emitting element reaches the predetermined light emission amount under the control of the first control means;
Depending on the difference or ratio between the light emission amount of the reference light emitting element and the light emission amount of the light emitting element when light is emitted by applying the reference voltage stored in the first storage means to light emitting elements other than the reference light emitting element. Second storage means for storing the first voltage for each light emitting element other than the reference light emitting element;
A second control means for controlling the light emission amount of the reference light emitting element that emits light by applying a voltage to the predetermined light emission amount in the image formation driving process;
A correction value voltage corresponding to a difference or a ratio between the reference voltage and a voltage applied when the light emission amount of the reference light emitting element emitted by the control of the second control unit becomes the predetermined light emission amount. Correction voltage generation means for generating a correction voltage corrected by calculating and calculating the correction value voltage / the reference voltage × the first voltage + the first voltage, for each of the plurality of light emitting elements;
The driving voltage obtained by correcting the voltage applied when the light emission amount of the reference light emitting element, which is emitted by the control of the second control means, becomes the predetermined light emission amount by the correction voltage is driven for each of the plurality of light emitting elements. Drive voltage generating means for generating a voltage;
A light quantity control device comprising: A plurality of light emitting elements;
The light quantity control device according to claim 5, wherein the light emission amount of the plurality of light emitting elements is controlled.
An optical scanning device comprising: An optical scanning device according to claim 6;
A photosensitive member exposed by a beam emitted from a plurality of light emitting elements provided in the optical scanning device based on image data;
An image forming apparatus.

Images