JP2006251242A - Optical scanner, method of optical scanning and optical scanning program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem that the light quantity for sync detection is not sufficiently obtained, synchronizing jitter is increased thus the image is deteriorated. <P>SOLUTION: The optical scanner is primarily characterized in that a scanned light beam is detected, a plurality of light emitting elements are controlled by using information obtained by the detection and the emitting times of the light beams are synchronized. Briefly explaining these primary characteristics, a light receiving element 14 arranged out of the scanning region of a photoreceptor drum 17 detects a laser beam and makes a detection signal on the basis of the detected result. Further, an LD control part so controls an LD unit that the light emitting time of the LD unit is synchronized on the basis of the detection signal obtained by the light receiving element. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical scanning device that scans a light beam emitted from a laser diode, and in particular, an optical scanning device and an optical scanning method for writing an image with a light beam in a digital copying machine, a laser beam printer, a facsimile, and the like. And an optical scanning program.

  2. Description of the Related Art Conventionally, in an image forming apparatus represented by a laser printer, light that draws an image on the surface of a charged drum-shaped photoreceptor by deflecting and scanning a light beam emitted from a laser diode (LD) with a rotating polygon mirror. Scanning is generally performed.

  In such an optical scanning device, since the rotary polygon mirror is usually rotated at a very high speed, a slight rotation unevenness occurs or the accuracy of the rotary polygon mirror is slightly inferior. There is a concern about the malfunction that causes the deviation.

  For this reason, for example, in Patent Document 1 (Japanese Patent Application Laid-Open No. 2002-162586), a light beam scanned by a rotating polygon mirror is arranged by disposing a synchronization detecting element in an ineffective scanning area where a photoconductor does not exist on a scanned surface. An image with no deviation in the writing position on the photosensitive member by detecting this when passing through the synchronization detection element, generating a synchronization detection signal, and correcting the modulation timing of the light beam based on this synchronization detection signal Can be formed.

JP 2002-162586 A

  However, in the above-described technique, there may be a mismatch between the light amount required for the photoconductor and the light amount required for the synchronization detection element. When the amount of light required for the photosensitive member is smaller, there is a problem that the amount of synchronization detection light cannot be sufficiently obtained, and the synchronization jitter increases and the image deteriorates.

  Therefore, in the present invention, even when the amount of light necessary for the photosensitive member is smaller than the amount of light necessary for the synchronization detection element, sufficient light is given to the synchronization detection element to prevent the image from being deteriorated due to an increase in synchronization jitter. An object is to provide a scanning device, an optical scanning method, and an optical scanning program.

  In order to solve the above-mentioned problems and achieve the object, the invention according to claim 1 is an optical scanning device that scans a light beam by controlling a light emitting element that generates the light beam, the scanned light beam And a light emitting element control means for controlling a plurality of light emitting elements using information obtained by the detecting means to synchronize the light emission timings of the plurality of light beams. .

  According to a second aspect of the present invention, in the above invention, when the light emitting element control means adjusts the light emission amount of the light emitting element to be lower than a predetermined light amount, the plurality of light emitting elements emit light simultaneously. And adjusting the light emission amount.

  The invention according to claim 3 is characterized in that, in the above invention, the light emitting element control means adjusts the light emission amount by controlling the number of light emitting elements that emit light according to the light emission amount of the light emitting element. To do.

  According to a fourth aspect of the present invention, in the above invention, the light emitting element control means sets a light amount larger than a period other than the period during the period in which the light emitting element emits light for detection. Features.

  According to a fifth aspect of the present invention, in the above invention, the light emitting element control means calculates a total light emission amount of the plurality of light emitting elements during a period in which the light emitting element emits light for detection. It is characterized by setting to.

  In the invention according to claim 6, in the above invention, when the light emitting element control means causes the light emitting element to emit light for detection, the light emission amounts of the plurality of light emitting elements are substantially equal to each other. It is characterized by setting to.

  According to a seventh aspect of the present invention, in the above invention, the light emitting element control means is configured to calculate a sum of distances between the beam spots scanned on the scanned surface when the light emitting elements emit light simultaneously for detection. The light-emitting elements that generate the light beam that is minimized are caused to emit light simultaneously.

  According to an eighth aspect of the present invention, in the above invention, the light emitting element control means is configured such that the beam spot array formed on the surface to be scanned by the light emitting element that is turned on when the detection is performed is an interval in the scanning direction of each beam spot. The maximum value is less than or equal to one-half of the beam spot diameter.

  The invention according to claim 9 is an optical scanning method for scanning a light beam by controlling a light emitting element that generates the light beam in the above invention, and a detection step for detecting the scanned light beam; And a light-emitting element control step of controlling a plurality of light-emitting elements using information obtained in the detection step to synchronize the light emission timings of the plurality of light beams.

  According to a tenth aspect of the present invention, there is provided an optical scanning program for causing a computer to execute a method of scanning a light beam by controlling a light emitting element that generates the light beam according to the above invention. And a light emitting element control procedure for controlling a plurality of light emitting elements using information obtained by the detection procedure to synchronize the light emission timings of the plurality of light beams. And

  According to the invention of claim 1, 9 or 10, even when the light amount necessary for the photosensitive member is smaller than the light amount necessary for the synchronization detection element, a sufficient amount of light is given to the synchronization detection element to increase the synchronization jitter. It is possible to provide an apparatus for preventing the image from deteriorating.

  According to the invention of claim 2, an apparatus for preventing damage to the synchronous detection element by preventing the allowable light quantity of the synchronous detection element from being exceeded, and reducing the use energy when the light beam has a large light quantity value. Can be provided.

  According to the invention of claim 3, even when there is a large gap between the amount of light required by the photosensitive member and the amount of light required for the synchronization detection element, a sufficient amount of light is given to the synchronization detection element to increase synchronization jitter, etc. Thus, it is possible to provide an apparatus for preventing the image from deteriorating.

  According to the invention of claim 4, even when there is a large gap between the amount of light required by the photosensitive member and the amount of light required for the synchronization detection element, a sufficient amount of light is given to the synchronization detection element to increase synchronization jitter, etc. Thus, it is possible to provide an apparatus for preventing the image from deteriorating.

  According to the invention of claim 5, it is possible to avoid a large change in the amount of light incident on the synchronization detecting element even before and after the amount of light changing the number of light emitting elements, and to prevent the image from being deteriorated due to a change in synchronization jitter characteristics. An apparatus can be provided.

  According to the sixth aspect of the present invention, it is possible to provide an apparatus that prevents the image from deteriorating due to the synchronization detection position shift by preventing the beam profile from being collapsed.

  According to the seventh aspect of the present invention, it is possible to provide an apparatus for preventing an image from deteriorating due to a synchronization detection position shift by preventing a collapse of a beam profile in the scanning direction of a combined beam.

  According to the eighth aspect of the present invention, it is possible to provide an apparatus that prevents the image from deteriorating due to the synchronization detection position shift by preventing the beam profile in the scanning direction of the combined beam from collapsing.

  Embodiments of an optical scanning device, an optical scanning method, and an optical scanning program according to the present invention will be described below in detail with reference to the accompanying drawings.

  Hereinafter, the optical scanning device according to the first embodiment will be described. In the first embodiment, a laser diode array (hereinafter referred to as LDA) in which four light sources that can be individually controlled are arranged in an array on one chip is used as a light source for a plurality of laser beams. It is assumed that the LDA uses only one built-in photodiode (PD) for detecting the amount of light.

  First, the outline and features of the optical scanning device according to the first embodiment will be described with reference to FIG. FIG. 1 is a configuration diagram showing a configuration of a laser beam printer.

  In the laser beam printer, as shown in FIG. 1, inside the laser diode unit (LDU) 13, the four laser beams emitted from the LDA are emitted as parallel rays by a collimating lens, and are rotated polygon mirrors (hereinafter referred to as a rotating polygon mirror). After being deflected and scanned by a polygon mirror 11, an image is formed as four beam spots close to the charged surface of the drum-shaped photoconductor 17 in the sub-scanning direction by an imaging lens composed of an f-θ lens 12. . At this time, each laser beam is individually modulated on the basis of the image signal, repeatedly turned on and off, and repeatedly scanned in the main scanning direction indicated by the arrow in the drawing according to the rotation of the polygon mirror 11 and simultaneously scanned for four lines. Then, the photosensitive drum 17 rotates to perform sub-scanning, thereby forming an electrostatic latent image on the photosensitive drum 17. The formed electrostatic latent image is developed with a charged developer (toner), and a transfer material such as transfer paper to which a charge opposite to that of the developer is applied is brought into close contact with the photosensitive drum 17. Developer is transferred to the transfer material. Then, after the transfer material is separated from the photosensitive drum 17, the developer is fused on the transfer material by heating, and fixing is performed.

  Therefore, the main feature of the present invention is that a scanned light beam is detected and information obtained by the detection is used to control a plurality of light emitting elements to synchronize the light emission timings of the plurality of light beams. This main feature will be briefly described. The light receiving element 14 arranged outside the scanning region on the photosensitive drum 17 detects a laser beam and generates a detection signal based on the detected result. The LD control unit controls the LD unit so that the light emission timing of the LD unit is synchronized based on the detection signal obtained by the light receiving element. The light receiving element 14 corresponds to the “detecting means” recited in the claims, and the LD control unit corresponds to the light emitting element control means.

  Next, the details around the LD control unit will be described. First, in the optical scanning apparatus of this embodiment, as shown in FIG. 2, a central processing unit 21 (hereinafter referred to as CPU) controls the entire laser printer. The LD control unit 22 electrically processes the image data, and in parallel with the LDU 23 constituted by the LDA 23b, the LD driver 23a, etc., three signals of an image data signal (DATA in the figure), a light quantity control signal, and a sample / hold signal. Is transmitting.

  Four LD drivers 23a in the LDU 23 are prepared corresponding to the four LDs built in the LDA 23b, and the corresponding LDs are respectively driven. Therefore, only two LD drivers 23a are shown as representatives in order to avoid complication of the figure. Here, each LD driver 23a drives the corresponding LD based on the transmitted signal. Then, outside the effective scanning period, the APC (automatic power control) is sequentially performed for each LD by the sample and hold signal (S / H signal) being in the sample state. APC is performed by feeding back the monitor current generated by the photodiode (PD) built in the LD package to the LD driver 23a built in the APC circuit.

  During the effective scanning period, the output current of the driver is fixed to a constant value by the S / H signal being held. Next, a circuit block diagram of the APC circuit built in the LD driver 23a is shown in FIG. 3, and the operation of the APC circuit will be described. Here, an APC circuit is built in each LD driver 23a, but the configuration of each APC circuit is completely the same, so only one APC circuit will be described.

The LD is supplied with a bias current that does not always cause LD light emission. During the APC operation, a data signal that is an LD lighting signal and a sample signal that follows are transmitted as control signals from an image processing unit that is an LD control device. The LD lighting signal switches the switch circuit of FIG. 3 ON, and the sample signal switches the S / H switch ON. Then, a signal current based on the voltage value of the hold capacitor flows from the current generation circuit to the LD through the switch circuit and is added to the bias current, so that the LD emits light, and a current proportional to the light intensity of the LD becomes PD. Flow into. Then, the value of the current flowing through the PD in the I / V conversion circuit 23a ₂ is converted into a voltage.

As with the reference voltage signal inputted from the outside for each ch basis of the converted voltage and the LD light amount is hold capacitor based on the comparison result by the comparator 23a ₁ is charged or discharged, that the voltage value changes The output current of the current generation circuit is controlled, and the LD light quantity is controlled to be constant. At the time of image writing, the S / H signal is changed to a hold signal, and the S / H switch is turned off. As a result, since the value of the hold capacitor is fixed to a constant value, the current flowing from the current generation circuit to the LD is fixed to a constant value. Based on the image data signal sent from the LD control unit, the LD modulation switch circuit inside the LD driver 23a is switched, and the LD light source is modulated to write an image on the photosensitive member.

  Now, in the first embodiment, the emitted light quantity of the LD is changed by changing the light quantity reference voltage shown in FIG. 3 through the light quantity control signal shown in FIG. 2 according to the conditions of the photoconductor and the like. It can be changed. Then, as shown in FIG. 4, the number of LD lights for synchronization detection is changed in accordance with the amount of emitted LD light. And each time chart according to the number of lighting is shown in FIGS.

  Further, in Example 1, the LDs that emit light simultaneously at the time of synchronization detection are LDs that form the closest beam spots on the surface to be scanned as shown in FIG. Even when three or more LDs are lit, the one that minimizes the sum of the intervals between the beam spots is selected. Furthermore, in order to prevent the collapse of the beam profile in the scanning direction synthesized by each beam, the beam spot array formed on the surface to be scanned by the LD that is turned on at the time of synchronization detection is shown in FIG. It is assumed that the optical adjustment is performed so that the maximum value d is equal to or less than ½ of the beam spot diameter w. The effect by this is shown below.

  The reason for adjusting the maximum value d of the scanning direction interval of each beam spot to be ½ or less of the beam spot diameter w is as follows. It is known that the light intensity distribution at an arbitrary point of the optical system becomes a Gaussian distribution when the aberration of the lens is ignored. Normally, the beam spot diameter of a Gaussian beam is defined as the radius from the peak value of the light intensity at the center to the point where the light intensity becomes 1 / e2 of the peak value. The beam spot diameter is defined from the point where the intensity is 1 / e2 to 1 / e2 of the peak value. As shown in FIG. 11, when the beam spot radius corresponding to half of the beam spot diameter w is defined as ωo, the light intensity distribution can be expressed by the equation (1) shown in FIG. 27, where r is the distance from the center.

  Considering that a Gaussian beam is irradiated onto a cross section perpendicular to the optical axis, which is the surface to be scanned, to form a beam spot, the light intensity is Gaussian distributed in the x and y directions on the cross section. However, suppose here that the center of two Gaussian beams is aligned in the x direction to form a beam spot. Further, the x direction is considered as the beam scanning direction. This is shown in FIG. Further, when the light intensity distribution on the x-axis is graphed, it is as shown in FIG.

  When the distance d between the centers of the two beam spots is ½ or less of the beam spot diameter w, the light intensity distribution has only a single peak, but the distance d between the centers of the two beam spots is equal to the beam spot diameter. Beyond 1/2 of w, the light intensity distribution waits for a bimodal peak. This is shown in FIG. And why such a phenomenon occurs is shown below by calculation.

  First, in order to make the problem easier to understand, only the light intensity distribution in the x direction is considered.To simplify the calculation, the light intensity distribution is normalized as ωo = √2, Io = 1. Equation (2) shown in FIG.

  Further, considering the light intensity distributions in which the beam spot is shifted by a and −a in the x direction around the origin, they can be expressed by equations (3) and (4) shown in FIG. 27, respectively. (However, a ≧ 0.)

  Furthermore, the total light intensity distribution obtained by combining these two light intensity distributions is (5) shown in FIG. This is shown in FIG.

And to find the peak position of this light intensity distribution,
dI / dx = 0 Equation (6)
By calculating x such that, the candidate for the peak position is obtained. When formula dI / dx = 0 is rearranged using formula (7) obtained by executing dI / dx on the left side of formula (6), formula (8) is obtained. Furthermore, since Expression (9) holds, x satisfying Expression (10) is obtained. That is, the intersection value of Equation (11) and Equation (12) is the value of x to be obtained and becomes a peak position candidate. Here, considering the variable X, if the equations (13) and (14) are graphed, the result is as shown in FIG.
tanhX <X (X> 0)
tanhX = X (X = 0)
tanhX> X (X <0)
Therefore, if X = 2ax is set here, from Equation (15), the result is as shown in FIG. 17, and from the intersection of the graph in FIG. 17, when the condition: 1 / 2a ² ≧ 1 is satisfied, dI / dx It can be seen that x satisfying x = 0 satisfies one condition of x = 0: when x 1 / 2a ² <1, x satisfying dI / dx = 0 is three including x = 0.

Therefore, in order to have one light intensity distribution peak, it is only necessary to satisfy 1 / 2a ² ≧ 1, that is, to satisfy Expression (16). In order to satisfy this equation 16, ωo = √2 is set here, and it can be seen that a should be ½ or less of the beam spot radius ωo. Here, the light intensity distribution was considered as ωo = √2, Io = 1, but even if ωo, Io take other different values, the light intensity distribution graphs are in the x direction and the I direction, respectively. Since only the enlarged graph is obtained, it can be seen that the general characteristic that the combined light intensity distribution becomes a single peak if a is equal to or smaller than the beam spot radius ωo. Therefore
d = 2a
w = 2ωo
Therefore, it can be seen that the light intensity distribution has only a single peak if the distance d between the centers of the two beam spots is set to ½ or less of the beam spot diameter w.

  In the above description, only the light intensity distribution in the x direction, which is the beam scanning direction, is considered. However, with respect to the influence of the distance between the beam spots in the y direction, as shown in FIG. In comparison, since it has a sufficiently large spread in the y-axis direction, even if the beam spots are shifted in the y-axis direction, there is almost no influence on the synchronous detection operation, and can be ignored.

  Regarding the fact that the beam itself has a spread in the y-axis direction, the light intensity distribution on the line parallel to the x-axis that deviates from the x-axis by a certain amount in the y-axis direction is the light intensity on the x-axis. As long as the distribution is multiplied by a certain constant, the light intensity distribution of the portion deviated by a certain amount in the y-axis direction from the beam spot center should be considered in the same way as above whether the peak is unimodal or bimodal. Can do.

The reason why the light intensity distribution on the line parallel to the x axis is considered to be obtained by multiplying the light intensity distribution on the x axis by a certain constant will be described. The light intensity distribution can express the distance from the center as a function of r as shown in Equation 1, but as is well known, using the fact that it is Equation (17), I (r) = I (x) I (y) can be transformed.
On the line parallel to the x axis, y is a constant value yo, so if I (yo) = k, then I (r) = k I (x), and the light intensity on the line parallel to the x axis It can be seen that the distribution can be thought of as the light intensity distribution on the x-axis multiplied by a constant.

  Therefore, if the beam spot scanning direction interval d is ½ or less of the beam spot diameter w, the beam profile is not affected when viewed from the synchronization detecting element. Similarly, even when using a plurality of beams of n = 2 or more, if the maximum value d in the scanning direction interval of each beam spot is 1/2 or less of the beam spot diameter w, when viewed from the synchronization detection element, It can be seen that the beam profile is not affected.

  Hereinafter, an optical scanning device according to a second embodiment will be described with reference to FIGS. 19 to 22. Also in the second embodiment, since the configuration is almost the same as that of the first embodiment, only the light emission amount at the time of synchronous detection is changed, and therefore the description of the same portion is omitted as much as possible. Since the configuration is exactly the same, it is omitted. In the second embodiment, APC is performed outside the effective scanning period as in the first embodiment. Since the operation of the APC circuit built in the LD driver 23a is almost the same as that of the first embodiment, the description thereof is omitted.

  Now, also in the second embodiment, by changing the light quantity reference voltage shown in FIG. 3 through the light quantity control signal shown in FIG. 2 according to the conditions of the photoconductor and the like, the emitted light quantity of the LD is changed. Shall be able to. Then, as in the first embodiment, the number of synchronous detection LD lighting is changed in accordance with the LD emission light quantity. And each time chart according to the number of lighting is shown in FIGS.

  However, in the second embodiment, an analog bias current control signal is transmitted from the LD control unit 22 to the LDU 23 in addition to the control signal shown in FIG. It is assumed that the bias current value set to is output as an analog bias current control signal via the DAC 22 a in the LD control unit 22. The LD driver 23a in the LDU 23 drives the LD by adjusting the amount of bias current based on the bias current control signal. This is shown in FIGS.

  Now, as shown in FIG. 21, the bias current control signals of all the LD drivers are controlled so that the voltage rises periodically in accordance with the timing when the LDs are turned on for synchronization detection. To do. During this time, APC control is not performed. As a result, a large amount of bias current is added to the LD only during the LD lighting period for synchronization detection, and the respective LD emission amounts within the LD lighting period are increased as compared with the image data output time.

  Thus, even if a plurality of LDs are simply turned on, even if the incident light quantity to the synchronization detection element is less than the threshold light quantity of the synchronization detection element, the threshold light quantity is exceeded by increasing each LD emission quantity. The incident light quantity can be realized, and as a result, the synchronous detection can be surely performed. This is shown in FIG.

  Hereinafter, an optical scanning device according to Example 3 will be described with reference to FIGS. 23 to 24. Also in Example 3, since the configuration is almost the same as that of the second example, the only difference is that the amount of light emission at the time of synchronization detection is always constant. Since the configuration is exactly the same, it is omitted. In the third embodiment, APC is performed outside the effective scanning period as in the second embodiment. Since the operation of the APC circuit built in the LD driver 23a is almost the same as that of the first embodiment, the description thereof is omitted.

  Now, also in this embodiment, by changing the light quantity reference voltage shown in FIG. 20 via the light quantity control signal shown in FIG. 19 according to the conditions of the photoconductor and the like, the emitted light quantity of the LD is changed. Shall be able to. Then, as in the second embodiment, the number of synchronous detection LD lighting is changed in accordance with the LD emission light quantity. And each time chart according to the number of lighting is shown in FIGS. Similarly to the second embodiment, the LD driver in the LDU transmits a bias current control signal having an analog value in addition to the control signal shown in FIG. 19 from the LD control unit to the LDU. It is assumed that the LD is driven by adjusting the amount of bias current based on the current control signal.

  Further, in this embodiment, even when the LD light quantity is changed by changing the light quantity reference voltage according to the conditions of the photoconductor and the like, the incident light quantity to the synchronization detecting element is always substantially the same at the time of synchronization detection. In addition, a bias current value corresponding to the light amount reference voltage obtained experimentally and theoretically in advance is stored in the register of the LD control unit 22, and the bias current value corresponding to the light amount reference voltage is stored in the LD control unit. It is assumed that it is output as an analog value via the DAC 22a and applied to the LD when synchronization is detected.

  FIG. 23 shows the relationship between the LD light quantity at the time of image data output and the bias current value to be set. When outputting image data, the bias current is kept constant, and a signal current determined as a result of the APC operation based on the light amount reference voltage is added to the bias current to drive the LD, thereby controlling the LD at a constant current.

  At this time, since the magnitude of the signal current is determined as a result of the APC operation based on the light quantity reference voltage, it can be seen that the magnitude of the signal current changes according to the light quantity reference voltage. On the other hand, when the LD for synchronization detection is lit, in order to keep the LD light quantity constant, by setting a bias current determined in advance according to the LD light quantity at the time of data output, the signal current according to the light quantity reference voltage is set. By canceling the change, the LD drive current which is the sum of the signal current and the bias current can be kept constant.

  As a result, regardless of the change in the light quantity reference voltage, that is, the LD light quantity at the time of data output, the LD light quantity when the synchronization detection LD is lit is always kept constant. This is shown in FIG. At this time, as a bias current value stored in the register of the LD control unit, a bias current value corresponding to the LD light amount is not simply stored, but the LD light amount and the LD temperature are used as parameters. The bias current value may be stored, and the bias current may be determined from the current value stored in the register based on the value obtained by measuring the LD light amount control signal and the LD ambient temperature with a thermocouple or the like.

  Hereinafter, an optical scanning device according to Example 4 will be described with reference to FIGS. Also in the fourth embodiment, the configuration is almost the same as that of the second embodiment, except that the LD light emission amount at the time of synchronization detection is the same as each LD. Since the configuration is exactly the same, it is omitted. In the fourth embodiment, as in the second embodiment, APC is performed outside the effective scanning period. Since the operation of the APC circuit built in the LD driver 23a is almost the same as that of the second embodiment, the description thereof is omitted.

  Now, also in the fourth embodiment, by changing the light quantity reference voltage shown in FIG. 20 via the light quantity control signal shown in FIG. 19 according to the conditions of the photoconductor and the like, the emitted light quantity of the LD is changed. Shall be able to. Then, similarly to the second embodiment, the number of synchronous detection LDs is changed in accordance with the amount of emitted LD light. And each time chart according to the number of lighting is shown in FIGS.

  Similarly to the second embodiment, the LD driver 23a in the LDU 23 transmits an analog bias current control signal in addition to the control signal shown in FIG. 19 from the LD control unit 22 to the LDU 23. It is assumed that the LD is driven by adjusting the amount of bias current based on the bias current control signal.

  Further, in the fourth embodiment, each light amount to be emitted at the time of synchronization detection even when the light amount is changed for each LD by changing the light amount reference voltage for each LD according to the conditions of the photoconductor, the optical system, etc. Are stored in the register of the LD control unit 22 in advance so that the bias current value corresponding to the light intensity reference voltage of each LD, which has been experimentally and theoretically obtained in advance, in the same manner as in the second embodiment, The bias current value corresponding to the light quantity reference voltage is output as an analog value via the DAC in the LD control unit 22 and is applied to the LD at the time of synchronization detection. FIG. 25 shows the relationship between the LD light amount when outputting image data and the bias current value to be set.

  In FIG. 25, only the LD1 and LD2 are illustrated for easy understanding of the concept. When outputting image data, the bias current is kept constant, and a signal current determined as a result of the APC operation based on the light quantity reference voltage of each LD is added to the bias current to drive the LD, thereby controlling each LD at a constant current. To do.

  At this time, since the magnitude of the signal current is determined as a result of the APC operation based on the light quantity reference voltage, it can be seen that the magnitude of the signal current of each LD changes according to each light quantity reference voltage. On the other hand, when the synchronization detection LD is lit, in order to keep the light quantity of each LD equal, a bias current predetermined in accordance with each LD light quantity at the time of data output is set for each LD. By canceling the difference in signal current of each LD according to the difference in the light amount reference voltage, the LD drive current, which is the sum of the signal current and the bias current, can be kept equal for each LD.

  As a result, regardless of the change in the light amount reference voltage, that is, the light amount difference for each LD at the time of data output, the LD light amount when the synchronization detection LD is lit is always kept constant. This is shown in FIG. At this time, as a bias current value stored in the register of the LD control unit, a bias current value corresponding to each LD light amount is not simply stored, but each LD light amount and LD temperature are used as parameters. A corresponding bias current value may be stored, and the bias current may be determined from the current value stored in the register based on a value obtained by measuring the LD light amount control signal and the LD ambient temperature with a thermocouple or the like. . Furthermore, the third embodiment and the fourth embodiment may be combined so that the respective LD light amounts are equal at the time of synchronization detection, and the LD light amount at the time of synchronization detection may be constant regardless of the light amount reference voltage.

  Although the embodiments of the present invention have been described so far, the present invention may be implemented in various different forms other than the embodiments described above. Accordingly, as the image forming apparatus according to the fifth embodiment, various different embodiments will be described by dividing them into (1) system configuration and (2) hardware configuration, respectively.

(1) System configuration, etc. Of the processes described in this embodiment, all or part of the processes described as being automatically performed can be performed manually, or can be performed manually. All or part of the described processing can be automatically performed by a known method. In addition, the processing procedure, control procedure, specific name, and information including various data and parameters shown in the above-described document and drawings can be arbitrarily changed unless otherwise specified.

  Further, each component of each illustrated apparatus is functionally conceptual, and does not necessarily need to be physically configured as illustrated. In other words, the specific form of distribution / integration of each device is not limited to that shown in the figure, and all or a part thereof may be functionally or physically distributed or arbitrarily distributed in arbitrary units according to various loads or usage conditions. Can be integrated and configured. Further, all or any part of each processing function performed in each device may be realized by a CPU and a program analyzed and executed by the CPU, or may be realized as hardware by wired logic.

(2) Hardware Configuration FIG. 28 is a block diagram illustrating a hardware configuration of the optical scanning device according to the embodiment. As shown in the figure, the optical scanning apparatus has a configuration in which a controller 100 and an engine unit (Engine) 600 are connected by a PCI (Peripheral Component Interconnect) bus. The controller 100 is a controller that controls the entire multifunction device 1 and controls drawing, communication, and input from an operation unit (not shown). The engine unit 600 is a printer engine that can be connected to a PCI bus, and is, for example, a monochrome plotter, a one-drum color plotter, a four-drum color plotter, a scanner, or a fax unit. The engine unit 600 includes an image processing part such as error diffusion and gamma conversion in addition to a so-called engine part such as a plotter.

  The controller 100 includes a CPU 110, a north bridge (NB) 130, a system memory (MEM-P) 120, a south bridge (SB) 140, a local memory (MEM-C) 170, and an ASIC (Application Specific Integrated Circuit). 160 and a hard disk drive (HDD) 180, and the north bridge (NB) 130 and the ASIC 160 are connected by an AGP (Accelerated Graphics Port) bus 150. The MEM-P 120 further includes a ROM (Read Only Memory) 120a and a RAM (Random Access Memory) 120b.

  The CPU 110 performs overall control of optical scanning, has a chip set composed of the NB 130, the MEM-P 120, and the SB 140, and is connected to other devices via this chip set.

  The NB 130 is a bridge for connecting the CPU 110 to the MEM-P 120, the SB 140, and the AGP 150, and includes a memory controller that controls reading and writing with respect to the MEM-P 12, a PCI master, and an AGP target.

  The MEM-P 120 is a system memory used as a memory for storing programs and data, a memory for developing programs and data, a memory for drawing a printer, and the like, and includes a ROM 120a and a RAM 120b. The ROM 120a is a read-only memory used as a memory for storing programs and data, and the RAM 120b is a writable and readable memory used as a program / data development memory, a printer drawing memory, and the like.

  The SB 140 is a bridge for connecting the NB 130 to a PCI device and peripheral devices. The SB 140 is connected to the NB 130 via a PCI bus, and a network interface (I / F) unit and the like are also connected to the PCI bus.

  The ASIC 160 is an IC (Integrated Circuit) for image processing applications having hardware elements for image processing, and has a role of a bridge for connecting the AGP 150, the PCI bus, the HDD 180, and the MEM-C 170, respectively. The ASIC 160 includes a PCI target and an AGP master, an arbiter (ARB) that forms the core of the ASIC 160, a memory controller that controls the MEM-C 170, and a plurality of DMACs (Direct Memory) that rotate image data using hardware logic. Access Controller) and a PCI unit that performs data transfer between the engine unit 600 via the PCI bus. An FCU (Fax Control Unit) 300, a USB (Universal Serial Bus) 400, and an IEEE 1394 (the Institute of Electrical and Electronics Engineers 1394) interface 500 are connected to the ASIC 160 via a PCI bus.

  The MEM-C 170 is a local memory used as a copy image buffer and a code buffer. An HDD (Hard Disk Drive) 180 is a storage for storing image data, programs, font data, and forms. It is.

  The AGP 150 is a bus interface for a graphics accelerator card proposed for speeding up graphics processing. The AGP 150 speeds up the graphics accelerator card by directly accessing the MEM-P 120 with high throughput. .

  As described above, the optical scanning device, the optical scanning method, and the optical scanning program according to the present invention are useful for scanning a light beam by controlling a light emitting element that generates the light beam, and particularly, an image deteriorates. Suitable for preventing

It is a figure which shows an example of a structure of a laser beam printer. FIG. 3 is a configuration diagram illustrating a configuration around an LD control unit according to the first embodiment. It is a block diagram of an APC control circuit. It is a figure which shows the relationship between LD emitted light quantity and the number of light emitting element lighting. It is a control signal time chart at the time of one light emitting element for synchronous detection. It is a control signal time chart at the time of two light emitting elements for synchronous detection. It is a control signal time chart at the time of three light emitting elements for synchronous detection. It is a control signal time chart at the time of four light emitting elements for synchronous detection. It is a figure which shows the positional relationship of the beam spot which a light emitting element produces on a to-be-scanned surface. It is a figure which shows the inclination of the beam arrangement | sequence on a to-be-scanned surface. It is a figure which shows the definition of a beam spot diameter. It is a figure which shows the light intensity distribution of the beam spot on a to-be-scanned surface. It is a figure which shows the scanning direction light intensity distribution on a to-be-scanned surface. It is a figure which shows the shape of a synthetic | combination beam profile. It is a figure which shows the total light intensity distribution obtained by synthesize | combining two light intensity distribution. It is a figure which shows the graph of Formula 13. It is a figure which shows the conditions for the light intensity distribution peak being one. It is a figure which shows the magnitude | size and position of a synchronous detection element and a beam spot. FIG. 6 is a diagram illustrating a configuration around an LD control unit according to a second embodiment. FIG. 6 is a block diagram of an APC control circuit according to a second embodiment. It is a figure which shows the timing chart of a bias current control signal. It is a figure which shows the effect of increasing each LD light-emission amount. It is a figure which shows the relationship between the LD light quantity and the bias current value to set. It is a figure which shows the relationship between LD light quantity at the time of image data output, and LD light quantity at the time of synchronous detection. It is a figure which shows the relationship between the light quantity for every LD, and the bias current value to set. It is a figure which shows the relationship between each LD light quantity at the time of image data output, and each LD light quantity at the time of synchronous detection. It is a figure which shows the type | formula which concerns on an optical scanning device. It is a block diagram which shows the hardware constitutions of an optical scanning device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Polygon mirror 12 F- (theta) lens 13 LD unit 14 Light receiving element 15 Synchronization detection mirror 16 Reflection mirror 17 Photosensitive drum 21 CPU
22 LD controller 23 LDU
23a LD driver 23b LDA
22a, 23c DAC

Claims (10)

An optical scanning apparatus that scans a light beam by controlling a light emitting element that generates the light beam,
Detecting means for detecting the scanned light beam;
A light emitting element control means for controlling a plurality of light emitting elements using information obtained by the detection means to synchronize the light emission timings of the plurality of light beams;
An optical scanning device comprising:   The light emitting element control means adjusts the light emission amount by simultaneously emitting light from the plurality of light emitting elements when the light emission amount of the light emitting element is adjusted to be lower than a predetermined light amount. The optical scanning device according to 1.   The optical scanning device according to claim 1, wherein the light emitting element control unit adjusts the light emission amount by controlling the number of light emitting elements that emit light according to the light emission amount of the light emitting element.   4. The optical scanning device according to claim 3, wherein the light emitting element control unit sets a light amount larger than a period other than the period during which the light emitting element emits light for detection.   4. The light according to claim 3, wherein the light emitting element control unit sets a total light emission amount of the plurality of light emitting elements to a constant light amount during a period in which the light emitting element emits light for detection. Scanning device.   4. The light according to claim 3, wherein the light emitting element control unit sets the light emission amounts of the plurality of light emitting elements to substantially equal light amounts when the light emitting element emits light for detection. Scanning device.   The light emitting element control means simultaneously emits light emitting elements that generate light beams that minimize the sum of the distances between the beam spots scanned on the scanned when the light emitting elements emit light simultaneously for detection. The optical scanning device according to claim 1.   The light emitting element control means has a beam spot array formed on the surface to be scanned by the light emitting element that is turned on when detecting, so that the maximum value in the scanning direction interval of each beam spot is not more than one-half of the beam spot diameter. The optical scanning device according to claim 1, wherein: An optical scanning method for scanning a light beam by controlling a light emitting element that generates a light beam,
A detecting step of detecting the scanned light beam;
A light emitting element control step of controlling a plurality of light emitting elements using information obtained by the detection step to synchronize the light emission timings of the plurality of light beams;
An optical scanning method comprising: An optical scanning program for causing a computer to execute a method of scanning a light beam by controlling a light emitting element that generates the light beam,
A detection procedure for detecting the scanned light beam;
A light emitting element control procedure for controlling a plurality of light emitting elements using information obtained by the detection procedure to synchronize the light emission timings of the plurality of light beams;
An optical scanning program that causes a computer to execute the above.

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