JP5987372B2 - Optical output control circuit, optical scanning device, and image forming apparatus - Google Patents

Description

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

  A surface emitting laser (VCSEL: Vertical Cavity Surface Emitting LASER) is characterized by a low threshold, low power consumption, and easy inspection and two-dimensional arraying in a wafer state. Because of these features, it can be used as an alternative to conventional edge-emitting lasers in image forming devices such as laser printers, optical recording devices such as optical disks, optical communications, and light sources for image reading devices and image display devices. Research and development is in progress.

  As a light amount control method for a two-dimensional VCSEL array used in an image forming apparatus, a surface on which a surface emitting laser array is formed at a time between image data output periods as described in Patent Document 1. The light emitting lasers are sequentially turned on one by one, and the output current of the photodiode detected at that time is converted into voltage and then converted into digital data. The converted digital data is preset in each surface emitting laser. There is a method of matching the target light amount by intermittently changing the drive current of the surface emitting laser to be controlled so as to coincide with the target value. This method itself is not unique to the two-dimensional VCSEL array, but is known as a method for controlling the amount of light of a semiconductor laser element. For example, Patent Document 2 discloses the method.

  However, in the methods described in Patent Documents 1 and 2, when the target light amount is reduced, the magnitude of the signal at the input of the means for converting to digital data is also reduced, so that the quantization error of the digital data is increased. As a result, there is a problem that the accuracy of the light amount control is deteriorated.

  Therefore, the present invention has been made in view of the above, and even when the target light quantity is reduced, the accuracy of the light quantity control does not deteriorate, that is, the light quantity with high accuracy without depending on the target light quantity. It is an object of the present invention to provide a light output control circuit, an optical scanning device, and an image forming apparatus in a semiconductor laser or an optical scanning device capable of performing control.

The present invention is a light output control circuit for controlling light emission of a semiconductor laser, a light receiving element that receives light emitted from the semiconductor laser, and a current-voltage conversion unit that converts a current detected in the light receiving element into a voltage. An integration circuit that performs a predetermined time integration based on the converted voltage, an A / D conversion unit that converts the output from the integration circuit into digital data, and the digital data converted by the A / D conversion unit And a D / A converter for converting an output from the digital operation unit into an analog signal, and performing a calculation so that the light amount of the semiconductor laser becomes a predetermined light amount. A current flowing through the semiconductor laser, and when the light intensity of the semiconductor laser is low in the integrating circuit, the predetermined time is Ku, wherein when light intensity of the semiconductor laser is high state, and are not the predetermined time is shortened, the from off of the semiconductor laser, a predetermined delay time to start A / D conversion in the A / D converter and it said to Rukoto to.

According to another aspect of the present invention, there is provided a light output control circuit for controlling light emission of a semiconductor laser, wherein a light receiving element that receives light emitted from the semiconductor laser, and a predetermined time integration based on a current detected in the light receiving element. An integrating circuit to perform, an A / D converter for converting the output from the integrating circuit into digital data, and a light quantity of the semiconductor laser based on the digital data converted by the A / D converter so as to be a predetermined light quantity A digital operation unit that performs an operation on the digital signal, and a D / A converter that converts an output from the digital operation unit into an analog signal, and a current based on the analog signal flows to the semiconductor laser, In the integration circuit, when the light amount of the semiconductor laser is low, the predetermined time is long, and when the light amount of the semiconductor laser is high, All SANYO a predetermined time shorter, from said off of the semiconductor laser, and wherein to Rukoto constant delay time until the A / D conversion start in the A / D converter.

  According to the present invention, it is possible to provide a light output control circuit, a light scanning device, and an image forming apparatus in a semiconductor laser or a light scanning device capable of performing light amount control with high accuracy without depending on a target light amount. it can.

Structural diagram of a surface emitting laser drive circuit according to the first embodiment Illustration of optical output of surface emitting laser module Structure diagram of light output control circuit in first embodiment Time chart of light output control method by light output control circuit in first embodiment Explanatory drawing of the light output control method by the light output control circuit in 1st Embodiment Explanatory drawing of the other light output control method by the light output control circuit in 1st Embodiment Structure diagram of light output control circuit in second embodiment Explanatory drawing of the light output control circuit in 3rd Embodiment Configuration diagram of laser printer in fourth embodiment Configuration of Optical Scanning Device in Fourth Embodiment Illustration of surface emitting laser array The block diagram of the color printer in 5th Embodiment

  The form for implementing this invention is demonstrated below. In addition, about the same member etc., the same code | symbol is attached | subjected and description is abbreviate | omitted.

[First Embodiment]
(Light output control circuit)
An optical output control circuit of the optical scanning device according to the first embodiment will be described. In this embodiment, the optical output of a semiconductor laser is controlled in an optical scanning device or the like in which a semiconductor laser such as a surface emitting laser is used. In this embodiment, a surface emitting laser is used as the semiconductor laser. However, the present invention can be similarly applied to an edge emitting semiconductor laser. A surface emitting laser is a semiconductor substrate in which a lower semiconductor DBR, a lower spacer layer, an active layer, an upper spacer layer, an upper semiconductor DBR, a contact layer, and the like are laminated and formed of a semiconductor material including GaAs. And an upper electrode connected to the contact layer and a lower electrode formed on the back surface of the semiconductor substrate. In such a VCSEL, a laser beam is emitted in a direction perpendicular to the semiconductor substrate surface by passing a current between the upper electrode and the lower electrode.

  FIG. 1 shows a driving circuit 100 in which a surface emitting laser is used as a light emitting element. The drive circuit 100 includes a surface emitting laser module 101, a photodiode 102 as a light receiving element, a controller 103, a VCSEL drive circuit unit 105, a power supply circuit (not shown), an interface circuit with the outside, and the like.

  The surface emitting laser module 101 includes four surface emitting lasers 101a to 101d. The anode electrodes of the surface emitting lasers 101a to 101d are connected to the surface emitting lasers 101a to 101d in the VCSEL drive circuit unit 105, respectively. These are connected to VCSEL drive circuits 105a to 105d provided corresponding to 101d. Further, the cathode electrodes of the surface emitting lasers 101a to 101d are connected to each other and then to the ground potential. In addition, each cathode electrode of the surface emitting lasers 101a to 101d may be connected to a cathode other than the ground potential and having a constant potential.

  The surface emitting lasers 101a to 101d are turned on when the current supplied from the VCSEL driving circuits 105a to 105d flows. The light thus lit enters the photodiode 102 after passing through optical members such as a lens, an aperture, and a mirror (not shown). The photodiode 102 has a cathode electrode connected to the light output control circuit 104 in the controller 103, and an anode electrode connected to the ground potential. The anode electrode of the photodiode 102 may be connected to a potential other than the ground potential. For example, the anode electrode is connected to a constant potential that can be reverse biased or zero biased. May be. In such a photodiode 102, when light emitted from the surface emitting lasers 101a to 101d is incident, a current corresponding to the amount of incident light flows by the photovoltaic force.

  The controller 103 has a light output control circuit 104, and controls the amount of light and the lighting timing when the surface emitting lasers 101a to 101d emit light. As the light amount control at the time of light emission, in addition to the light output control circuit 104 for setting the emitted light output to a predetermined light amount for each of the surface emitting lasers 101a to 101d, the image height on the photoconductor surface (not shown). In order to shorten the delay time at the start of light emission in the surface emitting lasers 101a to 101d, a bias that allows a current smaller than the laser oscillation threshold to flow even when the light is extinguished. There are current circuits.

  The controller 103 outputs setting values for controlling the light quantity, and these outputs are input to the respective VCSEL driving circuits 105 a to 105 d in the VCSEL driving circuit unit 105.

  For example, as shown in FIG. 2, the surface emission laser module 101 controls the light emission timing of the surface emitting lasers 101 a to 101 d to form an image on a photosensitive drum such as an image forming apparatus during a time A of one main scanning line. Time B and time C1 and C2 for adjustment before and after time B, etc., and each operation is repeated at a constant cycle. Further, the time C1 and C2 for adjustment and the like are further divided for various adjustments. For example, the time C1 for adjustment and the like includes a synchronization detection time D and the like. The time C2 includes the light output control time E and the like.

  The controller 103 outputs a timing signal for blinking the surface emitting lasers 101a to 101d to the VCSEL driving circuits 105a to 105d based on an image forming signal from the outside during image formation. Moreover, in the time for adjustment etc., the timing signal for blinking the surface emitting lasers 101a-101d is output to the VCSEL drive circuits 105a-105d at a preset time.

  As described above, the VCSEL drive circuits 105a to 105d output a current having a magnitude based on the set value of the light amount control from the controller 103 to the surface emitting lasers 101a to 101d, and the surface emitting lasers 101a to 101d receive the current from the controller 103. Flashes based on the timing signal.

  Next, the light output control circuit in the present embodiment will be described with reference to FIG. The light output control circuit 104 in this embodiment includes a current-voltage conversion unit 201, an integration circuit 202, an A / D converter 203, a digital operation unit 204, a register 205, a D / A converter 206, a reference voltage source 208, and a multiplexer 270. And 271 etc.

Current - voltage conversion unit 201 has a function of converting the output current of the photodiode 102 into a voltage, the resistance value of converting the amplifier 210 and the current to voltage has a transimpedance resistor 211 and the like of R _TI .

The integration circuit 202 has a function of integrating the output from the photodiode 102 that has been converted into a voltage by the current-voltage conversion unit 201, and includes an amplifier 220, an input resistance 221 having a resistance value of R _INT , and a capacitance of C _INT Capacitor 222, a switch 223 for discharging the electric charge stored in capacitor 222, and the like.

  The A / D converter 203 has a function of converting the output from the photodiode 102 integrated in the integration circuit 202 into digital data. In the present embodiment, the A / D converter 203 is a kind of A / D converter, and when it is described as an A / D converter, the A / D converter 203 is also included. There is.

  The register 205 has a function of holding digital data, holds registers 250a to 250d that hold the value of the output data of the A / D converter 203 targeted in the optical output control, and holds the calculation result in the digital calculation unit 204. Registers 251a to 251d. The registers 250a to 250d and the registers 251a to 251d are provided in one-to-one correspondence with each of the surface emitting lasers 101a to 101d.

  The D / A converter unit 206 includes D / A converters 260 a to 260 d, and the current value when the surface emitting lasers 101 a to 101 d are turned on based on digital data held in the register 205 is a VCSEL driving circuit. The function of outputting to 105 is provided. The D / A converters 260a to 260d are provided in one-to-one correspondence with the surface emitting lasers 101a to 101d.

  The reference voltage source 208 has a function of supplying a DC voltage serving as a reference for operation to the amplifier 210 in the current-voltage conversion unit 201 and the amplifier 220 in the integration circuit 202.

  The multiplexer 270 has a function of selecting digital data in the registers 250 a to 250 d and outputting the digital data to the digital arithmetic unit 204 during the light output control operation of the surface emitting lasers 101 a to 101 d. As described above, the digital data in the registers 250a to 250d is provided in one-to-one correspondence with the surface emitting lasers 101a to 101d.

  The multiplexer 271 has a function of selecting digital data in the registers 251 a to 251 d and outputting the digital data to the digital arithmetic unit 204 during the light output control operation of the surface emitting lasers 101 a to 101 d. As described above, the digital data in the registers 251a to 251d is provided in one-to-one correspondence with the surface emitting lasers 101a to 101d.

  The digital arithmetic unit 204 outputs the output data of the A / D converter 203, the value of the output data of the A / D converter 203 targeted by the optical output control held in the registers 250a to 250d selected in the multiplexer 270, Calculation is performed based on the set values of the D / A converters 260a to 260d corresponding to the surface emitting lasers 101a to 101d in the previous light output control operation held in the registers 251a to 251d selected in the multiplexer 271. New setting values of converters 260a to 260d are calculated and output to registers 251a to 251d.

  Next, the operation of the light output control circuit in this embodiment will be described. FIG. 4 is a timing chart showing the operation in the light output control circuit 104. The timing chart shown in FIG. 4 shows the light output control time E in FIG. 2 in more detail. Specifically, at the light output control time E for each main scanning line, the surface emitting laser 101a. The light output control operation is performed once for each of the surface emitting laser 101b, the surface emitting laser 101c, and the surface emitting laser 101d in this order. The reset signal in the integration circuit 202, the A / D conversion timing signal of the A / D converter 203, the data update timing signal of the registers 251a to 251d, the signal for selecting the signal output from the multiplexer 270 and the multiplexer 271, The values of the output data of the A / D converter 203 targeted by the optical output control held in the registers 250a to 250d and the initial values of the calculation results in the digital calculation unit 204 in the registers 251a to 251d are shown in FIG. Although not input from the controller 103 and set.

In Figure 4, the light output control operation is started at time T _1, the switch 223 of the integrator circuit 202 is reset in the integrating circuit 202 is turned off is canceled. At the same time, the output of the register 250 a is selected by the multiplexer 270, the output of the register 251 a is selected by the multiplexer 271, and each is output to the digital operation unit 204.

  Then, at the time E of the previous light output control, the current set in the VCSEL drive circuit 105a, which is the output of the D / A converter 260a, is supplied to the surface emitting laser 101a, and the surface emitting laser 101a is turned on, not shown. Light enters the photodiode 102 via the optical system.

In the photodiode 102, when light from the surface emitting laser 101a is incident, a current corresponding to the amount of incident light flows. Assuming that the current flowing at this time is i _A , the current i _A is input to the current-voltage conversion means 201 of the light output control circuit 104.

The cathode of the photodiode 102 in the current-voltage conversion unit 201 is connected to the inverting input terminal of the amplifier 210. In the amplifier 210, the current i _A flows toward the cathode of the photodiode 102, so that the transimpedance resistor 211 causes the voltage of the inverting input terminal to be equal to the voltage of the non-inverting input terminal from the output terminal to the inverting input terminal. since negative feedback is applied, the voltage of the _{R TI} × _{i a} is generated when the resistance value of the transimpedance resistor 211 and _{R TI.} Since the voltage at the inverting input terminal and the non-inverting input terminal of the amplifier 210 is the output voltage Vref of the reference voltage source 208 connected to the non-inverting input terminal, the voltage at the output terminal of the amplifier 210 is Vref + R _TI × i _A Become.

The output of the amplifier 210 is the output of the current-voltage conversion unit 201, and this output is input to the integration circuit 202. The output of the amplifier 210 is connected to one terminal of the input resistor 221, and the voltage is Vref + R _TI × i _A. The voltage of the other terminal of the input resistor 221 is connected to the inverting input terminal of the amplifier 220. The inverting input terminal of the amplifier 220 is connected to the inverting input terminal voltage from the output terminal to the inverting input terminal by the integrating capacitor 222. = Because negative feedback is applied so as to be the voltage at the non-inverting input terminal, Vref.

Since a voltage of Vref + R _TI × i _A −Vref = R _TI × i _A is applied to both ends of the input resistor 221, assuming that the resistance value of the input resistor 221 is R _INT , the input resistor 221 has (R _TI × i _A ) / R _INT = (R _TI / R _INT ) × i _A current flows, and the integration capacitor 222 is charged by this current. Assuming that the capacitance of the integrating capacitor 222 is C _{INT and} the elapsed time from the beginning of the current flow is t, the charge of (R _TI / R _INT ) × i _A × t is charged. The voltage between the terminals changes with time in accordance with the amount of charge charged, and the magnitude is (1 / C _INT ) × (R _TI / R _INT ) × i _A × t. Here, negative feedback is applied from the output terminal of the amplifier 220 so that the voltage at the inverting input terminal of the amplifier 220 to which one terminal of the integration capacitor 222 is connected does not change from Vref. , The current flowing through the integrating capacitor 222 flows toward the output terminal of the amplifier 220. Therefore, it becomes lower than the inverting input terminal, and its value is Vref− (1 / C _INT ) × (R _TI / R _INT ) × i _A × t.

Then, when the surface emitting laser 101a is turned off after the time t _{A has} elapsed, the current flowing into the photodiode 102 becomes zero and the output of the current-voltage conversion unit 201 returns to Vref, the voltage between the two terminals of the input resistor 221 are equal, the current also becomes zero flow the input resistor 221 to the integrating capacitor 222, the voltage of the output terminal of the amplifier 220, the voltage Vref- _{(1 / C INT)} at the point time _{t a} lapse × _{(R TI} / R _INT ) × i _A × t _A remains constant.

The output of the amplifier 220 is the output of the integrating circuit 202 and is input to the A / D converter 203. The output of the A / D converter 203 is input to the digital arithmetic unit 204. In the A / D converter 203, when the surface emitting laser 101a is extinguished at time t _A and delayed by a fixed time t _d1 and the A / D conversion timing signal rises, the output of the integration circuit 202 is sampled and A / D conversion is performed. The output data is updated to the data of the current optical output of the surface emitting laser 101a after a certain time has elapsed. On the other hand, in the integration circuit 202, when the update of the output data in the A / D converter 203 starts, the switch 223 is turned on for a certain time t _rst after the time t _d2 allowing for the delay of the update of the output data, and the integration capacitor 222 is discharged. Here, _trst is a time sufficient for the electric charge charged in the integrating capacitor 222 to be discharged.

  The digital arithmetic unit 204 outputs the output data of the A / D converter 203 and the output data of the A / D converter 203 targeted by the light output control operation of the surface emitting laser 101a selected by the multiplexer 270 held in the register 250a. And the setting value of the D / A converter 260a corresponding to the surface emitting laser 101a in the light output control operation in the previous main scanning line selected by the multiplexer 271 held in the register 251a. The new set value of the D / A converter 260a is calculated and output to the register 205.

In the register 205, after the sampling of the A / D converter 203 is completed, when the timing signal for updating the data in the registers 251 a to 251 rises after the time t _{d3 when the} calculation delay in the digital calculation unit 204 is expected, the light amount of the surface emitting laser 101 a The register 251a that holds the setting data is updated. The data in the registers 251b to 251d other than the register 251a that holds the light amount setting data of the surface emitting laser 101a that is the light output control target is not updated.

  In the D / A converter 206, when the data in the register 251a is updated, the output of the D / A converter 260a connected to the register 251a is changed to the data value in the new register 251a and output to the VCSEL drive circuit 105a. To do.

Then, the light output control operation of the now surface-emitting laser 101a the time _{T 2} ends and the light output control operation of the surface emitting laser 101b is started, the output of the register 250b in the multiplexer 270 is selected, the register 251b in multiplexer 271 Outputs are selected and input to the digital operation unit 204, respectively.

  Then, at the time E of the light output control in the previous main scanning line, the current set in the VCSEL drive circuit 105b by the output of the D / A converter 260b flows to the surface emitting laser 101b, so that the surface emitting laser 101b is turned on. Then, light enters the photodiode 102 via an optical system (not shown), and the same light output control operation as that of the surface emitting laser 101a is performed. The light output control operation of the surface emitting laser 101b is different from the light output control operation of the surface emitting laser 101a because the data selected by the multiplexer 270 and the multiplexer 271 and output to the digital operation unit 204 is held in the registers 250b and 251b. The register that is updated by the output of the digital arithmetic unit 204 is the register 251b, and the D / A converter that changes the output is the D / A converter 260b. This corresponds to the laser 101b.

Then at time T _3, the light output control operation is finished in the surface emitting laser 101b, the light output control operation in the surface-emitting laser 101c then begins running. Further, at the time T _4, the light output control operation is finished in a surface emitting laser 101c, the light output control operation in the surface emitting laser 101d starts running next.

Then, at time T _5, the light output control operation of the surface emitting laser 101d is completed, the switch 223 is turned on in the integrating circuit 202, so that higher voltages are not applied that exceeds the input range to the A / D converter 203 To complete the light output control operation.

In the light output control circuit 104, the target light amount of the semiconductor laser is changed while the voltage Vref− (R _TI / (R _INT × C _INT )) × i _A × t _A at the time t _{A has} elapsed. At this time, since Vref, R _TI , R _INT , and C _INT are fixed values, i _A × t _A is set to be constant. For example, when the target light quantity is set to ¼, if the lighting time of the surface emitting laser is increased by four times, i _A / 4 × t _A × 4 = i _A × t _A , and i _A × t _A is constant. It becomes. By doing so, the magnitude of the signal at the input of the A / D converter 203 does not change even if the target light quantity changes, and the value of the output data of the A / D converter 203 is constant and held in the registers 250a to 250d. The value of the output data of the A / D converter 203 targeted by the optical output control is also constant.

In the case shown in FIG. 5, the lighting timing of the surface emitting laser is fixed when the target light quantity is ¼, and the lighting time is extended by extending the turn-off timing backward as the target light quantity decreases. The delay T _d1 of the A / D conversion timing signal in the A / D converter 203 is uniquely determined based on the extinction of the surface emitting laser, and the output of the integrating circuit 202 is converted into digital data from the extinction of the surface emitting laser. By making the delay time until it is constant, the influence of droop of the capacitor used in the integration circuit 202 can be eliminated. Further, the delay T _d2 of the reset signal of the integration circuit 202 and the delay T _d3 of the data update timing signal in the registers 251a to 251d are based on the rise of the timing signal of the A / D conversion of the A / D converter 203 as a reference. Even if the target light amount changes, each is uniquely determined.

In the case shown in FIG. 6, when the target light amount is ¼, the timing for turning off the surface emitting laser is fixed, and as the target light amount decreases, the lighting timing is advanced and the lighting time is lengthened. The A / D conversion timing signal delay T _d1 in the A / D converter 203 is based on the extinction of the surface emitting laser, so that the A / D conversion timing signal delay of the A / D converter 203 is the same as in FIG. T _d1 is uniquely determined, and the influence of droop of the capacitor used in the integrating circuit 202 can be eliminated by making the delay time from turning off the semiconductor laser to converting the output of the integrating circuit 202 into digital data constant. it can. Further, the delay T _d2 of the reset signal of the integrating means 202 and the delay T _d3 of the data update timing signal of the registers 251a to 251d are based on the rise of the timing signal of the A / D conversion of the A / D converter 203 as a reference. Even if the target light amount changes, each is uniquely determined.

  In the case shown in FIGS. 5 and 6, the time required for the light output control operation per one surface emitting laser is such that the processing is completed even when the target light quantity with the longest lighting time is the minimum. It is necessary to.

  The light output control circuit and the light output control method of the semiconductor laser in the present embodiment can be used for light amount setting of an optical scanning device or the like which will be described later. In this case, high-definition contrast and gradation on the surface of the photosensitive drum. A latent image having excellent tone can be formed by scanning.

  In addition, since the image forming apparatus described later includes an optical scanning device using this light amount control method, it is possible to form a high-definition image with good contrast linearity at high speed. As described above, the light output control circuit in this embodiment can also control the edge emitting laser instead of the surface emitting laser.

[Second Embodiment]
Next, a second embodiment will be described. This embodiment is a light output control circuit having a structure different from that of the light output control circuit in the first embodiment. The light output control circuit 304 in this embodiment will be described with reference to FIG. The light output control circuit 304 in this embodiment is not provided with the current-voltage conversion unit 201 in the light output control circuit 104 in the first embodiment shown in FIG. 3 and the input resistor 221 in the integration circuit 202. Of structure. That is, the light output control circuit 304 in this embodiment is not provided with the current-voltage conversion unit 201, and the integration circuit 302 is stored in the amplifier 220, the capacitor 222 having a capacitance of C _INT , and the capacitor 222. It is formed by a switch 223 or the like for discharging the generated electric charge. For this reason, in the light output control circuit 304 in this embodiment, the cathode of the photodiode 102 is connected to the inverting input terminal of the amplifier 220 in the integration circuit 302. In the present embodiment, in the integration circuit 302, the integration capacitor 222 has a function corresponding to a current-voltage conversion unit.

The operation of the light output control circuit 304 in this embodiment is also described with reference to the timing chart shown in FIG. 4. However, since the direction of the current charging the integration capacitor 222 is reversed, the polarity of the output of the integration circuit 302 is Is positive instead of negative, and the voltage at the output terminal of the amplifier 220 at the time t _{A has} elapsed is Vref + (1 / C _INT ) × i _A × t _A. If the output of the integrating circuit 302 is to be negative, the anode of the photodiode 102 is replaced with the inverting input terminal of the amplifier 220 in the integrating circuit 302 instead of the cathode of the photodiode 102, and the photodiode 102 is reverse-biased or zero-biased. It is only necessary to connect to a certain potential. In the optical output control circuit 104 in the first embodiment shown in FIG. 3, the voltage at the output terminal of the amplifier 220 is added to the capacitance C _INT of the integrating capacitor 222, the resistance value T _TI of the transimpedance resistor 211 and the input resistance 221. whereas with a large freedom of design because it determined by the resistance R _iN, the light output control circuit 304 of this embodiment shown in FIG. 7, the design flexibility because it is determined only by the C _INT is small However, since the current-voltage conversion unit 201 and the input resistor 221 in the integration circuit 202 in the light output control circuit 104 of the first embodiment are not provided, the light output control circuit can be reduced, and It can be manufactured at low cost.

  The contents other than the above are the same as in the first embodiment.

[Third Embodiment]
Next, a third embodiment will be described. By the way, in the drive circuit 100 or the like in which the surface emitting laser is used, there is no variation in the optical system and the target light quantity in the surface emitting laser constituting the surface emitting laser module 101 is the same, or the surface emitting laser module 101 is configured. When there is only one surface emitting laser (single element), the target light quantity is one. In such a case, the light output control circuit uses an A / D converter 409 having a plurality of comparators instead of the A / D converter 203 as means for converting an analog signal into digital data. Also good.

  The light output control circuit in this embodiment will be described with reference to FIG. FIG. 8 shows an A / D converter 409 used in this embodiment in place of the A / D converter 203 in the first embodiment and the second embodiment.

  As described above, the A / D conversion unit 409 has a function of converting an analog signal into digital data, and includes four resistors 490a to 490d, five comparators 491a to 491e, and five latches 492a to 492e. Etc.

  First, the four resistors 490a to 490d will be described. One end of the resistor 490a is connected to the reference voltage VerfRa supplied from the reference voltage source 208, the other end of the resistor 490a is connected to one end of the resistor 490b, and the other end of the resistor 490b is The other end of the resistor 490c is connected to one end of the resistor 490d, and the other end of the resistor 490d is connected to the reference voltage VerfRe supplied from the reference voltage source 208. It is connected. Note that the relationship between the two reference voltages VerfRa and VerfRe is VerfRa> VerfRe. When the voltage at the point where the resistor 490b and the resistor 490c are connected is VerfRb, the voltage at the point where the resistor 490b and the resistor 490c are connected is VerfRc, and the voltage at the point where the resistor 490c and the resistor 490d are connected is VerfRd. VerfRa> VerfRb> VerfRc> VerfRd> VerfRe. For the resistors 490a to 490d, the resistance value of the resistor 490a = the resistance value of the resistor 490d, the resistance value of the resistor 490b = the resistance value of the resistor 490c, and further, the resistance value of the resistors 490a and 490d ≧ the resistance values of the resistors 490b and 490c. It is formed to have a resistance value.

  Next, the comparators 491a to 491e will be described. The non-inverting terminals of the comparators 491a to 491e are connected to the output of the integrating circuit 202. At the non-inverting input terminal, the voltage VerfRa is input to the comparator 491a, and the voltage VerfRb is input to the comparator 491b. The voltage VerfRc is input to the comparator 491c, the voltage VerfRd is input to the comparator 491d, and the voltage VerfRe is input to the comparator 491e. The comparators 491a to 491e compare the output of the integrating circuit 202 with the reference voltages VerfRa to VerfRe respectively connected thereto. When the output of the integrating circuit 202 is large, “1” is output, and when it is small, “0” is output. Is output.

Next, the latches 492a to 492e will be described. The latches 492a to 492e hold the outputs of the comparators 491a to 491e and output them to the digital arithmetic unit 204. Updating of the latch 492a~492e, as in the case of A / D converter 203 shown in FIG. 3, performed when the VCSEL101a has a predetermined time _{t d1} delay off at time _{t A.}

  In the digital operation unit 204, when the polarity of the signal of the integrating circuit 202 is negative as in the first embodiment, the outputs of the latches 492a to 492b are “0” and the outputs of the latches 492c to 492e are “1”. On the other hand, when the polarity of the signal of the integrating circuit 202 is positive as in the second embodiment, the outputs of the latches 492d to 492e are “0” and the outputs of the latches 492a to 492c are “1”. The new set values of the D / A converters 260a to 260d are calculated so that "

  The contents other than those described above are the same as those in the first embodiment or the second embodiment.

[Fourth Embodiment]
Next, a fourth embodiment will be described. This embodiment is a laser printer 1000 which is an image forming apparatus using the light output control circuit and the light output control method of the semiconductor laser in the first to third embodiments.

  Based on FIG. 7, the laser printer 1000 in this Embodiment is demonstrated. The laser printer 1000 according to this embodiment includes an optical scanning device 1010, a photosensitive drum 1030, a charging charger 1031, a developing roller 1032, a transfer charger 1033, a charge eliminating unit 1034, a cleaning unit 1035, a toner cartridge 1036, a paper feeding roller 1037, a feeding roller. A paper tray 1038, a registration roller pair 1039, a fixing roller 1041, a paper discharge roller 1042, a paper discharge tray 1043, a communication control device 1050, and a printer control device 1060 that comprehensively controls each of the above parts are provided. These are housed in predetermined positions in the printer housing 1044.

  The communication control device 1050 controls bidirectional communication with a host device (for example, a personal computer) via a network or the like.

  The photosensitive drum 1030 is a cylindrical member, and a photosensitive layer is formed on the surface thereof. That is, the surface of the photoconductor drum 1030 is a scanned surface. The photosensitive drum 1030 rotates in the direction indicated by the arrow X.

  The charging charger 1031, the developing roller 1032, the transfer charger 1033, the charge removal unit 1034, and the cleaning unit 1035 are each disposed in the vicinity of the surface of the photosensitive drum 1030. Then, along the rotation direction of the photosensitive drum 1030, the charging charger 1031 → the developing roller 1032 → the transfer charger 1033 → the discharging unit 1034 → the cleaning unit 1035 are arranged in this order.

  The charging charger 1031 uniformly charges the surface of the photosensitive drum 1030.

  The optical scanning device 1010 scans the surface of the photosensitive drum 1030 charged by the charging charger 1031 with a light beam modulated based on image information from the host device, and corresponds to the image information on the surface of the photosensitive drum 1030. A latent image is formed. The latent image formed here moves in the direction of the developing roller 1032 as the photosensitive drum 1030 rotates. The configuration of the optical scanning device 1010 will be described later.

  Toner cartridge 1036 stores toner, and this toner is supplied to developing roller 1032.

  The developing roller 1032 causes the toner supplied from the toner cartridge 1036 to adhere to the latent image formed on the surface of the photosensitive drum 1030 to visualize the image information. Here, the latent image to which the toner is attached (hereinafter also referred to as “toner image” for the sake of convenience) moves in the direction of the transfer charger 1033 as the photosensitive drum 1030 rotates.

  Recording paper 1040 is stored in the paper feed tray 1038. A paper feed roller 1037 is disposed in the vicinity of the paper feed tray 1038. The paper feed roller 1037 takes out the recording paper 1040 one by one from the paper feed tray 1038 and conveys it to the registration roller pair 1039. The registration roller pair 1039 temporarily holds the recording paper 1040 taken out by the paper supply roller 1037, and in the gap between the photosensitive drum 1030 and the transfer charger 1033 according to the rotation of the photosensitive drum 1030. Send it out.

  A voltage having a polarity opposite to that of the toner is applied to the transfer charger 1033 in order to electrically attract the toner on the surface of the photosensitive drum 1030 to the recording paper 1040. With this voltage, the toner image on the surface of the photosensitive drum 1030 is transferred to the recording paper 1040. The recording sheet 1040 transferred here is sent to the fixing roller 1041.

  In the fixing roller 1041, heat and pressure are applied to the recording paper 1040, whereby the toner is fixed on the recording paper 1040. The recording paper 1040 fixed here is sent to the paper discharge tray 1043 via the paper discharge roller 1042 and is sequentially stacked on the paper discharge tray 1043.

  The neutralization unit 1034 neutralizes the surface of the photosensitive drum 1030.

  The cleaning unit 1035 removes the toner remaining on the surface of the photosensitive drum 1030 (residual toner). The surface of the photosensitive drum 1030 from which the residual toner has been removed returns to the position facing the charging charger 1031 again.

  Next, the optical scanning device 1010 will be described with reference to FIG. The optical scanning device 1010 controls a light source unit 1100, a coupling lens and an aperture plate (not shown), a cylindrical lens 1113, a polygon mirror 1114, an fθ lens 1115, a toroidal lens 1116, two mirrors (1117, 1118), and the above-described units. A control device (not shown) for controlling the operation is provided.

  The light source unit 1100 is mounted with any one of the light output control circuits in the first to third embodiments.

  The cylindrical lens 1113 condenses the light output from the light source unit 1100 in the vicinity of the deflection reflection surface of the polygon mirror 1114 via the mirror 1117.

  The polygon mirror 1114 is made of a regular hexagonal columnar member having a low height, and six deflection reflection surfaces are formed on the side surface. Then, it is rotated at a constant angular velocity in the direction indicated by the arrow Y by a rotation mechanism (not shown).

  Accordingly, the light emitted from the light source unit 1100 and condensed near the deflection reflection surface of the polygon mirror 1114 by the cylindrical lens 1113 is deflected at a constant angular velocity by the rotation of the polygon mirror 1114.

  The fθ lens 1115 has an image height proportional to the incident angle of light from the polygon mirror 1114, and moves the image surface of light deflected by the polygon mirror 1114 at a constant angular velocity with constant speed in the main scanning direction. The toroidal lens 1116 forms an image of the light from the fθ lens 1115 on the surface of the photosensitive drum 1030 via the mirror 1118.

  The toroidal lens 1116 is disposed on the optical path of the light beam through the fθ lens 1115. Then, the light beam that has passed through the toroidal lens 1116 is irradiated onto the surface of the photosensitive drum 1030 to form a light spot. This light spot moves in the longitudinal direction of the photosensitive drum 1030 as the polygon mirror 1114 rotates. That is, the photoconductor drum 1030 is scanned. The moving direction of the light spot at this time is the “main scanning direction”. The rotation direction of the photosensitive drum 1030 is the “sub-scanning direction”.

  The optical system arranged on the optical path between the polygon mirror 1114 and the photosensitive drum 1030 is also called a scanning optical system. In this embodiment, the scanning optical system includes an fθ lens 1115 and a toroidal lens 1116. Note that at least one folding mirror may be disposed on at least one of the optical path between the fθ lens 1115 and the toroidal lens 1116 and on the optical path between the toroidal lens 1116 and the photosensitive drum 1030.

  In this case, if the surface emitting laser array LA is arranged as shown in FIG. 9, in the surface emitting laser array LA, the center of each surface emitting laser element (VCSEL) extends in the direction corresponding to the sub-scanning direction. Since the positional relationship of the surface emitting laser elements in the direction corresponding to the sub-scanning direction when the vertical line is lowered is equal (interval d2), the lighting timing is adjusted to adjust the sub-scanning on the photosensitive drum 1030. It can be understood that the configuration is the same as the case where the light sources are arranged at equal intervals in the scanning direction. For example, if the pitch d1 of the surface emitting laser elements in the direction corresponding to the sub-scanning direction is 26.5 μm, the interval d2 is 2.65 μm. If the magnification of the optical system is doubled, writing dots can be formed on the photosensitive drum 1030 at intervals of 5.3 μm in the sub-scanning direction. This corresponds to 4800 dpi (dots / inch). That is, high-density writing of 4800 dpi (dot / inch) can be performed. Of course, higher density can be achieved by increasing the number of surface emitting lasers in the direction corresponding to the main scanning direction, making the array arrangement in which the pitch d1 is reduced and the interval d2 is further reduced, or the magnification of the optical system is reduced. And higher quality printing becomes possible. Note that the writing interval in the main scanning direction can be easily controlled by the lighting timing of the light source.

  Further, in this case, in the laser printer 1000, the surface emitting laser element can generate a high single basic transverse mode output even if the writing dot density increases, so that printing can be performed without reducing the printing speed. it can. Further, when the writing dot density is the same, the printing speed can be further increased.

  In the description of the present embodiment, the case of the laser printer 1000 as the image forming apparatus has been described. However, the present invention is not limited to this.

  For example, an image forming apparatus that directly irradiates laser light onto a medium (for example, paper) that develops color with laser light may be used.

  Further, an image forming apparatus using a silver salt film as the image carrier may be used. In this case, a latent image is formed on the silver salt film by optical scanning, and this latent image can be visualized by a process equivalent to a developing process in a normal silver salt photographic process. Then, it can be transferred to photographic paper by a process equivalent to a printing process in a normal silver salt photographic process. Such an image forming apparatus can be implemented as an optical plate making apparatus or an optical drawing apparatus that draws a CT scan image or the like.

  In this embodiment, since the light output control circuit and the light output control method of the semiconductor laser in the first to third embodiments are used, high contrast and gradation are provided on the surface of the photosensitive drum 1030. An excellent latent image can be formed by scanning. In the optical scanning apparatus 1010 according to this embodiment, the light source unit 1100 can be a surface-emitting laser array or an edge-emitting laser array, or a single-element surface-emitting laser or an edge-emitting laser. .

  Since the optical output device 1010 according to the present embodiment includes any one of the optical output control circuits according to the first to third embodiments, a high-definition latent image with high definition and excellent contrast and gradation can be obtained. It can be formed at high speed. Further, since the laser printer 1000 according to the present embodiment is equipped with any one of the light output control circuits in the first to third embodiments, it is a high-definition and high-quality image excellent in contrast and gradation. Can be formed at high speed.

[Fifth Embodiment]
Next, a fifth embodiment will be described. The fifth embodiment is a color printer 2000 including a plurality of photosensitive drums.

  Based on FIG. 10, the color printer 2000 in this Embodiment is demonstrated. The color printer 2000 in the present embodiment is a tandem multicolor printer that forms a full-color image by superimposing four colors (black, cyan, magenta, and yellow). “Charging device K2, developing device K4, cleaning unit K5, and transfer device K6”, “photosensitive drum C1, charging device C2, developing device C4, cleaning unit C5, and transfer device C6” for cyan, and magenta “Photosensitive drum M1, charging device M2, developing device M4, cleaning unit M5, and transfer device M6” and yellow “photosensitive drum Y1, charging device Y2, developing device Y4, cleaning unit Y5, and transfer device Y6” ”, Optical scanning device 2010, transfer belt 2080, fixing unit 2030, and the like. It is equipped with a.

  Each photosensitive drum rotates in the direction of the arrow shown in FIG. 10, and a charging device, a developing device, a transfer device, and a cleaning unit are arranged around each photosensitive drum in the order of rotation. Each charging device uniformly charges the surface of the corresponding photosensitive drum. The surface of each photoconductive drum charged by the charging device is irradiated with light by the optical scanning device 2010, and a latent image is formed on each photoconductive drum. Then, a toner image is formed on the surface of each photosensitive drum by a corresponding developing device. Further, the toner image of each color is transferred onto the recording paper on the transfer belt 2080 by the corresponding transfer device, and finally the image is fixed on the recording paper by the fixing unit 2030.

  Since the optical scanning device 2010 uses the optical output control circuit and the optical output control method of the semiconductor laser in the first to third embodiments, it is the same as the optical scanning device 1010 described in the fourth embodiment. An effect can be obtained. In addition, since the color printer 2000 includes the optical scanning device 2010, it is possible to obtain the same effect as the laser printer 1000 in the fourth embodiment.

  As mentioned above, although the form which concerns on implementation of this invention was demonstrated, the said content does not limit the content of invention.

DESCRIPTION OF SYMBOLS 100 Drive circuit 101 Surface emitting laser module 101a-101d Surface emitting laser 102 Photodiode 103 Controller 104 Light output control circuit 105 VCSEL drive circuit part 105a-105d VCSEL drive circuit 201 Current-voltage conversion part 202 Integration circuit 203 A / D converter ( A / D converter)
204 Digital operation unit 205 Register 206 D / A converter unit 208 Reference voltage source 210 Amplifier 211 Transimpedance resistor 220 Amplifier 221 Input resistor 222 Capacitor 223 Switch 250a to 250d Register 251a to 251d Register 260a to 260d D / A converter 270 Multiplexer 271 Multiplexer 1000 Laser printer (image forming device)
1010 Optical scanning device 2000 Color printer (image forming apparatus)

JP 2009-1006 A JP-A-2-266964

Claims (11)

A light output control circuit for controlling light emission of a semiconductor laser,
A light receiving element that receives light emitted from the semiconductor laser;
A current-voltage conversion unit that converts a current detected in the light receiving element into a voltage;
An integration circuit for performing a predetermined time integration based on the converted voltage;
An A / D converter for converting the output from the integrating circuit into digital data;
A digital operation unit that performs an operation so that the light amount of the semiconductor laser becomes a predetermined light amount based on the digital data converted in the A / D conversion unit;
A D / A converter for converting an output from the digital operation unit into an analog signal;
Have
A current based on the analog signal flows through the semiconductor laser;
In the integrating circuit, wherein when the light amount of the semiconductor laser is low, the predetermined time is long, wherein when light intensity of the semiconductor laser is high state, and are not the predetermined time has shortened,
Said semiconductor from the laser off of the light output control circuit according to claim to Rukoto constant delay time until the A / D conversion start in the A / D conversion unit. A light output control circuit for controlling light emission of a semiconductor laser,
A light receiving element that receives light emitted from the semiconductor laser;
An integration circuit for performing a predetermined time integration based on the current detected in the light receiving element;
An A / D converter for converting the output from the integrating circuit into digital data;
A digital operation unit that performs an operation so that the light amount of the semiconductor laser becomes a predetermined light amount based on the digital data converted in the A / D conversion unit;
A D / A converter for converting an output from the digital operation unit into an analog signal;
Have
A current based on the analog signal flows through the semiconductor laser;
In the integrating circuit, wherein when the light amount of the semiconductor laser is low, the predetermined time is long, wherein when light intensity of the semiconductor laser is high state, and are not the predetermined time has shortened,
Said semiconductor from the laser off of the light output control circuit according to claim to Rukoto constant delay time until the A / D conversion start in the A / D conversion unit.   3. The light output control circuit according to claim 1, wherein a value integrated for a predetermined time in the integration circuit is substantially constant. 4.   4. The optical output control circuit according to claim 1, wherein a delay time from when the semiconductor laser is turned off to when it is converted into digital data in the A / D converter is substantially constant. 5.   5. The output from the integration circuit is reset after a predetermined time has elapsed after the conversion to digital data in the A / D conversion unit is started. 6. Light output control circuit.   5. The light output control circuit according to claim 1, wherein in the integration circuit, the output is continuously reset except for a time for light output control.   The light output control circuit according to claim 1, wherein the A / D converter is an A / D converter.   The light output control circuit according to claim 1, wherein the A / D conversion unit includes one or more comparators. An optical scanning device that scans a surface to be scanned with light,
A light source comprising the light output control circuit according to claim 1;
A light deflector for deflecting light from the light source;
A scanning optical system for condensing the light deflected by the light deflection unit on the surface to be scanned;
An optical scanning device comprising: An image carrier;
The optical scanning device according to claim 9, which scans the image carrier with light modulated according to image information;
An image forming apparatus comprising:   The image forming apparatus according to claim 10, wherein there are a plurality of image carriers, and the image information is multicolor color information.

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