JP3239315B2 - Multi-beam optical scanning device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical scanning device used for a laser printer, a digital copy, and the like, and more particularly, to a multi-beam type optical device which realizes high-speed and high-resolution optical scanning using a plurality of beams. It relates to a scanning device.

[0002]

2. Description of the Related Art Conventionally, an optical scanning device (laser scanner) used for a laser printer scans a recording member such as a photosensitive drum using a single beam.
A polygon mirror (rotating polygon mirror) that rotates at high speed is used as a beam scanning unit. Further, in recent years, there has been a demand for high-speed, high-resolution, color, and high-quality optical scanning devices. Therefore, a multi-laser scanner that forms an image by simultaneously optically scanning a plurality of beams has been proposed. .

FIG. 16 shows a configuration example of an optical unit of a conventional multi-beam laser scanner. Here, a laser printer that forms an image on the photosensitive drum 106 is shown. LD1 and LD2 (101) are laser diodes (hereinafter also referred to as LDs) serving as light sources, and two beams are emitted to the polygon mirror 102 at the same time. The polygon mirror 102 is a mirror that rotates several thousand times per minute, and is a mirror for oscillating beams emitted from LD1 and LD2 in the vertical direction on the paper surface. The Fθ lens is a correcting lens for correcting the laser scanning speed on the photosensitive drum surface 106 so as to be constant.

A mirror 104 is generally fixed and is a mirror for reflecting a beam in the direction of the photosensitive drum. The BD detection unit 105 is a sensor (photodiode) that detects a reference position for printing and writing. LD1 and L
The beam emitted from D2 is polarized by the polygon mirror 102 and passes through the Fθ lens. Further, the mirror 104
The image is formed on the photosensitive drum by scanning on the surface of the photosensitive drum 106 after being reflected by the light.

FIG. 17 is a diagram for explaining the beam scanning order. FIG. 17A shows a scanning beam (single beam) when only one light source is provided.
The beams are scanned one by one in the order of 2, a3. FIG.
(B) is a scanning beam (multi-beam) when the two light sources shown in FIG. 16 are provided, and after b11 and b12 are simultaneously scanned, b21 and b22 are simultaneously scanned.
Further, operations such as emission / stop of the beams from the LD1 and LD2, rotation control of the polygon mirror 102, detection and control of the scanning position by the BD detection unit 105 are controlled by a controller (not shown).

FIG. 18 shows a configuration example of a conventional light source for generating a multi-beam. The light source 110 fixes two beam generating sources 111 corresponding to the laser diodes LD1 and LD2 in FIG. 16 to flanges 112 that are insulated from each other. It is fixed to 113 by screwing.

Each flange is covered with an insulating film such as alumite. FIG. 19 shows a schematic block diagram of a driving portion of a conventional laser diode (LD). The controller 121 includes a laser diode LD1,
The print signals A and B for driving the LDs 2 (123, 125) are generated. The print signals A and B are pulse signals as LD drive circuits A and B (122, 1
24). FIG. 20 shows a circuit example of the conventional LD drive circuits A and B shown in FIG. Here, when the print signal A or B is input as a pulse signal to the transistors TR101 and TR102, a drive current flows to LD1 or LD2, and beam 1 or beam 2 is output.

[0008]

However, in the conventional light source shown in FIG. 18, LD1 and LD2 are electrically insulated, but since each flange is covered with an insulating film, there is a gap between the flanges. There is a capacitor capacity (floating capacity). For example, as shown in FIG. 20, when the stray capacitance C exists and the drive current of the LD1 flows at the point p, it affects the drive current of the other LD2 at the point q.

FIG. 21 illustrates this effect. When the drive pulse is generated at the point p in FIG. 20 while the drive pulse is generated at the point p in FIG. 20, the overshoot of the rising edge of the pulse at the point q affects the pulse waveform at the point p. Exert. This effect becomes noise and causes ghosts in the image output by beam 1. Similarly, the rise of the drive waveform of the LD1 may affect the drive waveform of the LD2, and in any case, it causes a deterioration in print quality.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above circumstances, and has as its object to prevent the occurrence of ghost in a multi-beam optical scanning device and improve the printing quality. It is another object of the present invention to provide a multi-beam optical scanning device at low cost while utilizing a controller used in a conventional single-beam optical scanning device.

[0011]

SUMMARY OF THE INVENTION The present invention provides a plurality of beam generating sources for generating a plurality of beams, a plurality of beam driving units for providing a driving signal for generating the beams to the beam generating sources, and a beam scanning unit. A reference position detection unit that detects each beam at a reference position to start the detection and generates a detection signal corresponding to each beam, and is synchronized with a synchronization clock based on the detection signal generated by the reference position detection unit. A print data generation unit that generates print data, a print data storage unit that separates and stores print data output from the print data generation unit for each beam, and a print data storage unit that stores the print data stored for each beam. And a control unit for giving a beam drive unit corresponding to the above at a timing determined by the detection signal. A.

Further, according to the present invention, the reference position detecting section is constituted by a single photo sensor, and a detection signal for separating a detection signal corresponding to each beam from a plurality of detection signals detected by the single photo sensor. A separation unit may be further provided. Further, the apparatus may further include a detection signal delay unit that corrects a deviation of a relative time interval between the detection signals of each beam separated by the detection signal separation unit to match a predetermined reference interval.

The plurality of beam generating sources may be constituted by laser diodes, respectively, and may be a multi-beam optical scanning device in which each laser diode is connected to a common ground terminal. A multi-beam optical scanning device connected to the power supply terminal of the first embodiment may be used.

Further, according to the present invention, the beam drive unit includes a subtraction unit that subtracts two signals, and an edge signal generation unit that detects a rising edge of the given print data and generates an edge signal. A subtraction unit of an arbitrary beam driving unit A subtracts print data given to the beam driving unit A from an edge signal generated by an edge signal generation unit of another arbitrary beam driving unit B, and performs beam driving. An object of the present invention is to provide a multi-beam optical scanning device that generates a drive signal for generating a beam corresponding to the section A.

Here, the beam generating source may be any one that can generate a laser beam, and for example, a laser diode can be used. Alternatively, a gas laser may be used. The beam driving unit is a circuit for driving a laser diode that generates a beam,
It is composed of switching elements such as transistors.
The reference position detector is a so-called photodetector, and it is preferable to use a photodiode in terms of its performance. In addition, it is preferable to use one photodiode due to its configuration.

By irradiating the photodiode with a beam, a detection signal is output from the photodiode. Since the beam is scanned by the rotating mirror, the detection signal is output as a pulse signal. In general, this detection signal is referred to as a BD signal (Beam, Det).
ect), and the reference position detection unit is also referred to as a BD detection unit. The BD signal is generated every time each beam is irradiated on the photodiode. However, since each beam is emitted at a predetermined timing, it is output as a discrete and continuous pulse signal.

The detection signal separation section is for separating the BD signal corresponding to each beam from the continuous pulse signal, and is configured as a BD signal separation circuit in which a timer and a logic element are combined. The print data generation unit may use the data used in the conventional single-beam type optical scanning device. Hereinafter, the print data generation unit is referred to as a controller.

As the print data storage unit 12, a RAM or the like is used, but it is preferable that the print data storage unit 12 is separated into two buffers (A, B) in order to speed up printing. Each buffer (A, B) is preferably divided into a memory area for storing print data for generating each beam for each beam. Then, the print data corresponding to the first beam is alternately written to the first beam memory areas in the buffers A and B by the control unit, and is alternately read. Further, since the print data given from the controller is generally serial data, it is preferable that the print data is converted into parallel data by a serial-parallel conversion circuit before being stored.

The control unit is a memory control unit that controls reading and writing of the buffers A and B, and can be generally configured by a logic circuit such as a counter. The detection signal delay unit is configured by a delay circuit that changes the output timing of the detection signal by using a delay element such as an LC integration circuit. The subtraction unit can be easily configured by combining logic elements such as an operational amplifier, for example, and the edge signal generation unit can be configured by a delay element.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on an embodiment shown in the drawings. Note that the present invention is not limited to this. FIG. 1 is a block diagram showing a laser diode driving portion of a multi-beam optical scanning device according to the present invention. Here, an embodiment using two laser diodes will be described.

In FIG. 1, a controller 1, LD driver circuits (5a, 5b), LD1 (6a), LD2 (6
a) As the BD detection unit 7, the same one as the conventionally used one shown in FIG. 16 and FIG. 19 can be used. As the controller 1, the same controller as used when optical scanning is performed using a single beam is used. Therefore, the controller 1 outputs a continuous serial video signal (hereinafter also referred to as a print signal) used for performing optical scanning with a single beam, together with the synchronous clock signal.

In this embodiment, the following specific constituent blocks convert single beam serial data into parallel data for generating two beams, and emit two beams at a predetermined timing. It is characterized in that two laser diodes are driven.
The serial-parallel conversion circuit 2 is a circuit that converts a serial print signal sent from the controller 1 into parallel data.

The buffer A (3) and the buffer B (4)
A memory for storing the converted parallel data, and usually a RAM is used. The memory 1 of the buffer A (3) and the memory 1 of the buffer B (4) store parallel data for the LD 1 (6a), and the buffer A (3)
And the memory 2 of the buffer B (4) are LD2
This stores parallel data for (6b). For example, memory 1 of buffer A (3) and buffer B
By alternately reading the data of the memory 1 of (4), a drive signal for causing the LD 1 (6a) to emit a beam is created. The details will be described later.

The LD driving circuits 5a and 5b cause the laser diodes LD1 (6a) and LD2 (6b) to emit light. For this purpose, a circuit similar to the conventional one can be used. In order to prevent a ghost at the time of printing caused by driving the diodes simultaneously, it is preferable to adopt a circuit configuration as described later. Reference numerals 13a, 13b, 14a, and 14b are OR circuits.
One photodiode is used for the BD detection unit 7 as in the related art.

The BD signal separating circuit 8 converts a plurality of BD signals obtained by the BD detecting section 7 into B signals for each laser diode.
D signals (BD1, BD2) are separated. BD
If the detection unit 7 is provided separately for each laser diode, it is not necessary to provide such a separation circuit. However, it is difficult to provide a plurality of BD detection units due to the configuration of the optical scanning device. Advanced maintenance such as is required, leading to an increase in cost. Therefore, as described later,
The D signal separation circuit 8 can be easily configured by a timer and several logic elements.
The D detection unit 7 and the BD signal separation circuit 8 will be used. This allows a simple circuit configuration for detection and separation of the BD signal.

The delay circuits 11a and 11b
This is a circuit for correcting a timing deviation of the D signals (BD1, BD2). Since the BD signals BD1 and BD2 have a timing deviation due to a mounting error of the light source or a difference in the power of the laser diode, unless this is corrected,
This causes a displacement of the printing dots and causes deterioration of printing quality.
Therefore, it is necessary to correct the timing shift by the delay circuits 11a and 11b. BD1 ′ and BD2 ′ are BD signals after this correction.

The pseudo BD generation circuit 9 generates a pseudo BD signal which is a reference of the timing of the print signal output from the controller 1. When two beams are used, the writing speed is halved, so that the BD signal separated by the BD separation circuit 8 appears twice as long as the period for emitting each beam. Therefore, since the separated BD signal cannot be directly supplied to the controller 1, the pseudo BD signal is generated at the timing of 周期 cycle of the BD signal and is supplied to the controller 1. A generation circuit 9.

In general, when scanning is performed using n beams, the pseudo BD generation circuit 9 uses the separated BDs.
It is configured to generate a pseudo BD signal having a period obtained by equally dividing the signal by the number n of beams. This pseudo BD generation circuit 9
Can be realized, for example, by combining circuit elements such as a counter.

The memory control circuit 10 is a circuit for controlling the reading and writing of each of the buffers A (3) and B (4). Where, for example,
When generating a drive signal for LD1 (6a),
When the memory 1 of the buffer A (3) is at the timing of writing, the memory control circuit 10 determines that the memory 1 of the buffer B (4) is at the timing of reading and the buffer A (3)
When the memory 1 of the buffer B is at the timing of reading, the memory of the buffer B (4) is at the timing of writing.
Control each memory.

The memory control circuit 10 is realized by a circuit element such as a counter, for example. The memory control circuit 10 and each memory in the buffer are connected by a chip select (CS), a read / write (R / W), and a control signal line of an address line. The laser emission timing creation circuits 12a and 12b are provided with delay circuits 11a and 11b.
A timing signal (VD01, VD02) for emitting a beam is created based on the BD signal output from b, and can be realized by a circuit element such as a counter and a gate, for example.

The interval between one BD signal and the next BD signal is
Since one scanning period in the horizontal direction is shown, the timing signal is output for a predetermined time within a period between a certain BD signal and the next BD signal. For example, if one horizontal scanning period is 6
At 40 μsec, the timing signal is 100 μsec.
About c is output. In addition, the timing signal (V) generated by the laser emission timing generation circuits 12a and 12b.
D01, VD02) are input to the OR circuits 14a and 14b for generating a drive signal for each laser diode.

Next, the outline of the operation of the laser diode driving portion of the present invention will be described with reference to FIGS. Here, an embodiment in which scanning is performed by two beams will be described. FIG. 4 shows an embodiment of a time chart for reading / writing to / from a memory in a buffer according to the present invention. First, a print signal synchronized with the synchronization clock is sent from the controller 1 to the serial-parallel conversion circuit 2. The synchronous clock used at this time is a pseudo BD signal generated by the pseudo BD generation circuit 9 and is a signal indicating the start of scanning for each laser diode. As described above, in FIG. 4, the BD signal BD1 'input to the pseudo BD generation circuit 9 has a period twice as long as the period for emitting two beams. Therefore, in the pseudo BD generation circuit 9, the BD
The BD shown in FIG.
A pulse signal corresponding to 1 ″ is generated and given to the controller 1 as a pseudo BD signal as shown in FIG.

The controller 1 adopts the pseudo BD signal as a synchronous clock, and synchronizes with the print signal (w
1 to w4). The serial-parallel conversion circuit 2 takes in a serial print signal for each laser diode on the basis of a synchronous clock, and outputs the print signal as parallel data of, for example, 8 bits to the memory of the buffer A (3).

Two laser diodes (LD1, LD
When using 2), the parallel print data (w1) for the laser diode LD1 is written into the memory 1, and the parallel print data (w2) for the laser diode LD2 is written.
Is written to the memory 2. The writing of data from the serial-parallel conversion circuit 2 to the buffer A (3) is controlled by the memory control circuit 10 using read / write lines, chip select lines, and address lines.

After the parallel print data (w1, w2) for one scan is written into the memory 1 and the memory 2 of the buffer A, these are read out by the memory control circuit 10 (r1, r2). Further, the read data (r1, r2) is stored in the laser emission timing creation circuit 1
At the timing created in 2a and 12b, the OR circuit 14
a and 14b and output to the LD drive circuits 5a and 5b.

After that, the LD driving circuits 5a and 5b operate the laser diodes LD1 and LD2 at the given timing.
To emit a beam for one scan. Buffer A
When reading parallel print data from (3), (r
1, r2), new next print data (w3, w4) is written from the serial-parallel conversion circuit 2 to the buffer B (4). When reading out the print data written in the memory of the buffer B (4),
Writing of new print data to (3) is performed. The memory control circuit 10 controls such alternate writing and reading to and from the buffer A (3) and the buffer B (4).

As described above, since two sets of buffers A and B are provided to alternately read and write print data, high-speed printing performed by driving two laser diodes can be stabilized. It is. Also, by adopting the configuration as shown in FIG. 1, the controller 1, the LD drive circuits 5a and 5b, and the BD detection unit 7 can use the one of the conventional single beam type optical scanning device. The transmission control of the print data in the controller 1 does not need to perform the control unique to the multi-beam type.
Since the same control as that of the conventional single beam type may be performed, the load on the controller does not increase.

Hereinafter, embodiments of the serial-parallel conversion circuit 2, the LD drive circuits 5a and 5b, the BD separation circuit 8, and the delay circuits 11a and 11b, which are features of the configuration of the multi-beam type optical scanning device of the present invention. Will be described.

Embodiment 1 FIG. 2 shows an embodiment of a serial-parallel conversion circuit. Where the registers Reg 1 and
Reg 2 (21, 22) converts serial data into parallel data. MEM23 is buffer A
Or, a memory in B for storing the converted parallel data. 24 is an inverting circuit, and 25 is a frequency dividing circuit. The frequency dividing circuit 25 doubles the period of the synchronous clock provided from the controller 1.

The MEM 23 is connected to the memory control circuit 10 shown in FIG. 1 by an R / W line, a CS (chip select) line, and an address line in the same manner as in ordinary memory control. The registers Reg1, Reg2 and the MEM 23 are connected by, for example, an 8-bit bus line.

FIG. 3 shows a time chart of the serial-parallel conversion circuit. The print data is 1-bit serial-parallel data, and is input to the register Reg 1 (21) or Reg 2 (22) in synchronization with the synchronous clock. Here, when high-speed and high-resolution printing is required, writing serial data to a register requires one step.
A very high-speed synchronous clock of several ns is required.

Therefore, a video clock (CL) having a cycle twice as long as the synchronous clock (CLK) is generated by the frequency dividing circuit 25.
K × 2), and print data is registered at the rising and falling timings of the video clock by Reg 1 (21) and R
eg 2 (22). For example,
The print data “1” in FIG. 3 is taken into Reg 1 at the rise of the video clock, and the print data “2” is taken into Reg 2 at the fall of the video clock.

Further, the print data alternately loaded into Reg 1 and Reg 2 is written into the MEM 23 by the memory control circuit outputting a write signal. Thus, high-speed and high-resolution printing can be supported by alternately taking serial print data into the registers (Reg1, Reg2) and writing them as parallel data in the memory MEM23. In addition, by adopting the above-described configuration, it is possible to use a high-speed synchronous clock as it is and to prevent a synchronization deviation due to a delay of a circuit element that may occur when converting to parallel data, thereby achieving stable print data. Is possible.

Embodiment 2: Here, a multi-beam type L
An embodiment of the D drive circuits 5a and 5b will be described. FIG.
FIG. 1 shows a schematic block diagram of a laser diode driving portion in one embodiment of the present invention. Here, it is assumed that two laser diodes (LD1, LD2) that generate beams are used. The light source is an LD, as shown in FIG.
1. Assume that the LD 2 is mounted on a flange, and the flange is covered with an insulating film, and is fixed at a predetermined interval to an aluminum block housing.

In FIG. 5, an LD1 driving section 41 receives a print signal A given from a controller and generates a signal for driving the laser diode LD1. Similarly, the print signal B is input to the LD2 drive unit 42,
A signal for driving the laser diode LD2 is generated. L
The D1 drive unit 41 and the LD2 drive unit 42 include an edge signal generation unit (43a, 43b) and a subtraction unit (44a, 44b) to remove noise components that affect each other. The edge signal generators (43a, 43b) detect the rise of the print signal and generate a pulse signal indicating the rise, and this pulse signal is input to the other subtractor. The pulse signal input to the other subtractor is used to cancel noise components as shown in FIG.

FIG. 6 is a schematic diagram of the signal waveform of each part in FIG. In FIG. 6, since a capacitor capacitance is formed between the flanges as shown in the conventional example, a noise component n1 is generated in the print signal A in the LD drive unit 41, resulting in a drive waveform c. On the other hand, the edge signal generator 43b detects the rising edge of the print signal B and generates an edge signal waveform f as shown in FIG. The subtraction unit 44a subtracts the edge signal waveform f from the drive waveform c to generate the LD signal.
One drive waveform g is generated. In this way, a drive waveform without noise is obtained as a drive waveform in the LD 1, and as a result, ghost can be prevented from occurring.

Similarly, the noise component n2 is added to the print signal B.
Is generated, the noise component is removed from the driving waveform e on which the noise is superimposed by the subtraction unit 44b using the edge signal waveform d generated by the edge signal generation unit 43a.
As described above, by providing the edge signal generating section and the subtracting section in the respective laser diode driving sections of the LD1 and LD2, it is possible to remove noise components generated by the capacitor formed in the configuration and affecting each other. it can.

FIG. 7 shows a laser diode (L) of the present invention.
7 shows a detailed configuration example of an embodiment of the driving portion of D). Here, LD1 and LD2 are laser diodes, and PD1 and PD2 are diodes for controlling the current flowing through the laser diodes. TR1 and TR2 control the current flowing through LD1 by print signal A or B.
It is an n-type transistor. The amplifier 51 and the power control unit 52 are for making the light emission intensity of the laser constant.

The NOT circuit 53, the delay circuit 54, the AND circuit 55, and the transistors TR2 and TR4 detect a rising edge of the print signal and generate a pulse signal, and the pulse signal is generated by the edge signal generators (43a and 43b). Equivalent to. The collector terminals of TR2 and TR4 are connected to the emitter terminals of TR1 and TR3 via resistors R10 and R5, respectively. Thus, TR1 and TR4,
By connecting TR2 and TR3, the subtraction sections (44a, 44b) described above are configured.

The resistance values of the resistors R1 to R10 are, for example, R1, R6 = 5 to 30Ω, R2, R7 = 1.
00-1KΩ, R3, R8 = 100Ω, R4, R9 = 1
00Ω, R5, R10 = 10 to 100Ω can be used. Further, the power supply voltage V supplied to LD1 and LD2 is preferably in the range of +5 to + 24V, for example, + 24V.

Points c, d, e, f, g, and h in FIG. 5 correspond to points c, d, e, f, g, and h in FIG. 7, and the signal waveform at each point is shown in FIG. It will be.
That is, even if noise n1 occurs in the drive signal waveform at the point c, the edge signal waveform f is added to TR1, so that the laser diode LD1 has a waveform of g (= cf) in which the noise n1 is canceled. A pulse is applied.

Similarly, even if noise n2 occurs in the drive signal waveform at point e, the edge signal waveform d is added to TR2, so that the laser diode LD2 has the noise n
A pulse having a waveform of h (= ed) in which 2 is canceled is applied. Therefore, since drive signals that do not include noise components corresponding to the print signals A and B are applied to the LD1 and LD2, it is possible to prevent the occurrence of ghost in printing.

In the embodiment shown in FIG. 7, LD1 and PD1,
In addition, the configuration in which the power supply terminal (+ V) of the LD2 and the PD2 is made common is shown. In addition, as shown in FIG.
The ground terminals (GN) of LD1 and PD1, and LD2 and PD2
A configuration of the type that shares D) may be used.

FIG. 8 shows another embodiment of the circuit near LD1 and LD2 in FIG.
In order to drive D1 and PD2, a negative power supply (-V
= −50 V to −24 V), and transistors TR1 and TR2 for driving LD1 and LD2.
And resistors R1 'and R3' on the power supply terminal (+ V) side.

Also in the embodiment shown in FIG. 8, the pulses applied to LD1 and LD2 have the driving waveforms g and h shown in FIG. 6, and the noise component can be removed. Therefore, the print signals A and B are supplied to the drive unit of the laser diode.
Edge signal generator (4)
3a, 43b) and a subtractor (44a, 4b) for canceling the noise component affecting the other by the edge signal generated by the edge signal generator at the rise of the pulse. Noise components can be removed from the laser diode drive signal to prevent ghosting during printing.

In order to remove the above-mentioned noise components, coils (LD1, LD2) may be inserted between the power supply voltage + V and LD1 and LD2 as shown in FIG. With these coils (L1, L2),
A sharp change in the drive waveform of the laser diode can be prevented, and therefore, noise components can be removed. In addition,
The inductor value of the coil may be, for example, about 10 μH.

Also, as shown in FIG. 10A, by providing a plurality of transistors, it is possible to prevent a sharp change in the drive waveform of the laser diode. FIG. 10B shows a current waveform flowing through the three transistors TA, TB, and TC shown in FIG. 10A and a current waveform flowing through the laser diode. Here, the timing at which the laser diode is driven by the three transistors TA, TB, and TC is divided into three stages to make the rising and falling of the current waveform flowing through the laser diode gentle. This makes it possible to reduce the influence of a sharp change in the laser diode drive waveform on the other drive waveform. It should be noted that in order to make the drive timing shift as shown in FIG. 10B, three transistors TA, TB,
Among the TC characteristics, the current amplification factor (hfe) may be kept constant.

In the above, there has been described the embodiment in which the ghost is prevented by removing the noise component generated when the light source composed of the two beam sources is constituted by one aluminum block case. However, the noise components can be removed even if the two beam generation sources are configured as separate housings and fixed to a plastic frame plate at predetermined intervals. FIG. 11 shows an embodiment in which the two beam sources are configured as separate block housings. FIG.
1 (a) is a plan view, (b) is a front view, and (c) is a side view. The two aluminum block housings shown
A flange incorporating a laser diode (LD1 or LD2) is attached.

The aluminum block housings 1 and 2 are provided with a concave portion at the lower portion, and a frame plate having a convex portion B for engaging with the concave portion and a convex portion A for stabilizing the aluminum block. It is attached. Here, the projection A is trapezoidal when viewed from above so that the optical axis of the beam emitted from the laser diode forms a predetermined angle, and an aluminum block is fixed along the side surface of the trapezoid. It is preferred that this be done. Here, as the material of the frame plate, it is necessary to use a material that does not cause a floating capacitance between the two aluminum blocks.

For this purpose, for example, as a frame,
It is preferable to use a material having no conductivity such as a plastic material. As the material of the block housing for fixing the flange, aluminum is most preferably used in terms of molding, but a plastic material may be used. In this way, the two beam emission sources are provided in separate block housings,
Further, by fixing this to a plastic frame, it is possible to suppress noise components generated in the laser diode drive signal.

Embodiment 3 Next, an embodiment of the BD separation circuit 8 of the present invention will be described. FIG. 12 shows the BD detection unit 7
An example of a BD separation circuit 8 that separates and extracts three BD signals (SIG5, SIG6, and SIG7) from a BD signal (SIG1) given from the first embodiment. As shown in the figure, this circuit includes two timers 61 and 62 (TIMER1, T
IMER2) and some logic elements.

FIG. 13 shows a time chart of the separation of the BD signal. In this embodiment, an optical scanning device having three laser diodes is considered. At this time, the three beams are detected by one BD detection unit, so that the BD detection unit 7
A signal is generated. Since the three beams have different timings for irradiating the BD detection unit 7, the BD signals generated by the respective beams are superimposed and output as time-shifted pulse signals. It is a signal (S1, S2, S3) like SIG1.

The timers 61 and 62 are used to generate timings for separating the respective signals. The set time of the timings is determined by the mounting position of the laser diode, the angle, the distance between other components, and the like. Should be determined by the following conditions. For example, SIG1
Assuming that the period from S1 to S2 is about 15 μsec, the set time counted by the timers 61 and 62 is preferably about 20 μsec. here,
The timers 61 and 62 are of the re-trigger type.

Hereinafter, the time chart of FIG. 13 will be described. First, the signal SIG input to the BD signal separation circuit 8
The timer 61 is activated at the falling edge of the first BD signal (S1). At this time, the signal SIG2 is output from the timer 61.
Is output for a fixed time T. Here, the certain time is a time set in advance, and is set to a time longer than the time when the next BD signal (S2) will come.

Since the timer 61 is also triggered by the following signals S2 and S3, the output of the timer 61 is changed after the signal S1 is input as shown by SIG2 in FIG.
It is continuously output until after 3 is input. SIG3
Is the logical product of SIG1 and SIG2, and is obtained by removing the signal S1 from SIG1 as shown in the figure. The timer 62 is operated at the fall of SIG3. Since the timer 62 is also of the retrigger type, the output of the timer 62 is SIG4 in FIG.

Using the above SIG1 to SIG4, 3
BD for each laser diode
The signals (S1, S2, S3) are extracted. That is, BD
SIG5 corresponding to the signal S3 can be taken out by the logical product of SIG3 and SIG4. Also, the BD signal S2
Are SIG2, SIG3, and SIG
Can be extracted by the logical product of negation of 4 and BD
SIG7 corresponding to signal S3 includes SIG1 and SIG2
Can be taken out by the logical AND with the negation of

As described above, the BD signal detected by a plurality of beams is output as a superposed pulse signal from the BD detection unit, and each of the beams is easily output by the BD signal separation circuit as shown in FIG. BD corresponding to
The signal can be separated. Also, in the present invention using a plurality of beams, the BD detection unit 7 can be constituted by one photodiode, so that the same configuration as in the case of using a conventional single beam can be adopted.

Therefore, the BD detector and the B
By providing the D signal separation circuit, the circuit configuration of the BD detection portion of the multi-beam optical scanning device can be simplified. Although the example of the BD signal separation circuit in the case of using three laser beams has been described above, the BD signal separation circuit is also provided with a timer and a logic element when two or four or more laser beams are used. Can be configured by

Embodiment 4 Next, an embodiment of the delay circuits (11a, 11b) in the embodiment of FIG. 1 of the present invention will be described. Therefore, this is an example of a delay circuit in the case of an optical scanning device using two laser beams. According to the present invention, as described above, a plurality of beams are detected by one BD detection unit, and the BD
Signals are separated by a BD signal separation circuit. When two beams are used, two BD signals (BD1 and BD2) are detected by being superimposed. The two BD signals are detected as signals shifted by a predetermined time by the BD signal separation circuit. For example, as shown in FIG.
D2 is detected at a time interval T apart.

However, this actually detected time interval T
Is often different from the time interval Ts (see FIG. 14) scheduled at the time of design due to an error in the mounting position of the BD detection unit in the optical scanning device of the present invention or a difference in beam power. The delay circuit described below is for correcting such a timing shift of the BD signal.

FIG. 15 shows a delay circuit (11a,
11b) shows an example. In the figure, DELAY
Reference numerals 71 and 72 denote delay elements, which can be configured using, for example, an LC integration circuit. The output signal of this DELAY is
1 ′ and BD2 ′. SR flip-flop 73
The counter 74 generates a timing for counting, which is set by the input of BD1 'and BD2'
Is reset by the input of.

The counter CNT 74 has BD1 ′ and BD1 ′.
The time interval T with 2 'is counted. The reference value setting circuit 76 includes a BD signal BD
A count value (reference value) corresponding to the time interval Ts between 1 and BD2 is generated. Comparator CMP75
Is to compare the actual count value of the time interval T by the counter CNT74 with the reference value of the time interval Ts at the time of design and output the difference.

The output value of the comparator CMP75 is DE
The output timing is fed back to the LAYs 71 and 72, and the output timing of the BD1 and the BD2 is adjusted by the DELAY based on the output value. For example, when the time interval T between BD1 and BD2 is narrower than the reference value, the output timing of BD2 is slightly delayed by the DELAY 72 so that the time interval Ts is adjusted, and output as BD2 '. Note that BD1 'and BD2' correspond to the outputs of the delay circuits 11a and 11b in FIG.

As described above, the timing shift of the BD signal is automatically corrected by the delay circuit while comparing it with the reference value of the output timing of the BD signal. It is possible to prevent dot displacement. In addition, since the automatic correction is performed by the feedback as described above, the stable performance as the optical scanning device can be maintained even with environmental changes such as temperature changes.

The delay time of the DELAYs 71 and 72 may be adjusted by switching with a dip switch. In this case, it is necessary for the user to prepare some set times at the time of design and set them before use, but there is an advantage that the circuit can be rationalized.

As described above, the configuration and functions of the optical scanning device using two beams are mainly described as the multi-beam type optical scanning device of the present invention, but the same applies to the optical scanning device using three or more beams. By adopting the configuration described above, it is possible to provide a multi-beam type optical scanning device which prevents generation of noise which causes ghost and has stable performance against environmental changes.

[0077]

According to the present invention, print data is stored separately for each beam, and the print data is supplied to the beam drive unit at a timing based on the detection signal detected by the reference position detection unit. Therefore, it is possible to provide a multi-beam optical scanning device capable of preventing occurrence of ghost and improving printing quality.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a laser diode (LD) driving portion of a multi-beam optical scanning device according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration of a serial-parallel conversion circuit according to an embodiment of the present invention;

FIG. 3 is a time chart of the serial-parallel conversion circuit of the present invention.

FIG. 4 is an embodiment of a time chart for reading from and writing to a memory in a buffer according to the present invention;

FIG. 5 is a schematic block diagram of an LD driving portion according to an embodiment of the present invention.

6 is an explanatory diagram of a drive signal waveform in each part of FIG.

FIG. 7 is a detailed configuration block diagram of an LD driving portion according to an embodiment of the present invention.

FIG. 8 is a configuration diagram of another embodiment near the LD in FIG. 7;

FIG. 9 is a configuration diagram of another embodiment in the vicinity of the LD in FIG. 7;

FIG. 10 is a configuration diagram of another embodiment near the LD in FIG. 7;

FIG. 11 shows an embodiment in which two beam sources are configured as separate housings in the present invention.

FIG. 12 is a configuration block diagram of an embodiment of a BD separation circuit according to the present invention.

FIG. 13 is a time chart of a separating operation of the BD separating circuit of the present invention.

FIG. 14 is an explanatory diagram of a BD signal detection timing in the present invention.

FIG. 15 is a block diagram showing a configuration of a delay circuit according to an embodiment of the present invention;

FIG. 16 is a configuration diagram of a conventional optical unit.

FIG. 17 is an explanatory diagram of scanning of a single beam and a multi-beam.

FIG. 18 is a configuration diagram of a conventional light source that generates a multi-beam.

FIG. 19 is a configuration block diagram of a conventional laser diode (LD) driving portion.

FIG. 20 is a configuration diagram of a conventional LD drive circuit (A, B).

FIG. 21 is an explanatory diagram of a driving waveform of a conventional LD.

[Explanation of symbols]

 1. Controller 2. 2. Serial-parallel conversion circuit Buffer A 4. Buffer B 5a. , 5b. LD drive circuit 6a. , 6b. Laser diode 7. BD detection section 8. 8. BD separation circuit 10. Pseudo BD generation circuit Memory control circuit 11a. , 11b. Delay circuit 12a. , 12b. Laser generation timing creation circuit

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yoshitaka Murakawa 1015 Uedanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture Inside Fujitsu Limited (72) Inventor Tatsuya 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture Fujitsu Limited ( 72) Inventor Yasuo Numata 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture Inside Fujitsu Limited (72) Inventor Kazuki Ogawa 1015 Kamidadanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture Inside Fujitsu Limited (72) Inventor Bunmei Seto Kanagawa prefecture, Nakahara-ku, Kawasaki, Kamikodanaka 1015 address Fujitsu within Co., Ltd. (56) reference Patent flat 6-255181 (JP, a) (58 ) investigated the field (Int.Cl. ^7, DB name) B41J 2/44 H04N 1/036

Claims (5)

(57) [Claims] A plurality of beam generating sources for generating a plurality of beams; a plurality of beam driving units for providing a driving signal for generating the beams to the beam generating sources; and a reference position for starting beam scanning. A reference position detection unit that detects each beam and generates a detection signal corresponding to each beam; and a print data generation unit that generates print data synchronized with a synchronization clock based on the detection signal generated by the reference position detection unit. A print data storage unit that separates and stores the print data output from the print data generation unit for each beam; and stores the print data stored for each beam in a beam drive unit corresponding to that beam. Ri Do and a control unit to provide at a timing determined by the detection signal, the beam driving unit, subtracting unit for performing subtraction of the two signals
And the rising edge of the given print data
And an edge signal generation unit for generating a signal. The subtraction unit of the arbitrary beam driving unit A is
Of the print data given to the
Subtraction with the edge signal generated by the edge signal generator
To generate a beam corresponding to the beam driving unit A
Multi-beam type characterized by generating a drive signal of
Optical scanning device. 2. The apparatus according to claim 1, wherein the reference position detection unit includes a single photosensor, and further includes a detection signal separation unit configured to separate a detection signal corresponding to each beam from a plurality of detection signals detected by the single photosensor. The multi-beam optical scanning device according to claim 1, further comprising: 3. The apparatus according to claim 1, further comprising a detection signal delay unit that corrects a relative time interval shift between the detection signals of the respective beams separated by the detection signal separation unit to match a predetermined reference interval. 3. The multi-beam optical scanning device according to claim 2, wherein: 4. The multi-beam optical scanning device according to claim 1, wherein said plurality of beam generating sources are each constituted by a laser diode, and each laser diode is connected to a common ground terminal. 5. The multi-beam optical scanning device according to claim 1, wherein each of said plurality of beam generating sources is constituted by a laser diode, and each laser diode is connected to a common power supply terminal.