JPH0722679A - Laser drive device and image recording method by laser scanning - Google Patents

Abstract

PURPOSE:To obtain laser light amount output of accurate duty ratio by adjusting the duty ratio of binary current value driven by a laser current drive means based on characteristic data stored in laser characteristic memory means. CONSTITUTION:A microcomputer 1 measures current-to-light quantity characteristic to a maximum light quantity PDmax, obtains a threshold current Ir whereat a laser diode 5 starts light emission and calculates Ir/Imax wherein Imax is a laser current at a maximum light quantity output. Duty ratio of laser driving waveform reduces as Ir/Imax is close to one. The microcomputer 1 reads data stored in ROM corresponding to Ir/Imax, outputs specified data as selection signals S0, S1, S2 to correct reduction of duty ratio and turns an LON signal to L. When S0=L, S1=H, and S2=L, a D2 signal is output to a D2, terminal of a selection circuit 8, enters a voltage current converter and corrects duty ratio of an image signal VD0.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser driving device applicable to a laser beam printer, a magneto-optical disk, etc., and an image recording method for scanning an image on a photosensitive member with a laser beam. .

[0002]

2. Description of the Related Art (1) In recent years, laser beam printers have been widely accepted in the market as high-resolution, high-speed printers. Further demands for high resolution and high speed are increasing.

An important factor in increasing the resolution and speed of this laser beam printer is the high-speed response of the semiconductor laser driving device. For example, 16 sheets of A4 size paper are printed per minute, and the resolution is 600 × 600 (d
pi), the modulation frequency of the semiconductor laser is 17 MH
It may be z.

On the other hand, the peak of the driving current of the semiconductor laser needs to be about 30 mA to 100 mA. When switching such a large current, it is difficult to keep the rise time and fall time of the laser drive current low.

Therefore, the ratio of the rise time and the fall time to the modulation period is large, and as a result, the laser current waveform is different from the square wave, as shown in FIG.
The waveform becomes distorted as shown in FIG.

Further, the current-light quantity characteristic of the semiconductor laser has a characteristic as shown in FIG. In FIG. 4, I _T
Is the current at which the semiconductor laser starts laser oscillation and is called the threshold current of the laser.

In the region where the laser current is I _T or more, the laser light amount changes almost linearly with respect to the laser current. The slope in that region is called slope efficiency η (mW / mA).

When a laser current having the waveform shown in FIG. 3A is applied to a semiconductor laser having such characteristics, the resulting light quantity waveform becomes the waveform shown in FIG. 3B.

As can be seen from FIG. 3B, the period t _on during which the laser is emitting and the period t during which the laser is not emitting are shown.
Comparing the _off, apparently t _on becomes shorter than the t _off. The reason is that the time required for the rise and fall of the laser current occupies a considerable proportion of the laser modulation period. This becomes more remarkable as the laser driving frequency becomes higher.

(2) In the laser beam printer, the modulated laser beam is made into parallel light by a collimator lens, the laser beam is repeatedly reflected and scanned by a rotating rotary polygon mirror, and the reflected laser beam is reflected. An image is formed by irradiating and scanning the photoconductor through the f-θ lens.

The density between the scanning lines on the photosensitive member formed by the irradiation of this modulated laser beam, that is, the resolution is set by changing the blinking period of the laser, the laser power and the rotational speed of the rotary polygon mirror. It For example, when the resolution is increased from 240 dpi (dots / inch) to 480 dpi, the frequency of the video signal is quadrupled, that is, the laser blinking cycle is set to 1/4, and the laser power is reduced by several tens of percent (it varies depending on image forming conditions. ), By doubling the number of rotations of the rotary polygon mirror.

[0012]

(1) As described in the prior art (1), the higher the laser driving frequency, the higher the duty ratio (= T _on / T) of the laser emission.
_off ) has the disadvantage of being small.

Further, the threshold current I _{T of the} semiconductor laser is
In many cases, the slope efficiency and the slope efficiency greatly vary depending on the lot of the laser, which causes a large variation in the duty ratio of laser emission.

Therefore, in view of the above points, a first object of the present invention is to provide a laser driving device configured to always obtain an accurate laser light amount output with a laser emission duty ratio regardless of the semiconductor laser characteristics. is there.

(2) Conventional Technique In the conventional example described in (2), the method of decreasing the laser power is adopted among the methods of increasing the resolution, and therefore the higher the resolution becomes, the more the laser power control accuracy becomes. Will be more demanding.

Therefore, the reason will be described in detail with reference to FIG.

FIG. 9 shows the relationship between the drum surface light quantity and the drum potential V. The drum electric potential V is a negative electric potential, and the drum electric potential moves in the positive direction as the irradiation laser power increases, so that the toner can easily be carried. That is, the density of the printed image is increased.

Here, in the drum surface light amounts P and P ', P is a light amount set at a high resolution, and P'is a light amount set at a low resolution. Further, ΔP and ΔP ′ are the above P,
The control error when the light amount is P'is shown. From this characteristic, assuming that the values of .DELTA.P and .DELTA.P 'are the same, the fluctuation .DELTA.V of the drum potential due to the control error of P is greater than the fluctuation .DELTA.V' of the drum potential due to the control error of P '. It will be.

That is, the density unevenness due to the fluctuation of the drum surface light amount P is larger than that of the drum surface light amount P '. On the contrary, in order to suppress the fluctuation of the drum potential, the control accuracy of the drum surface light amount P must be higher than that of P '.

Further, control of laser power (hereinafter referred to as APC
Is abbreviated), and digital control using a CPU is generally used. In this case, the quantization error is a major factor in the control accuracy of the APC. This quantization error is a constant power value (m
W / bit), the smaller the laser power, the worse the control accuracy of the APC.

Therefore, in view of the above-mentioned point, the second object of the present invention is to provide an image recording method in which unevenness of light and shade of an image at high resolution is suppressed by appropriately controlling the laser power.

[0022]

(1) In order to achieve the first object of the present invention, the present invention provides a laser current drive means for supplying a binary-modulated current to a semiconductor laser, and the laser. Laser current control means for controlling the peak current of the laser current flowing by the current drive means, laser light amount detection means for detecting the light amount from the semiconductor laser, and based on the respective outputs of the laser current control means and the laser light amount detection means Measuring the current vs. light quantity characteristic of the semiconductor laser, and a laser characteristic storing means for storing the characteristic data,
A duty ratio adjusting means for adjusting the duty ratio of the binary current value supplied by the laser current driving means based on the characteristic data stored in the laser characteristic storing means.

(2) In order to achieve the second object of the present invention, the present invention scans a photosensitive member with a laser beam which is modulated according to an image signal, whereby a static image formed on the photosensitive member is scanned. In a method of developing an electrostatic latent image, transferring the developed powder image to a transfer material, and then fixing the image to record an image, a laser power that contributes to recording of the photosensitive member is applied to the photosensitive member. The value is set higher than a value suitable for the scanning line density specific to scanning, and the lighting time of the laser beam is set shorter than the lighting time corresponding to one pixel.

[0024]

(1) According to the above configuration of the present invention, the laser current control means and the laser light quantity detection means measure the current-to-light quantity characteristic of the laser, and based on the data of the characteristics stored in the laser characteristic storage means, By adjusting the duty ratio of the binary current value driven by the laser current driving means, it is possible to obtain an accurate laser light amount output with a duty ratio that is not affected by variations in the characteristics of the semiconductor laser.

(2) In the present invention, in the laser lighting operation, the laser light amount is set to be larger than a predetermined light amount, and at the same time, the laser lighting time is set to be shorter than the predetermined time, so that the grayscale of an image with high resolution is obtained. It is possible to suppress unevenness.

[0026]

EXAMPLES Hereinafter, each example of the present invention will be described in detail.

Embodiment 1 Hereinafter, a first embodiment of the present invention will be described.

FIG. 1 is a block diagram showing a laser drive circuit according to the first embodiment of the present invention. 1 in this figure
Is a microcomputer, in which a read-only memory (ROM) storing the control procedure and other control programs shown in FIG. 5, a random access memory (RAM) temporarily storing data, and a ROM are stored. A microprocessor that executes the program is included.

Reference numeral 2 denotes a D / A converter, which receives parallel digital data output from the microcomputer 1 and converts the digital data into an analog voltage.

Reference numeral 4 is a voltage-current converter with a switch function. That is, the analog voltage output from the D / A converter 2 is input to the V _i terminal of the voltage-current converter 4, the analog voltage is converted into an analog current and output from the I _o terminal. The I _o terminal of the voltage-current converter 4 is connected to the laser diode 5, and the current output from the I _o terminal also flows through the laser diode 5. Further, the voltage-current converter 4 has a switch terminal D _i . When this D _i is at the “H” level, a current flows through the I _o terminal, and when this D _i is at the “L” level, a current flows through the I _o terminal. Does not flow.

When a current flows through the laser diode 5 and the laser emission starts, a part of the laser light is applied to the photodiode 6. The laser light applied to the photodiode 6 is converted into a current according to the light intensity, and the current flows through the resistor 7.

When the photodiode current flows through the resistor 7, the current is converted into a voltage, and the terminal voltage P _o of the resistor 7 is input to the A / D converter 3 of 3. The A / D converter 3 converts the terminal voltage P _o of the resistor 7 into digital data in parallel format. The parallel digital data output from the A / D converter 3 is input to the microcomputer 1.

Reference numeral 8 is a signal selection circuit, which inputs eight digital signals (D ₀ , D ₁ , D ₂ , D ₃ , D).
₄ , D ₅ , D ₆ , D ₇ ) and outputs the selected signal to the D _S terminal.

The selection of this signal in the signal selection circuit 8 is performed according to a command from the microcomputer 1. That is, the signal output to the D _S terminal is selected according to the states of the three selection signals S _S output from the microcomputer 1. These three selection signals S _S are respectively S
_{When 0} , S ₁ and S ₂ are set, the signal output to the D _S terminal is as shown in Table 1 below.

[0035]

[Table 1]

The signal output from the D _S terminal of the signal selection circuit 8 is input to the OR circuit 28. Further, the OR circuit 28
The LON signal output from the microcomputer 1 is input to the other input terminal of the. The output of the OR circuit 28 is input to the D _i terminal of the voltage-current converter 4. This OR circuit 28 causes the D _i terminal of the voltage-current converter 4 when either the signal output from the D _S terminal of the signal selection circuit 8 or the LON signal output from the microcomputer 1 is at the “H” level. Becomes "H" level and its I
_o Current flows to the terminal.

9, 10, 11, 12, 13, 14, 1
Reference numerals 5 and 16 are delay circuits. These delay circuits delay the input digital signal for a fixed time and output the delayed signal. The delay times of the delay circuits 9 to 16 are made substantially equal.

The outputs of the delay circuits 9 to 16 are ORed respectively.
Circuits 17, 18, 19, 20, 21, 21, 23, 24
Entered in. The same signal as the input signal of the delay circuit 9 is input to the other input terminals of the OR circuits 17 to 24.

A driver circuit 25 receives the input image signal VD _o, and receives the delay circuit 9 and the OR circuit 17-.
24 to transmit the signal.

FIG. 2 shows the image signal VD _o and the terminals D ₀ , D ₁ , D ₂ , D ₃ , D ₄ , D ₅ and D of the signal selection circuit 8.
₆ shows the timing of the signals input to D ₇ . As shown in FIG. 2, terminals D ₀ , D ₁ , D ₂ , D ₃ , D ₄ ,
The signals D ₅ , D ₆ and D ₇ are signals obtained by changing the duty ratio of the original image signal VD _o . That is, the duty ratio of the signal at the terminal D ₇ is the largest, and the duty ratio of the signal at the terminal D ₀ is the smallest.

If the selection signals S ₀ , S ₁ and S ₂ are set to predetermined states, the image signal with the duty ratio changed as described above can be selected as the signal from the D _S terminal.

Next, the control procedure of the microcomputer 1 (stored in the ROM) will be described according to the flow shown in FIG.

First, the microcomputer 1 resets the data ID (i) input to the D / A converter 2 to a predetermined value, and sets the LON signal to "H" level (S3-1, S3).
-2). At this time, as already described, a predetermined current flows through the laser diode 5.

Then, the microcomputer 1
The output data of the A / D converter 3 corresponding to D (i) is received (S3-3).

When the current flowing through the laser diode 5 is small, it does not emit light as shown in FIG. Therefore, at this time, the terminal voltage P _o of the resistor 7 is equal to zero, and the output data of the A / D converter 3 is also “0”.

The microcomputer 1 is an A / D converter 3
The more received data PD (i) is compared with the predetermined value PD _max, and it is determined whether PD (i) ≧ PD _max is satisfied (S3-4).

If PD (i) <PD _max , S3
Move to step -5, the microcomputer 1 ID
(I) and the corresponding PD (i) are stored in the RAM. Then, ID (i) is increased by a predetermined amount, and i is i +
Set to 1 (S3-6, S3-7). And S3
Return to step -2 to set data again in the D / A converter 2.

When ID (i) gradually increases in this way, the current of the laser diode 5 also gradually increases. When the current of the laser diode 5 exceeds the threshold current I _T shown in FIG. 4, the laser diode 5 starts emitting light. When ID (i) further increases, PD (i) approaches the maximum light amount PD _max .

When PD (i) ≧ PD _max is satisfied, the process proceeds to step S3-8.

The above-mentioned (S3-1), (S3-2),
(S3-3), (S3-4), (S3-5), (S3-
The procedures shown in steps 6) and (S3-7) are merely procedures for the microcomputer 1 to digitally measure the current-to-light quantity characteristic of the laser diode 5.

The microcomputer 1 has a maximum light amount PD
If the current-light quantity characteristic to the _max finishes measured at a predetermined step, the microcomputer 1 can be determined a threshold current I _T of the laser diode 5 starts emitting light (S3-8). The threshold current is _IT , the maximum light intensity PD
When the laser current when outputting the _max and I _max,
The microcomputer 1 calculates I _T / I _max .

As shown in FIG. 3, as I _T / I _max approaches 1, the duty ratio of the laser drive waveform decreases. Since the rise time of the laser current shown in FIG. 3A is known here, the microcomputer 1
After calculating I _T / I _max , the change in the duty ratio of the laser drive waveform corresponding to the calculated value can be estimated.

For this estimation, the microcomputer 1 only has to read the data stored in the ROM corresponding to the I _T / I _max . Then, in order to correct the decrease of the duty ratio, the selection signals S ₀ , S ₁ , S
_The specified data is output as ₂ . At the same time, the microcomputer 1 sets the LON signal to "L" level.

For example, the microcomputer 1 uses S ₀ =
When “L”, S ₁ = “H”, and S ₂ = “L”, the D ₂ signal is output to the D _S terminal of the signal selection circuit 8. This makes it possible to select a signal in which the duty ratio of the original image signal VD _o is widened.

The D ₂ signal is the D of the voltage-current converter 4.
It is transmitted to the _i terminal. As a result, the signal in which the duty ratio of the image signal VD _o is corrected can be transmitted to the voltage-current converter 4, and the duty ratio of the laser light amount waveform can be set to 50%.

Embodiment 2 FIG. 6 is a block diagram showing a laser drive circuit according to the second embodiment. The difference between FIG. 6 and FIG. 1 is that FIG.
That is, the delay circuits 9 to 16 used in 1) are replaced with the D-type flip-flops 29 to 36.

In the first embodiment described above, it is necessary to use a highly accurate analog delay circuit (for example, an LC delay line using an inductor and a capacitor), but this analog delay circuit is difficult to integrate. is there. Therefore, in the second embodiment shown in FIG. 6, in order to avoid the problem, the analog delay circuit is replaced with a digital D-type flip-flop (hereinafter abbreviated as D-type F / F).

D type F / F 29, 30, 3 shown in FIG.
1, 32, 33, 34, 35 and 36 respectively have an output terminal Q and a clock terminal CK clock-synchronized with the input terminal D.
There is. All clock terminals CK of these D type F / F
The same reference clock signal is input to. The frequency of this reference clock is set to be considerably higher than the frequency of the image signal VD _o . For example, the frequency of the reference clock is set to be 32 times the basic frequency of the image signal VD _o .

FIG. 7 shows a timing chart regarding the image reference clock, the image signal VD _o , and the signals input to the terminals D _{0 to} D ₇ of the signal selection circuit 8 in that case. As shown in FIG. 7, the duty of the image signal VD _o can be changed in units of one cycle of the image reference clock. That is, the duty ratio of the image signal VD _o can be corrected by selecting the signals input to the terminals D _{0 to} D ₇ as in the first embodiment.

Embodiment 3 Prior to a detailed description of the third embodiment, first, referring to FIG.
The principle of the present invention will be described with reference to FIG.

FIG. 8A shows the laser beam intensity,
(B) of the figure shows a laser drive signal.

That is, by setting the laser light amount larger than a predetermined light amount, the fluctuation of the drum potential due to the fluctuation of the laser light amount is suppressed, and at the same time, the lighting time is changed from t ₁ to t _2.
By shortening it to 1, the image thickening due to the increase of the laser light amount is suppressed. That is, the laser beam intensity is changed from P in the prior art (see FIG. 9) to P '.

10 to 12 are views showing a third embodiment of the present invention. In the third embodiment, the laser light amount is increased and the lighting width is shortened for each pixel.

In FIG. 10, 110 is a CPU,
It controls the sequence of a laser beam printer (not shown) and drives the laser.

Reference numeral 111 is a D / A converter, and 112 is a laser drive current source. The digital value output from the CPU 110 is converted into an analog value by the D / A converter 111, and the laser drive current source 112 supplies a current proportional to this voltage value to the laser diode 117 via the switch circuit 113. The switch circuit 113 is turned on / off according to a laser modulation signal, and the current from the laser driving current source 112 is supplied to the laser diode 117 during the ON operation.
Supply to.

The laser diode 117 emits light by supplying a current and irradiates a drum (not shown). At the same time, the laser diode 117 also enters the monitor photodiode 116 to detect the emission power.

Reference numeral 115 is an I / V converter for converting the detected photoelectric current into voltage, and 114 is an I / V converter 115.
It is an A / D converter that converts the output voltage from the device into a digital value. The CPU 110 uses the A / D converter 114
The amount of light emitted from the laser diode 117 is detected by reading the digital value output from the laser diode 117.

CPU 110, D / A converter 11
1, laser drive current source 112, switch circuit 113, laser diode 117, photodiode 116, I /
An AP that sets the laser light amount to a predetermined value by a combination configuration of the V converter 115 and the A / D converter 114.
The C operation is executed.

Next, this APC operation procedure (RO in FIG. 10)
(Stored in M) will be described with reference to the flowchart shown in FIG.

First, the CPU 110 outputs a preset value that should be the target laser light amount (S23).

Then, in order to turn on the laser diode 117, a laser ON signal is output to switch the switch circuit 11
3 is turned on and the laser diode 117 is turned on (S24).

Thereafter, the amount of emitted light detected by the photodiode 116 is input via the A / D converter 114 (S25).

It is judged whether or not this input value is larger than the target value (S26), and if it is larger, the set value is decremented to reduce the laser light amount (S2).
8).

If the input value is not larger than the target value, it is next determined whether or not the input value is smaller than the target value (S27). If the result is small, the set value is incremented to increase the laser light amount (S2
9).

If the input value is neither large nor small with respect to the target value, it is determined that the laser light amount is emitting a predetermined light amount, and the APC operation ends. Therefore, the means for increasing the light amount in this embodiment is realized by increasing the target value.

Next, the shortening of the lighting width of the laser will be described.

Reference numeral 118 in FIG. 10 is a D-type flip-flop,
Reference numeral 119 is an inverter, 120 is an AND circuit, 121 is a monostable multivibrator (one-shot multivibrator), and 122 is an OR circuit.

FIG. 1 shows the timing of each of the above circuits.
It is 1.

At the timing of printing the image data, the laser ON signal is "L" and the ENB signal is "H". Here, the laser ON signal is used as the laser ON signal from the CPU at the time of the above-described APC operation, and the ENB signal is used to prevent the laser from being erroneously turned on at times other than the printing operation.

The VDO signal and the VDO-CLK signal are input from the host computer or the like connected to the printer at the timing shown in FIG. First, the D-type flip-flop 118 causes the VDO signal and VDO-C.
The LK signals are synchronized. D-type flip-flop 1
The output signal Q of 18 is supplied to one input terminal of the AND circuit 120, and the signal obtained by inverting the VDO-CLK signal is supplied to the other input terminal.

Therefore, when the VDO-CLK signal is "L",
At the timing when the Q output of the D-type flip-flop 118 is "H", the monostable multivibrator 121
Triggers. This trigger causes the monostable multivibrator 121 to output only one pulse having a preset width.

This pulse width is set to be shorter than one cycle of the VDO-CLK signal, that is, the time for one pixel.
It is input to the laser diode 117 via the circuit 122 as a waveform like a laser modulation signal (see FIG. 11).

By the above operation, the laser diode 117 is turned on for each pixel in a time shorter than the original lighting time of one pixel.

Embodiment 4 FIGS. 13 to 15 are views showing a second embodiment of the present invention. In the second embodiment, the laser light amount is increased only in the peripheral pixels of the image and the lighting time is shortened, and the lighting time is set to one pixel for the other pixels.

In FIG. 13, a CPU 110, a D / A converter 111, a laser drive current source 112, a switch circuit 113, a laser diode 117, an A / D converter 114, an I / V converter 115, and a photodiode 116.
Since the APC operation having the above structure is similar to that of the first embodiment, its explanation is omitted.

The control of the lighting time of the laser diode will be described below.

First, as an image example, the image shown in FIG. 15 is assumed. Each cell in FIG. 15 corresponds to one pixel, and the number attached to each pixel indicates the order in which pixel data is output. Further, white pixels are white (that is, the laser diode 117 is OFF), and black pixels are black (that is, the laser diode 117 is ON). Therefore, in this image example, a rhombic image is printed.

In the present embodiment, the peripheral pixels (pixel Nos. 4, 5, 11, 14, 18, 23, in the image example of FIG.
25, 32, 33, 40, 42, 47, 51, 54, 6
0, 61), the lighting time is shortened, and the other pixels are lit for one pixel.

In FIG. 13, reference numeral 130 is a line buffer and a peripheral pixel detection circuit, and VDO-C is output from the output terminal thereof.
The LK signal and the VDO signal synchronized with the LK signal are output, and the signal VDO-CNT signal indicating the peripheral pixels is output at the same timing. FIG. 14 shows the timing.

In FIG. 14, pixel No. 4,5,11,1
Since 4, 18, 23, and 25 are peripheral pixels, the VDO-CNT signal becomes "H" at that timing. VDO
When the -CNT signal is "H", the lighting time of the laser diode is shortened.
AND the O-CNT signal and the VDO-CLK signal,
When the VDO-CNT signal is "H" and the VDO-CLK signal is "H", the next-stage monostable multivibrator 135 is triggered (A signal in the figure), and only one pulse having a predetermined pulse width is output. (C signal in the figure). This pulse width is set shorter than the time for one pixel.

Further, the output of the monostable multivibrator 135 is delayed by the delay circuit 36. The output of the delay circuit 36 and the output of the monostable multivibrator 135 are ANDed by the AND circuit 137 in the next stage.
Therefore, the lighting time of the laser diode becomes shorter than the time of one pixel.

On the other hand, for the other pixels, VDO
Signal and inverted signal of VDO-CNT signal (inverter 13
2 is inverted by the AND circuit 133.
Then, only the pixels other than the peripheral pixels are extracted, and the D-type flip-flop 134 synchronizes with the VDO-CLK signal (B signal in the figure).

The signals of the peripheral pixels and the other pixels are ORed.
The OR circuit 138 drives the switch circuit 113 as the waveform of the laser modulation signal in FIG. 14 to turn on the laser diode 117.

[0094]

As described above, according to the present invention, when the semiconductor laser is driven, the current-light amount characteristic of the semiconductor laser is first measured, and the duty ratio of the image signal is changed according to the characteristic. Therefore, it is possible to maintain the duty ratio of the laser light amount waveform at a predetermined value even when the current-light amount characteristic of the semiconductor laser changes.
It is possible to always stably switch the laser light.

(2) According to the present invention, a higher laser power than the proper laser power in the electrophotographic process is set, and at the same time, the lighting time of the laser for each pixel is shortened to obtain a high resolution. It is possible to suppress the occurrence of uneven density in the image.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is a timing diagram showing the operation of FIG.

FIG. 3 is a diagram showing a general drive waveform of a laser diode.

FIG. 4 is a diagram showing a general current-light quantity characteristic of a laser diode.

FIG. 5 is a flowchart showing a control procedure in the first embodiment.

FIG. 6 is a block diagram showing a second embodiment.

FIG. 7 is a timing diagram showing the operation of FIG.

FIG. 8 is an explanatory diagram showing the principle of the third and fourth embodiments.

FIG. 9 is a diagram showing a relationship between a drum surface light amount and a drum surface potential.

FIG. 10 is a block diagram showing an electrical configuration of a third embodiment.

11 is a waveform diagram showing the operation of FIG.

FIG. 12 is a flowchart showing a control procedure in the third embodiment.

FIG. 13 is a block diagram showing an electrical configuration of a fourth embodiment.

FIG. 14 is a waveform diagram showing the operation of FIG.

FIG. 15 is a diagram schematically illustrating a print image according to a fourth embodiment.

[Explanation of symbols]

 1 Microcomputer 2 D / A converter 3 A / D converter 4 Voltage-current converter 5 Laser diode 6 Photodiode 8 Signal selection circuit 9-16 Delay circuit 17-24 OR circuit 110 CPU 111 D / A converter 112 Laser drive Current source 113 Switch circuit 114 A / D converter 115 I / V converter 116 Photodiode 117 Semiconductor laser (diode) 118 D-type flip-flop 119 Inverter 120 AND circuit 121 Monostable multivibrator 122 OR circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hideki Suzuki 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Kenji Takubo 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Incorporated (72) Inventor Masaharu Tsukada 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inhito Hideto Iwama 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Ryo Nakatani 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (5)

[Claims] 1. A laser current drive means for supplying a binary-modulated current to a semiconductor laser, a laser current control means for controlling a peak current of a laser current flowing by the laser current drive means, and a laser current control means for controlling the peak current of the laser current. A laser light amount detecting means for detecting a light amount, a current versus light amount characteristic of the semiconductor laser is measured based on each output of the laser current control means and the laser light amount detecting means, and a laser characteristic storing means for storing the characteristic data. And a duty ratio adjusting means for adjusting the duty ratio of the binary current value supplied by the laser current driving means based on the characteristic data stored in the laser characteristic storing means. apparatus. 2. The laser driving device according to claim 1, wherein the duty ratio adjusting means has a plurality of delay circuits and a combinational logic circuit group connected to the output side of the delay circuits. 3. The duty ratio adjusting means according to claim 1, wherein the duty ratio adjusting means has a plurality of clock-synchronized flip-flop circuits and a combinational logic circuit group for inputting output signals of the flip-flop circuits. Laser drive device. 4. The semiconductor device according to claim 1, wherein the laser characteristic storage means includes a semiconductor read-only memory storing a program, a microcomputer operating according to the program stored in the read-only memory, and data processed by the microcomputer. And a random access memory for storing the laser. 5. A laser beam modulated according to an image signal is scanned on a photoconductor to develop the electrostatic latent image formed on the photoconductor, and the developed powder image is used as a transfer material. In the method of transferring and then fixing the image to record an image, the laser power contributing to recording of the photoconductor is set higher than a value suitable for a scanning line density specific to scanning the photoconductor, and An image recording method characterized in that a lighting time of the laser beam is set shorter than a lighting time corresponding to one pixel.