JPH03232282A - Semiconductor laser drive device - Google Patents

Abstract

PURPOSE:To enable a semiconductor laser to keep monotonous in density and to obtain a gradated exposure energy by a method wherein a light emission time is controlled within a maximum light emission time to adjust an emission energy, and an emission time is fixed to a maximum light emission time to increase an optical output when it reaches a prescribed emission energy. CONSTITUTION:A semiconductor laser 20 is made to start emitting light, a photodiode 21 outputs a voltage VM detecting the light concerned, and when VM reaches to a set value of VBM, a microprocessor 1 stops the output voltage V3 of a D/A converter 4 from increasing. The output voltage V2 of a D/A converter 5 is made to increase gradually until the voltage of VM reaches to a prescribed value of VWM. Input data to the D/A converter 6 is set to the same data at the time when the maximum image data are inputted, the output voltage V4 of the D/A converter 3 is made to increase gradually and to stop increasing when it reaches to a prescribed value of VmaxM, and the output voltage V4 of the converter 3 is determined. Then, the microprocessor 1 sets an LON signal high in level and an MPX 45 to a subtracter 41 side and starts reading image data and executing a printing operation.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a semiconductor laser driving device, and particularly to a semiconductor laser driving device for obtaining continuous gradation on a photosensitive material, for example, by adjusting the emission energy of laser light from a semiconductor laser. Concerning technology for improving equipment.

<Prior Art> Conventionally, laser printers and the like have been known that are configured to expose and scan a photosensitive material by modulating the intensity of a laser beam generated by a semiconductor laser (laser diode; LD) using an external optical modulator. However, by directly controlling the current supplied to the semiconductor laser without using the external modulator, the optical output of the semiconductor laser is controlled, and continuous gradation (not a dithered image but a single pixel image) is produced on the photosensitive material. The following methods were used to obtain the gradation information.

Semiconductor lasers have certain characteristics between the supplied current and the generated optical output, so if the current is controlled by the required gradation, the optical output can be directly controlled without using an external modulator. In order to obtain 256 (2') gradations, it is sufficient to divide the current into 256 steps.

Continuous gradation can also be obtained without using an external modulator by keeping the current supplied to the semiconductor laser constant, keeping the optical output constant, and variably controlling the pulse width of one pixel clock (emission time per pixel). For example, if one pixel clock is 300 ns (maximum exposure time), if the pulse width is controlled from 1 ns to 300 ns in ins increments, 3
A time resolution of 0.00 steps can be obtained, and 300 continuous gradations can be obtained by controlling the exposure time of 300 steps (Japanese Patent Laid-Open Nos. 56-152372 and 61-580).
(See Publication No. 68, etc.).

Note that when controlling the pulse width of one pixel clock as described above, it is also possible to change the pulse width by analog processing in addition to digital processing as described above.

Furthermore, it is also possible to provide a plurality of N current sources with different current values for the semiconductor laser, and to digitally combine these current sources to obtain a light intensity level of 2M level (especially Kaisho 63-184
(See Publication No. 773, etc.).

There is also a device configured to obtain multiple gradations by modulating both the optical output and exposure time of a semiconductor laser (see Japanese Patent Laid-Open No. 124921/1983).

<Problems to be Solved by the Invention> By the way, in the configuration as described above in which continuous gradation is obtained by decomposing and controlling the current according to the number of required gradations, the output characteristics of the semiconductor laser used are shown in FIG. 35, for example. If the usable range of optical output is 0 to 3 mW, the current difference in the optical output range is 14 mA. Here, if we want to obtain 256 steps of gradation, 14m^/256 =
It is necessary to control the current with an accuracy of 55 μA, and as shown in Fig. 36, the digital input image data is converted by a D/A converter and sent to a semiconductor laser (LD) via an amplifier.
), there are problems in that a high-speed and high-precision D/A converter is required, leading to an increase in cost, and it is also difficult to ensure the required precision.

Furthermore, when variably controlling the pulse width of each pixel or elementary clock using digital processing, if you try to obtain sufficient gradation from the pulse width alone, it is necessary to finely set the increments (unit increment time) of the pulse width. For example, if you want to obtain 1024 steps of gradation and one pixel clock is 300ns, the pulse width increments are 300ns/1024=0.3
ns, and a time resolution on the order of GHz is required. It is difficult to achieve such time resolution using normal circuit technology, and the method of variable pulse width control as described above is effective when the required frequency of the pixel clock is low (on the order of KHz), but as it increases The feasibility becomes low.

In addition, when performing variable pulse width control as described above by analog processing, for example, a triangular wave synchronized with the pixel clock is generated, and this is compared with the analog value of the input data to convert it into a pulse width. In this case, high-frequency pulses are not required, but it is necessary to generate a triangular wave with an accurate slope, which is difficult to realize, and the accuracy is also inferior to digital processing.

Furthermore, in the method of obtaining continuous gradation by providing multiple current sources, for example, if you want to obtain 1024 (210) steps of gradation, 10 current sources are required, which makes the circuit complicated and increases costs. I can't. In addition, for example, Japanese Patent Application Laid-Open No. 63-184773 uses a method using multiple current sources.
In the publication disclosed in the publication, the characteristics of the optical output and current of the semiconductor laser are assumed to be as shown in FIG. 37, but in reality, the semiconductor laser starts oscillating as shown in FIG. 35. The optical output hardly changes below the boundary current (threshold current) (spontaneous emission region), whereas the optical output increases rapidly when the boundary current exceeds the boundary current (laser oscillation region). If the number of current sources is N, it cannot be said that a light amount level of 2N level can be obtained.

Furthermore, as shown in FIG.
Divide the current so that it becomes P0 (■., ■1°...)
Then, ■ in the nonlinear region. , I+, and Ig are not equal to each other, and ■, ~■, in the linear region are equal. Therefore, the minimum number of bits (L
SB) as A, the next number of bits is 2A, then 4A,
...Is it possible to combine these units to obtain 2N optical outputs as a 2N-IA? ! It (control assuming that the relationship between optical output and current is linear) cannot be performed.

That is, in the example shown in FIG. 38, LSB=1. In Although,
The current corresponding to input data 2 is 1. +1. ≠2■・, and the current corresponding to input data 3 is [.

+ 11+ I t≠3■. Furthermore, the current corresponding to input data 4 is Io+ I++ Iz+ Ix≠4
Since it is To, the above-mentioned A, 2A, 4A, ・
... 2N optical outputs cannot be reliably obtained from N-1 units of 2N-IA.

In addition, in the case of a configuration in which both the optical output and the exposure time of a semiconductor laser are modulated, for example, according to an embodiment in Japanese Patent Laid-Open No. 124921/1982, input digital data is divided into lower bits and upper bits, and the lower bits are The pulse width is controlled by the pulse width, and the optical output (supply current) is controlled by the upper bit. In this case, the current waveform flowing through the semiconductor laser will be as shown in Figures 39 and 40, but the question is whether monotonicity is guaranteed in the concentration actually obtained when switching the optical output. .

That is, in the case of the examples shown in FIGS. 39 and 40, "P.

×Density obtained at maximum time t0 (1 pixel time)≦P2×
It is difficult to stably establish the density obtained in the minimum time Δt, considering variations in the photosensitive material, changes over time, changes over time in the process, reciprocity law failure characteristics of the photosensitive material, etc., and the monotony of the concentration is difficult. If this is not achieved, gradation characteristics will deteriorate and faithful density reproduction will not be possible.

The present invention was made in view of the above-mentioned problems, and an object of the present invention is to provide a semiconductor laser driving device that can maintain concentration monotonicity and obtain multi-gradation exposure energy without increasing the resolution of the driving current. shall be.

<Means for Solving the Problems> Therefore, the present invention provides a semiconductor laser driving device that adjusts the emission energy of a semiconductor laser in multiple stages by controlling the emission time and optical output, the semiconductor laser driving device adjusting the emission energy of the semiconductor laser in multiple stages by controlling the emission time and optical output. The light emission energy is adjusted by holding the light output at a constant value and variably controlling the light emission time within the maximum light emission time, and when the light emission energy exceeds the predetermined light emission energy, the light emission time is fixed at the maximum light emission time and the light output is adjusted to the above constant value. The configuration is such that the emission energy is adjusted by controlling the increase as described above.

Here, the optical output of the semiconductor laser can be controlled to increase by increasing the bias optical output.

Further, the optical output of the semiconductor laser can be controlled to increase by selectively switching and controlling a plurality of semiconductor laser current sources connected in parallel.

Furthermore, an optical output attenuation means is interposed in the optical path of the semiconductor laser, and when controlling the optical output and adjusting the emission energy, the optical output is controlled in a region where the optical output is linear with respect to changes in the supplied current. It is preferable to configure it as follows.

<Function> According to the semiconductor laser drive device having such a configuration, when the required light emission energy is less than a predetermined value, the semiconductor laser light output is held at a constant value and the light emission time is kept within the maximum light emission time (for example, one pixel clock). By variable control with
It is possible to obtain the type of luminous energy (gradation when exposing a sensitive material) according to the step of luminous time control,
In addition, if the required light emission energy cannot be obtained even if the light is emitted for the maximum light emission time under the constant light output, then the light emission time is fixed at the maximum light emission time, and instead the light output is increased to the above certain value or more. Greater luminous energy can be obtained by increasing the
The type of luminous energy (
When exposing a sensitive material, it is possible to obtain gradations), and as a result, the final emission energy can be controlled as the sum of the number of steps of emission energy controlled during emission time control and light output control. Steps are set.

Here, when controlling the light output, the light output is increased above the light output maintained when controlling the light emission time, so that the light emission energy obtained during the light emission time control and the light output control do not overlap.

<Example> The present invention will be described in detail below. This embodiment is a laser printer configured to expose and scan a sensitive material with laser light while adjusting the exposure energy by directly controlling the current supplied to a semiconductor laser to obtain continuous gradation on the sensitive material. etc. is assumed.

First, before describing an embodiment of a semiconductor laser driving device according to the present invention, an example of the characteristics of a photosensitive material exposed and scanned by a semiconductor laser will be described with reference to FIG.

In the diagram shown in FIG. 4, the vertical axis is the density D of the photosensitive material due to laser exposure, the horizontal axis is the pulse width (exposure time) Tw (ns) of the supply current control pulse signal, and the optical output of the semiconductor laser (m The characteristics at each light output are shown by changing W ), and the maximum exposure time for one pixel (one pixel clock) is 320 ns.

Here, due to the T characteristic (gamma characteristic) of the photosensitive material, from the highlight (density 0.4 to 0.5) to the shadow (1.0 to 1
．． 5), the slope of the density change with respect to the pulse width Tw change is steep in the part where it is necessary to have the most gradation step. In addition, when the optical output of the semiconductor laser is lowered, the slope of the concentration change with respect to the pulse width Tw becomes gentler, so the concentration can be controlled accurately by the pulse width Twf#Jm.
Gradation expression using the pulse width Tw becomes easier, but if the light output is low, the maximum density will decrease even if exposed for one pixel clock (320 ns). 8
) is not obtained. For this reason, when the optical output is increased in an attempt to obtain the maximum density D ) must be reduced to 7 nanoseconds or less to obtain the necessary concentration resolution.

Moreover, without modulating the pulse width Tw, the maximum pulse width (
FIG. 5 shows the characteristics when the optical output of the semiconductor laser is changed at 320n+s).

Here, if we compare and refer to Figures 4 and 5, we can see that, for example, the optical output of the semiconductor laser is set to 0.21, pulse width Tw control is first performed, and the maximum pulse width (one pixel clock) is reached. It can be seen that it is preferable to increase the light output at a time when the concentration is 1.5 (concentration 1.5) and control the concentration so as to obtain a higher concentration.

That is, in FIG. 5, the part A is the pulse width Tw control, and the part B is the pulse width Tw control.
The part is for light output control, and in this case, the fourth part is for light output control.
Since the curve C in the figure (light output 0.2 mW) and the curve D in FIG. Further, in the portion C of FIG. 4 where the gradation is obtained by controlling the pulse width Tw, the density rises slowly with respect to the pulse width Tw, so it is easy to obtain a large resolution. However, since the concentration control range by light output control is narrower than when only light output control is performed, the resolution by light output control may be rougher, and there is no need to increase the resolution of the drive current. Furthermore, in the above case, since it is sufficient to obtain a density up to 1.5 with the maximum pulse width, there is no need to increase the optical output during pulse width Tw control more than necessary, and resolution can be ensured by pulse width Tw control. In order to ensure the resolution by controlling the pulse width Tw, it is not impossible to obtain the maximum concentration, and it is possible to solve the problem that it is difficult to increase the concentration resolution only by controlling the pulse width Tw and that the maximum concentration cannot be obtained.

In the case of the above example, the maximum density is 1.8, and the switching point between pulse width Tw control and optical output control is 1.5, so the density difference ΔD is 1.8-1. 5 =
0.3 is the density control range by optical output control. For example, if the density resolution is 0.01, 0.310.01=3
It is sufficient to have an optical output resolution of 0 steps.

Since the light output change in the above range is 0.2 → 0.1 raW, assuming that the light output per density step is linear, (0,7-0,2)/3 per l step.
0 = 0.016 mW. The current increments corresponding to this 0.016d have a slope characteristic of 0.2 as shown in Fig. 35.
If it is 4d/mA, then 0.016niW 10゜2
4=67μA.

On the other hand, the entire concentration range (0,
1 to 1.8) with a resolution of 0.01, (1,8-0,1)10.01=170 steps are required, and the optical output during this time is 0.01→0.7- Therefore, per concentration step (0,7-0,01)
A resolution of /170 = 0.004 mm is required, and the corresponding current step width is calculated in the same manner as above to be 0.00410.24-17 μ8, and as mentioned above, the concentration is 1.5 or more. Compared to the case where the range is resolved by optical output control, approximately 4 times the current resolution is required, and the number of steps required also increases from 30 (5 bits) to 170 (
8 bits), which requires a large number of D/A converter bits, and controlling the optical output at a density of 1.5 or higher is advantageous in terms of current resolution and D/A converter bit number. It turns out that it is.

Here, the above semiconductor laser driving method can be summarized as follows.

That is, as the first stage (pulse division II), as shown in FIG. 6, pulse division is performed under a constant optical output. II (light emission time control within the maximum light emission time) is performed to increase the pulse width with a resolution of unit pulse time until the maximum pulse width (one pixel clock; maximum light emission time) as the required concentration increases. And 1. When the image data area is such that the desired density (exposure energy) cannot be obtained even if the maximum pulse width is applied with the constant light output, the second stage (light output control) is performed.
l1l), the maximum pulse width (
After increasing the pulse width to one pixel clock), the light output is increased step by step with the pulse width set to the maximum pulse width (maximum light emission time) to obtain the maximum density.

A semiconductor laser driving device using the above driving method will be described in more detail below.

First, as a first embodiment, a device constituted by a combination of a pulse width modulation circuit, a current switch connected to the pulse width modulation circuit, and a variable bias current source will be described. That is, in this first embodiment, after reaching the maximum pulse width as shown in FIGS. 8 and 9.

The optical output of the semiconductor laser is increased by increasing the bias current (bias optical output Pit), and the minimum value P of the bias current, l1in (corresponding to the minimum laser power), is the amount of light that the sensitive material is not exposed to. is set to be the output. Of course, the minimum value of the bias current may be set to zero.

FIG. 1 shows the circuit configuration of the semiconductor laser driving device according to the first embodiment, in which a data latch circuit 2 temporarily latches digital input image data Dφ to D8, and a microprocessor (MPU)1
has a plurality of input/output ports, and controls the laser light output according to the control procedure shown in the flowchart of FIG.

The control procedure (control program) shown in the flowchart of FIG. 2 is stored in advance in the internal ROM of the microprocessor 1.

The D/A converter 6 is used to increase/decrease the current value for optical output control 4B (luminance modulation), and the output of the D/A converter 6 is used for the D/A converter for bias current setting, which will be described later.
The output of the converter 4 and the adder 43 are added. The subtracter 41 also receives a set value 40 that stores digital manual data indicating a switching point between pulse width control and optical output control.
is subtracted from the input digital data, and the subtraction result by the subtracter 41 and the signals (MPXSET, MPXRESET) from the microprocessor 1 are converted into MPX
45 and input to the D/A converter 6.

The D/A converters 3 to 5 are connected to the output ports of the microprocessor 1 and convert digital data indicating voltage values output from the microprocessor 1 into analog voltages 12 to 4.

Here, the output of the D/A converter 3 is for span control of the D/A converter 6, and controls the slope of the output voltage with respect to the input digital data of the D/A converter 6.

On the other hand, the output of the D/A converter 4, which is added to the output of the D/A converter 6 in the adder 43, controls the offset bias value. Furthermore, the laser power of the semiconductor laser 20 is controlled by the output of the D/A converter 5, which is pulse width modulated as described later.

The above components 1.3 to 5 constitute a voltage application circuit 30 that applies different voltages to two voltage/current conversion circuits 11.12, which will be described later.

The A/D converter 8 is connected to the input port of the microprocessor 1 and receives a voltage from the photodiode 21.

is converted into digital data and processed by microprocessor 1.
send to The microprocessor l is an A/D converter 8
According to the digital data sent from the photodiode 21 in accordance with the output, the data output to the D/A converters 3 to 5 is adjusted and controlled as described later.

The two voltage/current conversion circuits 11 and 12 convert a voltage value into a current value, and each has an input voltage terminal V.
i, Output current terminal io and output voltage switching (current generation)
It has an input control terminal Di for controlling. The output current terminals Io are connected in parallel to each other, and a semiconductor laser 20 is connected in series to this parallel connection terminal.
is supplied with the sum of the currents output from each voltage/current conversion circuit 11.12.

The generator section 16 divides the pixel clock signal CLK (synchronization signal) into 16 parts and creates 16 types of pulses according to the input data D4 to D7, and the canceling section 17 converts the pulses obtained by the generator section 16 into delay lines. The pulse is further divided into 16 using the following, and the generator section 16 and canceling section 17 generate 2' x 2' = 2@ pulses.

The decoder 42 decodes the input digital data,
When the optical output of the semiconductor laser 20 corresponds to a concentration region equal to or higher than a predetermined value in which the optical output is controlled to increase, a high level signal is output to the selector 15 .

Furthermore, the selection unit 15 controls whether or not to output the pulse width modulation signal to the voltage/current conversion circuit 12 in accordance with the output of the decoder 42 . That is, when the output of the decoder 42 is at a low level, the pulse width control signal from the canceling section 17 is sent to the voltage/current conversion circuit 12. When the output of the decoder 42 is at a high level, a high level signal is always sent to the voltage/current conversion circuit 12 regardless of the signal from the canceling section 17. In addition, as shown in the embodiment shown in FIG. 42, a function is provided to forcibly set the output to a high level using the LON signal from the microprocessor sensor 1. still,
The voltage/current conversion circuit 11 is designed to be always turned on.

As described above, the subtracter 41 uses input image data (stored in the set value 40, (the image data corresponds to a predetermined emission energy at the control switching point) is digitally subtracted from the input digital data, and the result is output to the D/A converter 6.

Further, the MPX 45 switches between the output from the microprocessor 1 (MPXSET, MPXRESET) when the microprocessor 1 initializes the optical output and the image data from the subtracter 41 and outputs the same to the D/A converter 6. That is, when setting the optical output, the microprocessor 1
The output from the subtracter 41 is transmitted to the D/A converter 6, and otherwise the data from the subtracter 41 is input to the D/A converter 6. FIG. 41 shows a specific example of MPX45, in which the control signal MPXSET from microprocessor 1 is high and the D/A
The input to converter 6 is forced to the maximum. Similarly,
When MPXSET and MPXRESET are low, the input to the D/A converter 6 is forced to zero. Also, MPX
SET is low, MPXRESET is high, subtractor 41
The data from the D/A converter 6 will be transmitted to the D/A converter 6.

As described above, the semiconductor laser 20 is connected to the output current terminals IO of the two voltage/current conversion circuits 11 and 12 (wired-OR connection), and the optical output (brightness) of the semiconductor laser 20 is determined by the output current terminal IO of the two voltage/current conversion circuits 11 and 12. detected by. The output voltage of the photodiode 21 is converted into a digital value by the A'/D converter 8 and sent to the microprocessor 1 as described above. Note that the resistor R5 is a load resistor connected between the anode of the photodiode 21 and the ground, and Vcc indicates the power supply voltage.

Figure 3 shows the two voltage/current conversion circuits 1 shown in Figure 1.
1.12 circuit configuration is shown.

In FIG. 3, 117 and 118 are operational amplifiers (OP
amplifier), 119 to 121 are transistors, 122 is an open collector type buffer IC as a negative circuit,
R6 to RIO and R20 to R23 are resistors.

Here, the value of each resistance of R6-R9 is set to a constant value RA, that is,
If R6=R7=R8=R9=RA and the resistance value of RIO is RA>R10, then the collector current 101 of the transistor 119 will be as shown in the following equation. However, Vi is the voltage of the input voltage terminal.

10, =Vi/RIO When the input control terminal Di is at a low level, the transistor 120 is in the ON state, and the collector current 1 described above is
A current approximately equal to 01 flows between the collector and emitter of transistor 120. Further, when the input control terminal Di is at a high level, the transistor 120 is in an OFF state, and the collector current is . .

A current approximately equal to 121 flows between the collector and emitter of transistor 121 at output terminal I. A current is generated.

In this way, depending on the level of the input control terminal Di, ■. ,
L:, turns on/off the conversion current corresponding to Vi/RIO
The circuit shown in FIG. 3 is a voltage/current conversion circuit capable of switching according to the level of the input control terminal Di.

In addition, in Fig. 3, resistors R20, R2L R22, R2
3 is R20#R21#R23, R22X Io+ in advance
The resistance value is selected so that = 1~2■. Also,
It is assumed that the current amplification factors of the transistors 119 to 121 and the voltage amplification factors of the operational amplifiers 117 and 118 are very large.

Next, the operation of the circuit shown in FIG. 1 will be explained.

The D/A converters 3 to 5 convert digital data indicating voltage values sent from the microprocessor sensor 1 into analog voltages V2 to V, respectively. Among these, ■2 is
It is input to the input voltage terminal Vi of the corresponding voltage/current conversion circuit 12. Further, the D/A converter 4 converts the digital data indicating the voltage value sent from the microprocessor 1 into an analog voltage (bias voltage), and converts this N voltage V3 and the output voltage V of the D/A converter 6. , and is manually input to the input terminal Vi of the voltage/current conversion circuit 11 via the adder 43. In this way, the voltages input to the voltage/current conversion circuits 11.12 are individually controlled, and these voltage/current conversion circuits 11.1
The two output currents are set to be Im and In, respectively.

Output terminal ■ of the voltage/current conversion circuit 11.12.

are logically connected as shown in FIG. 1, so the current IL supplied to the semiconductor laser 20 is the sum of the respective currents as shown below.

IL = I, l XS-+1. (Sφ is zero or 1) Since the input control terminal (switching terminal) Di of the voltage/current conversion circuit 12 can ON/OFF control the output current,
From the equations of the current rot and the current (2), the current (1) is determined by the following equation.

It = S φ・Vz / R10+ Vm / R
IO Here, Sφ represents the ON/OFF state of the manual control terminal Di of the voltage/current conversion circuit 12, and when the input control terminal Di is at a high level, Sφ=1, and when the input control terminal Di is at a low level. At times, Sφ=φ, and the current IL is controlled according to the input pulse signal to the input control terminal Di. Here, the value of the resistor RIO of the current/voltage conversion circuit 11.12 determines the maximum current that the current/voltage conversion circuit 11.12 can drive, so the resistance values of the current/voltage conversion circuits 11 and 12 may be different.

By the way, the current of the semiconductor laser 20 in this embodiment is
The optical output characteristics are shown in FIG. 10, and the respective output voltages corresponding to the optical output P l + P W + P wrmx of the photodiode 21 for monitoring the amount of light (light output) are Let Vah*xH.

Therefore, for example, when the output light amount of the semiconductor laser 20 is Pl, the photodiode 21 outputs the voltage ■□.

Further, the data Dφ~ input to the data latch circuit 2
D8 is image data, Dφ is the least significant bit (LSB),
D8 is the most significant bit (MSB), and based on this 9-bit data, 25
6 (2') gradations, 32 gradations by optical output modulation, total 2
Performs 88-gradation laser light energy adjustment.

The input image data Dφ to D8 are the pixel clock signal CLK.
(synchronization signal) is captured in synchronization with the rising edge of the signal. This input image data is latched by the data launch circuit 2 because the input image data Dφ is sent from the outside.
This is to compensate for the difference in the rise of D8. Further, the LON signal output from the microprocessor 1 is input to the select section 15, and if the LON signal is at a low level, the input control terminal Di of the voltage/current conversion circuit 12 is at a high level. That is, the semiconductor laser 20 is supplied with more current than the current/voltage conversion circuit 12 .

Next, the control operation of the microprocessor 1 and the operation of this embodiment will be explained with reference to the flowchart shown in FIG.

First, before exposing the sensitive material with a laser (printing operation), that is, before outputting image data, the microprocessor 1 sets the outputs of the D/A converters 3 to 5 to 0■, and turns the LON signal on. The input control terminal Di of the voltage/current conversion circuit 12 is set to a low level as a high level. Furthermore, the MPX 45 is switched to the microprocessor 1 side, and the microprocessor 1 outputs the MPXRESET signal to set the output of the MPX 45 to zero. As a result, the input data of the D/A converter 6 becomes zero and the D/A
The output of converter 6 is made to be OV (step 31).

At this time, the input voltage V of the voltage/current conversion circuit 11.12
Note that when V z = V m = O, the current 1 flowing through the semiconductor laser 20 becomes zero.

Subsequently, only the output voltage V of the D/A converter 4 is increased by a predetermined value (step 32).

At the same time, the microprocessor 1 is connected to the A/D converter 8.
The voltage V,4 from the photodiode 21 is monitored via the photodiode 21. When the semiconductor laser 20 emits light, a current flows through the photodiode 21, and the photodiode 21 and the resistor R5
Since a positive voltage V,4 is generated at the contact point with the microprocessor 1, by measuring this voltage VM,
The amount of laser light (light output) of the semiconductor laser 20 can be determined.

The microprocessor 1 monitors the voltages V, 4 and outputs the output Vz (=Vs; V, =Q) of the D/A converter 4.
gradually increase. Since the input control terminal Di of the voltage/current conversion circuit 11 is always at a high level, at this time, 1
．． =Vl (V3)/RIO current is the semiconductor laser 20
flows to When the semiconductor laser 20 emits light according to the optical output characteristics shown in FIG. ■Stop the rise control in step 3. Therefore, the set value VIIM is the 10th
Photodiode 21 corresponding to optical output P8 in the figure
Therefore, the semiconductor laser 20 generates an optical output Pg. The current IL flowing through the semiconductor laser 20 at this time corresponds to the bias current 8 in FIG.

Next, the microprocessor 1 maintains the voltage vt at a value equivalent to the optical output Pw! , is supplied to the semiconductor laser 20, the LON signal is set to low level (step 34).

At this time, a high level signal is input from the select section 15 to the input control terminal Df of the voltage/current conversion circuit 12 (Sφ becomes 1), and the output terminal I0 of the voltage/current conversion circuit 12
A current flows through the semiconductor laser 20, and the current IL flowing through the semiconductor laser 20 is expressed by the following equation.

IL=Vz/R10+ Is (However, I,=V,/R
IO) Next, the microprocessor 1 converts the voltage ■ output from the photodiode 21 via the A/D converter 8 into
While monitoring, this voltage vN is set to a predetermined value (1). l, reaches 1 (value equivalent to optical output Pw), D/
The output voltage 2 of the A converter 5 is gradually increased (step S5, step S6).

When the voltage (a) reaches the predetermined value V, the voltage is determined by the sum of the voltage (i) 3 corresponding to the first output PI output from the D/A converter 4 and the voltage (i) 2 output from the D/A converter 5. This means that the predetermined value V has been obtained; in other words, the D/A converter 4 has produced a light output of 23 minutes (current ■,
), the D/A converter 5 further converts P, 4-P,
This means that the output of the current flow is controlled.

Next, the voltage V output from the D/A converter 4.5,
, V, is held at the constant value obtained up to step 6, and the microprocessor 1 sends an MPXSET signal to the MPX45 to set the input data to the D/A converter 6 to the same data as when inputting the maximum image data. Outputs
Set MPX45 output to maximum image data), D/
The output voltage V4 of the A converter 3 is gradually increased, and the voltage V,1 is the optical output P. When the output voltage V4 reaches a predetermined value V□ corresponding to
8. S9).

As described above, the output voltages of the D/A converters 3 to 5 are adjusted to the preset optical outputs P, , P of the semiconductor laser 2o.
, , P, (see FIG. 10) are adjusted to the values that can be obtained, so fluctuations in the optical output due to variations in the temperature and characteristics of the semiconductor laser 20 can be prevented, and stable optical output can always be obtained. In other words, the voltage value (current value) required to obtain a predetermined optical output can be set in advance, but if there are temperature changes or variations in characteristics, it may not be possible to obtain the desired optical output with the initially set voltage. Since there is a photodiode 21
The actual optical output of the semiconductor laser 20 is monitored, and the voltage value at which the desired optical output is actually obtained is determined.

Next, in step 5, the microprocessor 1 sets the LON signal to high level and sets the MPX 45 to the subtracter 41 side.
10) The image data reading and printing operation is started (step 5ll). At this time, the input image data of Dφ to D8 is transferred to the data latch circuit 2 and the generator section 16.
．． Cancellation part 17. The light passes through the selection section 15 and is converted into exposure energy (emission energy) of 288 steps. In this embodiment, the configuration is such that 256 (2 @) steps are obtained by pulse width modulation, and the exposure energy for the remaining 32 steps is adjusted by current value control, and the above pulse modulation and current value control (light amount modulation) total of 28
This is so that 8-step gradation can be obtained.

Among input data Dφ to D8, lower 8 pins Dφ to D7
is used for pulse width identification, and the input image data is 256
Until the image data exceeds 256, the gradation corresponding to the input image data is obtained based on pulse modulation, and when the image data exceeds 256, the bias current is increased as described later.

Next, the generator section 16 will be explained in detail.

The generator section 16 has a function of roughly dividing the pixel clock signal CLK (synchronization signal) into 16, and divides the pixel clock signal CLK (synchronization signal) into 16 different pulse widths based on the upper 4 bits D4 to D7 of the lower 8 bits for pulse width recognition. make.

FIG. 11 shows a circuit example of this generator section 16, in which the generator section 16 includes flip-flop circuits 51a to 51.
f, 4-bit binary down counter 52. NAND circuit 53. It is composed of a NOR circuit 54 and the like.

Also, in order to divide the pixel clock signal CLK into 16,
A clock 16×CK, which is 16 times the pixel clock CLK, is used. 16 times the clock 16XcK
For example, if a 16 frequency divider (not shown) is used to generate the pixel clock CLK (synchronization signal), a clock (high frequency signal) that is 16 times the pixel clock is naturally required, so it is not possible to use this. Yes, but the pixel clock CL
When there is no KL, the PLL (
phase-locked loop), 16 times the clock 1
Generating 6XCK is easy. Alternatively, if you ignore the synchronization relationship (phase) between the pixel clock CLK and the 16x clock 16XCK, it is possible to independently use the pixel clock CLK.
A crystal oscillator that generates a clock 16 times as large as 16 may be used.

The generator section 16, as shown in FIG.
~D7 is loaded into the counter, and the carry after down-counting is input to the flip-flop 51e, and as shown in FIG.
1d and the NAND circuit 53 to create the rise control signal Jin of the divided pulse out pis,
Further, the divided pulse o is generated by the NOR of the output of the flip-flop 51e and the rise control signal Jin.
A falling control signal Kin of ut pis is generated. 1st
The example in FIG. 3 is a time chart when "3" is input in D7 to D4.

Then, it is possible to obtain pulse widths of 16 steps as shown in FIG. 14, which correspond to the values of φ to 15 indicated by the 4 bits of image input data D4 to D7, respectively.For example, rD7. D6°D5. D4J is [φ,
1. 1. When it is IJ, a divided pulse out pis having a pulse width of 2 of the pixel clock CLK is output. Here, the minimum pulse width after division is 1/1
6CLK, and increases in increments of 1/16CLK until the maximum remains at CLK (16/16CLK). Note that the pulse width division in the generator section 16 is as follows:
It is clear that the division is not limited to 16 divisions.

Next, details of the canceling unit 17 will be explained.

FIG. 15 shows an example of the circuit of the canceling section 17, and the minimum created by the generator section 16 is 1/16 CL.
The divided pulse out pis of 16 steps is K,
Furthermore, the delay line 61 is used to subdivide into 16 divisions, thereby increasing the number of pulse width modulation steps to 16 x 16.
= 256 steps. Therefore, the delay time between each tap of the delay line 61 is 1/16X1/16C
LK=1/256 CLK.

The delay line 61 outputs the divided pulse out pis (basic pulse width) and the τ pulse (high frequency signal) separately from the generator section 16, as shown in FIG.
It is delayed in 6 ways (tl-tl5), and Da
Input image data Dφ by ta5elector62
One of the delayed pulses t2 to t15 is selected according to the value of ~D3, and finally, as shown in FIG. 17,
Divided pulses created by the generator section 16 out pi
s is further subdivided into 16 ways, and the input divided pulse out pis is canceled (erased) with an accuracy of CLK/256. In the example of FIG. 16, D3 to D
This is a case where “2” is input to φ and t3 is selected by the data selector 62.

That is, the canceling unit 17 calculates the logical sum B of the delayed pulse A selected according to the values of the image data Dφ to D3 and the τ pulse, and calculates the logical sum B and the generator unit 16.
By taking the conjunction with out pis from
Cut the out pis with CL K/256 precision.
This is a further subdivision of tpis.

Without using such a method, for example, FIGS. 18 and 19
As shown in the figure, delay line output and pixel clock C
A method of performing a logical sum OR or a logical product AND with the LK or basic pulse signal (out pis) (Japanese Patent Laid-Open No. 56-15
2373, JP-A-63-296558, etc.)
In this case, since the basic pulse always requires a rising or falling edge, it is no longer possible to subdivide using a delay line at the minimum or maximum pulse width. This may result in a decrease in image quality.

For example, as in this embodiment, 1 in the generator section 16
At the 6-division stage, image input data D4 to D7 are divided into "1.1,1
．． 1, a high level signal is output continuously for one pixel clock (see FIG. 14), so there is no edge in the pulse width. Therefore, the method of ORing or ANDing the delay line output and the pixel clock CLK or the basic pulse width signal cannot delay the pulse, and D4 to D7 are r
l, 1° 1.1'', it becomes impossible to subdivide further.

In other words, the image input data D4 to D7 are "φ, φ2φ, φ
”~rl, 1,1. φ" and there is a rising or falling pulse during the 100-element clock CLK, it is possible to subdivide it by the number of taps of the delay line, but rl, 1.1. Since the above-mentioned subdivision cannot be performed at the time of IJ, a jump occurs in the change in pulse width.

Conversely, if a low level is output for one pixel clock CLK when D4 to D7 are "φ, φ, φ, φ", D
4-D7 are rl, 1. 1. 1. So 15/16
It becomes a high-level pulse between CLK and K, and the pulse width can be subdivided using 15/16 edges.
φ, φ, φ” are at a low level during one pixel clock CLK and there is no pulse (there is no edge), so subdivision is impossible at this point.

Therefore, in this case "φ, φ, φ, ■" ~ ri, i.

1.1", it is possible to subdivide using daylay lines, but
Since this cannot be done with "φ, φ, φ, φ", there will still be a jump in pulse width modulation.

Incidentally, examples of the former are shown in FIGS. 20(a) to (d),
Here, in order to simplify the explanation, four types of basic pulse widths (corresponding to the out pis output from the generator section 16) (1/4CLK, 2/4CLK, 3/4
CLK, ICLK).

On the other hand, in the method of subdividing the pulse width as in this embodiment, the basic pulse width (subdivided pulse out pls in the generator section 16) is not delayed, and the time corresponding to the minimum resolution of the basic pulse width (in this embodiment In the example, 1/16c
The above problem is solved by delaying the pulse width of LK). That is, as shown in FIG.
Even if ~D7 are all 1 and the divided pulses out pis outputted from the generator section 16 are continuously at high level, the OR of the pulse signal τout and the delay pulse outputted simultaneously from the generator section 16. By taking , the pulse width can be subdivided by the number of taps of the delay line.

In this embodiment, the basic pulse width out pls is removed (erased) by taking the AND of the delayed pulse B shown in FIG. 15 and the basic pulse width out pis. Based on the hardware configuration shown in FIG. 22, as shown in FIG. 23, the delay pulse B and the basic pulse width out pis are ORed.
In this case, contrary to the example shown in FIG.
'', it becomes low level for one pixel clock CLK, and it can be applied to the case of 15/16 CLK with rl, 1° 1, ■''.

In addition, in the above examples, the basic pulse width outpls
Although the pulse width is changed by increasing or decreasing the O trailing edge (falling edge), it is clear that the same thing may be done at the leading edge (rising edge).

It has been explained above that the pulse width out pis divided into 16 by the generator section 16 is further divided into 16 by the canceling section 17 to perform pulse width modulation of 256 steps.

Next, the selection section 15 will be explained. Select section 15
Then, the pulse width modulation signal from the canceling unit 17 is output as is as Sφ while the input image data corresponds to the pulse width modulation region, and the semiconductor laser 20 is outputted via the voltage/current conversion circuit 12. Pulse width modulation is performed with the optical output of . When image data such that the required exposure energy cannot be obtained even with the maximum pulse width is input, the output of the decoder 42 becomes high level, and the S during one pixel time is input.
φ becomes high level, and the voltage/current conversion circuit 12 supplies a current of 1.0 to the semiconductor laser 20 during the maximum pulse (one pixel time). flow.

Further, subtraction data between the input image data and the set value (input image data corresponding to the switching timing between pulse width modulation and optical output modulation) is input to the D/A converter 6 via the MPX 45. Therefore, the bias current I increases or decreases depending on the input image data. At this time,
I7 is always ON, and as a result, the optical output is P as shown in FIG.

to Pl is variably controlled according to the input image data.

Note that when controlling the light output as described above, the exposure time is constant for one pixel time. In the above example, the bias current Is is always applied to the semiconductor laser 20, but it is also possible to set the bias current I to zero and to absorb this current (1) into the current 1w during pulse width modulation. That is, L+I in FIG.

New 1. The voltage is then supplied to the semiconductor laser 20 by the voltage/current conversion circuit 12. During optical output modulation, the summed current of the voltage/current modulation circuits 11 and 12 is supplied to the semiconductor laser 20.

In the above example, the generator section 16. Cancellation part 17
．． Although a power of 2 state is assigned to the select section I5, the present invention is not necessarily limited to this. for example,
6 stages in the cancel section 17, 13 stages in the generator section 16
In terms of stages, 6<23=8.13<2'=16, so 3-bit and 4-bit data should be given to each stage. In this case, as shown in Figure 24,
Prepare a conversion table (LUT) configured with ROM etc.
Input image data Dφ to D6 are converted to Dφ' to D6'. That is, as shown in FIG. 25, the input image data may be changed in such a way that the converted data increases at a pitch corresponding to a hexadecimal number (cancellation section 17) and a decimal number (generator section 16) above it. .

In addition, the input control terminal Di of the voltage/current conversion circuit 11 for the bias current I is inputted with the logical sum of Dφ to D8 instead of Vcc, so that all the input image data is “φ
'', the bias current (2) may be turned off.

According to the first embodiment described above, the final number of gradations is determined as the sum of the gradation by pulse width modulation and the gradation by optical output modulation, so the same number of gradations is obtained by modulating only one of them. Compared to the case, there is no need to finely control the pulse width or optical output. Furthermore, since the optical output is modulated over a wider range than the optical output that is held at a constant value when pulse width modulation is performed, monotony of concentration can be ensured.

In the first embodiment, as shown in FIG. 1, the voltage/current conversion circuit 11 for bias current is separately provided, but when the bias is zero, the second embodiment shown in FIG. By integrating the voltage/current conversion circuits 11 and 12,
It is also possible to configure only the voltage/current conversion circuit 12. In FIG. 26, the same elements as in FIG. 1 are given the same reference numerals.

In the circuit configuration shown in FIG. 26, compared to the configuration in FIG.
The voltage/current conversion circuit 11 is omitted, the D/A converter 4 for bias current control is omitted, and the output voltage V2 of the D/A converter 5 for optical output control is changed to the output voltage of the D/A converter 4. , is input to the adder 43 instead of , and the output voltage V of the adder 43 is input to the voltage/current conversion circuit 1.
It is input to the vi terminal of 2.

In this configuration, in the input image data area (first stage) in which gradation is obtained by pulse width modulation, a pulse width modulation signal is outputted from the selector 15 to the input control terminal Di of the voltage/current conversion circuit 12, and the optical output is D/A converter 5
As shown in FIG. 27, the constant optical output P is fixed at Pw. The pulse width (emission time=exposure time) is modulated according to the human image data while holding the pulse width. In addition, when the exposure energy (density) corresponding to the input image data cannot be obtained even if the light output P is emitted for one pixel clock, as a second step, as shown in FIG.
The optical output of the semiconductor laser 20 is converted to P via the converter 6.

It increases or decreases from to P wax.

Furthermore, in the optical output modulation region shown in FIG. 10, when the optical output change with respect to the current change is linear, Japanese Patent Application Laid-Open No. 63-1
Publication No. 84773 or the patent application filed earlier by the applicant
As shown in Japanese Patent No. 55145, optical output modulation can be performed by using a plurality of voltage/current conversion circuits in combination based on predetermined weighting. In other words, it has a plurality (N) of voltage/current conversion circuits connected in parallel, and modulates the optical output in 2N ways by combining these voltage/current conversion circuits in the second stage after pulse width modulation. The circuit configuration of the third embodiment is shown in FIG. 29. In FIG. 29, the same elements as in FIG. 1 are given the same reference numerals.

In the circuit configuration shown in FIG.
φ is input and pulse width modulation is performed.The difference from the first embodiment shown in FIG. 23=8 different optical outputs can be obtained.

Therefore, the first stage of pulse width modulation is the same as the first embodiment, but the second stage of optical output modulation is as follows:
The voltage/current conversion circuit 10 subtracts the numerical value of the image data (stored in the setting value 40) corresponding to the switching point between the stage and the second stage from the input image data.
~12, respectively. In addition, voltage/current conversion circuit 1
As shown in the figure, the subtraction results output to 0 to 12 respectively have Aφ as LSB and A2 as MSB.

In the third embodiment shown in FIG. 29, the image data corresponding to the switching point stored in the setting value 40 is
At FH, the maximum input value is 255+23-1=262. For example, if the input image data is 260, A
φ~A2 is rl as shown in FIG. 30, 0°I J =
5 = 260-255 is output.

Here, for example, a semiconductor laser 20 as shown in FIG.
In the characteristics, Pl is the bias optical output and P.

Assuming that P is a constant optical output during pulse width modulation and P mm x Pw is an optical output modulation area, optical output modulation is performed by three voltage/current conversion circuits 10 to 12, but the voltage/current conversion circuit 1
2 is (P, , -P,)/8, voltage/current conversion circuit 1
1 is (P, , -P,)/4, voltage/current conversion circuit 1
Assuming that the semiconductor laser 20 can output a current that can output an optical output of (P, , -PW)/2, the relationship between the manual image data and the optical output is as shown in FIG.

Further, the Adjust circuit 46 in FIG. 29 is used to forcibly turn on the semiconductor laser 20 when the microprocessor 1 initializes each D/A converter 3 to 6. The circuit configuration is as shown in FIG. 32.

The initial setting program for the above D/A converters 3 to 6 is
This is shown in the flowchart of FIG.

The flowchart shown in FIG. 33 is basically the same as the flowchart shown in FIG. 2, but the number of processing steps is increased due to the increase in the number of D/A converters to be set. In the program shown in the flowchart of FIG. 33, for example, in S22, the voltage V14 is compared with V14.
■ in lllN+ L<twallg-pw)is
? (P+es Kan-Pw)/l is the first cuff (P,-pw
)/8.

By the way, if the region in which the optical output is modulated is not the linear region of the semiconductor laser 20 as shown in FIG. 34, the desired gradation cannot be obtained by modulating the optical output by current addition as described above. Therefore, in this case, by interposing an attenuator as a light quantity attenuation means in the optical path and reducing the efficiency of the optical system, the optical output control range of the semiconductor laser 20 is increased as a whole, and the optical output is reduced in the linear region. Output modulation can be performed.

As shown in FIG. 34, when the area initially set as the use area is a nonlinear area, P is the modulation switching point of the optical output. In order to move -0.1 mW to the linear region of 0.51 or more, an attenuator (filter) with a transmittance of 0.110.5 = 20% or less is inserted in the optical path.
P to ensure the same exposure energy as without an attenuator. can be shifted to 0.5 mW or more. This allows optical output modulation to be performed by the semiconductor laser 20.
The desired gradation can be obtained by performing this in the linear region of .

<Effects of the Invention> As explained above, according to the present invention, the emission energy (grayscale) of the semiconductor laser is adjusted in multiple stages by the emission time (supply current pulse) modulation and the optical output modulation, and by each modulation, Since the final adjustment step is obtained as the total obtained, compared to the case where the light emission energy is adjusted only by controlling the light output, it is possible to achieve higher accuracy and reduce costs by not requiring an A converter etc. There is no need to set the adjustment unit time in detail, unlike when adjusting the emission energy only by emission time modulation. In addition, when controlling the light emission time, the light output is kept constant, and when controlling the light output, the light output is increased beyond the above-mentioned constant light output, so that the uniqueness of each light emission energy adjustment (monotony of concentration) is ensured. When applied to a laser printer, faithful density reproduction can be achieved.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing the entire system in the first embodiment of the present invention, FIG. 2 is a flowchart showing control details in the same embodiment, and FIG. 3 is an example of the circuit configuration of the voltage/current conversion circuit shown in FIG. 1. 4 is a diagram showing the relationship between the current supply time (pulse width) to the semiconductor laser and the density obtained on the sensitive material in the same example as above, and FIG. 5 is a diagram showing the optical output of the semiconductor laser and the density. FIGS. 6 and 7 are diagrams showing the basic control characteristics of the semiconductor laser driving device according to the present invention, and FIGS. 8 and 9 are diagrams showing the basic control characteristics of the semiconductor laser drive device according to the present invention, respectively. FIG. 10 is a diagram showing the control characteristics in the first embodiment in terms of the relationship between current and optical output; FIG. 11 is a circuit diagram showing an example of the circuit of the generator section shown in FIG. , FIG. 12 is a block diagram showing an example of a PLL circuit that can be used in the first embodiment, FIG. 13 is a time chart showing control characteristics of the generator section shown in FIG. 11, and FIG. FIG. 15 is a circuit diagram showing an example of the circuit of the canceling section shown in FIG. 1, and FIG. 16 is a time chart showing the control characteristics of the canceling section shown in FIG. 15. , FIG. 17 is a comparison diagram showing input data and conversion results for the control characteristics shown in FIG. 16, FIG. 18 is a circuit diagram showing another example of the pulse width dividing device, and FIG. 19 is a circuit diagram showing the circuit shown in FIG. 18. 20(a) to (d) are time charts for explaining problems in the pulse splitting device compared to the first embodiment, and FIG. 21 is a time chart showing the control characteristics of the first embodiment. Time chart showing pulse width division characteristics in 2nd
2 is a circuit diagram showing another circuit example of the cancellation circuit shown in FIG. 1, FIG. 23 is a comparison diagram showing input data and conversion results in the circuit shown in FIG. 22, and FIG. 24 is a circuit diagram showing the circuit configuration shown in FIG. 1. 25 is a comparison diagram showing the conversion table shown in FIG. 24; FIG. 26 is a circuit diagram showing the entire system in the second embodiment of the present invention; FIG. 27 and FIG. 28 are diagrams showing the control characteristics in the second embodiment, respectively.
FIG. 9 is a circuit diagram showing the entire system in the third embodiment of the present invention, FIG. 30 is a comparison diagram showing the relationship between input data and optical output value in the third embodiment, and FIG. A diagram showing the characteristics of light output control in a contrasting relationship between current and light output, FIG. 32 is the Ajus shown in FIG. 29.
A circuit diagram showing the circuit configuration of the t circuit, FIG. 33 is a flowchart showing control details in the third embodiment of the same, and FIG. 34 is a diagram showing the relationship between the optical output control range and the linear/nonlinear region of the semiconductor laser. , Fig. 35 is a diagram showing the relationship between current and optical output in a semiconductor laser according to temperature, Fig. 36 is a block diagram showing an example of a conventional semiconductor laser driving device, and Fig. 37 shows problems in the conventional driving device. FIG. 38 is a diagram showing the characteristics of the linear and non-linear regions of the semiconductor laser, and FIGS. 39 and 40 are diagrams of conventional semiconductor lasers that perform both light emission time control and optical output control, respectively. FIG. 41 is a circuit diagram showing a specific example of the MPX shown in FIG. 1, and FIG. 42 is a circuit diagram showing a specific example of the select section shown in FIG. 1. 1... Microprocessor 2... Data latch 3-6... D/A converter 8... A/D converter 11.12... Voltage/current conversion circuit 1
5...Select section 16...Generator section
17... Cancellation part 20... Semiconductor laser
21...Photodiode 40...Setting value
41...Subtractor 42...Decoder 43.
...Adder 45...MPX Fig. 14 Fig. 22rI! J Figure 32 41 Figure 34 Figure 35 Figure 36

Claims (1)

[Scope of Claims] (1) A semiconductor laser driving device that adjusts the light emission energy of a semiconductor laser in multiple stages by controlling the light emission time and light output, the light output of the semiconductor laser being constant until a predetermined light emission energy. The light emission energy is adjusted by holding the light emission time at a value and variably controlling the light emission time within the maximum light emission time, and when the light emission energy exceeds the predetermined light emission energy, the light emission time is fixed at the maximum light emission time and the light output is controlled to increase beyond the above certain value. 1. A semiconductor laser driving device characterized in that the device is configured to adjust emission energy by adjusting the emission energy. (2) The semiconductor laser driving device according to claim 1, wherein the semiconductor laser driving device is configured to increase the optical output of the semiconductor laser by controlling the increase in the bias optical output. (3) In the semiconductor laser driving device according to claim 1,
1. A semiconductor laser driving device characterized in that the optical output of the semiconductor laser is controlled to increase by selectively switching and controlling a plurality of semiconductor laser current sources connected in parallel. (4) An optical output attenuation means is interposed in the optical path of the semiconductor laser, and when controlling the optical output and adjusting the emission energy, the optical output is controlled in a region where the optical output is linear with respect to changes in the supplied current. Claim 1 characterized in that:
, 2 or 3. The semiconductor laser drive device according to any one of .