JPH0593876A - Optical scanning recording device - Google Patents

Abstract

(57) [Abstract] [Purpose] To enable main scan synchronization detection and control with no line omissions and reduced synchronization deviation. A rotary polygonal mirror 3 for deflecting a light beam modulated by a recording light source 1 in accordance with an image information signal by a certain angle, an imaging optical system 4 for forming an image of the deflected light on a photoconductor, and a deflected light A part of the light rays outside the image writing range within the light receiving element 6 for synchronization.
Sync detection means 1 for binarizing a photoelectric conversion signal obtained by detection by a predetermined threshold value and outputting a main scanning synchronization signal.
2 and a light source control means 9 for changing the recording light source 1 to an optical output corresponding to at least two or more writing densities. In the optical scanning recording apparatus, a threshold for binarizing the synchronization detecting means 12 is set. Instead of being fixed, the binarization threshold setting circuit 13 is made variable according to the change of the optical output of the recording light source 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical scanning recording device such as a laser printer, a digital copying machine and a laser facsimile.

[0002]

2. Description of the Related Art Generally, as shown in FIG. 8, an optical scanning recording apparatus of this type rotates a polygon mirror after collimating a light beam emitted from a recording light source such as a semiconductor laser 1 by a collimator lens 2. After being deflected at a constant angle by one reflecting surface 3 of 3, an fθ lens 4 as an imaging optical system forms an image on the photoconductor 5 to form an electrostatic latent image. Here, the semiconductor laser 1 is modulated in accordance with an image information signal, is main-scanned on the photoconductor 5 by the rotary polygon mirror 3, and is sub-scanned by the rotation of the photoconductor 5, thereby
A dimensional writing record is made. In such an operation, since the main scanning direction is synchronized for each main scanning, a part of the deflected light deflected by the rotary polygon mirror 3 is received outside the image range in the main scanning direction (outside the photoconductor 5). The synchronizing light receiving element 6 is provided. The photoelectric conversion signal detected and obtained by the synchronizing light receiving element 6 is binarized by a threshold value (those set at the time of assembly adjustment of the device) in the comparator, and is used as a main scanning synchronization signal of the electrical scanning recording device. It is output to the control system. Such a synchronization method is disclosed in, for example, Japanese Patent Laid-Open No.
No. 2-44712, etc.

As described above, the optical scanning recording apparatus combining the electrophotographic technology and the laser scanning technology can use plain paper and can obtain high-quality images at high speed. Therefore, the optical scanning recording apparatus can be used as an output device of a computer or a digital copying machine. It is becoming popular rapidly.

Under such circumstances, there is one that enables recording with a plurality of writing densities and halftone recording with the same optical scanning device so that a higher quality image can be obtained.

[0005]

Here, for example, when recording with two or more writing densities using the same optical scanning device, it is essential to change the optical output of the semiconductor laser 1 in accordance with the change of the writing density. is there. In the case of halftone recording, it is essential to change the light output by changing at least one of the light emission time (light emission pulse width) and the light emission intensity of the semiconductor laser 1 in accordance with the density information included in the image information signal. At this time, the amount of light received by the synchronizing light-receiving element 6 installed outside the image range also changes according to the change in the optical output of the semiconductor laser 1. In this state, when the photoelectric conversion output of the synchronization light receiving element 6 is binarized by a certain threshold value (binarization level) to generate the main scanning synchronization signal, as shown in FIGS. 9 (a) and 9 (b). In addition, the signal length of the main scanning synchronization signal changes remarkably in accordance with the change in the light amount, and in the worst case, the photoelectric conversion output of the synchronization light receiving element 6 falls below the threshold value, as shown in FIG. The main scanning synchronization signal is not generated, and lines may be missing in the recorded image.

In this respect, it is possible to avoid the situation in which the main scanning synchronization signal is not generated by setting the threshold value to the minimum value of the optical outputs corresponding to all the writing densities, but the main scanning synchronization signal has the same signal length. There is an adverse effect such as an increase in the change, the circuit configuration becomes complicated in the electric control system (for example, a signal length fixing process by differentiation is required), and recording is performed with a plurality of writing densities in the same screen. In this case, the phase in the main scanning direction may shift due to a change in the main scanning synchronization signal length, which may cause a synchronization shift in the recorded image.

Incidentally, for example, Japanese Patent Publication No. 61-51822.
As disclosed in Japanese Patent Publication No. JP-A-2003-264, there is also a method of correcting the light amount at the time of detecting the main scanning synchronization signal by sampling and holding the signal level detected by the light receiving element and comparing it with a preset threshold value. Is a system that lacks high-speed response because it corrects the light amount after detecting light, and the above-mentioned problems may occur if the threshold setting is not appropriate, and a device that can change the writing density. Is not applicable to.

[0008] Such a situation also applies to the case where halftone recording is possible.

[0009]

According to a first aspect of the present invention, there is provided at least one recording light source and a photoconductor, and a light beam obtained by modulating the recording light source according to an image information signal is deflected at a constant angle. And a rotating polygon mirror, an imaging optical system for forming an image of the deflected light on the photosensitive member, and a part of the deflected light outside the image writing range is detected by a light receiving element for synchronization. A synchronization detection unit that binarizes the photoelectric conversion signal with a predetermined threshold value and outputs a main scanning synchronization signal, and a light source control unit that varies the recording light source to an optical output corresponding to at least two or more writing densities. In the optical scanning recording apparatus, a binarization threshold value setting circuit for varying the threshold value for binarization of the synchronization detecting means according to the change of the optical output of the recording light source is provided.

In this case, in the invention described in claim 2, there is provided a signal length fixing means for outputting the signal length of the main scanning synchronization signal as a substantially constant signal length. In the invention described in claim 3, for each writing density. A binarization threshold having storage means for storing the binarization threshold and output means for outputting the binarization threshold corresponding to the writing density signal for varying the optical output of the recording light source from the storage means to the synchronization detection means. The setting circuit.

According to a fourth aspect of the present invention, there is provided a rotary polygonal mirror which has at least one recording light source and a photoconductor, and which deflects a light beam modulated by the recording light source according to an image information signal by a certain angle. And an image forming optical system for forming an image of the deflected light on the photoconductor, and a photoelectric conversion signal obtained by detecting a part of the light beam outside the image writing range in the deflected light by the light receiving element for synchronization. Optical scanning recording provided with a synchronization detection unit which binarizes by a predetermined threshold value and outputs a main scanning synchronization signal, and a light source control unit which varies the recording light source to an optical output corresponding to at least two or more writing densities. In the device,
An optical output control means is provided for keeping the optical output of the recording light source at a constant value when the synchronization detection means detects the synchronization.

Similarly, in the invention described in claim 5, there is provided at least one recording light source and a photosensitive member, and the rotating polyhedral surface deflects the light beam modulated by the recording light source according to the image information signal by a certain angle. A mirror, an image forming optical system for forming an image of the deflected light on the photoconductor, and a photoelectric conversion signal obtained by detecting a part of the light beam outside the image writing range in the deflected light by a light receiving element for synchronization. Is binarized by a predetermined threshold to output a main-scanning synchronization signal, and the recording light source is made to perform halftone recording by changing at least one of a light emission time and a light emission intensity based on an image information signal. In the optical scanning recording apparatus provided with the light source control means, the optical output control means for controlling the light output of the recording light source at the time of synchronization detection by the synchronization detection means to a constant value is provided.

According to a sixth aspect of the present invention, in the fourth or fifth aspect of the present invention, the recording light source is a semiconductor laser, and the light output of the semiconductor laser is detected by the light receiving element and the light receiving element. An optical / electrical negative feedback loop that controls the forward current of the semiconductor laser so that the received light signal proportional to the optical output of the semiconductor laser and the emitted light level command signal become equal, and the received light signal and the light emission level command The light emission level based on the light output / forward current characteristics of the semiconductor laser, the coupling coefficient between the light receiving element and the light output of the semiconductor laser, and the light input / light receiving signal characteristics of the light receiving element so that the signals become equal. A conversion unit that converts a command signal into a forward current of the semiconductor laser,
The light source control means is composed of control means for controlling the semiconductor laser with a current that is the sum or difference of the control current of the optical / electrical negative feedback loop and the current generated by the conversion means.

[0014]

According to the first aspect of the present invention, the binarization threshold value is not fixed, but is changed according to the change in the optical output of the recording light source corresponding to the writing density. Even if the amount of received light of the light receiving element for use is changed, it does not disappear when the main scanning synchronization signal is generated by the binarization, and it is possible to prevent line omission during image output. Further, it is a binarization threshold value corresponding to a change in the optical output for writing, and a main scanning synchronization signal having substantially the same phase can be obtained, and the synchronization deviation of the recorded image is also reduced.

In particular, according to the second aspect of the present invention, the signal length fixing means is provided to output the signal length of the main scanning synchronization signal as a substantially constant signal length. Since it is possible to correct the variation of the signal length that cannot be compensated by the setting of the binarization threshold value, it is not necessary to perform the signal length fixing process by differentiation or the like in the electric control system. According to the third aspect of the invention, the binarization threshold value setting circuit corresponds to a storage unit that stores the binarization threshold value for each writing density and a writing density signal that varies the optical output of the recording light source. Since the binarization threshold value is output from the storage means to the synchronization detection means, the main scanning synchronization signal can be detected instantly when the writing density is changed, and the malfunction of the electrical control system can be prevented. And reliable control can be performed.

Further, according to the inventions of claims 4 and 5, the synchronization detection is performed without depending on the change of the recording density or the change of the light emission time or the light intensity of the recording light source for the halftone recording. Since the light output of the recording light source is always kept constant, it is possible to perform synchronization detection / control without line omission or synchronization deviation. In these cases, according to the invention of claim 6, since the semiconductor laser used as the recording light source is controlled by the semiconductor laser control means of high speed, high accuracy, and high resolution, the control accuracy of the optical output is high, so that the synchronization is achieved. Detection·
The control becomes more accurate, and high-speed, high-quality multi-value density recording and halftone recording are possible.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the invention described in claims 1 to 3 will be described with reference to FIGS. The apparatus configuration shown in FIG. 8 is used as it is. The present embodiment is applied to the one capable of recording with a plurality of writing densities by the same optical scanning device, and a writing density setting signal from a main body (not shown) is sent to the optical scanning device electric control system 7. The modulation frequency is set so as to obtain an optical output according to the input writing density, and the semiconductor laser 1 is variably controlled via the semiconductor laser (LD) driver 8. The light scanning device electrical control system 7 and the LD driver 8 constitute a light source control means 9. Further, the photoelectric conversion output of the light receiving element 6 is input to the comparator 10 having a reference voltage terminal to which a binarization threshold is input, and the binarized output is subjected to waveform shaping through the buffer 11 to generate a main scanning synchronization signal. The detection means 12 is configured. The main scanning synchronization signal (waveform shaping output) by the synchronization detecting means 12 is input to the optical scanning device electric control system 7.

In addition to such a basic configuration, in this embodiment, the binarization threshold value of the comparator 10 is also made variable in accordance with the change of the optical output accompanying the change of the writing density. A binarization threshold value setting circuit 13 that outputs a binarization threshold value corresponding to a signal to a reference voltage terminal of the comparator 10 is provided. In the binarization threshold setting circuit 13, it is preferable that the binarization threshold set in advance for each writing density is set so as to reduce the variation in the main scanning synchronization signal length.

In such a configuration, when the writing density setting signal is input from the main body to the optical scanning device electric control system 7 and the binarization threshold setting circuit 13, the optical scanning device electric control system 7 is inputted.
Then, the optical output is set according to the writing density, the semiconductor laser 1 is turned on through the LD driver 8, and the state of waiting for the input of the main scanning synchronization signal is set. On the other hand, the binarization threshold setting circuit 13
Then, the binarization threshold value set in advance according to the writing density is output to the reference voltage terminal of the comparator 10. When the light beam from the semiconductor laser 1 deflected by the rotary polygon mirror 3 and condensed by the imaging optical system 4 is detected by the light receiving element 6, the comparator 10 uses a binarization threshold value corresponding to the optical output at that time. Are binarized, and the waveform is shaped by the buffer 11 to become a main scanning synchronization signal, which is input to the optical scanning device electrical control system 7. When the main scanning synchronization signal is input, the optical scanning device electric control system 7 starts the phase synchronization operation in the main scanning direction, enters the recording preparation state, and waits for a writing command from the main body. When a write command is received, a write permission signal is generated, and the image information signal (Data) is received and recording is performed. Such an operation is similarly repeated for each main scanning line.

Therefore, according to the present embodiment, if the optical output changes according to the writing density, the binarization threshold is also changed correspondingly, so that proper and reliable synchronization detection can always be performed, There is no omission. Also,
Since the binarization threshold value is appropriately changed each time the light output is changed,
The phase shift is reduced in each synchronization detection.

By the way, in the present embodiment, as shown in FIG. 1, a monostable multivibrator which receives the waveform shaping output from the buffer 11 as an input and outputs a signal length constant output to the optical scanning device electric control system 7. There is provided a timer circuit 14 which is constituted by the above and serves as a signal length fixing means. As a result, the signal length of the main scanning synchronization signal is made substantially constant and output to the optical scanning device electrical control system 7, so that there is a variation in the synchronization signal length that cannot be compensated for by setting the binarization threshold value according to each writing density. Is corrected, and the signal length fixing process by differentiation or the like in the electric control system 7 of the optical scanning device becomes unnecessary.

In the present embodiment, the binarization threshold value setting circuit 13 is a rewritable nonvolatile memory as a storage means for storing the setting value of the binarization threshold value for each writing density, as shown in FIG. Threshold setting data storage memory 1
5 is used, and the D / A converter 16 is used as an output unit that outputs the binarized threshold value to the comparator 10. Therefore, the writing density setting signal output from the main body is converted into address data for reading the threshold setting data through the decoder 17, and the threshold setting data storage memory 15 is provided.
Input to the D / A converter 16, the threshold setting data storage memory 15 outputs the data of the designated address. The D / A converter 16 outputs the threshold voltage corresponding to the designated data as a binarization threshold to the comparator 10 and uses it for the above-described comparison for synchronization detection.

Therefore, such a binarized threshold value setting circuit 1
According to the configuration of 3, the main scanning synchronization detection by the binarization threshold value at a level corresponding to the optical output can be instantaneously performed when the writing density is changed, the malfunction of the optical scanning device electric control system 7 can be prevented, and the reliability can be improved. It is possible to detect and control high synchronization. In particular, since a rewritable non-volatile memory is used as the threshold setting data storage memory 15 here, the setting value of the binarization threshold value can be arbitrarily reset, so that the semiconductor laser 1, the rotary polygon mirror 3, the imaging optical system. It is possible to easily cope with a change in the optical output characteristic due to the change of 4 or the like, and the synchronization detection with high versatility is achieved.

Next, one embodiment of the invention described in claims 4 and 6 will be described with reference to FIGS. In this example,
The reference voltage terminal of the comparator 10 is provided with a preset predetermined binarization threshold value, and instead of the binarization threshold value setting circuit 13, a recording light source light output setting unit 18 serving as a light output control means is provided. It is a thing. Here, the recording light source light output setting unit 18 basically receives a writing density setting signal from the main body, sets an optical output according to the writing density, and outputs it to the optical scanning device electric control system 7. In addition, when the synchronization light-receiving element 6 detects synchronization, it also has a function of setting a value that always provides a constant light output regardless of the writing density at that time and outputting the value to the optical scanning device electrical control system 7.

The operation of the circuit shown in FIG. 3 will be described with reference to the timing chart shown in FIG. First, when the power is turned on, the electric control system 7 of the optical scanning device outputs the optical output setting signal / P. Sync (“/”
Indicates a bar ... The same applies to other signals below)
Is set to the L level (setting) and is output to the recording light source light output setting unit 18. In response to this, the recording light source optical output setting unit 18 outputs the optical output signal P. Set Set to the optical output for synchronous detection, and set the electric control system 7 for the optical scanning device.
Return to. In the electric control system 7 of the optical scanning device, the optical output signal P. Set to the optical output control signal P.P. The light is converted to Cont and output to the recording light source control unit (LD driver) 8 to turn on the semiconductor laser 1 with the light output for synchronization detection, and wait for input of the first main scanning synchronization signal / DETP. When the main scanning synchronization signal / DETP for the first time is input, the optical output setting signal / P. Sync is set to the H level (release), and the optical output signal P. Set the optical output according to the writing density and enter the recording preparation state. In this recording preparation state, the optical output setting signal / P. The optical output control signal P.P. The level of Cont is 0, and the semiconductor laser 1 is not turned on. After the second time, 1
Optical output setting signal /
P. Sync is set to the L level (setting) again, and thereafter, the same operation as the first time is repeated. At this time, the light output at the time of synchronization detection by the synchronization light receiving element 6 is always set to a constant value.

When the optical scanning device electric control system 7 enters the recording preparation operation, the line data output permission signal / L. Generate Gate. This line data output permission signal / L. Gate is L
The output of the line image information signal (Data) is permitted in the level state. Therefore, this period corresponds to the image recording width in the main scanning direction. However, the line data output permission signal / L. Even if the Gate is at the L level, the image recording permission signal / F. Until the Gate becomes L level (permitted), the optical output control signal P. No image information is output to Cont. When a recording start signal / Wrst (negative logic signal) comes from the main body, an image recording permission signal / F. Gate is set from the H level (prohibition) to the L level (permission), and the optical output signal P. The image signal of the light output corresponding to the writing density set by Set is the light output control signal P.P. It will be output to the Cont and recorded.

In such an operation, the optical output setting signal / P. Sync, line data output enable signal / L. Gate
, Image recording permission signal / F. Since all Gates are generated with reference to the main scanning synchronization signal / DETP, variations in the output timing and signal length of the main scanning synchronization signal / DETP are caused by these signals / P. Sync, / L. Gate, /
F. It appears as a variation in Gate. However, in this embodiment, since the optical output of the semiconductor laser 1 at the time of detecting the main scanning synchronization is a constant value that does not depend on the change in the writing density, etc.,
The variation of the main scanning synchronization signal / DETP is greatly reduced,
It is possible to detect and control synchronization without causing synchronization deviation or line omission.

Here, if the light output (constant value) of the semiconductor laser 1 at the time of main scanning synchronization detection is one of the light outputs set according to the writing density, the light output setting data is shared. Therefore, the configuration of the recording light source light output setting unit 18 can be further simplified. In particular, if the maximum light output is shared for synchronization detection, more reliable synchronization detection becomes possible.

In the present embodiment, the semiconductor laser 1 is used as the recording light source, but the light source control means 9 suitable for it is used.
The structure and operation of the semiconductor laser control circuit 8 therein will be described with reference to FIG. First, the light emission level command signal (corresponding to the light output control signal P.Cont) is input to the comparison amplifier 19 and the current converter (converting means) 20, and a part of the light output of the semiconductor laser 1 is monitored by the light receiving element 21. To be done. here,
The comparison amplifier 19, the semiconductor laser 1, and the light receiving element 21 form an optical / electrical negative feedback loop 22.
Reference numeral 9 compares the light receiving signal proportional to the photocurrent (proportional to the optical output of the semiconductor laser 1) induced in the light receiving element 21 with the light emission level command signal, and the result indicates the forward current of the semiconductor laser 1. The light reception signal and the light emission level command signal are controlled to be equal. Further, the current converter 20 uses a current preset according to the light emission level command signal such that the light reception signal and the light emission level command signal become equal (light output / forward current characteristics of the semiconductor laser 1, the light receiving element 21 and the semiconductor laser). Coupling coefficient with the optical output of 1 and the light receiving element 2
1), which outputs a preset current based on the light input / forward current characteristic of 1. The sum of the output current of the current converter 20 and the control current output from the comparison amplifier 19 becomes the forward current of the semiconductor laser 1 and is controlled.

Now, let us say that the crossover frequency in the open loop of the optical / electrical negative feedback loop 22 is f0 and the DC gain is 10000.
In this case, the step response characteristic of the optical output Pout of the semiconductor laser 1 is Pout = PL + (PS-PL) exp (where PL is the optical output at t = ∞ and PS is the amount of light set by the current converter 20). It can be approximated by −2πf0t). Here, since the DC gain in the open loop of the optical / electrical negative feedback loop 22 is 10,000,
When the allowable range of the setting error is 0.1% or less, the light output PL is considered to be equal to the set light amount. Therefore, if the light quantity PS set by the current converter 20 is P
If it is equal to L, the optical output of the semiconductor laser 1 is instantly PL
Is equal to Further, even if PS varies by 5% due to disturbance or the like, if f0 = 40 MHz or so, the error of the optical output of the semiconductor laser 1 with respect to the set value will be 0.4% or less after 10 nanoseconds.

By using such a high-speed, high-accuracy, high-resolution semiconductor laser control circuit 8, the light output of the light source (semiconductor laser 1) can be controlled with high accuracy, and thus the optical scanning recording apparatus with high main scanning synchronization accuracy. Becomes

Further, an embodiment of the invention described in claim 5 will be described with reference to FIGS. 6 and 7. In the present embodiment, at least one of the light emission time (light emission pulse width) and the light emission intensity of the semiconductor laser 1 is selectively variable based on an image information signal including density information, instead of changing the writing density as in the above-described embodiments. By doing so, the present invention is applied to an optical scanning recording apparatus that enables halftone recording. Therefore, the optical scanning device electric control system 23 of the present embodiment basically has the same configuration as that of the above embodiment, but the semiconductor laser 1 according to the image information signal.
The light emission time and the light emission intensity are set and output to the recording light source control unit 8, and the driving current of the semiconductor laser 1 is controlled to perform halftone recording. This optical scanning device electrical control system 2
In addition to the recording light source control unit 8 and the light source control unit 3, the optical scanning device electric control system 3 also serves as the optical output control unit 3.

The operation of the circuit shown in FIG. 6 having such a configuration will be described with reference to the timing chart shown in FIG. First, when the power is turned on, the electric control system 23 of the optical scanning device outputs the optical output setting signal / P. Sync is set to L level (setting), and the optical output control signal P. Cont is set to the light output at the time of synchronization detection and output to the recording light source control unit 8, the semiconductor laser 1 is turned on by the light output for the time of synchronization detection, and the first main scanning synchronization signal / DETP input waiting state is set. stand by. When the main scanning synchronization signal / DETP for the first time is input, the optical output setting signal / P. S
Set ync to H level (release) and enter the recording preparation state. In this recording preparation state, the optical output setting signal /
P. The optical output control signal P.P. Con
The level of t is 0, and the semiconductor laser 1 does not light up.
After the second time, the optical output setting signal / P. Sync is set to the L level (setting) again, and thereafter, the same operation as the first time is repeated. At this time, the light output at the time of synchronization detection by the synchronization light receiving element 6 is always set to a constant value.

When the optical scanning device electric control system 23 enters the recording preparation operation, the line data output permission signal / L. Generate Gate. This line data output permission signal / L. The output of the line image information signal (Data) is permitted when Gate is at the L level. Therefore, this period corresponds to the image recording width in the main scanning direction. However, the line data output permission signal / L. Even if the Gate is at the L level, the image recording permission signal / F. Until the Gate becomes L level (permitted), the optical output control signal P. No image information is output to Cont. When a recording start signal / Wrst (negative logic signal) comes from the main body, an image recording permission signal / F. Gate is set from the H level (prohibition) to the L level (permission), and the line data output permission signal / L. Gate is converted into data for setting at least one of the light emission time and the light emission intensity of the semiconductor laser 1 in accordance with the image information signal output in the L level section, and this data is converted into the light output control signal P.P. Halftone recording is performed by superimposing and outputting on Cont.

In such an operation, the optical output setting signal / P. Sync, line data output enable signal / L. Gate
, Image recording permission signal / F. Since all Gates are generated with reference to the main scanning synchronization signal / DETP, variations in the output timing and signal length of the main scanning synchronization signal / DETP are caused by these signals / P. Sync, / L. Gate, /
F. It appears as a variation in Gate. However, in the present embodiment, the optical output of the semiconductor laser 1 at the time of detecting the main scanning synchronization is a constant value that does not depend on the image information signal (including the information on the light emission time and the light emission intensity).
The variation of P is significantly reduced, and the synchronization detection / control can be performed without causing the synchronization deviation or the line omission.

Here, if the optical output value (constant value) of the semiconductor laser 1 at the time of synchronization detection is the maximum output value among the optical output values controlled by the image information signal, sufficient reception at the time of synchronization detection. Since signals can be obtained and data for optical output setting can be shared, waste of setting optical output conditions can be eliminated,
The burden on the electrical system can be reduced.

By the way, also in this embodiment, the semiconductor laser 1 is used as a recording light source, and as a configuration of the semiconductor laser control circuit 8 in the light source control means 9 suitable for it, the circuit configuration shown in FIG. 5 can be applied.

[0038]

Since the present invention is configured as described above, according to the invention of claim 1, it is possible to change the optical output of the recording light source corresponding to the writing density without fixing the binarization threshold value. Since it is changed according to the writing density, even if the received light amount of the synchronizing light receiving element is changed by changing the writing density, it does not disappear when the main scanning synchronizing signal is generated by the binarization, and the occurrence of line omission during image output is prevented. This is a binarization threshold value that can be prevented and corresponds to a change in the optical output for writing, and a main scanning synchronization signal of approximately the same phase can be obtained, and synchronization deviation of a recorded image can be reduced.

In particular, according to the second aspect of the present invention, the signal length fixing means is provided to output the signal length of the main scanning synchronization signal as a substantially constant signal length. Since it is possible to correct the variation in the signal length that cannot be compensated by the setting of the binarization threshold value, the signal length fixing process by differentiation or the like in the electric control system becomes unnecessary, and according to the invention of claim 3, the binarization is performed. Regarding the threshold setting circuit, storage means for storing a binarization threshold value for each writing density, and output for outputting a binarization threshold value corresponding to a writing density signal for varying the optical output of the recording light source from the storage means to the synchronization detecting means Since the means is provided, the main scanning synchronizing signal can be appropriately detected instantly when the writing density is changed, and the malfunction of the electric control system can be prevented to perform highly reliable control.

Further, according to the inventions of claims 4 and 5, the synchronization detection is performed without depending on the change of the recording density or the change of the light emission time or the light intensity of the recording light source for the halftone recording. Since the optical output of the recording light source is always set to a constant value, it is possible to perform synchronization detection / control without line omission or synchronization deviation. In these cases, according to the invention of claim 6, high speed and Since the semiconductor laser used as the recording light source is controlled by the high-precision and high-resolution semiconductor laser control means, the optical output control accuracy is high, so the synchronization detection / control is also more accurate, and high-speed, high-quality multi-valued It enables density recording and halftone recording.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the invention described in claims 1 to 3.

FIG. 2 is a block diagram showing the binarized threshold value setting circuit.

FIG. 3 is a block diagram showing an embodiment of the invention described in claim 4.

FIG. 4 is a timing chart showing the operation.

FIG. 5 is a block diagram showing an embodiment of the invention described in claim 6;

FIG. 6 is a block diagram showing an embodiment of the invention described in claim 5;

FIG. 7 is a timing chart showing the operation.

FIG. 8 is a schematic perspective view showing the configuration of a general optical scanning recording apparatus.

FIG. 9 is an explanatory diagram showing a relationship with an optical output-binarization level at the time of synchronization detection.

[Explanation of symbols]

 1 recording light source = semiconductor laser 3 rotating polygon mirror 4 imaging optical system 5 photoconductor 6 light receiving element for synchronization 9 light source control means 12 synchronization detection means 13 binarization threshold setting circuit 14 signal length fixing means 15 storage means 16 output Means 18 Light output control means 20 Conversion means 21 Light receiving element 22 Optical / electrical negative feedback loop 23 Light output control means 24 Light source control means

Claims (6)

[Claims] 1. A rotary polygonal mirror having at least one recording light source and a photoconductor, which deflects a light beam modulated by the recording light source according to an image information signal by a predetermined angle, and the deflected light. An image-forming optical system for forming an image on the body and a photoelectric conversion signal obtained by detecting a part of the light beam outside the image writing range in the deflected light by the light receiving element for synchronization are binarized by a predetermined threshold value. An optical scanning recording apparatus comprising: a synchronization detection means for outputting a main scanning synchronization signal; and a light source control means for varying the recording light source to an optical output corresponding to at least two or more writing densities. An optical scanning recording apparatus comprising a binarization threshold value setting circuit for varying a threshold value for binarization according to a change in the optical output of the recording light source. 2. The optical scanning recording apparatus according to claim 1, further comprising signal length fixing means for outputting the signal length of the main scanning synchronization signal as a substantially constant signal length. 3. Storage means for storing a binarization threshold value for each writing density, and a binarization threshold value corresponding to a writing density signal for varying the optical output of the recording light source is output from the storage means to the synchronization detecting means. An optical scanning recording apparatus according to claim 1, wherein the optical scanning recording apparatus is a binarized threshold value setting circuit having an output means. 4. A rotary polygon mirror having at least one recording light source and a photoconductor, which deflects a light beam modulated by the recording light source according to an image information signal by a predetermined angle, and the deflected light. An image-forming optical system for forming an image on the body and a photoelectric conversion signal obtained by detecting a part of the light beam outside the image writing range in the deflected light by the light receiving element for synchronization are binarized by a predetermined threshold value. An optical scanning recording apparatus comprising: a synchronization detection means for outputting a main scanning synchronization signal; and a light source control means for varying the recording light source to an optical output according to at least two or more writing densities. An optical scanning recording apparatus comprising an optical output control means for controlling the optical output of the recording light source at the time of synchronization detection to a constant value. 5. A rotary polygonal mirror having at least one recording light source and a photoconductor, which deflects a light beam modulated by the recording light source according to an image information signal by a predetermined angle, and the deflected light. An image-forming optical system for forming an image on the body and a photoelectric conversion signal obtained by detecting a part of the light beam outside the image writing range in the deflected light by the light receiving element for synchronization are binarized by a predetermined threshold value. Optical scanning provided with synchronization detection means for outputting a main scanning synchronization signal, and light source control means for performing halftone recording by changing at least one of a light emission time and a light emission intensity of the recording light source based on an image information signal. The optical scanning recording apparatus, wherein the recording apparatus is provided with an optical output control means for controlling the optical output of the recording light source at the time of synchronization detection by the synchronization detection means to a constant value. 6. A light source for recording is a semiconductor laser, and a light receiving element for receiving and detecting the light output of the semiconductor laser, a light receiving signal and a light emission level command signal proportional to the light output of the semiconductor laser detected by the light receiving element. And an optical / electrical negative feedback loop that controls the forward current of the semiconductor laser so that the light reception signal and the light emission level command signal become equal to each other. A conversion means for converting the light emission level command signal into a forward current of the semiconductor laser based on a coupling coefficient between the light receiving element and the light output of the semiconductor laser, and a light input / light receiving signal characteristic of the light receiving element; And a control means for controlling the semiconductor laser with a current that is the sum or difference of the control current of the optical / electrical negative feedback loop and the current generated by the conversion means. 6. The optical scanning recording apparatus according to claim 4, wherein the light source control means is