KR940009717B1 - Image forming apparatus - Google Patents

Abstract

No content.

Description

Image forming apparatus

1 is a schematic structural diagram of an image forming apparatus according to an embodiment of the present invention.

Fig. 2 is a block diagram showing the main parts of the image forming apparatus in the first embodiment.

3 is a timing diagram showing a relationship between a horizontal synchronization signal and image information.

4 is a flowchart for explaining processing relating to setting the scanning density and the printing speed and determining the period of the horizontal synchronization signal.

5 is a block diagram showing in detail the horizontal synchronous signal control circuit in FIG.

FIG. 6 is an explanatory diagram showing the contents of a reference table stored in a memory in FIG. 5; FIG.

7 is a flowchart for explaining in detail the period control of the horizontal synchronization signal.

8 is an explanatory diagram showing a first example of a printing state by the image forming apparatus of the present invention.

9 is an explanatory diagram showing a second example of the printing state by the image forming apparatus of the present invention.

10 is an explanatory diagram showing a third example of the printing state by the image forming apparatus of the present invention.

11 is an explanatory diagram showing a fifth example of the printing state by the image forming apparatus of the present invention.

Fig. 12 is a block diagram showing the main parts of the image forming apparatus in the second embodiment.

BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to an image forming apparatus for forming an image according to picture information on a recording sheet, and for example, to an image forming apparatus such as a laser printer.

Laser printers are widely used as high speed and high quality printers. In this laser printer, a latent image is formed on the surface of the photoconductor by reflecting and deflecting the laser beam modulated according to the picture signal on each side of the rotating polyhedron rotating at a constant speed and repeatedly irradiating in the main scanning direction of the photoconductor drum or the photoconductor belt.

In the case of changing the printing speed in such a laser printer, it is necessary to change the so-called process speed such as the surface speed of the photoconductor or the reaction speed of the recording paper.

However, if only this process speed is changed, the density of the sub-scanning direction of the image changes. For this reason, conventionally, the rotation speed of the polygon mirror was changed to cope with the process speed. Similarly, when changing the scanning density in the sub-scanning direction, it is not necessary to change the process speed, but it is necessary to change the rotational speed of the rotating polyhedron.

As described above, in the conventional image forming apparatus, the rotation speed of the rotating polyhedron is switched when the printing speed and the scanning density are changed. However, there was a drawback that the rotating polyhedron had to be rotated at a high speed, and it was not easy to accurately change the rotation speed, and the apparatus circuit for switching was also large.

Accordingly, an object of the present invention is to provide an image forming apparatus capable of changing the printing speed and the scanning density without changing the rotational speed of the rotating polyhedron at all.

In the present invention, (i) a photosensitive member moving in a constant direction, (ii) a laser beam output means for outputting a laser beam modulated in accordance with an image signal, and (iii) reflecting a ray beam from each side while rotating at a constant speed, and the photosensitive member A rotating polyhedron, which is irradiated in a main scanning direction different from the sub-scanning direction in the movement direction above, and (iv) a rotation used for reflection of the laser beam in response to a request for changing the scanning density and a printing speed in the sub-scanning direction The image forming apparatus includes surface spacing means for determining the spacing of the faces of the polyhedron, and video signal supply means for supplying video signals by one scan in synchronization with the surface of the predetermined interval determined by (v) to be used by the determining means. Let's do it.

In the present invention, the interval of the plane of the rotating polyhedron used for the reflection of the laser beam is determined according to the scanning density and the printing speed in the sub-scanning direction, and the signal is supplied by one scan in synchronization with each side of the determined interval. To achieve the purpose.

Hereinafter, the present invention will be described in detail by way of examples.

1 shows a schematic configuration of a laser beam printer according to an embodiment of the present invention. In FIG. 1, this laser beam printer is viewed from the side, and the left side of the figure is the front surface of the laser beam printer.

This laser beam printer 100 is provided with a laser scanning device 101. The laser scanning device 101 is arranged with a semiconductor laser (not shown) for modulating and outputting the laser in accordance with the speech signal. The laser beam emitted from this semiconductor laser is incident on the polygon mirror 102 and polarized according to this rotation. After the polarized laser beam passes through the f? Lens 103, the direction of travel is changed by the mirrors 104 and 105 and output from the laser device.

On the extension of the laser beam output from the laser scanning device 101, a photosensitive drum 106 which rotates in the direction of the arrow at a constant speed is arranged. The laser beam output from the laser scanning apparatus 101 repeatedly scans the predetermined exposure apparatus 107 of this photosensitive drum 106 in the axial direction, that is, the main scanning direction. Slightly before this exposure position 107, it is arrange | positioned at the charge corotron 108 opposite the photosensitive drum 106, and is made to uniformly charge the surface of the gold photosensitive drum 106. As shown in FIG. The laser beam is irradiated to the photosensitive drum 106 after the charging to form an electrostatic latent image corresponding to the image information on the drum surface. This electrostatic latent image is developed by the developing apparatus 109 on the drum surface downstream from the exposure position. In the developing device 109, a toner supply mechanism 111 for supplying the toner in the cartridge to the developing roll 110 for developing the electrostatic latent image by causing the toner to stick magnetically to the developing roll 110, or the like. Parts are arranged. A predetermined developing bias is applied to the developing roll 110.

The toner image formed by the development of the developing apparatus 10 is moved to the position opposite to the transfer corrotron 112 by the rotation of the lamellar drum 106, where it is electrostatically transferred onto the recording paper (usually paper). In addition, the magnetic corotron 108 and the transpicorotron 112 used in the present embodiment have a structure in which a single wire corotron wire is wired in a space covered by a shield member and a voltage applying terminal is provided at one end thereof. .

Next, the conveyance path of the recording paper will be briefly described. The recording paper (not shown) is filled in the cassette tray 114 inserted from the front side in the paper feeding device 113 detachably disposed below the laser beam printer 100. The recording paper disposed on the uppermost layer of the cassette tray 114 is sent out of the tray 114 by the vandal roll 115 having a half moon shape. Instead of the vandal roll 115, other means such as a litrol roll may be used.

The conveyed recording paper stops its progress once the path is advanced by the conveyance roll 128 and reaches the tip of the resist roll 129 as indicated by the broken line. Thereafter, in synchronization with the rotational position of the photosensitive drum 106, an electronic clutch (not shown) starts the rotation of the resist roll 129, whereby the recording paper is stably conveyed at a constant speed. In this way, the recording paper passes between the photosensitive drum 106 and the transfer corotron 112 at a desired timing. Only at this point of time, the transfer corotron 112 discharges, thereby electrostatically attracting the toner on the photosensitive drum 106 toward the transfer corotron 112, and transferring the toner onto the recording paper. The recording paper on which transfer has been carried out is electrostatically removed from the back surface of the drum surface by an electrostatic needle (not shown) disposed downstream of the transfer corotrone 112. The peeled recording paper is conveyed on a conveying path of a predetermined length to release the tension, and then conveyed to a fixing device 118 in pairs of the heat roller 116 and the pressure roll 117. In the fixing apparatus 118, the heat 116 and the pressure roll 117 which the recording paper abuts on a predetermined width pass between. At this time, the transferred side of the toner on the recording paper becomes the heat roller 116, and the pressure roll 117 pushes the recording paper onto the heat roller 116 to enable efficient heat transfer. The heat stroke 116 is controlled by the high temperature constant temperature. In this state, the toner image on the recording sheet adheres passionately to the sheet surface.

An exit roll 119 is provided on the exit side of the fixing device 118, and the conveyed recording paper is discharged to the upper portion of the laser beam printer 100 on the exit roll 119. Since the recording paper passes through the above-described path, the recording surface is discharged with the recording surface facing down, and the printed sheets can be fed to the stapler in the discharged order.

On the other hand, the toner image, which has not been transferred to the recording paper, is removed from the drum surface by the cleaning apparatus 120 disposed further downstream of the transfer corotrone 112. The cleaning device 120 is provided with a blade 120b for scraping the toner off the drum surface or a film 120a for preventing the toner from leaking.

By the way, in the laser beam printer 100 of this embodiment, the photosensitive drum 106, the cleaning device 120, the charge corotron 108, and the developing device 1090 are integrally formed as the EP cartridge 121. The laser beam printer 100 of the embodiment has a front cover 123, which is indicated by a dashed line, which is opened and closed about the hinge 122. The user opens the front cupper 123 to remove the paper jam or the EP cartridge. It is possible to easily exchange the 121 and the transcoccaltron 112. In the laser beam printer 100 of the present embodiment, the attachment and detachment of the mounting apparatus 118 can be easily performed by a user. .

Behind the laser scanning apparatus 101, the power supply part 124 which becomes a low voltage power supply and a high voltage power supply is arrange | positioned, and power required for each component is supplied. The control apparatus 125 is arrange | positioned behind the power supply part 124, and the electrical control of the laser beam printer 100 is performed. The image information processing device 126 is disposed above the power supply unit 124 and the control device 125, and the image information sent from the computer is translated into the language of the laser beam printer 100 and sent to the control device 125. have.

As described above, the so-called mechanical components in the laser printer 100 of the present embodiment are arranged in front of the apparatus, and the so-called electrical components 127 are arranged in the rear.

Next, the scanning to the photosensitive drum 106 by the laser scanning device 101 will be described in detail.

FIG. 2 shows components related to laser scanning in the image forming apparatus of FIG. However, in this drawing, those that are not important for explanation are omitted.

The polygon mirror 102 of the laser scanning device 101 is rotated in the direction of the arrow at a constant speed by a drive motor (not shown). The polygon mirror 102 sequentially deflects the laser beam 13 incident from the laser oscillator 11 via the modulator 12 by six faces 102a to 102f, and the fθ lens 103 (first The scan is performed at a constant speed in the main scanning direction M of the photosensitive drum 106 through FIG. Therefore, up to six main injections are possible in one rotation of the polygon mirror 102.

The laser beam reflected by the polygon mirror 102 is incident on the beam detector 22 at an angle changed by the reflector 21 at the position of the beam 16. The beam detector 22 detects the incidence of the laser beam and outputs a pulsed beam detection signal 24 to the horizontal synchronous signal control circuit 23 in the control device 125.

The horizontal synchronizing signal control circuit 23 applies a transform process or the like to the pulse waveform of the beam detection signal 24 and outputs the horizontal synchronizing signal 31 as the horizontal synchronizing signal 31 to the image information processing apparatus 126. Control is carried out so that the horizontal synchronizing signal 31 becomes a predetermined interval in accordance with the printing speed information 27 given from and the scanning density information 29 given from the scanning density control circuit 28.

The printing speed control circuit 26 outputs the printing speed information 27 in accordance with the printing speed control signal 33 given from the image information processing device 126 and at the same time with respect to the motor 34 for driving the photosensitive drum 106. The drive speed control signal 35 is outputted.

The scanning density control circuit 28 outputs the scanning density information 29 in accordance with the scanning density control signal 37 given from the image information processing apparatus 126.

The laser control circuit 15 controls the laser oscillator 11 and the modulator 12 in accordance with the image information 38 input from the image information processing apparatus 126.

In addition, the main scanning is performed in a period of 1 / 6th of the rotation period of the polygon meter 102 corresponding to the period in which each side of the polygon mirror 102 faces the photosensitive drum 106, but the laser beam conforms to the sign signal during this main scanning period. Is modulated only in the period between the beam position 17 and the beam position 18, and the beam is cut off before and after. In this embodiment, however, the laser output can be performed at a constant amplitude every time even when each surface of the polygon mirror 102 reaches the angle position where the laser beam 13 is polarized to the beam position 16. Therefore, the beam detection signal 24 is always output to each main scan irrespective of whether the feed signal is supplied or not.

The image information processing apparatus 126 is supplied with raw information from a computer or the like not shown, and at the same time, printing parameters such as printing speed and scanning density are input. The supplied biometric information is converted into image information 38 suitable for the requested printing state in accordance with a given printing parameter and stored in an image memory (not shown). Then, in synchronization with the horizontal synchronizing signal 31 from the horizontal synchronizing signal control circuit 23 of the control apparatus 125, output is performed for each line.

The data conversion based on the print parameters is for the following reason. In other words, the biochemical information supplied from a computer or the like may not be suitable for the scanning density at which the total pixel number per page is located. For this reason, the number of pixels is adjusted by removing pixels every line or adding new pixel lines.

3 shows the timing relationship between the horizontal synchronous signal 31 output from the horizontal synchronous signal control circuit 23 and the image information 38 output from the image information processing apparatus 126. As shown in FIG. As shown in (a) of this figure, the original horizontal synchronizing signal 31 has a period T of 1/6 of the rotation period of the polygon mirror 102 and is synchronized with the output timing of this image information processing apparatus. In 126, one line of image information 38 (the oblique portion of the drawing diagram (b)) is supplied to the laser controller 15 of the controller 125 (FIG. 2). The operation of the control device 125 and the peripheral device of the configuration as described above will be described.

Setting of Scanning Density and Printing Speed and Determination of Period of Horizontal Synchronization Signal 31

Along with the fourth drawing, the setting of the scanning density and the printing speed and the determination operation of the period of the horizontal synchronizing signal 31 performed before printing will be described.

When a command for specifying print parameters is input to the image information processing apparatus 126 from a computer (not shown) (step S101), the image information processing apparatus 126 decodes it and prints the speed control signal 33 (FIG. 2). And the scan density control signal 37 are output to the print speed control circuit 26 and the scan density control circuit 28, respectively (step S102).

The print speed control circuit 26 and the scan density control circuit 28 which received this output the print speed information 27 and the scan density information 29 to the horizontal synchronous signal control circuit 23, respectively (step S103). . At this time, the printing speed control circuit 26 determines whether or not a value different from the printing speed set at present is required (step S104), and at another printing speed (Y), the photosensitive drum 106 driving motor ( The drive control signal 35 is outputted to 34 to change the rotational speed of the motor (step S105).

The horizontal synchronizing signal control circuit 23 determines the period of the horizontal synchronizing signal 31 based on the inputted information. This period determination operation will be described in detail below.

5 shows the horizontal synchronous signal control circuit 23 in detail. This circuit is provided with a CPU (central processing unit) 42 having a register 41 and is connected to a memory 44, a counter 45, and an input / output signal interface circuit 46 via a bus 43.

The beam detection signal 24 from the beam detector 22, the print speed information 27 from the print speed control circuit 26, and the scan density information 29 from the scan density control circuit 28 are input and output. The signal is sent to the CPU 42 via the signal interface circuit 46, and the horizontal synchronizing signal 31 is output through the signal interface circuit 46. The pulse number of the input beam detection signal 24 is counted by the counter 45.

In the memory 44, a reference table 48 for determining period of the horizontal synchronization signal 31 is stored.

6 shows a reference table 48. In this table, the period of the horizontal synchronizing signal 31 is set corresponding to the combination of various scanning densities and printing speeds. For example, when the scan density (D) is 600 DPI (dots / inch) and the print speed (S) is 10 PPM (number of prints / minute), the period of the horizontal synchronizing signal 31 should be the basic period (Tsec). have. The period of the horizontal synchronization signal 31 when the scanning density D is 400 DPI and the printing speed S is 5 PPM indicates that the period of the horizontal synchronization signal 31 should be 3 Tsce.

In this image forming apparatus, four types of scanning densities such as 600, 400, 300, and 200 DPI can be selected, and two types of printing speeds, 10 and 5 PPM, can be selected, depot values after starting the device, and scanning density 600DPI and printing speed 10PPM are set. do.

As apparent from this table, the scanning density D, the printing speed S, and the period NT of the horizontal synchronization signal 31 always satisfy the following expression (1). Provided that N is a positive integer.

D × S × NT = 6000T ......................................... ..............................(One)

4, when the printing speed information 27 and the scanning density information 29 are input to the horizontal synchronous signal control circuit 23 in step S103, the CPU 42 of this circuit checks the reference table 48 in the memory 44. By reference, the value NT to be employed as the period of the horizontal synchronization signal 31 is extracted (step S106). For example, when the given scanning density D is 300 DPI and the printing speed S is 10 PPM, the period of the horizontal synchronization signal 31 is 2T. That is, N = 2. The CPU 42 sets this N value in the register 41 (step S107).

In this way, the setting of the scan density and the printing speed and the determination of the period of the horizontal synchronization signal 31 are completed.

Period control of the horizontal synchronization signal 31

Next, the output control of the horizontal synchronization signal 31 by the horizontal synchronization signal control circuit 23 will be described with reference to FIG.

The laser control circuit 15 (FIG. 2) controls the laser oscillator 11 in synchronization with the rotation of the polygon mirror 102 and each side of the polygon mirror 102 reaches an angular position corresponding to the beam position 16. A short pulse width laser beam is output at each timing.

The beam detector 22 which received this outputs the beam detection signal 24 of predetermined pulse width to the horizontal synchronous signal control circuit 23. As shown in FIG.

The CPU 42 (FIG. 5) of the horizontal synchronous signal control circuit 23 sets 0 to the value c of the pulse count counter 45 of the beam detection signal 24 at the start of operation (step S101). . The counter 45 increments the count value c each time the beam detection signal 24 is input (step S102) (step S103).

The CPU 42 monitors the count value c (step S104), and instructs that the horizontal synchronizing signal 31 is output when this value becomes the value N stored in the register 41 (Y). Is output to the input / output signal interface circuit 46. Upon receiving this, the input / output signal interface circuit 46 performs shaping on the pulse waveform of the beam detection signal 24 input at that time and outputs it as the horizontal synchronization signal 31 (step S105).

A series of processes in steps S101 to S105 are repeatedly performed until the print operation end signal is input below (step S106).

In the case of the above example, that is, when the scanning density D is 300 DPI and the printing speed S is 10 PPM, " 2 " is set in the register 41 to execute the operation of FIG. As a result, as shown in FIG. 3C, the horizontal synchronization signal 31 is output at the pulse interval 2T. This means that each time the beam detection signal 24 is input twice, the horizontal synchronization signal 31 is output once.

Each time the image information processing device 126 receives the horizontal synchronization signal 31 of the pulse interval NT, it outputs one line of image information 38 to the laser control device 15. FIG.

For example, when N is 2, image information 38 for one line is output at intervals of 2T as shown in FIG. 3D. Of course, this image information 38 is not the raw picture information supplied from the computer, but has been accumulated in the image memory converted into a data format suitable for the request of 300DPI scanning density and 10PPM printing speed as described above.

The laser controller 15 controls the laser oscillator 11 and the modulator 12 in accordance with the given image information 38 to output the laser beam 13 to the polygon mirror 102.

When N is 2, the laser beam 13 is reflected to the first surface 102a, the third surface 102c, and the fifth surface 102e of the six surfaces of the polygon mirror 102, for example. It enters the drum 106. That is, the laser beam 13 is not output at the timing where the second surface 102b, the fourth surface 102d, and the sixth surface 102f oppose the photosensitive drum 106.

In this case, since the rotational speed of the photosensitive drum 106 is retained as it is by the processing of FIG. 4, steps S104 to 105, as a result, the printing speed remains at 10 PPM and only the scanning density is changed to 300 DPI, which is 1/2 of the original density. do.

In the case where the designated scanning density D is 600 DPI and the printing speed S is 5 PPM, the pulse interval is 2T as shown in FIG. In this case, however, the rotational speed of the photosensitive drum 106 becomes 1/2 of the original by the processing of Steps S104 to S105 of FIG. 4, and as a result, the scanning density remains as it is 600 DPI and only the printing speed is 1/2 of the original. Will be changed to 5PPM.

In the case where the designated scanning density (D) is 300 DPI and the printing speed (S) is 5 PPM, the pulse interval becomes 4T according to FIG. 6, while the rotation speed of the photosensitive drum 106 becomes 1/2 of the original. As a result, the scanning density is changed to 300 DPI, which is 1/2 of the original, and the printing speed is changed to 5PPM, which is 1/2 of the original. In this case, the surfaces used for reflection of the polygon mirror 102 are three surfaces, such as the first surface 102a, the fifth surface 102e, the third surface 102c, the first surface 102a ... Becomes

In the case where the designated scanning density (D) is 400 DPI and the printing speed (S) is 5 PPM, the pulse interval becomes 3T according to FIG. 6, while the rotation speed of the photosensitive drum 106 becomes 1/2 of the original. As a result, the scanning density is changed to 400 DPI which is the original 2/3, and the printing speed is changed to 5PPM which is the original 1/2. In this case, the surface used for the reflection of the polygon mirror 102 becomes only two surfaces of the first surface 102a and the fourth surface 102d.

Fig. 8A shows the printing state of the image forming apparatus at the depot value, that is, the scanning density is 600 DPI and the printing speed is 10 PPM. In this case, the period of the horizontal synchronization signal 31 is T, and all six surfaces of the polygon mirror 102 are used.

8B shows a printing state printed at a scanning speed of 600 DPI and a printing speed of 5 PPM. In this case, the period of the horizontal synchronization signal 31 is 2T, and every other surface of the polygon mirror 102 is used. Moreover, the solid line drawn in bold in the above figure actually shows the line to which the laser beam was irradiated, and the broken line shows the line which carried out the irradiation. The same applies to the following drawings.

Figure 9a shows a printing state in which the scanning density is printed at 300 DPI and the printing speed at 10 PPM. In this case, the period of the horizontal synchronization signal 31 is 2T, and the surface of the polygon mirror 102 is used every other time.

FIG. 9B shows a printing state printed at a scanning density of 300 DPI and a printing speed of 5 PPM. In this case, the period of the horizontal synchronization signal 31 is 4T, and three surfaces of the polygon mirror 102 are used.

9C shows a printing state in which the scanning density is printed at 400 DPI and the printing speed at 5 PPM. In this case, the period of the horizontal synchronization signal 31 is 3T, and two surfaces of the polygon mirror 102 are used.

In the present embodiment, a system in which the enemy of the scanning density (D), the printing speed (S) and the period (NT) of the horizontal synchronizing signal 31 is 6000T has been described as shown in equation (1). no.

For example, in a system of low performance as a whole whose enemy is 3000T, the printing state becomes as shown in FIG. This figure (a) shows a case where the scanning density is 300 DPI, the printing speed is 10PPM and the period of the horizontal synchronizing signal 31 is T. (b) the scanning density is 300 DPI, the printing speed is 5PPM and the horizontal synchronizing signal 31 is shown. The period of is 2T. (C) shows a case where the scanning density is 600 DPI, the printing speed is 5 PPM, and the period of the horizontal synchronization signal 31 is T. FIG.

On the other hand, in a system having high performance as a whole whose enemies are 12000T, the print state is as shown in FIG. This figure (a) shows a case where the scanning density is 600 DPI, the printing speed is 10PPM, and the period of the horizontal synchronous signal 31 is 2T. (B) The scanning density is 400 DPI, the printing speed is 10PPM, and the horizontal synchronous signal 31 is shown. It shows that the period of is 3T. (C) shows a case where the scanning density is 300 DPI, the printing speed is 10 PPM, and the period of the horizontal synchronization signal 31 is 4T.

As described above, in the present embodiment, the horizontal synchronization signal control circuit 23 removes the beam detection signal 24 at appropriate intervals, thereby obtaining the horizontal synchronization signal 31 having a predetermined period.

On the other hand, as shown below in the second embodiment, the horizontal synchronization signal 31 having a predetermined period can be obtained by removing the laser beam itself incident on the beam detector 22.

12 shows the main parts of the image forming apparatus in the second embodiment of the present invention. In this figure, the same reference numerals are given to the same parts as those in the first embodiment (FIG. 2), and description thereof is omitted as appropriate.

In this example, the print speed information 27 output from the print speed control circuit 26 and the scan density information 29 output from the scan density control circuit 28 are not the horizontal synchronous signal control circuit 23, but laser control. It is supposed to be input to the device 15.

The internal structure of the laser control device 15 has a circuit configuration substantially the same as that shown in FIG. 6, and reference tables are provided to correspond to the scanning density, the printing speed, and the period of the horizontal synchronization signal 31.

This control device 15 performs the same operation as in the first embodiment. That is, the CPU (not shown) extracts the value NT to be used as the period of the horizontal synchronization signal 31 by referring to the reference table and sets this value of N in its register.

The counter (not shown) of this laser control device 15 counts the number of pulses of the rotation synchronization signal output in synchronization with the rotation of each surface by an encoder (not shown) that monitors the rotation of the plygon mirror 102. The CPU monitors this count value and when the value becomes the value N stored in the register, the CPU controls the laser oscillator 11 and the modulator 12 to output the synchronous beam for incidence into the beam detector 22. As a result, the beam detection signal 24 is output from the beam detector 22 to the horizontal synchronous signal control circuit 23.

Whenever the beam detection signal 24 is input, the horizontal synchronous signal control circuit 23 performs a shaping or the like on this pulse waveform and outputs it as the horizontal synchronous signal 31. As a result, the period of the horizontal synchronization signal 31 becomes NT.

The following operation is the same as in the first embodiment.

In this manner, in the second embodiment, the beam detection signal 24 input to the horizontal synchronous signal control circuit 23 is not subtracted, but the output of the synchronous beam to the beam detector 22 is controlled by the laser oscillator 11. You will be taken away.

As described above, according to the present invention, since the interval of use surface of the rotating polyhedron is determined according to the scanning density and the printing speed, and the signal is supplied by one line in synchronization with this interval, it is not necessary to switch the rotational speed of the rotating polyhedron. . Therefore, a large-scale circuit is unnecessary for changing the scanning density or printing speed, and the control is easy and accurate.

Claims (1)

A photosensitive member moving in a predetermined direction, a laser beam output means for outputting a laser beam modulated in accordance with a speech signal, and a main scanning direction different from the sub-scanning direction which is the moving direction on the photosensitive member by reflecting the laser beam on each surface while rotating at a constant speed Means for determining the spacing of the surfaces of the rotating polyhedron used for reflection of the laser beam in response to at least one of the rotating polyhedron to be irradiated repeatedly, and the request for changing the scanning density in the sub-scanning direction and changing the printing speed. And picture signal supply means for supplying picture signals one by one in synchronization with a plane of a predetermined interval determined to be used by said determining means.