JPS6157749B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a laser recording magnification method for varying the magnification of a recorded image in a laser recording apparatus.

Conventionally, the laser recording magnification changing method is based on the case where, for example, three laser beams are controlled simultaneously in a digital printer that performs laser recording to record an image as shown in Figure 1a, and four laser beams are controlled simultaneously. When recording an image under control, the recorded image is enlarged 4/3 times as shown in FIG.

However, with such a laser recording magnification changing method, although it is possible to digitally greatly change the magnification ratio of an image, it is difficult to change it small.

SUMMARY OF THE INVENTION An object of the present invention is to provide a laser recording magnification change method that eliminates the above-mentioned drawbacks and allows slight magnification changes.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 shows a well-known multi-beam laser recording device. In this laser recording device, the readout clock is transferred from the clock oscillation circuit 1 to the image memory 2.
An image signal is read out from the image memory 2 in addition to the image signal. This image signal passes through a gate circuit 3, is modulated by a drive system 4, and is applied to an optical modulator 5. The laser beam emitted from the laser 6 is optically modulated by the optical modulator 5, main-scanned by the polygonal mirror 7 constituting the optical scanner, and transmitted to the photoreceptor drum 9 via the -θ lens 8.
Guided by this, a latent image is created there. The mirror 7 is rotationally driven by a drive section 10, and the photosensitive drum 9 is rotationally driven by a drive section 11. Also, a beam detector 12 detects a laser beam at the end of the photoreceptor drum 9, and the gate circuit 3 opens when the photoreceptor drum 9 is scanned in synchronization with the output signal. Other well-known operations are performed by a device not shown, and an image is recorded on the recording paper.

Here, the linear velocity of the photoreceptor drum 9, the optical scanner 7
The scanning speed of the clock oscillator 1 and the period of the read clock from the clock oscillation circuit 1 have a fixed relationship. Recording speed A sheet/min Recording paper size Vertical L ₁ mm x Width L ₂ mm Resolution n sheets/mm Number of surfaces of mirror 7 m-plane Number of laser beams If a sheet, horizontal scanning speed (main scanning The rotational speed N rpm of the drive unit 10 that determines the Therefore, the vertical feed speed (sub-scanning speed) is Vmm/sec
is V=L ₁ × A/60=K ₂ L ₁ , and the repetition period T sec of the horizontal scanning speed is becomes. Here, if the effective scanning period is δ, the effective scanning time T′ is becomes. Therefore, the readout period t sec per one dot of the image signal is becomes. In this way, the number of rotations N of the optical scanner 7, the feeding speed V of the recording paper that determines the number of rotations of the photoreceptor drum 9, and the period t of the readout clock are each a function of the length _L1 of the recording paper in the vertical direction. . In other words, if you want to change the length _L1 in the vertical direction of the entire image, that is, if you want to change the magnification, all you have to do is change N, V, and t according to the fixed relationship described above.

This embodiment has been developed with attention to this point, and as shown in FIG. 3, when the magnification control circuit 13 specifies the magnification of the variable magnification in the laser recording device, a corresponding control signal is sent to the memory. and is output to the control circuits 14-16. The memory and control circuits 14 to 16 are configured to respectively output information regarding N, V, and t that realize the constants K ₁ to _{K 3} as described above in response to an input signal from the magnification control circuit 13. The outputs thereof are applied to programmable counters 17 to 19, respectively, to control their frequency division ratios. The PLL circuits 20 to 22 are operated by each reference signal from the reference frequency generator 23, and the frequency division ratios of the programmable counters 17 to 19 are
Outputs a frequency proportional to _A1 to _A3 . The driving parts 10, 11 and the clock oscillation circuit 1 are the PLL circuit 2.
It operates in synchronization with the outputs of 0 to 22, and therefore N, V, and t have a constant relationship depending on the magnification specified by the magnification control circuit 13, that is, the above constants.
The length L ₁ of the recorded image in the vertical direction is changed by changing the relationship to realize K ₁ to K ₃ . Here, the reference signals of frequencies ₁ to ₃ applied from the reference frequency generator 23 to the PLL circuits 20 to 22 are synchronized with the output from one stable oscillator, and are applied to the PLL circuits 20 to 22.
The output frequencies of 22 are completely synchronized.

Although FIG. 4 shows the PLL circuit 20, the PLL circuits 21 and 22 are similarly constructed. This PLL
In the circuit 20, the reference frequency generator 23
The phase of the 400-600Hz reference signal is compared with the 400-600Hz output from the programmable counter 17 by the phase comparator PD, and the output is passed through the low-pass filter LPF.
is applied to the voltage controlled oscillator VCO through the voltage controlled oscillator VCO, which oscillates at a frequency of 4000 to 6000 Hz. The programmable counter 17 divides the frequency by repeatedly counting the output pulses of the voltage controlled oscillator VCO by a predetermined number, and the number is controlled to 40 to 60 by the output of the memory and control circuit 14. The output of the voltage controlled oscillator VCO is sent to the frequency divider circuit 24
The frequency is divided to 1/B ₁ , for example 1/100, and the frequency is 40 to 60Hz.
and is added to the drive section 10.

By using the PLL circuit in this way, the drive section 1
0, 11 and the clock oscillation circuit 1 can be controlled all at once, and the accuracy is also very high because of phase synchronization. Further, the magnification can be changed by operating a single magnification control circuit.

As described above, in the laser recording magnification method according to the present invention, the period of the readout clock in the laser recording device is varied in inverse proportion to the length of the recording paper in the vertical direction, and the scanning speed of the optical scanner and the photosensitive Since the magnification is varied by varying the rotational speed of the recording paper in proportion to the length of the recording paper in the vertical direction, it is possible to perform slight magnification changes.

[Brief explanation of the drawing]

Fig. 1 is a diagram for explaining a conventional laser recording magnification method, Fig. 2 is a system diagram showing a well-known laser recording device, Fig. 3 is a block diagram showing an embodiment of the present invention, and Fig. 4 FIG. 2 is a block diagram showing a PLL circuit of the same embodiment. 1... Clock oscillation circuit, 2... Image memory,
3... Gate circuit, 4... Drive system, 5... Optical modulator, 6... Laser, 7... Mirror, 8...-
θ lens, 9... Photoreceptor, 10, 11... Drive unit, 12... Beam detector, 13... Magnification control circuit, 14-16... Memory and control circuit, 17-
19...Programmable counter, 20-22...
...PLL circuit, 23...Reference frequency generation section.

Claims (1)

[Claims] 1. A clock oscillation circuit that sends a read clock to the image memory to read out an image signal, an optical scanner that main scans a laser beam modulated by the image signal from the image memory and guided to the photoreceptor, and the photoreceptor. In the laser recording apparatus, the period of the read clock from the clock oscillation circuit is varied in inverse proportion to the length of the recording paper in the vertical direction, and the scanning speed of the optical scanner and the A laser recording magnification changing method characterized in that the magnification of a recorded image is changed by varying the rotational speed of the photoreceptor by a drive unit in proportion to the length of the recording paper in the vertical direction.