JPS588628B2 - Kogaku Teki Inji Souchi - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical printing device in which printing magnification can be arbitrarily changed using a mechanical deflector.

In recent years, as printing devices used for computer output have become faster, optical printing devices that combine an optical character generator and an electrophotographic screen are being adopted. It is constructed as shown in FIG.

That is, after the light beam emitted from the laser light source 1 is modulated according to information by the optical modulator 2 (the optical modulator 2 periodically modulates the refractive index depending on the magnitude of the applied voltage representing an electric signal, for example). A Pockel-type cell composed of potassium dihydrogen phosphate, which converts to , is used.

), an optical deflector 3 using an acousto-optic element performs scanning in the printing line direction (hereinafter simply referred to as sub-scanning), and at the same time, a mechanical polarizer 4 such as a rotating mirror or galvano mirror performs scanning in the printing line direction (hereinafter simply referred to as main scanning). (referred to as scanning) is performed.

The light beam deflected as described above is passed through a suitable optical system 5.
The light is irradiated onto a photoreceptor 6 such as a photoreceptor drum of an electrostatic printing machine or a photographic plate, thereby recording a character pattern.

When the width of the sub-scanning is set to the width of the characters to be printed in the printing device as described above, an optical image of one line of characters can be formed in one main scan.

For example, in the case of a character pattern consisting of a dot matrix of k rows and l columns as shown in Figure 2, if n characters are printed per line, l x n sub-scans are performed with one main scan. , the relationship between main scanning and sub-scanning is shown in FIG.

On the other hand, the modulation waveform modulated by the optical modulator 2 is
As shown in the figure, it is synchronized with the sub-scanning.

In addition, the video clock, which is the reference timing for light beam modulation, is k, which is equal to the number of lines constituting one character, for one sub-scanning.
Since k pulses are generated, the light beam is modulated dot by dot in synchronization with the video clock, and one column of one character is printed by modulating the light beam for k dots.

By repeating this l times, one character is printed, and one
By repeating printing for characters n times, one line is printed.

However, with the optical printing device described above, it is extremely difficult to convert the size of characters to be printed midway through a line for the following reasons.

In other words, converting the size of characters to be printed is usually done by converting the main scanning speed and sub-scanning speed, but in high-speed printing devices such as those mentioned above, it is difficult to change the main scanning speed suddenly. This is because it is technically difficult due to the inertia of the mechanical deflector.

This invention was made in view of the above circumstances, and it is possible to maintain the main scanning speed of the mechanical deflector constant and change the printing magnification by changing the sub-scanning period and sub-scanning width, thereby reducing the negative effects caused by the inertia of the mechanical deflector. An object of the present invention is to provide a printing device that is capable of converting printing magnification without being affected.

Hereinafter, the present invention will be described in detail with reference to an embodiment shown in FIG. A video clock is generated with a period proportional to the directional magnification.

In Figure 6, the printing from time t1 to t2 is the normal size printing, from t2 to t3 is the intercharacter space period for adjusting the printing interval, and the printing from E3 to t4 is the normal size printing. If the print is enlarged to twice the size both vertically and horizontally, the video clock synchronization is
Increase by 2 times as the amount increases by 2 times.

Since the main scanning speed by the mechanical deflector 4 is kept constant, if the sub-scanning speed by the acousto-optic deflector 3 is kept constant, the dot spacing in the sub-scanning direction will be doubled, and the time required for sub-scanning will be doubled. By doubling the dot spacing in the main scanning direction, the dot spacing in the main scanning direction also doubles, and characters enlarged twice in the vertical and horizontal directions are printed.

The video clock output from the video clock generator 7 is applied to the dot matrix character signal generator 8, and the modulator drive circuit is synchronized with the video clock during the period when the character signal exists according to the corresponding printing pattern. 9 is activated, and the laser light source 1 is activated by the optical modulator 2 connected to it.
modulates the light beam emitted by the

On the other hand, the video clock is also applied to the deflection signal generator 11, and the generated deflection signal is converted to an appropriate frequency by the voltage-to-frequency converter 10, and then applied to the acousto-optic deflector 3 to sub-scan the light beam. deflect in the direction

Note that if the printing magnification is doubled both vertically and horizontally, the area of the character will actually be four times larger, but the printing time per dot will be 1x.
Since the length of time in the column direction of the characters is only increased by a factor of two, the density of the characters is reduced by a factor of two.

However, even if the density of each printed dot is constant, it is undesirable for the density of the character to change visually depending on the printing magnification, so as shown in Figure 7, it is proportional to the square of the character size. By providing a sub-gate pulse and performing optical modulation by ANDing the gate pulse and the character signal, a means is taken to make the apparent density of printed characters constant.

As described in detail above, this invention changes the printing magnification while keeping the main scanning speed of the mechanical deflector constant, so it is possible to print larger characters, which was previously difficult to achieve due to the inertia of the mechanical deflector. This makes it possible to convert the font in the middle of a line, for example, by simply preparing a character font for printing 8 point characters on the printing device.
Any character size such as point or 16 point can be printed.

Therefore, it is easy to read the character font, and in addition,
Since the components of the mechanical deflector, such as the rotating mirror, operate at a constant speed, they are less susceptible to jitter and the reliability of the parts is high.

In the above embodiment, the optical modulator and the acousto-optic deflector are independent and separate devices, but the acousto-optic deflector may also function as an optical modulator, and the light beam used may be a laser beam. It is not limited to light, and any visible light of a single wavelength may be used.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of a conventional optical printing device, Fig. 2 is an explanatory diagram of characters composed of dot matrices, and Fig. 3 shows the timing of main scanning and sub-scanning by the printing device shown in Fig. 1 above. FIG. 4 is a waveform diagram showing the timing of sub-scanning and optical modulation, FIG. 5 is an explanatory diagram of a printing device according to an embodiment of the present invention, and FIG. 6 shows a printing pattern by the same printing device. The explanatory diagram, FIG. 7, is a waveform diagram showing the timing of each part in the same printing device. 2 is an optical modulator, 3 is an acousto-optic deflector, 4 is a mechanical deflector, and 11 is a deflection signal generator.

Claims (1)

[Claims] 1 A mechanical deflector 4 that scans the light beam modulated by the optical modulator 2 in the main scanning direction at a constant speed, and a mechanical deflector 4 that increases or decreases the sub-scanning width according to the ratio of the character magnification to be printed, and at the same time It is equipped with a deflection signal generator 11 that increases or decreases the number of sub-scans per unit time in accordance with the reciprocal of the ratio of power character magnification, and an acousto-optic deflector 3 that performs sub-scans using an output signal generated from the deflection signal generator 11. Optical printing device.