JPS6333145B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a scanning image recording device that can scan a light beam to obtain an image on a recording medium according to an information signal.

Conventionally, a light beam is modulated based on image information from an electronic computer, etc., and the image information is recorded by scanning the modulated light beam onto a recording medium using an optical deflector and an optical element such as a lens. devices have been developed.

For example, in a method in which an unexposed area that is not exposed to a light beam is visualized, a phenomenon of "image thinning" (the line becomes thinner in the beam scanning direction) occurs compared to a method in which an exposed area is visualized. This will be explained using the letter "T" as an example. "Image thinning" means that in the method in which the exposed portion is visualized, the letter "T" is formed as shown in FIG. 1, and the line width in the scanning direction is 101, 102. On the other hand, in the method in which the unexposed area is visualized, the letter "T" is formed as shown in FIG. 2, and the line widths 201 and 202 in the scanning direction are the same as the line width 101 in FIG.
A phenomenon occurs in which it becomes thinner than 102 mm. For this reason, the quality of the letter "T" deteriorates in a method in which the unexposed portion is visualized. The reason for this will be explained in more detail using a scanning line segment as an example in FIG. In the method in which the exposed area is visualized, the line segment is the rising point 310 of the image signal 300 in FIG. 314 and at point 311 where the signal is turned off, the scanning spot 313 disappears. Center line 3 of scanning the line segment formed in this way
In the exposure distribution at 15, as shown at 302, the exposure amount increases from the line 316 of the scanning spot 312 to the end 318, then becomes constant, and then increases from the line 319 of the scanning spot 313 to the end 321. Exposure decreases. At the centers 317, 320 of the scanning spots 312, 313, the exposure amount becomes 1/2. In the method in which exposed portions are visualized, for exposure distribution 302, exposed portions at a visualization level of 322 or higher are visualized, and portions at a visualization level of 322 or lower are not visualized. The width of the image becomes 323.
This corresponds to the line widths 101 and 102 in FIG. On the other hand, in the method of visualizing the non-exposed area, an image signal 3 obtained by inverting the image signal 300 is used.
04 to form an image. The scan spot disappears at a point 350 where the image signal 304 turns off at a scan spot 352. Point 35 when the signal turns ON
1, a scanning spot 353 occurs, and the scanning direction 354
Move to. The exposure distribution at the center line 355 of the scan of the line segment thus formed is shown at 306, where the exposure amount decreases to zero from the end 356 to the end 358 of the scanning spot 352. After that, it remains zero and moves from the end 359 of the scanning spot 353 to the end 3.
It increases until it reaches 61 and then becomes constant. The exposure amount at the centers 357, 360 of the scanning spots 352, 353 is 1/2. If the visualization level of the system in which unexposed areas are visualized is 362, exposed areas and unexposed areas below 362 will be visualized, and other areas will not be visualized. The width that is visualized is 363
becomes. This corresponds to the line widths 201 and 202 in FIG.

As mentioned above, in the method in which the unexposed area is visualized, the visualization width is 363 in Fig. 3 (or 20 in Fig. 2).
1,202), and the width of the image in the method in which the exposed area is visualized is 323 in Fig. 3 (or Fig. 1, 10
1, 102), development occurs in which the image becomes shorter, that is, the image becomes thinner. Therefore, the letter "T" in FIG. 1 becomes like the letter "T" in FIG. 2, and the image quality deteriorates.

In the present invention, this "image thinning" is solved by changing the width of the image signal, and a scanning image recording system that can form high-quality images such as characters in a method in which non-exposed areas are visualized is developed. It's about getting the equipment. That is, the present invention includes an information signal generating means for generating an information signal, a modulating means for modulating a light beam according to the information signal, and a scanning means for deflecting the light beam and scanning a recording medium, In a scanning type image recording apparatus that forms an electrostatic latent image on the recording medium by scanning a light beam and further visualizes an unexposed area of the recording medium by a developing means, the light beam is scanned based on the information signal. A pulse signal generating means for generating a pulse signal for modulation, and determining whether the width of the pulse signal generated from the pulse signal generating means is within a predetermined width, and determining whether the width of the pulse signal is within the predetermined width. When it is determined that the width of the pulse signal is within the predetermined width, the width of the pulse signal is expanded and applied to the modulation means, and when the width of the pulse signal is determined that the width is not within the predetermined width, the width of the pulse signal is expanded. It is an object of the present invention to provide a scanning image recording apparatus which is provided with means for applying an voltage to the modulation means.

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

FIG. 4a shows a scanning type recording device and a modulation signal generation circuit according to the present invention. In the figure, 1 is a terminal to which a character code signal read from, for example, a magnetic tape is applied, and the character code signals applied from this terminal are successively stored in the page memory 2. If the character code signal is 8 bits per character, the character code signal is stored at a predetermined address in the page memory 2 indicated by the address counter 6 based on the clock of the clock generator 5. In the page memory 2, the character code signal of the first line of one page is placed in area 2-1, the character code signal of the second line is placed in area 2-2, and the character code signal of the nth line is placed in area 2. -n, and so on. For example, if the first line consists of 128 characters, areas 2-1, 2-2, etc.
128 character code signals are stored in each of the areas L1-1, L1-2, . . . in the first row.
..., L1-128 each store an 8-bit character code signal. When writing for one page is completed, an end signal is read from terminal 1', timing controller 8 instructs address counter 6 to read, and address counter 6 performs reading.

As mentioned above, this embodiment is a scanning type recording device, so if one character pattern is made up of 32 scanning lines (rows), first, area 2-1 is divided from area L1-1. The first row is read sequentially toward L1-128, and then the L1-128 is read sequentially.
1-1 to L1-128 and record the second row.By repeating the reading of area 2-1 32 times, recording of the first line is completed with 32 rows, and area 2 is recorded. -2 is read out. Therefore, when recording, first the address counter 6 reads out the first character code signal of the first row of the page memory 2, for example a code signal 00001000 consisting of 8 bits, from the area L1-1 and applies it to the character generator 3. do. As is well known, this character generator 3 applies a character code signal and a row address signal indicating which row of the character the character corresponds to, thereby generating the character of the character corresponding to the character code signal. A dot signal corresponding to the designated row is outputted to the output line 7 in parallel.

This row address signal is formed by counting beam detection signals from a beam detector 68, which will be described later, by the row address counter 12.
In this embodiment, one character pattern is stored in the character generator 3 as 32 x 32 dots, so the row address counter 12 returns to its initial state after counting 32 horizontal synchronization signals. It is configured so that it can be restored.

The dot signal derived onto the output line 7 in this manner is converted into a serial signal by a parallel-to-serial converter 4 comprising, for example, a shift register.
This is derived above.

Conventionally, the serial signal on the signal line 9 is directly transmitted to the beam modulator 5.
3 was applied to perform beam modulation.

The present invention resides in that this serial signal is changed by the processing circuit 10. The processing circuit 10 will be described later. Next, the laser recording device 50 will be explained.

A laser beam oscillated by a laser oscillator 51 is guided to an input aperture of a modulator 53 via a reflecting mirror 52. The reflecting mirror 52 is inserted to bend the optical path in order to reduce the space of the apparatus, and can be removed if unnecessary.

For the modulator 53, an acousto-optic modulation element using a known acousto-optic effect or an electro-optic element using an electro-optic effect is used.

At the modulator 53, the laser beam
According to the input signal to 3, the strength is modulated.

In addition, when the laser oscillator 51 is a semiconductor laser, a gas laser, etc. that can perform current modulation, or an internally modulated laser that incorporates a modulation element in the oscillation optical path, The modulator 53 is omitted and the beam is guided directly to the beam expander 54.

The beam diameter of the laser beam from the modulator 53 is expanded by a beam expander while remaining a parallel beam. Furthermore, the laser beam whose beam diameter has been expanded is transmitted through a polyhedral rotating mirror 5 having one or more mirror surfaces.
5. The polyhedral rotating mirror 55 is mounted on a shaft supported by high-precision bearings (e.g., air bearings) and driven by a motor 56 that rotates at a constant speed (e.g., hysteresis synchronous motor, DC servo motor).
The laser beam 62 is horizontally swept by a polyhedral rotating mirror 55 driven by a polyhedral rotating mirror 55, and the laser beam 62 is directed to a photosensitive drum 68 by an imaging lens 67 having a known .theta.
It is imaged as a spot on top. Beam detector 6
8 consists of a small entrance slit and a photoelectric conversion element with a fast response time (for example, a PIN diode). The beam detector 68 detects the position of the swept laser beam 62, and uses this detection signal to
The start timing of the input signal to the modulator 53 for providing desired optical information on the photosensitive drum is determined. As a result, it is possible to greatly reduce errors in the division accuracy of each reflective surface of the polyhedral rotating mirror 55 and synchronization deviations in horizontal signals due to uneven rotation, and it is possible to obtain high-quality images. The tolerance range of precision required for the drive motor 56 is increased, and the drive motor 56 can be manufactured at a lower cost. Other known deflection means such as a galver mirror can also be used.

The photosensitive drum 58 has an insulating layer, a photoconductive layer,
It is made of a conductive layer, and after its surface is uniformly positively charged with a primary charger 59, the exposed portion is charged with a charge remover 60 (AC or negative charge storage) at the same time as laser beam exposure. Thereafter, the electrostatic contrast is enhanced using a full-surface exposure lamp (not shown).

The surface potentials of the exposed and non-exposed areas at each stage of the above process are shown in FIG. 4b. As shown in FIG. 4b, it is the potential at the point that actually contributes to development; at the point, the surface potential of the non-exposed area of the photoreceptor is positive and the surface potential of the exposed area is negative. Therefore, when developing the non-exposed areas with the developer 70, negatively charged toner (negative toner) is required, and when developing the exposed areas, positive toner (positive toner) is required.
toner) is provided in the developing device 70.

Note that the present invention is not limited to the above-described process, but can also be applied to a method using so-called xerography or photosensitive paper.

An example of a processing circuit 10 for changing the pulse width of a signal in a manner in which a non-exposed area is visualized is shown in FIG. 5a, and waveforms at various parts in FIG. 5a are shown in FIG. 5b. The serial input signal 400 is inverted by an inverter 408 to obtain an inverted signal 401. The inverted signal 401 is input to a pulse generator 410 and a delay circuit 411. The pulse generator 410 generates a pulse with a predetermined time width _t1 at the rising edge of the inverted signal 401, and generates the signal 40.
form 2. The delay circuit 411 receives the inverted signal 4
01 by time t ₂ to form signal 403. Signals 402 and 403 are ANDed at AND gate 412 to obtain modulated signal 404 . While the modulation signal 404 is H, the photosensitive drum is irradiated with a laser beam, and while the modulation signal 404 is L, it is not irradiated. The modulation signal 404 has a pulse width of time (t ₁ −
t ₂ ). Since pulse generation is delayed in the pulse generator 410, when the signal 402 and the inverted signal 401 are ANDed, a short pulse will be generated at the rear end of the original signal and a "whisker" will occur on the recording paper. A delay circuit 411 is provided for the purpose of preventing this. By using the signal 404 obtained by changing the input signal 400 in this way, there is an effect of eliminating thinning of the image.

As shown in FIG. 5c, a signal 502 is obtained by enlarging the inverted signal 501 by the pulse width Δt in the circuit of FIG. 5a. In the case of the original signal 501,
Similarly to FIG. 3, the laser spot at the scanning center line 515 is indicated by 503, and the exposure distribution is indicated by 504.
Indicated by If the visualization level is 504 when the inverted signal 501 is used as a modulation signal, the width is 505.
get. When the signal 502 is a modulation signal,
Since the position where the scanning spot is generated moves from 511 to 512, the exposure distribution becomes as shown by a solid line 504, and the width to be visualized is a width 506 in the same manner as in FIG. The scanning speed of the scanning spot
If Vs, the length of the line segment increases by Vs·Δt. Therefore, thinning of the image can be eliminated. The pulse width Δt for generating the elongation amount l=Vs·Δt for this purpose is determined depending on the scanning speed Vs. Further, the elongation amount l is determined by the exposure distribution 60 at the scanning center line 605, as shown in FIG. 6a.
If the visualization level changes from 0 to 601 and 602, the width to be visualized changes to 603 and 604, so it depends on the visualization level. Also, Figure 6b
As shown in , the scanning spot diameter is 612,613
Since the visualization width changes to 615 and 616 even if it changes as shown in FIG.
Further, as shown in FIG. 6c, if the light amount changes, the peak of the exposure amount also changes, so the exposure distribution changes to 621 and 622 as shown at 620. For this reason, the width of the visualized image also changes from 624 to 625, and therefore depends on the amount of light. By appropriately selecting or controlling the pulse width △t according to the scanning speed, scanning spot diameter, visualization level, and light amount, it is possible to eliminate the narrowing of the image that occurs when non-exposed areas are visualized. This allows you to obtain high-quality images.

As an embodiment of the present invention, a method of expanding the pulse width according to the width of the line segment is also effective, as opposed to the method of expanding the pulse width uniformly regardless of the line segment as in the previous example. This is because, in FIGS. 1 and 2, it can be seen that the shorter the width, the lower the image quality due to the thinning effect. Therefore, even if the pulse width is expanded only when the width is short, high-quality characters and
Images can be obtained. A processing circuit for this purpose is shown in FIG. 7a. Original signal input in series 700/
700' is inverted by the inverter INV, and the inverted signal 701/701' is output to the pulse generator 7 at the falling edge.
10 to generate signals 702/702'. On the other hand, the inverted signal 701/701' further operates the pulse generator 711 at the rising edge of the signal 703/703'.
make. Signal 702/702' and signal 703/7
The output of OR circuit 713 of 03' is 704/70
It becomes 4'. If the pulse width of the original signal is shorter than the pulse width _t4 (Fig. 7b), a pulse is generated at the output of the OR circuit 713; on the other hand, if the pulse width is longer (Fig. 7c), an OR circuit is generated. No pulse is output to the output of circuit 713. This signal 704/70
4' and the original signal passing through the delay circuit 712 are ANDed.
A new signal 706/706' is generated in circuit 714.
From the sequence in Figure 7, if the original signal is shorter than a certain pulse width, the pulse width of the original signal changes,
If the pulse width is longer than a certain value, the pulse width of the original signal is not changed and a signal with the same pulse width is obtained. Recording based on such a new information signal eliminates the image quality deterioration caused by the thinning effect when the pulse width is short. Even in such cases, high quality images can be obtained.

The embodiment in which the signal width is expanded only backwards has been described above, but as shown in FIG. , it is clear that the same effect can be obtained if the amount of expansion is the same.

As described above, the present invention improves the image quality by changing the width of the image, which reduces the image quality due to thinning of the image in a method in which unexposed areas are visualized by changing the width of the image signal. A quality image scanning image recording device can be obtained. Further, in the present invention, it is not necessary to change the character patterns stored in the character generator, and a high quality image can be obtained with a simple circuit.

[Brief explanation of the drawing]

FIGS. 1, 2, and 3 are diagrams for explaining "image narrowing," FIG. A diagram showing changes in surface potential, FIG. 5a is the processing circuit 1
The circuit diagram of the first embodiment of 0, FIG. 5b is the same as FIG. 5a.
Figure 5c shows the exposure distribution and visualization width when changing the pulse width; Figure 6a shows the visualization when the visualization level changes. Figure 6b is a diagram showing the width of visualization when the beam spot diameter changes, Figure 6c is a diagram showing the width of visualization when the beam light amount is changed, Figure 7 a is a circuit diagram of the second embodiment of the processing circuit 10;
Figures b and c show signal waveform diagrams of various parts in Figure 7a, and Figure 8 shows other signal waveform diagrams. In the figure, 3 is a character generator, 4 is a parallel-to-serial converter,
10 is a processing circuit, 51 is a laser oscillator, 53 is a modulator, 55 is a rotating polygon mirror, 58 is a photoreceptor, 70
indicates the developing device.

Claims (1)

[Scope of Claims] 1. An information signal generating means for generating an information signal, a modulating means for modulating a light beam according to the information signal, and a scanning means for deflecting the light beam to scan a recording medium, In a scanning image recording device, an electrostatic latent image is formed on the recording medium by scanning the light beam, and an unexposed area of the recording medium is visualized by a developing means, wherein the light beam is scanned based on the information signal. a pulse signal generating means for generating a pulse signal for modulating the pulse signal; determining whether the width of the pulse signal generated from the pulse signal generating means is within a predetermined width; and determining whether the width of the pulse signal is within the predetermined width. When it is determined that the width of the pulse signal is within the predetermined width, the width of the pulse signal is expanded and applied to the modulation means, and when it is determined that the width of the pulse signal is not within the predetermined width, the width of the pulse signal is expanded. 1. A scanning type image recording apparatus, characterized in that a scanning image recording apparatus is provided with means for applying voltage to said modulation means without any interference.