JPS636578A - Laser image recording device - Google Patents

Abstract

PURPOSE:To miniaturize the device and to reduce its cost by bringing one laser beam containing the laser beams of three primary colors, to a time division modulation at every horizontal scanning period by an ultrasonic optical modulator (AOM). CONSTITUTION:A laser beam from a white laser 1 is reflected by a mirror 2, and made incident on an AOM 3. On other hand, the color image signal of three colors is inputted to a time division modulation driving means 4, and with respect to laser beams of three primary colors in one laser beam containing three primary colors, a color modulation by a color image signal of three colors is executed as a time division at every horizontal scanning period. A driving signal is outputted to the AOM 3. The laser beam subjected to modulation and outputted from the AOM 3 reaches an image forming surface 7 through a cylindrical lens 5, a prism 6, a polygon 8, etc. According to such constitution, the modulation to the laser beam of three primary colors can be executed by one set of AOM, and since the laser beam is not synthesized nor separated, a dichroic mirror is eliminated. Also, an optical adjustment mechanism and a man-hour for adjustment for the synthesis are eliminated, as well, and the device can be miniaturized, thereby reducing the cost.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention is directed to dichroic mirrors and AOMs (AcousLo Optic) for separating or combining laser beams.
The present invention relates to a laser image recording device that reduces the number of ultrasonic light modulators (ultrasonic light modulators) used to simplify and downsize the device while increasing its speed.

(Prior Art) FIGS. 10 and 11 are diagrams showing the basic configuration of a conventional color laser printer.

FIG. 10 shows a system using three lasers, a red laser 20, a green laser 21, and a blue laser 22, as laser light sources, which is called a three-tube system.

The system shown in FIG. 11 uses one helium-cadmium (He-Cd) white laser 23 that outputs white laser light containing the three primary colors of red, green, and blue, and is called a single-tube system.

In the three-tube type, each color laser beam output from each laser is connected to an AOM (Acou
The laser beams of each color are modulated with image signals by the ultrasonic optical modulators 3, 3', and 3'', and the modulated laser beams of each color are sent to the corresponding gicchroic mirrors 24, 24', and 3'', respectively. 24", and by aligning the optical axes at the time of reflection, it is combined into one beam, which passes through the subsequent optical system.
, the beam is scanned by a deflector, and a color image is photosensitively formed on the imaging surface of the photosensitive material 17. In the single-tube type, one laser outputs three primary color laser beams of red, green, and blue as one beam. However, the intensity modulation using the color image signals of each color must be performed separately for each of the red, green, and blue laser beams.
, 25'' is used to separate red, green, and blue laser beams. After separation, the configuration is similar to that of the three-tube type.

The above is a description of the prior art, but FIG. 12 is not a prior art, but a block diagram showing the configuration of a time-division modulation type color laser printer invented by the inventor of the present application and for which a patent has been applied for separately.

Using a He-Cd white laser 23 as a laser light source, 3
One white laser beam containing primary color laser beams is output and enters the AOM 3 via the optical system. AOM
The driver 15 is configured to output a high frequency signal having a driving frequency such that the Bragg angle is equal to each wavelength of the three primary colors of light incident on the AOM 3. The driving frequencies corresponding to the red, green, and blue laser beams are f3 and f2, respectively.
, f.

Then, the high frequency signal of frequency f1 is amplitude modulated by the red image signal, the high frequency signal of frequency f2 is amplitude modulated by the green image signal, and the high frequency signal of frequency f is amplitude modulated by the blue signal.

Then, the AOM driver 15 switches its driving frequency in a predetermined order every horizontal scanning period according to the signal from the RGB time-series signal generation circuit 16. Therefore, the AOM driver 15 switches the driving frequency at the same Bragg angle, respectively. Red, green, and blue laser beams modulated by corresponding color image signals are switched and output for each horizontal scan.

The output beam reaches the imaging surface of the photosensitive material 17 via a filter and other optical systems whose passing light is switched in accordance with the color of the beam.

Then, on the image forming surface of the photosensitive material 17, the same area is scanned three times in total with the red, green, and blue laser beams, once each, to complete exposure for one scanning line of the color image. After the exposure is completed, the photosensitive material 17 is moved by the horizontal scanning line interval and the same process is repeated.

Therefore, the movement of the photosensitive material 17 is a stepwise movement (intermittent feeding), and for this reason, a pulse motor is used as a power means for moving the photosensitive material 17.

(Problems to be Solved by the Invention) However, first, the three-tube type requires three lasers, which inevitably makes the device large, complicated, and expensive.

In addition, since the intensity of each of the three color laser beams is individually modulated, three AOMs are required.
Three guichroic mirrors are used to combine the book's laser beams into one. Optical adjustment (color matching) that accurately combines these three beams into one beam requires a complicated mechanism, resulting in an increase in the number of parts and the number of adjustment steps.

Next, in the single-tube type, there is only one laser, so in this respect, it is possible to achieve lower costs and a smaller size. However, the laser light output from one laser in one beam is red.

The laser beam is separated into three colors: green and blue. Therefore, the number of gicchroic mirrors for beam separation is increased by three compared to the three-tube type.

In addition, it is the same as the three-tube type in that three AOMs are required, and a complicated mechanism and adjustment man-hours are required for optical adjustment.

The time-division modulation type color laser printer shown in Figure 12 is an improvement over three-tube and single-tube types in that it eliminates the need for a gicroic mirror and requires only one AOM. There is a problem in that the printing speed cannot be increased because a pulse motor is used to move the photosensitive material and it is operated in a pull-in mode.

For example, when the sub-scanning line density is 20 lines/m+i, the print length in the sub-scanning direction is 297+*, and the rotation speed of the 8-sided polygon is 2.00 Orpm, the printing time takes about 1 minute. In order to intermittently feed the exposed member (photosensitive material), it is necessary to increase the startup speed of the pulse motor, for example. In the above example, the self-starting frequency of the pulse motor may be approximately 300 Hz, which is a sufficiently achievable value.

However, if you want to shorten the printing time from 1 minute to about 10 seconds, the scanning speed of the laser beam can be easily increased by increasing the polygon rotation speed from 2000 to 10.00 Orpm or by increasing the number of polygon faces. Yes, but the self-starting frequency of the pulse motor is about 5 times greater than 1.5001! z
It is very difficult to do so (see Figure 9(b)).
If a pulse motor with a low self-starting frequency is used, a so-called step-out phenomenon will occur.In order to prevent the step-out phenomenon, if the motor is driven at a low frequency, the sub-scanning line density will be reduced to 2.
Since it is not possible to deal with 0 lines/1 ugly line, there is a problem that scanning line unevenness occurs.

On the other hand, if you drive a pulse motor in pullout mode,
Although it is possible to increase the speed of conveyance, since the photosensitive material is conveyed continuously, there is a problem that color misregistration of RlG and B occurs within the -scanning line.

The purpose of the present invention is to take into consideration the problems in the above technology, and to
To provide a laser image recording device that requires only one AOM, does not require a glaucroic mirror, does not require complicated mechanisms or adjustments for color matching as in the past, and is capable of high-speed printing.

(Means for Solving the Problems) The present invention has the following means configuration to achieve the above object. That is, the laser image recording device of the present invention comprises: an AOM that performs color modulation on each primary color laser beam in one laser beam including three primary color laser beams by a corresponding color image signal; a time-division modulation drive means for switching the color modulation of the three colors in a predetermined order every horizontal scan and performing it in a time-division manner; vertical deflection means for vertically deflecting each color laser beam so that it is horizontally scanned at equal distances d in the moving direction of the photosensitive material (vertical direction); during a time corresponding to one horizontal scanning period of the primary color laser beam; and a photosensitive material moving means for vertically moving the photosensitive material at a speed of moving the photosensitive material by the distance d.

(Function) Hereinafter, the function of the laser image recording apparatus of the present invention having the above-described configuration will be described.

The laser beam including the three primary color laser beams output from the laser light source device is an AOM, and each laser beam of the three primary colors is modulated with the corresponding color image signal in one horizontal scanning period unit by a signal from the time division modulation driving means. Beams are output in a time-division manner.

For example, after a red laser beam modulated by a red image signal is output corresponding to one horizontal scan, a green laser beam modulated by a green image signal is output, and in the next cycle a blue laser beam modulated by a blue image signal is output. A laser beam is output.

That is, it is not possible to record one scanning line of a color image until three scans are performed corresponding to the three primary colors. thus,
Each color laser beam modulated by the color image signal is
The image plane is deflected by the vertical deflection means so that when horizontal scanning is performed on the imaging plane, 03 scanning lines for each color are drawn at equal intervals in the moving direction of the photosensitive material, that is, in the vertical direction. Now, let this interval be d, and the vertical positions corresponding to each color be ``■'', ``■,'' along the moving direction of the photosensitive material.

In this case, the order of colors of the laser beam output from the AOM is as follows: ■→■→■−■→■→■・・・■
It is set so that →■→,■.

- On the other hand, the photosensitive material is transferred into primary colors by means of moving the photosensitive material.
- is moved by d in the vertical direction in a time corresponding to one horizontal scanning period of the frame. Then, if the color of the 80M output beam changes every horizontal scan and the vertical position of the horizontal scan changes from ■→■→■, the photosensitive material also changes by d between ■→■. Since the light-sensitive material moves further by d between ■→■, the photosensitive material itself is exposed to laser beams of colors corresponding to ■, ■, and ■ at the same location.

Next, when ■→■, the photosensitive material has also moved by d, so exposure is performed again at a new position using new image information.

Here, the vertical direction of the laser beam changes stepwise each time the color (wavelength) changes, but the movement of the photosensitive material can be either stepwise or continuous.The difference is that the horizontal scanning line on the photosensitive material There is no practical problem at all, it just depends on whether it is completely horizontal or slightly tilted by the amount of movement.

As explained above, in the laser image recording device of the present invention, for one laser beam containing laser light of three primary colors, modulation by color image signals for each primary color is performed in a time-sharing manner in the horizontal scanning period of the laser beam. By doing so, one A
The OM enables modulation of the three primary color laser beams, and therefore does not combine, separate, or combine the laser beams as in conventional equipment, so there is no need for a gicroic mirror, which was required for this purpose. This also eliminates the need for complex optical adjustment (color matching) mechanisms and adjustment man-hours for synthesis, which results in simpler equipment, smaller size, higher reliability, and lower cost. By vertically deflecting the laser beams of each primary color, it is possible to move the photosensitive material continuously, and as a result, the pulse motor can be driven at high speed in pull-out mode, and motors other than pulse motors can be used. This makes it possible to speed up the movement of the photosensitive material (see FIG. 9), making it possible to realize a high-speed printer.

(Example) Hereinafter, an example of the present invention will be described based on the drawings. 1st
The figure is a configuration diagram of a first embodiment of the present invention in which a prism is used as the vertical vCIii direction means.

A laser beam output from a white laser 1 is reflected by a mirror 2 and enters an AOM 3.

- On the other hand, color image signals of three colors are inputted to the time division modulation driving means 4, and the time division modulation driving means 4 is configured such that the AOM 3 is
For each primary color laser beam in one laser beam including primary color laser beams, color modulation using the corresponding color image signal is switched in a predetermined order every horizontal scanning period in a time-sharing manner. A drive signal to cause the operation to be performed is output to the AOM3.

The modulated laser beam output from the AOM 3 passes through a cylindrical lens 5 for tilt correction and enters a prism 6 which is a vertical deflection means.

In the prism 6, the laser beams of each primary color are focused on the imaging plane 7 for each color.
, the light is deflected so as to irradiate the photosensitive material at equal distances Md in the moving direction (vertical direction). prism 6
The laser beam exiting the mirror 2' is reflected by the mirror 2', and is further reflected by a polygon (the figure shows a polygon, but a galvanometer mirror can also be used).
(same for other figures) reflected by f-θ lens 9
, and reaches the imaging plane 7 via the cylindrical lens 5'.

The photosensitive material is arranged so that its photosensitive surface coincides with the imaging plane 7. As the polygon 8 rotates clockwise as indicated by the arrow, the laser beam scans the image plane from the left side to the right side in the figure.

This is called horizontal scanning. Photodiodes (P, D) for detecting the start of scanning at the most horizontal scanning
, )10 are provided.

FIG. 2 is a block diagram of an embodiment using a deflection mirror 11 as the vertical deflection means. The deflection mirror 11 has a rotation center 14
It can be rotated by the required angle around , and a piezoelectric element 12 is attached to the negative end.
The piezoelectric element 12 expands and contracts in response to a signal from the piezoelectric element control circuit 13 to change the angle of the deflection mirror 11, thereby performing vertical deflection of the beam. The operation of the piezoelectric element control circuit 13 is performed in synchronization with time division modulation.

The operation of the pond is the same as in Figure 1.

FIG. 3 is a block diagram of an embodiment in which an AOM 3' is used as the vertically deflecting means. The diffraction angle of the beam in the AOM varies depending on the wavelength of the incident beam and the driving frequency, so this is used to perform vertical IQ direction. AOM driver 1
The driving frequency of the high frequency signal outputted from 5 is switched in synchronization with time division modulation. The operation of the pond is the same as that shown in FIG.

FIG. 4 shows an example in which the AOM 3 is used for both color modulation and vertical deflection. Since the diffraction angle of the laser beam in the AOM changes depending on the wavelength of the incident laser beam and the driving frequency, vertical compensation can be applied by appropriately selecting the driving frequency. The operation of the pond is the same as that shown in FIG.

Note that when modulation is performed with an AOM or when the AOM is used as a vertical deflection means, not only the desired beam output but also unnecessary beams are output at different angles.

The diffraction angle at the AOM is determined by the product of the wavelength of the incident light and the driving frequency. Now, if the wavelength of light is λB and the driving frequency is fB, the required diffraction angle of the beam is determined by λ11' f 11. However, since the incident laser light also contains G and R lights, if these wavelengths are λG and λa, respectively, then as shown in FIG. ., θ'8, unnecessary G and R light beams are output.

It is conceivable to use the slit 18 as a means to block this unnecessary light. Further, by providing a filter 19 that allows only desired light to pass through, a purer desired beam can be extracted.

Next, the progress of exposure on a photosensitive material using a beam subjected to time division modulation and vertical polarization will be explained.

FIG. 5 is a diagram showing how laser beams vertically polarized at different angles for each color irradiate the photosensitive material 17 on the imaging plane.

FIG. 6 is a diagram showing the time relationship between time division modulation and horizontal synchronization. The waveform diagram (C) is a diagram showing that modulation by each color image signal is performed in the AOM after a certain period of time To has elapsed by counting the clock signal after the beam is detected.
) is a diagram showing the time division area for each color, and in area B, blue (
B) The laser beam is modulated by a blue image signal, and in the G area, the green image signal is modulated.CG) The laser beam is modulated by a green image signal, and in the R area, the red (R) laser beam is modulated by a red image signal Modulation is performed using the image signal, and this completes the modulation of the color image for one scanning line.
This indicates that the third scanning line segment is repeated. This shows the progress of exposure on a photosensitive material when the laser beams of each color are subjected to time-division modulation as shown in Fig. 6 and horizontally scanned by being subjected to vertical deflection for each color by a vertical deflection means as shown in Fig. 5. and as shown in Figure 7.

In the figure, O is one pixel due to sunlight, × is one pixel due to G light,
* indicates one pixel by R light.

Since the first period in FIG. 6 is in area B, horizontal scanning is performed at the position indicated by ■ in FIG. This is point A in Figure 7. Second
Since the period is in the G region, horizontal scanning is performed at the position of ■. At this time, the photosensitive material 17 has also moved exactly d in the direction of the arrow by the time scanning begins, so that the G light is exposed over the area exposed to sunlight, as shown in the opening in FIG.

Since the third period is in the R region, horizontal scanning will be performed at the position shown in Figure 5 (■), but by this time the photosensitive material 17 has also moved further by d in the direction of the arrow. Exposure is carried out overlapping the same position exposed to sunlight and G light. This means that one scanning line on the photosensitive material has been exposed to three primary colors. In the fourth period, the area is B again, so horizontal scanning is performed at the position shown in Figure 5 (■), but since the photosensitive material still moves by d in the direction of the arrow, it is placed at a new position 3d away from the position of the first scanning line. Exposure for the second scanning line is then started.

As already mentioned, the movement of the photosensitive material in FIG. 7 may be stepwise or continuous.

(Effects of the Invention) As explained above, in the laser image recording device of the present invention, modulation by color image signals for each primary color is performed by horizontally scanning the laser beam with respect to one laser beam containing laser beams of three primary colors. By performing time-sharing at regular intervals, one A
The OM makes it possible to modulate the laser beams of the three primary colors, and therefore does not combine or separate and combine the laser beams as in conventional equipment, eliminating the need for dichroic mirrors that were required for this purpose. P for synthesis! No complicated optical adjustment (color matching) mechanism or adjustment man-hours are required, simplifying and downsizing the device.

This will result in higher reliability and lower costs, and by vertically deflecting the laser beams of each primary color, it will be possible to move the photosensitive material continuously, resulting in a pulse motor. It has the advantage that it can be driven at high speed in the pull-out mode, and that motors other than pulse motors can be used to speed up the movement of the photosensitive material (see FIG. 9), making it possible to realize a high-speed printer.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of the first embodiment of the device of the present invention, FIG. 2 is a diagram showing the configuration of the second embodiment of the device of the present invention, and FIG.
The figure shows the configuration of the third embodiment of the device of the present invention, FIG. 4 shows the configuration of the fourth embodiment of the device of the present invention, and FIG. 6 is a diagram showing the time relationship between time-division modulation and horizontal synchronization, FIG. 7 is a diagram showing the progress of exposure on a photosensitive material, and FIG. 8 is a diagram of unnecessary beam cutting means in the AOM output beam. Figure 9 is a diagram showing an example of the characteristics of a pulse motor, Figure 10 is a configuration diagram of a conventional three-tube color laser printer, Figure 11 is a configuration diagram of a conventional single-tube color laser printer, and Figure 12 is a separate patent. It is a configuration diagram of a time-division modulation type color laser printer pending application. 1... White laser, 2.2'......
Mirror, 3.3', 3''...AOM, 4.
...Time division modulation drive means, 5.5'...
Cylindrical lens, 6... Prism, 7
...imaging plane, 8...polygon, 9
......f-theta lens, 10...P, D
. (Photodiode), 11... Deflection mirror, 12... Piezoelectric element, 13... Piezoelectric element control circuit, 14... Center of rotation, 15...
...AOM driver, 16...RGB time series signal generation circuit, 17...Photosensitive material, 18
...Slit, 19...Filter,
20... Red laser, 21...
Green laser, 22... Blue laser, 2
3...He-Cd white laser, 24.24'
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Claims (5)

[Claims] (1) an AOM that performs color modulation on each primary color laser beam in one laser beam including three primary color laser beams using a corresponding color image signal; color modulation of the three colors in the AOM; a time-division modulation driving means that performs time-division modulation by switching in a predetermined order for each horizontal scan; laser beams of each primary color are directed in the moving direction (vertical direction) of the photosensitive material on the imaging plane of the photosensitive material; a vertical deflection means for vertically deflecting each color laser beam so that the laser beam of each color is horizontally scanned at equal distances d in a direction); a speed at which the primary color laser beam moves by the distance d during a time corresponding to one horizontal scanning period; 1. A laser image recording apparatus comprising: a photosensitive material moving means for vertically moving a photosensitive material; (2) A laser image recording apparatus according to claim (1), characterized in that a prism is used as the vertical deflection means. (3) The laser image recording apparatus according to claim (1), characterized in that an angle change mirror is used as the vertical deflection means. (4) The laser image recording apparatus according to claim (1), characterized in that an AOM is used as the vertical deflection means. (5) The laser image recording device according to claim (1), wherein the AOM that performs color modulation also serves as vertical deflection means.