JPS58121145A - Laser beam recorder - Google Patents

Abstract

PURPOSE:To vary the recording density of pictures, by switching the size of a laser beam spot and at the same time controlling the lighting interval, lighting control cycle, moving speed of the surface of a recording medium, etc. CONSTITUTION:A spot size controlling optical system 6 is controlled by a recording density setter 15. Thus the size of a radar spot 2c is switched. At the same time, a laser beam producing circuit 13, dividers 17 and 18 which divide the clock period, etc. in response to the operation of the setter 15. Thus the control is given to the spot lighting time interval per picture element of a picture information signal, the speed of revolution of a photosensitive drum 7 produced via a motor controlling circuit 14, the lighting control period of a spot 2c produced by a scan synchronizing circuit 12, etc. The pictures of different dot sizes and high quality are formed with the above-mentioned interlocking control. Thus it is possible to change the recording density of pictures.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a laser beam recording device, and particularly to a laser beam recording device [K] that can change image recording density.

As a laser beam generation source in a laser beam recording device, there are gas laser light sources such as He-Ne and He-Cd, and solid state laser light sources such as semiconductor, but which laser light source to use for the recording device is selected from a design standpoint. Since the present invention can be freely applied to a laser beam recording device using any laser light source, a laser beam recording device using a semiconductor laser light source will be explained below as an example.

A laser beam recording device using an electrophotographic recording method applies a uniform charge to the surface of a photoconductive drum that rotates at a constant speed, and scans the optical surface of the photoconductive drum with a laser beam spot in a minute direction. At the same time, the laser beam spot is blink-controlled to form a charge latent image, and after this charge latent image is developed with toner, the toner order is transferred onto recording paper. When this laser beam recording device is used in conjunction with a terminal of an electrical information processing device, an information image is expressed as a set of recorded dots. At the position where the recording dot is present, a laser beam spot is turned on to discharge the charge on the surface of the photoconductive drum, and a developing device develops the surface of the photoconductive drum so that toner adheres to the charge discharge area.

Therefore, the size of one recording dot is equal to the size of the charge emitting area on the surface of the photoconductive photosensitive drum, which is determined by the size of the laser beam spot and the distance traveled by the spot during one turn on. The resolution of the recorded information image, that is, the image recording density, is determined by the size of the recording dot, but in conventional laser beam recording devices, the size of the laser beam spot, lighting time width, and lighting control cycle are fixed. It was not possible to change the image recording density.

However, the recording speed can be increased by changing the image recording density depending on the type of information to be recorded, and the advantage is that one laser beam recording device can be used as a terminal for multiple information processing devices with different recording densities. can get.

Therefore, an object of the present invention is to provide a laser beam recording device that can change the image recording density.

In order to achieve this object, the present invention provides a means for switching the size of the laser beam spot, its lighting control period, lighting time width, and moving speed of the recording medium surface according to the information to be 6r2fit. It is characterized in that the image recording density is changed by changing the size of the recording dots.

Hereinafter, the present invention will be explained in detail based on illustrated embodiments.

FIG. 1 is a block diagram of a laser beam recording device. Laser beam 2 generated from semiconductor laser beam generator 1
The beam a is converted into a parallel beam 2b by a lens 8 and then irradiated onto a rotating polygon mirror 4, and the reflected beam is irradiated onto a photoconductive photosensitive drum 7 via an F-θ lens 5 and a spot size control optical system 6. The rotating polygon fi4 is rotated by the motor 8 at a constant speed in the direction of the arrow (a), so that the laser beam spot 2c formed on the surface of the photoconductive photosensitive drum 70 is repeatedly scanned at a constant speed in the direction of the arrow (middle). The photoconductive photosensitive drum 7 is rotated by the motor 9 in the direction of the arrow (c), and the drum surface moves by the width of the scanning locus (scanning+M) by the laser beam spot 2c for each scan of the laser beam spot 2c. The starting point of each scan by the laser beam spot 2C is detected by a photoelectric position sensor lO, and in synchronization with the start of scanning, painter information (me information signal from the g generation source 11 is read out via the scan synchronization circuit 12). In the case of the semiconductor laser beam generator 1, the laser beam generation control circuit 1B controls whether the laser beam 2a is generated or not (blinking of the spot 2C) by controlling the drive power supply on and off. ) can be controlled.

Furthermore, the detection signal of the position sensor lO is transmitted to the motor control circuit 14.
9 is input to control the surface of the photoconductive photosensitive drum 70 to move by a predetermined amount for each scan. The recording density setting device 15 controls the spot size control optical system 6 to control the spot size (2) formed on the surface of the photoconductive photosensitive drum 70.
C is set, the laser beam generation control circuit 18 is controlled to set the spot lighting time width per pixel of the 1-group information signal, and the clock signal generator 16 outputs the scanning synchronization circuit 12 and the motor control circuit 14. The branching ratio of the branching units 17 and 18 that controls the period of the clock signal given to the station is set. Suboc) When 2C is set to Jj, divider 17
The frequency division ratio of the frequency divider 18 is set to a small value to shorten the lighting control period of the laser beam spot 2C, and the frequency division ratio of the frequency divider 18 is set to a high value to lower the drive frequency and the rotational speed of the motor 9. Shorten the lighting time width. When the motor 9 is of the pole number converting type, the splitter 18 is omitted and the motor control circuit 14 is controlled by the output of the recording density setting device 15 to increase the number of poles and lower the rotation speed. When a step motor is used, the motor control circuit 14 may be modified to control the motor control circuit 14 so as to reduce the number of drive pulses and the step angle per scan. Suboc) B
When C is set to "large", the division ratio of the divider 17 is increased and the ZC lighting control period is lengthened, and the division ratio of the frequency divider 18 is set to a lower value to reduce the rotation speed of the motor 9. speed up and lengthen the spot lighting time width.

The semiconductor laser beam generator 1 is G
It is generally made of Ga, AI, A
It has a striped structure of 5 to 7 layers with different composition ratios of 8, and a heterojunction is formed between each layer. What is the wavelength of the laser beam 2a generated from such a semiconductor laser beam generator l? Around 8 Or1m, close to the wavelength of red in the visible light range.

As shown in FIG. 2, the spread of the laser beam 2a generated from the semiconductor laser beam generator 1 is different in the perpendicular direction (above) and the parallel direction C/) to the heterojunction surface! There is mold. From FIG. 2, the intensity of the laser beam 2a is 1/c with respect to the center! The spread angle at which the strength is found to be approximately 46 degrees in the perpendicular direction and approximately 20 degrees in the parallel direction. When the heterojunction surface of such a semiconductor laser beam generator l is installed in a direction perpendicular to the direction of the zero rotation axis of the photoconductive photosensitive drum, the laser beam 2a spreads out in the lateral direction and enters the lens 8. The cross-sectional shape of the laser beam 2a is a horizontally long ellipse. When this is made into a parallel laser beam 2b by a lens 8 having a focal length f1, its cross-sectional shape becomes a horizontally elongated ellipse as shown in FIG. 8(a), and its dimensions are as follows. This parallel laser beam 2b has a focal length of 111 m.
When a laser beam spot 2C is formed on the surface of the photosensitive drum 70 by focusing the laser beam with the F-θ lens 5 of ft,
When spot 2C is a and π as shown in Figure 8), K is spot size control 11 as shown in Figure 4.
41'Jt, cylindrical lens 6a in system 6
is inserted into the laser beam optical path to reduce the major axis dimension to a,'.

In order to approximate the shape of the recording dot formed on the surface of the photoconductive photosensitive drum 7 by the laser beam spot 2C to a square W or a perfect circle, the spot lighting time must be set to gray when the size of the spot 2C can be cut. to become Figure 5 (
When forming a large spot 2C as shown in a), the running velocity of spot 2C is V.
s, the spot lighting time is 1-1. becomes Vs. Further, as shown in FIG. 5(b), the spot lighting time width tI' when forming a small recording driver (19') with a small spot 2C' is S.

K is formed by arranging recording dots so that adjacent recording dots partially touch each other in the set meal direction of Subol-2C.
7. The lighting control cycle of 2C must be changed. C.

19" fan lighting control cycle 1,
4th grade, a! i, = −・・・・・・(7) Vs, lighting 1t in case of small 111 female dot) 19'
The il n period tl is fi 1,=---(8) Vs.

Also, in order to make the adjacent H dots contact with the outline between the foot placement direction of 2C and the @moon direction, the surface of the light drum 7 must be adjusted according to the size of the dot. There is no IL unless you change the moving violet.

For each 7)::lf, in order for the six walls of the Kojinga Shikangen drum to move as much as the size of the dot, it is necessary to::f,
Assuming that the periodicity is t, the circumferential speed Vd of the photosensitive drum 70 in the case of a large self-edge dot 1υ is as follows, and the circumferential speed vd' in the case of a small recording dot 19' is as follows. □ ・・・・・・
α becomes 1.

Next, an example of application to a laser beam recording device capable of switching the recording density between 8 dots/mm, 16 dots/mm, and 7 mm will be described. If the recording length in the spot scanning direction is 216 mm and recording is performed at 8 dots/mm as shown in FIG. 6(a), the number of recorded dots 19 per scan will be 1726. The scanning period 1s is 1.5 m5ec, and the description of 216 mm is l m
When scanning at 5ec, the scanning speed Vl of the laser beam spot 2C is 2.16 x 10' mm/sec
,bawl. Dimensions of recording dot 19 am & ma 1/8
= 1.25 XIO'mm, so the spot lighting time 1iIi & ts is 2.16
1, and the lighting control cycle is 1. From equation (7), Z, i6
It becomes X 10. Therefore, the scanning synchronization circuit 12 has 1.728 M
It is sufficient to provide a clock signal φ1 of Hz.

FIG. 6(b) is an example in which the spot lighting time width 11 is made equal to the period t*-578, 7B7 nsec of the clock signal φ1.

When recording with 16 dots) at 7 mm as shown in Fig. 6(C), the number of recorded dots (19/) per running bite is 84,521.

The scanning speed Vs of the small laser beam spot 2C' is 2
．． 16 x 10' mm/sec, the dimension al' of the recording dot 19' is l/16 = 6.25.
X 10”-”mm Spot lighting time 1
, / are obtained from equation (6), and the lighting control period 1.7 is obtained from equation (8). Therefore, the scan synchronization circuit 12 has 8.4
It is sufficient to provide a clock signal φ1' of 56 MHz.

FIG. 6(d) shows the spot lighting time width t and z as the period it' of the clock signal φ1' = 287.85185
This is an example where it is made equal to n5ec.

In this way, the lock signal φ1. Switching φ1' changes the clock frequency of the clock signal generator 16 to 8.456M1.
1z and a large recording drum) Information at 19-f#! When recording information @m#, divide the frequency into 1/2 by frequency divider 17, and use this as is when recording information @m# with small recording dot 19'.

Light 41j when recording using a large recording drum) 19
The circumferential velocity Vd of the L-sensitive photosensitive drum 70 is given by equation (9), and for the anastomosis in which recording is performed using the small recording dots 19', the following equation is obtained. Since vd: va' = 2: l,
Large d pd to motor control circuit 14) 19
In the case of 19', the clock signal of the clock signal generator 16 is input as is, and in the case of 19', the divider 18 is controlled to divide the clock signal into 1/2.
A circumferential velocity of 2=1 can be obtained.

Figure 7 (a) is a large recording drum) An example of recording 6 letters of "A" in an 8x8 dot matrix using 19 (in Figure 7)
is an example in which "o" is written in an 8×8 dot matrix using a small recording dot 19'.

FIG. 8 is a perspective view of the optical system 6 that switches the thickness of the laser beam spot into two types, large and small. The cylindrical lens 6a is attached to the side plate 6a by the plate 6b and shaft 6C.
It is supported between 66 and 66. The cylindrical lens 6a has an axis 6
With C as the center, it turns in the direction of arrow ) by the force of spring t3f.

The solenoid 6g turns the cylindrical lens 6a in the opposite direction of the arrow (as shown in the figure) against the tension of the spring 6f via the tensioner 46h, thereby intervening the lens 6a in the laser beam optical path. 61 is a positioning stopper. Therefore, make the laser beam spot 2C thicker (when doing so, use the solenoid 6
When deenergizing g and reducing it, it is difficult to energize solenoid 6g.

Note that the present invention can be further developed to change the recording density into eight or more types.

As described above, according to the present invention, the size of the recording dot is changed by changing the size of the laser beam spot, its lighting control period, lighting time width, and moving speed of the recording medium surface. You can change the recording density.

[BRIEF DESCRIPTION OF THE DRAWINGS] The drawings show an embodiment of the invention, and FIG. 1 shows a block diagram, FIG. 2 shows a laser beam spread characteristic diagram, and FIG.
) is a cross-sectional view of the parallel beam part of the laser beam, in Figure 8)
is a front view of the laser beam spot, Fig. 4 is an explanatory diagram of spot size control, Fig. 5 (a), (b), and Fig. 8g6 (
a) to (d) are explanatory diagrams of recording dot formation, FIG. 7(a),
Φ) is an example of a recorded image, and FIG. 8 is a perspective view of the spot size control optical system. ■・・・・・・Semiconductor laser beam generator, ga, 9b
... Laser beam, 2C ... Laser beam spot, 6 ... Spot size control optical system, 7 ... Photoconductive photosensitive drum, 11 ...・・・
・Image information signal generation source, 12...Travel synchronization circuit, 18...Laser beam generation control circuit, 14.
...Motor control circuit, 15...Recording density setting device, 16...Clock signal generator, 17,
18... Branch unit. Agent Patent Attorney Kenjibu Take 768 (10 (b) Su 7 Peng (α) C Go) (b) ↑ e Z 71 Procedural amendment (method) % formula % 2 Title of invention Laser beam recording scissors - 3 amendment Relationship with the case of the person who does
Correct the description with [lighting control period ttJ of clock signal φ1] (2) [point tJ control period I in 12th negative 14th line of specification]
G J's il:! The output is corrected to "clock signal φ'10 firing control period t≦". (3) Figure 5 (a), (1)) of the drawings and Figure 6 (a) to (dJ t- Figure 5 of the attached corrected drawings (
a) I (b) and Figures 6 (a) to (dJ). 9 Attached catalog correction drawings 1 copy'"f5 (a) O 6 (a) i,,, -Ino"l") 88shi

Claims (1)

[Claims] l. Irradiating a laser beam onto a recording medium surface trap moving in a predetermined direction, and blinking the laser beam spot while repeatedly scanning the laser beam spot in a direction intersecting the moving direction of the recording medium surface. In a laser beam recording device that controls the size of the laser beam spot and records an image according to the laser beam spot on the surface of the recording medium, the laser beam spot is controlled by switching the size of the laser beam spot to be large or small, and the laser beam spot is turned on. A laser characterized by comprising means for controlling the time width and lighting control cycle in response to switching the size of the spot, and means for controlling the moving speed of the recording medium surface in response to switching the size of the laser beam spot. Beam recording device. 2. In claim 1, the laser beam spot has an elliptical shape with a short axis in the scanning direction, and the means for switching and controlling the size of the laser beam spot is an optical system that switches the size of the spot in the long axis direction. A laser beam recording device comprising: