JPS5868715A - Scanning distortion correcting system - Google Patents

Abstract

PURPOSE:To correct difference of scanning speed of irradiated surface and fractionize the irradiated surface with a light beam into equal time equivalently by providing a function generator in a fixed memory and changing the oscillating frequency of a voltage controlling oscillator. CONSTITUTION:The velocity of a light beam on a surface scanned by a polygon mirror that rotates at a constant velocity is expressed by a/sin<2>theta. A pulse SR for resetting a counter circuit 7 is generated from a laser irradiation starting signal generating circuit 6 that receives a signal from a laser irradiation starting point sensor, and the value CV of the counter circuit is set to (0). After that, the counter circuit 7 is counted up by clock CC from a clock generating circuit 5. and the frequency fc of a V-F converter 9 is changed by voltage VC of a function generator 8 which is a D-A converter that generates voltage by the value CV, and output of a light modulator driver 11 is controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a scanning distortion correction method, and particularly to a scanning distortion correction method VC that corrects scanning distortion that occurs when the entire i-beam is scanned at a constant speed using a rotating mirror.

Conventionally, this type of correction has been done by optical correction (f-theta lens) or
It was corrected by arranging optical sensors at equal intervals. When correcting optically, it is done using a lens system.

Not only does it take up a lot of mounting space, but it is also cheaper on the screen side. ′! ! In addition, there were problems in terms of sensor accuracy and price, as well as mounting space and reliability.

An object of the present invention is to provide a highly reliable and low-cost scanning distortion correction method.

In non-invention, is it a set meal correction? Do it digitally (logically). That is, according to the present invention, the function generator is stored in a fixed storage device, and the oscillation frequency of the pressure-controlled oscillator is varied.

A scanning distortion correction method is obtained that corrects the difference IA in the fixed meal speed of the irradiated surface.

Reference is now made to the drawings, which illustrate one embodiment of the invention.

The present invention will be described in detail.

Referring to FIG. 1, in one embodiment of the present invention, a latent image is created on a rotating drum 2 by a rotating polygon mirror 3 and a laser beam 4. Here, the polygon mirror 3 rotates at a constant speed, and the polygon mirror 3 is irradiated with laser light 4 from a constant direction. Therefore, if the rotating mirror 3 is rotated at a constant speed, the laser beam 4 will be directed horizontally onto the photosensitive drum 2.

Is this the embodiment of the light beam of photosensitive drum 2+? When I look at it, I see that the distance from the polygon mirror is 1? lI7+, teIt, is early and becomes slower as it gets closer. If you say simple V, the edges will be faster and the middle will be slower (note that the polygon mirror 3 and photosensitive drum 2 are set parallel).

Here, the speed function V is V2a/sin'θθ
2ωL; ω2 angular velocity j and L; time a; expressed as the shortest distance between the polygon mirror 3 and the photosensitive drum 2;

The laser irradiation starting point sensor 1 indicates the starting point of laser irradiation and is made of a photoelectric conversion element.

Based on this, control is performed as shown below.

Referring to FIG. 2, the false detection sleeve correction circuit includes a laser irradiation start point signal generation circuit 6 that receives all signals from the laser irradiation start point sensor 1, a laser irradiation start point signal generation circuit 6 that generates the prenatal start point, and a counter circuit 7 that controls the function generator 8. , the function (electronic 11
3) Function generator 8 that generates and electric IE of function generator 8
A voltage frequency converter 9 that can change the frequency by
It consists of a print buffer circuit 10 that sends out a take at 1, and a clock generation circuit 5 that counts up a counter circuit.

The operation of the present invention configured as described above will be explained in detail.

When the laser source passes over the laser irradiation start point sensor, a pulse SR for resetting the counter circuit 7 is generated from the laser irradiation start point Ig generation circuit 6. This resets the value CV of the counter circuit 7 to O. Thereafter, the e-counter circuit 7 counts up based on the constant cycle clock CC generated by the clock generation circuit 5. A function generator 80, which is a digital-to-analog converter, generates a voltage according to the value CV of the counter circuit 7, and the frequency f of the voltage-frequency converter 9 is changed by the voltage VC. Print data is serially sent from the print buffer 10 by this fc, and when sent to the optical modulator driver 1, it is optically modulated and output. is faster at the end points and slower at the center point, which means that the scanning distortion of the uniformly constrained VC light can be corrected.

Here, it is assumed that the function generator is constituted by a fixed foot unit t, fL, and also incorporates a digital-to-analog converter.

Among the function generators, there are inexpensive fixed memory devices available on the market, and there are also digital-to-analog converters available on the market.
A converter is sufficient. Also, a commercially available frequency converter can be used. Therefore, upper L [21i + 4 roads can be realized without having to replace all the high-class circuits.

Therefore, as explained above, the present invention can construct a circuit that performs the scanning 111 at low cost and with high reliability using hardware elements.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a printing system of a laser printer of the present invention having a single length yj+. Figure 2 shows 11 cases of the 11th Ming Dynasty (
1) It is a flock diagram. FIG. 3 is a time chart of FIG. 2. 5- 1... Laser irradiation start point sensor, 2... Photosensitive drum, 3... Polygon mirror, 4... Laser source,
5... Clock generation circuit, 6... Laser irradiation start point signal generation circuit, 7... Counter circuit, 8...
Function generator, 9... Voltage frequency converter, 10...
・Print buffer circuit, 11... optical modulator driver,
CC...Clock, Cv...Counter value, V. ... Function generator output (voltage), f (2... Voltage frequency conversion output (frequency LL□... Light modulation driver output. Agent Patent attorney Uchihara Miscellaneous 6-

Claims (1)

[Claims] In the original beam rotating set meal, by storing the function generator in a fixed storage device and changing the oscillation frequency of the voltage controlled @ oscillator, the difference in the set meal speed of the irradiation surface is corrected, and the light beam is irradiated with equal constraints. A scanning distortion correction method that can subdivide a surface at equal times.