KR960003344B1 - Printer light source - Google Patents

Abstract

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Description

Light source for printer

1 is a block diagram of one embodiment of the present invention.

2 is a flowchart showing a calculation procedure of correction data set in the ROM in the embodiment.

3 is a diagram showing a result of measuring a light amount distribution of a light emitting dot of a light emitting tube portion before correction in FIG.

4 is a view showing the result of measuring the light quantity distribution of the light emitting dot of the light emitting tube part after correction in the same Example.

5 is a drive timing diagram of the light source for the printer of the embodiment.

6 is a perspective view showing the configuration of a general optical printer.

7 is a perspective view showing the configuration of a conventional printer light source having a plurality of light emitting dots.

* Explanation of symbols for main parts of the drawings

A: Photosensitive drum as a recording medium 1: Light source for printer

4: drive unit 10: ROM

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light source for a printer having a plurality of light emitting dots for forming a latent image on a recording medium, and more particularly to a printer capable of driving by correcting the lighting time of each light emitting dot so that the light quantity of each light emitting dot is uniform. It relates to a light source.

In recent years, optical printers using various light sources have been proposed. FIG. 6 schematically shows a general optical printer structure as an example, in which A is a photosensitive drum as a recording medium.

The photosensitive drum A rotates clockwise in the figure, and the surface of the photosensitive drum A is charged by the charger B. FIG. On the surface of the charged photosensitive drum A, a dot-shaped light is irradiated from a light source C having a plurality of light emitting dots to form a latent image such as a desired character or figure, which is developed by the developing device D. do.

The transfer paper F stored in the cassette E is transferred between the surface of the photosensitive drum A and the transfer heater G, and the characters and figures on the surface of the developed photosensitive drum A It is comprised so that thermal transfer may be carried out to a transfer paper F continuously. In addition, in the figure, H is an erasing lamp for erasing the transferred characters, and J is a cleaning blade for cleaning the photosensitive drum A surface.

As the light source having a plurality of light emitting dots, an LED array in which a plurality of LEDs are arranged in a straight line, or a vacuum fluorescent tube proposed in Japanese Patent Application No. 60-174997 may be used.

As shown in FIG. 7, the vacuum fluorescent tube has a plurality of band-shaped anodes 100 as light emitting portions, and a plurality of control electrodes each having slits intersecting obliquely with the anode 100 above each other ( 101).

That is, by dividing the anode 100 into the slits of the control electrodes 101, a plurality of light emitting dots 102 are arranged inclined along the slits, and each of the light emitting dots A is adapted to the driving of the photosensitive drum A. By adjusting the light emission timing of (102), the light from each light emitting dot 102 can be uniformly irradiated on a straight line parallel to the axis of rotation of the surface of the photosensitive drum (A).

In such a light source for a printer, in order to improve the printing quality as an optical printer, it is preferable to make the light quantity of each light emitting dot 102 as uniform as possible. For this reason, in the past, the driving voltage was adjusted for each driving IC for driving the light emitting dots, and the light amount was adjusted for each group of the plurality of light emitting dots in charge of each IC.

In particular, in the case of the vacuum fluorescent tube of the type described above, as shown in FIG. 7, the driving voltage is adjusted by the zener diode 103 for each of the plurality of band-shaped anodes 100, or each control electrode 101 is used. The driving voltage is adjusted with the resistor array 104 or the driving voltages of both the anode 100 and the control electrode 101 are adjusted at the same time.

As described above, in the conventional light source for a printer, light quantity correction of the light emitting dot has been performed by grouping a plurality of light emitting dots.

For this reason, even if the light quantity of each light emitting dot becomes uniform in a group, it becomes unavoidable that the light amount will become nonuniform between each group, and the unevenness | variance which a printer light source produces in each light amount of a some light emitting dot will arise.

This invention is made | formed in view of the said problem, and aims at making the light quantity of each light emitting dot uniform for every dot in the printer light source which has many light emitting dots.

The light source for a printer according to the present invention includes a plurality of light emitting dots for forming a latent image on a recording medium, a driving unit for driving each of the light emitting dots with a drive signal having a variable pulse width, and a ROM for storing pulse width correction data applied to the driving unit. Have

The correction data stored in the ROM is set based on data P indicating the amount of light of each light emitting dot obtained by emitting the light emitting dots with the same pulse width, that is, the maximum value in the data P ( The setting range of the correction ratio S = Pmin / P of the pulse width is determined according to the ratio of Pmax) and the minimum value Pmin, and the correction data D of the pulse width is adjusted in response to the correction ratio S within the same setting range. The correction rate S is calculated for each light emitting dot, and the correction data D is set for each light emitting dot.

The correction data in which the ROM is stored is supplied to the drive unit. The driving unit applies a pulse width driving signal according to the correction data to each of the light emitting dots, so that each light emitting dot lights only the corrected lighting time, so that the light quantity of the plurality of light emitting dots is uniform for each dot.

The light emitting tube portion 2 of the printer light source 1 of this embodiment has a plurality of band-shaped anodes on which phosphors are deposited, and a plurality of control electrodes each formed with one slit intersecting the anode obliquely. A plurality of light emitting dots are formed by dividing each anode. More specifically, there are eight anodes, and eight light emitting dots are arranged inclined with respect to the longitudinal direction of the anode for each slit of the 304 control electrodes, and a total of 8 x 304 = 2,432 dots are formed.

As shown in FIG. 1, an anode driver 3 is connected to each anode of the light emitting tube section 2, and a driving unit 4 is connected to each control electrode. The driver 4 receives data for correction to be described later and corrects the light emission time of the light emitting dot by changing the pulse width of the output drive signal in 16 steps, thereby making the amount of light of each light emitting dot uniform. Have

For this reason, the drive unit 4 has a grid driver 5, an AND gate 6, a comparator 7, a latch circuit 8, a shift register 9, and a shift register (1) of the drive unit 4; The ROM 10 is connected to 9.

The ROM 10 stores in advance the correction data D of the pulse width set for each light emitting dot. The correction data D of the ROM 10 is selected in accordance with the signal from the address counter 11 and input to the shift register 9. The comparator 7 is connected to a gradation counter 13 for outputting a count signal for comparison with the correction data D. As shown in FIG. 12 is a timing generation circuit, and is configured to supply various clock signals and the like to the anode driver 3, the address counter 11, and the driver 4, respectively.

Next, the correction data D with respect to the pulse width stored in advance in the ROM 10 will be described.

First, each light emitting dot of the light emitting tube portion 2 emits light under a common driving condition. That is, a common driving voltage is applied to each of the anodes, and at the same time, a driving signal having the same pulse width is applied to each control electrode so that each light emitting dot emits light for the same time.

The light quantity of each light emitting dot at this time is measured with a light quantity distribution measuring instrument, and as shown in FIG. 3, data P indicating light amount for each light emitting dot is obtained.

In the graph of FIG. 3, the horizontal axis is the number of the control electrode, and the data P shows the maximum value, minimum value, and average value of each light quantity of eight light emitting dots for each control electrode.

Then, as shown in the stem 100 of FIG. 2, the data P obtained as described above is input to data processing means such as a computer.

Next, as shown in step 10, the lower limit of the amount of light of the light emitting dot is set in the data processing means. The lower limit value is the minimum amount of light that can be used depending on the use conditions such as printing speed of the printer using this printer light source.

Next, as shown in step 102, the data P inputted by the data processing means is compared, and the maximum value Pmax and the minimum value Pmin are found.

Next, as shown in step 103, the said minimum value Pmin is compared with the lower limit of the set light quantity. Here, if the minimum value Pmin is below the lower limit, the light emitting tube portion 2 is judged to be a defective product lacking light quantity and becomes NG.

If the minimum value Pmin is greater than the lower limit value, the light quantity of each light emitting dot is dropped to the level of the minimum value Pmin, and the gray scale is applied to the pulse width of the driving signal applied to each light emitting dot to make the light quantity of each light emitting dot uniform. The correction data D is set.

That is, as shown in step 104, the ratio of the maximum value Pmax and the minimum value Pmin of the data P is calculated, and the driving signal output by the grid driver 5 for driving each light emitting dot is calculated. Set range of pulse width correction rate (S).

For example, when Pmax: Pmin = 1: 0.7, considering that the light emitting dot of the maximum value Pmax is corrected to the level of the minimum value Pmin, the pulse width of the light emitting dot of the minimum value Pmin is set to 1, the maximum value (Pmax). The pulse width of the light emitting dot of?) May be 0.7.

In other words, the setting range of the correction rate S in this case is 1.0 to 0.7.

Next, the setting range of the correction rate S is divided into ranks of predetermined stages, and each rank is represented by the correction rate S of the upper limit.

Then, the pulse width of each rank is determined corresponding to the pulse width at the correction factor 1, and this is correlated with the correction data D corresponding to the rank number of stages.

In this embodiment, as shown in Table 1, the setting range of the correction factor S is 1.0 to 0.702, and the rank is set to 15 stages in accordance with the number of variable steps of the output pulses of the grid driver 5 and the like. Data D is from 1 to F. In addition, Table 2 has shown the case where the setting range of correction factor S is set to 1.0-0.6.

Next, as shown in step 105, the correction rate S is calculated for all the light emitting dots in the following equation.

S = minimum value (Pmin) / measurement data P

Next, as shown in step 106, the correction data D is determined for each light emitting dot at the calculated correction rates S, respectively.

Next, as shown in step 107, the correction data D for each light emitting dot is stored in the ROM 10 using a ROM recorder.

Next, a driving method of the printer light source 1 configured as described above will be described with reference to FIGS. 1 and 5.

The data clock signal output by the timing generation circuit 12 is input to the address counter 11, and the correction data D of the ROM 10 is sequentially output to the shift register 9. The latch signal enters into the latch circuit 8 at an appropriate timing in synchronization with the data clock signal, and the correction data D of the shift register 9 is latched into the latch circuit 8.

The gradation counter 13 counts each time the manufacturing clock signal outputted from the timing generating circuit 12 is reset to a clear signal. The compensator 7 compares the correction data D latched in the latch circuit 8 with the counter value of the gradation counter 13.

In the comparison, if the correction data D which is the gradation data is equal to or greater than the count value, the correction data D is input to the AND gate 6 to turn on the grid driver 5, and this ON time is determined by the It becomes the pulse width of the drive signal applied to the control electrode.

Then, the output signal of the grid driver 5 is turned OFF when the correction data D becomes less than the count value. That is, the pulse width of the grid output signal is corrected in step 16 in accordance with the correction data D for each control electrode.

When the anode driver 3 drives each anode of the light emitting tube unit 2 in synchronization with the driving of the control electrode as described above, a plurality of light emitting dots have a pulse width based on each correction data D stored in the ROM 10. It is driven by the drive signal. Therefore, a large number of light emitting dots emit light uniformly, and if this state is measured by the above-described light amount distribution measuring instrument, the light amount distribution of each light emitting dot can be stored within a very narrow range as shown in FIG. Therefore, when the printer light source 1 is used as the light source of the optical printer, the printing quality is significantly improved compared with the prior art.

According to the present invention, since the amount of light of all the light emitting dots of the light source for the printer is individually corrected, the variation in the amount of light can be made smaller than before.

In addition, even if the light amount distribution changes during use, the light amount distribution can be made uniform simply by measuring the light amount again and setting the correction data again.

TABLE 1

TABLE 2

Claims (1)

A plurality of light emitting dots for forming a latent image on the recording medium, a driver for driving each of the light emitting dots with a drive signal having a variable pulse width, and data (P) indicating the amount of light of each of the light emitting dots emitting light with the same pulse width; The setting range of the correction ratio S = Pmin / P of the pulse width is determined in accordance with the ratio of the maximum value Pmax and the minimum value Pmin in the above, and the pulse width is corrected in response to the correction ratio S within the same setting range. And a ROM stored in advance so as to determine the data D and thereby supply the correction data D for each light emitting dot determined to correspond to the correction rate S calculated for each light emitting dot to the drive unit. The light source for a printer characterized by the above-mentioned.