JPH01168464A - Image recorder - Google Patents

Abstract

PURPOSE:To control dispersion of exposures in a photosensitive recording medium, by providing a means for correction of a time period (applying time) of a driving signal fed each of light emitting elements and a light control element according to corresponding stored light correction information on amount of light. CONSTITUTION:Light correction information on amount of light for each LED in an LED array part 13 are stored in a scanning clock circuit 14. An address signal is sent out to a read memory ROM 16. A time correction circuit 18 outputs a pulse of a specific pulse width for all 'black' image signals in the first reading of an image signal. On and after the second reading, it outputs or does not output a pulse of a specific pulse width narrower than that in the first reading of the 'black' image signal according to the light correction information. An amplifier in an LED drive amplification circuit 12 sends a signal which is produced by amplification of the pulse inputted from the time width correction circuit 18 to a corresponding LED as a driving signal. That is, each LED is scanned n-times, and dispersion of exposures can be reduced by controlling the sum of the pulse widths of the applied driving signals according to the light correction information of each LED.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention uses a light emitting element such as a light emitting diode or a light amount control element such as a liquid crystal to control the exposure of a photosensitive recording medium according to an image signal, thereby producing an image. The present invention relates to an image recording device for recording.

Conventional configuration and its problems One of the voltage value, current value, or time width of a drive signal applied to a light-emitting element such as a large number of light-emitting diodes arranged linearly or in a staggered manner, or a light amount control element such as a liquid crystal. By controlling both according to image signals and exposing a photosensitive recording medium such as a photosensitive selenium drum with the light emitted from each light emitting element or the light emitted from a constant amount of light source and transmitted through each light amount control element. , the image corresponding to the image signal (
Image recording devices that record latent images or visible images are known.

FIG. 1 is a block diagram showing the configuration of a conventional image recording apparatus as described above.

In this figure, 11 is an input terminal into which image signals are input in series, 12 is a light emitting diode (abbreviated as LED) drive amplifier circuit, 13 is an LED array section, 14 is a scanning clock circuit, and 15 is a recording section.

LED array part 1 part 3 LED array 13a formed by arranging a plurality of LEDs in a straight line or in a staggered manner along the straight line, and an optical lens or focusing optical fiber for condensing the light emitted by the LED array 13a. The optical system 1 and 3b are composed of optical systems 1 and 3b. The recording section 15 includes a photosensitive selenium drum 15a, which is a photosensitive recording medium, a charging section 15b, a developing section 15c, and a transfer section 15 arranged around the drum.
d.

It is composed of a cleaning section 15e and the like. The LED drive amplifier circuit 12 has the same number of amplifiers as the number of LEDs in the LED array 13a, the input of each of these amplifiers is coupled to the input terminal 11, and the output is connected to the corresponding L of the LED array 13a.
Each is combined with ED.

The recording operation will be explained below.

The image signal of the image to be recorded is serially input to the external input terminal 11 in synchronization with the scan clock output from the scan clock circuit 14. Each amplifier in the LED driving amplifier circuit 12 selectively operates sequentially in synchronization with the input of the image signal according to the scanning clock output from the scanning clock circuit 14.
Drive signal with voltage value according to image signal (time width is constant)
is applied to the corresponding LED. For example, when recording a black and white image, when a "black" image signal is input, the selected amplifier outputs a drive signal of a constant voltage value, causes the corresponding LED to emit light, and produces a "white" image. When the signal is input, the selected amplifier outputs a drive signal of O volts (does not output a drive signal) and does not cause the corresponding LED to emit light. Each LED on the LED array 13a is driven in this way.
The light emitted from the drum is imaged onto the photosensitive selenium drum 15a via the optical system 13b.

The photosensitive selenium drum 15a is rotated in the direction of the arrow in the figure by a driving means not shown in the figure. L
The LED on the ED array 13a is a photosensitive selenium drum 15.
They are arranged in the axial direction of a. Photosensitive selenium drum 15
The surface of a is uniformly charged to a specific polarity when passing through the charging section 16b, and then exposed to light from the LED array 13a, thereby recording an electrostatic latent image corresponding to the image signal. The recorded portion of this electrostatic latent image is sent to the developing section 15c and developed, and the resulting developed image (toner image) is transferred onto plain paper (not shown) at the transfer section 1sd. This plain paper is sent from the transfer section 15d to a fixing section (not shown in the figure), where it undergoes a fixing process and becomes a hard copy. After the residual toner is removed from the portion of the photosensitive selenium drum 15a that has passed through the transfer section 16d by the beam forming section 15e, it is sent to the charging section 15b again.

That is, in this example, the LED drive amplifier circuit 12
Main scanning is performed by sequentially selecting each LED of the ED array 13a, and sub-scanning is performed by rotating the photosensitive selenium drum 15a.

In addition, by adopting a matrix circuit, LED
The amplifier in the drive amplifier circuit 12 is connected to the L of the LED array 13a.
A conventional example in which the number is smaller than the number of EDs is also known. In addition, in order to cope with the increase in recording speed, the image signals for one scanning line are temporarily stored in the buffer memory, and then all the amplifiers in the LED drive amplifier circuit 12 are operated at the same time, and the LED array 1
A conventional example is also known in which the light emitting time allocated to each LED element is increased by driving all the LEDs on 3a at the same time according to corresponding image signals in the buffer memory.

Now, the biggest technical problem with the above-mentioned image recording apparatus is that variations in the characteristics of the light emitting elements or light quantity control elements, unevenness in the light quantity of the optical system, etc. cause variations in the amount of exposure of the photosensitive recording medium. As a result, the recording density becomes non-uniform and the quality of the recorded image deteriorates.

In contrast, in the past, LEDs with uniform characteristics were used.
This is dealt with by configuring the array 13a, but the LED
Since the manufacturing yield of the LED array 13a is poor and the LED array 13a requires a sorting operation, there is a problem that the price of the LED array 13a increases. Further, even if the LED array 13a with less variation in light intensity is obtained in this way, there is still a problem that recording density unevenness due to unevenness in the light intensity of the optical system 13b such as an array of convergent optical fibers remains.

OBJECT OF THE INVENTION The present invention solves the above-mentioned conventional problems.Even if the conditions regarding variations in the characteristics of the light emitting element or the light amount control element, the unevenness of the light amount of the optical system, etc. are relaxed compared to the conventional ones, the recording density does not change. An object of the present invention is to provide an image recording device that can record high-quality images.

Structure of the Invention The present invention provides means for storing light amount correction information for each light emitting element or light amount control element for controlling exposure of a photosensitive recording medium, and means for storing light amount correction information for each of the light emitting elements or light amount control elements. By providing a means for correcting the width (application time) according to corresponding light amount correction information stored in the means, the amount of exposure on the photosensitive recording medium for each of the light emitting elements or for each of the light amount control elements can be adjusted. The aim is to suppress the variation in the results and achieve the above-mentioned objective.

To supplement the explanation, when a constant voltage or current is applied to a light emitting element or a light amount control element, the brightness obtained on the photosensitive recording medium is L (lux), and the duration of that brightness is T (seconds). ), then the exposure amount K (lux - seconds)
It is given by Hani-LT. If the value of K is kept constant, the recording density can be made uniform, but in general, the value of L differs from element to element due to variations in the characteristics of the light emitting elements and light amount control elements, and unevenness in the amount of light in the optical system. Therefore, the present invention measures the value of L for each element in advance, obtains and stores light intensity correction information for each element to compensate for variations in the L value, and then adjusts each element according to the light intensity correction information during recording. By correcting the time width of the drive signal, it is possible to eliminate variations in values from element to element.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 2 is a block diagram of an image recording apparatus according to an embodiment of the present invention. In this figure, the symbols 11°12.13,
The parts marked 14 and 15 are respectively similar to the corresponding parts in FIG. However, in addition to the scan clock, the scan clock circuit 14 sends an address signal to the ROM 16, which will be described later, and a control signal to the buffer memory 17. 16 is ROM
(Read-only memory) This ROM1e has LE
Each LE making up the ED array in D array part 1 part 3
Light amount correction information for each D is stored in advance.

17 is a buffer memory that stores image signals for one scanning line, and 18 is a time width correction circuit.

Then, the binary image signals that are serially input to the input terminal 11 are stored in the buffer memory 17. When the image signal for one scanning line is stored in the buffer memory 17, the scanning clock circuit 14 controls the buffer memory 17 by a control signal.
The image signal is read out from the buffer memory 17 by repeating it n times at a period T/n which is 1/n of one scanning line period T.
It is input to the time width correction circuit 18. In synchronization with the reading of this image signal, the scanning clock circuit 14 updates the address signal in the ROM 16, and causes the ROM 1e to repeatedly output light amount correction information for each LED n times to the time width correction circuit 18.

The time width correction circuit 18 outputs a pulse with a constant pulse width for all "black" image signals when reading out the image signal for the first time, and from the second time onwards, the time width correction circuit 18 outputs a pulse with a constant pulse width for all the "black" image signals, and at each time after the second time, the time width correction circuit 18 outputs a pulse with a constant pulse width for all the "black" image signals. A pulse with a constant pulse width narrower than the first pulse is output for the black image signal, or is not output.The amplifier corresponding to each LED in the LED drive amplifier circuit 12 receives input from the time width correction circuit 18. A signal obtained by amplifying the pulse is applied to the corresponding LED as a drive signal.

That is, in this embodiment, each LED is scanned n times and the total time of the pulse width of the drive signal applied to each LED is controlled according to the light amount correction information of each LED, thereby canceling out the variation in the amount of exposure. It is something.

To simplify the explanation, the case where n=2 will be explained in detail with reference to FIG.

FIGS. 3A and 3S show the brightness Lf and light amount correction information Ti for each LED. FIG. 3C is a waveform diagram of the binary image signal, and FIG. 3D is a waveform diagram of the drive signal for each LED. Note that an LED array generally consists of several dozen LEDs.
It is composed of D, but here, to simplify the explanation, it is composed of L.
The explanation is based on the assumption that there are 10 EDs.

During the first scanning period of each LED, the time width correction circuit 18 maintains a constant pulse width α for all 7 black image signals.
In order to output pulses of i=2°3, 4 . . . corresponding to the "black" image signal, as shown in FIG. 5. 8. Drive signal with pulse width α for each of the 9 LEDs (voltage value is constant)
is applied. In the second scanning period, a pulse with a constant pulse width β (α) is applied only to the “black” image signal corresponding to the LED whose light intensity correction information TiO value exceeds the standard value 100. Therefore, as shown in FIG. 3d, a drive signal with a pulse width β is applied only to the LED with i=3.5.9. That is, the time width α of the drive signal for the LED whose Li value is equal to or higher than the reference value 100,
By increasing the time width of the drive signal for the LED whose value is less than the reference value 100 by β to α+β, the exposure amount is made uniform. It should be noted here that if the number of time divisions n is set to 3 or more, the time width of the drive signal can be corrected more finely, so that the compensation accuracy of the exposure amount is improved.

Note that, as shown by the broken line in FIG. 3d, a small amplitude pulse having the same pulse width α as the first pulse may be applied to the LED as the second and subsequent drive signals.

Further, similar time width correction can be performed by reading out the buffer memory 17 and ROM 1e in parallel, parallelizing the time width correction circuit 18, and operating all the amplifiers in the LED driving amplifier 12 at the same time. .

For example, as shown in Figure 4, in the first half of the scanning period, all L
Apply a drive signal with a constant pulse width to the ED all at once.
Assume that a "black" image signal is input. Same below)
In the second half period, a drive signal with a narrow pulse width (or a drive signal with the same pulse width and small amplitude as shown by the broken line) is simultaneously applied only to the LEDs whose Li value is less than the reference value. Alternatively, as shown in Fig. 5, a driving signal with a constant pulse width is applied to all LEDs at once in the first half of the scanning period, and a drive signal with the same pulse width (or a pulse with a different pulse width) is applied only to the LEDs with a small Li value in the second half. A certain number of drive signals (width) are applied all at once. In either example, if the number of divisions n of the scanning time is 3 or more, more accurate correction is possible.

When all the LEDs are driven in parallel in this way, if the exposure amount is constant, the scanning period T can be shortened compared to when each LED is driven in series, so that the recording speed can be improved.

Although the embodiment has been described above in which correction is performed for each element, it is also possible to make a plurality of elements into one block and perform correction on the average amount of light for each block. When constructing an LED, a plurality of chips each having a plurality of elements are connected to form an array of a predetermined length. In such a case, variations in each element within a chip are relatively small, and variations between chips tend to be large. Therefore, it is possible to obtain a correction effect by setting one chip as one block, setting a correction value based on the average light intensity, and applying it within the block. In this case, the correction circuit can be simplified.

Although embodiments using LEDs as light emitting elements have been described above, the light emitting elements are not limited to LEDs.

Furthermore, the present invention can be similarly applied to an image recording apparatus configured to form an image on a photosensitive recording medium by using light from a light source via a light amount control element such as a liquid crystal, instead of directly exposing light with a light emitting element. .

Furthermore, in each of the above embodiments, a developed image is obtained by recording an electrostatic latent image of an image on a photosensitive selenium drum and developing the latent image, but the developed image is directly recorded by exposure. It is clear that the present invention can be similarly applied to image recording apparatuses using photosensitive recording media.

As described in detail, according to the present invention, means for storing light amount correction information for each light emitting element or light amount control element;
By providing means for correcting the time width of the drive signal for each light emitting element or each light amount control element in accordance with the corresponding light amount correction information stored in the above means, the amount of exposure on the photosensitive recording medium can be made uniform. To achieve this, the recording density is -
In addition to being able to store high-quality images such as It is possible to obtain effects such as:

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional image recording device, FIG. 2 is a block diagram showing the configuration of an image recording device according to an embodiment of the present invention, and FIG. 3 is an explanation of the operation of the image recording device shown in FIG. 2. 4 is a waveform diagram illustrating a modification of the image recording device shown in FIG. 2, and FIG. 6 is a waveform diagram illustrating another modification of the image recording device shown in FIG. 2. It is a diagram. 11... Image signal input terminal, 12...
LED drive amplifier circuit, 13...LED array section, 13a...LED array, 13b...
・Optical system, 14...Scanning clock circuit, 16.
... Recording section, 15a ... Photosensitive selenium drum, 16 ... ROM, 17 ... Buffer memory, 18 ... Time width correction circuit . Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 1'0J Figure 2 Figure 3 1-l

Claims (1)

[Claims] The time width of a drive signal for each of the plurality of light emitting elements or light amount control elements is controlled according to the image signal, and a photosensitive recording medium is exposed with light emitted by each of the light emitting elements or light passing through each of the light amount control elements. An image recording device that records an image corresponding to the image signal on the same photosensitive recording medium by recording light amount correction information or Storage means for storing average light amount correction information of a block consisting of a plurality of elements, and a time period for correcting the time width of a drive signal for each of the elements or the block according to the corresponding light amount correction information stored in the storage means. The apparatus comprises a width correction means and a buffer memory for storing an image signal for at least one scanning line, and reads out the image signal n times repeatedly within one scanning line period T from the buffer memory and outputs it to the time width correction means. An image recording apparatus that corrects variations in exposure amount on the photosensitive recording medium by outputting light amount correction information from the storage means to the time width correction means n times in synchronization with the readout of the image signal.