JPH01209462A - Recording device - Google Patents

Abstract

PURPOSE:To improve the resolution of a recording picture by detecting the electrostatic charging potential of a photosensitive body by a measuring means and varying the quantity of light emission of a LED as an exposure light source according to an electrostatic charging potential state, and thus obtaining a recording surface which is nearly constant in line thickness at all times. CONSTITUTION:A surface potential measuring sensor 2 as the measuring means for the surface potential measures the electrostatic charging potential of the cylindrical photosensitive body 1. The voltage VR1 of a reference voltage setting circuit 31, the voltage VR2 of a reference voltage setting circuit 32, and the voltage VR3 of a reference voltage setting circuit 33 are supplied to respective input terminals of an operational amplifier 34 and the voltages VR1-VR3 are so set that VR1>VR2>VR3. The reference voltage setting circuit 31 is selected when the electrostatic charging potential of the photosensitive body 1 is high, the reference voltage setting circuit 33 is selected when the electrostatic charging potential of the photosensitive body 1 is low, and the reference voltage setting circuit 32 is selected when the electrostatic charging potential of the photosensitive body 1 is within a normal range. Therefore, even of the electrostatic charging state of the photosensitive body 1 changes owing to an external factor, recording is uniform in line thickness. Consequently, the resolution is prevented from deteriorating.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a recording device, and particularly to a recording device using an electrophotographic recording method using an LED recording head as a light source.

[Conventional technology]

In recording devices using electrophotographic recording methods that use conventional LED recording heads as light sources, the charging characteristics of the cylindrical photoreceptor deteriorate when used continuously for long periods of time, fluctuate due to temperature changes, and fluctuate due to humidity changes. However, the exposure was performed at a constant light amount set in advance.

FIGS. 3(a) to 3(c) are characteristic diagrams showing the correlation between the charging potential and the exposure amount for explaining the recording characteristics of the photoreceptor, respectively.

Figure 3(b) shows the normal charging potential VS with respect to the reference potential VS.
c1 and is exposed with a certain amount of light. When the charge is removed from the exposed portion D1 and a reversal phenomenon occurs, a developing material (hereinafter referred to as toner) is deposited on this portion. Next, see Figure 3 (
A) shows a case where the charging potential VC2 is high and shows a case where exposure is performed with a certain amount of light. Compared to FIG. 3(b), the charge in the exposed area D2 is insufficiently discharged, and even when the charge remains and is developed, not enough toner is applied, and the recorded image obtained by transferring the toner onto plain paper has thinner lines. When recording solid black, the spaces between the scanning lines may not be filled in and appear as white stripes.

FIG. 3(c) shows a case where the charging potential Vc3 is low, and shows a case where exposure is performed with a certain constant amount of light. in this case,
Compared to 2nd [J(b), the exposed area D3 is wider, and when developed, too much toner is applied, and the recorded image has thicker lines and degrades resolution.

[Problem to be solved by the invention]

The above-mentioned conventional recording device performs exposure with a constant amount of light, so when the charging characteristics of the photoreceptor change depending on the usage conditions and usage environment, the recording line becomes thinner or thicker, which deteriorates the resolution. There is.

[Means to solve the problem]

A recording apparatus of the present invention includes a photoconductor whose charged surface potential is changed by exposure to light, and an LED recording head consisting of a plurality of arranged LEDs that illuminate the photoconductor. means for measuring the surface potential; comparison means for comparing the measured potential with a preset reference voltage and outputting a control signal according to the comparison result; and receiving the control signal and adjusting the light amount of each of the LEDs. It is configured to include one stage of LED drive driving stage for changing.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram of a first embodiment of the present invention.

In FIG. 1, the charged potential of a cylindrical photoreceptor 1 is measured by a surface potential measuring sensor 2 serving as surface potential measuring means. The part surrounded by the dashed line is the LSI LE
A D drive circuit is shown. The charged potential of the photoreceptor 1 measured by the surface potential measurement sensor 2 is determined as a small voltage level by the comparator 3.
and is input to comparator 4. The comparator 3 outputs a high-level control signal when the charged potential of the photoreceptor 1 is high, that is, as shown in FIG. 3(a) described above.

The comparator 4 outputs a high-level control signal when the charged potential of the photoreceptor 1 is low, that is, as shown in FIG. 3(c) described above.

The NOR circuit 5 inputs the outputs of the comparators 3 and 4, and when the charged potential of the photoreceptor 1 is within the normal range, that is, the third
When shown in Figure (b), a high level control signal is output. Note that a reference voltage setting circuit 6 and a reference voltage setting circuit 7 are connected to the comparators 3 and 4, respectively, and are compared with the measured potential from the surface potential measurement sensor 2 in the comparators 3 and 4. The comparators 3 and 4, the NOR circuit 5, and the reference voltage setting circuits 6 and 7 constitute a comparison means.

A control signal that detects the charged potential state of the photoreceptor 1 passes through input terminals 8, 9, and 10, and is sent to the latches 11, 12, and 12. The signal is input to the latch 13. Further, a latch timing signal 15 is supplied to the latches 11, 12, and 13 via the input terminal 14, and determines the latch timing of the control signal input to the latches 11, 12, and 13. Although the latch timing can be selected arbitrarily, it is usually performed immediately before the photoreceptor 1 is exposed.

The latched control signal is transmitted to the CMOS switch 16, C
MOS switch 17. The signal is input to the CMOS switch 18. The CMOS switches 16, 17, and 18 are rendered conductive when the input control signals are at high level. Depending on the charged potential state of the photoreceptor 1, the CMOS switches 16 and 17
．． 18 becomes conductive.

Resistor 1 connected to each CMOS switch 16, 17, 18
9. Resistance 20. The resistance value of the resistor 21 is set as shown in equation (1), where the resistance value of the resistor 19 is R19, the resistance value of the resistor 20 is R2o, and the resistance value of the resistor 21 is R21.

R19<R20<R2v...<1) Resistor 19, 20
．． 21 are connected to the negative input terminal of the operational amplifier 22 via CMOS switches 16, 17, and 18, respectively, so that one of them is connected to the operational amplifier 22. LED
The current I flowing through the operational amplifier 22 is determined by the voltage value VR of the reference voltage setting circuit 24 connected to the operational amplifier 22 and the resistance 19°20.
The resistance value R of one resistor selected from 21 and the formula (
2).

I = VR/R...(2) Therefore, when the charged potential of photoreceptor 1 is within the normal range, resistor 2
0 is selected, and the current flowing through the LED 23 is equal to the normal current 1.0 included in the current I. becomes.

When the charged potential of photoreceptor 1 is high, resistor 19 is selected, and L
The current flowing through the ED 23 becomes larger than the normal current 11, and the amount of light emitted from the LED 23 also increases.0 The increase in the amount of emitted light means that the amount of exposure to the photoreceptor 1 increases, as shown in FIG. 3(a) above. The width of the exposed area D2 shown in FIG. 3(b) is almost equal to the width of the exposed area D1 shown in FIG. 3(b), and the line thickness becomes normal when recorded.

When the charged potential of the photoreceptor 1 is low, the resistor 21 is selected and L
The current flowing through the ED 23 becomes smaller than the normal current 11, and the amount of light emitted from the LED 23 also becomes smaller. As the amount of emitted light decreases, the amount of exposure to the photoreceptor 1 also decreases, and the width of the exposed portion D3 shown in FIG. 3(c) becomes equal to the width of the exposed portion D3 shown in FIG. 3(b), When recorded, the line thickness will be normal.

In FIG. 1, the operational amplifier 22 and the transistor 25 function so that the above-mentioned formula (2) holds even against external fluctuations in the power supply VDD, and the transistor 26 and the transistor 27 form a current mirror circuit. When the CMOS switch 28 is in a conductive state, a current having a current value equal to the current flowing through the transistor 26 flows through the transistor 27, and is supplied to the LED 23 via the output terminal 29. A control signal is applied to the signal terminal 30 to make the CMOS switch 28 conductive or non-conductive.

CMOS switch 28. Transistor 27. Output terminal 2
9. The same number of signal terminals 30 as the number of LEDs to be lit are prepared.

FIG. 2 is a block diagram of a second embodiment of the invention.

As shown in FIG. 2, the second embodiment uses a reference voltage value instead of a resistor connected to an operational amplifier 22 to change the current value of the LED 23 in the LED drive circuit shown in the dashed line in FIG. This is what I decided to change.

That is, as shown in FIG. 2, the voltage across the resistor 35 and the CMOS switch 1 are applied to each input terminal of the operational amplifier
Voltage V of the reference voltage setting circuit 31 via 6, 17 and 18
R1, the voltage vR2 of the reference voltage setting circuit 32, and the voltage VR of the reference voltage setting circuit 33 are supplied. Here, the voltage values of voltages V R1, V R2, V R3 (') are V
The relationship is R1>VH2>VRg.

Now, when the charged potential of the photoreceptor 1 is high, the reference voltage setting circuit 31 is selected, and when the charged potential of the photoreceptor 1 is low, the reference voltage setting circuit 33 is selected, so that the charged potential of the photoreceptor 1 is normal. When the voltage is within the range, the reference voltage setting circuit 32 is selected.

As a result, even if the charged potential state of the photoreceptor 1 changes due to external factors, the recording will have a negative line thickness.

〔Effect of the invention〕

As explained above, the present invention detects the charged potential of the photoreceptor using a surface potential measuring means, and changes the amount of light emitted from the LED as an exposure light source according to the charged potential state, thereby producing a line with a constant thickness. Since a recording surface of a large size can be obtained, there is an effect that the resolution and image quality of the recording surface can be improved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a first embodiment of the present invention, FIG. 2 is a block diagram of a second embodiment of the present invention, and FIGS.
c) is a characteristic diagram showing the correlation between the charging potential and the exposure amount for explaining the recording characteristics of each photoreceptor. 1... Photoreceptor, 2... Surface potential measurement sensor, 3, 4
...Comparator, 5...NOR circuit, 6,7...Reference voltage setting circuit, 8,9,10.14...Input terminal, 1
1゜12.13...Latch, 15...Latch timing signal, 16.17.18...CMOS switch,
1.9.20.21...Resistor, 22...Operation amplifier, 23...LED, 24...Reference voltage setting circuit, 2
5゜26.27...transistor, 28...CMO
S switch, 29... Output terminal, 30... Signal terminal, 31° 32.33... Reference voltage setting circuit, 34...
- Operational amplifier, 35...resistance.

Claims (1)

[Claims] a photoreceptor whose charged surface potential is changed by exposure to light;
L consisting of a plurality of arranged LEDs that illuminate the photoreceptor
In a recording apparatus equipped with an ED recording head, means for measuring the surface potential of the photoconductor, and comparison means for comparing the measured potential with a preset reference voltage and outputting a control signal according to the comparison result. and an LED driving means for changing the amount of light of each of the LEDs in response to the control signal.