JPH01218845A - Printing start position control apparatus of laser printer - Google Patents

Abstract

PURPOSE:To always start printing from an accurate printing start position, by clearing a timer and continuously outputting a sample holding signal and subsequently starting the counting operation of the timer when laser beam is detected by an optical sensor and stopping the output of the sample holding signal at the time of count-up. CONSTITUTION:At first, a signal SHON becomes a low level and a timer 1 is cleared and a flip-flop 2 is reset. Next, the signal SHON is reversed from a low level to a high level and the output SH of the flip-flop 2 becomes a low level to start the scanning of the certain range of laser beam. Next, the laser beam passes on an optical sensor to generate a printing range indication signal DF to input the same to the trigger terminal of the timer 1 and the timer 1 starts time counting operation. Next, the timer 1 is counted up to reverse a count-up signal CNTUP from a low level to a high level and the flip-flop 2 performs reset operation and the sample holding signal SH becomes a high level to finish a sample holding period.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a printing start position control device for a laser printer.

[Prior Art] Laser printers perform printing by placing information on a laser beam and scanning it on a drum to form a latent image, which is then transferred to printing paper.

In such a device, it is necessary to accurately manage the printing start position for each scanning line, and if this is insufficient, there is a problem that printing accuracy decreases and quality deteriorates.

Conventionally, an optical sensor is provided outside the printing start position of each scanning line, and a sample hold time is set from a position further outside the optical sensor to start scanning the laser beam.When the laser beam passes the optical sensor, This position is detected to determine the print start position, the sample hold time is ended, the laser beam is once turned off, and then the laser beam is turned on again from the print start position to start line scanning. The time from when the optical sensor detects the laser beam until the end of the sample hold time is managed using software.

This time is set to sufficiently compensate for the time it takes for the laser beam to pass through the light-receiving surface of the photosensor in order to ensure that the photosensor receives the laser beam, and to ensure that the detection output of the photosensor is accurately obtained. It is something that will be done.

[Problems to be Solved by the Invention] However, in the case where software is used to manage the time from when the optical sensor detects the laser beam until the end of the sample hold time, the microprocessor is If work is interrupted due to an interruption, etc., there will be a time lag, and as a result, the sample hold time will not end even when the print start position is reached, which may cause a lag in the print start position, which may affect the quality of the print. There was a problem with lowering it. However, if the interrupts being managed are disabled, a problem arises in that the microprocessor is unable to process at all during that time.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a print start position control device for a laser printer that can always start printing from an accurate print start position and improve printing quality.

[Means for Solving the Problems] The present invention scans a laser beam over a certain range and irradiates the optical sensor on the scanning line before starting the printing operation for each scanning line, and the laser beam is directed to the optical sensor. In the print start position control device of a laser printer, which determines the print start position of each scanning line by irradiation of the laser beam, it is cleared before scanning a certain range of laser beams, and then the time is counted in response to the irradiation of the laser beam to the optical sensor. A timer that starts the operation, and a sample and hold signal generation circuit that outputs a sample and hold signal for sample and hold following the timer's clear operation and stops outputting the sample and hold signal when the timer counts up are provided. The time from when the hold signal generation circuit generates a sample and hold signal until the timer starts counting time, and from when the timer starts counting time until the sample and hold signal generation circuit stops generating sample and hold signals. This is to manage the time of each person.

[Function] According to the present invention having such a configuration, the timer is cleared before scanning a certain range with the laser beam, and then the sample and hold signal is output from the sample and hold signal generation circuit, and then the optical sensor scans the laser beam. When detected, the timer starts counting, and when the timer counts up, the output of the sample and hold signal from the sample and hold signal generation circuit is stopped. Therefore, the time from when the timer starts counting until the sample and hold signal stops is managed by the timer, and therefore the printing start position can be managed accurately.

[Example] Embodiments of the present invention will be described below with reference to the drawings.

As shown in Figure 1, a laser printer has a low active sample hold signal SH and a low active print range instruction signal DF detected within the sample hold period, and among these, the sample hold signal SR is at a low level. The sample hold time A is the time from when the print range instruction signal DF is detected until the sample hold signal SH becomes high level. Managed. Among them, the sample hold time B particularly requires management accuracy in order to accurately set the printing start position.

Specifically, as shown in Fig. 2, a one-shot timer 1 and a flip-flop 2, which is a sample-and-hold signal generation circuit, are provided, and the set terminal (SET) of the flip-flop 2 and the clear terminal (CLR) of the timer 1 are connected to each other. They each supply a signal 5HON that enables sample and hold.

Further, an optical sensor (not shown) detects a laser beam and supplies a print range instruction signal bF to a trigger terminal (TRG) of the timer l.

The timer 1 outputs a count-up signal CNTUP from its output terminal (UP) and supplies it to the reset terminal (RESET) of the flip-flop 2.

A sample and hold signal SH is generated from the flip-flop 2.

The signal 5HON is a signal that becomes low active for a certain period of time as shown in FIG. 2 prior to the start of scanning a certain range of laser beams.

Next, the operation of this embodiment will be described based on FIG. 2.

First, in sequence number 1, the signal 5HON becomes low level, timer 1 is cleared, and flip-flop 2 is reset. As a result, the output CN5ET of timer 1 becomes determined and becomes low level. Furthermore, the output SH of the flip-flop 2 also becomes determined and becomes a high level.

In the next sequence 2, the signal 5HON is inverted from low level to high level. Therefore, the flip-flop 2 is set and its output SH becomes low level.

In this way, scanning of a certain range with the laser beam is started.

In the next sequence number 3, the laser beam passes over the optical sensor, a print range instruction signal DF is generated, and the timer 1
is input to the trigger terminal of the In this way, timer 1 starts a time counting operation.

In the next sequence NCL4, the time counting operation of the timer 1 ends and the count-up signal CNTUP is inverted from low level to high level. As a result, the flip-flop 2 performs a reset operation, the sample-and-hold signal SH becomes high level, and the sample-and-hold period ends.

Furthermore, in the 10th sequence NCL5, the signal S HON
becomes low level again, clears timer 1, and waits for the next line scan.

In this way, after the optical sensor detects the laser beam and the print range instruction signal DF is generated, the sample hold signal SH
Since the sample hold time B until it is stopped is managed by the one-shot timer 1, there will be no deviation in the time B. Therefore, the time at which the sample and hold signal SH is stopped is always accurate, and there is no possibility that the scan will lag until it reaches the print start position. Therefore, the positioning of the printing start position determined by the detection of the laser beam by the optical sensor is always accurate.

In this way, the printing start position of each line can be set with high precision.
Therefore, it is possible to perform high-quality printing without any printing deviation.

In the above embodiment, a one-shot timer was used as the timer, but it is needless to say that the invention is not limited to this.

Further, in the above embodiment, a case was described in which a flip-flop was used as the sample-and-hold signal generating circuit, but it is needless to say that the present invention is not limited to this.

[Effects of the Invention] As detailed above, according to the present invention, it is possible to provide a print start position control device for a laser printer that can always start printing from an accurate print start position and improve printing quality. It is.

[Brief explanation of the drawing]

The figures show an embodiment of the present invention, in which Fig. 1 is a timing diagram showing the timing relationship between the sample hold signal and the printing range instruction signal, Fig. 2 is a circuit diagram, and Fig. 3 is a signal of each part in Fig. 2. FIG. 3 is a waveform diagram showing waveforms. 1... One-shot timer, 2... Flip-flop, SH... Sample hold signal, DF... Print start instruction signal. Applicant's agent Patent attorney Takehiko Suzue Figure 2

Claims (1)

[Claims] A laser printer that scans a certain range of laser beams and irradiates them onto an optical sensor located on the scanning line before starting the printing operation for each scanning line, and determines the printing start position of each scanning line by irradiating the optical sensor with the laser beam. The print start position control device includes a timer that is cleared before scanning a certain range of laser beams and then starts a time counting operation in response to irradiation of the laser beam to the optical sensor; Subsequently, a sample and hold signal generation circuit is provided that outputs a sample and hold signal for sample and hold, and stops outputting the sample and hold signal when the timer counts up, and the sample and hold signal generation circuit generates the sample and hold signal. and the time from when the timer starts the time counting operation until the timer starts the time counting operation and the time from when the timer starts the time counting operation until the sample and hold signal generation circuit stops generating the sample and hold signal, respectively. Features: Print start position control device for laser printers.