JPH0532022A - Image formation device - Google Patents

Abstract

PURPOSE:To make it possible to obtain test print which allows the offset of a position for an image to be recognized by generating a masking signal for inhibiting the formation of an image in a specified area, driving a means for counting in synchronization with the end of the masking signal and modulating a laser beam in accordance with a count state. CONSTITUTION:A laser beam printer is equipped with a printing function for determining whether the ability to form an image is normal. In this case, a three-bit counter is provided which consists of flipflops 1 to 3 for entering a masking signal which inhibits a reset input from forming an image in a specified area. This counter is allowed to start the count if the masking signal 7 is false. In addition, if outputs 8 to 10 from the flipflops 1 to 3 are totally L, a pulse waveform is generated from a 3-input NOR circuit 4, and this waveform is synchronized with a basic clock 6 using the flipflop 5 to generate a pattern signal 11 for test print which modulates the laser beam.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a laser beam printer which forms an image using an electrostatic recording system having a test print pattern generating circuit.

[0002]

2. Description of the Related Art FIG. 8 shows the structure of a general laser beam printer. The image forming operation of the laser beam printer will be described below with reference to this drawing.

An image signal (VDO signal) 101 is input to the laser unit 102. Reference numeral 103 denotes a laser beam which is on / off modulated by the laser unit 102. A motor 104 causes the rotating polygon mirror (polygon mirror) 105 to rotate steadily. Reference numeral 106 denotes an imaging lens, which is the laser beam 1 changed by the polygon mirror 105.
07 is imaged on the photosensitive drum 108 which is the surface to be scanned. Therefore, the laser beam 107 modulated by the image signal 101 is horizontally scanned (scanning in the main scanning direction) on the photosensitive drum 108 to form an electrostatic latent image on the photosensitive drum 108. Reference numeral 109 is a beam detection port for taking in a laser beam passing through a predetermined scanning position from a slit-shaped entrance. The laser beam entering from the entrance is guided to the photoelectric conversion element 111 through the inside of the optical fiber 110, and is converted into an electric signal by the photoelectric conversion element 111. This electric signal becomes a horizontal synchronizing signal (hereinafter referred to as a BD signal) after being amplified by an amplifier circuit (not shown). 112
Is a transfer paper, and the latent image formed on the photosensitive drum 108 is visualized by a developing device (not shown) into a toner image.
Transferred to 2.

Next, a control signal for forming an image will be described with reference to FIG. 121 is the photosensitive drum 108
The upper toner image is transferred onto the transfer paper 121.
From 21, an area (image forming area) 122 that can be exposed by a laser is provided so as not to protrude. An image controller (not shown) outputs the image signal 126, and is often a controller other than a control unit that handles a control signal such as a BD signal or an external computer. In such a configuration, the image forming area 122 is provided by the mask signal 125 described later so that the photoconductor is not exposed even when the image controller turns on the image signal in the non-image area. Therefore, the image forming area 122 has different sizes according to the size of the transfer paper 121.

An image forming signal for forming an image corresponding to one main scanning line 123 on the transfer paper 121 will be described. The BD signal 124 is the synchronization signal in the main scanning direction described above, and other signals are generated in synchronization with this BD signal. The mask signal 125 is a signal that is turned on and off in accordance with the mask area 122 on the transfer paper 121. With this, laser emission by the image signal 126 having image information is prohibited, and exposure to the outside of the image forming area 122 is prohibited. .

In this way, an image for one page is formed by repeating the image formation for each main scan.

Such a laser beam printer has a test print function in order to check whether the image forming function is normal. This test print will be described with reference to FIG. Reference numeral 131 is a transfer paper on which a test print pattern is printed, and has a test print pattern consisting of a plurality of vertical lines in the image forming area 132. Reference numeral 124 is a BD signal, and 125 is a mask signal, which is the same as that described in the previous example. An image signal 133 for printing a test print pattern is a signal which is turned on at equal intervals in synchronization with the BD signal. FIG. 11 shows an example of a circuit for generating this signal, and FIG. 12 shows its timing chart.

The flip-flops 143, 144, and 145 constitute a counter of a 3-bit counter and count the basic clock CLK150. This counting is permitted by a signal obtained by inverting the BD signal by the inverter 142. That is, when the BD signal is at the H level, the counter is stopped, and when the BD signal is at the L level, counting is performed. This 3-bit counter has eight states, and a circuit for generating a pulse in one of the eight states has three states.
The input NOR is 146. The output of this 3-input NOR is output to the basic clock 15 using a flip-flop 147.
Synchronize to 0. The test print pattern created in this way determines whether the mask signal is output by the signal obtained by inverting the mask signal by the inverter 141. That is, when the mask signal is at H level, the test pattern is not output and L
At the level, a test print pattern is output. In this way, the test print pattern is generated on the BD
Start in sync with the signal. Next, the timing chart will be described with reference to FIG.

The basic clock 161 is a reference signal for all signals and is assumed to be sufficiently high speed. First, when the BD signal 162 is input, the flip-flops 143, 14
4, 145 are cleared and fixed to the initial state. The signals are 163, 164, and 165, respectively.

The counter returned to the initial state starts counting up in synchronization with the BD signal.

Some time after the start of counting up,
The mask signal 167 is released. Since the release timing differs depending on the size of the transfer paper, there is little possibility that the test print pattern is written at the same time when the mask is released. That is, the mask signal and the test print pattern 168
Has nothing to do with.

In the test print pattern thus formed, whether or not fluctuations (jitter) have occurred in the scanner motor, whether the image forming function is normal, etc.
Used for various diagnostics.

[0013]

[Problems to be solved by the invention] However,
This test print pattern has a drawback in that it is not possible to read from the pattern how much the transfer paper 131 is relative to its original position.

In order to clarify the displacement of the transfer paper 131, it is necessary to print a pattern that fills the entire image forming area with black, or configure the pattern with horizontal lines. However, when painting the entire surface in black, not only is the toner wasted wastefully, but the fluctuation of the scanner motor is not known, and the horizontal line pattern consumes less toner, but the fluctuation of the scanner motor does not occur. After all, it has the drawback of not knowing.

An object of the present invention is to solve the above technical problems and to provide an image forming apparatus for performing a test print capable of recognizing a positional deviation of an image without deteriorating the function of the test print.

[0016]

According to the present invention, an image is formed by adopting a structure in which generation of a test print pattern is started in synchronization with a mask signal, not in synchronization with a BD signal. This makes it possible to recognize the start position of the area from the test print pattern and realize a test print pattern generation circuit capable of identifying the deviation of the transfer paper.

[0017]

【Example】

FIG. 1 shows a control signal generation circuit in the first and first embodiments. The overall configuration of the first embodiment is similar to that of FIG. 8, and its description is omitted. Flip Flop 1, 2,
3 constitutes a 3-bit counter, and a clock signal 6
To count. Since the mask signal 7 is input to the reset inputs of these flip-flops, this counter starts counting when the mask signal 7 is false. When the mask signal 7 becomes false, the counter starts counting. When all of the flip-flop outputs 8, 9, 10 of the 3-bit counter become L, the 3-input NOR circuit 4 generates a pulse waveform. This waveform is synchronized with the basic clock 6 by the flip-flop 5 and becomes the pattern signal 11 of the test print.

Next, the details of these waveforms will be described with reference to FIG. The clock 15 is a basic clock and is the same as that described above. Mask signal 16
However, their outputs 17, 18, and 19 remain at the L level during the tru, because the flip-flops are reset. When the mask signal 16 is released, the counter starts counting and outputs a test pattern. The flip-flop 5, which generates a pulse signal when all the outputs from s1 to s3 are at the L level, immediately generates a pulse signal when the mask signal is released. This first pulse corresponds to a signal corresponding to mask release, that is, an image forming area. FIG. 3 shows a test print pattern formed by these image signals. As can be seen from this figure, it is understood that the image is formed from the left end of the image forming area. It is possible to know at which position on the transfer paper 21 the image forming area is formed by seeing how much the leftmost line is. The image signal 25 is a combination of the test print signal 11 and the image signal from the image controller, and the pulse waveform of the image signal 25 is the pulse of the test print signal. If the timing at which the mask signal 24 is released changes, the image effective area changes accordingly, and there is no problem.

Therefore, by using this method, it is possible to easily identify the image forming area as well as to check for the misalignment of the scan.

2. Next, a second embodiment of the present invention will be described with reference to FIG.

In the first embodiment, the example in which the test print pattern is generated in synchronization with the mask signal has been described. In the second embodiment, an example in which a line is forcibly drawn at the start and end of the mask signal will be described. FIG. 4 is a diagram when the present invention is implemented in a case where the image forming area and the test print pattern are displaced as in the conventional example. A pulse 31 of the image signal 30 can draw a line at the left end of the image forming area, and a pulse 32 of the image signal 30 can draw a line at the right end of the image forming area. The other BD signal 28 and mask signal 29 are the same as those described above.

Now, a circuit for generating the 31 and 32 pulses will be described with reference to FIG.

The mask start signal 40 and the mask end signal 37 are pulses generated when a counter (not shown) operating in synchronization with the BD signal reaches a certain value. The mask start signal 40 is the mask signal 4
2 is defined as the start timing, and the mask end signal 37 is
It defines the end timing of the mask signal 42. These mask start signal 40 and mask end signal 37
The mask signal 42 can be generated by inputting the signal to the JK flip-flop 35. Further, in order to generate the pulses 31 and 32 of the image signal 30 described above, the mask start signal 40 and the mask end signal 37 are synthesized by the OR circuit 36 and created.
However, if the mask end signal 37 is used as it is, a pulse is generated during the mask period and the transfer paper is not exposed. Therefore, the flip-flop 34 is delayed by one clock by one stage. A test pattern as shown in FIG. 4 can be obtained by synthesizing the test pattern 41 created by this circuit with the BD-synchronous test pattern described in the above-mentioned conventional example.

In this example, in order to draw a plurality of vertical lines in the image forming area, they are combined with the above test pattern,
Of course, if it is sufficient to draw a line at the left end and the right end of the image forming area without combining them, there is no need to combine them.

Third Embodiment A third embodiment will be described with reference to FIG.

In this example, a case where the example described in the second embodiment is applied in the sub-scanning direction will be described. Also in the sub-scanning direction, there is a signal corresponding to the mask signal in the main scanning direction that prohibits image formation. In this description, this signal is referred to as the top erase signal 53, and the third embodiment will be described below.

The top erase signal 53 is turned off a few millimeters from the leading edge of the transfer sheet and turned on a few millimeters before the trailing edge of the transfer sheet in the sub-scanning direction.

A pulse may be generated at the switching point of this signal and used as a test pattern. For example, it can be realized by using a circuit as shown in FIG. 7 and picking up a change point.

The circuit of FIG. 7 will be briefly described.

The outputs of the two flip-flops are inverted at the change point of the top erase signal. At this time, the flip-flop 50 changes one clock earlier of the clock 57 and the flip-flop 51 changes later one clock of the clock 57. Therefore, if these outputs are received by the XOR circuit, pulses can be output only at the change points. It is possible.

By the above, it can be easily realized in the sub-scanning direction.

[0032]

As described above, by using the present invention, it is possible to realize a test print pattern capable of easily reading the image forming range without consuming a large amount of toner. This makes it possible to check the image formation position only with the test print function of the main body without connecting a special test pattern generator during production and performing test printing, thus simplifying the manufacturing process. There is a merit that you can expect productivity improvement and cost merit.

Further, the same effect is exhibited in the maintenance in the market.

[Brief description of drawings]

FIG. 1 is a circuit diagram for implementing a first embodiment of the present invention.

FIG. 2 is a timing chart when the first embodiment of the present invention is implemented.

FIG. 3 is a test pattern and a signal when the first embodiment of the present invention is carried out.

FIG. 4 shows test patterns and signals when the second embodiment of the present invention is carried out.

FIG. 5 is a circuit diagram when a second embodiment of the present invention is implemented.

FIG. 6 is a timing chart when the second embodiment of the present invention is implemented.

FIG. 7 is a circuit diagram when a third embodiment of the present invention is implemented.

FIG. 8 is a diagram illustrating a configuration of a laser beam printer.

9 is a diagram for explaining an image forming operation of the laser beam printer in FIG.

FIG. 10 is a conventional test pattern and signal.

FIG. 11 is a diagram of a conventional test printer pattern generation circuit.

FIG. 12 is a timing chart of a conventional test pattern generation circuit.

[Explanation of symbols]

1 to 3, 5, 34, 35, 50, 51 Flip flops 6, 15, 38, 43, 57 Clock signals 7, 16, 24, 29, 42, 44 Mask signals 11, 20, 24, 29, 41, 46 patterns Signal 21, 26 Transfer paper 25, 30 Image signal

Claims (2)

[Claims] 1. An image forming apparatus for forming an image by scanning a photosensitive member with a laser beam modulated by an image signal, and a mask signal for inhibiting the formation of an image in a predetermined area, and a mask signal for ending the mask signal. An image forming apparatus comprising: a counting unit that starts counting in synchronization; and a test pattern generating unit that modulates a laser beam according to the state of the counting unit to print a test pattern. 2. An image forming apparatus for forming an image by scanning a photoconductor with laser light modulated by an image signal, and a mask signal for permitting the formation of an image in a predetermined area, and a mask signal synchronous with the mask signal. An image forming apparatus having a means for outputting a test pattern signal for turning on / off a laser beam.