JP3339752B2 - Laser recording device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser recording apparatus, and more particularly, to a laser recording apparatus having a beam detector for detecting a laser beam.

[0002]

2. Description of the Related Art A conventional laser recording apparatus will be described with reference to FIG. A laser beam 13 from a laser device 12 is emitted to a polygon mirror 14 rotated by a constant speed motor (not shown). Boligon mirror 14
The laser beam 16 deflected by the laser beam passes through the lens 15 and irradiates the photosensitive drum 19. That is, the laser device 1
The laser light from 2 is main-scanned on the photosensitive drum 19. The latent image formed on the photosensitive drum 19 by the laser beam 16 is visualized by attaching toner by a developing device (not shown), and the toner on the photosensitive drum 19 is transferred to a sheet 20 by a transfer device (not shown).

A part of the laser light 16 is reflected by a BD mirror 17 and is incident on a BD sensor 18. BD sensor 18
Is a beam detecting device (hereinafter referred to as a BD) that does not show a BD (beam detecting) signal for detecting a printing start position.
(Referred to as a detecting device). BD detection device is BD
A BD detection signal is generated based on the signal. The laser recording device determines a print start position 19a on the photosensitive drum 19 based on the BD detection signal, gives a modulation signal to the laser device 12, and starts forming a one-line latent image from the print start position 19a. . The BD signal from the BD sensor 18 is
The signal is applied to a waveform shaping circuit (not shown), shaped, and sent to a BD detection device. FIG. 7 shows a waveform-shaped BD.
The waveform of the signal (FIG. 7A) and the waveform of the detection signal (BD detection signal) of the BD detection device (FIG. 7B) are shown. Thus, the BD detection device generates (starts up) a BD detection signal based on the BD signal.

The waveform shaping circuit performs waveform shaping at the start of the BD signal from the BD sensor 18 so that the signal sharply falls as indicated by f in the figure. In other words, the time point f of the falling edge of the waveform is the timing for determining the print start position 19a of the laser recording apparatus. Therefore, if the falling edge of the waveform is gentle, the timing at which the BD detection signal is generated tends to be shifted. Because. For example, when the reading sampling time is set to one third of the period of one dot of the laser recording apparatus, if the reading is shifted three times due to the gentle fall of the waveform, the reading is performed by one dot. This is because there is a delay in the line where printing is performed, which is a clear shift in printing.

[0005]

However, in the waveform shaping circuit, at the start of the BD signal from the BD sensor 18, the waveform shaping is performed to sharply lower the signal as shown by f in FIG. At the end, the rising becomes gentle as shown by g in the figure. During the gentle rising, the BD detection device once detects absence (high level) of a BD signal due to fluctuation of a threshold value set inside, and then detects presence of the BD signal again (g). ') A malfunction such as so-called chattering may occur. This may cause a shift of the printing start position by the laser recording device.

In the case of so-called one-time reading in which a BD signal is generated by reading a BD signal once, the BD detection device may be caused by noise from a power supply line or the like in addition to the gentle rising. May occur. On the other hand, in order to prevent the occurrence of the BD detection signal due to such a malfunction, it takes a long time to
A method of reading the D signal many times, for example, five times, is also conceivable. However, if the BD signal cannot be read due to noise or the like during the reading, the reading is started from the beginning, and the timing at which the signal should be generated is reduced. BD after a long delay
It was expected to cause a detection signal.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a laser recording apparatus which can accurately generate a BD detection signal only once in one main scan. Is to do.

[0008]

In order to achieve the above object, a latent image is formed by scanning a photosensitive drum with a laser beam in a main scanning direction, and toner is adhered to the latent image to form a visible image. In the laser recording apparatus of the present invention for transferring an image to a sheet, the laser recording apparatus is disposed at a predetermined position related to the photosensitive drum,
A laser beam detecting device that emits a beam detection signal by detecting the laser beam, Bimudi from the laser beam detecting device
It detects the irradiation of the laser light to the predetermined position based on the start of the detect signal, and a beam detection means for outputting a beam detect detection signal, and mask means for masking the input or output of the beam detector, the first laser beam When setting a mask time shorter than the one cycle corresponding to the scanning period
And a between setting means, said mask means, the output of the beam detect detection signal of the beam detector, Bee
After the start of the detect signal
Masking the input or output of the beam detection means before the end of the signal, and after the end of the beam detect signal
Mask in the course of time set by the mask period setting unit, and cancels the mask of the beam detecting means. In a preferred aspect of the present invention, the beam detecting means detects irradiation of the predetermined position with the laser light by reading a signal from the laser light detecting element a plurality of times, and outputs a beam detect signal. . Moreover,
In the present invention a preferred embodiment, the mask time set by the mask time setting means, the one scanning period 1/10
It is set to the above length.

[0009]

In the laser recording apparatus configured as described above,
At the start of one scan, the laser light detecting element receives the irradiation of the laser light and outputs a beam detect signal. Beam detection means, this beam detection signal based on detecting the irradiation of the laser beam to a predetermined position, and outputs a beam detect detection signals. In response, the mask means beam detect signal
The beam detection means is masked after the start of the signal and before the end of the beam detect signal . And the beam D
A mask shorter than the one cycle corresponding to one scanning period set by the mask time setting means after the end of the tect signal .
Course of disk time, i.e., unmask the beam detecting means before the laser beam to the laser beam detecting device is irradiated at the time of the next scan begins. For this reason, during the period from the irradiation of the laser light to the laser light detecting element at the start of scanning until the irradiation of the laser light to the laser light detecting element at the start of the next scanning .
Since the beam detection means is masked by the mask means during the mask time , no malfunction occurs.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments embodying the present invention will be described below with reference to the drawings. Here, the mechanical configuration of the laser recording apparatus of the present invention is the same as that of the prior art described above with reference to FIG. 6, and therefore, will be described here with reference to FIG. FIG. 1 is a block diagram of a BD detection device 30 of a laser recording device according to a first embodiment of the present invention. The BD detection device 30 generates a BD detection signal for detecting a print start position based on a signal from the BD sensor 18 and generates a BD detection signal.
Send to the 0 side. The controller 40 determines a print start position based on the BD detection signal, supplies a modulation signal to the laser device 12, and starts forming a latent image on the photosensitive drum 19.

[0011] As shown in FIG.
Are a waveform shaping circuit 32 for shaping the waveform of the signal from the BD sensor 18 and a BD detecting circuit 34 for generating a BD detection signal based on the signal from the BD sensor 18 whose waveform has been shaped.
1.86 corresponding to the main scanning time of the laser recording apparatus 1
ms, a clock circuit 36 for generating a clock signal for setting the read cycle 125 ns of the BD detection circuit 34, etc.
And a period setting circuit 37 for setting a mask time of a mask circuit described later, and a mask circuit 38 for masking the input side of the BD detection circuit 34.

Here, the circuit configuration of the BD detection circuit 34, the cycle setting circuit 37, and the mask circuit 38 will be described in more detail with reference to FIG. BD detection circuit 34
Is an AND gate 35 that gates an input from the waveform shaping circuit and a first that latches an output from the AND gate 35.
Flip-flop 34b, second flip-flop 34
c and a third flip-flop 34d. The first flip-flop 34b and the second flip-flop 34
c, a clock signal having a cycle of 125 ns is applied to the third flip-flop 34d. The cycle setting circuit 37 includes a counter 37a and a digital comparator 37b. The counter 37a counts a clock signal having a cycle of 125 ns, and
7b, and the digital comparator 37b outputs
The pulse signal is transmitted from the F terminal by setting 0.186 ms corresponding to 1/10 of 1.86 ms, which is one scanning time. The mask circuit 38 includes a flip-flop 38a.
Latches the input from the D terminal of the third flip-flop 34d of the BD detection circuit 34 and outputs it from the E terminal (inverted output). This latch state is indicated by a pulse signal from the F terminal of the digital comparator 37b. Hold until there is an input.

Next, the operation of the laser recording apparatus according to the present embodiment will be described with reference to FIGS. 1 to 3 and FIG. Here, FIG. 3 shows the waveform of each circuit in one scanning cycle (1.86 ms), and FIG. 3C shows the waveform shaping circuit 3 shown in FIG.
2, (D) is the D terminal output of the third flip-flop 34d of the BD detection circuit 34 shown in FIG. 2, (E) is the E terminal output of the flip-flop 38a of the mask circuit 38, and (F) is 3 shows an output from an F terminal of a digital comparator 37b of the cycle setting circuit 37.

First, the control device 40 rotates the borgon mirror 14 shown in FIG.
The laser light 13 is emitted from 2. Boligon mirror 14
The laser light 16 deflected by the laser beam passes through the lens 15, is reflected by the BD mirror 17, and enters the BD sensor 18. The BD sensor 18 outputs a BD (beam detect) signal to the waveform shaping circuit 32 of the BD detection device 30 shown in FIG. The BD signal from the BD sensor 18 is shaped by the waveform shaping circuit 32 so that the falling j at the time when the BD signal is generated becomes steep as shown in FIG. 34. The signal applied to the BD detection circuit 34 is applied to a first input 35a of the AND gate 35 shown in FIG. Here, as described later, since the high-level output from the flip-flop 38a of the mask circuit 38 is applied to the second input 35b, the BD signal applied to the first input 35a is:
The signal is directly applied to the first flip-flop 34b.
In this state, when a clock signal of 125 ns is applied (indicated by (i) in FIG. 3D), the first flip-flop 34b latches the BD signal and adds it to the second flip-flop 34c. In this state, when the next 125 ns clock signal is applied (shown by (ii) in FIG. 3D)
The second flip-flop 34c latches the BD signal and applies it to the third flip-flop 34d. Further, in this state, when the next clock signal of 125 ns is applied (indicated by (iii) in FIG. 3D), the third flip-flop 34d latches the BD signal and outputs it from the D terminal. This is the BD detection signal j 'shown in FIG. That is, B
The D detection circuit 34 reads the BD signal three times at a timing of 125 ns, and sends the BD detection signal to the control device 40 side when the BD signal is present at all three times (the low level shown in FIG. 3C continues). I do.

The control device 40 is controlled by the BD detection signal.
Recognizes that the laser beam has been irradiated on the BD sensor 18. That is, the laser beam 16 is irradiated to the print start position 19a on the photosensitive drum 19 after a lapse of a predetermined time from the input of the BD detection signal.
Modulates the laser device 12 for printing when the predetermined time has elapsed, and starts forming a one-line latent image from the printing start position 19a.

On the other hand, the output from the D terminal of the third flip-flop 34d is
8a, the flip-flop 38a switches the output from the E terminal (inverted output) to the low side (FIG. 3).
(E)). The output switched to the low side is applied to the second input 35b of the AND gate 35. Since then
The AND gate 35 maintains a low-level output regardless of the presence or absence of an input from the first input 35a. That is, the BD detection circuit 34 is masked by the signal from the mask circuit 38 so that malfunction such as chattering does not occur.

On the other hand, the counter 37a of the cycle setting circuit 37
Counts the clock signal of 125 ns, and adds the counted value to the digital comparator 37b. The digital comparator 37b starts scanning of the laser recording apparatus in the main scanning direction (corresponding to j shown in FIG. 3C).
After 0.186 ms has elapsed (k shown in FIG. 3F), a pulse signal is output from the F terminal (this 0.186 ms corresponds to a scan time of 1.86 ms in the main scanning direction as described above). (Corresponding to 1/10 of 86 ms). When this pulse signal is applied, the flip-flop 3 of the mask circuit 38
8a is cleared, and the output from the E terminal is switched to the high side (see FIG. 3E). The output switched to the high side is applied to the second input 35b of the AND gate 35. Thereafter, when the BD signal is input to the first input 35a, the AND gate 35 outputs the signal to the first flip-flop 34b. That is, the masking of the BD detection circuit 34 by the mask circuit 38 is released.
Thereafter, the BD sensor 18 is irradiated with the laser light at the start of the next main scanning of the laser light, and the above-described operation is repeated.

Next, a second embodiment of the present invention will be described. The circuit operation of the second embodiment is substantially the same as that of the first embodiment. However, in the first embodiment, the BD detection circuit 34 reads the BD signal three times, but in the second embodiment, the BD signal is detected by one reading. Since the configuration of the second embodiment is the same as that of the first embodiment described above with reference to FIG. 1, illustration and description are omitted, and the BD detection circuit 34, the cycle setting circuit 37, and the mask circuit 38 Only the circuit configuration will be described with reference to FIG. The BD detection circuit 34 includes an AND gate 35 that gates an input from the waveform shaping circuit 32, and a first flip-flop 34b that latches an output from the AND gate 35. A clock signal having a cycle of 125 ns is applied to the first flip-flop 34b. Period setting circuit 3
7 is a counter 37a and a digital comparator 37b.
The digital comparator 37b is equivalent to 90% of 1.86 ms, which is one scanning time, at 1.67.
The pulse signal is transmitted from the output terminal by setting 4 ms. The mask circuit 38 includes a flip-flop 38a.
The signal from the output terminal of the first flip-flop 34b of the detection circuit 34 is latched, and this latched state is maintained until a pulse signal is input from the digital comparator 37b.

In the second embodiment, the BD shown in FIG.
When a laser beam is incident on the sensor 18, the BD sensor 18
Outputs the BD signal to the waveform shaping circuit 32 side of the BD detection device 30. This BD signal is shaped by a waveform shaping circuit 32 and then applied to a BD detecting circuit 34. The signal applied to the BD detection circuit 34 is applied to a first input 35a of the AND gate 35 shown in FIG. Here, the second
The flip-flop 3 of the mask circuit 38 is also provided on the input 35b side.
8a, the first input 35
The BD signal applied to a is directly applied to the first flip-flop 34b. In this state, when a clock signal of 125 ns is applied, the first flip-flop 34
b latches the BD signal and outputs it as a BD detection signal. That is, the BD detection circuit 34 reads the BD signal once at a timing of 125 ns and sends the BD signal to the control device 40 side.
Transmitted as a detection signal. The operation of masking and unmasking of the BD detection circuit 34 by the mask circuit 38 of the second embodiment is the same as that of the first embodiment, and a description thereof will be omitted. In the second embodiment, since the BD signal is detected by reading once, there is an advantage that reading is quick.

Next, the configuration of a third embodiment of the present invention will be described with reference to the block diagram of FIG. Here, the same blocks as in the first embodiment described above with reference to FIG. 1 are denoted by the same reference numerals as in the first embodiment, and description thereof is omitted. In the first embodiment described above, the input side of the BD detection circuit 34 is masked by the mask circuit 38. However, in the third embodiment, the output of the BD detection circuit 34 is applied to the gate circuit 138, and the time other than the gate time is set. Are masked. Further, in the above-described first embodiment, the mask time of the mask circuit 38 is set by the cycle setting circuit 37 for collecting clocks. In the third embodiment, however, the gate circuit 138
A stop signal is given from the controller 40 during printing with laser light, and a gate signal is given only when the printing is completed, that is, at the timing when the next scanning is started and the laser light is incident on the BD sensor 18. Is configured. The configuration of the third embodiment can also operate in the same manner as the first and second embodiments.

In the first embodiment, the BD detection circuit 34
Has been described over a 1/10 of the main scanning time by the mask circuit 38, but in the first embodiment,
Since the BD signal is read three times and there is a low possibility that the BD signal is erroneously detected due to noise or the like, if the mask is formed until the completion of the rise of the BD signal shown in FIG. I can stand it. For this reason, about 1/10 of the main scanning time of the mask by the mask circuit 38 is sufficient.
Conversely, in the second embodiment, the BD detection circuit 34
Since the D signal is read once and there is a possibility that the BD signal may be erroneously detected due to noise or the like in addition to the above-described rise time, 9/10 of the main scanning time as set in the second embodiment. It is desirable that the mask be formed over the entire area.

In the first, second, and third embodiments described above, the example in which the masking of the BD detection signal is performed by an electronic circuit has been described. However, the present invention can also be realized by software. .

[0023]

According to the laser recording apparatus of the present invention as EFFECT above description, the irradiation of the laser light to the laser beam detecting element at the scanning start, irradiation of the laser light to the laser beam detecting device during the next scanning start mask time between up, beam detection hand
Since the step is masked by the masking means , only one beam detect signal can be accurately detected during one main scan.

[Brief description of the drawings]

FIG. 1 is a block diagram of a BD detection device according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram illustrating a configuration of the BD detection device in FIG. 1;

FIG. 3 is a waveform diagram of the BD detection device of the first embodiment.

FIG. 4 is a circuit diagram showing a configuration of a BD detection device according to a second embodiment of the present invention.

FIG. 5 is a block diagram illustrating a configuration of a BD detection device according to a third embodiment of the present invention.

FIG. 6 is a perspective view showing a mechanical configuration of a main part of a laser recording apparatus according to a conventional technique and an embodiment.

FIG. 7 is a waveform diagram of a conventional BD detection device.

[Explanation of symbols]

 Reference Signs List 18 BD sensor 19 Photosensitive drum 20 Paper 30 BD detection device 34 BD detection circuit 37 Period setting circuit 38 Mask circuit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B41J 2/44 G02B 26/10 G03G 15/04

Claims (3)

(57) [Claims] 1. A laser recording apparatus that scans a photosensitive drum with a laser beam in a main scanning direction to form a latent image, attaches toner to the latent image to form a visible image, and transfers the image to paper. A laser light detecting element that is disposed at a predetermined position related to the photosensitive drum and detects a laser beam and emits a beam detect signal; and based on the start of the beam detect signal from the laser light detecting element, moves to the predetermined position. A beam detecting means for detecting the irradiation of the laser light, and outputting a beam detection detection signal; a mask means for masking an input or an output of the beam detecting means; and a period corresponding to one scanning period of the laser light. Short ma
And a mask time setting means for setting a disk time, the mask means by the output of the beam detect detection signal of the beam detector, the beam detection signal to open
After the start and before the end of the beam detection signal, the input or output of the beam detection means is masked and the beam detection is performed.
In the course of the mask time set from <br/> the mask time setting means after the detect signal termination, laser recording apparatus characterized by unmask the beam detecting means. 2. The method according to claim 1, wherein the beam detecting unit detects the irradiation of the predetermined position with the laser light by reading a signal from the laser light detecting element a plurality of times, and outputs a beam detect signal. The laser recording device according to claim 1. 3. A mask time set by the mask period setting means, a laser recording apparatus according to claim 1, characterized in that a least one tenth of the length of one scanning period.