JPH11170597A - Laser beam printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily inspect the interval of laser beam in a sub-scanning direction, in a laser beam printer of an electrophotographic system, by using multi-laser beam. SOLUTION: A test print pattern generating circuit generating a first test print pattern region forming an image by using a pixel consisting of the final laser beam of the pre-scanning surface one before the arbitrary scanning surface of a rotary polyhedral mirror writing multi-laser beam and a photosensitive member and the first laser beam of a present scanning surface and a second test print pattern region forming an image by using two continuous laser beams of the present scanning surface is provided. Test pattern signals are respectively outputted from the first and second NAND gates 306, 406 of this circuit and the interval difference in the sub-scanning direction of laser beam is inspected from this print pattern.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser beam printer using a multi-beam laser, and more particularly to a laser beam printer having a test pattern generating circuit.

[0002]

2. Description of the Related Art In recent years, a multi-beam laser printer for forming an image using a plurality of light beams has been proposed.
FIG. 20 is a diagram showing a configuration example of a laser printer using such a multi-beam laser.

[0003] A laser printer 30 shown in FIG. 20 is connected to an external device 31 such as a computer.
Print on the recording paper based on the control of. External device 3
1 supplies various control signals and image information to the video controller 27 and outputs them as video signals. The print control unit 26 is a control circuit for controlling each unit in the apparatus.

FIG. 21 shows the operation timing of the multi-beam laser printer shown in FIG. Video controller 27
As shown in FIG. 21A, when the RDY signal from the external device 31 becomes TRUE (high level in the figure), the PRINT signal is set to TRUE as shown in FIG. 21B. The print control unit 26 determines that the PRINT signal is TRUE
Then, the drive of the main motor 23 and the polygon motor 14 is started as shown in FIGS.

When the main motor 23 is driven, the photosensitive drum 17, the fixing roller of the fixing unit 9, and the discharge roller 11 start rotating. Thereafter, the print control unit 26
Starts the light quantity control of the semiconductor laser 13 and sequentially drives the primary charger 19, the developing unit 20, and the transfer charger 21 at a high voltage.

When the time T1 has elapsed from the start of driving of the polygon motor 14 and the rotation of the polygon motor 14 is in a steady state, as shown in FIG. ), The paper feed clutch 24 is turned on (ON) to drive the paper feed roller 5, and the recording paper 18 in the paper feed cassette 2 is fed toward the registration roller 6. Then, the VSREQ signal is output to the video controller 17 as shown in FIG. 21 (c) at the timing when the recording paper 18 reaches the registration roller 6, and (h) in FIG.
As described above, the paper feed clutch 24 is turned off and the driving of the paper feed roller 5 is stopped.

On the other hand, when the video controller 27 completes the preparation of the output of the VDO signal after developing the image information from the external device 31 into a dot image, the VSREQ signal in FIG. Is confirmed, the VSYNC signal is changed to T as shown in FIG.
RUE. Then, in synchronization with this, (e) of FIG.
After the time Tv, the output of the VDO signal as the image data for one page is started.

At this time, the print control unit 26
As shown in (i), the registration roller clutch 25 is turned on and the registration roller 6 is driven after the time T3 from the rise of the VSYNC signal. The driving of the registration roller 6 is performed for a time T4 until the rear end of the recording paper 18 passes through the registration roller 6 as shown in FIG. Also,
During this time, the print control unit 26 controls the video controller 27
The semiconductor laser 13 is driven according to the VDO signal from the semiconductor laser 13.

Two semiconductor lasers 13 are provided,
The print controller 26 drives each semiconductor laser according to the VDO signal, and the laser light emitted from the two semiconductor lasers is converted into a linear scan by the rotation of the polygon mirror 15 of the scanner unit 7. The laser light of the two semiconductor lasers is applied to the photosensitive drum 1 by the mirror 16.
7 is irradiated.

In this manner, two lines of laser light, each modulated in accordance with the VDO signal, are simultaneously scanned on the photosensitive drum 17 to form a two-line latent image on the photosensitive drum 17, and the same operation is performed thereafter. Are repeated to form a latent image for one page on the photosensitive drum 17.

The latent image formed on the photosensitive drum 17 is
The toner is transferred to the recording paper 18 by the transfer charger 21 after being developed by the developing device 20. When the transfer is completed, the recording paper 18 is conveyed to the fixing device 9 where the toner image is fixed, and then discharged outside the apparatus by the discharge roller 11. If you want to continue printing the next page,
The print control unit 26 operates at time T5 as shown in FIG.
Later, the PRINT signal is set to TRUE again, and the same control as that for printing the first page is performed.

A test pattern generating circuit of such a multi-beam printer is configured, for example, as shown in FIG. FIG. 22 given as an example shows a circuit for generating a vertical line test print pattern by a two-beam laser printer.

The configuration and operation of the circuit shown in FIG. 22 will be described below. The mask signal generation timing setting register 101 shown in FIG. 22 stores a / MASK1 signal 1 required for test printing.
This register stores the timing (= counter value) for releasing the H.24 and / MASK2 signal 224 and the timing of occurrence (= counter value). The storage in the register 101 is performed at the beginning of the test print. Thereafter, test printing is performed according to the operation timing chart of the test print generation circuit of FIG.

Here, the / BD1 signal 120 is supplied to the first phase-locked oscillator 10 in order to align the horizontal synchronization of the test print.
2 and the first main scanning counter 103. Then, as shown in FIG. 23 (a), the / BD1 signal 120 is T
When it becomes RUE, first, the first main scanning counter 103 is reset. Subsequently, the first phase locked oscillator 102
As shown in FIG. 3B, an image clock signal (CLK1 signal) 121 synchronized with the / BD1 signal 120 is generated. This CLK1 signal 121 is output from the first main scanning counter 1
03 and a counter 10 for generating a test pattern
6 is input.

The first main scanning counter 103 counts the first main scanning counter value 122 to measure the number of clock pulses.
Increases with time. The main scanning counter value 122
Is compared with a counter value for canceling the mask set in the mask signal timing setting register 101 by the comparator 104. On the other hand, at this time, the value of the counter 106 remains 0. This is the / write inhibit signal 12
This is because the counter 106 continues to be cleared because 6 is TRUE.

As shown in FIG. 23 (f), the / BD1 signal 1
Following / 20, the / BD2 signal 220 changes from FALSE to TR.
When it comes to the UE, the first main scanning counter 103 described above
Similarly, the second main scanning counter 203 is reset, and FIG.
The second phase-locked oscillator 202 generates the second image clock pulse signal (CLK2 signal) 221 as shown in FIG. Then, the second main scanning counter 203 measures the number of clock pulses. In the second comparator, the mask release value of the laser 2 and the second main scanning counter value 22
2 are compared. As a result, the second main scanning counter value 22
2 is smaller, / MASK2 signal 224 is TRUE
Remains.

When the first main scanning counter value 122 becomes a mask release value and the mask of the laser 1 is released as shown in FIG. 23C, the / MASK1 signal becomes the NAND gate 1
05 is input.

At this time, / TO is applied to NAND gate 105.
When the PE signal 125 FALSE is input, FIG.
The counter 106 starts counting as shown in FIG.
Then, the NAND gate 107 having each bit of the 4-bit counter 106 as an input value is set to / TEST P
An ATTERN1 signal 127 is generated. (E) of FIG.
/ TEST P when the first counter value = Fh as in
The ATTERN1 signal 127 becomes TRUE.

When the value of the second main scanning counter 222 also reaches the value of the mask release, the / TEST PAT goes through a similar process.
Generate the TERN2 signal 227.

When the first main scanning counter value 122 becomes a value at which a mask is generated, the / TESTPATTERN1 signal 127 becomes FALSE. Similarly, a mask is generated on the laser 2 and writing is prohibited. This series of main scanning is repeated until the / TOPE signal 125 becomes TRUE.

In this manner, a vertical line test pattern is printed.

[0022]

However, in the above-described multi-beam laser printer, the distance between the plurality of lasers in the sub-scanning direction is adjusted when a single scanner unit is manufactured. Therefore, there is a problem that a special tool for measuring the interval between the beams is required in order to confirm the interval between the beams in the sub-scanning direction after the beam is attached to the main body.

As a method of inspecting a finished product, there is a test print. An item which can be inspected from a vertical line test print pattern created by a print pattern generating circuit of a conventionally proposed multi-beam laser printer is printing. Were possible, the degree of skew, the degree of jitter of the scanner motor, and the degree of confirmation of the mask area.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has a laser beam having a test print pattern generating circuit for generating a test print pattern capable of easily inspecting the interval between laser beams in the sub-scanning direction. It is intended to provide a printer.

[0025]

A laser beam printer according to the present invention is constructed as follows.

(1) In a laser beam printer for forming an image by scanning a plurality of laser beams modulated by an image signal on a photoreceptor via a rotary polygon mirror, a laser beam printer immediately before an arbitrary scanning surface of the rotary polygon mirror is used. A first test print pattern area for forming an image using pixels consisting of the last laser beam on the previous scan plane and the first laser beam on the current scan plane, and two consecutive laser beams on the current scan plane A test print pattern generating means for generating a second test print pattern area for forming an image using pixels is provided.

(2) In the above configuration (1), the first test print pattern and the second test print pattern are horizontal lines.

(3) In the above configuration (1), the first test print pattern and the second test print pattern are halftone images.

[0029]

Embodiments of the present invention will be described below with reference to the drawings. The outline of the laser beam printer is the same as that in FIG. 20, and the description is omitted.

(Embodiment 1) FIG. 1 is a block diagram showing a configuration of a test print pattern generation circuit in a two-beam laser printer of this embodiment. Hereinafter, the configuration and operation of the circuit of FIG. 1 will be described.

Mask signal generation timing setting register 3
01 is the / MASK1 signal 32 required for test printing
4 and the timing for releasing the / MASK2 signal 424 (=
Counter value) and timing of occurrence (= counter value)
And the timing of generating the TOGGLE signal 326 (=
(A counter value). The storing in the register 301 is performed at the beginning of the test print.
Thereafter, test printing is performed according to the operation timing chart of the test print pattern generation circuit shown in FIG.

The / BD1 signal 320 is input to the first phase locked oscillator 302 and the first main scanning counter 303. Then, as shown in FIG. 2A, the / BD1 signal 320 is TR
When it becomes UE, the first main scanning counter 303 is reset. Further, triggered by the / BD1 signal 320 being TRUE, the first phase-locked oscillator 302
The first image clock signal (CLK
1) 321 is started.

First image clock signal (CLK1 signal) 3
21 is input to the first main scanning counter 303. The first main scanning counter 303 measures the pulse of CLK1. The first main scanning counter value 322 is compared by the first comparator 304 with the value set in the mask signal timing setting register 301. As a result of the comparison, the / mask 1 signal (/ MASK1 signal) 324 is
As shown in (c) of FIG.
Output to ND gate 306.

In this way, the signal for inhibiting the writing of the beam 1 in the main scanning direction is controlled. The first comparator 304 compares the first main scanning counter 303 with the mask signal generation timing setting register 301, and as a result, the TOGGLE signal 326 as shown in FIG.
To the T-flip-flop 305.

In addition, the control of write inhibition in the vertical direction is performed as follows.
From the print control unit 26 / top erase signal (/ TO
(PE signal) 325. This / TOPE signal 325 is input to the / CLR signal input terminal of the first T-flip-flop 305 that generates test print data. In this way, the writing of the beam 1 in the sub-scanning direction is prohibited. / TOPE in Fig. 1
Signal 325 is FALSE.

When the / TOPE signal 325 is FALSE, the first T-flip prop 305 outputs a signal 327 which is a source of the test pattern 1 signal in accordance with the TOGGEL signal 326. The signal 327 which is the source of the test print pattern 1 signal is supplied to the first NAND gate 306.
Is masked by the / MASK1 signal 324. In this manner, the / TEST PATTERN1 signal 328 is output from the first NAND gate 306.

On the other hand, the / BD2 signal 420 is output from the second phase-locked oscillator 402, the second main scanning counter 403, and the second T-
The signal is input to the flip-flop 405. As shown in FIG. 2B, following the / BD1 signal 320, the / BD2 signal 42
When 0 changes from FALSE to TRUE, the second main scanning counter 403 is reset. Also, the / BD2 signal 20
Becomes TRUE, the second T-flip-flop 405
The logic of the signal 427, which is the basis of the test print pattern output from, is inverted.

Further, triggered by the / BD2 signal 420 being TRUE, the second phase-locked oscillator 402
Starts generation of the second image clock signal (CLK2 signal) 421 synchronized with the / BD signal 420. The second image clock signal (CLK2 signal) 421 is input to the second main scanning counter 403, and the second main scanning counter 403
Measures the pulse of the CLK2 signal 421.

The second main scanning counter value 422 is compared by the second comparator 404 with the value set in the mask signal timing setting register 301. As a result of the comparison, the / mask 2 signal (/ MASK2 signal) 424 is
As shown in (d) of FIG.
Output to ND gate 406. As a result, / MASK
The two signal 424 is a signal delayed by a certain time from the / MASK1 signal 324. The amount of this delay time is / B
After the D1 signal 320 becomes TRUE, the / BD2 signal 4
Time until 20 becomes TRUE.

Also, a / top erase signal (/ TOPE
Signal) 325 is the / T signal of the second T-flip-flop 405.
It is also input to the CLR signal input terminal. In this way,
Writing is prohibited in the sub-scanning direction.

When the / TOPE signal 325 is FALSE, the second T-flip-flop 405 operates every other scan.
An RUE signal 427 is output to the second NAND gate 406. The signal 427 which becomes TRUE every other scan
Is the / MASK2 signal 4 at the second NAND gate 406
24 masks it. In this way, the second
From the NAND gate 406, / TE as shown in FIG.
An ST PATTERN2 signal 428 is output.

FIG. 3 is a view showing a test print pattern result (normal case) printed when a test print is executed by the multi-beam laser printer having the test print pattern generating circuit of the present embodiment.

The left half surface 51 of the test print pattern shown in FIG. 3 is composed of a horizontal line scanned by the beam 2 on the scanning surface immediately before the scanning surface of the rotary polygon mirror and a horizontal surface scanned by the beam 1 on the scanning surface. This is a horizontal line of 2 dots and 2 spaces by the space of the line. The right half surface 52 of the test print pattern is a horizontal surface of 2 dots and 2 spaces formed by a horizontal line scanned by the beam 1 and the beam 2 on the scanning surface and a space of 2 lines.

At this time, the laser interval in the sub-scanning direction is as shown in FIG.
Indicated by FIG. 4 shows the light spot irradiated on the photosensitive drum surface by the beam 1 and the beam 2 for two scans.

The light spot 53 is a light spot by the laser 1 in the first scanning. The light spot 54 is a light spot of the first scanning laser 2. The light spot 55 is a light spot by the laser 1 in the second scanning. Light spot 56
Is a light spot by the laser 2 in the second scanning. The interval 57 is the interval between the beams 1 and 2 irradiated on the same scanning surface in the sub-scanning direction. Then, the right half surface 52 of the test print result shown in FIG. 3 is a result of writing two lines and two spaces with two beams at an interval 57.

The interval 58 is the interval between the preceding scanning beam 2 of two successive scans and the subsequent scanning beam 1 in the sub-scanning direction. The left half surface 51 of the test print result shown in FIG. 3 is a result of writing two lines and two spaces with two beams at an interval 58. In a normal state, the intervals 57 and 58 are equal. Therefore, the same pattern is drawn on the left half 51 and the right half 52 of the test print result.

Next, a case where the interval between the two-beam lasers in the sub-scanning direction is wider than a specified value will be described. FIG. 5 is a diagram showing the beam interval when the interval in the sub-scanning direction of the two-beam laser is wider than a specified value. Similarly to FIG.
Some are shown for scanning.

The light spot 59 is a light spot of the first scanning laser 1. The light spot 60 is a light spot of the first scanning laser 2. The light spot 61 is a light spot by the laser 1 in the second scanning. Light spot 62
Is a light spot by the laser 2 in the second scanning. Also,
The interval 63 is between the beam 1 and the beam 2 irradiated on the same scanning plane.
In the sub-scanning direction. Then, as assumed, the interval 63 is wider than the specified interval. The interval 64 is two consecutive
This is the distance in the sub-scanning direction between the scanning beam 2 before scanning and the scanning beam 1 after scanning.

At this time, the interval 64 becomes narrower than the specified interval. Therefore, the test print result when the interval between the two-beam lasers in the sub-scanning direction is wide is as shown in FIG. On the left half surface 65 of the test print result shown in FIG. 6, the width of the two beams is narrower and the space between the two spaces is printed wider than in the normal state. In addition, the right half surface 66 of the test print result has a wider interval between the two beams compared to the normal state,
The space spacing is reduced. As a result of the increase in the interval between the two beams, the two beams may become thick or separate into two beams.

Therefore, when the interval in the sub-scanning direction of the two-beam laser is wider than the specified value, the density of the horizontal line of two dots and two spaces on the left half surface 65 and the right half surface 66 in the test print result of FIG. Occurs. With such a mechanism,
It is possible to determine a case where the interval between the two-beam lasers in the sub-scanning direction is wide.

Similarly, the case where the interval between the two-beam lasers in the sub-scanning direction is narrower than a prescribed value can be explained.
FIG. 7 is a diagram showing the beam interval when the interval of the two-beam laser in the sub-scanning direction is smaller than a prescribed value. As in FIG. It is shown in minutes.

The light spot 67 is a light spot of the first scanning laser 1. The light spot 68 is a light spot by the laser 2 in the first scanning. The light spot 69 is a light spot of the second scanning laser 1. Light spot 70
Is a light spot by the second scanning laser 2. The interval 71 is an interval between the beams 1 and 2 irradiated on the same scanning surface in the sub-scanning direction. Then, as assumed, the interval 71 is narrower than the specified interval. The interval 72 is the interval in the sub-scanning direction between the beam 2 of the preceding scan and the beam 1 of the subsequent scan in two successive scans.

At this time, the interval 72 is wider than the specified interval. Therefore, the test print result when the interval between the two-beam lasers in the sub-scanning direction is narrow is as shown in FIG. Left half 73 of the test print result of FIG. 8 (FIG. 8)
Is printed with a wider interval between two beams than in a normal state and a narrow interval between two spaces. As described above, as a result of the increase in the interval between the two beams, the two beams may become thick or separate into two beams. In the right half surface 74 of the test print result, the interval between the two beams is smaller than in the normal state,
The spacing between the spaces is increased.

Therefore, when the interval between the two-beam lasers in the sub-scanning direction is smaller than the specified value, the density of the horizontal line of two dots and two spaces on the left half 73 and the right half 74 of the test print results. With such a structure, it is possible to determine a case where the interval between the two-beam lasers in the sub-scanning direction is narrow.

As described above, in the first embodiment, 2
The fact that the interval in the sub-scanning direction of the beam laser is a prescribed value can be easily determined by test printing using two types of horizontal lines of two dots and two spaces.

Although the present embodiment has been described by taking as an example the case where two areas are provided on one side of one sheet for printing, the present invention is limited to printing on one side of one sheet. It is not something to be done. For example, printing is performed by providing an area of the first pattern on the first sheet and an area of the second pattern on the second sheet.
It is possible to print the area of the pattern and the area of the second pattern on the back side of the sheet.

(Embodiment 2) FIG. 9 is a block diagram showing a configuration of a test print pattern generation circuit for realizing Embodiment 2 in a two-beam laser printer. Hereinafter, the configuration and operation of the circuit of FIG. 9 will be described.

Mask signal generation timing setting register 5
01 is a / MASK1 signal 52 required for test printing.
4 and the timing for releasing the / MASK2 signal 624 (=
Counter value) and timing of occurrence (= counter value)
Is a register for storing. The storage in the register 501 is performed at the beginning of the test print. After that Figure 1
Test printing is performed according to the operation timing chart of the test print pattern generation circuit shown in FIG.

/ Top erase signal (/ TOPE signal)
Reference numeral 525 denotes D-flip-flops 505 to 507 for generating test print patterns, and / CL of 605 to 607.
The signal is input to the R signal input terminal. As shown in FIG. 10A, when the / TOPE signal 525 switches from TRUE to FALSE, the write inhibition in the sub-scanning direction is released.

On the other hand, the / BD1 signal 520 is input to the first phase-locked oscillator 502, the first main scanning counter 503, and the first T-flip-flop 507. Then, when the / BD1 signal 520 becomes TRUE as shown in FIG. 10B, the first main scanning counter 503 is reset. When the / BD1 signal 520 becomes TRUE, the first T-
The output signal 529 of the flip-flop 507 is FALSE
To TRUE or TRUE to FALSE. The output signal 529 of the first T-flip-flop 507 is input to the first NAND gate 508.

Further, triggered by the / BD1 signal 520 being TRUE, the first phase-locked oscillator 502
Starts generation of a first image clock signal (CLK1 signal) 521 synchronized with the / BD1 signal 520. The first image clock signal (CLK1 signal) 521 includes a first main scanning counter 503, an 11th D-flip-flop 507,
The signals are input to the twelfth D-flip-flop 508, respectively. The first main scanning counter 503 outputs the CLK1 signal 521
The pulse of is measured. The first main scanning counter value 522 is:
The first comparator 504 compares the value with the value set in the mask signal timing setting register 501. As a result of the comparison, the / mask 1 signal (/ MASK1 signal) 524 is supplied from the first comparator 504 to the / CLR signal input terminal of the eleventh-D flip-flop 507 and the twelfth D-flip-flop 508 as shown in FIG. Is input to
In this way, the control for inhibiting the writing of the beam 1 in the main scanning direction is performed.

The 11D flip-flop (DF)
F) 507 and twelfth flip-flop (D-FF) 5
08 is connected as follows. The Q output terminal of the eleventh D-FF 507 is the D input terminal of the twelfth D-FF 508, and the / Q output terminal of the twelfth D-FF 508 is the eleventh D-FF5.
007, and the Q output terminal of the twelfth FF 508 are connected to the input terminal of the first NAND gate 509, respectively. With this connection, the signal is switched from FALSE, FALSE, TRUE, TRUE, and first according to the signal 528 output to the NAND gate 509 and the CLK1 signal.

The signal 52 in the main scanning direction of the laser 1
8 and the signal 529 in the sub-scanning direction are
8 and the / TEST PATTERN1 signal 5
30 is output.

Similarly to the laser 1, at the timing when the / BD2 signal 620 becomes TRUE as shown in FIG.
A CLK2 signal 621 is generated. This CLK2 signal 62
1, a / MASK2 signal 624 and a signal 628 in the main scanning direction of the laser 2 are generated as shown in FIG.

The difference between the test pattern generation circuit of the laser 2 and the test pattern generation circuit of the laser 1 lies in the signal circuit section in the sub-scanning direction. That is, the / BD2 signal 620
And / CHG signal 631 are input to AND gate 609. The output signal 632 of the AND gate 609 is input to a second T-flip-flop (second T-FF),
Is output in the sub-scanning direction.

The signal 62 in the main scanning direction of the laser 2
8 and the signal 629 in the sub-scanning direction are
8 and the / TEST PATTERN2 signal 6
30 is output.

When the / CHG signal 631 becomes TRUE, the writing cycle of the laser in the sub-scanning direction is reversed.
In this embodiment, the / CHG signal 631 is input in the form of a pulse signal in the middle of the sheet.

When a test print is executed by the test print pattern generation circuit having the above configuration, two types of 2 × 2 halftone dot patterns shown in FIG. 11 are obtained. The first halftone dot 80 is composed of the beam 1 at the upper part and the beam 2 at the lower part. The second halftone dot 81 has a beam 2 at the top,
The lower part is constituted by the beam 1. FIG. 11 shows a test print for confirming the interval of the two-beam laser beam in the sub-scanning direction.

FIG. 12 shows a halftone dot pattern when the interval between the two-beam lasers in the sub-scanning direction is wide.
In FIG. 12, the first halftone dot 82 is vertically long. Also, 1
In the second halftone dot area, the interval between halftone dots adjacent in the sub-scanning direction is narrower than in the normal case. The second halftone dot 83 is printed as a halftone dot shrunk in the vertical direction, and the interval between halftone dots adjacent in the sub-scanning direction in the second halftone dot area is wider than in the normal case. Therefore, it can be seen that the density of the area of the first halftone dot is different from the density of the area of the second halftone dot, and the interval between the two-beam lasers in the sub-scanning direction is easily wide.

FIG. 13 shows a halftone dot pattern when the interval between the two-beam lasers in the sub-scanning direction is narrow.
In FIG. 13, the first halftone dot 84 is printed as a halftone dot shrunk in the vertical direction. In the first halftone dot area, the interval between halftone dots adjacent in the sub-scanning direction is wider than in the normal case.
The second halftone dot 85 is vertically elongated, and the interval between halftone dots adjacent in the sub-scanning direction in the second halftone dot area is smaller than that in the normal state. Therefore, it can be seen that the density of the first halftone dot region is different from the density of the second halftone dot region, and the interval between the two-beam lasers in the sub-scanning direction is easily narrow.

As described above, in the second embodiment, the fact that the interval between the two-beam lasers in the sub-scanning direction is a specified value can be easily determined by test printing using two types of 2 × 2 halftone dots. Can be determined.

(Embodiment 3) In Embodiment 3 of the present invention, a method for confirming the interval between laser beams in the sub-scanning direction in a multi-beam laser printer having three or more laser beams will be described. FIGS. 14, 15 and 16 show test print results of a multi-beam laser printer using a three-beam laser.

FIG. 14 shows a test print result when the interval between the three beams in the sub-scanning direction is a prescribed value. FIG.
Is composed of two halftone dot pattern areas, and the size of one halftone dot in each case is 2 dots × 2 dots. In both cases, the interval between the halftone dots is 2 dots in the scanning direction and 4 dots in the sub-scanning direction. However, the interval between halftone dots is not limited to the above value.

One of the two halftone dots is a halftone dot 86. The upper half of this halftone dot 86 is written with beam 1,
The lower half is written with beam 2. The halftone dot 86 is characterized by being written by one scan.

Another dot is a dot 87. The upper half of this halftone dot 87 is written in beam 3 and the lower half is beam 1
Written in The halftone dot 87 is characterized in that it is written by the preceding scan and the subsequent scan of two consecutive scans. When the beam interval in the sub-scanning direction is a specified value, it is inferred from the test print result shown in FIG. 14 that the densities of the two types of halftone dots are the same.

FIG. 15 is a diagram showing a test print result when the interval between the three beams in the sub-scanning direction is wider than that after the regulation. Hereinafter, a description will be given in comparison with the test print result at the specified interval in FIG.

The dot 88 written by the beam 1 and the beam 2 is a long point in the sub-scanning direction. The interval between the halftone dots 88 is the same as the interval of 2 dots in the main scanning direction, and the interval in the sub-scanning direction is shorter than 4 dots.

The halftone dot 89 written by the other beam 3 and beam 1 is a point contracted in the sub-scanning direction. Also,
Regarding the interval between the halftone dots 89, the interval in the main scanning direction remains the same at 2 dots, and is longer than the interval of 4 dots in the sub-scanning direction. Therefore, when the beam interval in the sub-scanning direction is wider than the prescribed value, a test print pattern having a difference in density between the two types of halftone dots is printed.

FIG. 16 is a diagram showing a test print result when the interval between the three beams in the sub-scanning direction is smaller than a specified value. Hereinafter, a description will be made in comparison with the test print result at the specified interval in FIG.

The dot 90 written by the beam 1 and the beam 2 is a short point in the sub-scanning direction. As for the interval between the halftone dots 90, the interval in the main scanning direction remains the same at 2 dots, and the interval in the sub-scanning direction is longer than 4 dots.

The halftone dot 91 written by the other beam 3 and beam 1 is a point contracted in the sub-scanning direction. Also,
Regarding the interval between the halftone dots 91, the interval in the main scanning direction remains the same at 2 dots, and the interval in the sub-scanning direction is shorter than 4 dots. Therefore, when the beam interval in the sub-scanning direction is smaller than the prescribed value, a test print pattern having a difference in density between the two types of halftone dots is printed.

As described above, the fact that the interval between the three-beam lasers in the sub-scanning direction is a specified value is determined by two types of 2 ×
It can be easily determined by a test print using the second halftone dot.

Further, a test print pattern for confirming the interval of the four beams in the sub-scanning direction in the multi-beam laser printer of this embodiment using the four-beam laser will be described. FIGS. 17, 18 and 19 show test print results of a multi-beam laser printer using a four-beam laser.

FIG. 17 shows a test print result when the interval between the four beams in the sub-scanning direction is a prescribed value. As in FIG. 14, the test print pattern shown in FIG. 17 is composed of two dot pattern areas, and in each case, the size of one dot is 2 dots × 2 dots. In both cases, the interval between the halftone dots is 2 dots in the scanning direction and 2 dots in the sub-scanning direction. However, the interval between halftone dots is not limited to the above value.

One of the two halftone dots is a halftone dot 92. The upper half of this halftone dot 92 is written with beam 1 and the lower half is written with beam 2. The halftone dot 92 is characterized by being written by one scan.

Another halftone dot is a halftone dot 93. The upper half of this dot 93 is written with beam 4 and the lower half is beam 1
Written in The halftone dot 93 is characterized by being written by two consecutive scans and a subsequent scan.

FIG. 18 is a diagram showing test print results when the interval between the four beams in the sub-scanning direction is wider than a specified value. FIG. 19 is a diagram showing test print results when the interval between the four beams in the sub-scanning direction is smaller than a specified value.

When the beam interval in the sub-scanning direction is a prescribed value, it can be inferred from the test print result shown in FIG. 17 that the densities of the two types of halftone dots are the same. Also,
When the beam interval in the sub-scanning direction is smaller than the prescribed value, it is inferred from the test print result diagram shown in FIG. 18 that the densities of the two types of halftone dots are different. Similarly, when the beam interval in the sub-scanning direction is narrower than the specified value, it can be inferred from the test print results shown in FIG. 19 that the densities of the two types of halftone dots are different.

Similarly, in a multi-beam laser printer using an n-beam laser, a test print pattern for confirming the interval in the sub-scanning direction of the n-beam can be realized, for example, as follows. A halftone dot pattern in which 2 dots × 2 dots are written using beam 1 and beam 2 in one scan, and a halftone dot pattern in which 2 dots × 2 dots are written using beam n and beam 1 in continuous scanning Construct a test print pattern.

As described above, in the n-beam laser printer, it is possible to confirm the interval between the laser beams in the sub-scanning direction.

The embodiments of the present invention have been described above. In the present invention, as described above, a plurality of laser beams modulated by an image signal are scanned on a photosensitive drum using a rotating polygon mirror to form an image. In a laser beam printer, n (n ≧ 2) laser beams scanned at one time on any one surface of a rotary polygon mirror are converted into B1, B2,. And when
A first test print pattern area for forming an image using a pixel consisting of the beam Bn and the beam B1 of the current scanning plane one before the current scanning plane of the rotary polygon mirror; And a test print pattern generating means for generating a second test print pattern area for forming an image by using pixels consisting of the beam Bm-1 of the scanning surface and the beam Bm of the scanning surface (m is an integer of n or less). It was made.

The difference between the intervals in the sub-scanning direction can be obtained as the density difference between the first test print pattern area and the second test print pattern area.

[0093]

As described above, according to the present invention,
The interval in the sub-scanning direction of the laser beam, which is unique to the multi-beam laser printer, can be checked at low cost by using a special test print pattern and a test print pattern generating circuit without using an external device.

Further, the interval in the sub-scanning direction can be confirmed as a result of a final step of a laser beam printer called a test print.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a test print pattern generation according to a first embodiment.

FIG. 2 is a time chart showing an operation of the test pattern print pattern generation circuit of FIG. 1;

FIG. 3 is a diagram showing a test print result (in a normal state) of the two-beam laser printer according to the first embodiment.

FIG. 4 is a diagram showing a beam spot for two scans in a two-beam laser printer (in a normal state).

FIG. 5 is a diagram showing a beam spot for two scans (when the beam interval is wide) in a two-beam laser printer.

FIG. 6 is a diagram illustrating a test print result (when the beam interval is wide) of the two-beam laser printer according to the first embodiment.

FIG. 7 is a diagram showing a beam spot for two scans (when the beam interval is narrow) in a two-beam laser printer.

FIG. 8 is a diagram showing a test print result (when the beam interval is narrow) of the two-beam laser printer of the first embodiment.

FIG. 9 is a block diagram illustrating a configuration of a test pattern print pattern generation circuit according to a second embodiment.

FIG. 10 is a time chart showing the operation of the test print pattern generation circuit of FIG. 9;

FIG. 11 is a diagram illustrating a test print result (in a normal state) of the two-beam laser printer according to the second embodiment.

FIG. 12 is a diagram illustrating a test print result (when the beam interval is wide) of the two-beam laser printer according to the second embodiment.

FIG. 13 is a diagram illustrating a test print result (when the beam interval is small) of the two-beam laser printer according to the second embodiment.

FIG. 14 is a diagram illustrating a test print result (in a normal state) of the two-beam laser printer according to the third embodiment.

FIG. 15 is a diagram illustrating a test print result (when the beam interval is wide) of the two-beam laser printer according to the third embodiment.

FIG. 16 is a diagram illustrating a test print result (when the beam interval is narrow) of the two-beam laser printer according to the third embodiment.

FIG. 17 is a diagram illustrating a test print result (in a normal state) of the two-beam laser printer according to the fourth embodiment.

FIG. 18 is a diagram illustrating a test print result (when the beam interval is wide) of the two-beam laser printer according to the fourth embodiment.

FIG. 19 is a diagram illustrating a test print result (when the beam interval is small) of the two-beam laser printer according to the fourth embodiment.

FIG. 20 illustrates a configuration example of a multi-beam laser printer.

FIG. 21 is a time chart showing the operation of the multi-beam laser printer shown in FIG. 20;

FIG. 22 is a block diagram showing a configuration of a test print pattern generation circuit of a conventional multi-beam laser printer.

FIG. 23 is a time chart showing the operation of the test print pattern generation circuit of FIG. 22;

[Explanation of symbols]

 301 Mask signal generation timing generation circuit 302 First phase locked oscillator 303 First main scanning counter 304 First comparator 402 Second phase locked oscillator 403 Second main scanning counter 404 Second comparator 501 Mask signal generation timing generation circuit 502 First phase Synchronous oscillator 503 First main scanning counter 504 First comparator 602 Second phase locked oscillator 603 Second main scanning counter 604 Second comparator

Claims (3)

[Claims] 1. A laser beam printer which forms an image by scanning a plurality of laser beams modulated by an image signal on a photosensitive member via a rotary polygon mirror, wherein the laser beam printer is located immediately before an arbitrary scanning surface of the rotary polygon mirror. A first test print pattern area for forming an image using pixels consisting of the last laser beam of the previous scanning plane and the first laser beam of the current scanning plane, and pixels consisting of two consecutive laser beams of the current scanning plane A laser beam printer having test print pattern generating means for generating a second test print pattern area for forming an image by using the method. 2. A first test print pattern and a second test print pattern.
2. The laser beam printer according to claim 1, wherein the test print pattern is a horizontal line. 3. A first test print pattern and a second test print pattern.
2. The laser beam printer according to claim 1, wherein the test print pattern is a halftone image.