JP2003320703A - Imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To correct, for each beam, shading of an imaging apparatus which uses a plurality of laser beams. <P>SOLUTION: In the imaging apparatus which scans a light spot of each of laser beams LD1 and LD2 of a plurality of LDs on a face to be scanned, a period of time A represents a difference of times for the LD1 and LD2 to pass a light detector in a synchronizing detection signal, a period of time B represents a shading correction start point of the LD1, a period of time C represents a shading correction start point of the LD2, and D1-Dx represent scanning position detection intervals. Synchronizing detection signals DETP1 and DETP2 of the LD1 and LD2 have a time difference. Since it is necessary to offset differently from the DETP1 when the LD1 and LD2 are subjected to the shading correction on the basis of the DETP1 of the LD1, a scanning position is detected by equal intervals D1-Dx. Meanwhile, data for correcting a quantity of light of the LD corresponding to the scanning position (#1-#15) is stored beforehand. The quantity of light of each LD corresponding to the detected scanning position in accordance with a timing (DETP1 and DETP2) of a scanning line of each beam is controlled on the basis of the correction data. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a plurality of laser beams as a recording light source and is equipped with a writing optical system for scanning the laser beams, a laser printer, a digital copying machine,
The present invention relates to an image forming apparatus such as a facsimile machine, and particularly to an image forming apparatus having shading correction.

[0002]

2. Description of the Related Art For example, an invention relating to shading correction disclosed in Japanese Patent Laid-Open No. 2000-071510 is
Beam scanning type image formation having a light source means for generating a single light flux, a deflecting means for deflecting and scanning the light flux, and a scanning image forming optical means for converging a light spot on a surface to be scanned and scanning the surface to be scanned. Scanning position of the light spot (image height)
Based on the light quantity correction data stored in the storage means, and a scanning position detecting means for detecting The image forming apparatus is characterized by having control means for controlling the light quantity of the light source corresponding to the scanning position of the light beam according to the timing of the scanning line. Further, the scanning position detecting means therein is a scanning position detecting means having a discrete detection resolution obtained by equally dividing all the scanning positions into an appropriate number, and the storage means stores the light amount correction data for each of the equally divided portions. It is characterized by being a storage means for storing.

[0003]

However, the above-described conventional image forming apparatus is a shading correction method for a single beam, and does not support a plurality of beams. Further, since the scanning position detection and the light amount correction data are also performed by dividing the scanning range of the writing laser at equal intervals, there are cases where the light amount correction that fits the shading characteristics cannot be performed.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an image forming apparatus for performing shading correction of a plurality of writing beams. It is an object of the present invention to provide an image forming apparatus that performs light amount correction that fits shading characteristics.

[0005]

In order to achieve the above object, an image forming apparatus according to the present invention comprises a plurality of light source means for generating a light beam, and a deflecting means for deflecting a plurality of light beams from each light source means. In a beam scanning type image forming apparatus having a scanning image forming optical means for converging a plurality of deflected light beams as light spots on a surface to be scanned and scanning at predetermined scanning timings, the scanning positions of the light spots are arranged at equal intervals. Corresponding to storage means for dividing and storing the light quantity correction data for each divided area, scanning position detecting means for detecting the scanning position of the light spot, and scanning position of the detected light spot in the stored light quantity correction data. Control means for controlling the light quantity of the light source means corresponding to each light flux based on each scanning timing of the plurality of light fluxes by the light quantity correction data.

Further, the image forming apparatus according to the present invention includes a plurality of light source means for generating a light beam, a deflecting means for deflecting a plurality of light beams from the respective light source means, and a plurality of deflected light beams on a surface to be scanned. In a beam scanning type image forming apparatus having a scanning image forming optical means for condensing as a spot and scanning at a predetermined scanning timing, the scanning position of the light spot is divided at equal intervals, and the light amount correction data is obtained for each divided area. Of the plurality of light fluxes, the storage means for storing, the scanning position detecting means for detecting the scanning position of the light spot, and the light amount correction data corresponding to the detected scanning position of the light spot of the stored light amount correction data And a control means for controlling the light quantity of the light source means corresponding to each light flux based on the scanning timing of one light flux.

Further, the image forming apparatus according to the present invention includes a plurality of light source means for generating a light beam, a deflecting means for deflecting a plurality of light beams from the respective light source means, and a plurality of deflected light beams on the surface to be scanned. In a beam scanning type image forming apparatus having scanning and imaging optical means for condensing as spots and scanning at predetermined scanning timings, scanning positions of light spots are divided at arbitrary intervals, and light amount correction is performed for each divided area. The storage means for storing the data, the scanning position detecting means for detecting the scanning position of the light spot, and the light amount correction data corresponding to the detected light spot scanning position in the stored light amount correction data It has a control means for controlling the light quantity of the light source means corresponding to each light flux based on each scanning timing.

Further, the image forming apparatus according to the present invention includes a plurality of light source means for generating a light beam, a deflecting means for deflecting a plurality of light beams from each light source means, and a plurality of deflected light beams on a surface to be scanned. In a beam scanning type image forming apparatus having scanning and imaging optical means for condensing as spots and scanning at predetermined scanning timings, scanning positions of light spots are divided at arbitrary intervals, and light amount correction is performed for each divided area. The storage means for storing the data, the scanning position detecting means for detecting the scanning position of the light spot, and the light amount correction data corresponding to the detected light spot scanning position in the stored light amount correction data The control means controls the light quantity of the light source means corresponding to each light flux based on the scanning timing of one of the light fluxes.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. First, a first embodiment of the invention of claim 1 will be described. The present embodiment is a case where it is applied to an image forming apparatus capable of obtaining an image with double the resolution by superposing laser beams from two LDs and scanning them on a photosensitive drum. Two laser beams (LD1, LD2) obtained from the photodetector in Fig. 1.
Sync detection signal DETP1 of LD1 and sync detection signal DET of LD2 separately obtained from the sync detection signal DETP of
LD modulation level based on shading correction data (LD modulation data) within one cycle of P2 and DETP
An example of the distribution of (LDL VL1, LDLVL2) is shown.

The photodetector, as shown in FIG.
A PIN photodiode 1 for photoelectrically converting light of D (laser diode), and a digital signal conversion circuit 2 for converting its output into an ON / OFF digital signal and outputting the synchronization detection signal DETP are configured. . In addition, a plurality of L
The plurality of light beams (light fluxes) from D are deflected by the deflecting means, then condensed by the scanning image forming optical means as a light spot on the surface to be scanned such as the photosensitive drum, and scanned at predetermined scanning timings. Then, the shading correction is performed by controlling the light amount of the light source by the LD modulation data corresponding to the scanning position of the light spot on each scanning line.

The digital signal conversion circuit 2 outputs a beam detection signal (synchronization detection signal) DETP which becomes low level when receiving the signal from the PIN photodiode 1. From this DETP, DETP1 and DETP2 are created. As described above, an IC in which the light receiving element and the electric circuit are contained in one package may be used, or the light receiving element and the electric circuit may be separated. Alternatively, an optical fiber may be used.

In FIG. 1, the period A is DETP1, DE.
The time difference between the photodetectors passing through LD1 and LD2 in TP2 (time difference between DETP1 and DETP2), and the period B is LD1.
Shading correction start point of the scanning position (image height), period C represents the shading correction start point of the scanning position (image height) of LD2, and D1 to Dx represent scanning position detection intervals. As can be seen from FIG. 1, DETP1 and DETP of LD1 and LD2
The two signals have a time difference A. Therefore, when performing the shading correction of LD1 and LD2 with reference to the synchronization detection signal DETP1 of LD1, it is necessary to apply different offsets from DETP1. The circuits as shown in FIGS. 3 to 5 and 6 are prepared so that the offset of DETP1 can be multiplied by an arbitrary value. 7 shows the state of each signal and the set offset in these circuits. The operation sequence is shown below.

FIG. 3 shows a circuit for producing a reference clock for offset and scanning position. From the clock generation circuit 3 consisting of a crystal oscillator and PLL frequency synthesizer,
The print pixel clock LDCLK is generated. Next, in the clock synchronization circuit 4, the print pixel clock LDCLK is set as the laser beam modulation clock LDCLK1 whose phase is synchronized with the pulse timing of the synchronization detection signal DETP1.

FIG. 4 shows a counter (Cou) of LDCLK1.
nt1) 5 is shown. The counter 5 uses DETP1 as a reset signal and outputs C1. FIG. 5 shows DETP1
2 shows a circuit for setting an offset area from the. L
A comparator (Comp1) 6 in which a set value 1 of the offset of D1 (period B in FIG. 1) is set is used. The count value C1 of the LDCLK1 by the counter 5 is input to the comparator 6, and when the period B becomes the same, the offset pulse OFSET1 is generated from the comparator 6. Then, the offset signal CLR_RC1 is generated through the T flip-flop 7 by the DETP1 and the offset pulse OFSET1, as shown in FIG.

FIG. 6 shows scanning position detection at equal intervals (D1 to D).
x = D), and at the same time, a circuit for transmitting LD modulation data to the LD modulation circuit is shown. Counter (Count
2) 8 is a comparator (Comp which stores the value of the scanning position detection interval D (setting value 2) by counting LDCLK1.
2) The pulse is generated from the comparator 9 every time the count value of the counter 8 is increased by 9 by the scanning position detection interval. This pulse is a counter (Count3) 1
Each time 0 is counted, the modulation data of LD1 (# 0, # 1, ... # 15 in FIG. 1) is read from the ROM 11, converted into an analog signal by the digital-analog converter (DAC) 12, and then the LD modulation of the subsequent stage is performed. Send to the circuit. The LD modulation circuit modulates the light amount of the LD with the analog signal. The counter 8 is reset by the logical product of CLR_RC1 and the output of the comparator 9, and the counter 10 is CL.
It is reset by R_RC1.

In addition, the circuit shown in FIGS.
By providing each pair and replacing DETP1 with DETP2, LDCLK2 and CLR_RC2 for LD2 are obtained. As described above, the circuits of FIGS.
D1 and LD2 are respectively configured and combined, and LD1 and LD2 are provided with respective synchronization detection signals DET.
By multiplying the offset with P1 and DETP2, 2
Shading correction can be applied to the two beams LD1 and LD2 at the same scanning position.

Next, a second embodiment relating to the invention of claim 2 will be described. The present embodiment is a method of performing shading correction on LD1 and LD2 based on DETP1 shown in FIG. In FIG. 8, DETP1 to L
The comparator 6 and the T flip-flop 7 of FIG. 5 in which the offset period B of the shading correction of D1 is set and the comparator (Comp3) 13 and T in which the offset period A + C of the shading correction of DETP1 to LD2 is set as the set value 3 are provided. A T flip-flop 14 similar to the flip-flop 7 is provided. Then, the count value C1 of the counter 5 of FIG. 4 is input to the comparator 13, and the output thereof is input to the T flip-flop 14.

A pulse is generated from the comparator 6 when the counter value C1 becomes the value of the period B, and from the comparator 13 when the counter value C1 becomes the period A + C. By inputting the pulse to the T flip-flops 7 and 14 and setting DETP1 to reset, CLR_RC1 having a low level in the period B and CLR_RC2 having a low level in the period A + C can be formed from the rising edge of DETP1. By incorporating these in place of CLR_RC1 in FIG. 6 and CLR_RC2 configured in FIG. 6 for LD2, DE
LD1 and LD with only one scan timing signal of TP1
Two shadings can be done at the same scan position.

Next, a third aspect of the present invention according to claims 3 and 4,
The fourth embodiment will be described. The present embodiment is a shading correction method that can be performed by dividing the scanning position detection intervals not at equal intervals but at arbitrary intervals. FIG. 9 shows the circuit configuration. In FIG. 9, parts corresponding to those in FIGS. 6 and 8 are designated by the same reference numerals, and overlapping description will be omitted.

In FIG. 9, a comparator (Comp1
1 to Comp1X) 91 to 9X with arbitrary interval values D1 to D
Set x respectively. A counter 8 for counting LDCLK1 is connected to these, and the count value is D1 to
Comparators 91 to 9X each time Dx period is entered
Generate a pulse from. Each time the counter 10 counts the logical sum of these pulses by the OR gate 17, each LD modulation data of LD1 and LD2 is read by the ROM1.
It is read from 1, and transmitted to the LD modulation circuit in the subsequent stage via the digital-analog converter 12. Also, as above, LD
CLK1 is generated by the circuit shown in FIG.

Then, CLR_RC1 and CLR_RC
When the circuit for obtaining 2 is configured as shown in FIG.
It becomes a circuit for performing shading correction of LD1 and LD2 at the scanning timing of the D2 synchronization detection signals DETP1 and DETP2. This circuit is a third embodiment relating to the invention of claim 3.

Also, CLR_RC1 and CLR_RC2
When the circuit for obtaining the above is configured as shown in FIG. 8, it becomes a circuit for performing shading correction of LD1 and LD2 based on the synchronization detection signal DETP1 of LD1. This circuit is the fourth embodiment of the invention of claim 4.

[0023]

As is apparent from the above description, according to the first aspect of the invention, when shading correction of a plurality of light beams is performed, the same scanning position offset is provided from the synchronization detection signal of each light beam. Therefore, the shading correction of all the light fluxes can be performed at the same scanning position.

According to the invention of claim 2, when the shading correction of a plurality of light fluxes is performed, the scanning position offsets of the other light fluxes are separately set from the synchronization detection signal of one light flux. The shading correction of the light flux can be performed at the same scanning position.

According to the third aspect of the invention, when the shading correction of a plurality of light beams is performed, the interval on the scanning line for the correction operation is arbitrarily set, so that the LD modulation correction which is fitted by the shading characteristics can be performed. The same scanning position can be applied to all the light fluxes from the synchronization detection signals of the respective light fluxes.

According to the invention of claim 4, when the shading correction of a plurality of light beams is performed, the interval on the scanning line for the correction operation is arbitrarily set. Therefore, the LD modulation correction fitted by the shading characteristics can be performed. It is possible to perform all the light fluxes at the same scanning position from the synchronization detection signal of one light flux.

[Brief description of drawings]

FIG. 1 is a timing chart showing each synchronization signal, LD modulation data, etc. used in the first to fourth embodiments of the present invention.

FIG. 2 is a block diagram showing a photodetector applied in the first embodiment.

FIG. 3 is a block diagram showing a circuit for creating a reference clock for an offset and a scanning position according to the first embodiment.

FIG. 4 is a block diagram showing a configuration of a laser beam modulation clock counter according to the first embodiment.

FIG. 5 is a block diagram showing a circuit for setting an offset region from a synchronization detection signal of one beam according to the first embodiment.

FIG. 6 is a block diagram showing a circuit for performing scanning position detection at equal intervals and transmitting LD modulation data to an LD modulation circuit according to the first embodiment.

FIG. 7 is a timing chart showing various signals according to the first embodiment.

FIG. 8 is a block diagram showing a circuit for performing shading correction according to the second embodiment.

FIG. 9 is a block diagram showing a circuit for performing shading correction according to the third and fourth embodiments.

[Explanation of symbols]

1 PIN photodiode 2 Digital signal conversion circuit 3 clock generation circuit 4 clock synchronization circuit 5, 8, 10 counter 6, 9, 13, 15, 16 Comparator 7,14 T flip-flop 11 ROM 12 Digital-to-analog converter LD1, LD1 beam LDCK1 Laser beam modulation clock DETP sync detection signal DETP1 LD1 sync detection signal DETP2 LD2 sync detection signal CLR_RC1 LD1 offset signal CLR_RC2 LD2 offset signal

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2C362 AA07 AA12 AA24 AA29 AA33                       AA54 AA65                 2H045 BA22 BA32 CA73 CA88 CA98                       CA99 CB35                 5C072 AA03 BA08 HA02 HA06 HA11                       HB04 HB11 HB13 UA11 XA01                       XA05                 5C074 AA08 BB03 CC26 DD08 DD16                       EE02 EE04 HH02

Claims (4)

[Claims] 1. A plurality of light source means for generating a light flux, a deflecting means for deflecting a plurality of light fluxes from each light source means, and a plurality of deflected light fluxes are condensed as light spots on a surface to be scanned, respectively. In a beam scanning type image forming apparatus having a scanning image forming optical means for scanning at scanning timing, a scanning means for dividing a scanning position of a light spot at equal intervals and a storage means for storing light quantity correction data for each divided area; The scanning position detecting means for detecting the scanning position of each of the plurality of light beams and the light amount correction data corresponding to the detected scanning position of the light spot in the stored light amount correction data correspond to each light beam based on each scanning timing of the plurality of light beams. And a control unit for controlling the light amount of the light source unit. 2. A plurality of light source means for generating a light flux, a deflection means for deflecting a plurality of light fluxes from each light source means, and a plurality of deflected light fluxes are condensed as a light spot on a surface to be scanned,
In a beam scanning type image forming apparatus having scanning and imaging optical means for scanning at predetermined scanning timings, storage means for dividing the scanning position of a light spot at equal intervals and storing light quantity correction data for each divided area A scanning position detecting means for detecting a scanning position of the light spot; and a light amount correction data corresponding to the detected light spot scanning position among the stored light amount correction data, to scan one of the plurality of light beams. An image forming apparatus comprising: a control unit that controls a light amount of a light source unit corresponding to each light flux based on timing. 3. A plurality of light source means for generating a light flux, a deflection means for deflecting a plurality of light fluxes from each light source means, and a plurality of deflected light fluxes are condensed as a light spot on a surface to be scanned,
In a beam scanning type image forming apparatus having a scanning image forming optical unit for scanning at a predetermined scanning timing, the scanning positions of the light spots are divided at arbitrary intervals,
Storage means for storing the light quantity correction data for each divided area, scanning position detecting means for detecting the scanning position of the light spot, and light quantity correction corresponding to the detected light spot scanning position in the stored light quantity correction data An image forming apparatus comprising: a control unit that controls a light amount of a light source unit corresponding to each light flux based on each scanning timing of a plurality of light fluxes based on data. 4. A plurality of light source means for generating a light flux, a deflection means for deflecting a plurality of light fluxes from each light source means, and a plurality of deflected light fluxes are condensed as light spots on a surface to be scanned, respectively. In a beam scanning type image forming apparatus having a scanning imaging optical means for scanning at scanning timing, the scanning positions of the light spots are divided at arbitrary intervals,
Storage means for storing the light quantity correction data for each divided area, scanning position detecting means for detecting the scanning position of the light spot, and light quantity correction corresponding to the detected light spot scanning position in the stored light quantity correction data An image forming apparatus comprising: a control unit that controls a light amount of a light source unit corresponding to each light beam based on a scanning timing of one light beam among a plurality of light beams based on data.