JP3124051B2 - Image 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 an image recording apparatus, such as a laser printer or a digital copying machine, having one photoconductor and one transfer drum and capable of obtaining recorded images of a plurality of colors.

[0002]

2. Description of the Related Art Conventionally, as this type of image recording apparatus,
For example, there is one disclosed in JP-A-57-19764. In this method, writing is performed a plurality of times during one rotation of the photoconductor, but the diameter of the drum becomes large. Also, control is performed so that writing is performed by opening the gate at the time from the encoder pulse. Therefore, the condition is that the encoder (that is, the main body system) and the optical writing system are synchronized.

On the other hand, there is an apparatus in which a main body system and an optical writing system are operated asynchronously. That is, the writing timing by the optical writing system is controlled based on the position signal from the photoconductor.

[0004]

However, in such an asynchronous operation, depending on the writing state after the photoconductor position signal is generated, the worst one-dot image may be displaced to cause color misregistration. is there.

[0005]

According to the first aspect of the present invention, there is provided an optical writing system which includes one photosensitive member and one transfer drum and starts based on a position signal from the photosensitive member.
Said plurality of times of optical writing of an electrostatic latent image on the photosensitive member so as to obtain a color image by superimposing images of a plurality of colors, an image recording apparatus wherein the photosensitive member and the optical writing system operate asynchronously A plurality of recording light sources in the optical writing system in a sub-scanning direction of the photoconductor.
It is provided to scan different places,
Time between the position signal from the body and the synchronization signal of the optical writing system
Detecting means for comparing the difference with a plurality of predetermined values to detect the difference;
Depending on the time difference issued, whether the plurality of recording light sources
Selecting means for selecting one of them.

According to the second aspect of the present invention, the beams emitted from the plurality of recording light sources are arranged in the sub-scanning direction on the photosensitive member at a pitch in which one dot diameter is equally divided by the number of recording light sources. In this state, a plurality of recording light sources were arranged.

Furthermore, in the invention of claim 3, wherein, provided line buffer a plurality of write data.

According to the fourth aspect of the present invention, a plurality of recording light sources are divided into a plurality of groups to form a plurality of scanning lines, and each of the scanning lines in each group is arranged in the sub-scanning direction on the photosensitive member. A plurality of recording light sources were arranged in a state of being arranged at pitches equally divided by the number of groups.

At this time, according to the invention described in claim 5 , the static electricity
At the time of optical writing of an electro-latent image, a recording light source of any group is selected to perform recording for a plurality of scanning lines.

In addition, according to the invention described in claim 6 , the static
Detecting means for detecting a time difference between a position signal from the photoconductor at the time of optical writing of the electrostatic latent image and a synchronizing signal of the optical writing system by comparing with a plurality of predetermined values; and detecting one time according to the detected time difference. Selecting means for selecting a recording light source of the group.

Furthermore, in the invention of claim 7, wherein a plurality of predetermined values used by the detection means, the electrostatic latent image of the optical writing for the number of recording light source that is not selected during the optical writing said electrostatic latent image < The number obtained by dividing by the number of recording light sources selected at the time of the reading is a number obtained by multiplying the divided line cycle by an integer, and the maximum value is set to a value smaller than the line cycle.

[0012]

According to the invention described in claim 1 or 2 ,
By selecting a plurality of recording light sources and performing optical writing, the amount of dot shift can be suppressed to 1 / (the number of light sources), and the color shift when each color is superimposed can be suppressed.

[0013] In addition, according to the invention of claims 3 to 7, wherein the line for the write data buffer are provided a plurality, so be grouped by a plurality of forming a plurality of scan lines for recording light source Thus, simultaneous recording of a plurality of lines can be performed, and the recording time can be reduced.

[0014]

EXAMPLES be described with reference to an embodiment of the invention of claim 1 or claim 2, wherein in FIGS. 1 to 6. First, FIG. 2 shows the basic operation timing of the optical writing system. Area a
Generally controls the power of a laser diode as a light source and the position detection signal Det. It is used as a period for turning on the light source to generate P. Scan beam position detection signal Det. P is a line synchronization signal L.P. Sync and write data valid area signal L. The reference signal regulates the timing of occurrence of Gate. These signals are always generated when the polygon mirror for laser beam scanning has a constant speed, irrespective of the driving of the main body system (photoconductor, transfer drum, etc.).

Next, the photoconductor position signal HP and the optical writing system position detection signal Det. The relationship with P is shown in FIG. The position signal HP and the position detection signal Det. Since the P are asynchronous, for each color, as the time difference between these signals can vary, for example t ₀ ~t _3. Assuming that the line cycle is T, the illustrated example is t ₀ <T / 4, T / 2 <t ₁ <3T / 4,
It is assumed that t ₂ > 3T / 4 and T / 4 <t ₃ <T / 2.

In this embodiment, a plurality of laser diodes are used as a recording light source. Specifically, 4 a laser diode array emitting a beam is used, each when the LD ₁ to Ld _4, as well as of each beam on the recording medium (photosensitive member) becomes as shown in FIG. 1 It is arranged. That is, when the beam diameter is d,
One dot diameter is equally divided by 4 in the sub-scanning direction, and is arranged so as to have a pitch of d / 4. The four beams are arranged at a pitch of dx (= d / 4) in the main scanning direction.

The operation in the configuration using such a four-beam laser diode array as a light source will be described with reference to FIGS. Now, the position detection signal Det. It is assumed that P occurs at the timing of case a. At this time, since the time difference t ₀ from the position signal HP is t ₀ <T / 4, one pulse of the line synchronizing signal L.P. Upon detecting a Sync, recording is performed to start writing in the most advanced beam of the light source LD ₄ in the sub-scanning direction in FIG. 1. That is, as shown in the case a in FIG. 3, to start the writing with a beam LD ₄ advanced 3/4 dot in the sub-scanning direction relative to the beam LD ₁ regular, 1 all pages of the recording the beam LD Perform according to ₄ .

On the other hand, the position detection signal Det. Assuming that P occurs at the timing of case b, the time difference t ₁ is T / 2 <
Since t ₁ <3T / 4, one pulse of the line synchronizing signal L.T. When Sync is detected, light source L
To start writing beam D ₂ recording is performed. That is, as shown in case b of FIG.
Advanced 1/4 dot in the sub-scanning direction with respect to the _first beam LD
₂ starts writing, and all the recording for one page is performed by the beam LD ₂ .

The position detection signal Det. Assuming that P occurs at the timing of case c, the time difference t ₂ is t ₂ > 3.
T / 4, the one-pulse line synchronization signal L.T. Upon detecting a Sync, recording is performed to start the writing with a beam of the light source LD _1. That is, FIG.
As shown in the case c, writing is started with the regular beam LD ₁ , and recording for one page is entirely performed by the beam LD _1.
Performed by

Further, the position detection signal Det. P is case d
, The time difference t ₃ is T / 4
<T ₃ <T / 2, so that one pulse of the line synchronization signal L. When Sync is detected, light source L
To start writing beam of D ₃ performs recording. That is, as shown in case d of FIG.
Advanced 1/2 dot in the sub-scanning direction with respect to the _first beam LD
To start writing at _3, all the recording of one page is performed by the beam LD _3.

In the second and subsequent writing operations, the same operation as in the first writing operation is performed, so that the position detection signal Det. Even if there is a variation in the time difference between P and the position signal HP, the dots actually written scan substantially the same position (1/4 dot in the example shown in FIG. 3). That is, the dot shift amount is 1 / (number of beams 4).

FIG. 4 shows a circuit for performing such a write operation. First, the position signal HP is counted and the position detection signal Det. Clock CLK until P appears
Is provided. Here, the clock CLK is obtained by dividing the frequency of the pixel clock. Therefore, the counter 1 receives the position signal HP and the position detection signal Det. P
Will be detected. The output of this counter 1 is input to a plurality of, here three, comparators 2, 3, and 4 serving as detecting means. These comparators 2, 3, and 4 are magnitude comparators,
A bit comparison operation with the output of the counter 1 is performed using T / 4, T / 2 and 3T / 4 as predetermined values. A gate circuit 5 is provided as selection means for selecting any one of the light sources LD _{1 to} LD _{4 in} the laser diode array according to a combination of the output states of these comparators 2, 3, and ₄ .

More specifically, first, the position signal HP passes through an inverter 6, a JK flip-flop 7, a D flip-flop 8, and an exclusive OR gate 9 to which the outputs of these flip-flops 7, 8 are input. The signal is input to the counter ₁ as a signal S1. Here, a signal F. designating the number of effective write lines for one page is supplied to the flip-flop 8. Gate is input via the inverter 10.
On the other hand, the position signal HP is the D flip-flop 11
, And the output of the flip-flop 11 outputs the position detection signal Det. The signal is input to the next stage D flip-flop 12 together with P, and these flip-flops 11, 12
The input to the counter 1 as the signal S ₂ through the exclusive OR gate 13 to the output of the input. Further, in order to reduce the number of bits, the reference input of each of the comparators 2, 3, and 4 is given a predetermined value of n × w. The output bit of the value counted by clk is input. The position synchronizing signal L.L. A latch 14 having a flip-flop configuration for opening the gate at Sync is provided, and its output S ₃ is input to the gate circuit 5.

With such a circuit configuration, first, when the position signal HP is generated, the signals S ₁ and S ₂ are both at the H level, and the counter 1 starts the counting operation. Next, the position detection signal Det. When P is generated, the output Q of the flip-flop 12 becomes H level, the signal S ₂ has an L level. As a result, the counter 1 stops the counting operation and the position detection signal Det. The time difference up to P is held and output to comparators 2, 3, and 4. These comparators 2, 3, and 4 have predetermined values T / 4, T
/ 2, 3T / 4 and the output of the counter 1 are subjected to a bit operation, and the magnitude relation is output to the gate circuit 5.

When the signal S ₁ goes high,
The flip-flop 14 is enabled, and the signal S
₃ is the first line synchronization signal L.3 after the position signal HP is generated. S
It goes to the H level in synchronization with ync. The signal S ₃ is a gate circuit 5 is inputted, selects any one from among the light source LD ₁ to Ld ₄ in response to the comparator 2 outputs.

Assuming that the outputs of the comparators 2, 3, and 4 are A, B, and C, the outputs are as shown in Table 1 according to the time difference t.
It becomes as shown in.

[0027]

[Table 1] Inverter 15 as shown the gate circuit 5 in FIG. 5 Correspondingly, by AND gate 22 which receives the exclusive OR gate 16, 17, AND gates 18, 19, 20, 21 and the data signal S ₃ if the circuit arrangement, the light source LD ₁ to Ld ₄ in accordance with the time difference is selected.

The signal F. When Gate goes high, flip-flops 11 and 12 are cleared, and this signal F.G. When Gate falls to L level, flip-flop 8
There becomes H level, the signal S ₁ is at the L level. When the signal S ₁ is at the L level, the signal S ₃ becomes L level, the start signal becomes the L level. Here, F. Gat
e is a signal that specifies the number of effective write lines per page,
Signal S ₃ simultaneously occurs, the the signal S ₃ is generated line synchronization signal L. Generated by a circuit (not shown) that starts counting Sync.

The above-described operation is repeated also in the second and subsequent writing.

[0030] Now, in FIG. 6 showing the write timing for the light source LD ₁ to Ld _4, a data printing section L. Gate is set for each light source LD ₁ ~LD _4.
That, L. light source LD ₁ is selected Writing at the timing of the Gate (1) is performed, L. a light source LD ₃ is selected Writing is performed at the timing of Gate (3). In addition, each L. The delay time d _{0 of} Gate is for correcting the pitch dx between beams in the main scanning direction shown in FIG.

As described above, the signals HP, Det. By selecting any one of the light sources LD ₁ to LD ₄ for recording according to the time difference between P, the dot shift when each color is superimposed is suppressed.

The present embodiment will be described in general terms. Assuming that the number of recording light sources is n, the signals HP, Det. Time difference t between P is, n-th light source in the case of t <T / n (because n-th refers to those advanced most in the sub-scanning direction as light sources LD ₄ in FIG. 1), T / n ≦ t <(n−1) T / n
In the case of (n−x) + 1th light source (where t = x
T / n, x = 1 to n−2), t ≧ (n−1) T /
In the case of n, the first light source is selected and printing is performed, so that the dot shift when each color is superimposed is reduced by one.
/ N.

[0033] Next, will be described with reference to FIGS. 7 through 9 an embodiment of the invention of claim 3 to claim 7. The same parts as those described in the above embodiment are denoted by the same reference numerals. In the present embodiment, the number of recording light sources is further increased, and the light sources located at the same position in the main scanning direction are grouped. That is, a laser diode array having light sources LD _{A1 to} LD _A4 emitting four beams,
Similarly, a laser diode array having light sources LD _{B1 to} LD _B4 emitting four beams is provided. As shown in FIG. 7, the light sources LD _A1 and LD _{B1 form} one group to constitute two lines, and similarly, The light sources LD _A2 and LD _B2 constitute one group to constitute two lines, and the light sources LD _A3 and LD _B3 constitute one group to constitute two lines.
D _A4 and LD _B4 are arranged so as to form one group and constitute two lines. The relationship between the groups is such that the scanning line of each group has a pitch obtained by dividing one dot diameter d by the number of groups 4, that is, a pitch d / 4 divided into four.
Are arranged in the sub-scanning direction.

In such a configuration, control is basically performed in the same manner as in the above-described embodiment. However, in this embodiment, two light sources (one group) are simultaneously selected and two lines of light are selected. A record is made. For example, the case a in FIG. 8 is equivalent to the case a of Fig. 3, instead of the light source LD _4, recording is performed source LD _A4, LD _B4 is selected. That is,
Normal light source LD _A1, LD _B1 source proceeds in each 3/4 dot sub-scan direction relative to the LD _A4, LD starts writing in _B4, these light sources LD _A4 until the page is completed,
Recording is performed for each two lines with the LD _B4 . The photosensitive member is rotated and moved by two lines (two dots) during the line period T.

The same applies to the cases b, c, and d. The difference from FIG. 3 is that two corresponding light sources are selected.

In order to perform such simultaneous recording of a plurality of lines, a plurality of write data line buffers, here for odd lines and even lines, are provided.

In the case of this embodiment as well, control can be performed by the circuit configuration shown in FIG. 4, but since the number of light sources is increased, a gate circuit 23 as shown in FIG. . That is, the output side of the circuit shown in FIG. 5 has a two-stage configuration, and the AND gate 18 is connected to the AND gate 1
8 _A and 18 _B , and the AND gate 19 is
_A , 19 _B, and AND gate 20 is AND gate 2
0 _A and 20 _B , and the AND gate 21 is connected to the AND gate 21.
It is obtained by the _A, 21 _B. Further, for the AND gate 22 also two lines, is replaced by the AND gate 22 _A, 22 _B, are configured to two lines of writing data DataA from each not-shown line buffer, and B are input.

[0038]

According to the present invention, as described above, according to the first or second aspect of the present invention, by selecting a plurality of recording light sources and performing optical writing, a dot is formed. the shift amount can be suppressed to 1 / (the number of light sources), the color shift when superimposing each color can be suppressed, in addition, according to the invention of claims 3 to 7, wherein the line for writing data A plurality of buffers are provided, and a plurality of recording light sources are also grouped so as to form a plurality of scanning lines, so that simultaneous recording of a plurality of lines is possible.
Recording time can also be shortened.

[0039]

[Brief description of the drawings]

1 is a schematic view of the beam positional states of a plurality of light sources showing one embodiment of the invention of claim 1 or 2 wherein.

FIG. 2 is a timing chart showing a basic operation of an optical writing system.

FIG. 3 shows a position signal HP and a position detection signal Det. 6 is a timing chart showing a relationship with P and a beam to be selected.

FIG. 4 is a block diagram.

FIG. 5 is a block diagram showing a gate circuit.

FIG. 6 is a timing chart showing an operation example.

7 is a schematic view of the beam positional states of a plurality of light sources showing one embodiment of the invention of claim 3 to 7, wherein.

FIG. 8 shows a position signal HP and a position detection signal Det. 6 is a timing chart showing a relationship with P and a beam to be selected.

FIG. 9 is a block diagram showing a gate circuit.

[Explanation of symbols]

2,3,4 detecting means 5 and 22 selecting means _{LD 1 ~LD 4, LD A1 ~LD} A4, LD B1 ~LD B4 recording light source

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B41J 2/44 G03G 15/01 112 G03G 15/04 H04N 1/04 H04N 1/23 103

Claims (7)

(57) [Claims] An optical writing system that includes one photoconductor and one transfer drum, and starts an optical writing system based on a position signal from the photoconductor, the optical writing of the electrostatic latent image on the photoconductor is repeated a plurality of times; and to obtain a color image by superimposing images of a plurality of colors, wherein in the photosensitive member and the optical writing system image recording apparatus which operate asynchronously, the mutually a plurality of recording light source in said optical writing system Sub photorun of photoconductor
It is provided to scan different places in the scanning direction,
Position signal from the photoconductor and synchronization signal of the optical writing system
Detection method that compares the time difference with
And a plurality of recording light beams according to the detected time difference.
An image recording apparatus comprising: a selection unit that selects one of the sources . 2. A plurality of recording light sources are arranged such that beams emitted from a plurality of recording light sources are arranged in the sub-scanning direction on the photoconductor at a pitch obtained by equally dividing one dot diameter by the number of recording light sources. the apparatus according to claim 1, characterized in that arranged light sources. 3. The image recording apparatus according to claim 1, further comprising a plurality of write data line buffers. 4. A plurality of recording light sources are divided into a plurality of groups to form a plurality of scanning lines, and each of the scanning lines of each group is equally divided in the sub-scanning direction on the photoconductor by the number of groups. 4. The image recording apparatus according to claim 3 , wherein a plurality of recording light sources are arranged in a line at a pitch. 5. The method according to claim 1, wherein a recording light source of any one group is selected at the time of optical writing of the electrostatic latent image, and recording for a plurality of scanning lines is performed.
5. The image recording apparatus according to 4 . 6. A detecting means for detecting a time difference between a position signal from a photoconductor at the time of optical writing of the electrostatic latent image and a synchronizing signal of the optical writing system by comparing a plurality of predetermined values with each other. 6. The image recording apparatus according to claim 5, further comprising: selecting means for selecting one group of recording light sources according to the time difference. 7. A plurality of predetermined values used by the detection means, before
Select the number of recording light sources that are not selected during the optical writing of the electrostatic latent image.
The number divided by the number of recording light sources selected at the time of optical writing of the electrostatic latent image is a number obtained by dividing the line cycle by an integer, and the maximum value is set to a value smaller than the line cycle. The image recording apparatus according to claim 6, wherein: