JPH0695241B2 - Color electrophotographic recording method and apparatus - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for recording a color image by superimposing and recording a plurality of images of different colors on the same recording medium.

Conventional technology With the recent development of color printers and plotters,
High-quality and large-sized images similar to color printing and color photographs are required, and when a color image is generated by superimposing a plurality of images of different colors, each color must be obtained in order to obtain a high-quality and large-sized image. It is indispensable to align the images of 3 with high accuracy.

A conventional color electrophotographic recording apparatus will be described with reference to FIG. 9. This apparatus comprises a photoconductive image carrier 1, a charger 2, an LED head 3, a developing unit 4, and a transfer roller 5. When,
The cleaning unit 6, the eraser unit 7, the conveying roller 8, the supply roller 9 and the take-up roller 10 for the recording medium 12, and the sensor 11 for aligning the recording medium 12 are roughly configured.

The case of recording a color image in the above configuration will be described. The image carrier 1 whose charge has been previously removed by the eraser unit 7 rotates in the direction of the arrow in the figure and is uniformly charged by the charger 2 and the position described later by the LED head 3. A registration mark and a latent image of the first color image are formed, and the developing device 4 adheres the first color toner to the latent image.

On the other hand, the recording medium 12 is conveyed from the supply roller 9 to the take-up roller 10, and the alignment mark on the image carrier 1 and the image of the first color are transferred via the transfer roller 5.

After the transfer, the cleaning unit 6 removes the residual toner from the image carrier 1 and the eraser unit 7 removes the residual charge. On the other hand, the recording medium 12 has the winding roller 10
And is rewound in the direction of the supply roller 9 to prepare for image recording of the second and subsequent colors.

FIG. 10 shows a case where the registration mark 12a is recorded at the beginning, and then the recording medium 12 on which the image 12b of the first color is recorded is rewound to start recording the image of the second color. In this case, when the sensor 11 detects the alignment mark 12a, L
The ED head 3 superimposes the images at the recording timing so that the ED head 3 starts exposing the image of the second color on the image carrier 1, and similarly, superimposes a plurality of images of different colors to obtain a color image.

Therefore, the alignment mark 12a is formed in a shape and an interval that allows the sensor 11 to distinguish it from the image, and is formed at a position in consideration of the conveyance timing of the recording medium 12 and the rotation timing of the image carrier 1.

Problems to be Solved by the Invention However, according to such a configuration, the recording medium 12 expands and contracts due to the influence of ambient temperature during conveyance during image recording of the previous color, or slips in the conveying direction of the recording medium 12 occur. Due to the lateral meandering, there is a problem in that when an image of the next color is recorded, a positional shift or a color shift occurs.

The above-mentioned problem of expansion and contraction can be dealt with by setting a certain degree of tolerance for positional deviation and color misregistration.
In reality, the range is not wide enough to be dealt with by adjusting the manufacturing specifications of the recording medium and the atmosphere in the device, and especially when a large color image is to be obtained, the displacement and color shift due to expansion and contraction of the recording medium. Cannot be ignored.

Further, the problem of slippage in the transport direction of the recording medium and the meandering in the lateral direction are dealt with by improving the accuracy of designing and manufacturing of the apparatus, so that the apparatus becomes expensive and there is no guarantee that it will fall within an allowable range.

The present invention has been made in view of the above-mentioned problems, and is capable of accurately aligning a plurality of different color images on a recording medium regardless of expansion / contraction of the recording medium, slippage or meandering in the transport direction. It is an object of the present invention to provide an inexpensive color electrophotographic recording method and apparatus capable of overlapping recording and causing no color shift.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention forms a plurality of first marks on a recording medium in advance at predetermined intervals in the carrying direction and at least a second mark extending in the carrying direction. One row of marks is formed, an image is recorded with a preset number of lines between the first marks of the recording medium, the mark interval is measured, and the number of lines and the number of lines of the actually recorded image are calculated. Error is detected.
The number of lines between the next marks is set so that the number of lines between two consecutive marks becomes a predetermined number of lines, and an image is recorded with the set number of lines between the next marks, and at the same time, the second mark is recorded. By detecting the mark, the positional deviation of the recording paper in the direction orthogonal to the conveying direction is detected, and the image is moved in the direction orthogonal to the conveying direction and recorded according to the deviation of the forward starting position.

Operation The present invention has the above-mentioned configuration, and the positional deviation and the color deviation due to the expansion and contraction and the slip in the conveying direction of the recording medium are two continuous first.
Is corrected by making the number of lines between the marks constant, and the positional deviation and color deviation due to meandering of the recording medium are corrected by moving the image on the recording medium in a direction orthogonal to the transport direction.

Embodiments Embodiments of the present invention will be described below with reference to the drawings. First
FIG. 1 is a schematic configuration diagram showing an embodiment of a color electrophotographic recording apparatus according to the present invention, and FIGS. 2 and 3 are explanatory views of the main part.

In FIG. 1, 21 is a photosensitive drum that rotates in the direction of the arrow (sub-scanning direction) and serves as a photoconductive image carrier, 22 is a charger for uniformly charging the photosensitive drum 21, 23 Is an LED head for recording a latent image corresponding to the dots on the photosensitive drum 21 by arranging a plurality of light emitting elements in the width direction of the photosensitive drum 21 (main scanning direction) to emit predetermined dots.
Reference numeral 4 has developing devices 24a, 24b, 24c, and 24d for independently supplying four color toners of black, cyan, magenta, and yellow onto the photosensitive drum 21 to develop the latent image of the corresponding color. Further, the developing unit 25 also serving as a tray for the toner transfers the image visualized in each color by the developing devices 24a, 24b, 24c, and 24d of the developing unit 24 so as to be superimposed on the recording paper 33. The transfer roller, 26 is a cleaning unit for removing the toner remaining on the photosensitive drum 21 after the transfer, and 27 is an eraser unit for uniformly discharging the photosensitive drum 21. The developing unit 24 and the transfer roller 25 each have a structure capable of applying an appropriate bias in order to improve efficiency.

Further, 28 is a transport roller for transporting the recording paper 33 in the direction of the arrow (sub-scanning direction) shown in synchronism with the rotation of the photosensitive drum 21, and 29 is a continuous roll of the recording paper 33 wound in a roll shape. A supply roller for supplying 30, a take-up roller for the recording paper 33, a reference numeral 31 for an optical sensor for detecting expansion and contraction or slippage of the recording paper 33 in the conveyance direction (sub-scanning direction), and a reference numeral 33 for the recording paper 33. It is an optical sensor for detecting the meandering in the direction (main scanning direction) perpendicular to the conveyance direction of the. The LED head 23 and the optical sensor 31
As shown in FIG. 2, is disposed at a position equidistant from the contact point between the photosensitive drum 21 and the transfer roller 25. Further, the transfer roller 25, the conveyance roller 28, the supply roller 29, and the winding roller 30.
Can rewind the recording paper 33 in the direction opposite to the direction of the arrow in the figure.

Next, the alignment marks on the recording paper 33 will be described with reference to FIG. Incidentally, FIG. 3 shows the image 34a of the first color.
The case where the image 34b of the second color on the photosensitive drum 21 is superimposed and recorded on the recording paper 33 on which is recorded, and the description of the same members as those in FIG. 1 will be omitted.

A plurality of registration marks 33a, which serve as alignment marks in the sub-scanning direction, are arranged at both ends outside the image area of the recording paper 33, which is continuous paper, at predetermined equidistant pitches in the carrying direction. At least one line of line marks 33b extending in the direction and serving as a position alignment mark in the main scanning direction is formed. The optical sensors 31, 32 described above
Are arranged to detect the marks 33a and 33b, respectively.

The marks 33a and 33b are recorded in advance before the recording of the image of the first color as described later, but instead, they may be recorded simultaneously with the recording of the image of the first color. Incidentally, if the recording paper 33 is preliminarily colored before the mark recording and is expanded and contracted in accordance with the ambient temperature, it is possible to improve the positioning accuracy and the color matching accuracy during image recording.

Further, although the marks 33a and 33b are formed on both ends of the recording paper 33 respectively, they may be formed together on one end of the recording paper 33 or on the back surface thereof. In the case of the latter back surface, if it is formed near the center, the alignment accuracy is further improved.

The marks 33a and 33b may be printed in advance by another printing means, and the mark 33b is not formed and the recording paper 33 is not formed.
The meandering may be detected by detecting the left end or the right end of the. If printed in advance, marks 33a and 33b will be recorded when recording the image.
Since no image is formed, the image recording time can be shortened.

In the above configuration, first, the case where the marks 33a and 33b are recorded will be described.

In FIG. 1, the photosensitive drum 21, which has been precharged by the eraser unit 27, rotates in the direction of the arrow in the drawing and is uniformly charged by the charger 22, and the LED head 23 forms the latent images of the marks 33a and 33b described above. The developing device 24 develops the latent image with toner of a predetermined color.

On the other hand, the recording paper 33 is conveyed in the direction from the supply roller 29 to the take-up roller 30 in synchronization with the rotation of the photosensitive drum 21, and the transfer roller 33
The images of the marks 33a and 33b on the photosensitive drum 21 are transferred via 25.

After the transfer, the photosensitive drum 21 is cleaned by the cleaning unit 26.
The residual toner is removed by the eraser unit 27, and the residual charge is removed by the eraser unit 27.
Is rewound in the direction of the supply roller 29 to prepare for image recording of the first color and thereafter. When the recording paper 33 is rewound, it is rewound so that the next image recording start position is closer to the supply roller 29 than the optical sensors 31 and 32 are.

The images of the first and subsequent colors are recorded on the recording paper 33 with marks 33a and 33b.
Is detected and the images of the respective colors are aligned and superimposed. Next, this alignment will be described with reference to FIGS. 4 to 7.

FIG. 4 is a registration control circuit diagram for generating a recording trigger signal which is a start timing for the LED head 23 in the sub-scanning direction, and FIG. 5 is a timing chart of the main signal. An image signal is input to the LED head 23 from a circuit (recording driver circuit) not shown.

In FIG. 4, 31 is an optical sensor that detects the mark 33a of the recording paper 33 as described above, and 42 alternately outputs "1" and "0" each time the optical sensor 31 detects the mark 33a. A flip-flop having a Q terminal and a terminal, 43a
43b and 43b are counting circuits for alternately measuring the distance between the marks 33a, and 44a and 44b are marks 3 for the LED head 23.
The division circuit that alternately calculates the period of the recording trigger signal between 3a and outputs the recording trigger signal, 45a and 45b, alternately the recording trigger signal between the next mark 33a by the recording trigger signal of the previous mark 33a. A correction circuit for correcting, 46 is a trigger count circuit for counting the number of pulses of the recording trigger signal, 47a
And 47b are AND circuits, and 48 is an OR circuit.

The operation of the control circuit according to the above configuration will be described. Every time the optical sensor 31 detects one edge of the mark 33a, Q of the flip-flop 42 and the terminal output "1" or "0" to the toggle.

The Q and the terminals are connected to the enable terminals E of the counting circuits 43a and 43b, respectively. Therefore, when the optical sensor 31 detects the edge of the first mark 33a ₁ , the output of the Q terminal of the flip-flop 42 becomes "1". , The counting circuit 43a on the upper side of the drawing shows the next mark 33a by the clock signal CL.
The edge interval (time) T ₁ up to the edge of ₂ (signal A in FIG. 5) is measured.

At this time, since the image component recording by the LED head 23 is not yet performed (the same signal B), the count value of the trigger count circuit 46 is “0” and the correction value of the correction circuit 45a is “0”.
Becomes Therefore, the number of image component latent image lines N ₁ = N to be recorded on the photosensitive drum 21 due to the space between the next marks 33a ₂ and 33b _3.
-0 is determined, the division circuit 44a calculates the period tau ₁ of the recording trigger signal corresponding to the line number N ₁ by the following arithmetic expression _{τ 1 = T 1 / N 1} .

When the optical sensor 31 detects the next edge of the mark 33a ₂ , the Q terminal of the flip-flop 42 becomes “0” terminal, and the counting circuit 43b in the lower stage of the figure shows the time T ₂ between the marks 33a ₂ and 33a _3. measure.

On the other hand, the division circuit 44a on the upper side of the drawing outputs a recording trigger signal of the period τ ₁ , and this signal is gated by the AND circuit 47a for "1", that is, for the time τ ₂ , and the OR circuit 48a. The pulse number is counted by being applied to the LED head 23 via the trigger count circuit 46 as well as being applied to the trigger count circuit 46.

The LED head 23 forms a latent image on the photosensitive drum 21 at the start timing in the sub-scanning direction by the recording trigger signal. Therefore, the interval of the latent image formed on the photosensitive drum 21 in the sub-scanning direction is determined by the recording trigger signal. It corresponds to the period τ ₁ .

The count value of the count circuit 43b in the lower part of the figure is the time T ₁ and T ₂
It becomes N ₁ + Δ ₁ according to the difference of. However, N ₁ + Δ ₁ ≦ T ₂ / τ ₁ <N ₁ + Δ ₁ +1.

In other words, the mark may be expanded or contracted in the conveyance direction of the recording paper 33.
33a _1, 33a ₂ between error delta ₁ between the the number of lines N ₁ and mark 33a _1, 33a number ₂ was actually recorded lines N ₁ + delta ₁ assumed during the recording can be yielded.

Therefore, in the correction circuit 45b, the following calculation formula N _{2 is used} so that the number 2N of image component recording lines between the edge of the first mark 33a _{1 and} the edge of the third mark 33a ₃ becomes N + Δ ₁ + N ₂ = 2N. = N-Δ ₁ , the number N _{2 of} image component lines to be recorded between the following marks 33a ₂ and 33a ₃ is calculated.

Further, the division circuit 44b calculates the pulse period τ ₂ of the recording trigger signal between the marks 33a ₂ and 33a ₃ by the arithmetic expression τ ₂ = T ₂ / N ₂ .

This signal indicates that the Q terminal of the flip-flop 42 is "1" next.
During that period, that is, during the time T ₃ , the AND gate 47b gates the gate, and the gate is applied to the LED head 23 through the OR gate 48.

Similarly, when the count circuit 43b finishes measuring the time T ₃ , the trigger count circuit 46 counts N ₂ + Δ ₂ (however, N ₂ + Δ ₂ ≦ T ₃ / τ ₂ <N ₂ + Δ ₂ +1). In the correction circuit 45a, the next mark 3 depending on the error Δ ₂
Number of recording component latent image lines on photosensitive drum 21 between 3a ₃ and 33a ₄ N ₃
Is calculated by the calculation formula N ₃ = N−Δ ₂ , and the division circuit 45a further calculates the pulse period τ of the recording trigger signal for the next mark 33a ₃ , 33a ₄ by the calculation formula τ ₃ = T ₃ / N _{3. 3} is calculated.

To summarize the above operation, the registration marks 33 that should be recorded on the recording paper 33 at equal intervals in the sub-scanning direction.
The interval of a is alternately measured for each mark interval by the count circuits 43a and 43b, and the error in the sub-scanning direction of the mark interval due to the expansion and contraction and slippage of the recording paper 33 is detected by the trigger count circuit 46, and is recorded between the next marks. The number of image lines to be calculated is calculated for each line interval by the correction circuits 45a and 45b so that the number of image lines between two consecutive marks is constant (2N).
Dividing circuit for recording trigger signal with a cycle corresponding to the number of lines
44a and 44b generate for each mark interval, the recording trigger signal for each mark interval is made into a continuous signal by the logical product circuits 47a, 47b and the logical sum circuit 48 to activate the LED head 23, and the sub-scanning is performed between the marks 33a. The image of the first color is recorded on the recording paper 33 while correcting the directional error.

Similarly, for the images of the second to fourth colors, after rewinding the recording paper 33 for each image, the LED head 23 is activated by the recording trigger signal according to the expansion and contraction of the recording paper 33 in the sub-scanning direction. Four
Color image recording is performed by superimposing color images.

FIG. 6 is a schematic configuration of a line mark control mechanism that detects a position shift of the mark 33b on the recording paper 33 in the main scanning direction and generates a signal indicating a recording start light emitting element of the LED head 23 according to the position shift. FIG. 7 and FIG. 7 show waveform diagrams of the main signals.

In FIG. 6, 51 is a light source for illuminating the recording paper 33, and 52 is a light source.
Is a lens array for collecting the reflected light from the recording paper 33, 32
Is an optical sensor described above, and 53 is a control circuit.

The optical sensor 32 is a line image sensor having light receiving elements arranged at a high density in a direction (main scanning direction) orthogonal to the marks 33b on the recording paper 33, and the control circuit 53 controls each light receiving of the line image sensor 32. A position deviation in the main scanning direction due to meandering of the recording paper 33 is detected according to a signal from the element, and a recording start light emitting element of the LED head 23 is determined according to the position deviation.

In FIG. 7, a signal C is a trigger signal for the line image sensor 32 of the control circuit 53, and signals D, E and F are output signals of the line image sensor 32. In the latter signal, when light is incident on the light receiving element of the line image sensor 32, that is, when the white paper portion of the recording paper 33 is detected, there is a voltage output Vo in the bit, while on the other hand, when light is not incident, That is, it becomes 0 V when the mark 33b is detected.

The signal D is a detection signal when the mark 33b is at the correct position, that is, when the recording paper 33 is not displaced in the main scanning direction, and the n-th light receiving element of the line image sensor 32 is the left end of the mark 33b. Is detected, and the following N light receiving elements detect the width of the mark 33b.

On the other hand, the signal E shows the case where the recording paper 33 is shifted to the right and the n'th light receiving element of the line image sensor 32 detects the left end of the mark 33b. In this case, the control circuit 53 causes the LED head 23 to Control is performed so as to shift by a distance corresponding to the number of light emitting elements (n ² −n) at which image recording is started. Therefore,
A latent image is formed on the photosensitive drum 21 by moving a distance of (n'-n) pieces in the main scanning direction, and even if the recording paper 33 meanders, the image always starts recording from a position equidistant from the mark 33b. To be done.

When the amount of reflected light from the recording paper 33 decreases, the voltage level of the output signal F of the line image sensor 32 decreases, but the position of the light receiving element that detects the mark 33b does not change. Can be accurately detected.

The control of the recording start light emitting element in the main scanning direction with respect to the LED head 23 is performed in accordance with the recording trigger signal in the sub scanning direction described above, and thus a two-dimensional color image in which four color images are accurately superimposed is obtained. .

In the above embodiment, the positional deviation in the main scanning direction was corrected by controlling the recording start light emitting element of the LED head 23. Instead, as shown in FIG. 8, the LED head 23 is moved in the main scanning direction by the stepping motor 54 or the like. Alternatively, the control circuit 55 may drive the motor 54 in accordance with the positional deviation in the main scanning direction detected by the optical sensor 32 to correct the latent image forming position in the main scanning direction with respect to the photosensitive drum 21.

As described above, the first plurality of marks are formed in advance on the recording medium at predetermined intervals in the transport direction, and the second at least one row of marks extending in the transport direction are formed. An image is recorded with a preset number of lines between the first marks, the mark interval is measured, and an error between the line number and the line number of the actually recorded image is detected. The number of lines between the next marks is set so that the number of lines between two consecutive marks becomes a predetermined number, and an image is recorded with the set number of lines between the next marks, and at the same time, the second mark is recorded. By detecting the mark, the positional deviation of the recording paper in the direction orthogonal to the conveying direction is detected, and the image is moved in the direction orthogonal to the conveying direction according to the positional deviation so that the image is recorded. Positional deviations and color deviations due to expansion and contraction and slippage in the transport direction are corrected by making the number of lines between two consecutive first marks constant, and positional deviations and color deviations due to meandering of the recording medium are corrected. Is corrected by moving the image in the direction perpendicular to the conveying direction, and therefore, regardless of expansion / contraction of the recording medium, slippage or meandering in the conveying direction, a plurality of images of different colors can be accurately recorded on the recording medium. It is possible to realize an inexpensive color electrophotographic recording method and apparatus that can perform position-aligned and superimposing recording and that does not cause color misregistration.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of a color electrophotographic recording apparatus according to the present invention, FIGS. 2 and 3 are explanatory diagrams of the same main parts, and FIG. 4 shows correction in the sub-scanning direction. FIG. 5 is a registration control circuit diagram to be executed, FIG. 5 is a timing chart of the main signal, FIG. 6 is a schematic configuration diagram of a line mark control mechanism for correcting the main scanning direction, FIG. FIG. 8 is a schematic configuration diagram showing a modified example of the line mark control mechanism of FIG. 6, FIG. 9 is a schematic configuration diagram showing a conventional color electrophotographic recording apparatus, and FIG. 10 is the apparatus of FIG. FIG. 21 …… Photosensitive drum, 22 …… Charger, 23 …… LED head, 2
4 …… Developing section, 25 …… Transfer roller, 28 …… Conveying roller, 2
9 ...... feed roller, 30 ...... winding roller, 31, 32 ...... optical sensor, 33 ...... recording _{paper, 33a, 33a 1, 33a 2} , 33a 3, 33a 4
...... Registration mark, 33b ...... Line mark, 34a ...... Recorded image, 34b ...... Latent image, 42 ...... Flip-flop, 43a, 43b ...... Count circuit, 44a, 44b ...... Division circuit, 45a, 45b ... ... correction circuit, 46 ... trigger count circuit, 47a, 47b ... AND circuit, 48 ... OR circuit, 53,
55 …… control circuit, 54 …… stepping motor.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuhiro Shimamura 2-3-8 Shimomeguro, Meguro-ku, Tokyo Matsushita Dentsu Co., Ltd. (56) References

Claims (2)

[Claims] 1. A recording medium having a first plurality of marks formed at predetermined intervals in a carrying direction and a second at least one row of marks extending in the carrying direction and preset between first marks of a recording medium. An image is recorded with the number of lines recorded and the mark interval is measured, and an error between the number of lines and the number of lines of the actually recorded image is detected, and the line between two consecutive marks is detected by the mark interval and the error. Set the number of lines between the following marks so that the number is the specified number of lines,
An image is recorded between the following marks with the set number of lines, and the second mark is detected to detect the positional deviation in the direction orthogonal to the conveyance direction of the recording medium, and the image is formed according to the positional deviation. A color electrophotographic recording method, characterized in that the recording is carried out by moving in a direction orthogonal to the carrying direction, and the image recording is carried out by superposing a plurality of different colors. 2. A holding means for holding an image to be recorded on a recording medium, wherein a first plurality of marks are formed at a predetermined interval in the carrying direction and at least a second row of marks are formed extending in the carrying direction. An image carrier, a charger for charging the image carrier, and a latent image corresponding to the image on the image carrier charged by the charger with an arbitrary number of lines between the first marks. A recording station for forming the recording medium, means for visualizing the latent image formed by the recording station in a plurality of different colors, and a means for transferring the visualized image to the recording medium. A transfer unit, a unit for conveying the recording medium in both forward and backward directions to superimpose and record an image on the recording medium, and the first mark interval during conveyance of the recording medium in the forward direction. Means to measure,
Means for setting the number of lines for each of the marks of the latent image formed on the image carrier by the recording station; and means for detecting the number of lines of the latent image actually recorded and output for each of the marks. An error between the number of lines set between the previous marks and the number of lines of the image actually recorded is detected, and the number of lines between two consecutive marks becomes a predetermined number of lines due to the mark interval and the error. Means for correcting the number of lines between the following marks, means for detecting the second mark to detect a positional deviation in the direction orthogonal to the conveyance direction of the recording medium, and the recording station according to the positional deviation. And means for controlling to form a latent image by moving it in a direction orthogonal to the transport direction, and superimposes and records a plurality of images of different colors on the recording medium. Photo recording device.