JPS62232269A - Dot output device - Google Patents

Abstract

PURPOSE:To improve the resolution and the gradation by providing a binarization means for respectively comparing the first pattern pulse of picture data with the second pattern pulse of interpolation picture data and converting into dot information every output line. CONSTITUTION:The interpolation picture data constituting an interpolating line is formed so as to make the correlation density of the picture data corresponding to an input line in the vicinity of the interpolating line a picture element density and the first and the second pattern pulses are generated so as to shift a phase by a prescribed quantity. The output of the binarization result of the interpolating line is binarized by the shifted second pattern signal in a main scanning direction, thereby, binarized by the pseudo correlation density and the correlation density of the picture element density of the picture data of the input line surrounding the picture element of the interpolating line is binarized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a dot output device, such as a laser beam printer, which outputs image data as dot information.

[Prior Art] In recent years, with the advancement of semiconductor technology and the maturation of electrophotography technology, laser beam printers (hereinafter referred to as LBPs) and copying machines that apply LBPs have become popular due to their ability to record high-quality and high-speed images. It is rapidly becoming popular. Along with this widespread use, there is an increasing demand for higher quality image recording for LBP due to the expansion of application fields such as printing. To this end, it has been proposed to increase the recording dot density, or to convert the image data to multivalued data and perform gradation recording using techniques such as pulse width modulation recording.

[Problems to be Solved by the Invention] However, the above-mentioned desire for high-quality image recording inevitably leads to an increase in the amount of image data, but this causes the following problems.

■The increase in knee image data is caused by the increase in the image sending side, for example, in the case of a document reading device that reads a document image and outputs a digital image signal, in order to increase the reading density (sub-scanning density), for example, the CCD of the document reading device. The charge accumulation time of the scanner becomes shorter, making it more susceptible to noise and the like.

In addition, the increase in the amount of image data causes problems in image data transmission, such as the transmission frequency becoming high, making it impossible to lengthen the transmission path, and making it susceptible to external noise. Furthermore, an increase in the amount of image data poses a problem in that when it is processed, for example, converted into multivalued data, the burden on the image processing apparatus increases due to the processing.

(2) Further, in optical printers using light beams such as LBP, the following problems occur. That is, when recording dots are formed using a laser beam, it is difficult to form a beam spot into a square or rectangular shape, so spots with a circular or elliptical shape are often used. These circular or elliptical spots inevitably create gaps between the spots, and for this reason, in the past, the spots have been overlapped to prevent gaps from occurring.

Therefore, especially when trying to express gradations by pulse width modulation, the pulse width (beam spot width) representing the gradation is
changes due to the above-mentioned overlap, making it difficult to express gradation.

The present invention has been made in view of the above-mentioned problems of the prior art, and its purpose is to generate interpolated image data for interpolation lines from image data obtained by scanning with a coarse scanning density, and as a result, to improve resolution and gradation. The object of the present invention is to propose a dot output device that outputs reproduced images with good tonality.

[Means for Solving the Problems] The configuration of the present invention for achieving the above-mentioned problems includes an image data input means for inputting image data obtained by scanning and reading line by line, and an interpolation line for supplementing between the lines. interpolated image data generating means for generating interpolated image data, pattern pulse generating means for generating first and second pattern pulses having a predetermined period and shape, and a first pattern pulse for converting the image data into a first pattern pulse; A binarizing means is provided for comparing the interpolated image data with the second pattern pulse and converting the interpolated image data into dot information for each output line.

[Operation] In the above configuration, the interpolated image data constituting the interpolated line is generated such that the pixel density is the correlation density of the corresponding image data of the input lines before and after the interpolated line, and
The first and second pattern pulses are generated so as to be out of phase with each other by a predetermined amount. Then, the output of the binarization result of the interpolation line is binarized with a "pseudo" correlation density in the main scanning direction by being binarized by the shifted second pattern signal. , in the sub-scanning direction), it is the correlation density itself, so it is a binary value of the correlation density of the pixel density of the image data of the input line surrounding the pixels of the interpolation line.

[Examples] Examples according to the present invention will be described in detail below with reference to the accompanying drawings. The general feature of this embodiment is that an output device such as a printer has a built-in buffer memory, and interpolated image data is created from the image information that is sent, and this is generated as a line in which the phase of the recorded dots is relatively shifted. By recording, the output device records more dots than the number of image data sent, thereby making it possible to reproduce high-quality images. It also has the feature of facilitating tone control when multivalued image data is pulse-width modulated and binarized, and tone recording is performed using the binary image data. A case in which a dot output device having the above characteristics is applied to a so-called laser beam printer (LBP) will be described below.

Laser Beam Printer> FIG. 2 is a diagram showing a specific application example of the LBP 9 to which the present invention is applied. This example represents an embodiment in which the LBP 9 is combined with a document reading device to form a so-called copying device. An outline of this copying apparatus will be explained.

A document 3 placed on a document table glass 4 with its reading surface facing downward is scanned by an optical unit composed of a contact type line image sensor 1 such as a CCD and a light source 2, and the document image is converted into an electrical signal. In other words, the image signal read by the line image sensor 1 is read for one line in the main scanning direction in one reading, and in the sub-scanning direction, the image signal is read by the pulse motor 7, pulley 5, pulley 6, and drive belt 10. The optical unit is moved in the illustrated sub-scanning direction by the sub-scanning drive system, and the entire surface of the document 3 is read. The image data of the document image converted into electrical signals by the line image sensor 1 is sent to the image processing circuit 8, where it is subjected to electrical processing such as analog-to-digital signal conversion and shading correction. It is output to the LBP 9 as digital multivalued image data.

Generally, the scanning speed in the sub-scanning direction (for example, paper feed speed) of the reproduced image output by the LBP 9 and the scanning speed in the sub-scanning direction with respect to the original of the optical unit are basically the same, and as a result, .

A reproduced output is obtained without being reduced or enlarged in either the sub-scanning direction. Therefore, in such a case, the resolution and gradation of the reproduced image directly depend on the scanning density when reading the original. In other words, it is not possible to obtain a high-definition output image from image data read at a coarse scanning density.

By the way, the need for a coarse scanning density is due to, firstly, the fact that the data transfer rate cannot be increased due to problems with the interface between the image processing circuit 8 and the LBP 9, and secondly, the charge accumulation time of the line image sensor 1. This comes from demands such as the need to lengthen the length of the vehicle. As a result, L
If the scanning density was made the same on the BPQ side as on the reading side, the coarse reading density directly became the coarse recording density, resulting in a decrease in resolution, etc.

Therefore, by applying the present invention to LBP9 of a copying machine as shown in Fig. 2, it becomes possible to interpolate image data on the LBPQ side (on the output side), and as a result, there is no resolution deterioration and the image data on the document reading device side can be interpolated. In particular, it is possible to reduce the pixel (line) density in the sub-scanning direction.

Next, the dot recording mechanism in the laser beam printer 9 will be explained using FIG. A laser beam output from a semiconductor laser 19 is corrected into parallel light by a collimator lens 11, and is irradiated onto a polygon mirror 12 which is rotated in the direction shown in the figure by a scanner motor 13. It should be noted that the binary signal input to the semiconductor laser 19 is, as will be described later, multivalued image data that has been pulse width modulated and binarized, for example.

Further, the laser beam reflected by the polygon mirror 12 is corrected by the fθ lens 14 and forms a dot on the photosensitive drum 18. The polygon mirror 12 is used for main scanning in the LBP 9. The mirror 15 reflects the laser beam before the photosensitive drum 18 is irradiated with the laser beam, and generates a timing signal (=BD) for the optical sensor 17 to start outputting recording dots via the optical fiber 16. used. That is, the signal BD becomes a horizontal synchronization signal. Further, rotation of the photosensitive drum 18 in the illustrated direction provides sub-scanning. As will be described later, each signal used inside the LBP 9 is created based on the signal BD generated by the optical sensor 17. Therefore, as shown in FIG.
The PH flaw signal generated based on is sent to the image processing circuit 8,
In synchronization with this PH flaw signal, multivalued image data MI for LBP9 is outputted from image processing circuit 8. This signal P
H will be explained in detail later.

Interpolation of Image Data> FIG. 4 is a diagram showing an example of interpolation of image data according to this embodiment in LBP9. The outline is as follows.

In the document reading device shown in Figure 2, the document is scanned in main scan mode.

Scanned in the sub-scanning direction. As a result, as shown in FIG. 4, the image data of the first line, second line, and third line are read one after another. On the other hand, on the LBP9 side, the first line recording scan (this scan is called the main scan) and the second
An interpolation line is provided between main scan lines, and image data of this interpolation line is also scanned (sub-scan) and output.

This is image data interpolation, and basically, image data of interpolated lines (hereinafter referred to as interpolated image data) is synthesized from image data actually read by a reading device.

Various embodiments can be considered for this synthesis method depending on how the pixel density of interpolated image data is determined, and in which pixel position such pixel density is determined, in other words, how to determine the pixel density of the interpolated image data. Various embodiments can be considered depending on the timing at which value conversion is performed. In the embodiment described below, as a method for determining the pixel density of interpolated image data, the correlation density (for example, average density) of the density of two corresponding pixels of the previous line is used as shown in FIG. as the pixel density of the interpolated image data, or as shown in FIG. It is also conceivable to use the correlation density of pixels between the front and rear lines as the density of the interpolated image data, as shown in FIG. 5(C).

Furthermore, regarding the pixel position of the interpolated image data (position at the recording dot), the recording dot is formed at a position shifted by half a dot width from the pixel position of the previous line, as shown in FIGS. 5(a) and (b). There may be other methods, such as forming interpolated image data at the same pixel position as the image data of the previous and succeeding lines, as shown in FIG. 5(C). In particular, regarding the pixel position of interpolated image data, as mentioned above, in LBP, in order to minimize the overlap of recording dots caused by using a beam with a circular or elliptical spot shape, the recording dots of the interpolation line must be The position is shown in Figure 5 (a) and (b).
) is preferable. This point will be explained using FIG. 1.

FIG. 1 shows the concept of scanning when recording on the LBPQ side is viewed from the point of the laser beam spot.

1 as main scan 1 which is stored in the built-in buffer memory of LBP9 (described later) and read out as shown in the figure.
, 2, 3, 4 to n-1, n in the order of circular dots. Next, the recording dots of sub-scan 1 are recorded in the same manner, with the dot phase shifted by half, and using the data stored in the same buffer memory. After that, based on one line of image data sent from the document reading device in the same way,
The two-line recording of main scan and sub-scan is repeated by LBP9.

In this way, the number of dots recorded by the LBP 9 increases relative to the number of image data sent by the document reading device, so the reading density of the document reading device increases from the reading density of 1 in the main scanning direction to the reading density in the sub-scanning direction. The reading density in the direction is approximately 0.56. Therefore, compared to the conventional 1:1 reading density, the document reading device can take more time to accumulate photoelectric charges in the line image sensor 1, and can also take longer to transmit image data, so This produces effects such as being able to lower the frequency, which is extremely advantageous in terms of circuit configuration. That is, as can be seen from FIG. 1, the overlapping portion of the recorded dots in the main scanning direction is extremely small. This is largely due to the fact that the interpolation lines are shifted by half a dot.

In addition, by providing an interpolation line, there is no need to use a laser with an elliptical spot like in the past, and even though the recording dots on the interpolation line are shifted by half a dot width, there is no overlapping in the sub-scanning direction. The area of the lapped portion is reduced.

In addition, to explain the dots a and b (the final dot recording position of the sub-scan for one line) drawn by the broken line in FIG. Since one example of this embodiment correlates the dot recording of the sub-scan with adjacent image data of the main scan, recording of these dots a and b becomes unnecessary.

However, recording may be performed when the recording density is high or when there is no need to correlate image data. Further, in the position embodiment described later, it becomes possible to record dots at the final position as shown in FIG.

<Interpolated Image Data Generation/Binarization Circuit> FIG. 7 shows a block configuration diagram of a circuit that is the original form for generating interpolated image data and binarizing the interpolated image data together with input image data.

Multivalued image data MI from the image processing circuit 8 is stored in the buffer memory 200. The multivalued image data M○ stored in the buffer memory 200 is directly passed through the selector 202 for the main scan and is binarized by a binarization circuit 203 using pulse width modulation. On the other hand, for sub-scanning, the image data MO read out from the buffer memory 200 again is subjected to density calculation for interpolated image data by the density calculation circuit 201, and is then sent via the selector 202 to a pulse width modulated binary The data is binarized by the conversion circuit 203.

The concentration calculation circuit 201 is configured as shown in FIG. 5 (
Various correlation concentrations such as a) to (C) can be taken. These specific operations will become more clear in the specific circuit examples described later.

For both main scan and sub-scan, the output of the binarization circuit 203 is modulated into a laser beam by a laser driver 204. As described above, this laser beam is partially reflected by the reflection mirror 15 in FIG. 3, and becomes a BD scratch signal. Timing generation circuit 2 of this BD scratch signal Fig. 7
05 and is used to create various reference timings. One of the reference timings is the PH flaw signal, which is divided into main scan and sub scan, and is sent to the selector 202.
is a select signal for selecting image data. Other reference timings are the read clock and the binarization clock. In some embodiments described below, FIG.
) and (b), the recording dots of the interpolation lines shown in FIGS. This is achieved by establishing a relative phase relationship among the D signal, read clock, and binary clock.

In FIG. 8(a), the read clock and the binarization clock are made to have the same phase for both the main scan and the sub scan. Therefore, in order to shift by half a dot in the sub-scan, it is sufficient to generate both of the above clocks by shifting the BD scratch signal in the sub-scan by a predetermined amount (left margin of 11/2 dots). In this way, the image data is read out with a temporal shift of half a dot width relative to the main scan, and the image data is binarized as is, resulting in the recorded dots of the sub scan being shifted by half a dot.

Further, as shown in FIG. 8(b), the main scan read clock and the sub scan read clock are generated in the same phase, and the binarized clock is shifted by half a dot width between the two scans. If this is done, the recorded dots of the sub-scan will be shifted by half a dot with respect to the recorded dots of the main scan, as in FIG. 8(a). In addition, by shifting the binarization clock by half a dot width, the shifted binarization clock spans two pixels, so the result is equivalent even without calculating the average density as shown in Figure 5(a). be effective. This point will be explained in detail in the third specific example below.

<Pulse width modulation binarization circuit> Here, a specific circuit of the pulse width modulation binarization circuit 203 will be explained with reference to FIG. DT is image data of a main scan line or a sub scan line. Image data DT
is a digital-to-analog conversion circuit (D/A conversion circuit) 20
The digital signal is converted into an analog signal TL.

This signal TL is connected to the positive input terminal of the comparator 22 at the next stage. The triangular wave generation circuit 21 is a circuit for repeatedly generating a triangular wave for a period equal to the clock CK in synchronization with the binary clock CK. The signal TW, which is a triangular wave output, is connected to the negative input terminal of the comparator 22.

The signal TW does not have to be a triangular wave, but may be a sawtooth wave or a sine wave, for example, as long as it has a predetermined period and pattern.

During one image clock, the signal TL is a constant value, and the signal T
Since W changes gradually increasing and decreasing, comparator 2
The output of 2 is “ when the value of the signal TW is smaller than the signal TL.
1'', and the pulse width signal PW corresponds to the analog value of the signal TL.

In other words, the density of the image data is modulated by the pulse width.

<First Example> Next, an example of a specific circuit configuration diagram of dot recording according to this example will be explained using FIG. 10.

Input image data Ml from the image processing device 8 is stored in the memory 30.
, are temporarily stored in the memory 31. The reason there are two memories is to write and read from the memories at the same time. Memory 30. 1 in either memory 31
While writing input image data MI for lines,
Read the previous line image data from the other memory 2
The scanning is performed once for the main scan and once for the sub-scan. As the memories 30 and 31, first-in-first-out memory (FIFO memory), randomly accessible static RAM, etc. can be used.

The memory control circuit 34 controls the memory 30. It generates a signal MS for controlling writing/reading of the memory 31 and controlling the selector 33. The image data selected by the signal MS is input to the next stage D-type flip-flop (hereinafter referred to as OFF) 35 as image data M0. These memories 30, 31 and selectors 33. The memory control circuit 34 and the like substantially constitute the buffer memory 200 described above. The DFFs 35, 37, and 43 are used to adjust the timing of image signals. In particular, the DFF 37 forms a delay circuit for concentration calculation.

FIG. 11 shows memory write/read timing control. Referring to FIG. 11, the signal BD is the aforementioned horizontal synchronization signal, and is generated every time the laser beam starts main scanning. Signal PH is a signal that determines whether the current scan is main scan or sub-scan.When PH is "o", it is main scan, and when PH is "1°, it is sub-scan.
S changes to alternately select memories 30, 31 for each main scan. Therefore, the output M of the selector 33
O is the memory 30 during one period of the signal PH for the signal MS.
．． Select only one of 31, and as a result, the output MO
The same data is carried at two speeds during the above-mentioned one cycle. The second data is for secondary scanning. In this way, the input multilevel image data MI can be stored in the memory during one PH signal pulse (=2 pulses of signal BD) as shown in the figure, and during this time, the same image is stored inside LBP9 in synchronization with signal BD. The data MO is read twice from the buffer, and two lines of dots are recorded on the photosensitive drum 18.

Next, a circuit for calculating the pixel density for the interpolation line (sub-scan) will be described. Returning to FIG. 10, the addition circuit 39 is a circuit for creating the density of image data during sub-scanning. The embodiment of FIG. 10 performs the density calculation shown in FIG. 5(a), that is, the averaging of adjacent pixel data in the previous line (main scan). The adder circuit 39 is, for example, an 8-bit adder, and the output Y=(A+B
). By taking the upper 8 bits of this output, ignoring the lower 1 bit, and inputting the upper 8 bits to the selector 42 at the next stage, division by 2 is realized. That is, Y= (A+B
)/2 is obtained. In this way, the concentration calculation circuit 2 in FIG.
01 is realized.

The selector 42 is a circuit for selecting data during main scan and sub-scan. When the signal PH is 0", the A input (i.e. main scan) is selected, and when the signal PH is "1" high, the A input is selected. It is assumed that the B input (ie, sub-scan) is selected.

The image data DT whose timing was taken by the DFF43 is
The PWM circuit 44 performs pulse width modulation according to the value of the image data DT and converts it into a pulse signal PW. Regarding this PWM circuit 44, the pulse width modulation binarization circuit 203 in FIG.
This is explained in detail in FIG. 9. What should be noted here is PW
The binarization clock used in the M circuit 44 and the clock used for memory reading are the same clock CK.

That is, this corresponds to the phase relationship shown in FIG. 8(a), so in the sub-scan cycle, it is necessary to generate the clock CK shifted by half a dot as shown in FIG. 8(a). A circuit for this purpose will be explained in relation to the timing generation circuit below.

The laser driver 45 is a circuit that generates a signal for driving a semiconductor laser 46 (corresponding to the semiconductor laser 19 in FIG. 3) using a pulse width modulated binary signal pw.
Optical sensor 47 (corresponding to optical sensor 17 in Fig. 3) outputs signal B.
At a timing near when D is generated, the semiconductor laser 46
lights up. The signal BD generated by the optical sensor 47 is used by a toggle flip-flop (TFF) 48 to generate the signal PH. That is, the signal PH is inverted for each signal BD.

The signal BD is also used for synchronizing the clock CK in the counter 49, which is a synchronous up-counter. The counter 49 divides the frequency of the clock MC output from the oscillation circuit (OSC) 50 to generate the clock CK. In this embodiment, by counting 4 bits in the counter 49, the frequency ratio of the clock MC and the clock CK is set to 16:1.
It is said that In order to create the phase shift that should be generated between the above-mentioned main scan and sub-scan, that is, to accurately record dots on the photosensitive drum 18 with respect to the signal BD,
A signal PH is input to the highest preset input (D) of the counter 49. Further, the signal BD is input to the parallel load (LD) terminal of the counter 49. Then, signal B
Each time D is input, the signal PH is inverted and the preset value of the counter 49 becomes "0" or 8" depending on the signal PH. The clock CK is input to the final stage (Q) of the counter 49.
D), the phase of the clock CK is shifted by half a period between the main scan and the sub-scan. In this embodiment, one cycle of the clock CK corresponds to one dot, so a shift of half a cycle becomes a shift of half a dot.

Next, an example of the circuit operation of FIG. 10 will be explained using the timing chart of FIG. 12.

In Fig. 12, the output of TFF48 in Fig. 10 = PH
The timing when the signal is "0" (main scan) is shown in the upper half, and the timing when the signal is "1" (sub-scan) is shown in the lower half.

When the PH flaw signal is 0°, the image data DT is read out with a clock delay of only the left margin as shown. In the case of the PH flaw signal "°0", the counter 49 in FIG.
The count-up operation starts from "0". Therefore, the output terminal QD, which is the frequency of the clock MC divided by 16, outputs the clock CK as shown in FIG.

On the other hand, when the PH flaw signal is "1", the image data DT is read out with a clock delay of (left margin and zinc clock) as shown in the figure. When it becomes from °゛0”, the value “
This is to start the count-up operation from 8". In this way, the sub-scan is recorded at a position shifted by half a dot width from the main scan recording dot. Also, the image data DT is added by the signal PH. Since the average value of the circuit 39 is selected, dots as shown in the figure are recorded for the dots in the case of the PH flaw signal "O".

(Effects of First Example) According to the example described above, the following effects can be obtained.

■:: By generating interpolation lines from image data,
A reproduced image with high resolution can be obtained using image data with a small amount of information. The small amount of information allows for slower data transfer and prevents interface problems. Also, since the reading density in the sub-scanning direction can be lowered, C
When a CD or the like is used, the charge accumulation time can be increased. Of course, it is also possible to insert a plurality of interpolation lines between the preceding and succeeding main lines.

■: By adding an interpolation line, the laser beam spot can be changed from an elliptical shape to a circular one.

■: Since the recorded dots in the secondary scan are shifted by half a dot width from the recorded dots in the main scan, it is possible to reduce not only the overlap of recorded dots in the main scanning direction but also the overlap in the secondary scanning direction. This prevents deterioration in the reproducibility of gradation expression, especially during gradation recording using pulse width modulation.

■:: The pixel density of the interpolated image data (sub-scan) is the average value (correlation value) of the left and right pixel densities of the corresponding previous line (main scan), so the image reproduction of the interpolated line is smooth and the resolution does not deteriorate.

■: To shift the recording dot in the half-tread 98-width sub-scan, the readout clock and binarization clock are generated in synchronization with the horizontal synchronization signal (BD), and the clock generation is also preset. Since we are using a type counter,
The above half-dot shift can be reliably generated, and the circuit scale is simple.

Second Embodiment In the embodiment shown in FIG. 10, density generation of interpolated image data for sub-scanning is performed based on the concept shown in FIG. 8(a). In the next embodiment shown in FIG. 13, the density is set according to the concept shown in FIG. 8(b). In other words, regarding the interpolated image data of the interpolated line, 4 of the two main lines before and after it
The average density of the two pixels is taken. By doing this, the aim is to further improve the reproducibility of thin lines and the reproducibility of one gradation than the embodiment shown in FIG.

This will be explained according to the circuit shown in FIG. memory 30,
31 and 32 process two lines of image data at the same time, so three are required. Select signal MS of selector 33
are 2 bits MSo and MSl. Addition circuits 39-4
1 is a circuit for obtaining the image data density of the sub-scan. The adder circuit 39 calculates the average density of the previous main line, the adder 40 calculates the average density of the next main line,
The adder 41 calculates the average density of the four pixels. In counters 39-41, bit shifting techniques are used to divide by "2", similar to the adders in the circuit of FIG. As a result, it was shifted by 2 bits, (
A+B+C+D)/4 is obtained.

In Fig. 14, signals BD, PH, MI, MO, MO', M
A timing chart of SO and MSx is given. here,
MO and MO' are image data outputs of the previous main line and the next main line, respectively.

Effects of the second embodiment> In addition to the effects obtained from the embodiment shown in FIG. Rise.

<Third Embodiment> The main purpose of the third embodiment shown in FIG. 15 is to achieve substantially the same effect with a circuit that is simpler than the two embodiments described above. As shown in FIG. 8(b), by shifting the binary clock by half a dot width and generating it in the sub-scan, one binary clock spans two pixels. When binarization is performed using pulse width modulation, the same effect as the binarization based on the average density described in the above two embodiments can be obtained.

For this purpose, the read clock CC and the binarization clock C
K and K are generated with a shift of half a cycle. counter 4
9 is the first. There is no change from that of the second embodiment. Because of the exclusive OR gate 52, the read clock CC always has a constant phase with respect to any signal BD. In other words, the phase does not change between the main scan and the sub-scan. However, the phase of the binarized clock CK is shifted by half a cycle between the main scan and the sub-scan, as in the two embodiments described above. In this way, as shown in FIG. 16, the read clock CC and the binarized clock CK are
is in phase when “O”), but when sub-scan (PH is “O”)
”), the phase is reversed.

When such a binary clock CK is input to the PWM circuit shown in FIG. 9, the signal TW is output in synchronization with the clock CK, so in the sub-scan, a triangular wave TW shifted by half a dot is generated.
It is binarized by At this time, the output of the PWM circuit can be considered as a dot based on the average value of adjacent pixels of the image data DT, and a similar effect can be obtained by shifting the binary clock of the car by half a cycle. In the timing chart for PH-“1” in FIG. 16, so that it can be visually understood that the sub-scan dots based on this example produce the same effect as the binarization based on the average density, The shape of the recording dot is drawn as a combination of semicircles. Of course, the actual shape of the dot is a circle, but the width of the dot corresponds to an average of 4 pixels of 2 pixels.

Fourth Example> The fourth example shown in FIG. 17 is similar to the second example shown in FIG.
In order to obtain the same effect as the embodiment, instead of calculating the average density in the main scanning direction, the method of calculating the "pseudo" average density shown in the third embodiment described above is applied. As a result, the circuit configuration of this example is as follows with respect to the circuit of FIG.
The adder 39 is sufficient for calculating the average density only in the sub-scanning direction, and the phase relationship between the binarization clock CK and the readout clock CC is set so that the phases are opposite in the sub-scanning cycle as shown in FIG. It has the same circuit configuration.

By doing this, the effect obtained by the embodiment of FIG. 13 can be obtained with a much simpler circuit configuration.

<Other Modifications> In the embodiments described above, circular markings 2 are used as shown in FIG.
Although an etot is used, it is conceivable to use a dot shape such as an ellipse to record in a laser beam printer as shown in FIGS. 18(a) to 18(C).

FIG. 18(a) is a diagram showing the arrangement of recording dots when the ratio of the main scanning density to the sub-scanning density of the image data sent to the LBP 9 is set to 1:1. Similarly, in Figure 18 (
b) is a diagram showing the arrangement of recording dots when the ratio of the main scanning density to the sub-scanning density of the image data sent to the LBP 9 is set to 2=1. Furthermore, FIG. 18(c) shows that LB
9 is a diagram showing the arrangement of recording dots when the ratio of the main scanning density and the sub-scanning density of the image data sent to P9 is set to 1:2. FIG.

Further, in this embodiment, an LBP is assumed as the output device, but the present invention is not limited to this, since the present invention can be applied to any output device capable of dot recording.

[Effects of the Invention] As explained above, according to the present invention, it is possible to generate interpolated image data for interpolation lines from image data obtained by scanning with a coarse scanning density, and as a result, the image reading side It has become possible to output reproduced images with good resolution and gradation on the output side. Furthermore, even with a simple circuit configuration, the density change of the interpolation line can be made smooth, and the resolution in the main scanning direction and the sub-scanning direction on the output side is improved.

[Brief explanation of drawings]

Fig. 1 is a diagram explaining the generation of recording dots when the present invention is applied to LBP, Fig. 2 is a block diagram of a copying apparatus when the present invention is applied to LBP, and Fig. 3 is a diagram illustrating the light beam scanning in LBP. Figures 4(a) and 4(b) are diagrams explaining the relationship between document reading scanning and laser beam scanning. Figures 5(a) to (C) are diagrams explaining the principle of generating the density of interpolated image data. 6 is a diagram explaining a modification of FIG. 1, FIG. 7 is a circuit block diagram explaining the principle operation of the embodiment, and FIGS. 8(a) and 8(b) are diagrams showing the read clock and Figure 9 is a circuit diagram of the PWM circuit; Figure 10 is a circuit diagram of the first embodiment; Figure 11 is a memory read timing chart of the buffer memory in the first embodiment. , FIG. 12 shows the first embodiment,
13 is a circuit diagram of the second embodiment. FIG. 14 is a memory read timing chart of the second and fourth embodiments. FIG. 15 is a third embodiment. 16 is an operation timing chart of the third and fourth embodiments, FIG. 17 is a circuit diagram of the fourth embodiment, and FIGS. 18(a) to (C) are diagrams of other modified examples. FIG. 3 is a diagram illustrating recording dots. In the figure, 1... Line image sensor, 3... Document, 8...
・Image processing circuit, 9...LBP, 11...Collimator lens, 12...Polygon mirror, 15...Reflection mirror, 17...Sensor, 19.46...Semiconductor laser, 20...・D/A converter, 21... Triangular wave generation circuit, 22... Comparator, 30, 31.32...
・Memory, 33.42...Selector, 35, 36, 3
7,38°43.48...Flip-flop, 39,
40.41... Adder, 44... PWM circuit, 45
...Laser driver, 49...Counter, 200.
...Buffer Amezori, 201...Concentration calculation circuit, 20
2... Selector, 203... Pulse width modulation binarization circuit, 205... Timing chart generation circuit. Patent applicant Canon Co., Ltd.-1?1st ward? ) 1 lid, ? ,)

Claims (2)

[Claims] (1) An image data input means for inputting image data obtained by scanning and reading line by line, and interpolated image data constituting an interpolation line that supplements between the lines, which inputs the image data corresponding to the pixel position of the interpolation line. interpolated image data generation means for generating interpolated image data whose pixel density is the correlation density of image data of input lines before and after the interpolated line; a pattern pulse generating means for generating first and second pattern pulses, and comparing the image data with the first pattern pulse and the interpolated image data with the second pattern pulse, respectively, to obtain dot information for each output line. A dot output device comprising a binarization means for converting. (2) The dot output device according to claim 1, wherein the predetermined amount of phase shift is approximately half the dot width.