JPS58150365A - Jitter compensating system - Google Patents

Abstract

PURPOSE:To ensure the electric compensation of jitter, by using a ratio between the scanning locus length of each face of a rotary polyhedral mirror and the reference face to the compensating value and calculating the scanning frequency from said compensating value to use it as a scan timing pulse of a picture scanner. CONSTITUTION:The light radiated from a laser light source 1 is turned by a reflecting mirror 3 after passing through a laser modulator 2 and made incident to a rotary polyhedral mirror 4. The light reflected by the mirror 3 irradiates an original 13 via a ftheta lens 7 and a flat reflecting mirror 8. Then each face of the mirror 4 is recognized, and the recognizing code of each face of the mirror 4 is added to a scanning locus. Thus the light source 1 is driven for a fixed time to measure the length of the scanning locus. The ratio between the scanning locus length of each face of the mirror 4 and the reference face is obtained from the result of the above-mentioned measurement and used to the compensating value. Furthermore the compensating value is selected in response to the revolution of the mirror 4, and the scanning frequency is calculated from the desired scanning density and said compensating value. Then a scan timing pulse is produced for a picture scanner.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device such as a facsimile or a scanner device that optically and mechanically scans a document image and transmits or stores the image in a storage device, particularly a flat surface device that scans a document image using a rotating polygon mirror. Regarding a jitter correction method in a scanning facsimile or scanner device, this method aims to electrically correct jitter caused by optical non-uniformity between each surface of a rotating polygon mirror and obtain a distortion-free scanned image. In addition,
To provide an adjustment means that allows the amount of correction to be easily determined when setting the amount of electrical correction.

Conventionally, rotating polygon mirrors have been used in flat scanning facsimile or scanner devices, particularly in applications that require high-speed scanning.

However, it is difficult to reduce the division angle error of a rotating polygon mirror to less than a few seconds in manufacturing, and for applications with a large reading scanning density, such as scanning a 400-inch range with 454 pixels per inch, the above-mentioned rotating polygon mirror is used. Jitter that occurs periodically due to the division angle error can extend to several pixels, resulting in deterioration of image quality.

In order to remove this jitter, is there any way to remove jitter by setting a sampling frequency for each face of the rotating polygon mirror and switching it in synchronization with the rotation of each face? Furthermore, in applications where scanning is performed at an arbitrary magnification, the sampling frequency must be arbitrarily selected, making it difficult to apply the above-described method.

The present invention provides a method for electrically correcting the jitter.

Hereinafter, an embodiment in which the present invention is applied to a scanner device will be described with reference to the drawings.

FIG. 1 shows the mechanical and optical parts of the scanner device. The light emitted from the laser light source 1 passes through the laser modulator 2,
The direction of the light is changed by the reflecting mirror 3 and the light enters the rotating polygon mirror 4. The rotating polygon mirror 4 is driven by a main scanning motor 5 equipped with an encoder 6 for generating a mirror 0 surface interphase signal, and rotates in the direction of the arrow. In this device, the rotating polygon mirror 4 is an example of a six-sided mirror.

The light reflected by the rotating polygon mirror 4 secures a uniform spot diameter within the scanning range, passes through the fθ lens 7 for uniform speed scanning, is redirected by the flat reflecting mirror 8, and is directed to the original 13. irradiate. Reflected light from the original 13 is guided to a photomultiplier tube 12 through a glass fiber 11 and converted into an electrical signal. In addition, in front of the flat reflective mirror 8, a scan start point sensor 9 and a scan end point sensor 1o for generating a scan synchronization signal are arranged.

FIG. 2 shows the electric circuit of the scanner device, particularly the electric circuit for jitter correction.

The reference plane sampling frequency calculator 21 calculates the scanning density C1
The reference surface sampling frequency 03 is calculated from the reference surface scanning speed C2 and the reference surface scanning speed C2. The correction constant storage unit 27 stores correction constant write data C9 set by the correction constant writer 26.

The image signal generator 29 generates image signals C11 for surfaces 0 to 6 using the mirror 0 synchronization signal C13 and the scan end point sensor signal C14. The surface correction constant switch 28 receives the surface signal C1.
According to the surface specified by 1, the value of the specified surface among the six surface correction constants 010, which is the output of the correction constant storage section 27, is output as the surface correction constant CI2. The surface sampling frequency calculator 22 calculates the reference surface sampling frequency 03.
A surface sampling frequency 04 is calculated from the surface correction constant 012 and is applied to the sampling pulse generator 23. The sampling pulse generator 23 receives the scan start point sensor signal 01.
5, a sampling pulse C6 of a set frequency is generated. On the other hand, the image signal C6 generated by the photomultiplier tube 12 in FIG. 1 is sampled by the image signal sampling circuit 24, becomes a sampled image signal C7, is stored in the image signal buffer memory 26, and is output as an image signal output C8. The surface code generator 3o generates an adjustment pattern for sick correction from the surface signal C11, the scan start point sensor signal C15, and the sampling pulse C6, and outputs it as a laser beam drive signal.

If you place photographic paper or film for recording in place of manuscript 13 in Figure 1 of Kintetsu and operate it (the following explanation assumes that photographic paper is placed), the locus of the laser beam will be recorded on the photographic paper. . At this time, if the laser beam is made to shine for a certain period of time after passing through the scanning start point sensor 9, the scanning by each surface of the rotating polygon mirror 4 will be recorded on the photographic paper. This situation will be explained using FIG. 3.

Scanning start point sensor signal C16 and scanning end point sensor signal C14
The area sandwiched by each pulse signal is defined as the document effective dimension, and a certain period of time To from the scan start point sensor signal C16
When a laser beam driving pulse D1 having a pulse width of is applied to the laser modulator 2, the repetition of the scanning locus of the laser beam on each surface from PO to P5 is recorded on the photographic paper. Now, if the Q plane of the rotating polygon mirror 4 is used as a reference plane, and the length of its scanning locus Po is LO, and the length of the scanning locus Pn on the n plane is Ln, then the length of the scanning locus on the n plane is LO. It can be seen that in order to make it equal to , the laser light drive pulse D1 should have a pulse width of Tn shown below.

0 Tn=-XT.

Ln The fact that the scanning loci have the same length means that the same length is being scanned and read. Therefore, the interval of Lo is m
Considering that it is read in parts, the sampling pulse frequency at that time is fo = -T.

fn=-n. Therefore, the sampling pulse frequency of the n plane is n f' n = −X f using the reference plane sampling pulse frequency fo.

L.

becomes. That is, by using the n-th interval sampling frequency obtained by multiplying the reference plane sampling frequency by the n-th plane correction constant, it is possible to perform scanning reading without generating jitter.

When the above is applied to the configuration shown in FIG. 2, the reference plane sampling frequency 03 becomes C3-C1xC2 (Hz) due to the scanning density C1 pixel/man and the reference plane scanning speed 02/S. Also, using the surface correction constant 012 selected from the correction constants for each surface, the surface sampling frequency C4 is calculated as 04=C
1XC2XC12 (Hz), and sampling pulses for each plane are generated at this frequency.

By the way, in order to determine the correction constant for each surface, as described in conjunction with Figure 3, the laser beam for reading and scanning is emitted for a certain period of time and the length of the trajectory on the document surface is measured for each surface. In reality, it is difficult to separate the trajectory of each surface from the recorded trajectory. In order to identify which surface the recorded trajectory is on, the surface code generator shown in Figure 2 controls the laser beam drive signal so that an identification code is included in the trajectory of each surface during recording. vessel 3o
It is. The surface code invention will be explained in detail below.

FIG. 4 shows a detailed configuration diagram of the surface code generator 3o explained in FIG. 2, and FIG. 5 shows its operation timing diagram. The 4-bit counter 3 is activated by the scanning start point sensor signal C15.
1 and 32 and flip-flop 36 are cleared;
A surface signal C is sent to the 3-bit programmable down counter 33.
11 is loaded. Thereafter, each counter starts operating by the sampling pulse c6. However, until the count of 4-bit counter 32 reaches 15, it simply counts. When the count of the 4-bit counter 32 reaches 16, that is, the sampling pulse C
When the number of pulses of sampling pulse C5 reaches 24o, the MAX signal C24 of the 4-bit counter becomes 6H'', and then the pattern signal 025 becomes 025 during the 16 pulses of sampling pulse C5.
becomes "L''. At the end of that section, the CY signal C19 of the 4-bit counter 32 loads the 3-bit programmable down counter 33 with the current surface signal C11, and the flip-flop 35 is cleared. and the AND gate 37 is in an open state.The other input of the AND gate 37 is applied with the QM signal of the 4-bit counter 31 through the delay circuit 34, and is inverted every pulse of the sampling pulse C5. A mark signal C23 is obtained.When the value of the 3-bit programmable down counter 33 becomes 0, that is, when the QM signal C17 is counted by the area at that time,
The MiN signal C21 of the 3-bit programmable down counter 33 is generated, and the value of the D input of the flip-flop 36 is set. Therefore, Q signal 022 is "I,"
Then, AND gate 37 is closed. After that, AND until the CY signal C19 of the 4-bit counter 32 is generated.
Gate 37 remains closed. Furthermore, by setting 86 from the surface blanking switch SO, in combination with the output of the 3-bit decoder, any surface can be extinguished.

FIG. 6 is an example of the trajectory of the read scanning laser beam recorded using the above-described surface code generator.

The trajectory MO of surface 0 is sampling pal 7, C3 (7) 16
This is a pattern in which light is periodically extinguished and exposed for 240 cycles, and the locus M1 of one surface is incremented by one because it corresponds to the leftmost two cycles of the 240 cycles. Similarly, patterns for up to six sides are shown below. By recording such a pattern, each surface can be easily identified, and the length of the locus in the section with the same number of sampling pulses can also be easily measured.

Although the present invention has been described above based on one embodiment in which the present invention is applied to a scanner device, the present invention is not limited to this embodiment, and various application examples are possible. For example, the rotating polygon mirror is not limited to four surfaces, but may have any number of surfaces. Further, the period of the recording pattern for jitter adjustment may be any period. Furthermore, it goes without saying that the present invention can be applied not only to reading/scanning devices but also to scanning/recording devices.

By applying the present invention to an image scanning device, particularly a plane scanning type facsimile or scanner device that uses a rotating polygon mirror to scan an original image, jitter caused by optical non-uniformity between each surface of the rotating polygon mirror can be reduced. Correction is performed to obtain a distortion-free horizontal image. Also, at this time, correction values can be easily set.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the mechanical and optical parts of a scanner device to which the present invention is applied, FIG. 2 is a block diagram showing an electric circuit for jitter correction according to the present invention, and FIG. 3 is a diagram showing the locus of the reading scanning laser beam. FIG. 4 is a block diagram showing the electrical circuit of the area code generator in FIG. 2, FIG. 6 is a diagram showing the operation timing of the area code generator in FIG. 4, and FIG. FIG. 3 is a diagram showing a correction value measurement pattern that has been obtained. 1... Laser light source, 2... Laser modulator, 3
...Reflecting mirror, 4...Rotating polygon mirror, 6
...Main scanning motor, 6...Encoder,
7...Fθ lens, 8...Flat reflecting mirror, 9...Scanning start point sensor, 1Q...Scanning end point sensor, 11...Glass fiber , 12
... Photomultiplier tube, 13 ... Manuscript, 21.
...Reference plane sampling frequency calculator, 22...
... Area sampling frequency calculator, 23 ... Sampling pulse generator, 24 ... Image signal sampling circuit, 26 ... Image signal buffer memory,
26... Correction constant writer, 27...
Correction constant storage unit, 28... surface correction constant switch,
29... Area signal generator, 30... Area code generator, 31.32... 4-bit counter, 33... 3-bit programmable down. Counter, 34...Delay circuit, 36ζ...Flip/70 tube, 36...3 bit Tecoder,
37...mu ND gate, 5o-8s...plane blanking switch. Name of agent: Patent attorney Toshio Nakao (1st person)
Figure 3 Figure j ZJ-1111118-335-

Claims (3)

[Claims] (1) Recognize each surface of the rotating polygon mirror, add the recognition code for each surface of the rotating polygon mirror to the scanning trajectory, drive the scanning light source for a certain period of time, measure the scanning trajectory length, and use the reference code for the rotating polygon mirror. The ratio of the scanning locus length of each surface to the surface is used as a correction value, the correction value is selected according to the rotation of the rotating polygon mirror, and the scanning frequency is calculated from the target scanning density and the selected correction value,
A jitter correction method characterized by generating a scan timing pulse for an image scanning device. (2) The jitter correction method according to claim 1, in which the scanning light source is driven for a period of time that is an integral multiple of the scanning timing pulse period from the scanning starting point in order to measure the scanning trajectory length of each surface of the rotating polygon mirror. . (3) The jitter correction method according to claim 1, in which a scanning light source is driven for an arbitrary surface of a rotating polygon mirror for scanning locus measurement.