JP3526375B2 - Light spot interval detecting method / scanning line pitch setting method / light spot interval detecting device / scanning line pitch setting device and multi-beam scanning device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light spot interval detection method, a scanning line pitch setting method, a light spot interval detection device, a scanning line pitch setting device, and a multi-beam scanning device.

[0002]

2. Description of the Related Art An optical scanning device which deflects a light beam whose intensity is modulated by an image signal and scans a surface to be scanned for image formation is widely used in connection with image forming devices such as digital copying machines and various optical printers. Are known. Recently, a "multi-beam scanning device" has been proposed which simultaneously scans a plurality of scanning lines at the same time in order to increase the scanning speed.

One of the important points to note in a multi-beam scanning device is that the scanning line pitch that determines the recording density in the sub-scanning direction must be set accurately. This is because if the scanning line pitch is not accurate, the pixel density of the written recorded image periodically fluctuates in the sub-scanning direction, degrading the image quality of the recorded image.

Recently, a multi-beam scanning device capable of switching the scanning line pitch between two or more recording densities (for example, between 400 dpi and 600 dpi) is also intended,
In such an apparatus, accurate setting of the scanning line pitch is required for any recording density.

As a method of adjusting the change of the scanning line pitch, a light source section having a plurality of light sources can be rotated so that the arrangement direction of a plurality of light spots on the surface to be scanned can be rotated by the rotation of the light source section. When the light spot spacing is D, the angle α formed by the arrangement direction and the main scanning direction is
It is intended to adjust the rotational position of the light source unit so as to satisfy P = D · sin α with respect to the desired scanning line pitch: P.

This method is effective in setting the scanning pitch, but in order to accurately adjust and set the scanning line pitch, the light spot interval D must be known accurately. The light spot interval: D is determined by the relative positional relationship between the light sources in the light source unit, the imaging magnification of the optical system between the light source unit and the surface to be scanned, and the like.

The image-forming magnification and the like of the optical system between the light source section and the surface to be scanned often differ subtly due to a slight assembly error when assembling the optical system to each multi-beam scanning device. However, even if the assembling adjustment is performed as designed, it is conceivable that the imaging magnification may change with time due to the influence of vibration and the like accompanying the actual use of the multi-beam scanning device.

Further, the relative positional relationship among the plurality of light sources in the light source section is not limited to that of a monolithic structure such as an LD (semiconductor laser) array, but in a light source section in which a plurality of independent semiconductor lasers are combined, It is conceivable that an assembly error for each part and a change with time are considered, and even in a monolithic LD array, the interval of the light emitting parts is different for each individual. For this reason, in the above method in which the arrangement direction of the light spots is changed by the rotation of the light source unit to change and adjust the scanning line pitch, "the interval between the light spots must be accurately detected".

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to realize a light spot interval detecting method capable of surely detecting the light spot interval. Another object of the present invention is to realize a scanning line pitch setting method capable of accurately setting the scanning line pitch by using the above-described light spot interval detection method.

Another object of the present invention is to realize an optical spot interval detecting device for implementing the above scanning line pitch detecting method.

Still another object of the present invention is to realize a scanning line pitch setting device for carrying out the above scanning line pitch setting method.

Still another object of the present invention is to realize a multi-beam scanning device having the above-mentioned light spot interval detecting device or scanning line pitch setting device.

[0013]

According to a method of detecting a light spot interval of the present invention, in a multi-beam scanning device capable of rotating the arrangement direction of a plurality of light spots on a surface to be scanned by rotating a light source unit, A method for detecting the interval between two light spots ", which is characterized by the following points (claim 1).

That is, a single light-receiving element provided outside the scanning area and having a light-receiving surface length capable of commonly detecting a plurality of light spots in the scanning orthogonal direction is used, and light is received by two light spots whose intervals are to be detected. The surface is scanned at a predetermined scanning speed: v, a rectangular signal is obtained based on the output of the light receiving element, and the step of detecting the signal interval time: t of the rectangular signal corresponding to each light spot is rotated. By repeating this, the maximum value of signal interval time: t: t _max is obtained, and the light spot interval is obtained as v · t _max from this maximum value: t _max and scanning speed: v.

As the "light source part", a monolithic LD array having two or more light emitting parts or a combination of a plurality of semiconductor lasers and a plurality of LEDs can be used. The single light receiving element arranged outside the scanning region may be provided outside the region on the beam scanning start side or outside the region on the beam scanning end side for the purpose of detecting the light spot interval. When this light receiving element is provided on the beam scanning start side, it may be "also used for synchronous light detection".

The maximum number of light spots formed at one time on the surface to be scanned is equal to the number of light sources (light emitting portions) included in the light source portion. When the number of light sources is three or more, the light spot interval to be detected may be the light spot interval corresponding to any two light sources adjacent to each other, or any two of the three or more light sources may be used. It may be an interval between two light spots formed on the surface to be scanned when the light is turned on. When three or more light spots can be formed on the surface to be scanned, they do not necessarily have to be arranged on one straight line.

The number of light sources (light emitting units) included in the light source unit may be three or more as described above, but may be two (Claim 2). In this case, the multi-beam scanning is "two-beam scanning". Become.

According to the scanning line pitch setting method of the present invention, in a multi-beam scanning device capable of rotating the arrangement direction of a plurality of light spots on a surface to be scanned by rotating a light source section, a plurality of light spots are simultaneously scanned. Method for adjusting the pitch of the scanning lines, which has the following features (claim 3).

When the light spot interval: v · t _max is detected by the method according to claim 1 or 2, the position of the light source unit is defined as the "home position with respect to the rotation of the light source unit", and the desired scanning to be adjusted. Line pitch: For d, d = v · t
An angle θ that satisfies _max · sin θ is obtained, and the light source unit is rotated in the predetermined direction by the angle θ, so that the scanning line pitch is set to a desired scanning line pitch d.

Here, the "scan line pitch" is 2 when the light spot interval is detected by the method of the present invention.
This means the interval between scanning lines scanned by each light spot when scanning is performed with one light spot at the same time, and is equal to the pixel width in the sub-scanning direction determined by the recording density or an integral multiple of this pixel width.

"Optical spot interval detector" of the present invention
Is a device for carrying out the light spot detection method according to claim 1, that is, "a multi-beam scanning device capable of rotating the arrangement direction of a plurality of light spots on the surface to be scanned by rotating the light source section. , A device for detecting the distance between two light spots, which comprises rotating means,
It has a single light receiving element and a control / arithmetic means (claim 4).

The "rotating means" is means for rotating the light source section, and can be suitably constructed by a stepping motor having an appropriate step pitch as a drive source and a rotation transmitting mechanism for transmitting the rotation to the light source section.

The "single light receiving element" is provided outside the scanning region and has a light receiving surface length in the scanning orthogonal direction that can commonly detect a plurality of light spots. Considering ideally deflected multiple light beams, at the position where these ideal light beams cross the light receiving surface of the light receiving element, the direction in which the deflected light beam moves is defined as "scanning direction (corresponding to the main scanning direction on the scanned surface). The direction orthogonal to the scanning direction at the above position is referred to as the "scanning orthogonal direction (corresponding to the sub-scanning direction on the surface to be scanned)". The light receiving surface of the light receiving element "has a length capable of commonly detecting a plurality of light spots in the scanning orthogonal direction"
This means that when the array direction of the two light spots to be detected is the scanning orthogonal direction, the light receiving surface has a length in the scanning orthogonal direction that can receive the two light spots.

The "control / arithmetic means" controls the rotating means while scanning the light receiving surface at a predetermined scanning speed: v with two light spots whose intervals are to be detected, and has a rectangular shape based on the output of the light receiving element. The signal is obtained, and the maximum value of the signal interval time: t of the rectangular signal corresponding to each light spot: t _max is obtained. From this maximum value: t _max and the scanning speed: v, the light spot is defined as v · t _max. It is a means of obtaining a gap.

Also in this light spot interval detecting device,
The number of light sources (light emitting units) in the light source unit may be three or more, but this number can be two (claim 5).

According to the scanning line pitch setting device of the present invention, a "multi-beam scanning device capable of rotating the arrangement direction of a plurality of light spots on a surface to be scanned by rotating a light source section is used to simultaneously scan a plurality of light spots. 5. A device for adjusting the pitch of scanning lines to be performed.
Alternatively, in addition to the structure described in 5, pitch adjusting means is provided (claim 6).

The "pitch adjusting means" is defined in claim 4 or 5.
With the apparatus described, the position of the light source unit when the light spot interval: v · t _max is detected is the home position with respect to the rotation of the light source unit, and d = v with respect to the desired scan line pitch: d to be adjusted. A means for determining an angle satisfying t _max · sin θ: θ, and rotating the light source unit in a predetermined direction by an angle of θ to set the scanning line pitch to a desired scanning line pitch: d.

A multi-beam scanning device according to the present invention is a "multi-beam scanning device capable of rotating the arrangement direction of a plurality of light spots on a surface to be scanned by rotating a light source section". It has the light spot interval detection device described above or the scanning line pitch setting device described in claim 6 (claim 7).

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 2 showing an embodiment of a multi-beam scanning device according to claim 7, two light beams for two-beam scanning are emitted from a “light source part” shown by reference numeral 10.
They are emitted as parallel light beams (claims 2 and 5).
The emitted two light beams pass through the opening of the aperture plate 20 for shaping the light spot and enter the cylinder lens 30,
Sub-scanning corresponding direction (refers to a direction parallel to the sub-scanning direction on a virtual optical path in which the optical path from the light source to the surface to be scanned is linearly developed, and in the main scanning direction on the virtual optical path. The parallel corresponding direction is referred to as the main scanning corresponding direction) and is focused as a long line image in the main scanning corresponding direction in the vicinity of the deflection reflection surface 41 of the polygon mirror 40 which is an optical deflector.

When the polygon mirror 40 rotates at a constant speed in the direction of the arrow, the two light beams reflected by the deflecting / reflecting surface become a deflecting light beam, and the f.theta. The light is focused as two light spots on the scanning surface 50 and scanned. Since a photoconductive photoconductor is usually arranged at the position of the surface to be scanned, the light spot actually scans the photoconductor.

The light source unit 10 has two semiconductor lasers 11 and 12, two collimating lenses 13 and 14 inside a casing 18, and a 1/2 wavelength for rotating the polarization plane of the light beam from the semiconductor laser 11 by 90 degrees. Beam combining prism 1 for combining the light beams from the plate 15 and the semiconductor lasers 11 and 12
6 and a quarter-wave plate 1 for changing the polarization state of the combined two light fluxes to a circular polarization state for “shading correction”
7 and 7 are deployed.

The light beams emitted from the semiconductor lasers 11 and 12 are collimated by the corresponding collimating lenses 13 and 14, and then enter the beam combining prism 16. The light flux from the semiconductor laser 11 is generated by the beam combining prism 16
And is emitted from the beam combining prism 16. The light flux from the semiconductor laser 12 is internally reflected by the inclined surface 161 of the beam combining prism 16, reflected by the polarization beam splitter film 162, and emitted from the beam combining prism 16.

In FIG. 2, the collimating lenses 13 and 1
Both 4 are "in the same plane parallel to the main scanning corresponding direction".
At least one of the semiconductor lasers 11 and 12 is deviated from the optical axis of the corresponding collimator lens by a minute distance in the main / sub scanning corresponding direction. In FIG. 1A, the deviation of the semiconductor laser 12 from the optical axis of the collimator lens 14 in the sub-scanning corresponding direction is “exaggerated”. That is,
Straight line corresponding to the main scanning direction and the fine angular connecting the light emitting portion of the semiconductor laser 11, 12: form a theta _A, square: the slope of theta _A,
The two light beams emitted from the beam combining prism 16 are tilted with respect to each other in the sub-scanning corresponding direction by a slight angle. With this slight angle,
The gap in the sub-scanning direction of the two light spots focused on the scanned surface 50: P _S is determined.

Further, due to the slight deviation of the semiconductor lasers 11 and 12 from the optical axis of the corresponding collimating lens in the main scanning corresponding direction, the light beam emitted from the beam combining prism 16 is as shown in the drawing in the main scanning direction. Form a small angle with each other: θ _B. The angle: θ _B determines the interval P _M between the two light spots focused on the surface to be scanned 50 in the main scanning direction.

By rotating the light source section 10 around the optical axis of the collimating lens 13, the light on the surface 50 to be scanned can be increased by 2.
One remains a gap of the light spot was held constant, it is possible to rotate the direction connecting these spots, by utilizing this fact, the interval: P _S, it is possible to adjust the P _M.

The two light beams emitted from the beam combining prism 16 have their planes of linearly polarized light orthogonal to each other, and if they remain as they are, "shading" occurs due to the difference in reflectance due to the change in the reflection angle of the deflective reflection surface 41. These are made into a circularly polarized state by transmitting them through the four-wave plate 17. In this way, the combined and shading-corrected 2
The light flux is emitted from the light source unit 10.

The polygon mirror 4 is emitted from the light source unit 10.
The two light beams deflected by 0 are deflected toward the scanning region, but enter the mirror 61 through the fθ lens 32 on the way to the scanning region and are reflected by the mirror 61 toward the light receiving element 64. That is, the light receiving element 64 is "a single light receiving element provided outside the scanning area (claims 1 and 4)."
And also serves as a light receiving element for detecting the synchronous light.

The light receiving element 64 is arranged at a position equivalent to the surface to be scanned 50 on the optical path through the mirror 61 (not shown in the figure for the sake of drawing), and the two light beams are received by the light receiving element 64. It is condensed as a light spot on the surface (due to the image forming action of the fθ lens 32).

The light source unit 10 has the above-mentioned rotation mechanism 65 (a rotation mechanism) (composed of a stepping motor and a rotation transmission mechanism (gear, chain, wire, etc.) for transmitting the rotation thereof to the light source unit). Thus, the collimator lens 13 can be rotated around the optical axis. Further, the output of the light receiving element 64 is input to the control calculation section 70 which is a "control / calculation means".

In FIG. 1A, reference numeral 64A indicates a "light receiving surface" of the light receiving element 64. Further, reference characters SP1,
The “light spot” indicated by SP2 moves toward the scanning area by moving as indicated by arrows. The light spot SP1 is due to the light beam emitted from the semiconductor laser 11, and the light spot SP1 is due to the light beam emitted from the semiconductor laser 12. The light receiving surface 64A has a sufficient length in the scanning orthogonal direction (vertical direction in the drawing), and the light spot SP1,
Even when the interval in the scanning orthogonal direction of SP2 is the maximum value: L, these light spots can be reliably received.

For simplicity of explanation, it is assumed that the semiconductor laser 11 has a light emitting portion on the optical axis of the collimator lens 13.
Then, when the light source unit 10 is rotated around the optical axis of the collimator lens 13 by the rotation mechanism 65, the light spot SP
2 rotates around the light spot SP1. The distance L between the light spots SP1 and SP2 is the "light spot interval" and is the detection target. Light spot spacing:
L is expressed as “L if expressed using the intervals: P _S and P _M shown in FIG.
= √ (P _S ² + P _M ² ) ”.

The control calculation section 70 shown in FIG. 2 is as shown in FIG. That is, the control calculation unit 70 includes an MPU (main processor unit) 71 and an image processing unit 73.
And a comparator 74. The MPU 71 controls the image processing unit 73 and also controls the driver 72 (which is a part of the rotation mechanism) that drives the stepping motor M of the rotation mechanism 65 to control the rotation of the stepping motor M. The image processing unit 73 is controlled by the MPU 71 and receives the semiconductor laser 1 via the drivers 81 and 82.
The blinking of 1 and 12 is controlled. The comparator 74 binarizes the output of the light receiving element 64 at an appropriate threshold level and converts it into a rectangular signal, and the signal is processed by the image processing unit 7.
Output to 3. The MPU 71 also controls the rotation of the polygon mirror and the like as a control unit of the entire two-beam scanning device.

Now, the detection of the light spot interval is performed as follows. Semiconductor laser 1 controlled by MPU71
1 and 12 are turned on and the polygon mirror 40 is rotated at a constant speed at a predetermined rotation speed. As a result, the light receiving surface 64A of the light receiving element 64 is scanned by the two light spots SP1 and SP2 at a predetermined scanning speed: v. Each time the two light spots SP1 and SP2 scan the light receiving surface 64A, the signal output from the light receiving element 64 is output to the comparator 7
When binarized by 4, the continuous 2 as shown in FIG.
Since one rectangular signal is obtained, the "signal interval time" is obtained by the time interval: t between the leading edges of these signals.

That is, as shown in FIG. 1C, the output of the light receiving element 64 is sent to the counter 73A as a rectangular signal by the comparator 74, and the counter 73A receives the above-mentioned time by the clock from the clock generator 73B. Count the intervals. The counter 73A and the clock generator 73B
Are both included in the image processing unit 73 shown in FIG.

The result of counting by the counter 73A is MP.
Sampled at U71 with time interval: t. M
The PU 71 drives the stepping motor by one pulse each time sampling is performed, rotates the light source unit 10 by a small angle, and repeats the time interval: t for successive sampling by comparing the previous sampling result with the previous sampling result. , The maximum value: t _max is detected. When the maximum value: t _max is obtained, the “arrangement direction” of the light spots SP1 and SP2 becomes parallel to the scanning direction.

When the maximum value: t _max is obtained, the MPU 71
Performs the calculation: v · t _max to obtain the light spot interval: L, and sets the address of the stepping motor when the maximum value: t _max is obtained.

FIG. 4 is a flow chart showing the above-mentioned procedure when the MPU 71 detects the light spot.

Next, "scan line pitch setting" will be described.
The scanning line pitch is set by using the result of the "light spot interval detection" described above. As shown in the flow chart of FIG. 5, when the scanning line pitch is set, as described above, when the maximum time: t _max is obtained, the arrangement direction of the light spots SP1 and SP2 is "parallel to the scanning direction". Therefore, at this time, the address of the stepping motor is set to set this state as the home position for the rotation of the light source unit 10.

Then, the light spot arrangement direction is tilted by the angle: θ with respect to the light spot interval: L detected as described above (for this purpose, the light source section 10 may be rotated by the angle: θ). ) And the distance between the light spots SP1 and SP2 in the direction orthogonal to the scanning direction is L · sin θ, and therefore the angle: θ at which d = L · sin θ with respect to the target scanning line pitch: d is the rotation angle: θ. As MPU 71 (calculation may be performed or may be calculated based on a table that defines the relationship between sin θ and d / L).

Then, a desired scanning line pitch can be set by controlling the stepping motor M by the MPU 71 so as to realize this rotation angle: θ. Therefore,
In this case, the MPU 71 and the rotating mechanism 65 constitute "pitch adjusting means".

Thus, the two-beam scanning device shown in FIG. 2 is a multi-beam scanning device capable of rotating the arrangement direction of a plurality of light spots on the surface to be scanned 50 by rotating the light source section 10. It has a space | interval detection apparatus and a scanning line pitch setting apparatus (Claim 7).

[0052]

As described above, according to the present invention, a novel light spot interval detecting method and device can be realized. According to this light spot interval detection method and device,
The light spot interval can be detected accurately. According to the present invention, it is also possible to realize a new scanning line pitch setting method and apparatus. According to this scanning line pitch setting method and apparatus,
A desired scanning line pitch can be set easily and accurately. Further, according to the present invention, a novel multi-beam scanning device can be realized. According to this multi-beam scanning device,
Since the light spot interval can be detected with high accuracy, good multi-beam scanning can be realized by accurately setting the scanning line pitch based on this.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a light spot interval detection method of the present invention.

FIG. 2 is a diagram for explaining a two-beam scanning device which is one embodiment of the multi-beam scanning device of the present invention.

FIG. 3 is a diagram for explaining a control calculation unit in FIG.

FIG. 4 is a flowchart showing a procedure of detecting a light spot interval in the above embodiment.

FIG. 5 is a flowchart showing a procedure for setting a scanning line pitch in the above embodiment.

[Explanation of symbols]

Light receiving surface of 64A light receiving element SP1 light spot SP2 light spot L light spot interval

Claims (7)

(57) [Claims] 1. A method for detecting an interval between two light spots in a multi-beam scanning device capable of rotating an arrangement direction of a plurality of light spots on a surface to be scanned by rotating a light source section, comprising: Use a single light receiving element that is located outside the area and has a light receiving surface length in the scanning orthogonal direction that can commonly detect multiple light spots, and scan the above light receiving surface with two light spots whose intervals should be detected. The process of scanning at speed: v, obtaining a rectangular signal based on the output of the light receiving element, and detecting the signal interval time: t of the rectangular signal corresponding to each light spot is repeated while rotating the light source unit. , The above signal interval time: maximum value of t:
t _max, and from the maximum value: t _max and the scanning speed: v, v · t
_A method for detecting a light spot interval, which is characterized by obtaining a light spot interval as _max . 2. The light spot interval detection method according to claim 1, wherein the light source section has two light sources. 3. In a multi-beam scanning device capable of rotating the arrangement direction of a plurality of light spots on a surface to be scanned by rotating a light source section, the pitch of scanning lines simultaneously scanned by a plurality of light spots is adjusted. The method according to claim 1 or 2, wherein the light spot interval: v · t
_The position of the light source unit when _max is detected is the home position with respect to the rotation of the light source unit, and d = v.
An angle θ that satisfies t _max · sin θ is determined, and the pitch of the scanning lines is set to the desired scanning line pitch d by rotating the light source unit in a predetermined direction by the angle θ.
A method for setting a scanning line pitch, characterized in that 4. A multi-beam scanning device capable of rotating the arrangement direction of a plurality of light spots on a surface to be scanned by rotating a light source part, which is a device for detecting an interval between two light spots. A rotating unit for rotating the unit, a single light receiving element provided outside the scanning region and having a light receiving surface length in the scanning orthogonal direction capable of commonly detecting a plurality of light spots, and an interval while controlling the rotating unit. The light receiving surface is scanned at a predetermined scanning speed: v by two light spots to be detected to obtain a rectangular signal based on the output of the light receiving element, and a rectangular signal signal corresponding to each light spot. A control / calculation means for obtaining the maximum value of the interval time: t: t _max, and obtaining the light spot interval as v · t _max from the maximum value: t _max and the scanning speed: v is characterized. Light spot隔検 detection device. 5. The light spot interval detecting device according to claim 4, wherein the light source unit has two light sources. 6. A pitch of scanning lines simultaneously scanned by a plurality of light spots in a multi-beam scanning device capable of rotating the arrangement direction of a plurality of light spots on a surface to be scanned by rotating a light source section. 6. The device according to claim 4 or 5, wherein the light spot interval is v · t.
_The position of the light source unit when _max is detected is the home position with respect to the rotation of the light source unit, and an angle θ that satisfies d = v · t _max · sin θ with respect to the desired scanning line pitch to be adjusted: d And a pitch adjusting means for setting the pitch of the scanning lines to the desired scanning line pitch: d by rotating the light source unit in a predetermined direction by the angle: θ. apparatus. 7. A multi-beam scanning device capable of rotating the arrangement direction of a plurality of light spots on a surface to be scanned by rotating a light source section, wherein the light spot interval detecting device according to claim 4 or 5. A multi-beam scanning device comprising the scanning line pitch setting device according to claim 6.