JP2002254698A - Beam measuring device and beam measuring method for multi-beam scanning optical system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device and a method for measuring a scanning beam, which can accurately and reliably offer information on the scanning beam without being affected by a bend of a scanning line and the like in a scanning optical system using a multi-beam. SOLUTION: The beam measuring device for the multi-beam scanning optical system 2 is provided with a charge coupled device(CCD) camera 8 which images the scanning beam 4 applied by the optical system 2 of an image forming device 1, a moving means 10 which moves the CCD camera 8 in parallel within a scanning surface of the optical system 2, a control means 20 which controls the moving means 10, and a beam information obtaining means 21 which offers the information on the scanning beam 4 within the scanning surface according to an image obtained by the CCD camera 8. The beam measuring device measures the scanning beams 4 applied by the optical system 2. The control means 20 performs positioning control of the CCD camera 8 in order to make the scanning beams 4 applied to the CCD camera 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-beam scanning optical system beam measuring apparatus and a multi-beam scanning optical system for measuring a scanning beam in a multi-beam scanning type writing system unit used in a copying machine, a printer product or the like. It relates to a measuring method.

[0002]

2. Description of the Related Art In the measurement of a scanning beam emitted from a writing optical system used in a copying machine or a printer, an apparatus using a combination of a slit and a photosensor or a C
There is an apparatus using a CD camera or an apparatus using a position detecting element and a CCD camera or a photo sensor. In these devices, for example, a light emission timing of a laser diode and an imaging timing of a light receiving device represented by a CCD camera or the like are determined based on a synchronization signal detected by a photodiode or the like, and a beam profile, that is, information on a scanning beam is determined. The method of obtaining has been implemented.

[0003] Further, from this result, the amount of light such as 1/2 or 1 / e ² at the peak is obtained as the diameter of the scanning beam, or the intensity distribution profile is displayed two-dimensionally or three-dimensionally. There is also a method of visually recognizing such information.

For example, in a beam diameter measuring apparatus described in Japanese Patent Application Laid-Open No. 6-34329, a one-dimensional CCD line sensor is used, and the main scanning diameter and the sub-scanning diameter are simultaneously obtained by obliquely arranging them. . However, when measuring the multi-beam scanning optical system, only one of the plurality of scanning beams existing in the sub-scanning direction at one image height can be measured. In addition, a method using a slit and a photodiode as in a laser beam diameter measuring device described in Japanese Patent Application Laid-Open No. 7-103819 has been devised. But one
When measuring multiple beams in which multiple scanning beams are simultaneously irradiated at different heights at two image heights, the individual scanning beams cannot be identified by a photodiode that detects the total amount of light irradiating the light receiving surface. Measurement cannot be performed.

In the case where a two-dimensional CCD camera is used, there is an example in which the scanning beam is irradiated outside the imaging range due to the influence of the bending of the scanning line, and the scanning beam cannot be measured.

In recent years, in order to improve the image forming speed, a multi-beam scanning type writing optical system which uses a plurality of light sources or divides one light source into a plurality of scanning beams has been used. As a result, the printing speed is remarkably improved. However, a complicated configuration and process are also required for the scanning beam measuring device or the geodetic method, and the scanning beam is measured in the conventional one-beam writing unit. There are problems that cannot be handled by the apparatus and the method.

For example, in the case where a plurality of scanning beams are simultaneously incident in the sub-scanning direction at one image height, an apparatus / method using a photodiode for detecting the amount of light in the entire light receiving surface needs to identify the plurality of scanning beams. It is difficult. In addition, when a magnifying optical system is used for high-accuracy measurement, the scanning beam may deviate from the imaging range of the light receiving device due to the bending of the scanning line.

[0008] In addition to solving the above problems, the multi-beam scanning optical system requires a large number of scanning beams to be irradiated in one scan, so that the time required for measurement is long. A beam measuring apparatus and a beam measuring method for a multi-beam scanning optical system are desired.

[0009]

In a laser beam printer, a copying machine, and the like, as well as a higher resolution by reducing the diameter of a scanning beam, a reduction in printing time by improving a writing speed is a major problem. As the latter solution among these problems, a multi-beam scanning optical system using a plurality of beams has been devised and is being put to practical use.

The writing optical system in these image forming apparatuses has a very large effect on the printed image quality, and the performance required of the inspection apparatus for the writing optical system, which is the central part thereof, is increasing year by year. One of the items that need to be measured is to obtain a scanning beam accurately and with high accuracy over the entire scanning surface. The scanning beam diameter and the uniformity of the pitch between the scanning beams, the scanning line bending due to the tilt of the rotating polygon mirror, etc., especially the scanning line bending is about several tens of μm, whereas the scanning line bending is only a few. These factors are as large as 100 μm, which are factors that greatly affect the image quality, and it is considered essential to measure the irradiation position of the scanning beam with high accuracy in the entire scanning area.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and a multi-beam scanning optical system beam measuring apparatus and a multi-beam scanning optical system capable of measuring a plurality of scanning beams in a multi-beam scanning optical system. The present invention provides a system beam measurement method.

[0012]

According to the present invention, there is provided a beam measuring apparatus for a multi-beam scanning optical system, comprising: an imaging unit for imaging a dot array of a scanning beam emitted by a multi-beam scanning optical system of an image forming apparatus; Moving means for moving the scanning beam in the main scanning direction within the scanning plane of the multi-beam scanning optical system; controlling means for controlling the moving means so that a dot array of the scanning beam is picked up by the image pickup means; Based on the image obtained by the means,
A beam information acquisition unit for acquiring information on the scanning beam; a multi-beam scanning optical system beam measuring device for measuring the plurality of scanning beams irradiated in the sub-scanning direction by the multi-beam scanning optical system; However, the apparatus is characterized in that the imaging means is moved in the sub-scanning direction within the scanning plane of the multi-beam scanning optical system. With this configuration, it is possible to reliably measure the beam irrespective of the influence of scanning line bending or the like.

Further, in the multi-beam scanning optical system beam measuring apparatus according to the present invention, the number of dots in the sub-scanning direction of the scanning beam is acquired by the beam information acquiring unit as information on the scanning beam, and the imaging unit acquires the information. Storage means for storing the number of dots in the sub-scanning direction of the scanning beam to be imaged, the number of dots in the sub-scanning direction of the scanning beam obtained by the beam information obtaining means, and the number of dots stored by the storage means Comparing means for comparing and calculating the number of dots of the scanning beam in the sub-scanning direction, wherein the control means controls the moving means based on a result calculated by the comparing means. ing. With this configuration, it is possible to determine whether the number of dots of the scanning beam irradiated on the imaging unit is appropriate and move the imaging unit in the sub-scanning direction until the desired number of dots is reached, so that the scanning beam can be reliably measured. Becomes

Further, in the multi-beam scanning optical system beam measuring apparatus according to the present invention, the control means causes the moving means to move the imaging means in the main scanning direction within the scanning plane of the multi-beam scanning optical system. Then, the multi-beam scanning optical system is moved in the sub-scanning direction within the scanning plane. With this configuration, the process of sequentially moving to each measurement point in the scanning direction and positioning so that all the scanning beams are irradiated within the imaging range of the imaging unit is repeated, so that the scanning beam information is reliably acquired in the entire scanning area. It became possible.

Further, the beam measuring apparatus of the multi-beam scanning optical system according to the present invention, by receiving a range larger than the imaging range of the imaging means in the sub-scanning direction in the scanning plane of the multi-beam scanning optical system, A multi-beam scanning optical system includes a light detection unit that detects a position of a dot of the scanning beam that is irradiated in a plurality of sub-scanning directions,
The moving means moves the light detecting means in advance of the imaging means in the scanning plane of the multi-beam scanning optical system, and the control means controls the number of dots of the scanning beam detected by the light detecting means. The moving means is configured to move the imaging means simultaneously in the main scanning direction and the sub-scanning direction within the scanning plane of the multi-beam scanning optical system based on the position. With this configuration, in the measurement of the scanning beam in the entire scanning plane of the multi-beam scanning optical system, the beam position to be measured next is detected in advance by using the light detection means, and the beam is moved to the measurement point and also moved in the sub scanning direction. By doing so, it is possible to measure the scanning beam of the entire area in a shorter time.

Further, in the multi-beam scanning optical beam measuring apparatus according to the present invention, the control means controls the moving means based on an average position of dots of the scanning beam detected by the light detection means. Is provided. With this configuration, the position of the imaging unit is determined based on the average position of the plurality of scanning beams detected by the light detection unit in the sub-scanning direction, so that the scanning beams in the entire scanning plane can be measured without being affected by the scanning line bending. Becomes possible.

Further, the beam measuring device of the multi-beam scanning optical system according to the present invention has a configuration in which the light detecting means is a position detecting element. With this configuration, the position of the scanning beam to be measured next can be detected in a short time without performing image calculation by using the position detection element, and the measurement time can be reduced.

Further, in the multi-beam scanning optical system beam measuring apparatus according to the present invention, the beam information acquiring means may determine an irradiation position of the scanning beam within an imaging range of the imaging means and a movement amount of the imaging means. And acquiring an irradiation position of the scanning beam in the scanning plane as information on the scanning beam based on the scanning beam.
With this configuration, it is possible to calculate the absolute position at which the scanning beam is irradiated by further adding the moving distance of the imaging unit to the scanning beam irradiation position acquired within the imaging range of the imaging unit.

Further, according to the beam measuring method of the present invention, there is provided an image forming step for picking up an image of a dot array of a scanning beam irradiated by a multi-beam scanning optical system of an image forming apparatus; A moving step of moving an imaging position in the imaging step in a main scanning direction and a sub-scanning direction within a scanning plane of the multi-beam scanning optical system so that the image is captured in the imaging step; and an image acquired in the imaging step. Based on the, comprising a beam information acquisition step of acquiring information on the scanning beam, using a method characterized in that the multi-beam scanning optical system measures a plurality of the scanning beam irradiated in the sub-scanning direction I have. By positioning the relative position of the imaging means and the multi-beam scanning optical system in the sub-scanning direction so that the scanning beam is irradiated by this method, it is possible to reliably measure the scanning beam irrespective of the influence of scanning line bending and the like. Become.

Further, in the beam measuring method for a multi-beam scanning optical system according to the present invention, in the moving step, after moving an imaging position in the imaging step in a main scanning direction within a scanning plane of the multi-beam scanning optical system, A method is used in which the multi-beam scanning optical system is moved in the sub-scanning direction within the scanning plane. According to this method, the process of sequentially moving to each measurement point in the scanning direction and positioning so that all the scanning beams are irradiated within the imaging range of the imaging unit is repeated, and the scanning beam information can be reliably acquired in the entire scanning plane. It becomes possible.

Further, the beam measuring method of the multi-beam scanning optical system according to the present invention is characterized in that, in the sub-scanning direction in the scanning plane of the multi-beam scanning optical system, a range larger than the imaging range in the imaging step is received. A light detecting step of detecting a plurality of positions of the dots of the scanning beam irradiated in the sub-scanning direction by a multi-beam scanning optical system; and in the moving step, a light receiving position in the light detecting step is determined by the multi-beam scanning optical system. The multi-beam scanning optical system moves the imaging position in the imaging step based on a position of a dot of the scanning beam detected in the light detection step while moving the imaging position in the imaging plane prior to the imaging position in the imaging step. Using a method characterized by simultaneously moving the main scanning direction and the sub-scanning direction within the scanning plane of That. By this method, the time required for positioning the imaging means in the entire scanning plane can be reduced,
The scanning beam can be measured in a shorter time.

Further, in the beam measuring method for a multi-beam scanning optical system according to the present invention, in the beam information acquiring step, the irradiation position of the scanning beam within the imaging range in the imaging step and the movement of the imaging position in the imaging step A method is used in which an irradiation position of the scanning beam in the scanning plane is obtained as information on the scanning beam based on the amount. By this method, the absolute position at which the scanning beam is irradiated can be acquired, and information such as the beam diameter, the light amount, the irradiation position, the scanning line bending, and the like of an arbitrary scanning beam in the entire scanning plane can be acquired.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. (1st Embodiment)

FIG. 1 is a diagram showing a multi-beam scanning optical system beam measuring apparatus according to a first embodiment of the present invention.

In FIG. 1, a plurality of scanning beams 4 emitted from a laser diode group 3 as a multi-beam scanning optical system 2 of the image forming apparatus 1 are condensed on a mirror surface on a rotating polygon mirror 5. Then, the focused scanning beam 4 is
By the mirror surface of the rotating polygon mirror 5 rotating at high speed, the light passes through the lens group 6 and is scanned and exposed along the axial direction of the surface of the photosensitive drum (not shown).

The multi-beam scanning optical system beam measuring apparatus according to the present embodiment captures an image of the scanning beam 4 radiated by the multi-beam scanning optical system 2 and captures an image based on a signal output from the synchronization detecting photodiode 7. The CCD camera 8 is provided as a two-dimensional area type imaging means for synchronizing the timing and controlling the position. The CCD camera 8 is provided so as to move along the axial direction of a photosensitive drum (not shown). ing.

The CCD camera 8 is provided in a moving means 10 capable of moving the CCD camera 8 in the main scanning direction and the sub-scanning direction of the scanning beam 4, and a driving motor 11 is attached to the moving means 10, When the drive motor 11 is driven, the CCD camera 8 can move in the main scanning direction and the sub-scanning direction of the scanning beam 4. A control means 20 for controlling the moving means 10 is attached to the drive motor 11 so that the dot array of the scanning beam 4 is imaged by the CCD camera 8, and by controlling the drive motor 11, the CCD camera 8 Positioning control is performed in the main scanning direction and the sub-scanning direction.

The CCD camera 8 is a CCD camera 8
Is connected to beam information acquisition means 21 for acquiring information on the scanning beam 4 based on the image acquired by the CCD camera 8.
Are sequentially read out as signals, and the beam information acquiring means 2
1 is output.

The beam information acquisition means 21 is based on the image of the scanning beam 4 captured by the CCD camera 8, the number of beams, the beam diameter, the amount of light, the beam irradiation position within the imaging range of the CCD camera 8, the distance between each beam, and the like. Of the scanning beam 4 is calculated.

The control means 20 is connected with a photodiode 7 for synchronization detection. The photodiode 7 for synchronization detection outputs a predetermined signal to the control means 20 so as to correspond to the surface of a photosensitive drum (not shown). This is for synchronizing the imaging timing of the CCD camera 8 disposed at the position or for controlling the positioning of the CCD camera 8.

The operation of the multi-beam scanning optical system beam measuring apparatus according to this embodiment will be described below.

The scanning beam 4 emitted from the laser diode group 3 is focused on the mirror surface of the rotary polygon mirror 5. Then, the condensed scanning beam 4 passes through a lens group 6 so as to form an image on the surface of a photosensitive drum (not shown) by a mirror surface of a rotating polygon mirror 5 rotating at a high speed, and is moved in the axial direction of the photosensitive drum. Are scanned and exposed along. And scanning beam 4
Represents a C disposed at a position corresponding to the surface of the photosensitive drum.
It is detected by the CD camera 8.

The CCD camera 8 is attached to a moving means 10 which can move the scanning beam 4 in the main scanning direction and the sub-scanning direction. The movement in the sub-scanning direction is performed by the moving means 10 as shown in FIG. This is performed by moving the Z stage 10a, which is provided and is movable in the sub-scanning direction, in the sub-scanning direction. The Z stage 10a can move the CCD camera 8 in the sub-scanning direction by being driven by the drive motor 11.

In the moving step of moving the scanning beam of the multi-beam scanning optical system 2 in the main scanning direction and the sub-scanning direction, the CCD camera 8 is moved to a position where the scanning beam 4 is irradiated. An imaging step of imaging a dot row of the scanning beam 4 emitted from the optical system 2 is performed. Then, based on the image acquired in the imaging step, information such as the beam diameter, beam position, and beam distance of the scanning beam 4 is acquired in a beam information acquisition step of acquiring information on the scanning beam 4. Although the CCD camera 8 is moved in the sub-scanning direction in the moving step here, the scanning beam 4 may be irradiated on the CCD camera 8 by moving the multi-beam scanning optical system 2 in the sub-scanning direction. Good.

According to the above-described configuration, when measuring the dots 4a of the scanning beam 4 having the scanning line curve as shown in FIG. 3 using the two-dimensional area type CCD camera 8, particularly high precision measurement is performed. When using a magnifying optical system to perform
The dots 4a of the scanning beam 4 irradiated onto the imaging range 8a of the CD camera 8 are only a part of the scanning beam 4 to be measured. However, since the CCD camera 8 can be moved in the sub-scanning direction, scanning is performed. The dots 4a of the scanning beam 4 can be measured corresponding to the scanning line bending of the dots 4a of the beam 4. Note that the present invention is not limited to the measurement of the scanning beam 4 emitted from the multi-beam scanning optical system 2 of the image forming apparatus 1 such as a copying machine or a printer. Can be applied. (2nd Embodiment)

FIG. 4 is a diagram showing a multi-beam scanning optical system beam measuring apparatus according to a second embodiment of the present invention.

The multi-beam scanning optical system beam measuring apparatus according to the present embodiment has the configuration of the first embodiment, and further includes the number of dots 4a in the sub-scanning direction of the scanning beam 4 acquired by the beam information acquiring means 21, and Dots 4a in the sub-scanning direction of the scanning beam 4 to be imaged by the CCD camera 8
The comparison means 22 for comparing and calculating the number of dots 4a in the sub-scanning direction of the scanning beam 4 stored by the storage means 23 for storing the number of the scanning beams 4 is connected to the beam information acquisition means 21. Means 23 is connected.

The storage means 23 stores the laser diode group 3
The number of the scanning beams 4 in the sub-scanning direction which is output in the step S1 is input and stored in advance.

The comparing means 22 calculates the difference between the number of scanning beams 4 in the sub-scanning direction stored in the storage means 23 in advance and the number of scanning beams 4 obtained by the beam information obtaining means 21 at an arbitrary measurement point. The CCD camera 8 is moved in the sub-scanning direction via the control means 20 according to the value calculated by the comparison means 22.

Next, the operation will be described. FIG. 5 is a flowchart of the multi-beam scanning optical system beam measuring method according to the present embodiment. First, the CCD camera 8 is positioned in the main scanning direction (step S101). Next, the number of dots 4a of the scanning beam 4 irradiating the CCD camera 8 at that position is acquired by image processing called labeling (step S102).

The number of desired dots 4a in the sub-scanning direction of the scanning beam 4 to be imaged by the CCD camera 8, and beam information acquisition for acquiring information on the scanning beam 4 based on the image acquired by the CCD camera 8. Comparing the difference in the number of dots 4a obtained by the means 2
2, a comparison operation is performed (step S103), and the calculation result is substituted for a variable B1 (step S104). B1
= 0, that is, the number of desired dots 4a in the sub-scanning direction of the scanning beam 4 to be imaged by the CCD camera 8, and
Beam information acquisition means 2 for acquiring information on scanning beam 4 based on an image acquired by CCD camera 8
YE if the number of dots 4a obtained by 1 is equal
It becomes S and the positioning is completed. If B1 is not 0, the value of the calculation result B1 in step S103 is temporarily assigned to a variable B2 (step S105).

Next, the moving means 10 is moved by an arbitrary moving amount in one of the sub-scanning directions, whereby the CCD camera 8 is moved.
Is moved (step S106). It should be noted that one direction of the sub-scanning direction is not limited to one direction on one side of the sub-scanning direction, but may be moved in any direction. Then, the number of dots 4a of the scanning beam 4 irradiating the CCD camera 8 at that position is acquired by image processing called labeling (step S107).

The number of desired dots 4a in the sub-scanning direction of the scanning beam 4 to be imaged by the CCD camera 8, and beam information acquisition for acquiring information on the scanning beam 4 based on the image acquired by the CCD camera 8. The comparison means 22 performs a comparison operation on the difference in the number of dots 4a obtained by the means 21 (step S108), and substitutes the calculation result for a variable B1 (step S109).
If B1 = 0, the result is YES and the positioning is completed. B
If 1 = 0, the value of B2 in step S105 is compared with the value of B1 calculated in step S108 (step S110). Transportation means 10
Is moved in the sub-scanning direction in the same direction as the moving direction in step S106 (step S112), and is moved in the opposite direction when the number of scanning beams 4 irradiated onto the CCD camera imaging range 8a is reduced (step S112). ).

Then, the B calculated in step S108
1 is substituted for B2 (step S113), the process returns to step S107 again, and the number of dots 4a of the scanning beam 4 in the sub-scanning direction stored in the storage unit 23 in advance and the beam information at an arbitrary measurement point By repeating this process until the number of dots 4a of the scanning beam 4 acquired by the acquiring means 21 becomes equal, all the scanning beams 4 in the sub-scanning direction are irradiated on the CCD camera 8, and the scanning line Scanning beam 4 without the effect of bending
Can be automatically positioned.

FIG. 6 shows the dots 4a of the scanning beam 4 having a scanning line curve and the imaging range 8a of the CCD camera. For example, as shown in the flowchart of FIG. The scanning beam 4 is moved to each measurement point in the main scanning direction (Step S202), and after the movement is completed, Steps S102 to S1 in FIG. 5 are performed.
14 by the same operation as that of the dot 4 of the scanning beam 4.
a is positioned in the sub-scanning direction so that “a” irradiates the imaging range 8a of the CCD camera (steps S203 to
215), by repeating the measurement at all the measurement points (step S216), it becomes possible to measure the irradiation position, beam diameter, light amount, etc. of the scanning beam 4 in the entire scanning plane of the scanning beam 4. (Third embodiment)

FIG. 8 is a view showing a multi-beam scanning optical system beam measuring apparatus according to a third embodiment of the present invention.

As shown in FIG. 8, the multi-beam scanning optical system beam measuring apparatus of the present embodiment includes a photodiode array 30 as a light detecting means for detecting the scanning beam 4 in addition to the configuration of the second embodiment.

The photodiode array 30 is mounted on the CCD camera 8 and is moved by the moving means 10 in the scanning plane of the multi-beam scanning optical system 2 so as to precede the CCD camera 8. It has a light receiving surface and has a light receiving range in the sub-scanning direction that is larger than the CCD camera imaging range 8a.

The photodiode array 30 is connected to the beam information acquisition means 21, and is used in a photodetection step for detecting the positions of the dots 4 a of the scanning beam 4 irradiated in the sub-scanning direction by the multi-beam scanning optical system 2. The beam information acquisition unit 21 acquires the position information of the scanning beam 4 detected by 30, and drives the drive motor 11 via the control unit 20 based on the acquired position information to control the positioning of the CCD camera 8. .

According to the above configuration, the control means 20 controls the CCD camera 8 within the scanning plane of the multi-beam scanning optical system 2 based on the position of the dot 4a of the scanning beam 4 detected by the light detecting means 30. By linearly complementarily moving the moving means 10 so as to move the distance L1 in the main scanning direction and also the distance L2 in the sub-scanning direction, there is no time loss at the time of moving to the next measurement point. The scanning beam 4 can be measured in a short time. That is, there is no need to move in two steps, that is, movement to each measurement point in the main scanning direction and positioning in the sub-scanning direction, and thus the measurement time can be reduced.

In the positioning control of the CCD camera 8 in the sub-scanning direction, the size L4 of the CCD camera imaging range 8a in the sub-scanning direction is smaller than the distance L3 between the uppermost and lowermost dots of the scanning beam 4 in the sub-scanning direction. If it is sufficiently large, as shown in FIG. 9, the beam information acquisition unit 21 determines the average irradiation position of the plurality of scanning beams 4 in the sub-scanning direction, that is, the average position of the dots 4a of the scanning beam 4 detected by the light detection unit 30. Positioning control of the relative position of the CCD camera 8 and the multi-beam scanning optical system 2 calculated by image calculation or the like so that the calculated average irradiation position of the scanning beam 4 passes near the center of the CCD camera imaging range 8a in the sub-scanning direction. To do it.

According to the above-described configuration, all of the plurality of scanning beams 4 are irradiated on the imaging range 8a of the CCD camera in the sub-scanning direction, and all the scanning beams 4 can be measured. (Fourth embodiment)

FIG. 10 is a view showing a multi-beam scanning optical system beam measuring apparatus according to a fourth embodiment of the present invention. The multi-beam scanning optical system beam measuring apparatus according to the present embodiment has a third
In this embodiment, the photodiode array 30 as the light detecting means in the embodiment is configured in place of the position detecting element 40.

In FIG. 10, the beam measuring apparatus of the multi-beam scanning optical system has a position detecting element 40. The position detecting element 40 is connected to an analog / digital converting means 54 via a sample / hold means 53. It is connected to the control means 20.

The position detecting element 40 can detect the position of the scanning beam 4 applied to the position detecting element 40 as a voltage value.

The sample-and-hold means 53 has a circuit which samples and holds the voltage input to the analog-to-digital conversion means 54 and keeps the held voltage as it is until the analog-to-digital means 54 completes the conversion.

The analog-to-digital conversion means 54 converts the input signal input from the sample-and-hold means 53,
This is output to the control means 20.

According to the above configuration, the average position of the dots 4a of the scanning beam 4 irradiated in the sub-scanning direction is output as the voltage value V1 proportional to the distance from the center of the position detecting element 40. The output voltage value V1 is output to the analog-to-digital conversion means 54 via the sample-and-hold means 53, and is converted by the analog-to-digital conversion means 54 so that the average irradiation of the dots 4a of the scanning beam 4 irradiated in the sub-scanning direction. The position can be easily obtained, so that C
The positioning of the CD camera 8 in the sub-scanning direction can be performed.

Further, scanning in the scanning plane based on the absolute position coordinates of the dots 4a of the scanning beam 4, that is, the irradiation position of the scanning beam 4 within the imaging range in the imaging step and the movement amount of the imaging position in the imaging step. In order to acquire the irradiation position of the beam 4, for example, as shown in FIG. 11, the irradiation position coordinates of the scanning beam on the CCD camera imaging range 8a whose width in the sub-scanning direction is L5 are (x2, y2), The coordinates of the end of the camera imaging range 8a from the measurement origin are (x1, y
Assuming that 1), the absolute position coordinates of the dot 4a of the scanning beam 4 in the scanning plane are (x1 + x2, y1 + L5-y).
2). By storing information such as the measured scanning beam diameter and light amount together with the coordinate values, it becomes possible to acquire scanning beam information at an arbitrary image height.

[0060]

According to the first aspect of the present invention, even in a scanning optical system using a multi-beam, it is possible to eliminate the influence of scanning line bending and the like, and to reliably measure the scanning beam. In addition, by positioning the scanning beam so as to irradiate the same position, it is possible to reduce the variation due to the irradiation position of the imaging unit.

According to the second aspect of the present invention, in the measurement of a scanning beam at an arbitrary image height, a desired number of scanning beams are irradiated to the image pickup means, and the scanning beam can be measured reliably. Becomes

According to the third aspect of the present invention, in the measurement of the scanning beam, a desired number of the scanning beams are irradiated to the image pickup means, and the sub-scanning is performed without being affected by the scanning line bending in the entire scanning plane. It becomes possible to measure a multi-beam irradiated in a plurality of directions.

According to the fourth aspect of the present invention, the time required for positioning can be reduced, and the scanning beam can be measured in a shorter time.

According to the fifth aspect of the present invention, it is possible to measure the scanning beam in the entire scanning plane in a shorter time.

According to the sixth aspect of the present invention, since the irradiation average position of the scanning beam can be obtained without performing image processing, the positioning of the image pickup means and the measurement of the scanning beam can be performed in fewer steps. Become.

According to the seventh aspect of the present invention, the absolute position at which the scanning beam is irradiated on the scanning plane is calculated, and the beam diameter, the light amount, the beam irradiation position, and the scanning line bending of the scanning beam are calculated over the entire scanning plane. Etc. can be obtained.

According to the eighth aspect of the present invention, even in a multi-beam scanning optical system, it is possible to eliminate the influence of scanning line bending and the like, and to reliably measure a scanning beam. In addition, by positioning the scanning beam so as to irradiate the same position, it is possible to reduce the variation due to the irradiation position of the imaging unit.

According to the ninth aspect of the present invention, it is possible to reliably measure the scanning beam in the entire scanning plane.

According to the tenth aspect, the time required for positioning can be reduced, and the scanning beam can be measured in a shorter time.

According to the eleventh aspect of the present invention, it is possible to calculate the absolute position at which the scanning beam is irradiated, and to obtain the scanning beam information such as the bending of the scanning line in the entire scanning plane.

[Brief description of the drawings]

FIG. 1 is a diagram showing a multi-beam scanning optical system beam measuring apparatus according to a first embodiment of the present invention.

FIG. 2 is a side view of a multi-beam scanning optical system beam measuring apparatus.

FIG. 3 is a view showing a scanning line bending of a scanning beam.

FIG. 4 is a diagram illustrating a multi-beam scanning optical system beam measuring apparatus according to a second embodiment of the present invention.

FIG. 5 is a flowchart of a multi-beam scanning optical system beam measuring method according to a second embodiment of the present invention.

FIG. 6 shows a scanning beam dot and C for measuring the scanning beam.
FIG. 3 is a diagram illustrating an imaging range of a CD camera.

FIG. 7 is a flowchart of a multi-beam scanning optical system beam measuring method according to a second embodiment of the present invention.

FIG. 8 is a diagram showing a multi-beam scanning optical system beam measuring apparatus according to a third embodiment of the present invention.

FIG. 9 is a diagram illustrating a measurement based on an average irradiation position of a scanning beam in a multi-beam scanning optical system beam measuring apparatus according to a third embodiment of the present invention.

FIG. 10 is a diagram showing a multi-beam scanning optical system beam measuring apparatus according to a fourth embodiment of the present invention.

FIG. 11 is a diagram showing absolute position information of a scanning beam.

[Explanation of symbols]

 Reference Signs List 1 image forming apparatus 2 multi-beam scanning optical system 4 scanning beam 4a dot 8 CCD camera (imaging means) 10 moving means 20 control means 21 beam information acquisition means 23 storage means 22 comparison means 8a imaging range 30 photodiode array (light detection means) ) 40 Position detecting element (light detecting means)

Claims (11)

[Claims] 1. An image pickup means for picking up an image of a dot row of a scanning beam emitted by a multi-beam scanning optical system of an image forming apparatus; and moving the image pickup means in a main scanning direction within a scanning plane of the multi-beam scanning optical system. Moving means for controlling; controlling means for controlling the moving means so that the dot array of the scanning beam is imaged by the imaging means; and acquiring information on the scanning beam based on an image acquired by the imaging means. A multi-beam scanning optical system beam measuring device for measuring the plurality of scanning beams irradiated in the sub-scanning direction by the multi-beam scanning optical system, wherein the moving unit includes the imaging unit. A multi-beam scanning optical system which moves in the sub-scanning direction within the scanning plane of the multi-beam scanning optical system. Measuring device. 2. The method according to claim 2, wherein the beam information acquiring unit acquires the number of dots in the sub-scanning direction of the scanning beam as information for the scanning beam, and the dots in the sub-scanning direction of the scanning beam to be imaged by the imaging unit. Storage means for storing the number of dots, the number of dots in the sub-scanning direction of the scanning beam obtained by the beam information obtaining means, and the number of dots in the sub-scanning direction of the scanning beam stored by the storage means 2. The multi-beam scanning optical system beam measuring apparatus according to claim 1, further comprising: a comparing unit configured to control the moving unit based on a result calculated by the comparing unit. 3. 3. The control means moves the imaging means in the main scanning direction within the scanning plane of the multi-beam scanning optical system to the moving means, and then moves the imaging means within the scanning plane of the multi-beam scanning optical system. 3. The multi-beam scanning optical system beam measuring apparatus according to claim 1, wherein the beam is moved in a sub-scanning direction. 4. In the sub-scanning direction in the scanning plane of the multi-beam scanning optical system, a plurality of light beams are irradiated in the sub-scanning direction by the multi-beam scanning optical system by receiving an area larger than the imaging range of the imaging means. Light detecting means for detecting a position of a dot of the scanning beam, wherein the moving means moves the light detecting means prior to the imaging means within a scanning plane of the multi-beam scanning optical system; Means for moving the imaging means in the scanning plane of the multi-beam scanning optical system in the main scanning direction and the sub-scanning direction based on the positions of the dots of the scanning beam detected by the light detection means. The beam measuring device according to claim 1, wherein the beam is moved simultaneously. 5. The apparatus according to claim 4, wherein said control means controls said moving means based on an average position of dots of said scanning beam detected by said light detecting means.
3. The beam measuring apparatus according to claim 1, wherein 6. The beam measuring apparatus according to claim 5, wherein said light detecting means is a position detecting element. 7. The scanning surface as information on the scanning beam based on an irradiation position of the scanning beam within an imaging range of the imaging unit and a moving amount of the imaging unit. The multi-beam scanning optical system beam measuring apparatus according to claim 1, wherein an irradiation position of the scanning beam within the device is acquired. 8. An imaging step for imaging a dot array of a scanning beam irradiated by a multi-beam scanning optical system of an image forming apparatus; and the imaging step so that the dot array of the scanning beam is imaged in the imaging step. Moving the imaging position in the main scanning direction and the sub-scanning direction within the scanning plane of the multi-beam scanning optical system; and a beam for acquiring information on the scanning beam based on the image acquired in the imaging step. An information acquisition step, wherein the multi-beam scanning optical system measures the plurality of scanning beams irradiated in the sub-scanning direction. 9. In the moving step, after the imaging position in the imaging step is moved in the main scanning direction within the scanning plane of the multi-beam scanning optical system, sub-scanning is performed within the scanning plane of the multi-beam scanning optical system. 9. The method according to claim 8, wherein the beam is moved in a direction. 10. In the sub-scanning direction in the scanning plane of the multi-beam scanning optical system, by receiving an area larger than the imaging range in the imaging step, the multi-beam scanning optical system irradiates a plurality of light beams in the sub-scanning direction. A light detecting step of detecting a position of a dot of the scanning beam, wherein in the moving step, a light receiving position in the light detecting step precedes an imaging position in the imaging step in a scanning plane of the multi-beam scanning optical system. And move
Based on the positions of the dots of the scanning beam detected in the light detection step, the imaging position in the imaging step in the main scanning direction and the sub-scanning direction are simultaneously moved within the scanning plane of the multi-beam scanning optical system. The method for measuring a beam of a multi-beam scanning optical system according to claim 8. 11. In the beam information acquiring step, based on an irradiation position of the scanning beam within an imaging range in the imaging step and a moving amount of the imaging position in the imaging step, information on the scanning beam is The method according to claim 8, wherein an irradiation position of the scanning beam in the scanning plane is acquired.