JPH11142235A - Method and apparatus for measurement and evaluation of irregularity in quantity of light of scanning beam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a method and an apparatus in which an irregularity in the quantity of light in the scanning direction of a scanning beam projected from a scanning optical system in an image formation apparatus is measured and evaluated quantitatively as the performance of the scanning optical system. SOLUTION: A moving state 20 is moved on which a photosensor 11 used to receive a scanning beam projected from a scanning optical system, and a quantity-of-light sensor 12, are mounted, by a control box 21 to a direction (a face parallel to a scanning face) perpendicular to the direction of the scanning beam. The number of detections by the photosensor 11 is added up by a counter 24 as the number of scanning operations of a scanning beam L1 projected from a reflecting face 4a by turning a rotating multiple-face mirror 4. The quantity of light of the scanning beam L1 is added up by a host computer 22 on the basis of the output signal of the quantity-of-light sensor 12, so as to be stored on a memory 25. The total quantity of light per rotation of the rotating multiple-face mirror 4 is found and compared under the control of the host computer 22, in a plurality of measuring points corresponding to a plurality of projection directions of the scanning beam.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring a light quantity unevenness in a scanning direction of a scanning beam for measuring the light quantity of a scanning beam in an image forming apparatus such as a laser beam printer or a laser facsimile to evaluate whether or not the design is as designed. The present invention relates to an evaluation method and a measurement evaluation device.

[0002]

2. Description of the Related Art In recent years, an image forming apparatus such as a laser beam printer (LBP) for recording an image by optically scanning a photosensitive drum surface as a recording medium with a laser beam has been widely used.

FIG. 5 is a schematic view of a main part of a scanning optical system used in this type of image forming apparatus. In the figure, a laser beam emitted from a light source means 71 composed of a semiconductor laser or the like is converted into a parallel laser beam by a collimator lens 72, and is condensed by a cylindrical lens 73 having a predetermined refractive index in the sub-scanning direction. The light is incident on a reflection surface (deflection surface) 74a of a polygon mirror (optical deflector made of a polygon mirror) 74. The laser beam reflected and deflected by the reflecting surface 74a of the rotary polygon mirror 74 is projected onto a surface to be scanned, for example, the surface of the photosensitive drum 76 via an imaging lens system (fφ lens) 75. The imaging lens system has a so-called fφ function of making the movement of a point image formed on the drum surface of the laser beam uniform, and correcting image distortion. By rotating the rotary polygon mirror 74 at a constant speed in the direction of arrow A in the figure, the reflection surface for reflecting the laser beam is switched, and the surface to be scanned is repeatedly optically scanned in the direction of arrow B at a constant speed.

[0004] The optical performance of this scanning optical system is evaluated using an evaluation device when assembling it into an image forming apparatus or the like. Conventionally, in this performance evaluation, a scanning beam (scanning light beam) from a scanning optical system is received at a plurality of different positions in a scanning direction, for example, a beam scanning start position, an intermediate position, a scanning end position, and the like, and a direction orthogonal to the scanning direction. , The scanning position, beam diameter, scanning start timing, etc. are measured.

[0005]

However, non-uniform light quantity in the scanning direction of the scanning beam (non-uniform light quantity generated along the scanning direction), which is one of the optical performance evaluations, is not measured without performing image formation. The print density unevenness was visually evaluated by a person by assembling it into a device and actually printing on paper. The evaluation standard was not clear because of the sensory test, and the evaluation variation was large and ambiguous. In addition, since the scanning optical system must be incorporated into the image forming apparatus main body and printed in a completed state as a product, if a defect in light amount unevenness is detected in the printing evaluation, the image forming apparatus main body is disassembled and the scanning optical system is disassembled. It took time and effort to remove the system, resulting in higher costs.

The present invention has been made in view of the above-mentioned unsolved problems, and quantitatively measures the evaluation of unevenness in the light amount in the scanning direction as the performance of a scanning optical system in the same manner as other optical performance evaluations. It is an object of the present invention to provide a method and an apparatus for measuring and evaluating unevenness in the amount of light of a scanning beam, which can be evaluated reliably and in a short time by performing the evaluation.

[0007]

According to the present invention, there is provided a method for measuring and evaluating unevenness in the amount of light of a scanning beam. The method includes the steps of: operating a scanning optical system to be evaluated; and scanning a scanning beam receiving unit for receiving a scanning beam projected by the scanning optical system. The scanning beam receiver is sequentially moved in a direction perpendicular to the center direction, and the scanning beam receiver is temporarily stopped from moving each time the scanning beam receiver reaches a plurality of projection directions of the scanning beam which are determined in advance as measurement points, and one rotation of the rotating polygon mirror. The total light amount of the scanning beam for each is obtained, and the total light amounts obtained for a plurality of measurement points are compared.

Instead of temporarily stopping the scanning beam light receiving unit at a plurality of predetermined measurement points, the light amount measurement may be performed while the scanning beam light receiving unit is continuously moved at a constant speed.

An apparatus for measuring and evaluating unevenness in the amount of light of a scanning beam according to the present invention comprises a scanning optical system mounting section for mounting a scanning optical system to be evaluated, and a scanning beam light receiving section for receiving a scanning beam projected by the scanning optical system to be evaluated. Mounted, a light receiving unit moving stage that moves the scanning beam light receiving unit at a fixed distance from the evaluated scanning optical system and moves in a direction perpendicular to the center direction of the scanning beam,
Control the operation of the scanning optical system to be evaluated and the light receiving unit moving stage, with the rotation of the rotating polygon mirror, accumulate the number of scans of the scanning beam projected from each reflecting surface and measure the light amount of each scanning beam, A control unit is provided for obtaining the total light amount of the scanning beam for one rotation of the rotating polygon mirror, comparing and evaluating the total light amount for each moving measurement point.

The scanning beam receiving section includes a photosensor for counting the number of scans of the scanning beam associated with the rotation of the rotary polygon mirror and determining the timing of light quantity measurement, and a light quantity sensor for measuring the light quantity of the scanning beam according to the timing. May be provided. The light receiving surfaces of the photo sensor and the light amount sensor may have a rectangular shape elongated in a direction perpendicular to the scanning direction of the scanning beam.

[0011]

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a system configuration of an apparatus E1 for measuring and evaluating unevenness in light quantity of a scanning beam in a scanning optical system.
The light amount unevenness measurement and evaluation apparatus E1 includes a scanning optical system mounting section on which a scanning optical system to be evaluated is mounted, and a light receiving section for receiving a scanning beam emitted from the scanning optical system, and a control section includes a moving light receiving section moving stage, and a measuring section. It has a control unit for controlling the evaluation operation.

A laser beam generated from a semiconductor laser 1 of a scanning optical system is collimated by a collimator lens 2 and condensed linearly on a mirror surface 4 a of a rotary polygon mirror 4 by a cylindrical lens 3. Deflection scanning is performed by rotation. The scanning beam L1 is imaged on a virtual scanning plane 6 by an imaging lens system 5 having a spherical lens 5a and a toric lens 5b. This virtual scanning surface corresponds to the surface of the photoconductor of the rotating drum in the image forming apparatus.

The moving stage 20 has a photo sensor 11 and a light amount sensor 12 mounted thereon. The light receiving surfaces of these sensors are set so as to move on the virtual scanning surface 6. FIG. 2 is a diagram of a sensor mounted on the moving stage 20 as viewed from the front. Target scanning line A1 on virtual scanning surface 6
And a photo sensor 11 which is a first detecting means having a long rectangular light receiving surface 11a in a virtual scanning plane (YZ plane) parallel to the Z axis, and a long rectangular light receiving plane in the virtual scanning plane. Light amount sensor 12 as second detection means having light receiving surface 12a
It is shown. These are Y along the target scanning line A1.
It is mounted on a light receiving unit moving stage 20 that is movable in the axial direction.

The light receiving surface 11a of the photo sensor 11 and the light receiving surface 12a of the light amount sensor 12 are long in the Z-axis direction and have a certain width in the Y-axis direction. In particular, the width of the light receiving surface 12a of the light amount sensor in the Y-axis direction changes depending on the resolution setting for light amount unevenness detection. Since the purpose of evaluating the unevenness in the light amount of the scanning optical system is particularly to detect dust, dirt, scratches, distortion, etc. of the imaging lens system 5, a fraction of the scanning beam diameter on the imaging lens system is defined as the resolution. do it. For example, if the scanning beam diameter on the imaging lens is 1 mm, and the width (measurement resolution) of the light receiving surface 12a is about 0.3 mm, the cause of the defect on the imaging lens system can be detected. Further, the scanning beam does not always follow the target scanning line A1, but is scanned, for example, as a curve B1. In such a case as well, it has a long light receiving surface in the Z-axis direction in order to catch the scanning beam, and detects a change in the light amount of the beam.

The control unit includes a control box 21 for controlling the operation of the scanning optical system and the moving stage, a surface number memory 26 for storing the number of reflecting mirror surfaces of the rotary polygon mirror, and a counter for counting the number of scans by switching the reflecting mirror surface. 2
4 and a memory 25 for storing the measured light amount of the scanning beam.
And a host computer that controls the overall operation of the measurement and evaluation device and compares and evaluates the total amount of light per one rotation of the rotating polygon mirror at the measurement position.

The measurement and evaluation of the scanning beam L1 by the measurement and evaluation device E1 are performed as follows. FIG. 3 is a flowchart showing the procedure of measurement evaluation by the measurement evaluation apparatus E1. First, a target scanning optical system is installed at a predetermined position of the measurement evaluation apparatus E1, a semiconductor laser (light source) is made to emit light, and The mirror is rotated to enter a scanning state (step 1). Next, the host computer 2 instructs the control box 21 to move the moving stage 20 in the Y-axis direction.
Are sequentially moved to the measurement points, and the light quantity measurement is started.
The photo sensor 11 is a timing and counting sensor for measurement, and the host computer 22 detects the scanning beam with the photo sensor 11 and then reads out the output signal of the light amount sensor 12 with a certain delay (steps 2 and 3).
3, 4). Then, the light amount of the light amount sensor 12 is stored in the memory 25 in association with the value of the signal of the photo sensor 11 counted by the counter 24, that is, the number of scans (step 5,
6, 7). As a result, the amount of light for each reflecting mirror of the rotating polygon mirror is stored in the memory 25. The host computer 22 reads out the stored light amount for each reflecting mirror surface from the number of surfaces 26 and adds the light amount for the number of reflecting mirror surfaces to obtain the total light amount at one measurement point. The host computer 22 stores the value (the number of scans) obtained by the counter 24 in the surface number memory 2.
When the value becomes equal to the value of 6 (step 8), that is, when the rotary polygon mirror 4 makes one rotation, a command is sent to the control box 21 to move the light receiving unit moving stage 20 to the next measurement point (step 9). ). Steps 2 to 9 are repeated until the final measurement point is reached. The light amount of the scanning beam L1 detected in this way is calculated by the host computer 22 for each measurement point (step 10), and the light amount unevenness is evaluated by comparing the values (step 11).

In the above description, the light amount for one rotation of the rotating polygon mirror is obtained for each measurement point, and then the light receiving unit moving stage is sequentially moved to the next measurement point. Alternatively, the same light amount measurement may be performed while moving the moving stage at a constant appropriate speed, and the measured light amount at each measurement point may be obtained.

[0019]

As described above, according to the present invention, the total light amount for one rotation of the polygon mirror is integrated at each measurement point, and the evaluation is performed based on the integrated value. There is an effect that the light amount unevenness of the scanning optical system can be quantitatively evaluated regardless of the light amount variation. Then, based on the result, the position of dust, fluff, etc. in the optical system can be specified, and the defect can be removed by cleaning and replacing on the spot. Therefore, the scanning optical system is incorporated into an image forming apparatus or the like to print and visually inspect. Unlike the above, since the unevenness in the light amount of the scanning optical system can be quantitatively measured and evaluated in a short time, the manufacturing cost of an image forming apparatus or the like using the scanning optical system can be significantly reduced.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a scanning beam light amount unevenness measurement evaluation apparatus.

FIG. 2 is a diagram showing a light receiving surface of the measurement and evaluation device of FIG.

FIG. 3 is a flowchart showing a procedure for measuring and evaluating unevenness in light amount of a scanning beam by the apparatus of FIG. 1;

FIG. 4 is a diagram showing an addition relationship between a light amount reading timing and a light amount.

FIG. 5 is an explanatory diagram of a scanning optical system of the image forming apparatus.

[Explanation of symbols]

 1, 71 Laser beam 2, 72 Collimator lens 3, 73 Cylindrical lens 4, 74 Rotating polygon mirror 4a, 74a Reflecting mirror surface (deflection surface) 5a Spherical lens 5b Toric lens 5, 75 Imaging lens system 6 Virtual scanning surface 76 Photoconductor Drum 11 Photo sensor 12 Light intensity sensor 11a, 12a Light receiving surface 20 Moving stage 21 Control box 22 Host computer 24 Counter 25 Memory 26 Surface number memory

Claims (5)

[Claims] 1. A scanning optical system for projecting a scanning beam which repeatedly moves in a fixed direction by rotation of a rotary polygon mirror, and measures and evaluates a scanning beam unevenness in a scanning direction due to a change in a scanning direction of the scanning beam. In the evaluation method, the scanning optical system to be evaluated is operated, and a scanning beam receiving unit that receives a scanning beam projected by the scanning optical system is sequentially moved in a direction perpendicular to a center direction of the scanning beam. Each time the unit reaches a plurality of projection directions of the scanning beam that is determined in advance as a measurement point, the movement of the scanning beam light receiving unit is temporarily stopped, and the total light amount of the scanning beam per rotation of the rotating polygon mirror is obtained, and the plurality of measurement points are determined. A method for measuring and evaluating unevenness in the amount of light of a scanning beam, wherein the total amount of light obtained for each is compared. 2. The method according to claim 1, wherein instead of temporarily stopping the scanning beam light receiving unit at the plurality of measurement points that can be run in advance, the light amount is measured while the scanning beam light receiving unit is continuously moved at a constant speed. Scanning beam light amount unevenness measurement evaluation method described in the above. 3. A scanning light beam non-uniformity measurement for measuring and evaluating a scanning beam non-uniform light amount unevenness due to a change in a scanning direction of a scanning beam of a scanning optical system for projecting a scanning beam repeatedly moving in a fixed direction by rotation of a rotary polygon mirror. An evaluation apparatus, comprising: a scanning optical system mounting unit that mounts a scanning optical system to be evaluated; and a scanning beam light receiving unit that receives a scanning beam projected by the scanning optical system, and the light receiving unit is fixed from the scanning optical system. And a light receiving unit moving stage that moves in a direction perpendicular to the center direction of the scanning beam, and controls the operations of the scanning optical system and the light receiving unit moving stage, with the rotation of the rotating polygon mirror, Integrates the number of scans of the scanning beam projected from each reflecting surface, measures the amount of light of each scanning beam, obtains the total amount of scanning beam for one rotation of the rotating polygon mirror, and moves the measurement. An apparatus for measuring and evaluating unevenness in the amount of light of a scanning beam, comprising a control unit for comparing and evaluating the total amount of light for each point. 4. The scanning beam receiving section counts the number of scannings of the scanning beam associated with the rotation of the rotary polygon mirror, and determines a timing of light quantity measurement, and detects a light quantity of the scanning beam according to the timing. The light amount unevenness measurement and evaluation device according to claim 3, further comprising a light amount sensor for measuring. 5. The light amount unevenness measurement and evaluation apparatus according to claim 4, wherein the light receiving surfaces of the photosensor and the light amount sensor are rectangular in a direction elongated in a direction perpendicular to the scanning direction of the scanning beam.