JP2007033364A - Apparatus for measuring scanning laser beam diameter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To measure beam diameters in a main scanning direction and a sub-scanning direction of a scanning laser beam at main scanning positions of the number greater than the number of pairs of sensors. <P>SOLUTION: By moving an X stage 15 in the main scanning direction X, three pairs of sensors consisting of slitted pin photo diodes 17a, 17b and 17c and CCD line sensors 18a, 18b and 18c provided on the X stage 15 at predetermined intervals also move to arbitrary positions in the scanning direction X. Thus, the beam diameters in the main scanning direction and the sub-scanning direction of the scanning laser beam can be measured at main scanning positions of the number greater than the number of the pairs of sensors. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a scanning laser beam diameter measuring apparatus, and more particularly to a scanning laser beam diameter measuring apparatus used for adjustment of a laser printer optical system and a bar code scanner optical system utilizing scanning (scanning) of a laser beam.

For example, in a laser printer, a laser beam from a laser light source is reflected by a polygon mirror (polyhedral mirror) and scanned on a photosensitive drum, and an electrostatic latent image is formed on the surface of the photosensitive drum to record information. ing. In the barcode scanner, the laser beam from the laser light source is reflected by a polygon mirror and scanned on the barcode label, and the reflected light is detected to read the barcode.

As an example of a conventional scanning laser beam diameter measuring apparatus used when assembling and adjusting the optical system of such a laser printer or barcode scanner, the scanning laser beam is perpendicular to the main scanning direction. A plurality of sensor pairs comprising a slit photoelectric conversion element having an elongated slit and a CCD line sensor in which a large number of charge-coupled elements are arranged in the sub-scanning direction. And measuring the beam diameter in the sub-scanning direction based on the output signal of the CCD line sensor is known (see Patent Document 1).
JP-A-5-157624

However, in the above-described prior art, a plurality of sensor pairs are fixedly arranged at predetermined intervals in the main scanning direction. Therefore, the main scanning direction and sub-scanning direction beams of the scanning laser beam at a plurality of predetermined positions are provided. Only the diameter can be measured, and there has been a problem that the beam diameter at other positions can only be inferred from the measured beam diameters at a plurality of predetermined positions.

In the prior art, since a plurality of sensor pairs are fixedly arranged at predetermined intervals in the scanning direction, the scanning laser beam power differs at a plurality of main scanning positions. There is a problem that the beam diameters in the main scanning direction and the sub-scanning direction cannot be measured.

Therefore, an object of the present invention is to attach a plurality of sensor pairs to a moving member that can move in the main scanning direction, and to scan the main scanning direction and sub-scanning beams of the scanning laser beam at a number of main scanning positions larger than the number of sensor pairs. An object of the present invention is to provide a scanning laser beam diameter measuring apparatus capable of measuring a diameter.

Another object of the present invention is to provide a scanning laser beam diameter measuring device that modulates the scanning laser beam power at the position of a sensor pair consisting of a photoelectric conversion element with slit and a CCD line sensor to adjust the light output. It is to provide.

Means for Solving the Problems and Effects of the Invention

The scanning laser beam diameter measuring apparatus according to claim 1 includes a photoelectric conversion element with a slit having a long and narrow slit in the sub-scanning direction perpendicular to the main scanning direction of the scanning laser beam, and a large number of charge-coupled elements in the sub-scanning direction. A plurality of sensor pairs each including an arrayed CCD line sensor are provided, and the beam diameter in the main scanning direction is measured by the output signal of the photoelectric conversion element with slit, and the beam diameter in the sub-scanning direction is determined by the output signal of the CCD line sensor. In the scanning laser beam diameter measuring apparatus for measuring, the sensor pair is mounted on a movable member movable in the scanning direction, and the laser beam diameters in the main scanning direction and the sub-scanning direction are measured at more scanning positions than the number of sensor pairs. It is characterized by being measurable. According to the scanning laser beam diameter measuring apparatus of claim 1, the position of the plurality of sensor pairs can be moved to an arbitrary position by moving the moving member to an arbitrary position in the main scanning direction. It becomes possible to measure the beam diameter of the scanning laser beam in the main scanning direction and the sub-scanning direction at a number of main scanning positions larger than the number of pairs.

The scanning laser beam diameter measuring apparatus according to claim 2 is the scanning laser beam diameter measuring apparatus according to claim 1, wherein the scanning laser beam power is determined by the position of the photoelectric conversion element with slit of the sensor pair and the position of the CCD line sensor. The optical output is adjusted by applying modulation. According to the scanning laser beam diameter measuring apparatus according to claim 2, the slit laser beam power is modulated by adjusting the scanning laser beam power at the position of the photoelectric conversion element with slit and the position of the CCD line sensor, thereby adjusting the slit. The difference between the photosensitivity of the attached photoelectric conversion element and the photosensitivity of the CCD line sensor can be adjusted.

A scanning laser beam diameter measuring apparatus according to a third aspect is the scanning laser beam diameter measuring apparatus according to the first or second aspect, wherein the scanning laser beam power is reduced for the photoelectric conversion element with a slit located at the center side in the main scanning direction. For the photoelectric conversion element with slits located near both ends, the scanning laser beam power is increased, and for the CCD line sensor located near the center in the main scanning direction, the scanning laser beam power is reduced and located near both ends. The CCD line sensor is characterized in that it is adjusted to increase the scanning laser beam power. According to the scanning laser beam diameter measuring apparatus of the third aspect, the light output is reduced for the photoelectric conversion element with the slit located at the center side, and the light output is increased for the photoelectric conversion element with the slit located near both ends. In addition, since the light output is reduced for the CCD line sensor located at the center side and the light output is increased for the CCD line sensor located near both ends, the mirror surface of the polygon mirror of the laser beam from the laser light source It is possible to compensate for the change in the scanning laser beam power accompanying the change in the reflectance of the laser beam, which varies depending on the incident angle with respect to and the incident angle of the scanning laser beam on the fθ lens.

According to a fourth aspect of the present invention, in the scanning laser beam diameter measuring apparatus according to any one of the first to third aspects, the fθ lens unit is mounted on a movable member that can move in the sub-scanning direction, and the thickness of the fθ lens is increased. The beam diameter of the scanning laser beam in the main scanning direction and the sub-scanning direction can be measured over the entire range of directions. According to the third aspect of the invention, since the fθ lens is mounted on the moving member that can move in the sub-scanning direction, the entire range in the thickness direction of the fθ lens can be obtained by moving the moving member in the sub-scanning direction. The beam diameter of the scanning laser beam in the main scanning direction and the sub-scanning direction can be measured.

The object of measuring the beam diameter of the scanning laser beam in the main scanning direction and the sub-scanning direction at a number of main scanning positions larger than the number of sensor pairs is achieved by providing the sensor unit with an X stage.

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

FIGS. 1A and 1B are a plan view and a side view showing a configuration of a scanning laser beam diameter measuring apparatus according to Embodiment 1 of the present invention. The scanning laser beam diameter measuring apparatus according to the first embodiment includes a laser light source unit 1, a scanner unit 2, an fθ lens unit 3, a sensor unit 4, and a table 5 on which these components are placed. It is configured.

The laser light source unit 1 includes a laser light source 10 including a laser diode that emits a laser beam, and a coupling lens 11 that narrows the laser light emitted from the laser light source 10 into a spot-like laser beam.

The scanner unit 2 includes a polygon mirror 12 that reflects and scans a spot-like laser beam from the laser light source unit 1, and a scanner main body 12A that includes an electric motor (not shown) that rotates the polygon mirror 12. ing.

The polygon mirror 12 is formed in a pentagonal plate shape, and its peripheral surface is mirror-finished. The polygon mirror 12 is pivotally attached to a rotating shaft of an electric motor (not shown) disposed in the scanner body 12A. The polygon mirror 12 scans the laser beam incident from the laser light source unit 1 as a scanning laser beam m as the mirror surface rotates. In the first embodiment, the polygon mirror 12 has a pentagonal plate shape. However, the number of mirror surfaces of the polygon mirror 12 is not limited to five, and may be other numbers such as 6, 8, 12, 16, and the like. There may be.

As shown in an enlarged view in FIG. 2, the fθ lens unit 3 can move the fθ lens 13 used to keep the scanning speed of the scanning laser beam m constant and the fθ lens 13 in the vertical direction (Y direction). It is comprised from the Y stage 14 to mount. By rotating the knurling 14 a provided on the Y stage 14, the mounted fθ lens 13 can be moved to an arbitrary position in the vertical direction, so that the main scanning of the scanning laser beam m is performed over the entire range in the thickness direction of the fθ lens 13. It becomes possible to measure the beam diameter in the direction and the sub-scanning direction.

As shown in FIGS. 3A and 3B, the sensor unit 4 includes an X stage 15, a start sensor 16, pin photodiodes 17a, 17b, and 17c with slits, and CCD line sensors 18a, 18b, and 18c. It consists of three sensor pairs.

The X stage 15 is a stage that is moved in the main scanning direction (X direction) of the scanning laser beam m by a stepping motor, a linear motor, or the like (not shown).

The start sensor 16 is a photodiode fixedly disposed on the mounting member 16A, and is disposed at one end of a range (scanning width) scanned by the scanning laser beam m, detects the start of scanning, and starts a signal S1 (FIG. 5) is output.

As shown in an enlarged view in FIG. 4, the pinned photodiodes 17a, 17b, and 17c with slits have elongated slits in the sub-scanning direction (Y direction) perpendicular to the main scanning direction (X direction) of the scanning laser beam m. The slit width of each of the pinned photodiodes 17a, 17b, 17c with slits is sufficiently narrower than the beam diameter of the scanning laser beam m in the main scanning direction. The pin photodiodes 17a, 17b, and 17c with slits are attached to the X stage 15 at a predetermined interval.

Similarly, as enlarged in FIG. 4, the CCD line sensors 18a, 18b, 18c have a large number of charge couplings in the sub-scanning direction (Y direction) perpendicular to the main scanning direction (X direction) of the scanning laser beam m. It is a charge coupled device array in which devices are arranged, and is attached to the X stage 15 in proximity to the pin photodiodes 17a, 17b, 17c with slits. The height of the light receiving surfaces of the CCD line sensors 18a, 18b, and 18c and the height of the light receiving surfaces of the pin photodiodes 17a, 17b, and 17c with slits coincide with each other.

Referring to FIG. 5, the circuit system of the scanning laser beam diameter measuring apparatus according to the first embodiment includes an MPU (Micro Processing Unit) 21, an LD (Laser Diode) drive 22, an X stage drive 23, and a TIA (Time). An Interval Analyzer) 24, an AMP (AMPlifier) 25, a CCD (Charge Coupled Device) drive / AMP 26, and an A / D (Analog / Digital) conversion circuit 27 are included.

The MPU 21 includes a CPU (Central Processing Unit) (not shown), a ROM (Read Only Memory) for storing programs, a RAM (Random Access Memory) to which work areas and various counters are assigned, an I / O (Input / Output), and the like. . In the MPU 21, CCD 1 pixel clock cycle information and scanning time information are set in advance.

The LD drive 22 drives the laser light source 10 according to a control signal from the MPU 21.

The X stage drive 23 drives the X stage 15 by a control signal from the MPU 21.

The TIA 24 receives the start signal S1 from the start sensor 16 and the output signals S2, S3, and S4 from the three pinned photodiodes 17a, 17b, and 17c, and outputs a timing signal to the MPU 21.

The AMP 25 receives and amplifies output signals S2, S3, and S4 from the three slit pin photodiodes 17a, 17b, and 17c, performs analog / digital conversion by the A / D conversion circuit 27, and outputs them to the MPU 21.

The CCD drive / AMP 26 receives and amplifies the output signals S5, S6, S7 from the three CCD line sensors 18a, 18b, 18c, performs analog / digital conversion by the A / D conversion circuit 27, and outputs them to the MPU 21. The drive clock signals S8, S9, S10 are output to the CCD line sensors 18a, 18b, 18c for driving.

The CCD line sensors 18a, 18b and 18c are operated by CCD drive signals S8, S9 and S10 from the CCD drive / AMP 26, and CCD drive signals S8, S9 and S10 from the CCD drive / AMP 26. Is a start signal S1 generated when the start sensor 16 detects the scanning laser beam m.
Cleared in response to.

As shown in FIG. 6, the MPU 21 has a peak value P1 of the waveform A obtained by the output signals S2, S3, S4 from the pin photodiodes 17a, 17b, 17c with slits. 13.5% of the peak value P1, that is, 1 / e ² Is calculated as the beam diameter in the main scanning direction, and the time width t1 at a position 13.5% of the peak value P1 is calculated. Is multiplied by the scanning speed (mm / sec) to calculate the beam diameter of the scanning laser beam m in the main scanning direction.

Similarly, as shown in FIG. 6, the MPU 21 detects the peak value P2 of the waveform B obtained by the output signals S5, S6, S7 of the CCD line sensors 18a, 18b, 18c, and the peak value P2 Is calculated as the beam diameter in the sub-scanning direction. Here, since the waveform B obtained from the CCD line sensors 18a, 18b, and 18c is stepped, the time width t2 at the position of 13.5% of the peak value P2. Causes an error of ± t0. T0 Is the clock period of one pixel.

Therefore, as shown in FIG. 7, the MPU 21 calculates the beam diameter in the sub-scanning direction after correcting the waveform B ′ connecting the midpoints of the staircase waveform B. The peak value P2 ′ of the corrected waveform B ′ is a stepped waveform P2. Will be slightly larger. Then, the peak value P2 of the corrected waveform B ′ A value of 13.5% of 'is calculated as the beam diameter in the sub-scanning direction. That is, the time width of the value of 13.5% of the peak value P2 ′ is set to t2. 'Then beam diameter = t2 '/ T0 × 1 pixel pitch.

The MPU 21 displays the beam diameter in the main scanning direction and the beam diameter in the sub-scanning direction thus calculated on a display device (not shown).

By the way, when the scanning of the scanning laser beam m is repeated by the polygon mirror 12 and the fθ lens 13, the start signal S1 is sent from the start sensor 16 to the MPU 21 at the timing shown in FIG. And the output signals S2, S3, and S4 are sequentially input from the pin photodiodes 17a, 17b, and 17c with slits at the timing as shown in FIG. However, the output signals S5, S6, and S7 from the CCD line sensors 18a, 18b, and 18c are randomly input at a timing as shown in FIGS. 8 (c), (d), and (e). Therefore, the MPU 21 combines the output signals S5, S6, and S7 from the CCD line sensors 18a, 18b, and 18c so as to be sequentially arranged to obtain the waveform shown in FIG.

As shown in FIG. 9, the MPU 21 adjusts the laser beam power of the laser light source 10 through the LD drive 22 at the positions of the pin photodiodes 17a, 17b, 17c with slits and the positions of the CCD line sensors 18a, 18b, 18c. Modulation is applied to adjust the light output. The reason for this adjustment is that the light sensitivity of the slit photodiodes 17a, 17b, and 17c and the light sensitivity of the CCD line sensors 18a, 18b, and 18c are different. This is to adjust the difference.

Further, the MPU 21 reduces the light output for the pinned photodiode 17b with the slit located at the center through the LD drive 22 and increases the light output for the pinned photodiodes 17a and 17c with the slit on the left and right. Similarly, the MPU 21 reduces the light output of the CCD line sensor 18b located at the center through the LD drive 22 and increases the light output of the CCD line sensors 18a and 18c located on the left and right. The reason for this adjustment is that the reflectivity of the laser beam varies depending on the angle of incidence of the laser beam from the laser light source 10 on the mirror surface of the polygon mirror 12 and the angle of incidence of the scanning laser beam m on the fθ lens 13. Because.

Next, the operation of the scanning laser beam diameter measuring apparatus according to the first embodiment configured as described above will be described with reference to the flowcharts shown in FIGS.

In the optical output modulation initial setting process, the MPU 21 turns on the scanner unit 2 (S101 in FIG. 5), turns on the laser light source 10 (S102 in FIG. 10), and outputs signals from the pin photodiodes 17a, 17b, and 17c with slits. S2, S3 and S4 are measured (S103 in FIG. 10). Next, the MPU 21 calculates the difference between the output signals S2, S3, and S4 between the slit photodiodes 17a, 17b, and 17c (S104 in FIG. 10). Next, the MPU 21 measures output signals S5, S6 and S7 of the CCD line sensors 18a, 18b and 18c (S105 in FIG. 10), and the MPU 21 outputs signals S5 and S6 between the CCD line sensors 18a, 18b and 18c. , S7 is calculated (S106 in FIG. 10). The MPU 21 outputs the laser light source 10 so that the output signals S2, S3, S4 of the pinned photodiodes 17a, 17b, 17c with slits and the output signals S5, S6, S7 of the CCD line sensors 18a, 18b, 18c are constant. Is modulated (S107 in FIG. 10).

In the beam measurement process, the MPU 21 turns on the scanner unit 2 (S201 in FIG. 11) and turns on the laser light source 10 (light output modulation) (S202 in FIG. 11). Next, the MPU 21 moves the X stage 15 to the sensor position 1 (see FIG. 3A) (S203 in FIG. 11), and measures the beam diameter of the scanning laser beam m in the main scanning direction and the sub-scanning direction ( S204 in FIG. 11).

Specifically, in the beam diameter calculation process in the main scanning direction, the MPU 21 samples the A / D conversion data of the output signals S2, S3, and S4 of the pinned photodiodes 17a, 17b, and 17c with slits (S301 in FIG. 12). The peak value P1 is searched (S302 in FIG. 12), and 13.5% of the peak value P1 is calculated (S303 in FIG. 12). Next, the MPU 21 calculates the time width t1 at the 13.5% position (S304 in FIG. 12), and calculates the time width t1 at the 13.5% position × scanning speed = the beam diameter in the main scanning direction (FIG. 12). S305).

In the sub-scanning direction beam diameter calculation process, the MPU 21 reads the output signals S5, S6, and S7 of the CCD line sensors 18a, 18b, and 18c (S401 in FIG. 13) and obtains them from the output signals S5, S6, and S7. After the waveform B is corrected to the waveform B ′, the peak value P2 ′ of the corrected waveform B ′ is searched (S402 in FIG. 13), and 13.5% of the peak value P2 ′ is calculated (S403 in FIG. 13). Next, the MPU 21 calculates the pixel position of 13.5% (S404 in FIG. 13), the time width t2 ′ of the pixel position of 13.5% and the clock period t0 of one pixel. And the number of pixels (= t2 '/ T0) is calculated, and the number of pixels × pixel pitch = beam diameter in the sub-scanning direction is calculated (S405 in FIG. 13).

Subsequently, the MPU 21 moves the X stage 15 to the sensor position 2 (see FIG. 3B) (S205 in FIG. 11), and measures the beam diameter of the scanning laser beam m in the main scanning direction and the sub-scanning direction ( S206 of FIG. 11). Note that the measurement of the beam diameter of the scanning laser beam m in the main scanning direction and the sub-scanning direction has already been described in detail and will be omitted.

Finally, the MPU 21 turns off the scanner unit 2 (S207 in FIG. 11) and turns off the laser light source 10 (S208 in FIG. 11).

The MPU 21 calculates the scanning speed from the timing shift of the output signals S2, S3, S4 of the pinned photodiodes 17a, 17b, 17c and the scanning time, and calculates P−P (peak · peak) with respect to the average value of the scanning speed. The ratio of jitter can be calculated from (two peaks). Further, the MPU 21 repeatedly takes in the output signals S5, S6, S7 from the CCD line sensors 18a, 18b, 18c, thereby detecting a shift in the peak value of the scanning laser beam m on each mirror surface of the polygon mirror 12 and making it cumbersome. This can be measured.

Thus, the scanning speed and jitter can be measured by using the three pinned photodiodes 17a, 17b, and 17c with slits, and the surface tilt can also be measured by using the three CCD line sensors 18a, 18b, and 18c. Thus, comprehensive evaluation of the fθ lens unit 3 becomes possible, and practicality can be improved.

By the way, by the series of operations described above, the beam diameters of the scanning laser beam m in the main scanning direction and the sub-scanning direction when the scanning laser beam m passes through a fixed position in the thickness direction of the fθ lens 13 are measured. I was able to. Thereafter, when measuring the beam diameters in the main scanning direction and the sub-scanning direction when the scanning laser beam m passes through different positions in the thickness direction of the fθ lens 13, the knurl 14 a provided on the Y stage 14 is turned. As a result, the fθ lens 13 is moved to an arbitrary position in the vertical direction (sub-scanning direction Y), and then the measurement of the beam diameter of the scanning laser beam m in the main scanning direction and the sub-scanning direction is repeated. This makes it possible to measure the beam diameter of the scanning laser beam m in the main scanning direction and the sub-scanning direction over the entire range in the thickness direction of the fθ lens 13.

According to the first embodiment, by moving the X stage 15 to an arbitrary position in the main scanning direction X, the positions of a plurality of sensor pairs can be moved to arbitrary positions. It is possible to measure the beam diameter of the scanning laser beam m in the main scanning direction and the sub-scanning direction at a number of main scanning positions.

Further, according to the first embodiment, the scanning laser beam power is modulated by adjusting the position of the pinned photodiodes 17a, 17b, and 17c with slits and the positions of the CCD line sensors 18a, 18b, and 18c to adjust the light output. Thus, the difference between the photosensitivity of the pin photodiodes 17a, 17b, 17c with slits and the photosensitivity of the CCD line sensors 18a, 18b, 18c can be adjusted.

Further, according to the first embodiment, the light output is decreased for the pinned photodiode 17b with the slit located at the center, and the light output is increased for the pinned photodiodes 17a and 17c located near both ends. At the same time, the CCD line sensor 18b located on the center side reduces the light output, and the CCD line sensors 18a and 18c located near both ends increase the light output. Therefore, the polygon of the laser beam from the laser light source 10 is increased. It is possible to compensate for the change in the scanning laser beam power accompanying the change in the reflectance of the laser beam, which varies depending on the incident angle with respect to the mirror surface of the mirror 12 and the incident angle of the scanning laser beam m on the fθ lens 13.

Furthermore, according to the first embodiment, since the fθ lens 13 is mounted on the Y stage 14 that can move in the sub-scanning direction Y, the Y stage 14 can be arbitrarily moved in the sub-scanning direction Y. Thus, the beam diameters of the scanning laser beam m in the main scanning direction and the sub-scanning direction can be measured over the entire range of the fθ lens 13 in the thickness direction.

As mentioned above, although the Example of this invention was described, these are only illustrations to the last, and this invention is not limited to these, Based on the knowledge of those skilled in the art, unless it deviates from the meaning of a Claim Various changes are possible.

For example, in the first embodiment, three pin photodiodes with slits are arranged, but the present invention is not necessarily limited thereto, and may be two or four or more. Further, when it is not necessary to measure the scanning speed and jitter, one may be used. In the first embodiment, three CCD line sensors are arranged. However, the present invention is not limited to this, and may be one, two, or four or more.

(A) And (b) is the top view and side view which show the structure of the scanning laser beam diameter measuring apparatus which concerns on Example 1 of this invention. FIG. 2 is an enlarged side view of the fθ lens unit in FIG. 1. (A) And (b) is a front view explaining the movement position of the sensor unit in FIG. FIGS. 4A and 4B are an enlarged front view and an enlarged side view of a sensor pair including a pin photodiode with slit and a CCD line sensor in FIG. 3. 1 is a circuit block diagram showing a circuit system of a scanning laser beam diameter measuring apparatus according to a first embodiment. The wave form diagram of the output signal of the pin photodiode with a slit in FIG. 5, and the output signal of a CCD line sensor. The figure for demonstrating the correction process of the output signal waveform of the CCD line sensor in FIG. FIG. 5 is a waveform diagram showing output timings of the output signal of the pin photodiode with slit and the output signal of the CCD line sensor in FIG. 4. FIG. 2 is a light output waveform diagram illustrating adjustment of light output of the laser light source in FIG. 3 is a flowchart showing optical output modulation initial setting processing of the scanning laser beam diameter measuring apparatus according to the first embodiment. 3 is a flowchart showing a beam diameter measurement process of the scanning laser beam diameter measuring apparatus according to the first embodiment. 3 is a flowchart showing a scanning direction beam diameter calculation process of the scanning laser beam diameter measuring apparatus according to the first embodiment. 3 is a flowchart showing sub-scanning direction beam diameter calculation processing of the scanning laser beam diameter measuring apparatus according to the first embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Laser light source unit 2 Scanner unit 3 f (theta) lens unit 4 Sensor unit 5 Table 10 Laser light source 11 Coupling lens 12 Polygon mirror 12A Scanner main body 13 f (theta) lens 14 Y stage (moving member)
15 X stage (moving member)
16 Start sensors 17a, 17b, 17c Pin photodiode with slit (photoelectric conversion element with slit)
18a, 18b, 18c CCD line sensor 21 MPU
22 LD drive 23 X stage drive 24 TIA
25 AMP
26 CCD drive / AMP
27 A / D converter circuit

Claims (4)

A plurality of sensor pairs each including a photoelectric conversion element with slits having elongated slits in the sub-scanning direction perpendicular to the main scanning direction of the scanning laser beam, and a CCD line sensor in which a large number of charge coupled devices are arranged in the sub-scanning direction In the scanning laser beam diameter measuring apparatus for measuring the beam diameter in the main scanning direction by the output signal of the photoelectric conversion element with slit, and measuring the beam diameter in the sub-scanning direction by the output signal of the CCD line sensor,
The sensor pair is mounted on a movable member that can move in the scanning direction, and the laser beam diameters in the main scanning direction and the sub-scanning direction can be measured at more scanning positions than the number of sensor pairs. Scanning laser beam diameter measuring device. 2. The scanning laser beam diameter measuring apparatus according to claim 1, wherein the optical output is adjusted by modulating the scanning laser beam power by the position of the photoelectric conversion element with slit of the sensor pair and the position of the CCD line sensor. The scanning laser beam power is reduced for the photoelectric conversion element with a slit located at the center side in the main scanning direction, and the scanning laser beam power is increased for the photoelectric conversion element with a slit located near both ends, and the center in the main scanning direction. 3. The scanning laser beam diameter measurement according to claim 1, wherein the scanning laser beam power is adjusted to be small for a CCD line sensor located on the side, and the scanning laser beam power is adjusted to be large for a CCD line sensor located near both ends. apparatus. The fθ lens unit is mounted on a movable member movable in the sub-scanning direction, and the beam diameter of the scanning laser beam in the main scanning direction and the sub-scanning direction can be measured over the entire range in the thickness direction of the fθ lens. Item 4. The scanning laser beam diameter measuring apparatus according to any one of Items 1 to 3.

Images