JPH10239210A - Method and device for inspecting lens or mirror - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten the time required for setting and to measure a object to be inspected in wide range and with high precision, relating to inspection of surface precision of a cylindrical lens or a cylindrical mirror. SOLUTION: Relative to a cylindrical mirror (CYM) 21, convergent light beam 10 incident on the CYM 21 is moved relatively in the longitudinal direction of the CYM 21 by a parallel moving stage 15, and the fluctuation in beam diameter of the light beam 10 reflected on the CYM 21 is detected with a beam diameter measurement sensor 17 and a beam diameter/voltage converter 18. By judging difference in beam diameters at a normal part and a rough part on the surface of CYM 21, the surface precision of the CYM 21 is inspected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for inspecting optical components such as lenses and mirrors used in an optical scanning device and the like, and more particularly, to the length of a long optical component such as a cylindrical lens or a cylindrical mirror. The present invention relates to a method and an apparatus for inspecting the flatness of a surface along a direction.

[0002]

2. Description of the Related Art Conventionally, in an optical scanning device or the like that scans a light beam on a surface to be scanned, a cylindrical lens (hereinafter, referred to as CYL) has been used to correct the tilt of the rotary polygon mirror that deflects the light beam. Alternatively, an optical component such as a cylindrical mirror (hereinafter referred to as CYM) is used.

[0003] If the surface of the CYL or CYM has irregularities, the light beam transmitted or reflected by the surface is not normally refracted or reflected, and the accuracy of the scanning device is reduced. I needed to. Conventionally, the surface accuracy of these CYL or CYM has been inspected using an interferometer.

[0004]

However, in an inspection apparatus using an interferometer, there are many adjustment items such as an optical axis, a position, and an inclination of a reference lens and a mirror. There was a problem that it took time. Further, in the case of a horizontally long member such as CYL or CYM, it is desirable to make the measurement range that can be measured by one measurement as large as possible in order to shorten the time required for the inspection. However, in the inspection method using the above interferometer, since the measurement range is a range of about 100 mm in diameter, if the inspection target is longer than this, it is necessary to reset the setting. In the case of a horizontally long member such as CYL or CYM, resetting of the setting takes time, which is not suitable for mass production. In addition, inspection of CYL and CYM usually requires an accuracy of 0.03 μm or less, but the measurement accuracy of an interferometer is limited to about one twentieth of a wavelength, for example, a He-Ne laser having a wavelength of 632.8 nm. When was used, the accuracy limit was about 0.03 μm, and it was difficult to measure with higher accuracy.

The present invention has been made in view of the above-mentioned drawbacks of the method for detecting surface accuracy using an interferometer, and in addition to reducing the time required for setting, a cylindrical lens or a mirror capable of measuring an object to be inspected over a wide area with high accuracy. It is an object of the present invention to provide an inspection method and apparatus.

[0006]

SUMMARY OF THE INVENTION An inspection method and apparatus according to the present invention provides a CYL or CYM with a light beam transmitted through or reflected by the CYL along a longitudinal direction of the CYL or CYM. The surface accuracy of the CYL or CYL is inspected by relatively moving the beam and detecting a change in the beam diameter of the light beam that has passed through the CYL or reflected by the CYL.

Here, to move the light beam relative to CYL or CYM along the longitudinal direction of CYL or CMY means that the light beam incident on CYL or CYL is moved along the longitudinal direction. And any method for that purpose may be used. Specifically, for example, a method in which CYL or CYL is fixed and a light beam is moved along the longitudinal direction while being incident on the CYL or CYL, or vice versa.
A method in which M is fixed and the irradiation position of the light beam is moved along the longitudinal direction, or a method in which both are moved in opposite directions (or at different speeds in the same direction) can be used. Focused light is used as the light beam. Further, the beam diameter of the light beam refers to the diameter of the cross section of the light beam on the optical path.

[0008] The inspection method and apparatus according to the present invention include:
The convergence position of the converging light beam transmitted through or reflected by the CYL fluctuates in the optical axis direction in accordance with the unevenness of the surface of the CYL or CYL, and the fluctuation changes the beam diameter of the converging and diverging light beam. It utilizes the fact that it appears as a change at a predetermined position, and detects the change in the beam diameter to obtain the CYL or CYM.
Inspection of the surface accuracy is performed.

In the above inspection method, it is preferable that the position at which the fluctuation of the beam diameter is detected is a position after or before the light beam passes through the focusing position. Here, the predetermined position after the light beam passes through the focusing position refers to a measurement position defined on an optical path where the light beam travels while diverging after passing through the focusing position. That is, when the beam diameter of the light beam transmitted through the CYL or reflected by the CYM is measured at the focusing position, it is difficult to determine the difference in the beam diameter because the difference in the beam diameter between the normal portion and the uneven portion is small. When the beam diameter is measured at a predetermined position after the light beam has passed through the focusing position, the divergence after passing through the focusing position causes the beam diameter to increase, and the fluctuations are amplified accordingly. It is easy to determine the difference between the beam diameters. Further, even if the measurement position is located before the focusing position, the same effect can be obtained because the beam diameter increases.

The detecting means in the inspection apparatus according to the present invention comprises: a beam diameter measuring means for measuring a beam diameter from a light intensity distribution at a predetermined position of the light beam transmitted through the CYL or reflected by the CYM; It is characterized by comprising a conversion means for converting the beam diameter measured by the detection means into a voltage value, and an output means for visually outputting a change in the voltage value converted by the conversion means. .

Here, the beam diameter measuring means includes:
For example, measuring the light intensity distribution of a beam cross section and expressing this as a pulse waveform ("beam scan")
Can be used. The output means may be any means as long as the change in the beam diameter converted into the voltage value can be output visually. For example, XY recorder, C
An RT display or the like can be used.

[0012]

In the inspection method and apparatus according to the present invention, the CY is detected by detecting a change in the beam diameter of the light beam transmitted through the CYL or reflected by the CYM.
Since the surface accuracy of L or CYM is inspected, it is not necessary to adjust a complicated optical system as in the case of using an interferometer, and the time required for setting can be reduced. For example, the setting can be performed by simply adjusting the CYL or CYM by pressing it against the reference plane. Further, since the light beam is irradiated along the longitudinal direction of CYL or CYM, the surface accuracy can be measured in a wide range without resetting to change the measurement range. For this reason, CYL or CYM
It can sufficiently cope with mass production of such horizontally long members. Furthermore, since the variation of the beam diameter is measured, the measurement accuracy does not depend on the laser wavelength or the like.
Even fine irregularities of 0.03 μm or less can be measured with high accuracy.

[0013] Further, in a system in which the measured fluctuation in the beam diameter is converted into a fluctuation in the voltage value, and the fluctuation in the voltage value is output visually, the fluctuation in the beam diameter is visually recognized. And the state of the surface of CYL or CYM can be visually represented. If the change in the voltage value is input to a data processing device such as a personal computer, information on the measured beam diameter can be output to the personal computer.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a CYL or CYM inspection method and apparatus according to the present invention will be described by using CYL or CYM.
An embodiment in which the present invention is applied to the inspection apparatus will be described.

First, a case where the present invention is applied to a CYM inspection apparatus will be described. FIG. 1 is a schematic configuration diagram of the CYM inspection apparatus 100. The CYM inspection apparatus 100 is roughly divided into a light beam control unit 101 that irradiates the CYM 21 to be inspected with the light beam 10, a movement control unit 102 that moves the CYM 21 in its longitudinal direction, and light reflected by the CYM 21. And a beam diameter measuring unit 103 for measuring the beam diameter of the light beam.

The light beam control unit 101 includes a semiconductor laser light source 11 that generates a light beam 10, a collimator lens 12 that converts the light beam 10 into parallel light, and a focusing device that converts the parallel light beam 10 into focused light. An optical lens 13 and a beam splitter 14 that reflects the focused light beam 10 to the CYM 21 side and transmits the light beam 10 reflected by the CYM 21 to the beam diameter measurement unit 103 side. Here, the position at which the light beam 10 is focused is a predetermined position after the light beam 103 is reflected by the CYM 21 and reaches the beam diameter measurement unit 103.

The movement control unit 102 includes a parallel moving table 15 on which the CYM 21 is mounted, and a CYM 21 on the parallel moving table 15.
And a translation table controller 16 for translating in the longitudinal direction. CY on the translation stage 15
The moving speed of M21 is controlled by the parallel moving table controller 16.

In the parallel moving table 15 of this embodiment, C
Since measurement can be performed simply by setting the YM21 on the reference surface on the table, once the CYM21 is set, there is no need to adjust the optical axis, position, tilt, etc. of the lens and mirror afterwards. Can be shortened.

The beam diameter measuring unit 103 includes a beam diameter measuring sensor 17 and a beam diameter measuring unit 18 for measuring the beam diameter of the light beam 10 reflected by the reflecting surface of the CYM 21 and transmitted through the beam splitter 14, and the measured beam diameter. It comprises a beam diameter / voltage converter 19 for converting a diameter into a voltage value, and an XY recorder 20 for outputting a change in the converted voltage value on recording paper.

The CYM inspection apparatus 1 configured as described above
At 00, a light beam 10 emitted from a semiconductor laser light source 11 is converted into a parallel light by a collimator lens 12, and then becomes a condensed light by a condenser lens 13 to form a beam splitter 1.
4 is incident. The light beam 10 is reflected by the beam splitter 14 toward the CYM 21 to be inspected, and
21 is incident from a direction perpendicular to the longitudinal direction. The CYM 21 installed on the translation table 15 is translated at a constant speed in the longitudinal direction indicated by the arrow, and the light beam 10
Irradiation is continuously performed from one end of the CYM 10 to the other end thereof along the longitudinal direction of the YM 21.

Light beam 1 reflected by the reflecting surface of CYM 21
Numeral 0 passes through the beam splitter 14 and enters the beam diameter measuring sensor 17. The focusing position of the light beam 10 focused by the focusing lens 13 is determined by the beam splitter 14
Is set between the light beam 10 and the beam diameter measuring sensor 17 (the light beam 10 may be focused after reflection or may be focused before reflection). Measure the beam diameter after passing through the focusing position. The cross section of the beam measured by the beam diameter measuring sensor 17 shows a light intensity distribution as shown in FIG. This is represented by a pulse waveform by a commercially available measuring device called “beam scan”. The abscissa in the drawing indicates the distance in the diameter direction of the beam diameter (starting from the left end), and the ordinate indicates the light intensity of the light beam cross section (all units are omitted). In FIG. 2, the length from the rise to the fall of the pulse corresponds to the actual beam diameter, but various methods are available for determining the beam diameter. For example, a pulse width at a position of 13.5% of the pulse height (a position indicated by a broken line in the figure) is measured as the beam diameter D. The beam diameter measured by the beam diameter measuring device 18 is converted into a voltage value by a beam diameter / voltage converter 19 and then input to an XY recorder 20. In the XY recorder 20, the change in the converted voltage value is output on recording paper. This change in the voltage value is an enlarged graph of the change in surface properties of the CYM 10 in the longitudinal direction.

Next, the fluctuation of the beam diameter due to the unevenness of the surface of the CYM 21 will be described in detail.

FIGS. 3A and 3B are explanatory views showing the optical path of the light beam reflected on the surface of the CYM 21. FIG. 3A is an explanatory view showing the optical path of the light beam reflected on a normal portion on the CYM 21. And (b) shows the optical path of the light beam reflected by the minute concave portion 22 on the CYM 21. In the figure, the arrow z indicates the traveling direction of the light beam, and the arrow x indicates the moving direction of the CYM 21. Here, (a)
Is referred to as 10a, and the light beam of (b) is referred to as 10b.

As shown in FIG. 3A, the light beam 10a reflected on the normal portion of the CYM 21 converges at a convergence position A, and thereafter proceeds while diverging at a constant rate in the traveling direction. . If the surface accuracy on the CYM 21 is uniform in the longitudinal direction, the convergence position is always A when the light beam is continuously irradiated along the longitudinal direction of the CYM 21. However, actually, since the surface of the CYM 10 has minute irregularities, the convergence position A is shifted back and forth in the z direction. That is, as shown in FIG. 3B, if the light beam 10b is applied to the minute concave portion 22 of the CYM 21, the focusing position of the light beam 10b reflected by the minute concave portion 22 is larger than that of (a). And the light is focused at the focusing position B. As described above, the convergence position is deviated by AB between the case where the light is reflected by the normal portion and the case where the light is reflected by the minute concave portion, so that the beam diameter after passing through the convergence positions A and B is the same beam diameter on the optical path. When measured at the measurement position C, the beam diameters a and b in (a) and (b) are different. That is, the light beam 10b is the light beam 1
Since the beam is focused before 0a, the beam diameter b at the beam diameter measurement position C becomes larger than a. Although not shown in FIG. 3, if there is a minute convex portion on the CYM 21, the focal position of the light beam reflected by the minute convex portion is earlier than the focal position A of (a). The beam diameter at the beam diameter measurement position C becomes smaller than a.

As described above, if the surface of the CYM 21 has irregularities, the convergence position of the light beam 10 varies according to the irregularities, so that the beam diameter at the beam diameter measuring position C also varies. Therefore, a predetermined position after the light beam 10 has passed the focusing position is defined as a beam diameter measurement position C, and the beam diameter at this position is measured, so that the difference in the beam diameter between the normal portion and the uneven portion of the CYM 21 surface is determined. It can be easily determined.

For example, assuming that the size (depth) of the minute concave (or convex) portion is 0.03 μm and the beam diameter of the light beam impinging on the CYM is 5 mm, the radius of curvature R of the minute concave portion is about 10,000 mm. . In this case, R = 100
The difference between the focal position at the time of 00 mm and the focal position at the time of reflection at the normal part is about 4 mm, and the beam diameter is about 15 μm.
m (when the focal length of the condenser lens is 240 mm). Therefore, by measuring the fluctuation of the beam diameter, it is possible to easily determine the difference in the beam diameter between the normal portion and the uneven portion. The shift of the focusing position of 4 mm and the variation of the beam diameter of 15 μm can be changed as appropriate by changing the magnification of the condenser lens 13.

Next, an embodiment in which the inspection method or apparatus according to the present invention is applied to a CYL inspection apparatus will be described.

FIG. 4 is a schematic configuration diagram of the CYL inspection apparatus 110. The functions of each unit constituting the CYL inspection apparatus 110 are the same as those in FIG. 1, and the same parts as those in FIG. However, FIG. 4 omits illustration of the parallel moving table controller 16 and the like shown in FIG.

In FIG. 4, a light beam 10 emitted from a semiconductor laser light source 11 is emitted from a direction orthogonal to the longitudinal direction of a CYL 23 via a collimator lens 12 and a condenser lens 13. C installed on the translation table 15
Since the YL 23 is translated at a constant speed in the longitudinal direction, the light beam 10
Irradiation is continuously performed from one end of the YL 23 to the other end.

The light beam 10 transmitted through the CYL 23 is directly incident on the beam diameter measuring sensor 17. However, the focusing position of the light beam 10 focused by the condenser lens 13 is set between the CYL 23 and the beam diameter measuring sensor 17, and the beam diameter measuring sensor 17 passes the light beam 10 through the focusing position. The measured beam diameter is measured at a predetermined position. In the CYM 21 shown in FIG. 1, the beam diameter of the light beam reflected by one reflecting surface was measured.
The CYL 23 refracts the light beam on the entrance surface and the exit surface of the lens, respectively, so that the total surface accuracy of the two surfaces is inspected.

The CYL inspection apparatus 1 configured as described above
In 10, a light beam 10 emitted from a semiconductor laser light source 11 is converted into parallel light by a collimator lens 12, then becomes condensed light by a condenser lens 13, and becomes C light to be inspected.
The YL 23 is irradiated from a direction orthogonal to the longitudinal direction. Since the CYL 23 installed on the translation table 15 is translated in the longitudinal direction at a constant speed, the light beam 10 is continuously irradiated along the longitudinal direction of the CYL 23.

The light beam 10 transmitted through the CYL 23 is incident on a beam diameter measuring sensor 17, and the beam diameter is measured. The processing after the beam diameter measurement is the same as that in the case of FIG. 1 described above, and the unevenness on the surface of the CYL 23 can be detected as a change in the beam diameter of the light beam 10.

In the above embodiment, the beam diameter is measured at a predetermined position after the light beam has passed the focusing position. However, this may be measured before the focusing position.

In the inspection apparatus of the above embodiment, the measured beam diameter is converted into a voltage value by the beam diameter / voltage converter 19, and the fluctuation of the voltage value is printed out on a recording paper. Therefore, a change in the beam diameter can be visually recognized. Further, if a data processing device such as a personal computer is connected instead of the XY recorder 20 in FIG. 1, the information on the measured beam diameter can be displayed not only on a recording paper but also on a CRT display. Further, the data can be processed as necessary, or can be stored in a storage medium or the like.

The inspection method and apparatus according to the present invention can be applied not only to CYL or CYM but also to any optical component that reflects and refracts. Suitable for large-area lenses, such as large-diameter lenses.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a CYM inspection apparatus according to the present invention.

FIG. 2 is an explanatory diagram showing a light intensity distribution of a light beam.

FIG. 3 is an explanatory view showing the optical path of a light beam reflected by a CYM; FIG. 3A is a light beam reflected by a normal portion on the CYM; FIG. 3B is a light beam reflected by a minute concave portion on the CYM; Show the optical path of

FIG. 4 is a schematic configuration diagram of a CYL inspection apparatus according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Light beam 13 Condensing lens 14 Beam splitter 15 Parallel moving table 17 Beam diameter measuring sensor 18 Beam diameter measuring device 19 Beam diameter / voltage converter 20 XY recorder 21 CYM (cylindrical mirror) 23 CYL (cylindrical lens)

Claims (5)

[Claims] 1. A lens or mirror for applying a light beam transmitted through or reflected by the mirror to a lens or mirror.
By relatively moving along the longitudinal direction of the lens or mirror and detecting a change in beam diameter of the light beam transmitted through the lens or reflected by the mirror,
A lens or mirror inspection method, comprising inspecting the surface accuracy of the lens or mirror. 2. The method according to claim 1, wherein the light beam is a convergent light beam, and the fluctuation of the beam diameter is caused by a convergence position of the light beam transmitted through the lens or reflected by the mirror in accordance with irregularities on the surface of the lens or the mirror. The method for inspecting a lens or a mirror according to claim 1, wherein the method is a fluctuation. 3. The method according to claim 2, wherein the fluctuation of the beam diameter is detected after the light beam has passed through a focusing position or at a predetermined position before the focusing position. . 4. A moving means for relatively moving a lens or a mirror and a light beam along a longitudinal direction of the lens or a mirror, and a beam diameter of a light beam transmitted through the lens or reflected by the mirror. A lens or mirror inspection apparatus, comprising: a detection unit that detects a change, and inspecting the surface accuracy of the lens or the mirror based on the change in the beam diameter detected by the detection unit. 5. A beam diameter measuring means for measuring a beam diameter from a light intensity distribution of a light beam cross section at a predetermined position of a light beam transmitted through the lens or reflected by a mirror, and said beam diameter measuring means. 5. The lens according to claim 4, comprising: a conversion unit for converting the beam diameter measured by the unit into a voltage value; and an output unit for visually outputting a change in the voltage value converted by the conversion unit. Or a mirror inspection device.