JP2007101399A - Height measuring apparatus and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a height measuring technique capable of stably obtaining a high resolution in detection. <P>SOLUTION: A height measuring apparatus for measuring a height of an object to be measured in a prescribed height direction is equipped with an irradiating section, a sensor section and a height detecting section. The irradiating section irradiates a measurement point of the object to be measured at a tilted angle in the height direction with an irradiation beam being made up by arranging a plurality of beams having different wavelengths and no space between them in the height direction. The sensor section receives reflection light from the measurement point of the object to be measured irradiated with the irradiation beam and detects a wavelength of the reflection light. The height detecting section obtains the height of the object to be measured at the measurement point, based on the wavelength of the refection light detected by the sensor section. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a height measuring apparatus and method for measuring height.

Conventionally, a three-dimensional measurement technique using a light cutting method is known (for example, Patent Document 1). In this light cutting method, the slit light is irradiated obliquely with respect to the height detection direction (hereinafter referred to as “height direction”). A projection pattern by the slit light appears on the surface of the object to be measured. This projection pattern shows the light cut surface of the object to be measured, and is deformed according to the surface shape of the object to be measured. Therefore, this projection pattern is detected, and the surface shape of the object to be measured is detected from the deformed shape of the projection pattern.
A technique for simultaneously irradiating a plurality of slit lights is also known in order to expand the measurement range of this light cutting method.
In addition, the phase shift method is a technique for increasing the surface shape detection accuracy by slightly oscillating the slit light or stripe light described above using a piezo element or the like and detecting the brightness change of the projection pattern at this time. It is known.

On the other hand, in Patent Document 2, a plurality of slit lights having different wavelengths are irradiated onto a test object with a sufficient slit interval. By using such slit light, even if some slit light is lost due to the unevenness of the test object, the observation slit light can be reliably identified from the difference in color.
JP 2005-30774 A (Claim 1 etc.) JP-A-5-175310 (FIGS. 2, 3, paragraph 0027, etc.)

  By the way, the above-described phase shift method has a problem that it takes a long time to measure a projection pattern, since the projection pattern must be photographed a plurality of times while the irradiation position of the slit light or the stripe light is displaced.

  Further, when the irradiation light is vibrated with a piezo element, there is a problem that it is difficult to stably improve the surface shape detection accuracy because a mechanical error cannot be avoided.

  Furthermore, in Patent Document 2, it is necessary to provide a sufficient interval between the slit lights so that the observation slit light can be specified even if some of the slit lights are lost. However, this slit light has a problem in that the detection resolution is rough because it becomes impossible to measure at a gap portion.

  In view of the above-described problems, an object of the present invention is to provide a height measurement technique capable of stably obtaining a high detection resolution.

<< 1 >> The height measuring device of the present invention is a height measuring device that measures the height in a predetermined height direction of a test object, and includes an irradiation unit, a sensor unit, and a height detection unit.
An irradiation part irradiates the measurement location of a test object with the irradiation light beam which arranged the several light beam from which a wavelength differs in the height direction without gap at an angle inclined with respect to the height direction.
A sensor part receives the reflected light from the measurement location of the test object by irradiation light beam, and detects the wavelength of reflected light.
A height detection part calculates | requires the height of the test object in a measurement location based on the wavelength of the reflected light detected by the sensor part.
Hereinafter, preferred variations of the present invention will be described.

<< 2 >> The irradiating unit may irradiate light beams having different wavelengths adjacent to each other with overlapping in the height direction. In this case, the height detection unit can determine the height of the test object at the measurement location based on the mixing ratio of the wavelengths of the reflected light detected by the sensor unit.

<< 3 >> The height detection unit can obtain the height by associating the wavelength of the reflected light or the mixing ratio thereof with the wavelength distribution of the irradiated light flux at the measurement location.

<< 4 >> The irradiation unit can include a variable magnification optical system that optically enlarges / reduces the wavelength distribution of the irradiation light beam in the height direction.

<< 5 >> A calibration unit that calibrates the correspondence between the shift amount and the wavelength of reflected light at the measurement location can be provided by relatively shifting the measurement location and the irradiation light beam in the height direction. The height detection unit can obtain the height of the measurement location by collating the wavelength of the reflected light at the measurement location or the mixture ratio thereof with the correspondence calibrated by the calibration unit.

<6> The irradiation unit irradiates each surface of the multi-faced mirror with a plurality of light beams having different wavelengths, and aligns the reflection direction of the light beam group in substantially one direction, thereby causing the plurality of light beams having different wavelengths to be in the height direction It is possible to generate an irradiation light beam connected to the.

<< 7 >> The irradiation unit can generate an irradiation light beam by passing a light beam including a plurality of wavelengths through a wavelength selection element and changing the wavelength in the height direction.

<< 8 >> The height measurement method of the present invention is a method of measuring the height of a test object at a predetermined measurement location, and includes the following steps.
(Irradiation step) An irradiation light beam in which a plurality of light beams having different wavelengths are arranged in the height direction without a gap is irradiated to a measurement point of the test object at an angle inclined with respect to the height direction.
(Detection step) The reflected light from the measurement location of the test object by the irradiated light beam is received, and the wavelength of the reflected light is detected.
(Height measurement step) Based on the wavelength of the reflected light detected in the detection step, the height of the test object at the measurement location is obtained.

  In the present invention, a light beam in which a plurality of light beams having different wavelengths are arranged without gaps in the height direction is used as the light beam at the measurement location. If a gap is provided between light beams having different wavelengths, the reflected light from the test object cannot be obtained in the gap, and a height undetectable part occurs. However, in the present invention, it is possible to eliminate the height undetectable portion by arranging the light beams having different wavelengths without gaps.

<< Description of Overall Configuration of Embodiment >>
FIG. 1 is a diagram showing a height measuring device 11 of the present embodiment.
FIG. 1A shows a conceptual diagram of the height measuring device 11.
FIG. 1B shows a top view of the optical system (12, 30, 33, etc.) of FIG. 1A.
FIG. 1 [C] shows an enlarged view of the measurement point P in FIG. 1 [A].
FIG. 1D shows an image of lattice fringes reflecting the wavelength distribution when the measurement location P (here, solder bump) in FIG. 1C is illuminated by the irradiation light beam L. FIG.

In FIG. 1, a measurement target X (for example, a printed board) is arranged on a stage 20. The stage drive unit 21 can move the stage 20 in the XYZ directions shown in FIG.
The irradiation unit 12 is arranged at a position oblique to the height direction (here, the Z direction shown in FIG. 1) of the measurement target X (for example, a solder bump formed on a printed circuit board). The irradiation unit 12 irradiates the measurement target X with the irradiation light beam L at the irradiation angle θ. The irradiation light beam L at the measurement location P is a light beam in which a plurality of flat light beams having different wavelengths are arranged without gaps along the height direction of the measurement object X (for example, solder bump).

A sensor unit 13 is provided at a position where the measurement point P of the irradiation light beam L is expected. The sensor unit 13 receives the reflected light at the measurement location P and detects the wavelength (or wavelength mixing ratio) of the reflected light. As such a sensor unit 13, a color imaging device (multi-plate type, single-plate type, etc.), a line sensor, or a colorimeter is used.
The height measuring device 11 is provided with a control unit 14. The control unit 14 controls the operations of the irradiation unit 12 and the stage driving unit 21. The control unit 14 also processes the output signal of the sensor unit 13.

<< Configuration 1 of Irradiation Unit 12 >>
FIG. 2 is a diagram illustrating an example of the irradiation unit 12.
The mirror block 30 shown in FIG. 2 is a reflection block in which a plurality of reflection surfaces having different angles are collected, such as 50 degrees, 45 degrees, and 40 degrees. Such a mirror block 30 is formed by applying a single point process to an aluminum material. Around the mirror block 30, a plurality of laser light sources (laser diodes, etc.) 31a to 31f are arranged. The laser beams from these laser light sources 31a to 31f are incident on the reflecting surface of the mirror block 30 as parallel light beams by the waveform shaping optical systems 32a to 32f, are individually reflected by the reflecting surface of the mirror block 30, and have an interval of about 1 mm. Becomes parallel light.

  The waveform shaping optical systems 32a to 32f are preferably configured by arranging a collimator lens, an anamorphic prism pair, a beam expander, and a receiver lens on the emission side of the laser light sources 31a to 31f. In this case, the light beams of the laser light sources 31a to 31f are shaped into a flat light beam by an optical system from the collimator lens to the beam expander, and the flat light beam is condensed on the reflection surface of the mirror block 30 by the receiver lens.

Note that the wavelengths (here, RGB wavelengths) of the laser light sources 31a to 31f are set so that the wavelengths of adjacent lights are different from each other.
The flat light beam collected on the mirror block 30 passes through the cylindrical lens 33 for adjusting the light beam interval. The cylindrical lens 33 condenses the flat luminous flux of each of the laser light sources 31a to 31f on the line with a further increased flatness, and shapes it into an irradiation luminous flux L made up of multiple flat luminous fluxes. The convergence position of the irradiation light beam L is about 150 mm from the mirror block 30. This line-shaped irradiation light beam L is influenced by the aberration effect of the cylindrical lens 33 and the like, and the diameter of adjacent light having different wavelengths in the wavelength distribution direction shown in FIG. Therefore, different wavelengths are mixed in the boundary portion of the adjacent light, and the wavelength distribution as shown in FIG.

In FIG. 7A, adjacent light fluxes having different wavelengths are arranged so as to partially overlap, but they may be arranged without gaps without overlapping.
FIG. 3A is a diagram (partial view of FIG. 1A) showing the positional relationship between the irradiation unit 12 and the measurement target X. FIG.
By adjusting the cylindrical lens 33 back and forth in the optical axis direction of the irradiation light beam L, the interval R (about 30 mm) between the “convergence position of the irradiation light beam L” and the “measurement point P” can be adjusted (FIG. 1). reference). The measurement location P is a region where the irradiation light beam L and the measurement target X intersect and is a predetermined point (or line) on the measurement target X imaged by the sensor unit 13. At this time, the closer the convergence position is to the measurement point P, the closer the interval between adjacent lights included in the irradiation light beam L is.
With such an adjustment mechanism, the wavelength distribution in the height direction of the irradiation light beam L can be optically enlarged or reduced.
According to the height measuring apparatus 11 of the present embodiment, the measurement of the solder bump size φ100 to 200 μm can be performed with an accuracy of 5 μm.

FIG. 3B is a perspective view showing the irradiation light beam L irradiated to the measurement object X. FIG. Here, the irradiation light beam L is widened in the main scanning direction of the measurement target X using a cylindrical lens or the like. Due to such widening, the measurement point P is expanded in the main scanning direction, so that the height measurement in the main scanning direction can be performed collectively without moving the measurement object X in the main scanning direction (FIG. 7 [ B]).
When a slit plate (having a long hole in the wavelength distribution direction of the irradiated light beam) is used instead of the cylindrical lens 33, the measurement target X and the illumination unit 12 may be moved relatively in the main scanning direction ( (See FIG. 7C).

<< Configuration 2 of Irradiation Unit 12 >>
FIG. 4 is a diagram illustrating an example of the irradiation unit 12.
As shown in FIG. 4, the multi-wavelength light source 41 emits light (white light or the like) including multiple wavelengths. The light passes through the color filter 43 after adjusting the beam diameter through the lens 42. The color filter 43 is a color-coded filter so that the transmission wavelength changes in the height direction.
The transmitted light beam of the color filter 43 passes through the lens 44 for adjusting the light beam interval. This lens 44 changes the transmitted light flux to an irradiation light flux L that converges to one point (line), like the cylindrical lens 33 described above. The irradiation light beam L is affected by the diffraction effect of the color filter 43 and the aberration effect of the lens 44, and the diameter of adjacent light having different wavelengths is widened. Therefore, different wavelengths are mixed in the boundary portion of the adjacent light, and the wavelength distribution as shown in FIG. 7 is shown.
In such a configuration, by adjusting the lens 44 back and forth in the optical axis direction of the irradiation light beam L, the wavelength distribution in the height direction of the irradiation light beam L can be optically enlarged or reduced.
In order to collectively measure the height in the main scanning direction, the irradiation light beam L may be widened in the main scanning direction using a cylindrical lens or the like.

<< Description of Calibration Process of Height Measuring Device 11 >>
FIG. 5 is a flowchart for explaining the calibration process of the height measuring device 11. Hereinafter, the operation of the calibration process will be described along the step numbers shown in FIG.

[Step S1] The control unit 14 drives the irradiation unit 12 to turn on and starts irradiation of the irradiation light beam L.

[Step S2] On the stage 20, a measurement reference point having a height of zero is provided. The control unit 14 moves the stage 20 in the XY directions via the stage driving unit 21 and positions the measurement reference point at the measurement point P of the irradiation light beam L.

[Step S3] The sensor unit 13 receives the reflected light from the measurement point P, and detects the wavelength (or wavelength mixing ratio) of the reflected light.

[Step S4] Based on the “current height of the measurement reference point” and the “wavelength (or wavelength mixing ratio)”, the control unit 14 “wavelength distribution of the irradiation light beam L on the memory in the control unit 14”. And the height of the measurement object X are calibrated.

[Step S5] The control unit 14 determines whether the calibration of the correspondence relationship in the memory is completed. When the calibration is not completed, the control unit 14 shifts the operation to Step S6. On the other hand, when the calibration is completed, the control unit 14 completes the calibration process and shifts the operation to a measurement process described later.

[Step S6] The control unit 14 raises the stage 20 by a predetermined width in the height direction (Z direction) via the stage drive unit 21. The sum total of the rise of the stage 20 so far is the current height of the measurement reference point. After this operation, the control unit 14 returns the operation to step S3.
Through this series of calibration processes, the data of the wavelength distribution in the height direction (see FIG. 7) at the measurement location P is accurately stored on the memory in the control unit 14.

<< Description of Measurement Process and Inspection Process of Height Measuring Apparatus 11 >>
FIG. 6 is a flowchart for explaining the measurement process of the height measuring device 11. Hereinafter, the operation of this measurement process will be described along the step numbers shown in FIG.

[Step S <b> 10] The control unit 14 returns the measurement reference point to zero height during calibration via the stage driving unit 21.

[Step S <b> 11] The control unit 14 moves the stage 20 XY via the stage drive unit 21, and aligns the measurement start position of the measurement target X with the measurement location P. This measurement location P is an inspection location of the measurement target X. For example, the position of the solder bump on the printed circuit board (X) may be specified from the registered coordinate data of the design drawing and the position of the solder bump may be aligned with the measurement location P.

[Step S12] The sensor unit 13 receives the reflected light from the measurement location P and detects the wavelength of the reflected light (or the mixing ratio of the wavelengths).
When the measurement location P is a dot, the sensor unit 13 detects the wavelength (or wavelength mixing ratio) for this one point (see FIG. 7C).
On the other hand, when the measurement points P are linear as shown in FIG. 3B, the sensor unit 13 uses the wavelength (or wavelength mixture) for the linear measurement points P at every sample interval in the main scanning direction. Ratio) is detected (see FIG. 7B).

[Step S13] The control unit 14 collates the wavelength of the reflected light (or the mixing ratio of the wavelengths) with the corresponding relationship on the memory, and obtains the height of the measurement location P. In the case where the wavelength of the reflected light (or the mixing ratio of the wavelengths) does not completely match the corresponding numerical value, it is preferable to interpolate the adjacent corresponding relationship to obtain the height of the measurement location P.

[Step S14] The control unit 14 determines whether or not the scanning of the measurement target X is completed. When the scanning is not completed, the control unit 14 shifts the operation to Step S15. On the other hand, when the scanning is completed, the control unit 14 ends the measurement process.

[Step S <b> 15] The control unit 14 moves the stage 20 in the surface direction via the stage driving unit 21, and positions the next scanning position of the measurement target X at the measurement location P. When the measurement location P is a dot, the control unit 14 performs surface movement vertically and horizontally at every sample interval in the main scanning direction and the sub-scanning direction. On the other hand, when the measurement point P is linear as shown in FIG. 3B, the control unit 14 moves the stage 20 at every sample interval in the sub-scanning direction.
With this series of measurement processes, the control unit 14 can measure the height (surface shape) of each location while scanning the surface of the measurement target X.

[Step S <b> 16] The control unit 14 performs abnormality determination (non-defective product determination) on the measurement location P (solder bump) of the printed circuit board of the measurement target X. For example, the control unit 14 determines an abnormal state such as a solder bump defect, height abnormality, or positional deviation by comparing the height detection result with design drawing data. The control unit 14 uses the result of the abnormality determination (non-defective product determination) for monitor display, user alarm, yield inspection, non-defective product selection, and the like.

<< Effects of this embodiment >>
As described above, in the present embodiment, the irradiation light beam L whose wavelength changes in the height direction is irradiated. Therefore, the wavelength of the reflected light changes depending on the height of the measurement location P. By associating the reflection wavelength and the mixing ratio thereof with the wavelength distribution in the height direction of the measurement location P, the height of the measurement location P can be obtained.

  In this case, it is relatively easy to stabilize the wavelength distribution of the irradiation light beam L in the height direction. Therefore, stable detection accuracy can be obtained as compared with the phase shift method using a piezo element.

  In addition, unlike the phase shift method, it is not necessary to photograph the projection pattern a plurality of times, and the measurement time can be shortened.

In the present embodiment, an optical mechanism (for example, a variable magnification optical system) that optically enlarges / reduces the wavelength distribution of the irradiation light beam L in the height direction is provided.
By using this optical mechanism to optically expand the wavelength distribution, the height measurable range can be expanded.
Conversely, by optically reducing the wavelength distribution, the height detection resolution can be made finer.

  Furthermore, in this embodiment, the correspondence between the shift amount and the reflection wavelength is calibrated while the measurement location P and the irradiation light beam L are relatively shifted in the height direction. This calibration process makes it possible to further increase the measurement accuracy of the height.

  Further, in the present embodiment, as shown in FIG. 7, the light of each color partially or entirely overlaps, and the height can be measured more finely according to the slight difference in the mixing ratio of the reflected wavelengths. Become. As a result, the height detection resolution can be further reduced.

  In particular, even if the total light amount of the irradiation light beam L varies, the mixing ratio of the wavelength light beams, which is a relative amount, does not change. For this reason, in the present embodiment, it is possible to detect the height with high accuracy and stability even if the total light amount varies.

<< Additional items of embodiment >>
In this embodiment, the irradiation unit 12 shown in FIG. 2 or 4 is used. However, the embodiment is not limited to this. Any irradiation light beam L whose wavelength changes without a gap in the height direction of the measurement target X can be used.

  Incidentally, the irradiation light beam L only needs to partially include a light beam in which a plurality of light beams having different wavelengths are arranged without a gap, and does not exclude an embodiment in which a gap is provided in a part of the irradiation light beam L. By providing a gap in the irradiation light beam L, a plurality of height measurement ranges divided by the gap can be easily identified.

  In the present embodiment, a convergent type irradiation light beam L as shown in FIG. 3A is used. However, the embodiment is not limited to this. A spreading type or parallel type irradiation light beam L may be used.

  In the present embodiment, the wavelength distribution in the height direction is enlarged or reduced depending on the lens position of the irradiation unit 12. However, the embodiment is not limited to this. For example, the wavelength distribution in the height direction may be enlarged or reduced using an optical system that enlarges or reduces the diameter of the irradiation light beam L.

  In the present embodiment, a measurement reference point having a height of zero is prepared, and the wavelength distribution data at the measurement location P is calibrated while moving up and down the stage 20. However, the embodiment is not limited to this.

  For example, by preparing multiple measurement reference points whose heights are shifted in stages and aligning these measurement reference points with measurement points P, the reflected wavelengths (or wavelength mixing ratios) at each height are detected. May be. In this calibration process, the raising / lowering operation of the stage 20 can be omitted.

Further, for example, the wavelength distribution data may be calibrated by detecting the reflection wavelength (or the mixing ratio of the wavelengths) while shifting the irradiation light beam L (irradiation unit 12) up and down.
In the present embodiment, an irradiation light beam L of visible light is used. However, the embodiment is not limited to this. In general, it may be in a wavelength range that can be detected on the sensor unit 13 side, and irradiation light beams in various wavelength ranges such as an infrared range and an ultraviolet range can be used.

  Moreover, in this embodiment, the case where one irradiation part 12 is provided was demonstrated. However, the embodiment is not limited to this. In one irradiation part 12, since the part which becomes shadow on the surface of the measuring object X arises, height measurement becomes partially impossible. Therefore, the irradiation light beam L may be selectively irradiated from a plurality of directions so as to reduce the shaded portion.

  In the present embodiment, the wavelength distribution of the irradiation light beam L in the height direction changes in the order of RGB. However, the embodiment is not limited to the order of RGB. For example, the wavelength of the irradiation light beam L may be continuously changed in finer wavelength steps. Further, for example, the wavelength distribution of the irradiation light beam L may be such that the mixing ratio of three or more wavelengths changes continuously.

  In this embodiment, the reflection wavelength (wavelength mixing ratio) detected by the sensor unit 13 may be corrected in consideration of the reflection spectral characteristics of the measurement point P (measurement target X). By this correction, the height can be accurately obtained without being affected by the reflection spectral characteristic of the measurement target X.

  Furthermore, an irradiation light beam whose wavelength continuously changes in the height direction may be generated using a spectral action such as an optical prism or a chromatic aberration action of an optical element.

As described above, the present invention is a technique that can be used for a height measuring apparatus.
Examples of application fields include a solder bump volume inspection device, a surface shape inspection device, a three-dimensional measurement device, a device for precisely inspecting the surface condition of the skin, and a device for reading a surface unevenness code such as a card. .

It is a figure which shows the height measuring apparatus 11 of this embodiment. It is a figure which shows an example of the irradiation part. It is a figure which shows the relationship between the irradiation light beam L and the measuring object X. FIG. It is a figure which shows an example of the irradiation part. It is a flowchart explaining the calibration process of the height measuring apparatus 11. FIG. 4 is a flowchart for explaining measurement processing of the height measuring device 11; It is a figure which shows the correspondence of the mixing ratio of reflection wavelength, and height.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Height measuring device, 12 ... Irradiation part, 13 ... Sensor part, 14 ... Control part, 20 ... Stage, 21 ... Stage drive part, 30 ... Mirror block, 33 ... Lens, 41 ... Multiwavelength light source, 43 ... Color Filter, X ... measurement object, L ... irradiated light beam

Claims (8)

A height measuring device for measuring a height at a predetermined measurement location of a test object,
An irradiation unit that irradiates the measurement spot of the test object with an irradiation light beam in which a plurality of light beams having different wavelengths are arranged in the height direction without any gaps;
A sensor unit that receives reflected light from the measurement location of the test object by the irradiated light beam, and detects a wavelength of the reflected light;
A height measurement device comprising: a height detection unit that obtains the height of the test object at the measurement location based on the wavelength of the reflected light detected by the sensor unit. The height measuring device according to claim 1,
The irradiation unit irradiates light beams having different wavelengths adjacent to each other in the height direction by partially overlapping the irradiation light beams,
The height detection unit obtains the height of the test object at the measurement location based on a mixing ratio of the wavelengths of the reflected light detected by the sensor unit. In the height measuring device according to claim 1 or 2,
The height detector is configured to determine the height by associating a wavelength of the reflected light or a mixture ratio thereof with a wavelength distribution of the irradiated light beam at the measurement location. In the height measuring device according to any one of claims 1 to 3,
The irradiation unit includes a variable magnification optical system that optically enlarges / reduces the wavelength distribution of the irradiation light beam in the height direction. In the height measuring device according to any one of claims 1 to 4,
A calibration unit that calibrates the correspondence between the shift amount and the wavelength of reflected light at the measurement location by relatively shifting the measurement location and the irradiation light beam in the height direction,
The height detection unit obtains the height of the measurement location by comparing the wavelength of the reflected light of the measurement location or a mixture ratio thereof with the correspondence calibrated by the calibration unit. Height measuring device. The height measuring device according to any one of claims 1 to 5,
The irradiation unit is
Irradiation light flux in which a plurality of light fluxes having different wavelengths are arranged in the height direction by irradiating each surface of the multi-faced mirror with a plurality of light fluxes having different wavelengths and aligning the reflection direction of the light flux group in substantially one direction. The height measuring device characterized by generating. The height measuring device according to any one of claims 1 to 5,
The irradiation unit is
A height measuring apparatus, wherein the irradiation light beam is generated by changing a wavelength in the height direction by passing a light beam including a plurality of wavelengths through a wavelength selection element. A height measurement method for measuring the height at a predetermined measurement location of a test object,
Irradiation step of irradiating the measurement spot of the test object with an irradiation light beam in which a plurality of light beams having different wavelengths are arranged without gaps in the height direction; and
Detecting the reflected light from the measurement location of the test object by the irradiated light beam, and detecting the wavelength of the reflected light; and
A height measurement method comprising: a height measurement step for obtaining a height of the test object at the measurement location based on the wavelength of the reflected light detected in the detection step.

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