JP2009058459A - Profile measuring system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To measure only a portion, by image measurement using optical cutting, where it is determined to be suited to image measurement by optical cutting. <P>SOLUTION: In a profile measuring device 1, a slit light source unit 12 irradiates a slit light to a test substance 20 of a measuring object. Imaging sections 14A and 14B image the test substance 20 from two different directions. A controller 15 calculates the intensity difference of the two images taken from two different directions, and determines the portion where the slit light is now irradiating is unsuitable for optical measurement when the calculated intensity difference is larger than a predetermined threshold TH<SB>A</SB>. The present invention can be applied to profile measuring devices in which image measurement is carried out by optical cutting. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a shape measuring apparatus, and more particularly to a shape measuring apparatus suitable for use in image measurement by light cutting.

  Conventionally, there is a shape measuring device that projects slit light to measure the three-dimensional shape of a test object.

  The principle of measurement by the slit light projection method will be briefly described.

  The object placed on the stage of the shape measuring apparatus is irradiated with a strip-shaped slit light with a narrow cross section. The test object irradiated with the slit light is imaged by an imaging element such as a CCD (Charge Coupled Device). In the captured image, the slit image becomes a straight line if the portion irradiated with the slit light of the test object is flat, and if the irradiated portion is uneven, the slit image is deformed according to the position in the depth direction. To do. By moving the stage in a direction perpendicular to the slit light, the strip-shaped slit light is scanned over the entire test object, so that the three-dimensional shape of the test object can be measured.

  Further, a method has been proposed in which both image measurement by light irradiation and contact-type measurement by a touch probe are performed, and measurement is performed by any one of them (for example, see Non-Patent Document 1).

KREON AQUILON (manufactured by Kreon Technology), International Technology Transfer Corporation, [searched July 18, 2007], Internet <URL: http://www.ittc.co.jp/hproduct/kreon/aquilon.htm>

  However, Non-Patent Document 1 does not disclose how to use image measurement by light irradiation and contact-type measurement by a touch probe depending on what kind of judgment standard is used.

  On the other hand, in the shape measurement using light, if the test object has a mirror surface like metal, the light irradiated to the test object is regularly reflected, and the strong light is directly incident on the image sensor, There was a problem that accurate measurement was not possible.

  The present invention has been made in view of such circumstances, and appropriately determines whether the measurement part is suitable for image measurement by light cutting, and the measurement part determined to be suitable for image measurement by light cutting. Only can be measured by image measurement by light cutting.

  The shape measuring apparatus of the present invention is obtained by an illuminating unit that irradiates a test object to be measured with slit light, an imaging unit that images the test object irradiated with the slit light, and an imaging unit. Based on the slit image observed in the image, optical measurement means for measuring the shape of the test object, and whether the irradiated part, which is the part irradiated with the slit light of the test object, is a part suitable for optical measurement Determining means, and the optical measuring means measures the shape of the test object for a portion determined by the determining means to be a portion suitable for optical measurement.

  According to the present invention, based on the luminance of the slit image of the measurement part, it is determined whether the measurement part is suitable for image measurement by light cutting, so only the measurement part determined to be suitable for image measurement by light cutting. Can be measured by image measurement by light cutting.

  FIG. 1 shows a schematic configuration of a shape measuring apparatus to which the present invention is applied.

  The shape measuring apparatus 1 shown in FIG. 1 includes a uniaxial stage 11, a slit light source unit 12, a diffused light source unit 13, imaging units 14 A and 14 B, a controller 15, and a touch probe 23. A test object 20 to be measured is placed on the single axis stage 11.

  The single-axis stage 11 is a table that can be moved to one axis (x-axis) in the horizontal direction of the drawing under the control of the controller 15. A slit light source unit 12 is fixedly disposed above the center position of the movement range of the uniaxial stage 11. The slit light source unit 12 includes a semiconductor laser 16 that emits laser light, and a cylindrical lens 17 that shapes the laser light emitted therefrom into slit-like light. The slit light emitted from the cylindrical lens 17 and perpendicular to the moving direction of the uniaxial stage 11 is applied to the test object 20 placed on the uniaxial stage 11. In this embodiment, when the slit light is unnecessary, the laser light is turned off. Instead, the slit light source unit 12 can be moved by an arm or the like so that the measurement is not affected. You may make it evacuate.

  The diffusion light source unit 13 includes a lamp light source 18 and a diffusion plate 19 and is disposed obliquely above a predetermined angle with respect to the vertical direction of the test object 20, and irradiates the test object 20 from above with the diffused light. .

  The imaging units 14A and 14B each have an imaging device such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor) sensor, and take an image of the test object 20 under the control of the controller 15. The image (data) to be processed is supplied to the controller 15.

  The imaging units 14A and 14B are installed symmetrically with respect to the optical axis of the slit light, and the imaging unit 14A is on the right side when viewed from the front of the uniaxial stage 11 (right side from the slit light on the test object 20 in FIG. ) As the main imaging range, and the imaging unit 14B is in charge of the left side as viewed from the front of the single-axis stage 11 (left side from the slit light on the test object 20 in FIG. 1) as the main imaging range. Since the direction of the slit light (light projecting direction) and the imaging direction are different, so-called light cutting is observed in the images captured by the imaging units 14A and 14B, and a deformed slit image is observed. Note that the imaging units 14A and 14B do not necessarily have to be arranged symmetrically, as long as they can image the test object 20 from different directions. Three or more imaging units may be provided.

  The controller 15 controls each part of the shape measuring apparatus 1. For example, the controller 15 moves the single-axis stage 11 to a predetermined position, or performs lighting control of the slit light source unit 12 or the diffusion light source unit 13. The controller 15 also supplies imaging control signals to the imaging units 14A and 14B.

  The touch probe 23 has a contact sensor at its tip. The touch probe 23 is a plane parallel to the plane of the uniaxial stage 11, the y-axis perpendicular to the x-axis, the z-axis in the vertical direction, and the θ-axis and the z-axis that are rotation axes centered on the z-axis. It is fixed to a robot arm (not shown) capable of driving four or more axes including the φ axis that is inclined in the vertical direction, and the test object 20 can be contacted from an arbitrary position. Further, the signal from the touch sensor of the touch probe 23 and the movement displacement amount of the touch probe 23 from the robot arm can always be input to the controller 15. The controller 15 can acquire the position where the touch probe 23 contacts the test object 20 by inputting the movement displacement amount from the robot arm using a signal from the contact sensor of the touch probe 23 as a trigger.

  In the shape measuring apparatus 1 configured as described above, the shape of the slit light irradiated to the test object 20 is imaged by the imaging unit 14A or 14B, and the shape of the test object 20 is measured from the slit image. The shape of a desired measurement portion of the test object 20 is measured by both the optical measurement (non-contact measurement) to be performed and the contact measurement in which the touch probe 23 is brought into contact and the shape of the test object 20 is measured from the displacement. can do.

  FIG. 2 is a block diagram showing a functional configuration of the shape measuring apparatus 1. In FIG. 2, portions corresponding to those in FIG. 1 are denoted by the same reference numerals, and description of overlapping portions is omitted as appropriate.

  The shape measuring apparatus 1 includes a uniaxial stage 11, a slit light source unit 12, a diffused light source unit 13, imaging units 14A and 14B, a controller 15, an operation unit 21, a display unit 22, a touch probe 23, and a robot arm. . The controller 15 includes a stage control unit 31, a light source control unit 32, a camera control unit 33, a UI (User Interface) control unit 34, a determination unit 35, an optical shape calculation unit 36, a contact shape calculation unit 37, and a storage unit 38. Have Each unit in the controller 15 can exchange various data with each other as necessary.

  The operation unit 21 includes a keyboard for inputting characters and numerical values, a mouse for instructing a predetermined position on the screen displayed on the display unit 22, a joystick for moving the one-axis stage 11 and the touch probe 23, and the like. While accepting an operation, an operation signal corresponding to the operation is supplied to the UI control unit 34. The display unit 22 is, for example, a CRT (Cathode Ray Tube) display or an LCD (Liquid Crystal Display), and displays images captured by the imaging units 14A and 14B, or predetermined characters corresponding to user operations. Or display graphics. The user designates a predetermined portion of the image of the test object 20 displayed on the display unit 22 (the image captured by the imaging unit 14A or 14B), so that the user can measure the shape of the test object 20 at the target portion. A certain measurement part can be specified.

  The stage control unit 31 moves the uniaxial stage 11 to a predetermined position. The light source control unit 32 controls the slit light source unit 12 and the diffusion light source unit 13. The camera control unit 33 controls imaging by the imaging unit 14A and the imaging unit 14B. Based on the operation signal supplied from the operation unit 21, the UI control unit 34 displays a predetermined image on the display unit 22, or performs predetermined control on the stage control unit 31, the light source control unit 32, the camera control unit 33, and the like. Request. For example, when the user performs an operation for moving the single-axis stage 11 in the operation unit 21, the UI control unit 34 requests the stage control unit 31 to move a predetermined amount. The stage control unit 31 moves the uniaxial stage 11 by a predetermined amount in response to a request from the UI control unit 34.

  The determination unit 35 determines whether the measurement part of the test object 20 designated by the user is a part suitable for optical measurement.

  Measurement using a slit image has an advantage that multi-point data can be acquired in a short time (at a time). On the other hand, in the measurement using the slit image, the reflected light reflected by the test object 20 is used, but if the reflected light enters as a strong component (Specular Spike) of the specularly reflected light, a measurement error occurs. There is also a problem that measurement is performed with a large value (incorrect detection). Therefore, it is necessary to exclude the image including the slit image based on the specular reflection light from the image for measurement, but if the suitability of the optical measurement is determined based on the amount of light, the image including the slit image based on the specular reflection light is excluded. Can not do it.

  Therefore, in the shape measuring apparatus 1, the specularly reflected light is reflected only in one predetermined direction, and the diffused light is constant (Lambert's cosine law) regardless of the direction, and from two or more different directions. By taking a slit image and comparing the intensity (brightness) of the slit image, the image of the specularly reflected light is excluded and optical measurement is performed.

That is, the determination unit 35 calculates the difference in the intensity (luminance) of the slit images in the measurement portions of the images captured by the imaging unit 14A and the imaging unit 14B, and the obtained difference is greater than the predetermined threshold TH _A. Therefore, it is determined that one of the images may be an image including a slit image by specular reflection light, and the measurement portion is determined not to be suitable for optical measurement. Further, even if the difference in the intensity of the slit images is equal to or less than the predetermined threshold TH _A , the determination unit 35 does not have sufficient intensity if both the intensity of the two slit images is equal to or less than the predetermined threshold TH _B. Therefore, it is determined that the measurement part is not suitable for optical measurement. When it is determined that the measurement part of the test object 20 is not a part suitable for optical measurement, the part is supplied to the storage unit 38 as a measurement inappropriate position.

  The optical shape calculation unit 36 generates (calculates) shape data of the test object 20 from the slit image included in the images supplied from the imaging units 14A and 14B via the camera control unit 33. The shape data is acquired as line-shaped (point cloud) data irradiated with slit light. The contact shape calculation unit 37 uses the signal from the contact sensor as a trigger to capture the output of the encoder provided at each joint of the robot arm, and obtains the movement displacement information of the touch probe 23. Then, the shape calculation unit 37 generates (calculates) shape data of the test object 20 from the movement displacement of the touch probe 23.

  The storage unit 38 temporarily stores the measurement inappropriate position (information) supplied from the determination unit 35. The storage unit 38 also stores images obtained by the imaging units 14A and 14B as necessary. The storage unit 38 also stores a program for controlling the shape measuring apparatus 1 and predetermined data as necessary.

  Next, the measurement process of the shape measuring apparatus 1 will be described with reference to the flowchart of FIG. Prior to this processing, it is assumed that the laser light from the slit light source unit 12 and the diffused light from the diffused light source unit 13 are extinguished as an initial state.

  First, in step S1, the light source control unit 32 controls the diffusion light source unit 13 to turn on the diffusion light source.

  The user operates the operation unit 21 to move the uniaxial stage 11 so that the test object 20 is at a desired position within the imaging range of the imaging units 14A and 14B, and then instructs imaging. In step S <b> 2, the UI control unit 34 receives an operation signal representing imaging from the operation unit 21 and instructs the camera control unit 33 to perform imaging. The imaging units 14A and 14B image the test object 20 on the uniaxial stage 11 under the control of the camera control unit 33.

  In step S <b> 3, the UI control unit 34 displays a captured image including the test object 20 on the display unit 22 and displays a message such as “Please specify a measurement part” on the display unit 22. When the user operates the operation unit 21 to instruct a predetermined region of the image of the test object 20 displayed on the display unit 22 as a measurement part, the UI control unit 34 from the operation unit 21 in step S4. An operation signal is acquired, and the measurement part of the test object 20 is specified from the region specified by the user in the image and the current position of the single-axis stage 11. The position (x coordinate value) of the one-axis stage 11 for specifying the measurement part of the test object 20 and the region in the image are temporarily stored in the storage unit 38.

  In step S5, the light source control unit 32 controls the diffusion light source unit 13 to turn off the diffusion light source, and in step S6, controls the slit light source unit 12 to turn on the laser light. As a result, the slit light is irradiated onto the uniaxial stage 11.

  In step S7, the stage control unit 31 moves the uniaxial stage 11 to the start position. For example, assuming that the entire driving range of the single-axis stage 11 is scanned, the position that is one end of the driving range is the start position, and the other end is the end position. In addition, when the range in which the test object 20 is placed is extremely short with respect to the entire driving range of the uniaxial stage 11, the driving range of the uniaxial stage 11 in the shape measurement is designated (teaching) in advance. It may be.

  In step S8, the imaging units 14A and 14B image the test object 20 irradiated with slit light. The captured image is supplied to the determination unit 35 via the camera control unit 33.

  In step S9, the determination unit 35 determines whether the slit light is scanning the measurement portion designated by the user. This determination is made based on the current position of the single-axis stage 11 and the images supplied from the imaging units 14A and 14B.

  If it is determined in step S9 that the slit light is not scanning the measurement portion designated by the user, the process proceeds to step S14.

On the other hand, when it is determined in step S9 that the slit light is scanning the measurement portion specified by the user, the process proceeds to step S10, and the determination unit 35 determines the images captured by the imaging units 14A and 14B. A difference in the intensity (luminance) of the slit image in the measurement part is calculated, and it is determined whether the obtained difference in the intensity of the slit image is equal to or less than a predetermined threshold TH _A.

If it is determined in step S10 that the obtained difference in the intensity of the slit images is greater than the threshold TH _A , the process proceeds to step S11, and the determination unit 35 performs optical measurement on the measurement portion that is now scanned by the slit light. It is determined that the portion is not suitable for the measurement, and the portion is supplied to the storage unit 38 as a measurement inappropriate position and stored.

On the other hand, if it is determined in step S10 that the obtained difference in the intensity of the slit images is equal to or less than the threshold TH _A , the process proceeds to step S12, and the determination unit 35 determines that the intensity of the slit images is the imaging units 14A and 14B. It is determined whether any of the images picked up in step _{B is} equal to or less than the threshold value THB. In step S12, when the intensity of the slit image is determined to either be less than or equal to the threshold value TH _B, the process proceeds to step S11.

On the other hand, in step S12, when the intensity of the slit image is not equal to or smaller than the threshold value TH _B in any of the image captured by the imaging unit 14A and 14B, i.e., the intensity of at least one of the slit image is the threshold If larger than TH _B , in step S13, the optical shape calculation unit 36 calculates the shape data of the test object 20 from the slit images included in the images supplied from the imaging units 14A and 14B via the camera control unit 33. To get.

  In step S14, the stage controller 31 determines whether the current stage position is the end position. If it is determined in step S14 that the current stage position is not the end position, the process proceeds to step S15, and the stage control unit 31 moves the uniaxial stage 11 by a predetermined amount.

  After the process of step S15, the process returns to step S8, and the processes of steps S8 to S14 are repeatedly executed. As a result, the test object 20 is imaged at each stage position from the start position to the end position, and shape data is acquired for a measurement portion suitable for optical measurement.

  If it is determined in step S14 that the current stage position is the end position, the process proceeds to step S16, and the contact shape calculation unit 37 determines whether the measurement inappropriate position is stored in the storage unit 38. . If it is determined in step S16 that the measurement inappropriate position is stored in the storage unit 38, the process proceeds to step S17, and the contact shape calculation unit 37 controls the robot arm and is stored in the storage unit 38. The measurement inappropriate position is measured by the touch probe 23, and the measurement result (movement displacement) of the measurement inappropriate position by the touch probe 23 is acquired. And the contact shape calculating part 37 produces | generates the shape data of a measurement inappropriate position from the acquired measurement result.

  The measurement inappropriate positions that have been measured by the touch probe 23 are erased from the storage unit 38, and measurement by the touch probe 23 is performed for all measurement inappropriate positions stored in the storage unit 38 until there is no measurement inappropriate position in the storage unit 38. Steps S16 and S17 are repeated until is completed.

  If it is determined in step S16 that there is no measurement inappropriate position in the storage unit 38, the process proceeds to step S18, and the optical shape calculation unit 36 obtains the shape data obtained from the slit image and the touch probe 23. The obtained shape data is synthesized. After the combined shape data of the entire measurement range of the test object 20 is displayed on the display unit 22 or stored in the storage unit 38, the process ends.

  Note that if there is no shape data obtained by the touch probe 23, that is, if measurement has been performed with the slit image for all of the measurement parts designated by the user, the process of step S18 is omitted.

As described above, the shape measuring apparatus 1 calculates the difference in the intensity (luminance) of the slit image from the image of the test object 20 imaged from two different directions, and the obtained intensity difference is the predetermined threshold TH. _{If it is} greater than _A or the intensity of the two slit images is less than or equal to the predetermined threshold TH _B, it is determined that the part is not suitable for optical measurement. Can be determined appropriately (automatically), and only a suitable measurement portion can be measured by optical measurement. In other words, in the shape measuring apparatus 1, it is possible to prevent erroneous detection due to measurement using a slit image by regular reflection light.

  Furthermore, in the shape measuring apparatus 1, since the measurement part which is not suitable for measurement by light cutting can be measured by the touch probe 23, all the measurement parts designated by the user can be measured accurately.

  In the above-described example, it is determined whether the measurement part is a part suitable for optical measurement using two images captured by the imaging units 14A and 14B arranged in two different directions. It is also possible to determine whether or not the measurement portion is a portion suitable for optical measurement by using two images in which the NA (numerical aperture) is changed from one direction. More specifically, in the case of imaging with two types of NA, the amount of light received by diffused light changes only in the ratio of NA, but when a strong component of specular reflection light enters, the ratio of luminance Is greatly changed from the ratio of NA, the determination unit 35 calculates the ratio of the intensity of the slit images of the two images, and determines whether the measurement part is equal to the ratio of NA, so that the measurement part is suitable for measurement by optical cutting. Can be judged appropriately.

  For example, instead of the imaging unit 14A and the imaging unit 14B in FIG. 1, the imaging unit 41 shown in FIG. 4 is arranged in either the imaging unit 14A or the imaging unit 14B in FIG.

  The imaging unit 41 includes CCDs 51 and 52, imaging lenses 53 and 54, diaphragms 55 and 56 having different NAs, a BS (beam splitter) 57, and an objective lens 58.

  The reflected light of the slit light reflected by the test object 20 passes through the objective lens 58 and enters the BS 57. Part of the reflected light incident on the BS 57 is reflected by the joint surface of the BS 57 and received by the CCD 52 via the diaphragm 56 and the imaging lens 54. On the other hand, light that is not reflected by the joint surface of the BS 57 is received by the CCD 51 through the diaphragm 55 and the imaging lens 53. As a result, two images with different NAs can be acquired by one imaging unit 41.

  The determination unit 35 calculates the ratio of the intensity of the slit images of the two images and determines whether it is equal to the ratio of NA. Thereby, it can be judged appropriately (automatically) whether the measurement part is suitable for the measurement by light cutting. In other words, when a strong component of specularly reflected light enters, unevenness occurs in the NA of the imaging system, but erroneous detection due to aberrations caused by this unevenness can be prevented.

  Note that the example shown in FIG. 4 has a configuration in which two CCDs are acquired in one imaging unit and two images with different NAs are acquired, but only one CCD is included in one imaging unit. However, it is also possible to adopt a configuration in which two images with different NAs are acquired by two imaging operations with different apertures and different times. Further, it may be determined whether or not the measurement portion is suitable for measurement by light cutting using three or more NA different images.

  In the above-described example, the measurement part is determined by designating a desired position of the image captured by the user. However, the measurement part can be designated using CAD data. In this case, a measurement part is set in advance in the CAD data of the test object 20, and points corresponding to arbitrary three points on the CAD data are designated on the image captured by the imaging unit 14A or 14B. As a result, the measurement portion set in the CAD data is reflected on the test object 20 on the single-axis stage 11.

  In this specification, the steps described in the flowcharts include processes that are executed in parallel or individually even if they are not necessarily processed in time series, as well as processes that are executed in time series in the described order. Is also included.

  The embodiments of the present invention are not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present invention.

It is a figure which shows the schematic structure of the shape measuring apparatus to which this invention is applied. It is a block diagram which shows the functional structural example of a shape measuring apparatus. It is a flowchart explaining a measurement process. It is a figure which shows the other example of an imaging part.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Shape measuring apparatus, 11 1 axis | shaft stage, 12 Slit light source unit, 13 Diffuse light source unit, 14A, 14B Image pick-up part, 15 Controller, 21 Operation part, 22 Display part, 23 Touch probe, 31 Stage control part, 32 Light source control part , 33 camera control unit, 34 UI control unit, 35 determination unit, 36 optical shape calculation unit, 37 contact shape calculation unit, 38 storage unit

Claims (5)

Illumination means for irradiating slit light to the object to be measured,
Imaging means for imaging the test object irradiated with the slit light;
Optical measuring means for measuring the shape of the test object based on the slit image observed in the image obtained by the imaging means;
A determination means for determining whether an irradiated portion that is the portion irradiated with the slit light of the test object is a portion suitable for optical measurement,
The shape measuring apparatus characterized in that the optical measuring means measures the shape of the test object for a portion determined by the determining means to be a portion suitable for optical measurement. Contact-type measuring means for measuring the shape of the test object in contact with the test object,
The shape measuring apparatus according to claim 1, wherein the contact-type measuring unit measures the shape of the test object with respect to a portion that is determined not to be suitable for optical measurement by the determining unit. The imaging means images the test object from two or more different directions,
The determination means determines whether the irradiated portion is a portion suitable for optical measurement by determining whether the difference in the intensity of the slit image in two or more captured images is greater than a predetermined threshold. The shape measuring apparatus according to claim 1, wherein The imaging means images the test object with two or more different NAs,
The determination means calculates the ratio of the intensity of the slit image in two or more captured images, and determines whether the irradiated portion is a portion suitable for optical measurement by determining whether the ratio is equal to the ratio of NA. The shape measuring apparatus according to claim 1, wherein: Further comprising a designation means for designating a measurement part, which is a part for measuring the shape of the test object, on an image imaged by the imaging means;
The shape measuring apparatus according to claim 1, wherein the determination unit determines whether the irradiated portion is a portion suitable for optical measurement when the irradiated portion is the measurement portion.

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