JP5439218B2 - Image measuring machine - Google Patents

Description

  The present invention relates to an image measuring machine equipped with a telecentric optical system.

As shown in FIG. 5, a telecentric optical system including a front lens 12, a rear lens 13, and a telecentric stop 14 is known.
The telecentric optical system has a feature that the object field is wide, the focal depth is deep, and the imaging magnification is determined by the focal length of the front lens and the rear lens regardless of the position of the object. Therefore, a telecentric optical system is widely used for wide field collective measurement of objects to be measured such as blade tools, machine parts, assembled electronic parts, and the like (see Patent Document 1).

For example, as shown in FIG. 6A, an object to be measured having a step in the vertical direction (Z-axis direction) is measured with an image measuring machine equipped with a non-telecentric optical system that is not a telecentric optical system. Measurement), as shown in FIG. 5B, an image having a large dimensional change in the X and Y axis directions orthogonal to the Z axis direction is obtained.
On the other hand, when an image is measured with an image measuring machine equipped with a telecentric optical system, an image with little dimensional change in the X and Y axis directions orthogonal to the Z axis direction is obtained as shown in FIG. It is done. That is, a telecentric optical system is widely used because it is possible to accurately measure the shape in the X and Y axis directions even with an object having a step.

JP 2003-232999 A

  By the way, in a telecentric optical system, the numerical aperture (NA) is generally decreased to increase the depth of focus. However, if the depth of focus is increased, the focus position can be accurately detected. It becomes difficult. Therefore, there is a problem that dimension measurement in the Z-axis direction cannot be performed, and as a result, three-dimensional shape measurement becomes impossible.

  An object of the present invention is to provide an image measuring machine that solves the problems while maintaining the features of a telecentric optical system and enables three-dimensional shape measurement of an object to be measured.

In the image measuring machine according to the present invention, the table on which the object to be measured is placed and the imaging optical unit are relatively moved by a relative movement mechanism, and the image of the object to be measured is obtained from the image of the object to be measured taken by the imaging optical unit. In the image measuring machine for measuring a shape, the imaging optical unit is configured to capture a telecentric optical system having a front lens, a rear lens, and a telecentric stop, and an image of the object to be measured formed by the telecentric optical system. is configured to include a means, by using a laser beam, Bei give a non-contact position measuring means for measuring the position along the optical axis of the object surface on the optical axis of the telecentric optical system in a non-contact, The non-contact position measuring means passes a laser light source and a laser beam emitted from the laser light source through a front lens of the telecentric optical system. A laser beam irradiation optical system for irradiating the object to be measured, and a deviation amount detection for detecting a deviation amount of the surface of the object to be measured with respect to the focal position of the front lens by processing the laser beam reflected by the surface of the object to be measured A relative movement command means for operating the relative movement mechanism, and a relative movement amount between the table and the telecentric optical system in the optical axis direction so that the deviation amount detected by the deviation amount detection unit is eliminated. Position detecting means for detecting, wherein the front lens includes a first front lens, a second front lens, and a third front lens arranged from the object side, wherein the first front lens and the second front lens are An afocal optical system is configured, and the laser light irradiation optical system includes a collimator lens that collimates laser light emitted from the laser light source, and the collimator lens. And a beam splitter that reflects the laser beam toward the first front lens, and the telecentric diaphragm has a rear focal position of the third front lens that matches a front focal position of the rear lens. The beam splitter is arranged at a position where a rear focal position of the first front lens and a front focal position of the second front lens coincide with each other.

According to such a configuration, since the imaging optical unit is configured to include the telecentric optical system, even in the measurement object having a step, the shape in the direction orthogonal to the optical axis of the telecentric optical system can be accurately obtained. In addition, wide field of view can be measured.
In addition, since there is provided non-contact position measuring means for measuring the position of the surface of the object to be measured on the optical axis of the telecentric optical system in a non-contact manner using laser light, the optical axis direction of the telecentric optical system is provided. It is also possible to accurately measure the position of the object to be measured.
Therefore, it is possible to solve the problem of the telecentric optical system while maintaining the characteristics of the normal telecentric optical system and to realize the three-dimensional shape measurement of the object to be measured.
Furthermore, since the position of the surface of the object to be measured in the optical axis direction can be detected using an autofocus laser displacement meter, the position of the surface of the object to be measured can be detected with high accuracy.
In addition, the first front lens can be used for collimating light, and the remaining second front lens and third front lens can be used to correct aberration due to image formation of the optical system. Thereby, even if the aperture of the laser beam is increased, the flare of the laser beam and illumination light from the lens surface can be reduced. In addition, when the aperture of the laser beam is increased, the detection accuracy of the focus position is improved, so that more accurate measurement can be realized.

  In the image measuring machine of the present invention, it is determined that the position of the surface of the object measured by the non-contact position measuring means has reached a position within the focal depth of the telecentric optical system and a position outside the focal depth. When it is determined by the depth-of-focus determination means and the depth-of-focus determination means that the position of the surface of the object to be measured has reached a position close to the focal depth of the telecentric optical system, the surface of the object to be measured is determined. A depth-of-focus adjustment command means for operating the relative movement mechanism to relatively move the table and the telecentric optical system in the optical axis direction so that the position is substantially at the center of the focal depth of the telecentric optical system. It is preferable to provide.

  When measuring an object having waviness (undulation) in the vertical direction with an image measuring machine equipped with a normal telecentric optical system, as shown in FIG. 7, the telecentric optical system is measured at a certain height position. When moving along (FIGS. 7A to 7C), the surface position of the object to be measured may deviate from the focal depth of the telecentric optical system (in the case of FIG. 7C). In such a case, since the object to be measured cannot be measured, the measurement is temporarily stopped, the telecentric optical system is moved up and down with respect to the surface of the object to be measured, and the surface of the object to be measured is the focal depth of the telecentric optical system. After making adjustments to get inside, the measurement work must be resumed.

According to the present invention, when measuring an object to be measured having waviness (undulations) in the vertical direction, as shown in FIG. 3, the position of the surface of the object to be measured is determined by the focal depth determination means so that the focal depth of the telecentric optical system is If it is determined that the position has reached a near position (determination set value HSU, HSD) that is out of the focal depth, the surface depth of the object to be measured is set to the approximate focal depth of the telecentric optical system by the focal depth adjustment command means. Thus, the relative movement mechanism is operated so that the table and the telecentric optical system are relatively moved in the optical axis direction.
Therefore, since the surface position of the object to be measured is always maintained within the focal depth of the telecentric optical system, continuous measurement can be realized.

The image measuring machine of the present invention, before Symbol first front lens may be constituted by a single lens or cemented lens.

The schematic diagram which shows the image measuring device which concerns on 1st Embodiment of this invention. The schematic diagram which shows the image measuring machine which concerns on 2nd Embodiment of this invention. The figure which shows the example of a continuous measurement using the image measuring machine which concerns on 2nd Embodiment same as the above. The schematic diagram which shows the image measuring machine which concerns on 3rd Embodiment of this invention. The schematic diagram which shows a telecentric optical system. The figure which shows the characteristic of a non-telecentric optical system and a telecentric optical system. The figure which shows a problem when measuring a to-be-measured object with a telecentric optical system.

<First Embodiment (see FIG. 1)>
As shown in FIG. 1, the image measuring machine according to the first embodiment includes a table 1 on which an object to be measured W is placed, an imaging optical unit 10 disposed immediately above the table 1, and a non-contact position measuring unit. The autofocus laser displacement meter unit 20 and the illumination optical unit 40, the table 1, the imaging optical unit 10, the autofocus laser displacement meter unit 20 and the illumination optical unit 40 are arranged in a three-dimensional direction, that is, in the left-right direction (X-axis direction). The relative movement mechanism 50 for relative movement in the front-rear direction (Y-axis direction) and the vertical direction (Z-axis direction), the image picked up by the image pickup optical unit 10 and the measurement object obtained by the autofocus laser displacement meter unit 20 And a shape calculation unit 60 for obtaining the three-dimensional shape of the object to be measured from the surface height (Z-axis direction) information.

The imaging optical unit 10 includes a telecentric optical system 11 and a CCD camera 15 as an imaging unit that captures an image of a measurement object imaged by the telecentric optical system 11.
The telecentric optical system 11 includes a front lens 12, a rear lens 13 arranged so that a front focal position coincides with a rear focal position of the front lens 12, a rear focal position and a rear lens of the front lens 12. And a telecentric diaphragm 14 disposed at a position where the front focal position of 13 coincides. Here, a parallel light flux is formed between the front lens 12 and the rear lens 13. The front lens 12 and the rear lens 13 may be single lenses, but are preferably constituted by a plurality of lenses.
The CCD camera 15 is disposed at the rear focal position (imaging position) of the rear lens 13.

The autofocus laser displacement meter unit 20 measures the position of the surface of the object to be measured on the optical axis of the telecentric optical system 11 in a non-contact manner using a laser beam. It is composed of an autofocus laser displacement meter of the double pinhole method.
Specifically, the laser light source 21, the laser light irradiation optical system 22 that irradiates the measurement object with the laser light emitted from the laser light source 21 through the front lens 12 of the telecentric optical system 11, and the surface of the measurement object. A deviation amount detection unit 31 that detects the deviation amount of the surface of the object to be measured with respect to the focal position of the front lens 12 by processing the reflected laser light, and the relative amount so that the deviation amount detected by the deviation amount detection unit 31 is eliminated. A servo circuit 37 as a relative movement command means for operating the moving mechanism 50 and a position detection means 38 for detecting the relative movement amount between the table 1 and the telecentric optical system 11 in the optical axis direction are provided.

As the laser light source 21, a red semiconductor laser is used.
The laser light irradiation optical system 22 includes a collimator lens 23 that converts the laser light emitted from the laser light source 21 into parallel light, and reflects the parallel light from the collimator lens 23 and is incident perpendicular to the optical axis of the telecentric optical system 11. and two beam splitters 24 and 25 make, and a beam splitter 26 for reflecting toward the front side lens 12 the laser light from the beam splitter 25 is disposed between the front lens 12 and the telecentric stop 14 of the telecentric optical system 11 It is configured to include.

  The deviation amount detection unit 31 includes an imaging lens 32 that forms an image of reflected light that is reflected by the object to be measured and transmitted through the beam splitter 24, a beam splitter 33 that divides the light transmitted through the imaging lens 32, Two pinholes 34A and 34B arranged before and after the focused position of each reflected light divided by the beam splitter 33, and a photodiode for detecting the amount of reflected light that has passed through each pinhole 34A and 34B, respectively. And a shift amount detection circuit 36 for detecting the shift amount between the front focal position of the front lens 12 and the surface of the object to be measured based on the outputs from the light receiving elements 35A and 35B. ing.

The servo circuit 37 operates the relative movement mechanism 50 so that the shift amount detected by the shift amount detection circuit 36 becomes zero. Here, the imaging optical unit 10, the autofocus laser displacement meter unit 20, and the illumination optical unit 40 are integrally moved in the Z-axis direction.
The position detection means 38 includes a scale 38A provided in the imaging optical unit 10 along the Z-axis direction, and a detection head 38B that faces the scale 38A and is fixed to a stationary side (such as a fixed side member of the image measuring machine). It is comprised including. As the position detection method, a known method such as a photoelectric method, a capacitance method, or a magnetic method can be used.

  The illumination optical unit 40 includes an illumination light source 41, a collimator lens 42 that converts the light from the illumination light source 41 into parallel light, and reflects the illumination light that has passed through the collimator lens 42, transmits the beam splitter 25, and transmits the beam splitter 26. And a mirror 43 to be incident on the mirror.

  Although the relative movement mechanism 50 is not illustrated, for example, a Y-axis movement mechanism that moves the table 1 in the front-rear direction (Y-axis direction), a portal frame provided across the table 1, and the portal frame A slider provided on the horizontal beam so as to be slidable in the left-right direction (X-axis direction), and an imaging optical unit 10 and an autofocus laser displacement meter unit 20 provided at the lower end of the slider so as to be movable up and down (Z-axis direction). And an elevating member on which the illumination optical unit 40 is mounted (supported).

  The shape calculation unit 60 performs image processing on the image picked up by the image pickup optical unit 10 to obtain the X and Y axis direction dimensions and shape of the measurement object, and the measurement object obtained by the autofocus laser displacement meter unit 20. The dimension in the Z-axis direction of the object to be measured is obtained from the surface height information. That is, the three-dimensional shape of the object to be measured is obtained.

  In such a configuration, when illumination light is emitted from the illumination light source 41, the illumination light is irradiated to the object to be measured through the collimator lens 42, the mirror 43, the beam splitters 25 and 26, and the front lens 12. The reflected light reflected from the surface of the object to be measured is imaged by the CCD camera 15 via the telecentric optical system 11. Therefore, since the image of the object to be measured is formed by the telecentric optical system 11 and is imaged by the CCD camera 15, the features of the telecentric optical system 11 can be utilized. That is, even in the case of an object having a level difference, the shape in the direction orthogonal to the optical axis of the telecentric optical system 11 can be accurately measured with a wide field of view.

At this time, if the surface of the object to be measured has undulations or irregularities, the autofocus laser displacement meter unit 20 takes an image so that the front focal position of the front lens 12 of the telecentric optical system 11 coincides with the surface of the object to be measured. The optical unit 10, the autofocus laser displacement meter unit 20 and the illumination optical unit 40 are displaced in the vertical direction (Z-axis direction) with respect to the table 1, and the displacement amount is detected by the position detection means 38. Therefore, the position of the object to be measured in the optical axis direction of the telecentric optical system 11 can also be measured.
As a result, while taking advantage of the characteristics of a normal telecentric optical system, the problem can be solved and three-dimensional shape measurement of the object to be measured can be realized.

<Second Embodiment (see FIGS. 2 and 3)>
In the first embodiment, the imaging optical unit 10 and the autofocus laser displacement meter unit 20 are configured so that the surface of the object to be measured matches the front focal position of the front lens 12 of the telecentric optical system 11 by the autofocus laser displacement meter unit 20. Further, the illumination optical unit 40 is integrally displaced with respect to the table 1 in the vertical direction (Z-axis direction), and the amount of displacement is detected by the position detection means 38, whereby the position data of the object to be measured in the Z-axis direction is detected. In the second embodiment, the surface position of the object to be measured is reached when the surface position of the object to be measured reaches a position within the focal depth of the telecentric optical system 11 and deviating from the depth of focus. The relative movement mechanism 50 is operated so that is located at the front focal position of the front lens 12 of the telecentric optical system 11.

Specifically, as shown in FIG. 2, a focus depth determination circuit 39 as a focus depth determination means is added to the autofocus laser displacement meter unit 20.
The focal depth determination circuit 39 determines that the surface position of the measurement object measured by the autofocus laser displacement meter unit 20 has reached a position within the focal depth of the telecentric optical system 11 and a position outside the focal depth. Specifically, as shown in FIG. 3, positions near the focal depth of the telecentric optical system 11 and deviating from the focal depth, that is, determination setting values HSU and HSD are preset in the focal depth determination circuit 39. Yes. The depth-of-focus determination circuit 39 compares the deviation amount detected by the deviation amount detection circuit 36 with the determination setting values HSU and HSD, and when the deviation amount exceeds the determination setting values HSU and HSD, the focus corresponding to the deviation amount. An error signal is given to the servo circuit 37 as a focal depth adjustment command means.

  The servo circuit 37 operates the relative movement mechanism 50 based on the focus error signal from the depth-of-focus determination circuit 39 to relatively move the table 1 and the telecentric optical system 11 in the optical axis direction. That is, the table 1 and the telecentric optical system 11 are relatively moved in the optical axis direction so that the surface position of the object to be measured comes to the front focal position of the front lens 12 of the telecentric optical system 11 (substantially the focal depth central position). .

According to the second embodiment, as shown in FIG. 3, when continuously measuring an object having waviness (undulation) in the vertical direction, the surface position of the object to be measured is changed to a telecentric optical by the focal depth determination circuit 39. When it is determined that the position close to the focal depth of the system 11 and deviating from the focal depth (determination setting values HSU, HSD) is reached, the servo circuit 37 determines the surface position of the object to be measured as the focal point of the telecentric optical system 11. The relative movement mechanism 50 is operated so that the table 1 and the telecentric optical system 11 are moved relative to each other in the optical axis direction so as to come to substantially the center position in the depth (the front focal position of the front lens 12).
Therefore, since the surface position of the object to be measured is maintained in a state where it is kept within the focal depth of the telecentric optical system 11, measurement can be continuously performed.

<Third Embodiment (see FIG. 4)>
In 3rd Embodiment, as shown in FIG. 4, the structure of the telecentric optical system 11 differs from 1st, 2nd embodiment.
In the telecentric optical system 11 according to the third embodiment, the front lens 12 includes at least a first front lens 12A, a second front lens 12B, and a third front lens 12C that are arranged from the object side. Here, parallel light fluxes are formed between the first front lens 12A and the second front lens 12B and between the third front lens 12C and the rear lens 13. The first front lens 12A is configured by a single lens or a bonded lens. Further, the first front lens 12A and the second front lens 12B constitute an afocal optical system.

  The beam splitter 26 of the laser light irradiation optical system 22 is disposed between the first front lens 12A and the second front lens 12B. Accordingly, the laser beam irradiation optical system 22 of the third embodiment is arranged between the collimator lens 23, the beam splitters 24 and 25, the first front lens 12A, and the second front lens 12B, and the laser from the beam splitter 25. And a beam splitter 26 that reflects the light toward the first front lens 12A.

  According to the third embodiment, the first front lens 12A can be used for light collimation, and the remaining second front lens 12B and third front lens 12C can be used to correct aberrations due to imaging of the optical system. Thereby, even if the aperture of the laser beam is increased, the flare of the laser beam and illumination light from the lens surface can be reduced. In addition, when the aperture of the laser beam is increased, the detection accuracy of the focus position is improved, so that more accurate measurement can be realized.

<Modification>
The present invention is not limited to the above-described embodiments, and modifications, improvements and the like within the scope that can achieve the object of the present invention are included in the present invention.
In each of the embodiments described above, a red semiconductor laser is used as the laser light source 21, but if an invisible laser is used instead of the red semiconductor laser, it is possible to prevent a normal observation image from being interrupted.

In each of the above-described embodiments, the double-pinhole method autofocus laser displacement meter is used as the non-contact position measuring means, but is not limited thereto.
For example, a knife edge autofocus laser displacement meter may be used.
Alternatively, the laser light is split into two lights by a beam splitter, one light is reflected by a reference mirror, and the other light is irradiated to the object to be measured through the front lens 12 of the telecentric optical system. The reflected light can be interfered with the reference light reflected by the reference mirror and then received by the detector, and can also be used in an interferometer (Michelson interferometer) or the like.

  In each of the embodiments, the table 1 moves in the Y-axis direction, and the imaging optical unit 10, the autofocus laser displacement meter unit 20, and the illumination optical unit 40 move in the X-axis direction (left-right direction) and Z-axis direction (up-down direction). Although it was a structure, it is not restricted to this. In short, any configuration may be used as long as the table 1, the imaging optical unit 10, the autofocus laser displacement meter unit 20, and the illumination optical unit 40 are relatively moved in the three-dimensional direction.

  INDUSTRIAL APPLICABILITY The present invention can be used for measuring the three-dimensional shape of an object to be measured having a step, such as blade tools, mechanical parts, assembled electronic parts, and the like.

1 ... table,
10: Imaging optical unit,
11 ... Telecentric optical system,
12 ... Front lens,
12A ... 1st front lens,
12B ... Second front lens,
12C ... Third front lens,
13: Rear lens,
14 ... Telecentric aperture,
15 ... CCD camera (imaging means),
20 ... Autofocus laser displacement meter (non-contact position measuring means),
21 ... Laser light source,
22 ... Laser light irradiation optical system,
31: Deviation amount detection unit,
36: Deviation amount detection circuit,
37 ... Servo circuit (relative movement command means, focal depth adjustment command means),
39: Depth of focus determination means,
50: Relative movement mechanism.

Claims (3)

In an image measuring machine that relatively moves a table on which a measurement object is placed and an imaging optical unit with a relative movement mechanism and measures the shape of the measurement object from an image of the measurement object captured by the imaging optical unit ,
The imaging optical unit includes a telecentric optical system having a front lens, a rear lens, and a telecentric stop, and an imaging unit that captures an image of the object to be measured formed by the telecentric optical system.
Using a laser beam, Bei give a non-contact position measuring means for measuring the position along the optical axis of the object surface on the optical axis of the telecentric optical system in a non-contact,
The non-contact position measuring means includes a laser light source, a laser light irradiation optical system for irradiating the measurement object with a laser beam emitted from the laser light source through a front lens of the telecentric optical system, and a surface of the measurement object. A deviation amount detection unit that processes the reflected laser light to detect a deviation amount of the surface of the object to be measured with respect to the focal position of the front lens, and the relative amount so that the deviation amount detected by the deviation amount detection unit is eliminated. A relative movement command means for operating a movement mechanism, and a position detection means for detecting a relative movement amount between the table and the telecentric optical system in the optical axis direction,
The front lens has a first front lens, a second front lens, and a third front lens arranged from the object side,
The first front lens and the second front lens constitute an afocal optical system,
The laser light irradiation optical system includes a collimator lens that collimates laser light emitted from the laser light source, and a beam splitter that reflects the laser light from the collimator lens toward the first front lens. Configured,
The telecentric diaphragm is disposed at a position where a rear focal position of the third front lens and a front focal position of the rear lens coincide;
The image measuring machine , wherein the beam splitter is disposed at a position where a rear focal position of the first front lens and a front focal position of the second front lens coincide with each other . The image measuring machine according to claim 1,
A depth-of-focus determination means for determining that the position of the surface of the object measured by the non-contact position measurement means has reached a position within the depth of focus of the telecentric optical system and deviating from the depth of focus;
When it is determined by the depth-of-focus determination means that the position of the surface of the object to be measured has reached a position close to the focal depth of the telecentric optical system, the position of the surface of the object to be measured is the telecentric optical system. A depth-of-focus adjustment commanding unit that operates the relative movement mechanism to move the table and the telecentric optical system relative to each other in the direction of the optical axis so as to come to a substantially central position of the depth of focus. Image measuring machine. In the image measuring machine according to claim 1 or 2 ,
Before Symbol first front lens is constituted by a single lens or cemented lens, the vision measuring machine, characterized in that.

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