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WO2009043621A1 - Shape measuring instrument with light source control - Google Patents

Shape measuring instrument with light source control Download PDF

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Publication number
WO2009043621A1
WO2009043621A1 PCT/EP2008/059953 EP2008059953W WO2009043621A1 WO 2009043621 A1 WO2009043621 A1 WO 2009043621A1 EP 2008059953 W EP2008059953 W EP 2008059953W WO 2009043621 A1 WO2009043621 A1 WO 2009043621A1
Authority
WO
WIPO (PCT)
Prior art keywords
optical system
laser beam
shape measuring
measuring instrument
photo sensor
Prior art date
Application number
PCT/EP2008/059953
Other languages
French (fr)
Inventor
Satoshi Suzuki
Hiroshi Horiuchi
Kengo Suzuki
Original Assignee
Leica Geosystems Ag
Hexagon Metrology Kabushiki Kaisha
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Leica Geosystems Ag, Hexagon Metrology Kabushiki Kaisha filed Critical Leica Geosystems Ag
Publication of WO2009043621A1 publication Critical patent/WO2009043621A1/en

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/24—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
    • G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
    • G01S17/06—Systems determining position data of a target
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
    • G01S7/481—Constructional features, e.g. arrangements of optical elements
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
    • G01S7/481—Constructional features, e.g. arrangements of optical elements
    • G01S7/4817—Constructional features, e.g. arrangements of optical elements relating to scanning

Definitions

  • the present invention relates to a shape measuring instrument utilizing a non-contact sensor.
  • a conventional shape measuring instrument utilizing a non contact sensor includes a shape measuring device which utilizes a non-contact sensor to measure a shape of a surface of an object and output measurement data of the shape, a computer main body which processes the measurement data outputted from the shape measuring device, and a display device which is controlled by the Computer main body to display an image of the object, particularly a three dimensional image.
  • FIG. 4 is a schematic diagram of an optical system of the shape measuring device.
  • An object to be measured is irradiated with outgoing light emitted from a laser diode 111 via a condenser lens 112, a first mirror 113, a second mirror 114, and a third mirror 115.
  • Returning light reflected by a surface of the object to be measured enters a CCD line sensor portion 118 which is a non-contact sensor via the third mirror 115, the second mirror 114, a fourth mirror 116, and an object lens portion 117.
  • the shape measuring device can scan the surface of the object to be measured by rotating the whole case (not shown) accommodating the optical system about X axis or translating the optical system along Y axis shown in Fig. 4 and rotating the third mirror 115 about Y axis .
  • Fig. 5 is a conceptual diagram showing an optical system for adjusting output of outgoing light from the laser diode 111 in the optical system of the shape measuring device.
  • the optical system mainly comprises a band-pass filter 117b provided on the object lens portion 117, slit members 118b provided on a surface of the CCD line sensor portion 118, and a photo sensor 119 receiving reflected light reflected from a surface glass 118c of the CCD line sensor portion 118 to measure intensity of returning light of the laser beam.
  • An output from the laser diode 111 is controlled by performing feedback control such that intensity of laser beam detected by the photo sensor 119 becomes predetermined intensity.
  • ambient light a great amount of undesired external light
  • the photo sensor 119 can not measure intensity of the returning light of the laser beam accurately. Since the photo sensor 119 can not discriminate ambient light and laser beam incident on the photo sensor 119 from each other, control is made such that an amount of outgoing light of the laser diode 111 lowers. Accordingly, an amount of outgoing light from the laser diode 111 becomes insufficient, which results in impossibility of normal measurement.
  • a band-pass filter 117b is provided outside of an object lens 117a of the object lens portion 117 in order to reduce ambient light.
  • the band-pass filter 117b is an optical filter which allows passage of only returning light having a wavelength of the laser beam emitted from the laser diode 111.
  • the slit members 118b are provided on the outside of the surface glass 118c of the CCD line sensor portion 118 in order to lower the amount of ambient light entering a line sensor 118a of the CCD line sensor portion 118.
  • a slit is formed at a center of the surface glass 118c of the CCD sensor portion 118 by the slit members 118b, and a region of the surface glass 118c except for the slit is covered with the slit members 118b. Therefore, the reflecting face of the CCD sensor portion 118 is reduced so that the amount of ambient light reflected toward the photo sensor 119 is lowered. Thus, the amount of ambient light is limited by the band-pass filter 117b or the slit members 118 and control made such that a lowering of outgoing light of the laser diode 111 is prevented.
  • a width of a slit formed by the slit members 118b must be set to a width of 0.6 mm or more (preferably, 0.8 mm or more), and if the slit width is less than the size of 0.6mm, laser beam is also blocked by the slit members 118b, so that a sufficient amount of laser beam does not reach the line sensor 118a. Accordingly, there is a limit to reduction of the slit width, and if an optical system such as mentioned above is used, the shape measuring instrument, particularly a three dimensional shape measuring instrument, can not be used in a place where a light amount of ambient light is in a range of about 3000 lux to 4000 lux or more. In view of these circumstances, an object of the present invention is to provide a shape measuring instrument, particularly a three dimensional shape measuring instrument, which can be used even under such an environment that intense ambient light is present.
  • a shape measuring instrument comprising: a laser diode emitting laser beam; a first optical system for irradiating a surface of an object to be measured with laser beam emitted from the laser diode; a second optical system for focusing laser beam which is reflected from the surface of the object to be measured; a CCD line sensor portion for detecting a image location of the laser beam from the second optical system; and a photo sensor for measuring intensity of the laser beam from the second optical system, wherein the second optical system includes a beam splitter for branching an optical path for laser beam, and respective laser beams branched by the beam splitter are distributed to the CCD line sensor portion and the photo sensor, and a slit member for forming a slit is provided on a surface of the photo sensor.
  • the beam splitter is a partially transparent mirror.
  • the second optical system is provided with a band-pass filter which allows passage of light with wavelength of outgoing light from the laser diode only.
  • the shape measuring instrument described in claim 1 is configured such that the second optical system includes the beam splitter for branching an optical path for a laser beam and respective laser beams branched by the beam splitter are distributed to the CCD line sensor portion and the photo sensor, and the slit member for forming a slit is provided on the surface of the photo sensor.
  • Intensity of returning light distributed to the CCD line sensor portion and intensity of the returning light distributed to the photo sensor can be determined by characteristics of the beam splitter. Therefore, the intensity of returning light distributed to the photo sensor can be determined arbitrarily and a width of the slit formed by the slit member provided on the surface of the photo sensor can be narrowed sufficiently. Accordingly, even if the slit width of the photo sensor is made narrower than that in the conventional shape measuring instrument so that, even if ambient light incident on the photo sensor is reduced sufficiently, the light amount of returning light distributed to the CCD line sensor portion is not reduced. As a result, the shape measuring instrument can be used even in a place where a light amount of ambient light is in a range of about 3000 lux to 4000 lux or more.
  • the partially transparent mirror is used as the beam splitter.
  • the partially transparent mirror is relatively inexpensive, so that increase of manufacturing cost of the shape measuring instrument caused by providing the beam splitter is limited.
  • the second optical system is provided with the band-pass filter which allows passage of light having a wavelength of outgoing light from the laser diode only. Since ambient light incident on the photo sensor is reduced by the band-pass filter, intensity of outgoing light from the laser diode can be measured more accurately by the photo sensor.
  • An optical system 1 of a shape measuring device of a measuring instrument includes a laser diode 2 emitting laser beam, a first optical system for irradiating a surface of an object to be measured with laser beam emitted from the laser diode 2, a second optical system for focusing laser beam which is reflected from the surface of the object to be measured, a CCD line sensor portion 13 for detecting a image location of laser beam from the second optical system, and a photo sensor 12 for measuring intensity of laser beam from the second optical system, where the second optical system has a partially transparent mirror 11 which is a beam splitter for branching an optical path for laser beam, and respective laser beams branched by the partially transparent mirror 11 are distributed to the CCD line sensor portion 13 and the photo sensor 12, and slit members 12a for forming a slit are provided on a surface of the photo sensor 12 .
  • the abovementioned first optical system is configured to include a beam expander 3, a first mirror 4 and a second mirror 5, and the abovementioned second optical system is configured to include a third mirror 7, a fourth mirror 8, a fifth mirror 9, an object lens portion 10, and the partially transparent mirror 11.
  • the shape measuring instrument is mainly provided with a shape measuring device which uses the CCD line sensor portion 13 to measure a shape of a surface of an object to be measured and output data of the measurement, a Computer main body which processes the measurement data outputted from the shape measuring device, and a display device which displays a an image of the object to be measured under control of the Computer main body.
  • Fig. 3 shows a measurement principle of shape measuring instrument.
  • a surface of an object to be measured is irradiated with laser beam emitted from the laser diode 2, and returning light reflected by the surface of the object to be measured is concentrated by an object lens 10a of the object lens portion 10 to be focused on a line sensor 13a of the CCD line sensor portion 13.
  • An image location of the returning light measured by the line sensor 13a is outputted from the shape measuring device as measurement data.
  • the computer main body utilizes a triangle measurement principle used for distance measurement to calculate a shape, particularly a three dimensional shape, of the surface of the object to be measured based upon the measurement data.
  • Fig. 1 is a schematic perspective diagram showing an optical system of the shape measuring device of the shape measuring instrument according to the present embodiment.
  • the laser diode 2 is configured such that intensity of outgoing light from the laser diode 2 is controlled according to intensity of laser beam measured by the photo sensor 12 described later in a feedback manner.
  • a surface of an object to be measured is irradiated with the outgoing light from the laser diode 2 through the first optical system.
  • a beam expander 3 is an optical system for maintaining a small spot such that a laser beam diameter falls within a measurement distance range, and the first mirror 4 and the second mirror 5 are provided for changing a direction of laser beam.
  • the second mirror 5 is provided at one end of a rotating shaft of a swinging motor 6, and it is rotated about Y axis shown in Fig. 1.
  • An irradiation range of laser beam to a surface of an object to be measured can be moved in a horizontal direction in Fig. 1 according to rotation of the second mirror 5.
  • the third mirror 7 described later is also provided at the other end of the rotating shaft of the swinging motor 6, and it is rotated at the same angle as that of the second mirror 5.
  • the abovementioned optical system of the shape measuring device can perform scanning in a vertical direction of a surface of an object to be measured by rotating the whole case (not shown) accommodating the optical system about X axis or translating the optical system along Y axis shown in Fig. 1.
  • the third mirror 7, the fourth mirror 8, and the fifth mirror 9 are provided for changing the direction of the laser beam which is returning light, and the object lens portion 10 is disposed so as to concentrate returning light and focus the same on the line sensor 13a of the CCD line sensor portion 13.
  • the third mirror 7 is rotated about the Y axis shown in Fig. 1 by the swinging motor 6, and an incident angle of returning light of laser beam reflected on the surface of the object to be measured is provided to the third mirror 7 according to an irradiation angle of laser beam to the surface of the object to be measured by linkage with the second mirror 5.
  • the object lens portion 10 comprises the object lens 10a and a band-pass filter 10b.
  • the band-pass filter 10b is an optical filter which allows transmission of returning light having a wavelength of laser light emitted from the laser diode 2 only.
  • the second optical system has the partially transparent mirror 11.
  • the partially transparent mirror 11 is a beam splitter for branching laser beam which is returning light having passed through the object lens portion 10. Reflected light reflected by the partially transparent mirror 11 is distributed to the CCD line sensor portion 13, while transmission light is distributed to the photo sensor 12. Since the partially transparent mirror 11 in the present embodiment has a reflectance of 90% and a transmissivity of 10%, 90% of the returning light is distributed to the CCD line sensor portion 13, while 10% of the returning light is distributed to the photo sensor 12.
  • the CCD line sensor portion 13 has the line sensor 13a for measuring an image location of returning light.
  • the CCD line sensor portion 13 is disposed beside the partially transparent mirror 11, and it is disposed such that reflected light from the partially transparent mirror 11 is focused on the line sensor 13a.
  • the photo sensor 12 is provided on a surface thereof with a pair of slit members 12a so that a slit is formed on a surface of the photo sensor 12 by the slit members 12a.
  • the slit members 12a are provided such that the slit extends along a moving direction of returning light to the photo sensor 12.
  • a width of the slit can be set to about 0.1 mm or less, so that it becomes extremely narrow such as about 1/6 to 1/8 of a width of a slit formed on a surface of the conventional CCD line sensor portion.
  • the second optical system has the partially transparent mirror 11 which is the beam splitter for branching the optical path for laser beam, respective laser beams branched by the partially transparent mirror 11 are distributed to the CCD line sensor portion 13 and the photo sensor 12, and the slit members 12a for forming a slit are provided on the surface of the photo sensor 12.
  • Intensity of returning light distributed to the CCD line sensor portion 13 and intensity of the returning light distributed to the photo sensor 12 can be determined according to the transmissivity and the reflectivity of the partially transparent mirror 11 which is the beam splitter. Therefore, the intensity of returning light distributed to the photo sensor 12 can be determined freely, and the width of the slit formed by the slit members 12a provided on the surface of the photo sensor 12 can be narrowed sufficiently. Accordingly, even if the slit width of the photo sensor 12 is narrowed as compared with that in the conventional shape measuring instrument so that ambient light incident on the photo sensor 12 is reduced sufficiently, the light amount of returning light distributed to the CCD line sensor portion 13 is not reduced. As a result, the shape measuring instrument can be used even in a place where a light amount of ambient light is in a range of about 3000 lux to 4000 lux or more.
  • the partially transparent mirror 11 is used as the beam splitter.
  • the partially transparent mirror is relatively inexpensive, so that an increase of manufacturing cost of the shape measuring instrument due to providing the beam splitter is limited.
  • the second optical system is provided with the band-pass filter 10b which allows passage of light having a wavelength of outgoing light from the laser diode 2 only. Since ambient light incident on the photo sensor 12 is reduced by the band-pass filter 10b, intensity of outgoing light from the laser diode 2 can be measured more accurately by the photo sensor 12.
  • Fig. 1 is a schematic diagram of an optical system of a shape measuring device of a shape measuring instrument according to an embodiment of the present invention
  • Fig. 2 is a conceptual diagram showing an optical system for adjusting output of outgoing light from a laser diode 2 in an optical system of the shape measuring device shown in Fig. 1;
  • Fig. 3 is an explanatory diagram showing a measurement principle of the shape measuring instrument shown in Fig. 1 ;
  • Fig. 4 is a schematic diagram of an optical system of a shape measuring device of a conventional shape measuring instrument
  • Fig. 5 is a schematic diagram showing an optical system for performing output adjustment of outgoing light from a laser diode 111 in the optical system of the shape measuring device shown in Fig. 4;
  • Fig. 6 is an enlarged explanatory diagram of a CCD line sensor portion 118 in the optical system of the shape measuring device shown in Fig. 4.
  • band-pass filter 11 partially transparent mirror

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • General Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Length Measuring Devices By Optical Means (AREA)

Abstract

A shape measuring instrument which can be used even under an environment where intense ambient light is present comprises an optical system (1) of a shape measuring device which includes a laser dio de (2) emitting laser beam, a first optical system for irradiating an object to be measured with laser beam emitted, a second optical system for focusing laser beam which is reflected from the object to be measured, a CCD line sensor portion (13) for detecting a image location of laser beam from the second optical system, and a photo sensor (12) for meas uring intensity of laser beam from the second optical System, and respective laser beams branched by the partially transparent mirror (11) of the second optical system are d istributed to the CCD line sensor portion (13) and the photo sensor (12), and slit members (12a) are provided on a surface of the photo sensor (12).

Description

SHAPE MEASURING INSTRUMENT WITH LIGHT SOURCE CONTROL
The present invention relates to a shape measuring instrument utilizing a non-contact sensor.
A conventional shape measuring instrument utilizing a non contact sensor includes a shape measuring device which utilizes a non-contact sensor to measure a shape of a surface of an object and output measurement data of the shape, a computer main body which processes the measurement data outputted from the shape measuring device, and a display device which is controlled by the Computer main body to display an image of the object, particularly a three dimensional image.
FIG. 4 is a schematic diagram of an optical system of the shape measuring device. An object to be measured is irradiated with outgoing light emitted from a laser diode 111 via a condenser lens 112, a first mirror 113, a second mirror 114, and a third mirror 115. Returning light reflected by a surface of the object to be measured enters a CCD line sensor portion 118 which is a non-contact sensor via the third mirror 115, the second mirror 114, a fourth mirror 116, and an object lens portion 117. Incidentally, the shape measuring device can scan the surface of the object to be measured by rotating the whole case (not shown) accommodating the optical system about X axis or translating the optical system along Y axis shown in Fig. 4 and rotating the third mirror 115 about Y axis .
Fig. 5 is a conceptual diagram showing an optical system for adjusting output of outgoing light from the laser diode 111 in the optical system of the shape measuring device. The optical system mainly comprises a band-pass filter 117b provided on the object lens portion 117, slit members 118b provided on a surface of the CCD line sensor portion 118, and a photo sensor 119 receiving reflected light reflected from a surface glass 118c of the CCD line sensor portion 118 to measure intensity of returning light of the laser beam. An output from the laser diode 111 is controlled by performing feedback control such that intensity of laser beam detected by the photo sensor 119 becomes predetermined intensity.
However, when a great amount of undesired external light (hereinafter, called "ambient light") enters the surface glass 118c of the CCD line sensor portion 118, the photo sensor 119 can not measure intensity of the returning light of the laser beam accurately. Since the photo sensor 119 can not discriminate ambient light and laser beam incident on the photo sensor 119 from each other, control is made such that an amount of outgoing light of the laser diode 111 lowers. Accordingly, an amount of outgoing light from the laser diode 111 becomes insufficient, which results in impossibility of normal measurement.
Therefore, a band-pass filter 117b is provided outside of an object lens 117a of the object lens portion 117 in order to reduce ambient light. The band-pass filter 117b is an optical filter which allows passage of only returning light having a wavelength of the laser beam emitted from the laser diode 111. Further, the slit members 118b are provided on the outside of the surface glass 118c of the CCD line sensor portion 118 in order to lower the amount of ambient light entering a line sensor 118a of the CCD line sensor portion 118. A slit is formed at a center of the surface glass 118c of the CCD sensor portion 118 by the slit members 118b, and a region of the surface glass 118c except for the slit is covered with the slit members 118b. Therefore, the reflecting face of the CCD sensor portion 118 is reduced so that the amount of ambient light reflected toward the photo sensor 119 is lowered. Thus, the amount of ambient light is limited by the band-pass filter 117b or the slit members 118 and control made such that a lowering of outgoing light of the laser diode 111 is prevented.
However, in the abovementioned method where the slit is formed on the surface glass 118c of the CCD line sensor portion 119 by the slit members 118b, there is such a problem that a light amount of ambient light reflected by the surface glass 118c can not be reduced sufficiently. As shown in Fig. 6, this results from the fact that the distance between the surface glass 118c including the CCD line sensor portion 118 and the line sensor 118a is about 2mm and since the returning light is concentrated by the object lens 117a, a converging width of about 0.6mm of laser beam must be secured on a surface position of the surface glass 118c. Therefore, a width of a slit formed by the slit members 118b must be set to a width of 0.6 mm or more (preferably, 0.8 mm or more), and if the slit width is less than the size of 0.6mm, laser beam is also blocked by the slit members 118b, so that a sufficient amount of laser beam does not reach the line sensor 118a. Accordingly, there is a limit to reduction of the slit width, and if an optical system such as mentioned above is used, the shape measuring instrument, particularly a three dimensional shape measuring instrument, can not be used in a place where a light amount of ambient light is in a range of about 3000 lux to 4000 lux or more. In view of these circumstances, an object of the present invention is to provide a shape measuring instrument, particularly a three dimensional shape measuring instrument, which can be used even under such an environment that intense ambient light is present.
According to an aspect of the present invention, there is provided a shape measuring instrument comprising: a laser diode emitting laser beam; a first optical system for irradiating a surface of an object to be measured with laser beam emitted from the laser diode; a second optical system for focusing laser beam which is reflected from the surface of the object to be measured; a CCD line sensor portion for detecting a image location of the laser beam from the second optical system; and a photo sensor for measuring intensity of the laser beam from the second optical system, wherein the second optical system includes a beam splitter for branching an optical path for laser beam, and respective laser beams branched by the beam splitter are distributed to the CCD line sensor portion and the photo sensor, and a slit member for forming a slit is provided on a surface of the photo sensor.
It is further preferable in the shape measuring instrument according to the present invention that the beam splitter is a partially transparent mirror.
It is further preferable in the shape measuring instrument according to the present invention that the second optical system is provided with a band-pass filter which allows passage of light with wavelength of outgoing light from the laser diode only. The shape measuring instrument described in claim 1 is configured such that the second optical system includes the beam splitter for branching an optical path for a laser beam and respective laser beams branched by the beam splitter are distributed to the CCD line sensor portion and the photo sensor, and the slit member for forming a slit is provided on the surface of the photo sensor.
Intensity of returning light distributed to the CCD line sensor portion and intensity of the returning light distributed to the photo sensor can be determined by characteristics of the beam splitter. Therefore, the intensity of returning light distributed to the photo sensor can be determined arbitrarily and a width of the slit formed by the slit member provided on the surface of the photo sensor can be narrowed sufficiently. Accordingly, even if the slit width of the photo sensor is made narrower than that in the conventional shape measuring instrument so that, even if ambient light incident on the photo sensor is reduced sufficiently, the light amount of returning light distributed to the CCD line sensor portion is not reduced. As a result, the shape measuring instrument can be used even in a place where a light amount of ambient light is in a range of about 3000 lux to 4000 lux or more.
In the shape measuring instrument according to the present invention described in claim 2, the partially transparent mirror is used as the beam splitter. The partially transparent mirror is relatively inexpensive, so that increase of manufacturing cost of the shape measuring instrument caused by providing the beam splitter is limited. In the shape measuring instrument according to the present invention described in claim 3, the second optical system is provided with the band-pass filter which allows passage of light having a wavelength of outgoing light from the laser diode only. Since ambient light incident on the photo sensor is reduced by the band-pass filter, intensity of outgoing light from the laser diode can be measured more accurately by the photo sensor.
An embodiment of the present invention will be explained below with reference to Fig. 1 to Fig. 3. An optical system 1 of a shape measuring device of a measuring instrument according to the present embodiment includes a laser diode 2 emitting laser beam, a first optical system for irradiating a surface of an object to be measured with laser beam emitted from the laser diode 2, a second optical system for focusing laser beam which is reflected from the surface of the object to be measured, a CCD line sensor portion 13 for detecting a image location of laser beam from the second optical system, and a photo sensor 12 for measuring intensity of laser beam from the second optical system, where the second optical system has a partially transparent mirror 11 which is a beam splitter for branching an optical path for laser beam, and respective laser beams branched by the partially transparent mirror 11 are distributed to the CCD line sensor portion 13 and the photo sensor 12, and slit members 12a for forming a slit are provided on a surface of the photo sensor 12 . Incidentally, in the present embodiment, the abovementioned first optical system is configured to include a beam expander 3, a first mirror 4 and a second mirror 5, and the abovementioned second optical system is configured to include a third mirror 7, a fourth mirror 8, a fifth mirror 9, an object lens portion 10, and the partially transparent mirror 11.
The shape measuring instrument according to the present embodiment is mainly provided with a shape measuring device which uses the CCD line sensor portion 13 to measure a shape of a surface of an object to be measured and output data of the measurement, a Computer main body which processes the measurement data outputted from the shape measuring device, and a display device which displays a an image of the object to be measured under control of the Computer main body.
Fig. 3 shows a measurement principle of shape measuring instrument. A surface of an object to be measured is irradiated with laser beam emitted from the laser diode 2, and returning light reflected by the surface of the object to be measured is concentrated by an object lens 10a of the object lens portion 10 to be focused on a line sensor 13a of the CCD line sensor portion 13. An image location of the returning light measured by the line sensor 13a is outputted from the shape measuring device as measurement data. The computer main body utilizes a triangle measurement principle used for distance measurement to calculate a shape, particularly a three dimensional shape, of the surface of the object to be measured based upon the measurement data.
Fig. 1 is a schematic perspective diagram showing an optical system of the shape measuring device of the shape measuring instrument according to the present embodiment. The laser diode 2 is configured such that intensity of outgoing light from the laser diode 2 is controlled according to intensity of laser beam measured by the photo sensor 12 described later in a feedback manner. A surface of an object to be measured is irradiated with the outgoing light from the laser diode 2 through the first optical system. In the first optical system, a beam expander 3 is an optical system for maintaining a small spot such that a laser beam diameter falls within a measurement distance range, and the first mirror 4 and the second mirror 5 are provided for changing a direction of laser beam.
The second mirror 5 is provided at one end of a rotating shaft of a swinging motor 6, and it is rotated about Y axis shown in Fig. 1. An irradiation range of laser beam to a surface of an object to be measured can be moved in a horizontal direction in Fig. 1 according to rotation of the second mirror 5. The third mirror 7 described later is also provided at the other end of the rotating shaft of the swinging motor 6, and it is rotated at the same angle as that of the second mirror 5. Incidentally, the abovementioned optical system of the shape measuring device according to the present embodiment can perform scanning in a vertical direction of a surface of an object to be measured by rotating the whole case (not shown) accommodating the optical system about X axis or translating the optical system along Y axis shown in Fig. 1.
In the second optical system for focusing laser beam which is reflected light from a surface of an object to be measured, the third mirror 7, the fourth mirror 8, and the fifth mirror 9 are provided for changing the direction of the laser beam which is returning light, and the object lens portion 10 is disposed so as to concentrate returning light and focus the same on the line sensor 13a of the CCD line sensor portion 13. As described above, the third mirror 7 is rotated about the Y axis shown in Fig. 1 by the swinging motor 6, and an incident angle of returning light of laser beam reflected on the surface of the object to be measured is provided to the third mirror 7 according to an irradiation angle of laser beam to the surface of the object to be measured by linkage with the second mirror 5.
The object lens portion 10 comprises the object lens 10a and a band-pass filter 10b. The band-pass filter 10b is an optical filter which allows transmission of returning light having a wavelength of laser light emitted from the laser diode 2 only.
Further, the second optical system has the partially transparent mirror 11. The partially transparent mirror 11 is a beam splitter for branching laser beam which is returning light having passed through the object lens portion 10. Reflected light reflected by the partially transparent mirror 11 is distributed to the CCD line sensor portion 13, while transmission light is distributed to the photo sensor 12. Since the partially transparent mirror 11 in the present embodiment has a reflectance of 90% and a transmissivity of 10%, 90% of the returning light is distributed to the CCD line sensor portion 13, while 10% of the returning light is distributed to the photo sensor 12.
The CCD line sensor portion 13 has the line sensor 13a for measuring an image location of returning light. The CCD line sensor portion 13 is disposed beside the partially transparent mirror 11, and it is disposed such that reflected light from the partially transparent mirror 11 is focused on the line sensor 13a. The photo sensor 12 is provided on a surface thereof with a pair of slit members 12a so that a slit is formed on a surface of the photo sensor 12 by the slit members 12a. The slit members 12a are provided such that the slit extends along a moving direction of returning light to the photo sensor 12. Since a laser spot is focused on a PD element, a width of the slit can be set to about 0.1 mm or less, so that it becomes extremely narrow such as about 1/6 to 1/8 of a width of a slit formed on a surface of the conventional CCD line sensor portion.
Operation effect of the present embodiment will be explained below.
In the shape measuring instrument according to the present embodiment, the second optical system has the partially transparent mirror 11 which is the beam splitter for branching the optical path for laser beam, respective laser beams branched by the partially transparent mirror 11 are distributed to the CCD line sensor portion 13 and the photo sensor 12, and the slit members 12a for forming a slit are provided on the surface of the photo sensor 12.
Intensity of returning light distributed to the CCD line sensor portion 13 and intensity of the returning light distributed to the photo sensor 12 can be determined according to the transmissivity and the reflectivity of the partially transparent mirror 11 which is the beam splitter. Therefore, the intensity of returning light distributed to the photo sensor 12 can be determined freely, and the width of the slit formed by the slit members 12a provided on the surface of the photo sensor 12 can be narrowed sufficiently. Accordingly, even if the slit width of the photo sensor 12 is narrowed as compared with that in the conventional shape measuring instrument so that ambient light incident on the photo sensor 12 is reduced sufficiently, the light amount of returning light distributed to the CCD line sensor portion 13 is not reduced. As a result, the shape measuring instrument can be used even in a place where a light amount of ambient light is in a range of about 3000 lux to 4000 lux or more.
Further, in the shape measuring instrument according to the present embodiment, the partially transparent mirror 11 is used as the beam splitter. The partially transparent mirror is relatively inexpensive, so that an increase of manufacturing cost of the shape measuring instrument due to providing the beam splitter is limited.
Further, in the shape measuring instrument according to the present embodiment, the second optical system is provided with the band-pass filter 10b which allows passage of light having a wavelength of outgoing light from the laser diode 2 only. Since ambient light incident on the photo sensor 12 is reduced by the band-pass filter 10b, intensity of outgoing light from the laser diode 2 can be measured more accurately by the photo sensor 12.
Fig. 1 is a schematic diagram of an optical system of a shape measuring device of a shape measuring instrument according to an embodiment of the present invention;
Fig. 2 is a conceptual diagram showing an optical system for adjusting output of outgoing light from a laser diode 2 in an optical system of the shape measuring device shown in Fig. 1; Fig. 3 is an explanatory diagram showing a measurement principle of the shape measuring instrument shown in Fig. 1 ;
Fig. 4 is a schematic diagram of an optical system of a shape measuring device of a conventional shape measuring instrument;
Fig. 5 is a schematic diagram showing an optical system for performing output adjustment of outgoing light from a laser diode 111 in the optical system of the shape measuring device shown in Fig. 4; and
Fig. 6 is an enlarged explanatory diagram of a CCD line sensor portion 118 in the optical system of the shape measuring device shown in Fig. 4.
Explanation of Reference Numerals
1 : optical system of shape measuring device
2, 111: laser diode 3 : beam expander
4 : first mirror
5: second mirror
6: swinging motor
7 : third mirror 8: fourth mirror
9: fifth mirror
10, 117: object lens portion
10a, 117a: object lens
10b, 117b: band-pass filter 11: partially transparent mirror
12, 119: photo sensor 12a: slit member
13, 118: CCD line sensor portion 13a, 118a: line sensor 112: condenser lens portion
113: first mirror
114: second mirror
115: third mirror
116: fourth mirror 118b: slit member
118c: surface glass

Claims

1. A shape measuring instrument, particularly for measuring a three dimensional shape, comprising: a laser diode (2,111) for emitting a laser beam, a first optical system irradiating a surface of an object to be measured with the laser beam emitted from the laser diode (2,111), a second optical system for focusing the laser beam reflected from the surface of the object to be measured, a CCD line sensor (13a, 118a) for detecting the laser beam from the second optical system; and a photo sensor (12,119) for measuring intensity of the laser beam from the second optical system, wherein the second optical system includes a beam splitter for branching an optical path of the laser beam and distributing the laser beam to the CCD line sensor (13a, 118a) and to the photo sensor (12,119), and a slit member (12a, 118b) for forming a slit is provided on a surface of the photo sensor (12,119) .
2. The shape measuring instrument according to claim 1, wherein the beam splitter is a partially transparent mirror .
3. The shape measuring instrument according to claim 1 or 2, wherein the second optical system is provided with a band-pass filter which allows passage of light of wavelength of outgoing light from the laser diode (2,111) only.
PCT/EP2008/059953 2007-10-05 2008-07-29 Shape measuring instrument with light source control WO2009043621A1 (en)

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JP2007262472A JP2009092479A (en) 2007-10-05 2007-10-05 Three-dimensional shape measuring instrument
JP2007-262472 2007-10-05

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