JP2017519188A - Three-dimensional scanner for signal acquisition with dichroic beam splitter - Google Patents

Abstract

A laser scanner which is a device for optically scanning and measuring the surrounding environment, and passes through a light emitting device that emits a light beam using a rotary mirror and a light receiving lens having a rotary mirror and an optical axis, and then enters the surrounding environment of the laser scanner. A receiver for receiving a received beam reflected by an object. This laser scanner is arranged on the optical axis of the light-receiving lens and is equipped with a color camera that captures a color image of the surrounding environment of the laser scanner, and further, a dichroic beam splitter and thermal energy, ultraviolet radiation, millimeter wave radiation, or X A system comprising an energy detector for detecting line radiation is provided. The apparatus further comprises a control and evaluation unit that derives the distance to the object for a number of measurement points and links it to the color image and the data sensed by the energy detector.

Description

(Cross-reference of related applications)
This application is based on US provisional patent application No. 61/299166 dated Jan. 28, 2010 and German patent application No. 10 2009 055988.4 dated Nov. 20, 2009. It is a national phase application of patent application No. PCT / EP2010 / 006867, but it is accompanied by a priority claim based on US patent application No. 13/510020 dated June 15, 2012, all of which are hereby incorporated by reference. It shall be carried into this application.

  The present invention relates to an apparatus for optically scanning and measuring an ambient environment.

  For example, according to an apparatus known from Patent Document 1 and equipped with a laser scanner, the surrounding environment of the laser scanner can be optically scanned and measured. The rotating rotary mirror is composed of a polished plate (polished plate) of a metal rotor, and changes the direction of both the emitted beam and the received beam. The collimator of the light emitter sits in the center of the light receiving lens. The light receiving lens supplies a light receiving beam onto a light receiver disposed behind the light receiving lens and disposed on the optical axis. In order to acquire further information, a line scan camera that captures RGB signals is mounted on the laser scanner, so that various measurement points constituting the scan can be complemented with color information.

US Patent Application Publication No. 2010/0134596 US Pat. No. 7,368,292

  The basis of embodiments of the present invention is to create an alternative to the types of devices described above.

  Since the light receiver and the color camera capture the surrounding environment from the same viewing angle and on the same side of the rotary mirror, the color camera is placed on the optical axis of the light receiving lens, and when viewed from the rotary mirror, they are on the same side. There is an advantage that the parallax can be almost completely eliminated. The same mechanism can be used for the rotary mirror. The usage side of the rotary mirror is the same. The light receiving beam reflected by the rotary mirror travels parallel to the optical axis of the light receiving lens and continuously enters the light receiving lens. Since the light receiving lens replaces the light receiver, there is no change in the shadowing effect. In order to be able to send the emitted beam again, a launch mirror (sending mirror) that is reflective for the emitted beam and transparent for the color camera is provided in front of the color camera.

  Due to the fact that a rear mirror that reflects the light receiving beam refracted by the light receiving lens in the direction of the light receiving lens is provided behind the light receiving lens on the optical axis, the available space can be used more suitably. In order to complement this “bending optical system”, a central mirror that reflects the received light beam in the direction of the rear mirror is provided between the light receiving lens and the rear mirror. A preferred form of this mirror is a form that supports focusing, and in this form, the focal length of the non-bending optical system can still be extended (increased). The central mirror reduces the intensity from the near field compared to the far field, so it can be used for near field correction as well as an additional mask. Space is further saved by arranging the light receiver along the radial direction with respect to the optical axis of the light receiving lens in the cylindrical coordinate system defined by the optical axis.

  When the structure of the rotor is a hybrid structure, that is, a multi-element structure made of various materials, a relatively short structure, that is, a structure in which balance is maintained despite the inclination of the rotary mirror can be obtained. A combination of a metal holder, a rotary mirror made of coated glass, and a plastic housing can be used, but other combinations can also be used. The housing allows protection against unintentional contact while allowing balancing with a mass dominant holder. The glue between the rotor components can balance the temperature coefficient difference of expansion without compromising dynamic behavior.

  By providing a dichroic beam splitter on the feedback light path to the light receiver, an energy signal such as electromagnetic radiation can be branched and received by a corresponding detector, for example.

  Hereinafter, the present invention will be described in more detail based on exemplary embodiments depicted in the drawings.

It is a fragmentary sectional view of a laser scanner. It is a schematic diagram of a laser scanner. It is a perspective view of a rotor holder. It is a fragmentary sectional view of a laser scanner. It is a fragmentary sectional view of a laser scanner. It is a fragmentary sectional view of a laser scanner.

1 and 2 show a laser scanner 10 which is an apparatus for optically scanning and measuring the surrounding environment of the laser scanner 10. The laser scanner 10 has a measuring head 12 and a base 14. The measuring head 12 is mounted on a base 14 and is a unit that can be rotated around a vertical axis. The measuring head 12 has a rotary mirror 16, and the mirror 16 can be rotated around a horizontal axis. The intersection of those two pivot shafts is referred to as a center C ₁₀ of the laser scanner 10.

  The measuring head 12 is further provided with a light emitter 17 that emits a light beam 18. The emission beam 18 may be a laser beam belonging to a wavelength range of about 340 to 1600 nm, for example, a laser beam of less than 790 nm, 905 nm, or 400 nm. It is also possible to use another electromagnetic wave, for example an electromagnetic wave having a longer wavelength. The emission beam 18 is amplitude-modulated with, for example, a sine wave or square wave modulation signal. The emitted light beam 18 is radiated toward the rotary mirror 16 by the light emitter 17, where it is redirected and emitted to the surrounding environment. The received light beam 20 is a beam reflected by the object O or scattered in some other form in the surrounding environment, and is captured again by the rotary mirror 16 and redirected to the light receiver 21 side. The directions of the emitted light beam 18 and the received light beam 20 are derived from the angular positions of the rotary mirror 16 and the measuring head 12, and these angular positions are aligned by a single encoder. Depends on the position.

  The control / evaluation unit 22 has data connection means for the light emitter 17 and the light receiver 21 in the measurement head 12, and the constituent parts of the unit 22 are arranged outside the measurement head 12 by using it. For example, a computer connected to the base 14 may be used. The control / evaluation unit 22 derives the distance d between the laser scanner 10 and the object O side illuminated point with respect to a large number of measurement points X from the propagation times of the emitted light beam 18 and the received light beam 20. For this purpose, the phase shift between these two light beams 18 and 20 is derived and evaluated.

Scanning is performed along a circle due to the relatively quick rotation of the mirror 16. Since the measuring head 12 is rotated relatively slowly with respect to the base 14, the entire space is scanned step by step by a plurality of circles. A set of measurement points X constituting such measurement is called a scan. For such a scan, the origin of the local stationary reference system is defined by the center C ₁₀ of the laser scanner 10. The base 14 is stationary in this local stationary reference system.

Each measurement point X, in addition to the distance d to the center C ₁₀ of the laser scanner 10, and a luminance information and the like is also derived by the control and evaluation unit 22. This luminance value is a gray tone value, and is derived, for example, by integrating the signal of the optical receiver 21 subjected to band-pass filtering and amplification over the measurement period assigned to the measurement point X. Depending on the application, it may be desirable to have color information in addition to this graytone value. Therefore, the laser scanner 10 is also provided with a color camera 23, which is also connected to the control / evaluation unit 22. The color camera 23, which can be constituted by a CCD camera or a CMOS camera, generates a three-dimensional signal in the color space, for example, an RGB signal, for a two-dimensional image in the real space. The control / evaluation unit 22 is a unit that links a three-dimensional scan in the real space by the laser scanner 10 with a two-dimensional color image by the color camera 23 in the real space. This is called “mapping”. Linking is performed on an image-by-image basis for every captured color image to give each measurement point X that makes up the scan a color within the RGB share as a final result, i.e. to color the scan.

  Details of the measurement head 12 will be described below.

The light receiving beam 20 reflected by the rotary mirror 16 is incident on the plano-convex spherical light receiving lens 30, which has a substantially hemispherical shape in the embodiments of the present invention. Its optical axis A of the light receiving lens 30 is directed to the center C ₁₀ of the laser scanner. The convex side of the light receiving lens 30 that is highly refracted faces the rotary mirror 16 side. The color camera 23 is arranged on the optical axis A on the same side as the light receiving lens 30 when viewed from the rotary mirror 16. In the embodiments of the present invention, the color camera 23 is disposed at a point of the light receiving lens 30 closest to the rotary mirror 16. It is also possible to fix the color camera 23 on an untreated surface of the light receiving lens 30, for example, to paste on the surface, or to arrange the color camera 23 in an appropriate recess provided in the light receiving lens 30.

  In front of the color camera 23, that is, near the rotary mirror 16, a dichroic launch mirror 32, that is, a mirror 32 that transmits visible light and reflects red laser light in the embodiments of the present invention is arranged. Thus, the launch mirror 32 is transparent to the color camera 23 and, in turn, provides a clear view towards the rotary mirror 16 by this mirror 32. The reason why the launch mirror 32 is at an angle with respect to the optical axis A of the light receiving lens 30 is to allow the light emitter 17 to be disposed beside the light receiving lens 30. This emitter 17 comprising a laser diode and a collimator radiates the emitted beam 18 onto a launch mirror 32 which is then projected from the mirror 32 onto the rotary mirror 16. In capturing a color image, the rotary mirror 16 is rotated at a relatively low speed and step by step. Conversely, when capturing a scan, the rotary mirror 16 is rotated relatively quickly (for example, 100 cps) and continuously. The mechanism of the rotary mirror 16 remains the same.

  Since the color camera 23 is disposed on the optical axis A of the light receiving lens 30, there is virtually no parallax between the scanned and color images. In the known laser scanner, since the color camera 23 and its connection means, for example, the light emitter 17 and its connection means are arranged instead of the flexible printed circuit board, the light receiving lens 30 caused by the color camera 23 and the emission mirror 32 is provided. The shadowing effect does not change or remains insignificant.

  On the one hand, the laser scanner 10 is provided with a “bending optical system” in order to localize a distant measurement point X having a relatively long focal length and, on the other hand, a relatively narrow space. . For this purpose, a mask 42 is disposed on the optical axis A and behind the light receiving lens 30, and the mask is directed coaxially with the optical axis A. A mask 42 is disposed radially inward (that is, on the side indicated by the optical axis A), and there is a relatively wide open area through which the received light beam 20 reflected by the distant object O passes without hindrance. On the other hand, the mask 42 arranged on the outer side in the radial direction has a relatively narrow shadow region, and the intensity of the received beam 20 reflected by the nearby object O is reduced there. It will become a thing.

  The rear mirror 43 is disposed behind the mask 42 on the optical axis A, and this mirror is flat and orthogonal to the optical axis A. The rear mirror 43 reflects the received light beam 20 refracted by the light receiving lens 30 and makes it incident on the central mirror 44. The central mirror 44 is arranged on the optical axis A in the center of the mask 42 and is subjected to shadowing by the color camera 23 and the launch mirror 32. The central mirror 44 is an aspherical mirror, and acts as a negative lens, i.e., a lens that extends the focal length, or as a near-field correction lens, i.e., a lens that shifts the focus of the received beam 20 reflected by the nearby object O. In addition, only the portion of the light receiving beam 20 provides reflected light, and the reflected light passes through the mask 42 disposed on the central mirror 44 side. The central mirror 44 reflects the received light beam 20, and the beam 20 enters the central orifice behind the rear mirror 43.

  The light receiver 21 includes an incident diaphragm, a collimator with a filter, a condenser lens, and a detector, and is disposed behind the rear mirror 43. In order to save space, it is preferable to provide a light receiving mirror 45 that changes the direction of the received light beam 90 by 90 °, so that the light receiver 21 can be arranged in the radial direction when viewed from the optical axis A. This bending optical system can almost double the focal length compared to known laser scanners.

  As shown in FIG. 3, the rotary mirror 16 having a two-dimensional structure is a part of a rotor 61 that can be rotated as a three-dimensional structure by a corresponding rotary drive, and the angular position of the drive is determined by an associated encoder. It is measured by. Further, in order to save the space related to the rotary mirror 16 by making the rotor 61 relatively short, and to keep the rotor 61 in a balanced state, the rotor 61 is mounted on the holder 63 and the holder 63. A hybrid structure including the rotary mirror 16 and a plastic material housing 65 is configured, and the rotary mirror 16 is held by the housing.

  This metal holder 63 has a cylindrical basic shape, and has a 45 ° surface and various depressions. The parts that contribute to balancing the rotor 61, such as blades, shoulders, and protrusions, are the same between the recesses. The central hole serves to mount the motor shaft of the associated rotational drive. The rotary mirror 16 is made of glass with a coating and exhibits reflection in the wavelength region involved. The rotary mirror 16 is fixed to the 45 ° surface of the holder 63 with glue, and the holder 63 is provided with a special mounting surface 63b for that purpose.

  The housing 65 made of a plastic material has a hollow cylindrical shape cut at less than 45 °, and at least the holder 63 is sealed therein. The housing 65 may be glued to the rotary mirror 16 or may be fixed in another form. The rotary mirror 16 can be fastened at the periphery by the housing 65, for example, in a form locking form, and rubber sealing or the like may be interposed if necessary. Further, the housing 65 may be directly fixed to the holder 63 by glueing to the holder 63, or when the rotor 61 is mounted, the housing 65 is connected to the holder 63 by the action of the end plate 67, for example, screwed. Also good. By using the glue, the temperature coefficient difference of the material expansion used is offset on the one hand, and on the other hand, the elasticity is not too strong. Eliminated.

  The rotor 61 rotates around the optical axis A. The rotary mirror 16 covers one of the surfaces of the holder 63 (that is, a 45 ° surface). The housing 65 covers the holder 63 from the outside in the radial direction when viewed from the optical axis A. Therefore, since the sharp edge of the holder 63 is covered, it is difficult to cause injury. The holder 63 balances the rotor 61. The holder 63 may be formed of another relatively heavy material that can control the moment of inertia instead of metal. The housing 65 may be formed of another relatively light material that hardly affects the moment of inertia instead of plastic. The rotary mirror 16 may be other reflective (and transmissive) materials instead of the coated glass. The rotary mirror 16, the holder 63, and the housing 65 constituting the hybrid structure are individually formed parts and are fixed to each other.

  The laser scanner whose partial cross section is shown in FIG. 4 has substantially the same configuration as that shown in FIG. 1 except that a dichroic beam splitter 116, an additional lens 118, and an energy detector 119 exist. The coating on this dichroic beam splitter splits electromagnetic energy (ie, light) of a certain wavelength so as to propagate on the path 121 leading to the light receiver 21, while path 120 leading to the additional lens 118 and the energy detector 119. The electromagnetic energy of other wavelengths is branched so as to propagate.

  Examples of electromagnetic energy that can be detected by the energy detector 119 include thermal energy, ultraviolet radiation, millimeter wave radiation, and X-ray radiation. In the energy detector 119 for detecting thermal energy, the electromagnetic radiation will belong to the near infrared or mid infrared region of the electromagnetic spectrum.

  In many cases, a lens 118 is placed between the dichroic beam splitter 116 and the energy detector 119. In some cases, electromagnetic radiation following path 120 may be focused onto a small spot on energy detector 119 by this lens. In this case, the electromagnetic radiation is collected by the energy detector in parallel with the collection of distance information during the scanning procedure. In other words, in this example, energy information is collected point by point by the detector.

  In some cases, the lens 118 may be arranged so that an image of a region of the surrounding environment is formed. In this case, the lens 118 is provided with a plurality of detector elements (ie, pixels). In this type of detector, the collection of information by the scanner is generally performed by moving the scanner according to discrete steps of a step size selected to match the field of view of the lens system.

  Although the dichroic beam splitter is drawn at the position occupied by the mirror in FIG. 1, the dichroic beam splitter can be arranged at various other positions. For example, the dichroic beam splitter 116 may be placed near the dichroic launch mirror 32 so that a wider field of view than would be obtained when the dichroic beam splitter 116 is in the position shown in FIG.

  It is also possible to form the beam splitter differently by covering the right angle mirror so that a certain wavelength is reflected and the second wavelength is propagated. The right-angle prism mirror 122 shown in FIG. 5 is coated on the surface 123 so that the wavelength of the light source 28 is reflected onto the light receiver 21. Electromagnetic energy of other wavelengths propagates through the prism 122 to the energy detector 125 in the form of a beam 124.

  Using a plurality of dichroic beam splitters, eg elements 32 and 116, provides a means to obtain information about various radiations in a single 3D scanner. For example, in addition to knowing the 3D coordinates and colors of objects in the surrounding environment, it can be important to know the temperature of those objects. One convenient example would be a scan inside or outside the house that shows the temperature of the areas of the house. By identifying the heat leak source, repair actions such as adding an insulating material or filling a gap can be recommended.

  Dichroic beam splitters can also be used to acquire multiple wavelengths and provide diagnostic chemistry information, for example by making the energy detector a spectroscopic energy detector. As used herein, a spectroscopic energy detector is a detector characterized by its ability to resolve an electromagnetic signal into its spectral components. In many cases, the light beam is projected onto an object. By receiving and analyzing the reflected light, the existing spectral components can be discriminated. Today, gratings and other elements in spectroscopic energy detectors are miniaturized through the use of microelectromechanical chips. For example, today some companies are working on small devices that can analyze the nutritional components of food. For example, Fraunhofer reports an approach to a spectrometer for the same application that has dimensions of only 9.5 × 5.3 × 0.5 mm. An example of a device with which scanner 10 may be particularly suitable is a device capable of indicating the presence of explosives with spectral radiation. Such an approach is described in Riegl et al. It is described in Patent Document 2 assigned to.

  FIG. 6 shows various elements of the spectroscopic system incorporated in the scanner 10. Light emitted from the electromagnetic energy source is reflected by the beam splitter 130. In some embodiments, the beam splitter 130 is a non-deflecting beam splitter. In another embodiment, the beam splitter 130 is a polarization beam splitter, and its polarization plane is determined with reference to the light source 131 so that the loss is suppressed. The energy detector 119 is a spectroscopic energy detector that can determine the wavelength of incident electromagnetic energy. The wavelength of the reflected electromagnetic energy detected by the energy detector can be used in some cases to determine the material properties of the object to be scanned in the surrounding environment. In some embodiments, the electromagnetic energy source 131 and the beam splitter 130 are moved below the beam splitter 116 in FIG.

  Although the present invention has been described with reference to exemplary embodiments, various modifications may be made without departing from the scope of the present invention, as will be appreciated by those skilled in the art (so-called persons skilled in the art). And the elements can be replaced by alternatives. In addition, various modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Thus, the intent is that the present invention is not limited to the specific embodiments disclosed as the best mode suitable for carrying out the present invention, and any implementation belonging to the technical scope of the appended claims. It is in the point that this invention includes a form. Further, the use of the words “first”, “second”, etc. does not indicate any order or importance, but rather “first”, “second”, etc. to distinguish individual elements from other elements. The words are used. Furthermore, the use of the words “a”, “one”, etc. does not limit the amount, but rather indicates that there is at least one referenced object.

Claims (8)

A laser scanner for optically scanning and measuring the surrounding environment,
A light emitter, a rotary mirror, a light receiving lens, and a light receiver. The light emitter is configured to emit a light beam, and the light receiver is configured to receive the light beam. A portion of the emitted beam reflected by the object and reflected by the object becomes a received beam, and the received beam passes through a light receiving lens having an optical axis reflected by the rotary mirror, a light emitter, a rotary mirror, A light receiving lens and a light receiver;
A color camera that captures color images of the surrounding environment,
A dichroic beam splitter and an energy detector, wherein the dichroic beam splitter is configured to pass electromagnetic energy of the first wavelength to the energy detector and to pass the received beam to the receiver. A dichroic beam splitter and an energy detector having a second wavelength different from the one wavelength;
A control and evaluation unit configured to derive a distance to the object at least partially based on the received beam for a number of measurement points, the distance being received by the color image and the energy detector. A control and evaluation unit configured to link to electromagnetic energy;
A laser scanner comprising:   2. The laser scanner according to claim 1, wherein the color camera is arranged on an optical axis of the light receiving lens.   2. The laser scanner according to claim 1, wherein the energy detector detects energy selected from a set based on infrared energy, ultraviolet energy, X-ray energy, and millimeter wave energy.   2. The laser scanner according to claim 1, wherein the dichroic beam splitter is a plate beam splitter having an entrance surface and an exit surface, and the exit surface is parallel to the entrance surface.   2. The laser scanner according to claim 1, wherein the dichroic beam splitter is a right-angle prism.   2. The laser scanner according to claim 1, further comprising a second lens, wherein the second lens is disposed between the dichroic beam splitter and the energy detector.   7. The laser scanner of claim 6, wherein the second lens is configured to focus electromagnetic energy of a first wavelength on the energy detector.   7. The laser scanner of claim 6, wherein the energy detector has an array of pixels, and the second lens is configured to image electromagnetic energy of a first wavelength onto the array of pixels. Laser scanner.

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