DE102018201481A1 - Apparatus and method for determining the three-dimensional surface geometry of objects - Google Patents

Abstract

The invention relates to a device (10) for determining a three-dimensional surface geometry of an object (8). According to the invention, the device (10) comprises an electrostatic charge generator (1) for electrostatically charging the object (8), measuring means (2) for measuring a difference (z) of an electrostatic potential (φ) at a plurality of measuring points (i) on the Surface (8a, 8b) of the object (8) against a reference potential (φ (0)) and a calculator for calculating the surface geometry of the object (8) from the measured differences (z) of the electrostatic potential (φ) at the plurality of measurement points (i) on the surface (8a, 8b) of the object (8) with respect to the reference potential (φ (0)).

Description

The invention relates to a device and a method for determining the three-dimensional surface geometry of objects according to the preambles of claims 1 and 6.

There are a variety of methods to measure the surface geometry of an object, in particular a spectacle lens. In particular, mechanically or optically scanning methods, deflektometric methods or else interferometric methods are known.

The EP 2 090 861 A1 discloses the measurement of areas by means of a touching button.

Laser scanning (also laser scanning) refers to the line or raster-like sweeping of surfaces or bodies with a laser beam in order to detect their object geometry. In the US 6 122 063 A For example, a device suitable for this purpose is described.

From the WO 2007/018118 A1 , 15 EP 2 261 629 A2 . US 2005/0174566 A1 and JP 2010-008193 A For example, detecting unwanted eccentricities of two opposing optically active surfaces of a lens by scanning the lens with a laser light beam is known.

A deflektometric method is eg from the US 5 106 183 A refer to. There, it is proposed to measure the topography of the surface of an object by detecting reflections of light-emitting diodes arranged on the inside of a spherical surface portion on the surface of the object with a photodetector and subjecting them to evaluation.

The DE 10 2013 208 091 A1 describes a device for deflectometrically measuring the topography and / or the gradient and / or the curvature of an optically active surface of an object. This device has a device for arranging the object in a receiving area, in which the position of at least one point on the surface of the object in a device-fixed coordinate system can be determined. The apparatus includes a plurality of point light sources that provide light that is reflected at the surface to be measured of an object disposed in the receiving area. The device has at least one camera for detecting a brightness distribution which is caused by the light of the point light sources reflected on the surface to be measured on an image sensor. In the device described in this document, the point light sources are arranged on the lateral surface of a polyhedron.

Another method and a corresponding device for measuring the topography and / or the gradient and / or the curvature of a light-reflecting surface of a spectacle lens arranged in a receiving region is shown in FIG DE 10 2014 222 628 A1 described. The device has a light source and has a detection device for detecting a brightness distribution on a detection surface, which is caused there by the light of the light reflecting surface reflected light of the light source on the detection surface. The apparatus further comprises a scanning device for applying the light-reflecting surface with at least one directed light beam from the light source at different locations by relative displacement of the at least one light beam and the spectacle lens to each other.

The EP 2 228 623 A1 and the JP 2001-227908 A describe determining the topography of two opposing surfaces of an object by sequentially determining the distance of these surfaces by means of an interferometric measurement method at a plurality of measurement points.

Although the above-mentioned methods and devices have proven their worth, there is a need for a simple, inexpensive and yet fast apparatus for determining the three-dimensional surface geometry of objects, in particular spectacle lenses.

The object of the invention is therefore to provide a simple, cost-effective and comparatively quickly measuring device for determining the three-dimensional surface geometry of objects, in particular of spectacle lenses. A further object of the invention is to provide a simple, inexpensive and comparatively fast method for determining the three-dimensional surface geometry of objects, in particular of spectacle lenses.

This object is achieved by a device having the features of patent claim 1 and a method having the features of patent claim 6. Advantageous embodiments and modifications of the invention are the subject of the dependent claims.

• - einen elektrostatischen Ladungsgenerator zum elektrostatischen Laden des Objekts,
• - eine Messeinrichtung zum Messen einer Differenz des elektrostatischen Potentials an einer Vielzahl an Messpunkten auf der Oberfläche des Objekts gegenüber einem Referenzpotential und
• - eine Recheneinrichtung zum Berechnen der Oberflächengeometrie aus den gemessenen Differenzen des elektrostatischen Potentials an der Vielzahl an Messpunkten.

The device according to the invention for determining the three-dimensional surface geometry of an object comprises

• - an electrostatic charge generator for electrostatically charging the object,
• a measuring device for measuring a difference of the electrostatic potential at a plurality of measuring points on the surface of the object with respect to a reference potential and
• - A computing device for calculating the surface geometry from the measured differences in the electrostatic potential at the plurality of measurement points.

The above object is achieved in full by the device according to the invention.

• - elektrostatisches Aufladen des Objekts,
• - Messen einer Differenz des elektrostatischen Potentials an einer Vielzahl an Messpunkten auf der Oberfläche des Objekts gegenüber einem Referenzpotential und
• - Berechnen der Oberflächengeometrie aus den gemessenen Differenzen des elektrostatischen Potentials an der Vielzahl an Messpunkten.

The method according to the invention for determining the three-dimensional surface geometry of an object comprises the steps:

• - electrostatic charging of the object,
• Measuring a difference of the electrostatic potential at a plurality of measuring points on the surface of the object with respect to a reference potential and
• Calculating the surface geometry from the measured differences in the electrostatic potential at the plurality of measurement points.

The above object is achieved by the inventive method in full.

Advantageously, the measuring device comprises a scan cassette, wherein the scan cassette has a plurality of probes. The scan cassette generally has a rectilinear shape along which the probes are arranged one behind the other. In this way, the potential differences in one direction (eg along a x Coordinate).

Furthermore, the scan cassette may comprise a plurality of mutually parallel connected to ground plates, wherein between each two adjacent plates, each one of the probes is arranged. Each probe is shielded from the adjacent probe in this way.

In a preferred embodiment, the scan cassette is designed to be translationally displaceable. This not only potential differences in one direction, but also in a direction perpendicular thereto (eg along a y- Coordinate).

There may be a motor for translationally moving the scan cassette. The scan cassette can thus be moved over the object in a predetermined manner.

• 1 ein Ausführungsbeispiel eines erfindungsgemäßen 3D-Scanners im Querschnitt
• 2 den erfindungsgemäßen 3D-Scanner nach der 1 in perspektivischer Darstellung
• 3 eine Potentialverteilung des in der 2 gezeigten Diaphragmas, welches Bestandteil des in den 1 und 2 gezeigten 3D-Scanners ist
• 4 eine Messeinrichtung zur Bestimmung des elektrostatischen Potentials, welches bei dem 3D-Scanner nach den 1 und 2 verwendet wird

The invention will be described below with reference to the drawing. Show it.

• 1 An embodiment of a 3D scanner according to the invention in cross section
• 2 the inventive 3D scanner according to the 1 in perspective view
• 3 a potential distribution of in the 2 Diaphragm shown, which is part of the in the 1 and 2 shown 3D scanner is
• 4 a measuring device for determining the electrostatic potential, which in the 3D scanner after the 1 and 2 is used

The 1 and 2 show an embodiment of a device according to the invention in the form of a 3D scanner 10 in cross-section and in perspective view. The proposed 3D scanner 10 can be used as an inexpensive alternative to, for example, in the DE 10 2013 208 091 A1 or the DE 10 2014 222 628 A1 described devices are used.

While in the DE 10 2013 208 091 A1 or the DE 10 2014 222 628 A1 described devices are not suitable to determine the geometry of the entire object is the 3D scanner 10 according to the invention able to measure individual surfaces. The 3D scanner 10 According to the invention can therefore work more cheaply.

wobei k einen Koeffizienten bezeichnet, der vom verwendeten Einheitensystem abhängt, q die Größe der Ladung angibt und r den Abstand der Ladung q zu dem Punkt i angibt.The principle of the inventive 3D scanner 10 is based on the determination of the difference between the electrostatic potential φ of an electrostatic charge q loaded object to be examined - in the embodiment according to the 1 and 2 an optical lens 8th - and a cathode 6 which is a reference potential φ (0) certainly. The object 8th is by means of an electrostatic charge generator 2 electrostatically charged. The electrostatic potential φ at each point i on the object 8th is then given by the equation $${\mathrm{\phi }}_i=k\frac{q}{r}$$

in which k denotes a coefficient that depends on the unit system used, q indicates the size of the cargo and r the distance of the charge q to the point i indicates.

From the knowledge of the potential difference φ _l -φ (0) between the electrostatic potential φ at each point i on the electrostatically charged object 8th and a basic electrical potential φ (0) the cathode 6 with one and the same charge q can he distance r of the measuring point i on the object 8th to the cathode 6 be determined and with an ad 3 be displayed.

On the basis of this principle that can be in the 1 and 2 shown scheme of a 3D scanner 10 will be realized.

The 3D scanner 10 after the 1 and 2 includes in addition to the electrostatic charge generator 1 and the ad 3 two scan cartridges 4 , which above and below a recording 12 for the object 8th that of a object holder 7 is held, are arranged. Every scan cartridge 4 comprises a plurality of grounded plates arranged parallel to one another 4a , wherein between each two adjacent plates 4a , one probe each 4b is arranged. Every probe 4b represents a thin shielded wire. The distance between two adjacent probes 4b defines the x-resolution of the 3D scanner 10, as in 1 shown.

The length of each cassette 4 is greater than the extent of the object to be measured 8th in this direction x , The the object 8th outstanding left and right sides of each cassette 4 (indicated to the dotted line 14a . 14b . 14c . 14d) are used to measure the electrical ground potential φ (0) ,

For every point i then results from a comparator 2 Measurable measured value z, which is proportional to the potential difference φ _l - φ (0) is, according to the equation: $${\text{z}}_{\text{i}}=\text{m}\left({\mathrm{\phi }}_{\iota }-\mathrm{\phi }\left(0\right)\right)$$

It goes without saying that a determination of the surface geometry, ie the geometry of the surfaces 8a . 8b , an object 8th a measurement in one of the x Direction vertical y Direction required. The cassettes 4 are for that reason along the y Coordinate formed movable or displaceable, as indicated by the double arrows in the 2 is indicated. The movement in this direction y takes place in the embodiment by means of a (not shown) electric motor.

The electric motor according to the embodiment is not a stepping motor. To the y -Coordinate, in which the cassettes 4 currently be able to determine, according to the embodiment, a trigger is necessary. The operating principle of the trigger is as follows: above and below the cathodes 6 are thin diaphragms 5 arranged as in 2 shown.

Each diaphragm 5 is narrower than the cathode width. This does not only allow the potential φ (0) but also the potential φ (d) above the diaphragms 5 to determine. The potential distribution φ (d) above the diaphragms can, for example, as in 3 shown run.

The trigger can be triggered with the maximum or the minimum of the measured potential cp (d). Measurements are made at predetermined points on the y-axis. The complete measurement of the object 8th will consist of a record of the following kind: {x, y, φ _l . φ (0) , φ (c)} {x, y, φ ₂ . φ (0) , φ (c)} {x, y, φ _i . φ (0) . φ (c) }, ..., {x, y, φ _N . φ (0) , φ (c)} from all cassettes 4 , where φ (c) is the potential of the cathode 6 is. The value of the cathode potential φ (c) serves to deviations of the basic potential φ (0) due to mechanical inaccuracies in the production of the 3D scanner 10 excluded. After processing the data with suitable software, the result is a fairly accurate representation of the object in 3D.

The software may include auto-tuning software that uses a calibration object. This serves to different the coefficients k . m to determine the above equations.

A comparator 2 For example, with the aid of cascaded field effect transistors in the 4 be realized type realized.

It should be noted that a small revision of the device (software only) allows to use the measurements as a measure of optical properties of optical lenses.

LIST OF REFERENCE NUMBERS

1

electrostatic charge generator

2

comparator

3

display

4

Scan cassette

4a

plate

4b

probe

5

diaphragm

6

cathode

7

Cathode / object holder

8th

measurement object

8a

surface

8b

surface

10

3D scanner

12

admission

14a

line

14b

line

14c

line

14d

line

φ _l

electrostatic potential

φ (0)

basic electric potential

q

charge

i

Point

k

coefficient

m

coefficient

r

distance

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 2090861 A1 [0003]
• US 6122063 A [0004]
• WO 2007/018118 A1 [0005]
• EP 2261629 A2
• US 2005/0174566 A1 [0005]
• JP 2010008193 A [0005]
• US 5106183 A [0006]
• DE 102013208091 A1 [0007, 0022, 0023]
• DE 102014222628 A1 [0008, 0022, 0023]
• EP 2228623 A1 [0009]
• JP 2001227908A [0009]

Claims (6)

Device (10) for determining a three-dimensional surface geometry of an object (8) with - an electrostatic charge generator (1) for electrostatically charging the object (8), - a measuring device (2) for measuring a difference (z) of an electrostatic potential (φ _i ) at a plurality of measuring points (i) on the surface (8a, 8b) of the object (8) with respect to a reference potential (φ (0)) and - a computing device for calculating the surface geometry of the object (8) from the measured differences (e.g. ) of the electrostatic potential (φ _i ) at the plurality of measuring points (i) on the surface (8a, 8b) of the object (8) with respect to the reference potential (φ (0)). Device (10) according to Claim 1 , characterized in that the measuring device (2) comprises a scan cassette (4), wherein the scan cassette (4) has a plurality of probes (4b). Device (10) according to Claim 2 , characterized in that the scan cassette (4) comprises a plurality of mutually parallel connected to ground plates (4a), wherein between each two adjacent plates (4a), one of the probes (4b) is arranged. Device (10) according to Claim 2 or 3 , characterized in that the scan cassette (4) is designed to be translationally displaceable. Device (10) according to Claim 4 , characterized in that a motor for translational displacement of the scan cassette (4) is present. Method for determining a three-dimensional surface geometry of an object (8) comprising the steps of: - electrostatically charging the object (8), - measuring a difference (z) of an electrostatic potential (φ _i ) at a plurality of measuring points (i) on the surface of the object Object (8) against a reference potential (φ (0)) and - calculating the surface geometry from the measured differences (z) of the electrostatic potential (φ _i ) at the plurality of measurement points (i) on the surface (8a, 8b) of the object (8) against the reference potential (φ (0)).

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