JP2010175550A - Method and device for detecting shape of three-dimensional object - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method (a measuring method of the shape of a three-dimensional object) and a device which can detect the shape of a three-dimensional object in an extremely short measuring time. <P>SOLUTION: The propagation times of the light scattered and/or reflected and/or emitted by an object to be measured are encoded as light intensity modulations and light intensity or light intensity distribution is measured. The shape of the three-dimensional object is determined on the basis of measured values for the light intensity distribution. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a method for detecting a shape of a three-dimensional object (measuring a three-dimensional object shape) and an apparatus therefor.

Object shape detection methods are used in many industrial production fields, particularly in the field of quality control. The geometric data of the object is converted into numerical computer data with the aid of a suitable measuring device. The program then controls the dimensions and other parameters.

Various mechanical and optical methods are known for detecting the shape of an object. First, in the case of a mechanical method, data of a measurement object is usually collected for each point, and the three-dimensional shape of the measurement object is obtained from a series of measurement results for each point. On the other hand, however, it is disadvantageous that mechanical contact with the object to be measured is necessary. On the other hand, in the case of high-accuracy measurement, it is a disadvantage that the measurement time becomes considerably long. In the case of an optical method, since it can be measured without contact, it is a great advantage that it can be carried out without giving mechanical action to the object. For this reason, mechanical deformation of the object due to object measurement is eliminated. In particular, this optical shape detection method is advantageous when the surface of an object can be deformed like an elastic body.

Furthermore, an advantage of the non-contact shape detection method is that a large number of object points (and thus small surface elements) can be detected simultaneously. As a result, the measuring time is considerably shortened compared to the mechanical measuring method. In addition, structures including height can be measured, which is quite difficult with mechanical measurement methods.

Well-known optical shape detection methods are generally based on triangulation or interferometry.

In the triangulation method, a light point is projected on the surface of the object to be measured and observed from a direction away from the illumination direction. The coordinates of the projection point are calculated from the separated light beam projection direction and the observation point direction. This method is fairly accurate and clear. However, since the surface of the object to be measured must be measured point by point, considerable time is required to detect a complete object shape. Also, this method is disadvantageous because it cannot detect moving or changing objects. As a further development of the triangulation method, there are a light section method and a strip projection method.

In the light section method, a line of light is projected on the surface of an object to be measured instead of a single point. This line is observed with a camera from a direction away from the illumination method, and coordinates are determined. The spatial coordinates of the irradiation point can be obtained in the same manner as the above triangulation method. This light section method is faster than point-by-point triangulation, but slower than other methods that can detect a larger area simultaneously.

The strip projection method is a further development of the light section method, and projects a plurality of lines simultaneously onto the surface of an object to be measured. The intensity of these lines changes periodically in the lateral direction, and each line can be identified with an observation camera. This method is faster than the light section method because it can detect over a larger area at the same time. However, lines with the same intensity cannot be identified. Thus, at least some of the distinct measurement characteristics will be lost. For a more accurate measurement method, for example, an interference method such as white light interference analysis is often used.

However, all the above methods are disadvantageous in that the measurement time usually takes seconds, and more accurate measurement takes minutes. The shortest possible measurement time is not limited by the speed of the evaluation algorithm, but rather by the required multiple optical measurement methods.

Accordingly, an object of the present invention is to provide an optical three-dimensional shape detection (measurement) device and an optical three-dimensional shape detection (measurement) method that enable a considerably short measurement time, particularly a measurement time that is clearly shorter than that of the prior art. It is in. Accordingly, it is possible to detect the shape of a three-dimensional object that moves quickly or a three-dimensional object that changes.

This object is realized by the features described in claim 1 (method claim) of the present invention and the features described in claim 18 (device claim) together with the premise of the claims. Developments adapted to this purpose are contained in the dependent claims.

The unique advantage of the present invention is that the solid shape detection method / apparatus of the present invention can realize a measurement time as short as several milliseconds or sub-picoseconds. For this purpose, the transmission time of light scattered and / or reflected and / or emitted by the measurement object is encoded as light intensity modulation, and the light intensity or light intensity distribution is measured. The shape of the three-dimensional object is obtained from the measured value of the light intensity distribution. In this case, it is advantageous that the measurement object is irradiated with an appropriate light source before the light transmission time is encoded as light intensity modulation and the light intensity or light intensity distribution is measured. A pulse laser is suitable as the light source. The encoding of the light transmission time as the light intensity modulation is performed by at least one converter that changes the light absorption / reflection / transmission and / or polarization state according to time. As a result, the light in the optical path that subsequently passes through the converter changes its absorption, reflection, transmission, and / or polarization state, resulting in a different light intensity modulation. From this light intensity distribution, the light transmission time can be estimated. The shape of the three-dimensional object can be estimated from this light transmission time. For example, when the irradiation light is reflected at various reflection angles on the surface of the measurement object, the reflected light distribution is detected through the second light path by the light divider. Appropriate mathematical calculation (division, etc.) is performed on the measured light intensity via the converter and the light intensity distribution on the light path without the converter, and the three-dimensional height of the object or the surface contour of the object (no dimension) Obtained as a distribution. From this distribution, the light transmission time is determined, and thus the three-dimensional shape of the object is determined.

The converter is a non-linear absorber composed of dyes, dye solutions, optical filters and / or semiconductor switches. As a variant of the preferred embodiment, triphenylmethane dye is used as the dye. The semiconductor switch preferably has a GaAs structure. Further, the converter may be an optical gate such as a car cell or a Pockels cell. In order to measure the light intensity, a CCD camera or a CMOS camera may be used as a modification of the preferred embodiment. Furthermore, the device according to the invention can also consist of mirrors and / or partially transparent mirrors, optical imaging systems and / or optical gates.

In the following, the invention will be described in more detail on the basis of an embodiment at least partly shown in the drawings.

FIG. 1 is a schematic view of an optical shape detection apparatus having two measurement channels according to the present invention. The measurement object 10 is irradiated with a femtosecond laser 14. At this time, the light of the laser 14 is divided by the beam divider 16 and guided to the measurement object 10. The other irradiated part passes through the light beam divider 16, passes through the high reflection mirror 20, changes its direction while being appropriately delayed, and is guided to the converter 12 for intensity coding. The converter 12 is a non-linear, high-speed switching optical filter. Such filters are available, for example, from the RG series (Schott, Germany). The light scattered by the measurement object is guided to a nonlinear absorber (converter 12) whose volume is whitened by excitation with the aid of the lens system 18. After passing through the converter 12, the scattered light of the measurement object 10 is imaged by a lens system 22 provided on the surface of the CCD camera 26. As a result, the light scattered by the measurement object 10 is observed by the CCD camera 26. The scattered light is light intensity modulated by a nonlinear characteristic curve of the nonlinear absorber (converter 12) as a function of the light transmission time. When using the converter 12 (RG filter), the absorption recovery time results in the intensity being coded on a logarithmic scale as a function of delay time (and thus a function of the measured object shape). The light intensity is encoded by the non-linear absorber (converter 12), and as a result of the light intensity distribution, an image is generated in the CCD camera 26. Since the first measurement object reflects the irradiation light in various directions (at various reflection angles) on the surface of the three-dimensional object, the reflected light is behind the light beam divider 32, the high reflection mirror 30, and the lens system 24. Recorded in the second CCD camera 28 or the reflected light from the second illumination is recorded in the camera 26 without the converter (eg, removing the converter 12 or redirecting the light appropriately). The height profile of the measurement object 10 is obtained by dividing the light intensity behind the converter 12 measured by the CCD camera 26 by the second light intensity distribution after removal of the converter 12 measured by the CCD camera 26. Alternatively, the second light intensity distribution (not through the light path through the converter 12) can be measured by the second CCD camera 28. Equalization of the height profile is done after logarithmic correction of the intensity coding as a function of the whitening duration of the nonlinear absorber (converter 12).

FIG. 2 is a photographic image of the first measurement object. This is a Teflon stopper used for cuvette containers. The length of this stopper is about 10 mm.

FIG. 3 is a diagram showing a height profile of the first measurement object calculated after measurement by the method of the present invention. The scale of the height contour is different from the actual value. That is, the actual total length in the X direction is about 10 mm, and the Y direction is about 7.5 mm. When only a single irradiation from the viewpoint shown in FIG. 2 is used, only the diameter of the stopper is measured by the method of the present invention. The background of the stopper is caused by the noise of the CCD camera.

FIG. 4 is a measurement light intensity distribution diagram of the second measurement object encoded with a gray image.

The characteristic feature of the method of the present invention is that it can measure an object moving at high speed with a time resolution in the sub-nanosecond range, a repetition rate in the kilohertz range, and a relative accuracy of 1/1000 or more.

In the case of measurement, a plurality of converters used are electronically activated, and in the case of higher accuracy measurement, it is optically activated. The requirements for accuracy are not required to be very sophisticated. This is because the measurement is at the edge of the transmission change effect (or reflection / polarization change effect), so that a predetermined time interval can always be obtained for the measurement. In this case, not only the falling edge of the transmission change effect (or reflection / polarization change effect) but also the rising edge can be used in principle. In the embodiment of FIGS. 2-7, a falling edge is used.

In the simplest case, a non-linear absorber is used with a known absorption recovery time. This absorber is whitened by corresponding excitation light, preferably a pulsed laser. The excitation light is synchronized with the measurement light. This causes a time-dependent transmission attenuation of the light scattered and / or reflected and / or emitted from the measurement object.

Such a non-linear absorber is realized by means of a suitable dye (for example triphenylmethane dye) or a suitable semiconductor switch, for example on the basis of a fast-switching optical filter available from the RG series (Schott AG, Germany). The treatment method according to the invention is economical because a series of components can be used. In evaluating the light intensity distribution by the CCD camera, a logarithmic characteristic curve of the CMOS camera is presented. This CMOS camera makes it possible to use the characteristic curve of the nonlinear absorber. The accuracy of the measurement is limited by the non-uniform illumination or converter transmission profile, but can be significantly enhanced by reference channels and reference measurements. Furthermore, the use of various converters simultaneously or sequentially on different measurement channels will increase the measurement accuracy. With a suitable device (such as a resonator), each of the low speed converters can be activated and then the higher speed converters can be activated in a complex manner. Thereby, highly accurate measurement is possible over a wider measurement range.

The measurement results obtained by the measurement methods from different viewpoints are integrated, and the mathematical description of the three-dimensionally measured object is converted into, for example, a CAD format. According to the present invention, the gate can be arranged in the measuring device so that the solid shape can be detected only in a predetermined depth range. By this method, for example, shape detection in a scattered measurement object can be performed. This is particularly advantageous for biological and / or medical applications.

The three-dimensional shape detection according to the present invention can also be performed for two-dimensional shape detection. In the case of two-dimensional shape detection, the camera can be operated, for example, in a light intensity measurement combined mode, or it can be replaced by a linear line or pin diode. For single point evaluations, removal measurements can be performed.

FIG. 5 is a photographic image of the second measurement object. This is the inner center of the CD case that holds the CD and the tube clip behind it.

FIG. 6 is a diagram showing the height profile of the second measurement object calculated after measurement by the method of the present invention. In this figure, the difference in the various height levels of the second object can be clearly seen. The fastener was measured using a single measurement irradiation corresponding to FIG. 6, but not from the depth because it was irradiated from the front only. Therefore, the fastener of the CD case of FIG. 6 is shown extending in the Z direction (depth). Yet another effect is that this area is not measurable due to the shadow of the clip fastener tip. Therefore, the portion of the clip behind the CD case appears as a three-dimensional outline. However, this part is not consistent with the actual situation. This effect can be overcome by appropriate irradiation. Nevertheless, it can be said that the processing of the present invention can also be shown in this example. Similar to FIGS. 3, 4, and 7, the final scaling process is not performed in FIG. 6. Nevertheless, the three-dimensional structure of the second measurement object can be clearly seen.

FIG. 7 is a measurement light intensity distribution diagram of the second measurement object encoded with a gray image.
The quality of the measurement process is enhanced by using high quality components. With possible measurement methods, even objects in centimeters can be calculated with an accuracy of less than 10 μm per depth measurement.

A series of measurement speeds is determined by the data evaluation speed. Real-time measurement of a three-dimensional object that changes at high speed can be realized by a high-speed computer.

The method of the present invention described above can be applied to many fields. For example, it can be applied to the measurement of high-speed moving parts such as turbines and strict quality control in the field of microelectronics such as chips, DVDs and CDs. Furthermore, it is possible to measure the transmission material such as quality control of the optical glass and measurement of the outflow amount of liquid and gas. Also, the method according to the present invention can measure a series of light intensities distributed across the object cross section. Therefore, for example, quality control of the laser emission cross-sectional contour can be performed.

The present invention is not limited to the examples of the present specification. Combinations and modifications of the methods and elements described above may vary the embodiments without exceeding the scope of the invention.

It is the schematic of the optical shape detection apparatus by this invention. It is a photograph image figure of the 1st measurement object. It is a figure which shows the height profile of the 1st measurement object measured and calculated with the processing method of this invention. It is a measurement light intensity distribution map of the 1st measurement object coded with the gray image. It is a photograph image figure of the 2nd measurement object. It is a figure which shows the height profile of the 2nd measurement object measured and calculated with the processing method of this invention. It is a measurement light intensity distribution map of the 2nd measurement object coded with the gray image.

DESCRIPTION OF SYMBOLS 10 Measurement object 12 Converter 14 Pulse laser 16 Light beam divider 18 Lens system 20 High reflection mirror 22 Lens system 24 Lens system 26 CCD camera 28 CCD camera 30 High reflection mirror 32 Light beam divider

Claims (17)

a) encoding the transmission time of light scattered and / or reflected and / or emitted by the measurement object as light intensity modulation; b) measuring light intensity or light intensity distribution; c) measurement data. And determining the shape of the three-dimensional object,
The measurement object is illuminated by an appropriate light source before encoding the light transmission time as light intensity modulation and measuring the light intensity or light intensity distribution,
The encoding of the light transmission time as the light intensity modulation is performed by at least one converter that changes the light absorption / reflection / transmission and / or polarization state according to time, and the converter includes a dye, a dye solution, and an optical filter. And / or by a non-linear absorber composed of semiconductor switches,
A three-dimensional object shape detection method, wherein light from the light source is divided and applied to both the measurement object and the converter.   The three-dimensional object shape detection method according to claim 1, wherein the dye is a triphenylmethane dye.   The three-dimensional object shape detection method according to claim 1, wherein the semiconductor switch has a GaAs structure.   The three-dimensional object shape detection method according to claim 1, wherein the light source is a pulse laser light source.   The three-dimensional object shape detection method according to claim 1, wherein the converter is irradiated with a pulse laser light source, and its transmission or absorption state changes.   6. The three-dimensional object shape detection method according to claim 1, wherein the light intensity measurement is performed by a CCD camera, a CMOS camera, a CCD line camera, or a film of a CMOS line camera.   Furthermore, one or more measurements of light scattered and / or reflected and / or emitted by the measurement object are made without going through an optical path through the converter. The solid-object shape detection method as described in any one of.   The measurement data is evaluated based on a plurality of pieces of coded information of light transmission time as light intensity modulation, a shift (offset) of light transmission time as light intensity modulation, and / or light intensity measurement values. 8. The three-dimensional object shape detection method according to claim 1, wherein the three-dimensional object shape detection method is performed based on a plurality of pieces of coded information of light transmission time as modulation and light intensity measurement values obtained by a plurality of measurement channels.   The three-dimensional object shape according to claim 1, wherein an action of light scattered and / or reflected and / or emitted from the measurement object is limited by one or more optical gates of the measurement apparatus. Detection method.   The three-dimensional object shape detection method according to claim 1, wherein the evaluation and / or measurement is performed in one or two dimensions.   The evaluation of the measurement data is performed based on a plurality of coded information of light transmission time as light intensity modulation and light intensity measurement values, and a plurality of converters are used simultaneously or sequentially in different channels. The three-dimensional object shape detection method according to claim 1. In a three-dimensional object shape detection apparatus provided with one or more light intensity measurement units of light emitted from a measurement object and one or more measurement data evaluation units, the light absorption / reflection / transmission and / or polarization state One or more converters for encoding the light transmission time as light intensity modulation by at least one change of
The converter is a non-linear absorber composed of a dye, a dye solution, an optical filter and / or a semiconductor switch,
A three-dimensional object shape detection apparatus comprising: a light source; and a light beam divider that divides the light so that light from the light source is irradiated to both the measurement object and the converter. The dye is a triphenylmethane dye, and the semiconductor switch is GaAs
The three-dimensional object shape detection apparatus according to claim 12, having a structure.   The three-dimensional object shape detection apparatus according to claim 12, wherein the light source is a pulse laser.   15. The three-dimensional object shape detection apparatus according to claim 12, wherein the light intensity measurement unit is a CCD camera, a CMOS camera, a CCD line camera, or a CMOS line camera.   The three-dimensional object shape detection apparatus according to claim 12, wherein a plurality of measurement channels are provided.   The three-dimensional object shape detection device according to claim 12, further comprising a mirror, a partially transparent mirror, an optical imaging system, and / or an optical gate.

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