Abstract
A method and apparatus for the generation of 3Dimensional data for an object consisting of one or more light projection systems, a means of generating a light pattern or structure, one or more sensors for observing the reflected light, one or more sensors for registering position, one or more calibration methods for rationalizing the data, and one or more algorithms for automatically analyzing the data to reproduce the 3D structure.
Claims
1) A method for reconstructing and/or measuring the surface of an object or objects using a combination of structured light and a periodic modulation; the said method comprising rotating the structured light around the center of the structured light reference frame, measuring the sensor signal from a reference surface and storing the signal of the reference surface for future use, measuring the signal in a sensor in each predefined areas of the object(s) and storing for future use, analyzing said signals using known methods to extract the phase difference between the reference and the object(s), and using said signal analysis in computing the relative surface height of the object.
2) A method for reconstructing and/or measuring the surface of an object or objects using a combination of structured light and a periodic modulation; the said method comprising rotating the structured light around the center of the structured light reference frame, creating a computer-generated, or synthetic, reference signal and storing the reference signal for future use, measuring a signal in the sensor in each predefined areas of the object(s) and storing for future use, analyzing the signals using known methods to extract the phase difference between the reference and the object(s), and using said signals in computing the relative surface height of the object.
3) A method for reconstructing and/or measuring the surface of an object or objects using a combination of structured light and a periodic modulation; the said method comprising rotating the structured light around the center of the structured light reference frame, measuring a signal from a reference surface and measuring a signal in the sensor in each predefined areas of the object(s) at the same, or nearly the same, time, comparing the signals utilizing an electronic comparator, analyzing the signals using known methods to extract the phase difference between the reference and the object(s), and computing the relative surface height of the object.
4) A method for reconstructing and/or measuring the surface of an object or objects using a combination of structured light and a periodic modulation; the said method comprising rotating the structured light around the center of the structured light reference frame, measuring a signal from a reference surface and measuring a signal in the sensor in each predefined areas of the object(s) at the same, or nearly the same, time, comparing to the signals utilizing an electronic comparator, analyzing the signals using known methods to extract the phase difference between the reference and the object(s) and computing the relative surface height of the object.
5) The method of claim 1, 2, 3, or 4 where the object is translated, or the structured light is translated, or multiple light sources are used to eliminate any null conditions.
6) The method of claim 1, 2, 3, or 4 where the object is translated, or the structured light is translated, or multiple light sources are used to eliminate any null conditions, and the method is repeated for different width and spatial frequency in the light source to extend dynamic range or eliminate phase errors.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 Basic layout consisting of a light source with the ability to project and rotate structured light consisting of one or more lines of various widths and pitch, a sensor capable of measuring the structured light, a second sensor which monitors the angular position of the structured light, and a computer system that is used to synchronize, gather and analyze data.
[0010] FIG. 2 Same system as above with light structure rotated to an arbitrary angle. The light structure can be rotated to arbitrary angles or be continuously rotated. The sensor can capture one or more images, or continually capture data.
[0011] FIG. 3 Simulation of signals used for phase measurements in which the method for generating relative phase uses reference images 8, 9 and sample images 10,11 to generate temporal comparisons at single pixels between the reference and sample images of two structured light lines 12, 13. Two specific cases are shown for the pixel comparison: in one case the structured light line is rotated about the center of the field of view 8,10, and in the other case, the structured light line is rotated about a displaced reference 9,11.
[0012] FIG. 4 Shows the relationship between the spatial period of the structured light (T), the measured phase delta (), and the height change (z).
[0013] FIG. 5 An alternative layout consisting of a light source with the ability to project and rotate structured light consisting of arrays of lines of various widths and pitch, sensors capable of measuring the structured light from the sample and reference simultaneously, one or more sensors to measure the angular position of the structured light, and a computer system that will be used to synchronize, gather and analyze data.
[0014] FIG. 6 One example of a two-step process used as part of one embodiment of the invention for generation and analysis of 3Dimensional data.
[0015] FIG. 7 An alternative single-step process used as part of one embodiment of the invention for generation and analysis of 3Dimensional data.
DETAILED DESCRIPTION OF INVENTION
[0016] Reference is made herein to the attached drawings. Like reference numerals are used throughout the drawings to explain elements of the 3Dimensional measuring instrument. For the purpose of presenting a brief and clear description of the invention, the preferred embodiment will be discussed as used for the measurement of signal phase with subsequent analysis of this phase used to measure changes in distance. The figures are intended for representative purposes only and should not be considered to be limiting in any aspect.
[0017] Referring to FIG. 1, a light source capable of generating rotating, structured light 1 is projected onto the sample area 2. The structured light 6, as projected onto the sample area 2, will be measured by a sensor 3. A separate sensor 4 will be used to measure the angular position of the structured light. The data from sensors 3 and 4 are collected and passed to a computing system 5. The computing system 5 will have the ability to synchronize the angular position as measured by sensor 4 with the data acquired by sensor 3. The computing system 5 will also store and analyze data.
[0018] For clarity, FIG. 2 has the same layout as FIG. 1. However, in FIG. 2 the projected structured light 6 has been shown to be rotated to an arbitrary angle with its subsequent data representation 7 shown on the computer monitor. In application, the structured light can be rotated to arbitrary, discrete, angles or rotated continuously. In all cases, the data from the angle monitoring sensor 4 and the image monitoring sensor 3 will be synchronized as subsequently described.
[0019] Referring to FIG. 3, simulation of signals of 2 line segments (y=mx+b, in arbitrary units) with (10,11) and without (8,9) a sample present, or sample and reference signals respectively. For simplicity, m is set to zero in both cases and line segments at b=0 and b=10 are compared (8,9 and 10,11 respectively). For simulation purposes, the line segments are rotated at a constant angular velocity () of 0.1 rotations per second and images have been displayed at discrete angles from 5 degrees to 180 degrees in increments of 5 degrees. To demonstrate the signal response when a sample is present, a box 14 of arbitrary height has been inserted at the same locations shown in 10 and 11. A phase lead is shown for example purposes, indicating an outward forming box. Sensor signals are compared at the same location, with equivalent sensor size. In one implementation of the method, the phase delta () can be calculated from a time analysis comparison of the reference signal to the sample signal shown in 12 and 13 simply by multiplying time offset between the signals (t) by .
[0020] Referring to FIG. 4, one implementation of the method is described for using the spatial period (T) to relate the measured phase delta () to the height change (z). The field of view 15 of known width W is composed of N periods of length T. Relating the known width of the structured light W to the number of periods (N*T) 16, the phase delta can be converted to distance using the approximation z.sup.*(2W/N) 17. Alternative calculation can be done in the sensor space using the resolution of the sensor, effective magnifications, and geometrical configuration of the optical system.
[0021] An alternative layout of the instrument is references in FIG. 5. In this one implementation, the reference 18 and the object 19 are measured simultaneously, or near simultaneously. For this implementation, an image splitting mirror 20 is used to direct the structured light generated form the light source 21 onto the reference 18 and object 19. Sensors 22 and 23 are used to measure the reflected structured light from the reference 18 and object 19 simultaneously, or near simultaneously. Sensors 24 is used to measure and track the angular position of the structured light. Computer and synchronizing hardware and software 25 are used to synchronize the data collection from sensors 22 and 23 with the position of the structured light as measured by sensor 24. Comparisons between data measured on the reference and sample subjects are done through computer algorithms and/or hardware comparators to calculate the relative phase.
[0022] Referring to FIG. 6, an example two (2) step process for generation and analysis of data is described. In the Step 1, the structured light (Light Frame of Reference, LFOR) is generated at certain angles, rotated, and synchronized with the sensor; data (Image Capture Data Array Cube, ICDAC) is collected for both the reference and the sample for each LFOR and stored for processing in Step 2. This process can be repeated for multiple LFOR or terminated after a single comparison. In Step 2, ICDAC Traces (at each X,Y location in the sensor) are extracted from the stored IDAC for both reference and sample and analyzed to extract the relative phase; the relative phase is stored for each ICDAC trace to generate a phase map for each LFOR. Multiple Phase Maps are compared to identify any phase wrapping errors and the errors are corrected. Phase is converted to 3D height map information based upon the LFOR reference calibration. The 2 step process can be done sequentially or in parallel.
[0023] FIG. 7 shows a possible alternative single-step process for generation and analysis of data using the layout shown in FIG. 5. In this alternative approach, reference and sample data are collected and analyzed simultaneously. IDAC Trace analysis for relative phase may be done through software or through hardware.
