Title of Invention	"SYSTEM AND METHOD FOR REAL TIME MONITORING OF VIBRATIONS AND LARGE DEFORMATION IN DIFFUSED MATERIALS USING SEQUENTIAL SUBTRACTION AND IMAGE ENHANCEMENT"
Abstract	A Digital Speckle Pattern Interferometric (DSPI) device for monitoring the vibrations and mode shape of vibrating surfaces is disclosed. The device comprises a beam divider for splitting a laser beam into two mutually coherent object wave and reference wave. The object wave illuminates diffused surface of object. A digital filter spatially filters and collimates the reference wave. A means for combining the object wave with the reference wave forms the speckle interferogram which is converted into a video signal. Another means monitors the vibration and its mode shapes in real time when intensity of light falling on the object is either low or high. Lastly, a means creates an image for interferogram by subtracting current image from reference image and continues the process by subtracting the resultant image from the previous image. The recorded interferogram is displayed at the rate of 30 images per second after histogram equalization.

Title of Invention

"SYSTEM AND METHOD FOR REAL TIME MONITORING OF VIBRATIONS AND LARGE DEFORMATION IN DIFFUSED MATERIALS USING SEQUENTIAL SUBTRACTION AND IMAGE ENHANCEMENT"

Abstract

A Digital Speckle Pattern Interferometric (DSPI) device for monitoring the vibrations and mode shape of vibrating surfaces is disclosed. The device comprises a beam divider for splitting a laser beam into two mutually coherent object wave and reference wave. The object wave illuminates diffused surface of object. A digital filter spatially filters and collimates the reference wave. A means for combining the object wave with the reference wave forms the speckle interferogram which is converted into a video signal. Another means monitors the vibration and its mode shapes in real time when intensity of light falling on the object is either low or high. Lastly, a means creates an image for interferogram by subtracting current image from reference image and continues the process by subtracting the resultant image from the previous image. The recorded interferogram is displayed at the rate of 30 images per second after histogram equalization.

Full Text	FIELD OF THE INVENTION The present invention relates to a system and method for real time monitoring of vibration and large deformation in diffused materials using sequential subtraction and image enhancement. The invention has a wide area of application including power generating industry, automobile industry, aerospace industry and R&D laboratories. BACKGROUND OF THE INVENTION Holography has permitted the extension of classical interferometry, used to measure path differences of optically polished and specularly reflecting rough surfaces, to three dimensional diffuse objects with non-planar surfaces. For an on-axis reference beam and image-plane recording, the usual high-resolution photographic plate can be replaced by a CCD camera. A digital equivalent of wet processing for developing, fixing and displaying the hologram can be accomplished at video rate. The result is a Digital Speckle Pattern Interferometric (DSPI) system, which gives a live TV display of static and dynamic deformations of the object with the same sensitivity as that of conventional holography. DSPI has been used for many applications. In particular, time-average DSPI is a powerful tool for non-destructive evaluation of dynamic deformations. It is already known that to remove the speckle noise in DSPI fringes a filtering scheme using Symlet wavelet is more suitable and experiments have been conducted to remove the speckle noise from fringes recorded for surface of computer hard disk. PRIOR ART U.S. Patent No. 6,323,943 provides a vibration measurement method and apparatus utilising a self-mixing type laser Doppler vibrator meter. The vibration measurement method includes steps of: oscillating a laser beam of a predetermined wavelength and applying the laser beam to an object to be measured; mixing the reflected laser beam from the object and the oscillated laser beam for outputting a beat wave; calculating ratio of a beat wave amplitude for the turning point of the vibrating object, with respect to a predetermined reference amplitude; and calculating a displacement amount for the turning point of the vibrating object, according to calculated ratio. This enables detection of the vibration of the object to be measured. It is also known that digital Speckle Pattern Interferometric (DSPI) system can measure/monitor static and dynamic deformations in sub-micrometer range (of the order of A,/2, wherein X is the wavelength of the laser light in use). The DSPI is digital equivalent of conventional holographic interferometric (HI) system where object and reference beams interfere at almost zero degree. It is free from wet processing problems of conventional HI. STJMMARY OF THE PRESENT INVENTION In the present system a beam of laser is split into two mutually coherent beams by a beam divider. One of the beams illuminates the diffused reflecting surface of the object. The other beam is spatially filtered and collimated before interference takes place close to zero degree at the CCD faceplate. The object wave is combined with the reference wave to form a speckle interferogram that is converted into a video signal by the photoelectric action of video camera. The video analog output from the camera is fed into the PC based image processing system. In the present invention the time average interferograms are grabbed at frame acquisition rate and subtracted from the just previous time-averaged interferogram. The resultant interferograms are displaced continuously on computer screen at the frame rate 30 images per second. Computer program for interferogram acquisition, processing (evaluation of the interferograms) and displaying the results are written in the Labview environment. The system is optimised to get high contrast fringes. The subject system is based on the well known principle of interferometry. In this system, optically rough surface of the object is illuminated by laser light. The object wave is combined with the in-line reference wave to form the speckle interferogram that is converted into a video signal by the photo-electric action of the video camera. Fringes are obtained by subtracting two interferograms of the vibrating object. The design of the DSPI system developed by us is such that even if there is change in position (in-plane, out-of-plane, tilt, or combination of the all) of the object is in centimeters the monitoring of vibration of the object is possible. In all the inventions present in the prior art, the reference interferogram is predetermined and the subsequent interferograms are subtracted continuously from the reference interferogram. However in the present invention the time-average interferogram of the vibrating surface of the subject instrument over the frame acquisition period (1/30 second) is grabbed and subtracted from the just preceding time-average interferogram in sequential subtraction manner. Secondly in the inventions known in the prior art, the wavelets used were either Daubechies or Fourier transform filtering which had severe limitations accompanying the resuhs. Kauffmann and Galizzi have used Daubechies(db) wavelet filtering to reduce speckle noise in computer generated speckle correlation fringes. But the db wavelet is not much effective at the edges of the fringes. The Symlet wavelet filtering is more effective at the edges of the fringes in comparison to the Daubechies wavelet. However, despite having many advantages, the DSPI fringes have inherent speckle noise and poor fringe contrast. The present invention applies a new filtering scheme based on wavelet transform to improve the signal-to-noise ratio (SNR) in DSPI interferograms. The invention has capability to take care of small rigid body displacement/rotations of the object, direction of illumination and low frequency fluctuations in the lighting conditions. After recording of interferograms of the object e.g. loudspeaker diaphragm, computer hard disk etc., depending on the amount of speckle noise and texture of the object in the speckle interferograms, the interferograms are processed by a combination of median and Symlet wavelet filtering or average and Symlet wavelet to achieve better accuracy in measurement. In case the speckle noise is moderate, the combination of average and Symlet filtering is used and in case the speckle noise is more then the combinatioft of median and Symlet filtering is used. OB.IECTS OF THE PRESENT INVENTION The present invention resides in two embodiments wherein the first embodiment implements: a. monitoring of vibration and its mode shapes almost in real time. Monitoring of vibration can be done even if the intensity of light falling on the object is too poor or too high. The threshold can be set accordingly. b. if the object is in continuous motion, measurement of vibration with almost zero error is possible. Maximum speed of the object is equivalent to 140\|im/minute continuous motion of the faceplate of the CCD camera. c. fringes with relatively high signal-to-noise ratio (SNR) and improved contrast is obtained without separate processing. d. the time interval for display and recording the fringes can be adjusted as per requirement in specific applications (if a data after certain time is important and other data in between are not of so much importance, only the important data can be displayed and recorded by setting the time interval for display and recording). e. while monitoring the vibration, if there is fluctuation in the ambient light, it has almost no effect as the frame rate of acquisition of specklegram as frame refreshing rate is quite high. Accordingly, the present invention relates to a Digital Speckle Pattern Interferometric (DSPI) device for monitoring the vibration and its mode shape in real time comprising of:- (a) a beam divider for splitting a beam emitted by the laser towards the object into two mutually coherent beams wherein one of the beams illuminates the diffused surface of the object, herein called the object wave, (b) a spatial filter provided in the path of the second beam to spatially filter and collimate the second beam, herein called the reference wave, (c) means for combining the object wave with the in-line reference wave to form the speckle interferogram, (d) means for converting the said speckle interferogram into a video signal, (e) means for monitoring the vibration and its mode shapes in real time in the event intensity of light falling on the object is either low or high. (f) means for creating an image for interferogram by subtracting the current image from the reference image and continuing the process by subtracting the resultant image from the previous image and displaying the recorded speckle interferogram on the computer screen in real time at the rate of 30 images per second after histogram equalization. In the second embodiment automatic filtering of speckle interferogram is implemented and it can measure very large deformations which is not possible by any other commercially available systems. DETATLED DESCRIPTTON OF THE ACCOMPANY DRAWINGS Fringe patterns of vibrating loudspeaker (5 mW max., 3 mW min., 47Q, Hi-Fi speaker) diaphragm were recorded. A typical fringe pattern recording of loudspeaker diaphragm (fixed at the outer edge) vibrating at input signal frequency 4.5 kHz and amplitude 700 mVPP (excited by a HP 33120A function generator) is shown in Fig. 1(a). Result of filtering when Symlet wavelet (sym 5) is applied on the average 5 filtered image is shown in Fig. 1(b). Fig. 1(c) is the image when Symlet wavelet (sym 5) is applied on an image filtered by 3 x 3 median filter. The fringe patterns of vibrating variable speed motor (60 W, maximum speed 6500 rpm) bracket were recorded. A typical fringe pattern recording of the vibrating motor bracket is shown in Fig. 2(a). Result of filtering when Symlet wavelet (sym 5) is applied on the I average 5 filtered image is shown in Fig. 2 (b). Fig. 2 (c) is the image when Symlet wavelet (sym 5) is applied on an image filtered by 7 x 7 median filter. In Fig. 3 (a), the recorded fringe patterns of vibrating rectangular plates (dimension 150 mm X 50 mm x 3 mm) of effective length 106 mm tightened by bolts at one end when exited by a sinusoidal load of 2.4 x 10-3N at frequency 930 Hz (load is applied at a distance 100 mm from the fixed end) is shown. Filtering result when average 3 filtering followed by Symlet wavelet (sym 5) is implemented on the fringe pattern shown in Fig. 3 (a) is shown in Fig. 3 (b). Filtering result when median 3x3 filtering followed by Symlet wavelet (sym 5) is implemented on the fringe pattern shown in 3 (a) is shown in Fig. 3 (c). From the recorded images of the speckle interferogram it can be observed that the SNR in the speckle interferogram shown in Figure 1 (a) and Figure 2(a) are less than the SNR of the speckle interferogram shown in Fig. 3 (a). Filtering results show that for vibrating objects when Symlet wavelet was applied on the average or median filtered image of the speckle interferogram, the contrast and the SNR improves. Enhancement in contrast and SNR is more when Symlet wavelet was applied on the median filtered image of speckle interferogram for the case in which SNR in the recorded speckle interferogram was poor. If the SNR in the recorded interferogram is moderate, enhancement in contrast and SNR is more by applying Symlet wavelet filtering on the average filtered image of the speckle interferogram. For quantitative evaluation purpose, data obtained by both the programs is processed by average/median and Symlet wavelet filtering. From the filtered data the fringe profile can be drawn which improves the accuracy of measurement. Conventionally used systems can measure deformations only upto 10-15 µm while the subject system can work even up 1000 µm. The subject system is a very precise and cost effective vibration monitoring system, which can be used to measure/detect vibration/deformation in the reflecting or diffused surfaces in any precision engineering applications e.g. computer disks. It can be used as a component of automatic inspection and quality control system. WE CLAIM: 1. A Digital Speckle Pattern Interferometric (DSPI) device for monitoring the vibrations and mode shape of vibrating surfaces in real time comprising of: (a) a beam divider for splitting a beam emitted by a laser into two mutually coherent beams wherein one of the beams illuminates the diffused surface of the object, herein called the object wave, (b) a digital filter provided in the path of the second beam to spatially filter and collimate the second beam, herein called reference wave, (c) means for combining the object wave with the in-line reference wave to form the speckle interferogram, (d) means for converting the said speckle interferogram into a video signal, (e) means for monitoring the vibration and its mode shapes in real time in the event intensity of light falling on the object is either low or high, (f) means for creating an image for interferogram by subtracting the current image from the reference image and continuing the process by subtracting the resultant image from the previous image and displaying the recorded speckle interferogram on the computer screen in real time at the rate of 30 images per second after histogram equalization. 2. A Digital Speckle Pattern Interferometric (DSPI) device as claimed in claim 1, wherein the the recorded speckle interferograms are processed by a combination of average filtering and Symlet wavelet filtering in case the speckle noise in the recorded speckle interferograms is moderate. 3. A Digital Speckle Pattern Interferometric (DSPI) device as claimed in claim 1, wherein the the recorded speckle interferograms are processed by a combination of median filtering and Symlet wavelet filtering in case the speckle noise in the recorded speckle interferograms is high. 4. A Digital Speckle Pattern Interferometric (DSPI) device as claimed in claim 1, wherein the said isolated pixels in the matrix are removed by element-wise filtering before processing with symlet wave filtering. 5. A Digital Speckle Pattern Interferometric (DSPI) device as claimed in claim 1, wherein the means for converting the speckle interferogram into the video signal is a CCD camera. 6. A Digital Speckle Pattern Interferometric (DSPI) device as claimed in claim 1, wherein the images created, in the means for creating image by continuous subtraction of images, areis processed in a Personal Computer (PC) based image processing system 7. A Digital Speckle Pattern Interferometric (DSPI) device, substantially as hereinbefore described with reference to the accompanying drawings.

Full Text

FIELD OF THE INVENTION
The present invention relates to a system and method for real time monitoring of vibration and large deformation in diffused materials using sequential subtraction and image enhancement. The invention has a wide area of application including power generating industry, automobile industry, aerospace industry and R&D laboratories.
BACKGROUND OF THE INVENTION
Holography has permitted the extension of classical interferometry, used to measure path differences of optically polished and specularly reflecting rough surfaces, to three dimensional diffuse objects with non-planar surfaces. For an on-axis reference beam and image-plane recording, the usual high-resolution photographic plate can be replaced by a CCD camera. A digital equivalent of wet processing for developing, fixing and displaying the hologram can be accomplished at video rate. The result is a Digital Speckle Pattern Interferometric (DSPI) system, which gives a live TV display of static and dynamic deformations of the object with the same sensitivity as that of conventional holography.
DSPI has been used for many applications. In particular, time-average DSPI is a powerful tool for non-destructive evaluation of dynamic deformations.
It is already known that to remove the speckle noise in DSPI fringes a filtering scheme using Symlet wavelet is more suitable and experiments have been conducted to remove the speckle noise from fringes recorded for surface of computer hard disk.
PRIOR ART
U.S. Patent No. 6,323,943 provides a vibration measurement method and apparatus utilising a self-mixing type laser Doppler vibrator meter. The vibration measurement method includes steps of: oscillating a laser beam of a predetermined wavelength and applying the laser beam to an object to be measured; mixing the reflected laser beam from the object and the oscillated laser beam for outputting a beat wave; calculating ratio of a beat wave amplitude for the turning point of the vibrating object, with respect to a predetermined reference amplitude; and calculating a displacement amount for the turning point of the vibrating
object, according to calculated ratio. This enables detection of the vibration of the object to be measured.
It is also known that digital Speckle Pattern Interferometric (DSPI) system can measure/monitor static and dynamic deformations in sub-micrometer range (of the order of A,/2, wherein X is the wavelength of the laser light in use). The DSPI is digital equivalent of conventional holographic interferometric (HI) system where object and reference beams interfere at almost zero degree. It is free from wet processing problems of conventional HI.
STJMMARY OF THE PRESENT INVENTION
In the present system a beam of laser is split into two mutually coherent beams by a beam divider. One of the beams illuminates the diffused reflecting surface of the object. The other beam is spatially filtered and collimated before interference takes place close to zero degree at the CCD faceplate. The object wave is combined with the reference wave to form a speckle interferogram that is converted into a video signal by the photoelectric action of video camera. The video analog output from the camera is fed into the PC based image processing system. In the present invention the time average interferograms are grabbed at frame acquisition rate and subtracted from the just previous time-averaged interferogram. The resultant interferograms are displaced continuously on computer screen at the frame rate 30 images per second. Computer program for interferogram acquisition, processing (evaluation of the interferograms) and displaying the results are written in the Labview environment. The system is optimised to get high contrast fringes.
The subject system is based on the well known principle of interferometry. In this system, optically rough surface of the object is illuminated by laser light. The object wave is combined with the in-line reference wave to form the speckle interferogram that is converted into a video signal by the photo-electric action of the video camera. Fringes are obtained by subtracting two interferograms of the vibrating object. The design of the DSPI system developed by us is such that even if there is change in position (in-plane, out-of-plane, tilt, or combination of the all) of the object is in centimeters the monitoring of vibration of the object is possible.
In all the inventions present in the prior art, the reference interferogram is predetermined and the subsequent interferograms are subtracted continuously from the reference interferogram.
However in the present invention the time-average interferogram of the vibrating surface of the subject instrument over the frame acquisition period (1/30 second) is grabbed and subtracted from the just preceding time-average interferogram in sequential subtraction manner.
Secondly in the inventions known in the prior art, the wavelets used were either Daubechies or Fourier transform filtering which had severe limitations accompanying the resuhs. Kauffmann and Galizzi have used Daubechies(db) wavelet filtering to reduce speckle noise in computer generated speckle correlation fringes. But the db wavelet is not much effective at the edges of the fringes. The Symlet wavelet filtering is more effective at the edges of the fringes in comparison to the Daubechies wavelet. However, despite having many advantages, the DSPI fringes have inherent speckle noise and poor fringe contrast. The present invention applies a new filtering scheme based on wavelet transform to improve the signal-to-noise ratio (SNR) in DSPI interferograms. The invention has capability to take care of small rigid body displacement/rotations of the object, direction of illumination and low frequency fluctuations in the lighting conditions. After recording of interferograms of the object e.g. loudspeaker diaphragm, computer hard disk etc., depending on the amount of speckle noise and texture of the object in the speckle interferograms, the interferograms are processed by a combination of median and Symlet wavelet filtering or average and Symlet wavelet to achieve better accuracy in measurement. In case the speckle noise is moderate, the combination of average and Symlet filtering is used and in case the speckle noise is more then the combinatioft of median and Symlet filtering is used.
OB.IECTS OF THE PRESENT INVENTION
The present invention resides in two embodiments wherein the first embodiment implements:
a. monitoring of vibration and its mode shapes almost in real time. Monitoring of
vibration can be done even if the intensity of light falling on the object is too poor or too
high. The threshold can be set accordingly.
b. if the object is in continuous motion, measurement of vibration with almost zero
error is possible. Maximum speed of the object is equivalent to 140|im/minute continuous
motion of the faceplate of the CCD camera.
c. fringes with relatively high signal-to-noise ratio (SNR) and improved contrast is
obtained without separate processing.
d. the time interval for display and recording the fringes can be adjusted as per
requirement in specific applications (if a data after certain time is important and other data in
between are not of so much importance, only the important data can be displayed and
recorded by setting the time interval for display and recording).
e. while monitoring the vibration, if there is fluctuation in the ambient light, it has
almost no effect as the frame rate of acquisition of specklegram as frame refreshing rate is
quite high.
Accordingly, the present invention relates to a Digital Speckle Pattern Interferometric (DSPI) device for monitoring the vibration and its mode shape in real time comprising of:-
(a) a beam divider for splitting a beam emitted by the laser towards the object into two mutually coherent beams wherein one of the beams illuminates the diffused surface of the object, herein called the object wave,
(b) a spatial filter provided in the path of the second beam to spatially filter and collimate the second beam, herein called the reference wave,
(c) means for combining the object wave with the in-line reference wave to form the speckle interferogram,
(d) means for converting the said speckle interferogram into a video signal,
(e) means for monitoring the vibration and its mode shapes in real time in the event intensity of light falling on the object is either low or high.
(f) means for creating an image for interferogram by subtracting the current image from the reference image and continuing the process by subtracting the resultant image from the previous image and displaying the recorded speckle interferogram on the computer screen in real time at the rate of 30 images per second after histogram equalization.
In the second embodiment automatic filtering of speckle interferogram is implemented and it can measure very large deformations which is not possible by any other commercially available systems.
DETATLED DESCRIPTTON OF THE ACCOMPANY DRAWINGS
Fringe patterns of vibrating loudspeaker (5 mW max., 3 mW min., 47Q, Hi-Fi speaker) diaphragm were recorded. A typical fringe pattern recording of loudspeaker diaphragm (fixed at the outer edge) vibrating at input signal frequency 4.5 kHz and amplitude 700 mVPP (excited by a HP 33120A function generator) is shown in Fig. 1(a).
Result of filtering when Symlet wavelet (sym 5) is applied on the average 5 filtered image is shown in Fig. 1(b). Fig. 1(c) is the image when Symlet wavelet (sym 5) is applied on an image filtered by 3 x 3 median filter.
The fringe patterns of vibrating variable speed motor (60 W, maximum speed 6500 rpm)
bracket were recorded. A typical fringe pattern recording of the vibrating motor bracket is
shown in Fig. 2(a). Result of filtering when Symlet wavelet (sym 5) is applied on the
I average 5 filtered image is shown in Fig. 2 (b). Fig. 2 (c) is the image when Symlet wavelet
(sym 5) is applied on an image filtered by 7 x 7 median filter.
In Fig. 3 (a), the recorded fringe patterns of vibrating rectangular plates (dimension 150 mm X 50 mm x 3 mm) of effective length 106 mm tightened by bolts at one end when exited by a sinusoidal load of 2.4 x 10-3N at frequency 930 Hz (load is applied at a distance 100 mm from the fixed end) is shown. Filtering result when average 3 filtering followed by Symlet wavelet (sym 5) is implemented on the fringe pattern shown in Fig. 3 (a) is shown in Fig. 3 (b). Filtering result when median 3x3 filtering followed by Symlet wavelet (sym 5) is implemented on the fringe pattern shown in 3 (a) is shown in Fig. 3 (c).
From the recorded images of the speckle interferogram it can be observed that the SNR in the speckle interferogram shown in Figure 1 (a) and Figure 2(a) are less than the SNR of the speckle interferogram shown in Fig. 3 (a). Filtering results show that for vibrating objects when Symlet wavelet was applied on the average or median filtered image of the speckle interferogram, the contrast and the SNR improves. Enhancement in contrast and SNR is more when Symlet wavelet was applied on the median filtered image of speckle
interferogram for the case in which SNR in the recorded speckle interferogram was poor. If the SNR in the recorded interferogram is moderate, enhancement in contrast and SNR is more by applying Symlet wavelet filtering on the average filtered image of the speckle interferogram.
For quantitative evaluation purpose, data obtained by both the programs is processed by average/median and Symlet wavelet filtering. From the filtered data the fringe profile can be drawn which improves the accuracy of measurement.
Conventionally used systems can measure deformations only upto 10-15 µm while the subject system can work even up 1000 µm. The subject system is a very precise and cost effective vibration monitoring system, which can be used to measure/detect vibration/deformation in the reflecting or diffused surfaces in any precision engineering applications e.g. computer disks. It can be used as a component of automatic inspection and quality control system.

WE CLAIM:
1. A Digital Speckle Pattern Interferometric (DSPI) device for monitoring the vibrations and mode shape of vibrating surfaces in real time comprising of:
(a) a beam divider for splitting a beam emitted by a laser into two mutually coherent beams wherein one of the beams illuminates the diffused surface of the object, herein called the object wave,
(b) a digital filter provided in the path of the second beam to spatially filter and collimate the second beam, herein called reference wave,
(c) means for combining the object wave with the in-line reference wave to form the speckle interferogram,
(d) means for converting the said speckle interferogram into a video signal,
(e) means for monitoring the vibration and its mode shapes in real time in the event intensity of light falling on the object is either low or high,
(f) means for creating an image for interferogram by subtracting the current image from the reference image and continuing the process by subtracting the resultant image from the previous image and displaying the recorded speckle interferogram on the computer screen in real time at the rate of 30 images per second after histogram equalization.
2. A Digital Speckle Pattern Interferometric (DSPI) device as claimed in claim 1, wherein the the recorded speckle interferograms are processed by a combination of average filtering and Symlet wavelet filtering in case the speckle noise in the recorded speckle interferograms is moderate.
3. A Digital Speckle Pattern Interferometric (DSPI) device as claimed in claim 1, wherein the the recorded speckle interferograms are processed by a combination of median filtering and Symlet wavelet filtering in case the speckle noise in the recorded speckle interferograms is high.
4. A Digital Speckle Pattern Interferometric (DSPI) device as claimed in claim 1, wherein the said isolated pixels in the matrix are removed by element-wise filtering before processing with symlet wave filtering.
5. A Digital Speckle Pattern Interferometric (DSPI) device as claimed in claim 1, wherein the means for converting the speckle interferogram into the video signal
is a CCD camera.
6. A Digital Speckle Pattern Interferometric (DSPI) device as claimed in claim 1, wherein the images created, in the means for creating image by continuous subtraction of images, areis processed in a Personal Computer (PC) based image processing system
7. A Digital Speckle Pattern Interferometric (DSPI) device, substantially as hereinbefore described with reference to the accompanying drawings.

Documents:

925-DEL-2002-Abstract-(07-03-2011).pdf

925-del-2002-abstract.pdf

925-DEL-2002-Claims-(07-03-2011).pdf

925-del-2002-claims.pdf

925-DEL-2002-Correspodence Others-(01-08-2011).pdf

925-DEL-2002-Correspondence-Others-(07-03-2011).pdf

925-DEL-2002-Correspondence-Others-(29-04-2010).pdf

925-del-2002-correspondence-others.pdf

925-del-2002-correspondence-po.pdf

925-del-2002-description (complete).pdf

925-del-2002-description (provisional).pdf

925-del-2002-drawings.pdf

925-DEL-2002-Form-1-(01-08-2011).pdf

925-del-2002-form-1.pdf

925-del-2002-form-18.pdf

925-DEL-2002-Form-2-(01-08-2011).pdf

925-del-2002-form-2.pdf

925-del-2002-form-26.pdf

925-del-2002-form-3.pdf

925-del-2002-form-4.pdf

925-del-2002-form-5.pdf

925-DEL-2002-GPA-(29-04-2010).pdf

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Patent Number

259973

Indian Patent Application Number

925/DEL/2002

PG Journal Number

14/2014

Publication Date

04-Apr-2014

Grant Date

30-Mar-2014

Date of Filing

12-Sep-2002

Name of Patentee

INDIAN INSTITUTE OF TECHNOLOGY

Applicant Address

HAUZ KHAS, NEW DELHI-110 016, INDIA.

Inventors:

#	Inventor's Name	Inventor's Address
1	CHANDRA SHAKHER	INDIAN INSTITUTE OF TECHNOLOGY, HAUZ KHAS, NEW DELHI-110 016, INDIA.

PCT International Classification Number

G06F 15/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA