JP2005537517A - Direct digital holography acquisition of content-based off-axis illuminated objects - Google Patents

Abstract

Systems and methods for content-based fused off-axis illuminated direct digital holography are described. The method calculates and sets the object illumination angle relative to the optical axis (127) defined by the focusing lens (145) as a function of a Fourier-analyzed spatial heterodyne hologram, a content-based including spatial heterodyne fringes for Fourier analysis The axis of the recorded content-based spatial heterodyne hologram, including the spatial heterodyne fringe, is transformed into Fourier space, with the heterodyne carrier frequency defined as the angle between the reference beam and the object beam. Fourier analysis of recorded content-based spatial heterodyne holograms containing spatial heterodyne fringes by being located at the top, applying a digital filter to cut off the signal around the original origin, So Comprising: performing post-inverse Fourier transform.

Description

(Description)
BACKGROUND OF THE INVENTION Field of the Invention This application relates generally to the field of direct digital holography (interferometry). More specifically, the present invention relates to content-based off-axis illumination for direct digital holography.

DESCRIPTION OF RELATED APPLICATIONS Prior art direct digital holography (DDH), sometimes referred to as direct digital interferometry, is well known to those skilled in the art. For example, FIG. 1 shows one schematic embodiment of a DDH system. Light from laser source 105 is magnified by beam expander / spatial filter 110 and travels through lens 115. Thereafter, the expanded and filtered light travels toward the beam splitter 120. The beam splitter 120 may partially reflect. The portion of the light reflected from the beam splitter 120 constitutes an object beam 125 that travels toward the object 130. A portion of the object beam 125 is reflected by the object 130 and travels through the beam splitter 120 toward the focusing lens 145. The light then travels through a focusing lens 145 toward a charge coupled device (CCD) camera (not shown).

  The portion of light from lens 115 that passes through beam splitter 120 constitutes reference beam 135. The reference beam 135 is reflected from the mirror 140 at a small angle. Thereafter, the reference beam 135 reflected from the mirror travels toward the beam splitter 120. Thereafter, the portion of the reference beam 135 reflected from the beam splitter 120 travels through the focusing lens 145 and travels toward the CCD camera (not shown). The object beam 125 from the focusing lens 145 and the reference beam 135 from the focusing lens 145 constitute a plurality of objectives and reference waves 150 and interfere at the CCD to produce a hologram interference pattern as described in US Pat. No. 6,078,392. Give rise to properties.

  In FIG. 1, the object beam 125 is parallel and coincident with the optical axis 127. This type of DDH setting can be referred to as on-axis illumination.

  The limitation of this technology was that the imaging resolution of the DDH system was limited by the optical components of the system. The most notable limitation of optical components is the aperture stop, which is necessary to prevent image quality deterioration due to aberrations. For the two-dimensional Fourier plane, only the spatial frequency of the object in the circle with the radius q0 can be transmitted. For axial illumination, the aperture with radius q0 appears to be centered on zero spatial frequency (q = 0). Therefore, an effort is needed to enable transmission of spatial frequencies outside the circle of radius q0.

SUMMARY OF THE INVENTION The following aspects of the present invention are needed. Of course, the present invention is not limited to these aspects.

  According to one aspect of the invention, the processing calculates the illumination angle relative to the optical axis defined by the focusing lens as a function of data representing a Fourier analyzed spatial heterodyne hologram, and spatial heterodyne for Fourier analysis. Recording content-based spatial heterodyne holograms containing fringes and transforming the axis of the recorded content-based spatial heterodyne holograms containing spatial heterodyne fringes to Fourier space and defining it as the angle between the reference beam and the object beam To analyze the recorded content-based spatial heterodyne hologram containing the spatial heterodyne fringe and to cut off the signal around the original origin by being located at the top of the generated heterodyne carrier frequency Apply digital filter Comprising it and, then, and performing an inverse Fourier transform.

According to another aspect of the invention, a machine includes an interferometer that records a content-based spatial heterodyne hologram including a spatial heterodyne fringe for Fourier analysis, including a focusing lens, and a digital recorder coupled to the interferometer. These and other aspects of the invention comprise a computer that calculates an illumination angle with respect to an optical axis defined by a focusing lens as a function of data representing a Fourier-analyzed spatial heterodyne hologram. Will be better recognized and understood when considered in connection with. The following description, however, is not intended to be limiting, although various embodiments of the invention and many specific details are set forth. Many alternatives, modifications, additions, and / or reconfigurations may be made within the scope of the present invention without departing from the spirit thereof. The present invention includes all such alternatives, modifications, additions and / or reconfigurations.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention and its various features and advantages are more fully described by reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Well-known initial materials, processing techniques, components, and apparatus have been omitted so as not to obscure the present invention in unnecessary detail. However, it should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are exemplary and not restrictive. Various alternatives, modifications, additions and / or rearrangements within the spirit and / or scope of the underlying inventive concept will become apparent to those skilled in the art from this disclosure.

  Within this application, several publications are referenced by Arabic numerals in parentheses. Full citations for these and other publications may be found after the paragraph titled Reference at the end of the specification and immediately preceding the claims. The entire disclosures of all these publications are hereby expressly cited for the purpose of providing a background to the invention and illustrating the state of the art.

  In general, the relevant background of the present invention may include acquiring, storing, and / or reproducing digital data. The relevant background of the present invention may include processing digital data representing an image. Also, relevant background of the present invention may include converting data from multiple images to a composite image.

  The present invention may include a method for obtaining an improved resolution holographic image from a direct digital holography system using off-axis illumination. The present invention may also include an apparatus for acquiring improved resolution holographic images in a direct digital holography (DDH) system using off-axis illumination.

  In general, an object to be observed (imaged) is optically coupled to an illumination source via one or more optical components. As described with respect to FIG. 1, the illumination beam typically passes through the center of the objective lens of interest (ie, the lens system) along the optical axis and thus parallel to the optical axis. This type of DDH configuration can be referred to as “on-axis illumination”, and this configuration obtains the spatial frequency (q) of the object to a certain limit (q0) determined by the aperture of the objective lens. Can do.

  The present invention may include an “on-axis illumination” scenario. In this case, the illumination source is disposed in the horizontal direction so that the beam passes through the objective lens parallel to the optical axis but off the center. Due to the focusing effect of the objective lens, the illumination is incident on the object at an angle with respect to the optical axis. With this eccentric illumination, a higher spatial frequency (q> q0) of the object than in the on-axis illumination can pass through the aperture of the objective lens and can therefore be observed. This is an important advantage of the present invention.

  The present invention may include an extended DDH system (apparatus) adapted to digitally capture on-axis and one or more off-axis illuminated holograms of the same object. The present invention may also include analyzing and / or processing (fusion) digitally captured data. The resulting fusion image encompasses a wider range of spatial frequencies than in any original hologram, thus significantly increasing the nominal imaging resolution of the system compared to when off-axis illumination data is unavailable. .

  As noted above, the imaging resolution of the basic DDH system is limited by the optical components, particularly the aperture stop required to prevent image quality degradation due to aberrations. An aperture stop is required to prevent higher frequency aliasing and subsequent degradation of imaging quality. This means that the optical component of the DDH system can only transmit the spatial frequency of the object in the circle with the radius q0. In the case of on-axis illumination, an opening of radius q0 appears centered at 0 spatial frequency (q = 0). In the case of off-axis illumination, the opening with the radius q0 appears shifted (for example, on the left) in the frequency domain. This suggests that a spatial frequency of q> q0 is transmitted in the direction in which the aperture is shifted. The disadvantage is that spatial frequencies where q is close to q0 are “lost” in the opposite direction. By acquiring a second image in which the illumination is offset in the opposite direction, the aperture appears off (eg, to the right), so the “lost” spatial frequency from the first image has an additional frequency of q0 or higher. To be recovered. As a result of fusing information from two images, one image with better resolution is obtained. Since DDH records phase information on the composite image wave, the information from both (or more) images is fused to yield surprisingly advantageous results. The present invention improves the resolution of general object structures regardless of orientation.

  The present invention may include an extension of the basic DDH system to automatically capture both on-axis and off-axis illuminated holograms. The present invention may also include a method for analyzing and fusing the results of these holograms so that the observed object is displayed at a higher spatial resolution than is available in conventional DDH technology.

  As can be seen in FIG. 1, the object beam 125 is parallel to the optical axis 127. As described above, this setting can be referred to as on-axis illumination. On the other hand, off-axis illumination refers to the case where the object beam 125 is incident on the object 130 at an angle with respect to the optical axis 127 (an example is illustrated by the object teams 215 and 305 shown in FIG. 3). ) There are many ways to achieve off-axis illumination. The approaches presented below are only representative and are therefore intended to be non-limiting examples.

  With reference to FIGS. 2 and 3, one embodiment of an off-axis illumination DDH apparatus is illustrated. 2 and 3, there are two major corrections from FIG. The first correction is that the laser source 105, beam expander / spatial filter 110, and lens 115 are grouped into a movable housing 205 controlled by a computer. The housing 205 is movable along an axis that is practically parallel to the optical axis 127. More specifically, the housing 205 is movable along an axis that is substantially coplanar with the normal of the beam splitter 120.

  With further reference to FIGS. 2 and 3, the second correction point is that an object objective lens 210 is added. In FIG. 2, the laser source housing 205 is arranged so that the object beam 125 is reflected from the beam splitter 120 and passes through the center of the object objective lens 210. Thereafter, the object beam 125 leaves the object objective lens 210 and enters the object 130 around the optical axis 127. In this configuration, on-axis illumination is realized and the system of FIG. 2 is effectively the same as FIG.

  However, in FIG. 3, the laser source housing 205 is offset (up in this particular configuration) so that the object beam 125 passes through the object objective lens 210 off its center. Of course, alternatively, the laser source housing 205 can be offset downward. Due to the focusing characteristic of the object objective lens 210, the object beam 215 leaving the object objective lens 210 is incident on the object 130 at an angle with respect to the optical axis 127, so that off-axis illumination is realized. Thus, the object beam 215 can be incident on an object that is not substantially parallel to the optical axis 127. The object beam 305 reflected from the object passes through the object objective lens 210 from the center and passes again, but due to the optical characteristics of the object objective lens 210 and the focusing lens 150, the CCD (not shown) I) Focus on the top. In the case of off-axis illumination, the diffraction property (1) suggests that the hologram formed in the CCD due to interference between the object beam 305 and the reference beam 135 contains some spatial frequency of the object that is not observed with on-axis illumination. To do.

  Thus, the present invention can include an apparatus operable to digitally record spatial heterodyne holograms including spatial heterodyne fringes for Fourier analysis. The apparatus includes a laser, a beam splitter optically coupled to the laser, a reference beam mirror optically coupled to the beam splitter, an object optically coupled to the beam splitter, a reference beam mirror, and A focusing lens optically coupled to both of the objects, a digital recorder optically coupled to the focusing lens, a computer that performs Fourier transform, applies a digital filter, and performs inverse Fourier transform, see The beam is incident on the reference beam mirror at a non-standard angle, the object beam is incident on the object at an angle with respect to the optical axis defined by the focusing lens, and the reference beam and object beam include a plurality of simultaneous reference and object waves. And is recorded by the digital recorder after being focused on the focal plane of the digital recorder by the focusing lens Forming a spatial heterodyne hologram containing a spatial heterodyne fringe for analysis, and the computer converts the axis of the recorded spatial heterodyne hologram containing the spatial heterodyne fringe to Fourier space, depending on the angle between the reference beam and the object beam It is positioned at the upper end of the specified heterodyne carrier frequency, and the signal around the original origin is cut off before performing the inverse Fourier transform. The apparatus may include an object objective lens optically coupled between the beam splitter and the object. The apparatus can include an aperture stop coupled between the object and the focusing lens. The beam splitter, reference beam mirror, and digital recorder can define a Michelson shape. The beam splitter, reference beam mirror, and digital recorder can define a Mach-Zehnder shape. The apparatus may include a digital storage medium coupled to a computer that performs a Fourier transform, applies a digital filter, and performs an inverse Fourier transform. The digital recorder may include a CCD camera 350 that defines pixels. The apparatus can include a magnifier / spatial filter 230 optically coupled between the laser and the beam splitter. The angle between the reference beam and the object beam and the magnification given by the focusing lens can be chosen so that the digital recorder resolves the features of the spatial heterodyne hologram including the spatial heterodyne fringe for Fourier analysis. Two fringes with two pixels per fringe can be provided to resolve certain features of the digital recorder. The present invention may include a spatial heterodyne hologram created by the above-described apparatus and implemented on a computer readable medium.

  Thus, the present invention can include a method of recording a spatial heterodyne hologram including a spatial heterodyne fringe for Fourier analysis. The method separates the laser beam into a reference beam and an object beam, reflects the reference beam from the reference mirror at a non-standard angle, and targets the object beam at an angle relative to the optical axis defined by the focusing lens. A spatial heterodyne hologram including a spatial heterodyne fringe for Fourier analysis is created by focusing the reference beam and the object beam, which constitute a plurality of simultaneous reference and object waves, in the focal plane of the digital recorder. Fourier analysis by forming and transforming the axis of the recorded spatial heterodyne hologram to Fourier space so that it is located at the top of the heterodyne carrier frequency defined by the angle between the reference beam and the object beam Spatial heterodyes including spatial heterodyne fringes for Includes analyzing the hologram, and applying a digital filter to cut off the signals around the original origin, then, and performing an inverse Fourier transform. The method includes reflecting the object beam from the object at an angle relative to the optical axis defined by the focusing lens and reflecting the object beam from the object at an angle relative to the optical axis defined by the focusing lens. And diffracting the object beam by an object objective lens. Transforming the axis of the recorded spatial heterodyne hologram to Fourier space can include transforming with an extended Fourier transform. The step of digitally recording can include detecting the beam with a CCD camera that defines the pixels. The off-axis illuminated space heterodyne hologram may be an off-axis illuminated space low frequency heterodyne hologram. The phrase low frequency suggests that the fundamental fringe spatial frequency is below the Nyquist sampling limit. The method may also include storing a spatial heterodyne hologram that includes a spatial heterodyne fringe for Fourier analysis. The method may also include reconstructing a Fourier analyzed spatial heterodyne hologram. The method may also include transmitting a Fourier analyzed spatial heterodyne hologram. The method may also include a spatial heterodyne hologram produced by the above method and implemented on a computer readable medium.

In order to use content-based fused off-axis illumination, certain imaging parameters such as off-axis illumination angle and direction must be set. However, there is no optimal set of imaging parameters for all objects, and there is no optimal set of imaging parameters for each part of the same object. Illuminating “all over” valleys and trenches degrades or loses all useful height information. Therefore, there is also a need for efforts to select and / or optimize off-axis illumination parameters for the target object.

  The present invention may include a method for improving holographic imaging of a DDH system that uses off-axis illumination. The method can be implemented in software. The method may include selection of off-axis illumination parameters as a function of the content of the observed object. This method can improve the spatial and height resolution of a direct digital holography (DDH) imaging system using off-axis illumination in a manner that depends on the content of the predetermined object of interest. Improved resolution is achieved through digital processing of a plurality of deterministically selected holograms of a given object captured at various illumination angles. Thus, the present invention can address the need for off-axis illumination parameters determined by the content of the observed object.

  The selection of off-axis illumination parameters may be iterative. Additional off-axis illumination images may be merged to form a composite image. Additional (off-axis) illumination images may be compiled and fused into a composite image, one set or multiple sets at a time.

  The selection of off-axis lighting parameters may be genetic. Multiple composite images may be compiled and compared. One or more illumination parameters used to obtain a fusion image with the best resolution between two or more composite images are used as guide points (eg, endpoints) to further these parameters in subsequent iterations. You may make it optimize. Alternatively, one or more illumination parameters used to obtain a fused image having the worst resolution between two or more composite images may be avoided during subsequent iterations.

  The method may include the following procedures. A holographic imaging system with computer controlled object illumination forms a hologram of the observed object. A digital representation of the hologram is transferred to the computer, and a digital representation of the object wave (ie, image) is reconstructed and stored. The feature of interest may be identified either by the user or by automated processing. Guidance for the feature of interest may be provided by data indicating changes in amplitude and / or phase across two or more adjacent pixels. A sudden change in amplitude and / or phase across two or more adjacent pixels is a good indication of the feature of interest.

  A composite image with improved resolution is calculated by fusing the current image to one or more past images. The composite image and the feature of interest are analyzed and the result of the analysis terminates the process or provides new imaging control parameters. These control parameters indicate the next illumination angle for capturing a new image and may be passed to the holographic imaging system. This process may be repeated. Thus, the present invention can improve holographic imaging performance by adapting off-axis illumination to the characteristics of the observed object.

With reference to FIG. 4, the external view of this invention is shown. The physical components of the present invention may include an object 1, an off-axis illumination direct digital holography (DDH) system 3, and a computer 15 for display, storage, and / or further analysis. The target object 1 is imaged by the off-axis illumination DDH system 3. The off-axis illumination DDH system 3 may be the system shown in FIGS.
Referring again to FIG. 4, the output of the DDH system 3 is a digital hologram 2 which is then passed to the composite image reconstruction stage 5 where a composite digital image 4 of the observed object 1 is calculated. In one embodiment, the composite image reconstruction stage 5 may use Fourier domain image reconstruction, which is now well known to those skilled in the art. It is important that the amplitude of the composite digital image (4) indicates the reflectance of the object 1 and the phase of the composite digital image 4 indicates the height of the object 1.

  Still referring to FIG. 4, the composite digital image 4 is then passed to both the image storage stage 7 and the feature selection stage 9. Image storage stage 7 collects all of the captured images for object 1 in one or more image sets 14. To form a composite image, the image storage stage 7 passes one or more image sets 14 and associated parameters 12 to the fusion algorithm 13. The fusion algorithm 13 computes a higher resolution composite fused image 16 using one or more passed sets of images 14 along with associated imaging control parameters 12 used to capture the images into the sets. In one embodiment, the fusion algorithm 13 may construct the composite fusion image 16 using the Fourier domain approach described in connection with FIGS.

  Referring again to FIG. 4, the fused image 16 may be passed to the imaging parameter selection stage 11 and may also be passed to the display, storage, and / or further analysis stage 15. The stage of feature selection 9 takes a composite digital image 4 and a user input or automatic feature identification 6 as inputs. The purpose of the feature selection step 9 is to identify the feature of interest in the observed object 1. Such features may be identified by the user through a graphical user interface or by automatic image processing. The feature selection stage 9 then passes the feature parameters 8 to the imaging parameter selection stage 11. The imaging parameter selection step 11 takes the feature parameter 8 and the current fusion image 16 as inputs. By analyzing the current fused image 16 relative to the feature parameter 8, the imaging parameter selection step 11 determines whether the process should be stopped if the fused image 16 is determined to be good enough. Alternatively, or instead, it may be determined whether to output a new set of imaging control parameters 12. The new imaging control parameter 12 may instruct the DDH system 2 to capture a new hologram using the off-axis illumination angle specified by the imaging control parameter 12. Once a new digital hologram 2 has been captured, the above process is repeated until the stage of image parameter selection 11 determines that the process should be stopped.

  As a structure that performs the function of aligning the source, beam expander / spatial filter, and lens so that the object beam passes through or off the center of the object objective lens, the disclosed embodiments are A computer-controlled movable housing is shown, but the structure performing the function of aligning the source, beam expander / spatial filter, and lens is such that the object beam passes through or from the center of the object objective lens. There may be other structures that can perform the function of aligning the object beam to pass off, such as beam splitters, mirrors, object objective lenses, objects, focusing. A movable platform that places the lens and CCD camera relative to the source, beam expander / spatial filter, and lens, or another example Movable optical components (e.g., mirrors), or as another example includes a flexible optical fiber and / or cable.

  The terms “a and an” as used herein are defined as one or more. As used herein, the term “plurality” is defined as two or more. As used herein, the term “another” is defined as a second or more. As used herein, the terms “including” and / or “having” are defined as “comprising” (ie, an open language). As used herein, the term “coupled” has been referred to as “connected”, but it is not necessarily direct or mechanical. As used herein, the term “approximately” is defined as at least close to a predetermined value (eg, preferably within 10%, more preferably within 1%, most preferably within 0.1%). The As used herein, the term “substantially” is defined as “largely”, but is not necessarily the entire specified. As used herein, the term “generally” is defined as at least close to a predetermined state. As used herein, the term “deploying” refers to “designing”, “building”, “shipping”, “installing”, and And / or defined as “operating”. As used herein, the term “means” is defined as hardware, firmware, and / or software for achieving a result. The term “program” or “computer program” as used herein is defined as a sequence of instructions designed to execute on a computer system. A program or computer program executes on a subroutine, function, procedure, object method, object implementation, potential application, applet, servlet, source code, object code, shared / dynamic load library, and / or computer system May include other sequences of instructions designed for. As used herein, the term “low-frequency” may be defined as implying that the basic fringe spatial frequency is below the Nyquist sampling limit.

Practical application of the invention Practical applications of the invention that are valuable in science and technology include metrology. The present invention is useful in connection with microelectronic (mechanical) manufacturing, such as for semiconductor testing. The present invention is also useful in connection with nanotechnology research, development, and manufacturing, such as nanovisualization or nanomeasurement. The present invention is useful in connection with interferometers that use digital processing and / or digital data acquisition, such as, for example, direct digital holography tools based on electronic holography. There are virtually countless uses of the present invention, all of which need not be detailed here.

Advantages of the Invention A method, apparatus, and / or computer program that represents an embodiment of the invention may be cost-effective and advantageous for at least the following reasons. The present invention may provide for identifying interesting features of an observed object, either automatically or by user input via a graphical user interface. The present invention can provide control of a holographic imaging system based on identified features to provide content-based resolution improvements. The present invention can provide a feedback path. In the feedback path, the current fusion image is analyzed to determine whether to stop processing or to calculate the best imaging parameters to capture a new hologram. The present invention can provide computer control of object illumination. The present invention can provide for fusing results from multiple holograms. The present invention can provide much higher imaging resolution. The present invention improves quality and lowers costs compared to previous efforts.

  All disclosed embodiments of the invention disclosed herein can be made and used without undue experimentation in light of the disclosure. The present invention is not limited by the theoretical description provided herein. Although the best mode for carrying out the present invention examined by the inventors has been disclosed, the practice of the present invention is not limited thereto. Thus, it will be appreciated by one skilled in the art that the present invention may be practiced otherwise than as specifically described herein.

  Further, each component need not be combined with the disclosed configuration, but could be combined with virtually any configuration. Further, changes may be made in the sequence of steps including the steps or methods described herein. Further, although the devices described herein may be separate modules, it will be apparent that the devices may be integrated into the associated system. Moreover, all disclosed components and features of each disclosed embodiment may be combined with or taken from the disclosed components and features of each of the other disclosed embodiments, except where incompatible with each other. Can be replaced.

  It will be apparent that various substitutions, modifications, additions and / or reconfigurations of features of the invention may be made without departing from the spirit and / or scope of the underlying inventive concept. The spirit and / or scope of the underlying inventive concept as defined by the appended claims and their equivalents covers all such alternatives, modifications, additions, and / or rearrangements. Is considered.

  The appended claims are not expressly stated in a particular claim with the phrase “means for” and / or “step for” as a means plus function limitation It is not to be construed as including such limitation. Dependent embodiments of the present invention are detailed in the appended independent claims and their equivalents. Particular embodiments of the present invention are distinguished from one another by the attached independent claims and the equivalents.

The accompanying drawings, which form a part of this specification, are included to illustrate certain aspects of the present invention. The clearer concepts of the present invention, and the components and operations of the systems provided by the present invention, will be more readily apparent by reference to non-limiting embodiments, which are examples shown in the drawings. Will. The invention will be better understood by reference to one or more of these drawings in combination with the description presented in the specification. Note that the features shown in the drawings do not necessarily follow a uniform scale.
FIG. 1 is a conventional direct digital holography device, appropriately labeled “prior art”. FIG. 2 shows a schematic diagram of an off-axis illumination direct digital holography device (interferometer) in an on-axis position that represents an embodiment of the present invention. FIG. 3 shows a schematic diagram of the off-axis illumination direct digital holography device (interferometer) of FIG. 2 in the off-axis position. FIG. 4 shows a schematic diagram of an off-axis illumination direct digital holography device (interferometer) with multiple illumination sources that represents an embodiment of the present invention.

Claims (27)

A method for recording a content-based off-axis illuminated spatial heterodyne hologram including a spatial heterodyne fringe for Fourier analysis comprising:
Calculating the illumination angle relative to the optical axis defined by the focusing lens as a function of data representing a Fourier-heterospatial spatial heterodyne hologram;
Reflecting the reference beam from the reference mirror at a non-standard angle;
Reflecting the object beam from the object;
Focusing a reference beam and an object beam at the focal plane of a digital recorder to form a content-based off-axis illuminated spatial heterodyne hologram including a spatial heterodyne fringe for Fourier analysis;
Digitally recording content-based off-axis illuminated spatial heterodyne holograms including spatial heterodyne fringes for Fourier analysis. Convert the axis of the recorded content-based off-axis illuminated spatial heterodyne hologram containing the spatial heterodyne fringe to Fourier space so that it is located at the top of the heterodyne carrier frequency defined as the angle between the reference beam and the object beam Fourier-analyzing a recorded content-based off-axis illuminated spatial heterodyne hologram containing spatial heterodyne fringes,
Applying a digital filter to cut off the signal around the original origin, and then
The method of claim 1, further comprising performing an inverse Fourier transform. The method of claim 1, further comprising fusing a Fourier-analyzed content-based off-axis illuminated spatial heterodyne hologram with at least one Fourier-analyzed spatial heterodyne hologram to calculate a single composite image. Method. 4. The method of claim 3, wherein the Fourier analyzed spatial heterodyne hologram comprises a composite image. The method of claim 3, further comprising reproducing a single composite image. The method of claim 3, further comprising transmitting a single composite image. Calculating the illumination angle relative to the optical axis defined by the focusing lens as a function of the data representing the Fourier-analyzed spatial heterodyne hologram comprises selecting a feature of interest from the Fourier-analyzed spatial heterodyne hologram; The method of claim 1. The method of claim 7, wherein the step of digitally recording further comprises detecting the beam with a CCD camera defining pixels. 9. The method of claim 8, wherein the feature of interest is defined by data indicative of a change in at least one element selected from the group consisting of amplitude and phase across at least two pixels. The method of claim 1, further comprising determining whether to record another content-based spatial heterodyne hologram. The method of claim 10, further comprising recording another content-based spatial heterodyne hologram. Convert the axis of other recorded content-based spatial heterodyne holograms, including spatial heterodyne fringes, to Fourier space so that it is located at the top of the heterodyne carrier frequency defined as the angle between the reference beam and the object beam Fourier-analyzing other recorded content-based spatial heterodyne holograms including spatial heterodyne fringes,
Applying a digital filter to cut off the signal around the original origin, and then
The method of claim 11, further comprising performing an inverse Fourier transform. 13. The method of claim 12, further comprising fusing a Fourier analyzed other content-based spatial heterodyne hologram with the Fourier analyzed at least one spatial heterodyne hologram to calculate a single composite image. The method of claim 1, further comprising storing content-based spatial heterodyne holograms including spatial heterodyne fringes for Fourier analysis as digital data. A computer program comprising computer or machine readable program elements convertible to perform the method of claim 1. A machine readable medium comprising data generated by the method of claim 1. An apparatus operable to digitally record content-based off-axis illuminated spatial heterodyne holograms including spatial heterodyne fringes for Fourier analysis,
An illumination source;
A beam splitter optically coupled to the illumination source;
A reference beam mirror optically coupled to the beam splitter;
A focusing lens;
A digital recorder coupled to a focusing lens;
A computer that controls the illumination angle with respect to the optical axis defined by the focusing lens as a function of data representing a Fourier-analyzed spatial heterodyne hologram, performs a Fourier transform, applies a digital filter, and performs an inverse Fourier transform ,
The reference beam is incident on the reference beam mirror at a non-standard angle, the object beam is incident on the object at an angle with respect to the optical axis defined by the focusing lens, and the reference beam and the object beam are focused by the focusing lens on the digital recorder. A content-based off-axis illuminated spatial heterodyne hologram containing a spatial heterodyne fringe for Fourier analysis that is focused on a surface and recorded by a digital recorder is formed, and the computer records a recorded axial envelope containing the spatial heterodyne fringe. The axis of the illumination space heterodyne hologram is transformed into Fourier space so that it is located at the top of the heterodyne carrier frequency defined by the angle between the reference beam and the object beam, and around the original origin before performing the inverse Fourier transform A device that cuts off the signal. The apparatus of claim 17, further comprising an object objective lens optically coupled between the beam splitter and the object. The apparatus of claim 17, wherein each of the plurality of illumination sources includes a laser. The apparatus of claim 17, wherein the digital recorder includes a CCD camera defining pixels. The angle between the reference beam and the object beam and the magnification given by the focusing lens are chosen so that the digital recorder resolves the features of the off-axis illuminated spatial heterodyne hologram including the spatial heterodyne fringe for Fourier analysis, 28. The apparatus of claim 27, wherein two fringes are provided having two pixels per fringe. The apparatus of claim 17, wherein the illumination source is movable relative to the beam splitter. The apparatus of claim 16, wherein the beam splitter, the reference beam mirror, and the digital recorder define a Michelson shape. The apparatus of claim 16, wherein the beam splitter, the reference beam mirror, and the digital recorder define a Mach-Zehnder shape. The apparatus of claim 16, further comprising a digital storage medium coupled to a computer for performing a Fourier transform, applying a digital filter, and performing an inverse Fourier transform. 18. The apparatus of claim 17, wherein the computer calculates an illumination angle relative to the optical axis defined by the focusing lens as a function of data representing a Fourier analyzed spatial heterodyne hologram. A machine readable medium comprising data generated using the apparatus of claim 16.

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