DE102017219091A1 - Method for producing an evaluation image, in particular for holographic microscopy - Google Patents

Abstract

A method for producing an evaluation image (4) of an interference image (2) detected by means of optical interferometry is proposed, which comprises at least the following steps:
- calculating a first Fourier image by means of a Fourier transformation of the interference image (2);
- Computing a second Fourier image (3) by means of a masking (42) of the symmetrical components in a region of the first Fourier image to the first diffraction order (41); and
- Calculating the evaluation image (4) by means of an inverse Fourier transform of the second Fourier image (3). Furthermore, the invention relates to a method for holographic microscopy of an object with an inventively created evaluation image (2).

Description

The invention relates to a method for producing an evaluation image from an interference image acquired by means of an optical interference method, in particular by means of digital holographic microscopy.

In a digital holographic microscopy (abbreviated: DHM), a reference beam and a measuring beam are superimposed and brought to interference. In this case, the measuring beam comprises information about the object to be measured, for example cells.

Due to the mentioned interference, a captured image of the object (interference image) has a wave pattern, in particular a striped pattern. This makes it difficult to detect and measure the object or objects. This problem also exists in other interferometric methods, for example in further holographic measuring methods or in material testing.

The object of the present invention is to provide an evaluation image which enables an improved recognition of objects to be measured, in particular of cells.

The object is achieved by a method having the features of independent claim 1 and by a method having the features of independent claim 11. In the dependent claims advantageous refinements and developments of the invention are given.

• - Berechnen eines ersten Fourierbildes mittels einer Fouriertransformation des Interferenzbildes;
• - Berechnen eines zweiten Fourierbildes mittels eines Ausblendens der symmetrischen Anteile in einem Bereich des ersten Fourierbildes um die erste Beugungsordnung; und
• - Erstellen des Auswertebildes mittels einer inversen Fouriertransformation des zweiten Fourierbildes.

The method according to the invention for producing an evaluation image of an interference image acquired by means of optical interferometry comprises at least the following steps:

• - calculating a first Fourier image by means of a Fourier transformation of the interference image;
• - calculating a second Fourier image by masking out the symmetrical components in a region of the first Fourier image around the first diffraction order; and
• - Creating the evaluation image by means of an inverse Fourier transform of the second Fourier image.

As optical interferometry, any optical method is referred to, which comprises an interference between two light beams, in particular between a reference beam and a measuring beam. In particular, optical interferometry is a digital holographic microscopy.

An interference image is, for example, a two-dimensional image of an interference pattern resulting from the interference. The interference pattern typically includes a plurality of interference fringes, which is also referred to as a fringe pattern or wave pattern.

A Fourier image is a Fourier transform generated image or image. Typically, this is also two-dimensional. The Fourier transformation is preferably carried out as a fast Fourier transform (abbreviated to FFT), for example by means of a computing device.

Diffraction orders, in particular the first diffraction order, correspond to magnitude local maxima within the first Fourier image. Typically, the first Fourier image has a plurality of such maxima which, starting from a zeroth diffraction order (central maximum), are identified by positive and negative numbers, for example first diffraction order (diffraction order N = 1).

Furthermore, it is understood that a light beam, in particular the reference beam or the measuring beam, is regarded as a descriptive model representation of a real spatially extended light beam known to the person skilled in the art.

A hiding of the symmetrical components is at least a partial, in particular a complete, reduction of the symmetrical components of the first Fourier image in said region around the first diffraction order. In particular, the symmetrical components in said region of the first Fourier image can be reduced according to preferred embodiments which are the subject of the dependent claims.

According to the present invention, the second Fourier image is calculated from the first Fourier image by masking out the symmetrical components in a region of the first Fourier image around the first diffraction order. In other words, in the named region, the symmetrical components of the first Fourier image are at least partially, in particular completely, reduced within the region around the first diffraction order. As a result, the asymmetrical components of the first Fourier image in the region around the first diffraction order are advantageously amplified in comparison with the symmetrical components, so that the second Fourier image has asymmetrical components in the region around the first diffraction order.

It is a recognition of the present invention that the symmetrical components belong to the symmetrical wave pattern of the interference pattern are, while the asymmetrical shares go back to the object to be measured or to the objects to be measured. By hiding the symmetrical components in the region around the first diffraction order, the influence of the wave pattern within the evaluation image is thus advantageously reduced. As a result, advantageously, the objects to be measured can be better recognized and measured. This is because it can be better separated from the wave pattern. Thus, the present invention allows the most accurate representation of the object to be measured or the objects to be measured. As a result, in particular, a clearer visualization, for example in medical procedures or material testing, as well as a more accurate determination of geometrical sizes of the objects possible. In particular, its diameter or its cross-sectional area can be determined improved for cells.

From the second Fourier image, the evaluation image is created according to the invention. As a result of the suppression of the symmetrical components provided according to the invention, the wave pattern of the interference image is suppressed, so that the evaluation image is virtually freed from said wave pattern. This allows an improved detection and / or measurement of the object to be measured based on the inventively created evaluation image.

In the method according to the invention for holographic microscopy of one or more objects, at least one interference image of a subarea of the object or at least one of the objects is detected. The method according to the invention is characterized by using an evaluation image prepared according to the present invention or one of its embodiments.

In other words, an evaluation of a holographic microscopy, in particular a digital holographic microscopy, of one or more objects is carried out based on the evaluation image produced according to the present invention or one of its embodiments.

There are the above-mentioned inventive method for creating the evaluation image or one of its configurations similar and equivalent advantages.

Basically, the fading out of the symmetrical components in the region of the first Fourier image about its first diffraction order can take place according to a multiplicity of embodiments.

• - Festlegen einer um die erste Beugungsordnung des ersten Fourierbildes punktsymmetrischen Kontur, insbesondere einer Ellipsenkontur oder einer Kreiskontur, um die erste Beugungsordnung des ersten Fourierbildes;
• - Bestimmen des Minimums m des Betrages der zur festgelegten Kontur zugehörigen komplexen Werte z des ersten Fourierbildes; und
• - Berechnen der Werte w des zweiten Fourierbildes auf der festgelegten Kontur in Abhängigkeit des bestimmten Minimums m.

It is particularly preferred if the hiding of the symmetrical portions comprises at least the following steps:

• Determining a contour which is point-symmetrical about the first diffraction order of the first Fourier image, in particular an elliptical contour or a circular contour, about the first diffraction order of the first Fourier image;
• Determining the minimum m of the amount of complex values z of the first Fourier image associated with the specified contour; and
• Calculating the values w of the second Fourier image on the specified contour as a function of the determined minimum m.

Particularly preferably, the values w of the second Fourier image are calculated on the defined contour by means of w = (| z | -m) · exp (iφ), where z = | z | · Exp (iφ) is.

In other words, a contour, in particular an elliptical contour or a circular contour, which encloses the first diffraction order, is determined around the first diffraction order. The contour is preferably formed closed. Subsequently, the minimum m of the amount of the complex values z arranged on the specified contour is calculated. The thus calculated or determined minimum m is preferably subtracted from the amount of the values z arranged on the contour. The difference thus formed is additionally provided with a complex phase exp (iφ), so that the new values on the contour are given by w = (| z | - m) · exp (iφ). These new values w correspond to the values of the second Fourier image on the specified contour. In other words, the first and second Fourier images match up to the values on the specified contour. On the contour, the first Fourier image has the complex values z and the second Fourier image the complex values w = (| z | -m) · exp (iφ), where m denotes the minimum of the magnitude of the complex values z on the contour. Furthermore, φ denotes the respective phase of the complex values z. As a result of the procedure described, the symmetrical components in the region around the first diffraction order are at least partially blanked out.

Other mathematically equivalent formula expressions and / or numerical factors may be provided. For example, scalings of the above formula expression for the values w are z, | z |, 1 / z and / or 1 / | z | and / or a real or complex factor. Furthermore, an addition or subtraction of a value independent of z is possible (English: offset).

In particular, an average could φ the phases φ of the complex values z determined on the contour to form the complex values w according to w = (| z | - m) · exp (i φ ) be used. Further phases may be provided here, for example a phase which changes as it traverses the contour by 2π or a rational or integer multiple of 2π. In particular, a phase-symmetrical phase with respect to the first diffraction order is advantageous.

Furthermore, instead of an average value, a general complex number could be deducted, that is to say w = z-r * exp [if (k ₁ , k ₂ )] with z = k ₁ + ik ₂ and r, f (k ₁ , k ₂ ) real and arbitrary. In other words, w = z - r · exp [if (z)], where f (z) = 0 is additionally possible, so that a purely real number r is subtracted.

Any combinations of the mathematical embodiments mentioned here are also possible.

For blanking, it is furthermore particularly advantageous to use a plurality of contours concentrically arranged around the first order of diffraction, in particular a plurality of concentric elliptical contours or a plurality of concentric circles arranged around the first order of diffraction.

As a result, the symmetrical components within the range are advantageously more blanked out, as a result of which the evaluation image is advantageously further improved.

• - Bestimmen einer zweidimensionalen Gaußverteilung mit einer bestimmten Amplitude und wenigstens einer oder mehrerer bestimmten Breiten, wobei die zweidimensionale Gaußverteilung um die erste Beugungsordnung des ersten Fourierbildes zentriert und zu dieser punktsymmetrisch ist; und
• - Subtraktion der Werte der zweidimensionalen Gaußverteilung von den entsprechenden Werten des ersten Fourierbildes.

Furthermore, it is advantageous if the hiding of the symmetrical portions comprises at least the following steps:

• Determining a two-dimensional Gaussian distribution having a specific amplitude and at least one or more specific widths, wherein the two-dimensional Gaussian distribution is centered about and point-symmetrical about the first diffraction order of the first Fourier image; and
• Subtracting the values of the two-dimensional Gaussian distribution from the corresponding values of the first Fourier image.

In other words, of the complex values of the first Fourier image in said region around the first diffraction order, the corresponding values defined by the two-dimensional Gaussian distribution are subtracted.

By means of the subtraction of the two-dimensional Gaussian distribution from the values of the first Fourier image around the first diffraction order, the symmetrical components are reduced by the first order of diffraction.

wobei A die Amplitude, σ die Breite und (µ₁, µ₂) die zweidimensionale Koordinate der Position bezeichnet. Das Tupel (k₁, k₂) korrespondiert zum komplexen Wert z = k₁+ik₂ des ersten Fourierbildes.A two-dimensional Gaussian distribution typically has an amplitude, a width and a position, wherein the position is a two-dimensional coordinate and corresponds to the position of the maximum value (amplitude) of the two-dimensional Gaussian distribution. In other words, for example, for a symmetrical two-dimensional Gaussian distribution that has circular contours (circular contours): $$G\left(k_1.k_2\right)=A\cdot e^{-\left[{\left(k_1-{\mathrm{\mu }}_1\right)}^2+{\left(k_2-{\mathrm{\mu }}_2\right)}^2\right]\text{/}\left(2{\mathrm{\sigma }}^2\right)}$$

where A denotes the amplitude, σ the width and (μ ₁ , μ ₂ ) the two-dimensional coordinate of the position. The tuple (k ₁ , k ₂ ) corresponds to the complex value z = k ₁ + ik _{2 of} the first Fourier image.

By centering the two-dimensional Gaussian distribution about the first diffraction order, the position of the first diffraction order corresponds to the position of the two-dimensional Gaussian distribution. The width of the Gaussian distribution is determined in a Gaussian distribution with elliptical contours by two widths in two mutually independent directions. In addition, the elliptical Gaussian distribution can be rotated arbitrarily. Furthermore, the width of the Gaussian distribution can be determined by its full width at half maximum (abbreviated to FWHM).

It is particularly preferred if the amplitude and / or the width of the two-dimensional Gaussian distribution is / are determined by an optimization of the calculated evaluation image.

In other words, in a first step, the amplitude and the width of the two-dimensional Gaussian distribution can be determined. Subsequently, the evaluation image is hereby calculated, wherein the amplitude and width of the two-dimensional Gaussian distribution are changed in such a way until a defined optimum of the calculated evaluation image is achieved. In particular, the optimum is to be determined in such a way that the objects to be measured remain clearly visible and the image background, in particular the wave pattern, is almost completely blanked out.

In particular, the width or the majority of the widths of the Gaussian distribution is point-symmetrical with respect to the first order of diffraction. Furthermore, an additional complex phase, for example as explained above, can be provided for the said Gaussian distribution.

• - Bereitstellen eines Referenzinterferenzbildes;
• - Berechnen eines Referenzfourierbildes mittels einer Fouriertransformation des Referenzinterferenzbildes; und
• - Subtraktion der Werte des Referenzinterferenzbildes von den entsprechenden Werten des ersten Fourierbildes.

According to an advantageous embodiment of the invention, the hiding of the symmetrical portions comprises at least the following steps:

• - Providing a reference interference image;
• - calculating a reference Fourier transformation image by means of a Fourier transformation of the reference interference image; and
• Subtracting the values of the reference interference image from the corresponding values of the first Fourier image.

In other words, a reference interference image acquired without the object to be measured is provided. The reference interference image therefore has no object to be measured or no objects to be measured. As a result, the reference interference image mainly comprises the unwanted wave pattern.

The Fourier transformed reference interference image (reference Fourier image) is subtracted from the corresponding values of the first Fourier image, thereby calculating the second Fourier image. Since the reference Fourier image mainly comprises the symmetrical components of the interference pattern, the said subtraction reduces the symmetrical components of the first Fourier image. In other words, the second Fourier image, which is calculated by the said subtraction from the first Fourier image, has significantly smaller symmetrical components around the first diffraction order. In other words, evaluation image = IFFT [(FFT (interference image) - FFT (reference interference image)], where FFT is the fast Fourier transform and IFFT is the inverse fast Fourier transform.

In an advantageous embodiment of the invention, the values of the first Fourier image are set to the value zero in a further region which comprises the zeroth diffraction order.

As a result, the contrast of the evaluation image is advantageously increased. This is because the background of the interference image is darkened or suppressed.

According to an advantageous embodiment of the invention, the amount of the evaluation image is calculated.

The amount of the evaluation image corresponds to its brightness. Advantageously, thereby the object or the objects within the evaluation image can be detected improved.

In an advantageous development of the invention, a low-pass filtering of the second Fourier image takes place transversely to the interference fringes of the interference image.

As a result, advantageously still remaining minor artifacts or remnants of the wave pattern within the evaluation image can be further reduced.

• 1 ein gemäß einer Ausgestaltung der Erfindung erstelltes zweites Fourierbild;
• 2 ein gemäß einer ersten Ausgestaltung der Erfindung erstelltes Auswertebild;
• 3 ein gemäß einer zweiten Ausgestaltung der Erfindung erstelltes Auswertebild;
• 4 ein gemäß einer dritten Ausgestaltung der Erfindung erstelltes Auswertebild;
• 5 eine Übersichtstabelle der verschiedenen Ausgestaltungen bezüglich des Ausblendens der symmetrischen Anteile; und
• 6 ein Flussdiagramm des erfindungsgemäßen Verfahrens zur Erstellung eines Auswertebildes.

Further advantages, features and details of the invention will become apparent from the embodiments described below and with reference to the drawings. Shown schematically:

• 1 a second Fourier image created according to an embodiment of the invention;
• 2 a generated according to a first embodiment of the invention evaluation image;
• 3 a generated according to a second embodiment of the invention evaluation image;
• 4 a generated according to a third embodiment of the invention evaluation image;
• 5 an overview table of the various embodiments with respect to the blanking of the symmetrical components; and
• 6 a flowchart of the inventive method for creating an evaluation image.

Similar, equivalent or equivalent elements may be provided with the same reference numerals in one of the figures or in the figures.

The 1 shows a second Fourier image created according to an embodiment of the invention 3 ,

At the abscissa 101 and the ordinate 102 of the second Fourier image 3 in each case a wave number or a circular wave number or a wavelength is plotted in arbitrary units.

The second Fourier image 3 has in the illustrated section a first diffraction order 41 , a minus first diffraction order 39 and a zeroth order of diffraction 40 on. An exemplary area around the first diffraction order 41 is marked by a dashed line.

The second Fourier image 3 was masked by masking the symmetrical portions in the area around the first diffraction order 41 calculated from a Fourier-transformed interference image (first Fourier image).

The interference image was provided in this embodiment by digital holographic microscopy. The objects to be measured are cells in the illustrated embodiment, in particular red blood cells.

Preferably, the hiding of the symmetrical components takes place around the first diffraction order 41 by concentric about the first diffraction order 41 arranged elliptical contours, in particular circular contours, by means of the subtraction of a first diffraction order 41 centered two-dimensional Gaussian distribution and / or by means of a subtraction of a Fourier-transformed reference interference image.

In the other figures, these mentioned methods for masking the symmetrical components around the first diffraction order 41 illustrated and explained.

2 shows an interference image detected by digital holographic microscopy 2 , Here are the objects to be measured cells, especially red blood cells. As from the interference picture 2 can be seen, this has a typical formed from strip wave pattern, which adversely reduces the visibility and Vermessbarkeit the illustrated and measured objects.

By the inventively provided hiding 42 the symmetrical components around the first diffraction order of the Fourier-transformed interference image 2 (First Fourier image), the wave pattern, which essentially corresponds to the symmetrical portions, is significantly reduced, so that the recognizability of objects in the created evaluation image 4 opposite to the original interference image 2 is significantly improved.

In the in 2 In the embodiment shown, the symmetrical components are determined by means of a plurality of circular contours arranged concentrically around the first diffraction order by determining the minimum of the magnitude of the complex values z associated with one of the defined circular contours and subtracting the thus determined minimum from the absolute value hidden from the circle contours complex values. Furthermore, the difference formed is multiplied by exp (iφ). In other words, for the values w of the second Fourier image on the defined circle contours, w = (| z | -m) · exp (iφ), where z = | z | · Exp (iφ) is. As a result, the symmetrical components are advantageously hidden or reduced.

The 3 shows an evaluation image created according to a second embodiment of the invention 4 ,

In 3 the hiding is done 42 the symmetric components around the first diffraction order of the second Fourier image by means of a subtraction of a two-dimensional Gaussian distribution centered around the first diffraction order. In this case, the amplitude and the width of the two-dimensional Gaussian distribution with respect to the recognizability of the objects within the evaluation image 4 optimized. As a result, advantageously in the original interference pattern 2 reduced to recognizing wave pattern, whereby the recognizability of the objects, in particular the cells, is improved.

4 shows an evaluation image created according to a third embodiment of the invention 4 ,

In 4 Hiding took place 42 the symmetric components around the first diffraction order by means of the subtraction of a reference interference pattern. The reference interference image was detected and provided by a preliminary measurement (interference between measuring beam and reference beam without objects), which took place without the objects to be measured. The thus-detected reference interference image is Fourier-transformed and from the Fourier-transformed interference image 2 , which comprises the objects to be measured, subtracted in Fourier space. As a result, the symmetrical components about the first diffraction order can advantageously also be blanked out or reduced, which in turn improves the recognizability of the objects, in particular of the cells and their visualization.

5 shows an overview table of the particularly advantageous three possible methods for masking the symmetric components to the first diffraction order. The object to be measured is an example of an erythrocyte.

The summary table has three columns C1 , ..., C3 as well as four lines R1 , ..., R4 on.

The entries of the first column C1 correspond to the respective interference pattern. The entries in the second column each show a binary image of a created evaluation image. The entries of the third column C3 show a section of the binary image through the center of the object to be measured.

The first line R1 corresponds to a known method. In binary image ( R1 . C2 ) of the known evaluation image ( R1 . C1 ) clear artifacts can be seen. In particular, the diameter of the cell can only be determined insufficiently.

The second line R2 corresponds to the first embodiment of the invention (see. 2 ). In this case, the symmetrical components around the first diffraction order are masked out or reduced by means of concentric circular contours, as described above. It is a clear improvement of the binary evaluation image ( R2 . C2 ) in comparison to the known binary evaluation image ( R1 . C2 ) the first line R1 recognize. In particular, the diameter of the cell is more accurately determinable.

The third line R3 corresponds to the second embodiment of the invention (see. 3 ). In this case, the hiding of the symmetrical components takes place by means of a subtraction of a two-dimensional Gaussian distribution. Especially in the associated section ( R3 . C3 ) is a significant improvement compared to the known evaluation image ( R1 . C1 ) or to the section ( R1 . C3 ) to recognize.

The fourth line R4 corresponds to the third embodiment of the invention (see. 4 ). In this case, the hiding of the symmetrical components takes place about the first diffraction order by means of a subtraction of a Fourier-transformed reference interference image. Again, one of the known method (first line R1 ) to see significant improvement in the detectability and determinability of the diameter of the cell.

In 6 a flowchart of the inventive method for creating the evaluation image is shown.

First, an interference image is provided, in particular by means of digital holographic microscopy. In this case, the interference image can comprise one or more objects to be measured, in particular cells, as an image.

In a first step S1 In the method according to the invention, a first Fourier image is calculated by means of a Fourier transformation of the interference image.

In a second step S2 In the method according to the invention, a second Fourier image is calculated by masking out or reducing the symmetrical components in a region of the first Fourier image around the first diffraction order.

In a third step S3 In the method according to the invention, the evaluation image according to the invention is created by means of an inverse Fourier transformation of the second Fourier image.

The implementation of the above-described processes or method steps, in particular the calculation of the first and / or second Fourier image as well as the generation of the evaluation image by means of the inverse Fourier transformation, can be carried out on the basis of instructions written on computer-readable storage media or in volatile computer memories (collectively referred to as computer-readable storage) ), in particular a computing device. In particular, a fast Fourier transformation (FFT) is provided for generating or calculating the first and / or second Fourier image.

Computer-readable memories are, for example, volatile memories such as caches, buffers or RAMs as well as non-volatile memories such as removable data carriers or hard disks. The functions or method steps described above can be in the form of at least one instruction set in or on a computer-readable memory. The functions or method steps are not bound to a specific instruction set or to a specific form of instruction set or to a specific storage medium or to a specific process or to a specific execution scheme and may be due to software, firmware, microcode, hardware, processors or integrated circuits in the Operating alone or in any combination.

Various processing strategies can be used here, for example serial processing by a single processor, multiprocessing, multitasking or parallel processing. The instructions can be stored in local memories. It is also possible to remove the instruction remotely and access it like a network (cloud).

The term computing device as used herein includes processors and processing means in the broadest sense, for example, servers, general purpose processors, graphics processors, digital signal processors, application specific integrated circuits (ASICs), programmable logic circuits such as FPGAs, discrete analog or digital circuits, and any combinations thereof, including all other processing means known to the skilled person or developed in the future. In particular, the Fourier transforms or the creation of the evaluation image can take place by means of a quantum computer. Basically, processors can include one or more devices. If a processor includes multiple devices, these may be configured to process instructions in parallel or sequentially.

Although the invention has been further illustrated and described in detail by the preferred embodiments, the invention is not limited by the disclosed examples, or other variations can be derived therefrom by those skilled in the art without departing from the scope of the invention.

Claims (11)

Method for producing an evaluation image (4) of an interference image (2) detected by means of optical interferometry, comprising the steps: - calculating a first Fourier image by means of a Fourier transformation of the interference image (2); - Computing a second Fourier image (3) by means of a masking (42) of the symmetrical components in a region of the first Fourier image to the first diffraction order (41); and - Creating the evaluation image (4) by means of an inverse Fourier transform of the second Fourier image (3). Method according to Claim 1 in which the masking (42) of the symmetrical components comprises at least the following steps: - defining a contour which is point-symmetrical about the first diffraction order (41) of the first Fourier image, in particular an elliptical contour or a circular contour; Determining the minimum m of the amount of complex values z of the first Fourier image associated with the specified contour; and - calculating the values w of the second Fourier image (3) on the specified contour as a function of the determined minimum m. Method according to Claim 2 in which the calculation of the values w of the second Fourier image (3) on the defined contour is effected by means of w = (| z | -m) · exp (iφ), where z = | z | · Exp (iφ) is. Method according to Claim 2 or 3 in which a plurality of contours, in particular a plurality of elliptical contours or a plurality of circular contours, is used, wherein the contours are arranged concentrically around the first diffraction order (41) of the first Fourier image. Method according to Claim 1 in which the masking (42) of the symmetrical portions comprises at least the following steps: - determining a two-dimensional Gaussian distribution having a specific amplitude and one or more specific widths, the two-dimensional Gaussian distribution being centered and centered around the first diffraction order (41) of the first Fourier image this is point-symmetrical; and subtracting the values of the two-dimensional Gaussian distribution from the corresponding values of the first Fourier image. Method according to Claim 5 in which the amplitude and / or the width of the two-dimensional Gaussian distribution is / are determined by an optimization of the calculated evaluation image (4). Method according to Claim 1 in which the masking (42) of the symmetrical components comprises at least the following steps: - providing a reference interference image; - calculating a reference Fourier transformation image by means of a Fourier transformation of the reference interference image; and subtracting the values of the reference interference image from the corresponding values of the first Fourier image. Method according to one of the preceding claims, in which the values of the first Fourier image are set to the value zero in a further region comprising the zeroth diffraction order (40). Method according to one of the preceding claims, in which the amount of the evaluation image (4) is calculated. Method according to one of the preceding claims, in which further low-pass filtering of the second Fourier image (3) takes place transversely to the interference fringes of the interference image (2). Method for holographic microscopy of an object, in which at least one interference image of a partial area of the object is detected, characterized by using one according to one of the Claims 1 to 10 created evaluation image (4).

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