WO2015165471A1

WO2015165471A1 - Contiguous diffractive images with reduced speckle

Info

Publication number: WO2015165471A1
Application number: PCT/DK2015/050107
Authority: WO
Inventors: Jesper GLÜCKSTAD
Original assignee: Danmarks Tekniske Universitet
Priority date: 2014-04-28
Filing date: 2015-04-27
Publication date: 2015-11-05

Abstract

There is presented a method for providing an intensity pattern (Ioutput), such as an image, more particularly a contiguous intensity pattern with reduced speckle. The method comprises encoding a spatial light modulator (SLM) with a modulation pattern so as to form the intensity pattern as a diffraction pattern, where the method furthermore comprises shaping (GPC) an input beam so that the point spread function in the output region where the diffraction pattern is formed has suppressed side lobes, such as the point spread function being substantially rectangular in shape, and wherein the method furthermore comprises tiling the modulation pattern so that the spacing between the individual point spread function corresponds to their widths. An effect of this may be that the output pattern is formed as a pattern of closely spaced point spread functions, which enables forming a contiguous pattern with reduced speckle.

Description

CONTIGUOUS DIFFRACTIVE IMAGES WITH REDUCED SPECKLE

FIELD OF THE INVENTION

The present invention relates to a method for image generation, and more particularly to a method for, apparatus for and use of diffractive image

generation.

BACKGROUND OF THE INVENTION For many purposes, it is relevant to produce high quality images. On such method, Computer Generated Holography (CGH) is a method of digitally generating holographic interference patterns. A holographic image can be generated e.g. by digitally computing a holographic interference pattern and printing it onto a mask or film for subsequent illumination by suitable coherent light source.

An improved method for producing images would be advantageous, and in particular a more efficient and/or reliable method for producing contiguous images and/or for reducing speckle would be advantageous.

SUMMARY OF THE INVENTION

In particular, it may be seen as an object of the present invention to provide a method for providing images, such as an output intensity pattern that may enable realizing one or more of the objects mentioned above.

It is a further object of the present invention to provide an alternative to the prior art. Thus, the above described object and several other objects are intended to be obtained in a first aspect of the invention by providing a method for providing an output intensity pattern, such as a contiguous output intensity pattern, in an output region, the method comprising :

- receiving an input intensity pattern,

- receiving an input beam of electromagnetic radiation, - providing a spatial light modulator

- generating a modulation pattern at the spatial light modulator, so that a diffraction pattern of the modulation pattern corresponds to the input intensity pattern,

- encoding the input beam by

i. shaping, such as optically shaping, the input beam so as to achieve that a shaping profile in one or two dimensions is provided to at least a portion of the input beam whose optical paths traverses the spatial light modulator, so as to suppress side-lobes of a point spread function in the output region in one or two or three dimensions,

ii. modulating, such as optically modulating, the input beam, with the modulation pattern at the spatial light modulator, so as to provide a shaped and modulated input beam, - providing with the shaped and modulated input beam the output intensity pattern in the output region as a diffraction pattern of the modulation pattern,

wherein the method further comprises

- tiling the modulation pattern so that a spacing of a sampling lattice in the output region substantially corresponds to, such as corresponds to, such as being equal to, a width of a main lobe of the point spread function in the output region.

The invention may particularly, but not exclusively, be advantageous for enabling providing an output intensity pattern in the output region, such as a contiguous output intensity pattern in the output region. The invention may furthermore particularly, but not exclusively, be advantageous for reducing speckle in the output region. It may be seen as an insight made by the present inventor, that shaping the input beam so as to suppress side-lobes of a point spread function in the output region may advantageously be combined with tiling the modulation pattern, in particular combining so that a spacing of a sampling lattice in the output region substantially corresponds to a width of a main lobe of the point spread function in the output region. An advantage thereof may be, that an output pattern may be provided as a pattern of pixels defined by the point spread function, with reduced side-lobes, which are only overlapping to a limited extent, such as not overlapping, and which therefore may lead to reduced speckle, but which at the same time may enable providing contiguous patterns because the point spread functions can be placed close to each other, such as immediately adjacent each other.

The steps are not necessarily arranged in the order in which they occur.

It may, for example, be understood that encoding and tiling takes place temporally before providing the output pattern, such as temporally before providing the (real) output pattern in the output region. This may for example be the case where the modulation motif is calculated (such as calculated in a computer based on computer generated holography (CGH)), in which case the modulation motif (data) could be calculated or computated based on the input intensity pattern (data), and the modulation motif could then be tiled to generate the modulation pattern (data) and subsequent thereto the modulation pattern (real) could be realized (or generated) at the SLM whereafter it can be encoded by the input beam (real), which input beam (real) in turn is transformed into the modulated input beam (real) with which the output pattern (real) is provided in the output region (real) as the interference pattern (real) of the modulation pattern (real) at the SLM. It may furthermore be understood that shaping may take place temporally before, after, simultaneously, partially overlapping and/or fully overlapping with modulating. Output pattern may be interchangeably used with output intensity pattern (I₀utput(x, y, z)). By 'modulation motif may be understood a pattern for which modulation motif the diffraction pattern corresponds to the input intensity pattern (data), i.e., the modulation motif may be employed to reconstruct the the input intensity pattern and. Furthermore, the modulation motif may be tiled (for example, a modulation pattern may be provided by tiling at least twice so that Nt-x x Nt-_y, such as 2 x 2, modulation motifs are generated at the SLM) to form the modulation pattern, comprising multiple tiled modulation motifs, encoded at the SLM.

By 'providing an output intensity pattern in the output region' may be understood a process of generating an intensity pattern, such as an intensity pattern in the output region which intensity pattern substantially corresponds, such as corresponds to the input intensity pattern. In other words, a user may input an input intensity pattern as information (where 'information' may be used

interchangeably with 'data'), such as a set of information of corresponding desired intensity values and spatial coordinates enabling identifying a pattern which the user would like to generate in the output region, such as data corresponding to (or descriptive of) an intensity pattern. An example of such a pattern may, for example, be given by a two dimensional monochrome image where each pixel in a discretized two-dimensional grid is assigned an intensity value. The method may then enable providing a real-world intensity pattern in the output region which intensity pattern substantially corresponds, such as corresponds to the input intensity pattern. It may be understood by the skilled person, that under practical circumstances there may not necessarily be exact identity between an (ideal) input intensity pattern and a corresponding output intensity pattern in the output region, such as the provided 'output intensity pattern in the output region', since fundamental physical laws, such as described by the Maxwell equations, may impose limits on the capabilities of optical systems.

A 'contiguous output intensity pattern' is understood as is common in the art, and may be understood as a pattern where different parts of the pattern are coherent, such as where 'coherent' in this specific context of 'contiguous output intensity pattern' may be understood as connected to each other (elsewhere 'coherent' is understood as is common within the art of optics, such as relating to or composed of waves having a constant difference in phase). Thus, it may be understood that different parts of the output intensity pattern may be touching along a boundary or at a point. It may in particular be understood that immediately adjacent pixels, such as two nearest neigbour pixels are touching along a boundary or at a point. By touching may in this context be understood, that the intensity along a line connecting the maxima of the two pixels is non-zero all the way along said line. Thus, for a sequence of immediately adjacent pixels, such as 3 pixels with one pixel in the middle and its two nearest neighbours on either side, the intensity profiles of the pixels is touching or connected throughout an unbroken sequence.

By 'an output region' may be understood a region in which the output intensity pattern may be formed. The output region may be an image plane as is known in the art for a two-dimensional intensity pattern, but may also be a volume for a three-dimensional intensity pattern.

By 'receiving an input intensity pattern' or 'receiving input intensity pattern data' may be understood, that the method comprises receiving as an input a desired intensity pattern, such as a user defined desired pattern, which the user would like to be provided as an output intensity pattern in the output region. It may be understood that the input intensity pattern is provided as information (where 'information' may be used interchangeably with 'data'), such as a set of information of corresponding desired intensity values and spatial coordinates enabling identifying a pattern which the user would like to generate in the output region, such as data corresponding to (or descriptive of) an intensity pattern

'Receiving an input beam of electromagnetic radiation' is understood as is common in the art, such as said input beam being a real input beam of

electromagnetic radiation. It may be understood that the present invention may not be limited to generating the input beam. In an embodiment, there is provided a step of providing the input beam of electromagnetic radiation, such as via emitting the input beam of electromagnetic radiation from a laser.

By 'a spatial light modulator' which in the present application is used

interchangeably with 'spatial electromagnetic radiation modulator' is understood a spatial light modulator (SLM) as is known in the art. It is understood that the spatial EMR modulator may be provided in a number of embodiments including embodiments with movable parts, such as one or more movable mirrors, or embodiments with spatially distributed and electrically addressable elements which change their properties in terms of optical path length, transmittance, and/or reflectivity upon activation. The spatial variations of optical characteristic across the spatial EMR modulator may in specific

embodiments be known as a hologram. In a particular embodiment, there is provided a system, wherein the spatial EMR modulator comprises diffractive optics (which is described in the reference WO2003/034118 Al, which is hereby incorporated by reference in entirety). According to some embodiments of the invention the spatial electromagnetic radiation modulator is configured for encoding a pattern, such as the modulation pattern and/or the modulation pattern and a pattern for at least partially shaping the input beam, as any one of scalar amplitude pattern, a phase pattern, a polarization pattern singly or in any combination. It may thus be understood, that the SLM may be capable of and configured for encoding the modulation pattern alone, but may also be capable of and configured for enconding the modulation pattern and furthermore at least part of a pattern for shaping. It is noted that the modulation pattern may be an interference pattern, such as a digitally computed holographic interference pattern.

According to some embodiments of the invention the spatial electromagnetic radiation modulator is configured for at least partially modulating an input beam, such as for at least partially shaping and modulating an input beam, such as providing a substantially non-flat phase profile and/or a non-flat scalar amplitude profile to the input beam.

According to some embodiments of the invention the spatial electromagnetic radiation modulator is configured for at least partially modulating an input beam, such as for at least partially shaping and modulating an input beam by providing concurrent phase and scalar amplitude modulation, such as by means of two spatial modulation-subunits arranged for allowing concurrent phase and amplitude shaping and/or modulation of the incoming beam.

According to some embodiments of the invention, the spatial electromagnetic radiation modulator is configured for providing spatial polarization shaping and/or modulation. It is noted that the spatial shaping and/or modulation of the input beam can be done by a spatial electromagnetic radiation modulator, such as described in the reference "Real-time interactive 3D manipulation of particles viewed in two orthogonal observation planes", Ivan R. Perch-Nielsen, Peter John Rodrigo, and Jesper Gluckstad, 18 April 2005 / Vol. 13, No. 8 / OPTICS EXPRESS 2852, the contents of which are hereby incorporated by reference. In a particular embodiment, the spatial EMR modulator comprises a system for providing diffractive beam shaping, such as a system for diffractive optics, such as a system for Fourier holography, such as a system for Fresnel holography, such as a system for holographic optical scattering. Advantages of employing diffractive optics may include compactness in the setup with few additional optical elements required.

In general, the spatial shaping and modulation could be carried out with known spatial light modulators including Liquid Crystal SLMs (LC-SLMs), Micro Electro- Mechanical Systems SLMs (MEMS-SLMs), deformable mirror SLMs, Acousto-Optic SLMs (AO-SLMs), or other types of SLMs.

According to another embodiment of the invention, there is provided a system wherein the spatial electromagnetic radiation modulator is arranged for applying, such as applies, a spatial shaping and/or modulation of the targeting EMR, such as the incident electromagnetic radiation, by changing its properties locally, such as an electrically or optically addressed spatial light modulator. A spatial light modulator typically operates according to the principles of light diffraction wherein each elementary unit (e. g., a pixel) of the modulator locally modulates the phase of a portion of a light beam impinging thereon, to provide a predetermined light profile. According to this particular embodiment, the modification of the EMR, such as light, does not involve moving an element of the spatial light modulator spatially. Rather a local property (such as transparency or optical path length) of the elementary unit is changed.

It is noted that 'Electromagnetic radiation' (EMR) is well known in the art. EMR is understood to include various types of electromagnetic variation, such as various types corresponding to different wavelength ranges, such as radio waves, microwaves, infrared radiation, EMR in the visible region (which humans perceive or see as 'light'), ultraviolet radiation, X-rays and gamma rays. The term optical is to be understood as relating to light. EMR is also understood to include radiation from various sources, such as incandescent lamps, LASERS and antennas. It is commonly known in the art, that EMR may be quantized in the form of elementary particles known as photons. In the present application, the terms 'light' and 'optical' is used for exemplary purposes. It is understood, that where 'light' or 'optica l' is used it is only used as an exam ple of EMR, and the invention is understood to be applica ble to a lso other wavelength interva ls where reference is made to 'light' or 'optica l'. In other words, EMR a nd light are used interchangea bly in the present application .

Amplitude is to be understood as is common in the art, i .e. , as a com plex am plitude Uo being g iven by

Uo(r) = Ao(r)exp(i<po(r))

Where Ao is or may be a spatially dependent vector representative of the d irection and a mplitude of the electric field in a g iven position, i .e., a vector whose length and d irection may vary with respect to spatial position, φ₀ is initial phase which in a sim ilar ma nner is or may be spatially dependent.

By the bold notation is ind icated vectorial properties as is known in the art. The magnitude or disturbance U(r,t) may be given for a point in space and time may then be g iven

U(r,t) = Uo(r) e'^- O

Where k is wavevector, r is position (such as where r corresponds to a vector from origo, a nd thus corresponds to a position such as a position g iven by coordinates (x,y,z)), t is time, and ω is tempora l frequency.

It is further understood, that said amplitude makes no reference to pola rization, i .e. , any spatially varying polarization profile is conceivable a nd encom passed by the present invention . In em bodiments, a particular polarization profile may be applied . In some embodiments, the polarization profile is inhomogeneous across the wavefront. It may in pa rticular be noted that both conventional a nd

unconventional polarization states, also known as "vector beams", are conceivable and encompassed by the present invention . In contrast to conventional polarization states, such as linear, circular or elliptical polarizations, which can be uniquely described by a specific point on the surface of the Poincare sphere, the vector beams, have a spatial inhomogeneous polarization state, and therefore can not be described by a point, but rather by a number of points on the Poincare sphere.

By 'a modulation pattern' may be understood a pattern as is known in the a rt, such as a two-dimensiona l pattern com prising binary or m ultilevel va lues. A diffraction pattern of the modulation pattern may correspond to the input intensity pattern.

By 'generating a modulation pattern at the spatial light modulator' may be understood encoding the SLM with the modulation pattern, such as so that the SLM can encode the input beam with the modulation pattern, e.g., a phase such the modulated input beam is provided.

By 'so that a diffraction pattern of the modulation pattern corresponds to the input intensity pattern' may be understood that diffraction pattern resulting from the modulation pattern, such as the resulting diffraction pattern when the input beam and/or the shaped input beam is diffracted by the modulation pattern, where it is understood that the diffraction pattern corresponds to the input intensity pattern. This may, for example, be realized by Computer Generated Holography (CGH) as is known in the art, and is the method of digitally generating holographic interference patterns.

By 'encoding the input beam' may be understood as is common in the art, such as receiving the input beam and changing a profile of the beam so as to correspond to a shaping profile and/or a modulation pattern.

By 'shaping the input beam' may be understood applying one or more optical operations to the beam, such as passing the beam through an optical filter for chancing the phase profile, a scalar amplitude profile and/or a polarization profile.

By 'shaping' may in general be understood 'spatial shaping' whereby may understood that the properties of the input, such as scalar amplitude, phase or polarization other parameters is changed, e.g. by a GPC setup and/or by a spatial EMR modulator (such as at least partially by the same SLM as is carrying out the modulation with the modulation pattern).

The shaping may be carried out by directly applying the shaping profile, such as by passing the input beam through a filter with a spatially varying transmittance function corresponding to a desired scalar amplitude profile. The shaping may be carried out in multiple steps, such as by passing the input beam through a filter with a spatially varying transmittance function

corresponding to a desired scalar amplitude profile and passing the input beam (before or subsequently) passing the input beam through a filter with a spatially varying phase mask, so as to provide a beam with a spatially varying phase and scalar amplitude. It may be understood, that in such multiple step approach, either of the scalar amplitude filter or phase filter may identical to the SLM which also carries out the modulation of the input beam with the modulation pattern (which may be either of a modulation pattern given by scalar amplitude or phase).

The shaping may be carried out, e.g., by means of a Generalized Phase Contrast (GPC) setup. GPC is understood as is known in the art. An advantage of

employing GPC may be that the shaping profile may be provided in an energy efficient manner, such as without blocking substantial amounts of light.

By 'so as to achieve that a shaping profile is provided' may be understood that the shaping is carried so as to achieve that a certain profile - the shaping - profile is provided or encoded in the input beam. It may be understood, that the shaping may be carried out in numerous ways, as is known to the skilled person, e.g., by using the SLM, optionally in combination with other optical elements, such as a further SLM. As an alternative, a GPC setup may be used.

By Ίη one or two dimensions' may be understood that the shaping may be done in e.g., one dimension, such as one dimension orthogonal to a direction of

propagation of the input beam, such as in two dimensions, such as two

dimensions orthogonal to a direction of propagation of the input beam.

By 'is provided to at least a portion of the input beam whose optical paths traverses the spatial light modulator' may be understood that the shaping portion of the input beam which is subjected to shaping at least comprises a portion of the input beam whose optical paths traverses, such as propagates through the spatial light modulator.

It may furthermore be understood, that the shaping may be carried out before the SLM, at the SLM and/or after the SLM. For example, a scalar amplitude shaping may take part before the SLM, where the SLM completes the shaping by furthermore carrying out a phase shaping of the input beam, so as to shape the input beam which provides a shaping profile with both a scalar amplitude profile and a phase profile, such as a complex amplitude profile.

By 'so as to suppress side-lobes of a point spread function in the output region' may be understood that the shaping serves to suppress, such as reduce, such as reduce an energy content of, side lobes of a point spread function in the output region, such as relative to an input beam which is not shaped, such as relative to an input beam having a flat profile, or a rectangular profile (such as a flat profile being truncated at the SLM), or a Gaussian profile, or a Gaussian profile which is truncated at the SLM. It is understood, that the side-lobes must be seen in relation to the main lobe of the point spread function. It is further understood, that suppressing side-lobes of a point spread function in the output region entails reducing an amount of energy in the side-lobes relative to an amount of energy in the main lobe. An advantage of suppressing side-lobes may be that their energy may be better used. Another advantage of suppressing side-lobes may be, that it enables reducing speckle. The shaping profile may be a SINC like profile, such as a profile being symmetrical and/or having a main lobe which is larger than any sidelobes and/or having portions of opposite phase with respect to each other, such as a profile being described by a SINC function. Alternatively, the shaping profile may be a JINC profile.

It may be understood that side-lobes of a point spread function may be

suppressed in the output region, such as in one or two dimension, such as in one or two or three dimensions.

By Ίη one or two or three dimensions' may be understood that the output pattern which is provided in the output region may be one dimensional, such as varying in only one direction in an image plane, or two-dimensional, such as representing a two-dimensional image in an output region being an image plane, such as three- dimensional, such as representing a 3D image or volume in an output region being a three-dimensional volume. It may for example be understood that a first output intensity pattern can be provided at a 2D plane at depth zi and a second output intensity pattern can be provided at a 2D plane at depth z₂=zi+dz. Thus, by adding output intensity patterns (such as adding 2, 3, 5, 10, 100 or more output intensity patterns) in dedicated planes being adjacent (but distributed along the z-axis), it may be possible to provide 3D imaging with reduced speckle. It is furthermore understood that the point spread function may have a

component in the z-axis direction (as well as along the lateral xy-axes).

By 'modulating the input beam' may be understood encoding the input beam with the modulation pattern at the spatial light modulator. By 'modulation' of EMR is in general understood that the direction, intensity, phase or other parameters of the EMR is changed, such as changed with respect to time so that microscopic objects which change position (such as being moved by the trapping means) over time may be targeted or trapped, such as followed in space by the targeting and/or trapping means over time.

According to some embodiments of the invention the spatial electromagnetic radiation modulator is configured for providing a modulated EMR beam, such as modulated light beam, having a substantially flat intensity profile but non-flat phase profile. In particular embodiments, the spatial electromagnetic radiation modulator is configured for providing a phase-only modulation wherein only the phase varies across a spatial electromagnetic radiation modulator (i.e., non-flat phase-profile). In particular embodiments, all other optical characteristics are substantially constant across the modulator. In particular exemplary embodiments of the present invention the spatial light modulator is approximated by a phase- only modulation of an input laser beam in a discrete pixel matrix. Phase-only modulation allows the entire incoming beam power to be diffractively distributed between the stimulation points with minimal power loss.

By 'so as to provide a shaped and modulated input beam' may be understood that the shaping and modulation serves to provide a shaped and modulated input beam. It may be understood, that the shaping and modulating may be carried out in separate steps, such as first receiving the input beam, shaping the input beam into a shaped input beam and then modulating the shaped input beam into a modulated and shaped input beam, or vice versa. It may be understood that the shaping and modulating may be carried out in the same step, such as using a phase and scalar amplitude spatial light modulator, which at the same time and position carries out the shaping and the modulation. It may be understood that the shaping and modulating may be overlapping, such as a part of the shaping being carried out before or after the modulating at the SLM, and a remaining part of the shaping being carried out at the SLM at the same time and place as the modulating.

By 'providing with the shaped and modulated input beam the output intensity pattern in the output region as a diffraction pattern of the modulation pattern' may be understood that the diffraction pattern of the modulation pattern which is read out with the shaped input beam provides the output pattern in the output region. The diffraction may in exemplary embodiments be described as Fresnel diffraction as is known in the art or Fraunhofer diffraction as is known in the art. It may be understood, that the output intensity pattern is a diffraction pattern of the modulation pattern (which is read out with the shaped beam or the beam which is shaped after being modulated). Thus, the output intensity pattern is not the diffraction pattern of a (any) beam. However, it may be understood, that the output intensity pattern is provided via (or by means of) the shaped and modulated beam. By 'tiling the modulation pattern' may be understood that the modulation pattern is tiled, such as at least partially repeated at the spatial light modulator in a least one direction, such as tiled to fill the spatial light modulator in one or two directions. It is thus understood, that the modulation pattern is tiled, or at least partially repeated in at least one direction. It is thus understood, that tiling implies that the modulation pattern is at least partially repeated. Thus, 'no tiling' implies that a the modulation pattern appears only once (modulation pattern appears 1 time), whereas tiling implies that the modulation pattern appears more than once (modulation pattern appears more than 1 time). It is understood that a factor indicating the number of times the modulation pattern appears is greater than 1 due to the tiling, but it is not necessarily an integer. Said factor is hereinafter referred to as 'number of tilings' (Nt) where a 'number of tilings' of 1 corresponds to 'no tiling' (and where it is understood that 'tiling' implies Nt > 1, such as Nt at least 2). In embodiments, the modulation pattern is tiled, such as the modulation motif is tiled, so that said number of tilings may be described with a positive integer, such as said positive integer being 2, 3, 4, 5, 6, 7, 8, 9 or 10, 100 or larger.

In embodiments, the number of tilings implies that the modulation pattern appears a number of times in one or two directions which may be described with a real value, which need not be confined to whole numbers. This may be referred to as fractional tiling.

In embodiments, the number of tilings implies that the modulation pattern appears an equal number of times in both directions.

An advantage of tiling may be that it enables increasing the spacing of a sampling lattice in the output regions by an amount proportional to the number of tilings. The increasing in spacing is provided along each dimension corresponding to the number of tiling along said dimension. The tiling does not affect the resolution.

By 'spacing of a sampling lattice in the output region' may be understood the distance between the individual point spread functions in the output lattice, such as between individual "pixels" or "voxels" in the output region. It may be understood, that this spacing may be controlled, such as increased, by tiling. By 'pixel' may be understood as is common in the art as a picture element. It may furthermore be understood, that a 'pixel' in the present context corresponds to a point spread function. For example, an output intensity pattern may be given by an array of pixels, such as an array of (spatially, such as spatially in a 2D plane) distributed point spread functions, such as point spread functions which may be of similar or non-similar intensity. Therefore, the 'point spread function' may correspond to the 'pixel intensity profile'. A 'voxel' is understood as is common in the art to be a 3D pixel. By 'a width of a main lobe of the point spread function' may be understood the full width at half of the maximum (FWHM) as is common in the art.

By 'so that a spacing of a sampling lattice in the output region substantially corresponds to, such as corresponds to, such as being equal to, a width of a main lobe of the point spread function in the output region' may be understood that the tiling is arranged with respect to the width of the main lobe of the point spread function, so that adjacent point spread functions are placed substantially adjacent each other, so as to neither substantially overlap, such as overlap, nor having a substantial gap, such as a gap, between them. An advantage of this may be that it enables forming a substantially contiguous, such as contiguous pattern of closely spaced point spread functions, such as point spread functions with suppressed side-lobes. An advantage of the suppressed side-lobes may be that it enables reducing speckle. By 'so that a spacing of a sampling lattice in the output region substantially corresponds to, such as corresponds to, such as being equal to, a width of a main lobe of the point spread function in the output region' may be understood that the spacing of a sampling lattice may be no more than 50 %, such as 40 %, such as 30 %, such as 25 %, such as 20 %, such as 15 %, such as 10 %, such as 5 %, such as 2.5 %, such as 1 %, such as 0.5 % , such as 0.1 % larger or smaller than a width of a main lobe of the point spread function. It may generally be understood, that the method may be carried out with or without one or more lenses in the optical path between the SLM and the diffraction pattern.

According to a first aspect of the invention there is provided a method (M) for providing an output intensity pattern (Ioutput(x,y,z)), such as a contiguous output intensity pattern, in an output region (Reoutput), the method comprising :

- Receiving (SO) input intensity pattern (Iin_Put(x,y,z)) data,

- Receiving (SI) an input beam ( Bmput) of electromagnetic radiation,

- providing (S2) a spatial light modulator (SLM),

- generating (S3) a modulation motif and tiling it to form a modulation pattern (Pa_m) encoded at the spatial light modulator (SLM), so that a diffraction pattern (DF) of the modulation pattern (Pa_m)

corresponds to the input intensity pattern (I in_Put(x,y,z)),

- shaping, such as optically shaping, and modulating, such as optically modulating, (S4) the input beam ( Bmput) by

i. shaping (S5) the input beam so as to achieve that a shaping profile in one or two dimensions (Sprofiie) is provided to at least a portion of the input beam (Bmput) whose optical paths traverses the spatial light modulator, wherein the shaping (Sprofiie) profile may be described mathematically by a SINC function or a JINC function, ii. modulating (S6) the input beam (Bmput), with the modulation pattern (Pa_m) at the spatial light modulator (SLM), so as to provide a shaped and modulated input beam (smBmput),

- providing (S7) with the shaped and modulated input beam (smBmput) the output intensity pattern (Ioutput(x,y,z)) in the output region (Reoutput) as a diffraction pattern (DF) of the modulation pattern (Pa_m),

wherein said tiling comprises

- tiling (S8) the modulation motif to form the modulation pattern (Pam), such as tiling (S8) the modulation motif in one or two dimensions to form the modulation pattern (Pa_m), so that

i. the width Asinc of the SINC or JINC mainlobe of the shaping function, where said width Asinc of the SINC or JINC mainlobe is understood to be the width between the first two zero- crossings, across the spatial light modulator in at least said one direction, such as two directions,

ii. the width Dmotif of the modulation motif in the corresponding direction or directions,

are substantially related by, such as related by:

Asinc ~ 2Dmotif

such as substantially related by, such as related by:

Asinc = 2D motif.

In the present context, the width Asinc may refer to the width of a SINC of JINC mainlobe, but for conciceness of notation, reference is made to "SINC" only in the index (although it could alternatively be written as Asinc for the SINC option and Ajinc for the JINC option or in general Asincjinc to cover both options).

It may in general be understood that a spacing (A) of a sampling lattice in the output region (Reoutput) substantially corresponds to, such as corresponds to, such as being equal to, a width (w) of a main lobe of the point spread function (PSF) in the output region (Reoutput), where said width (w) of a main lobe of the point spread function (PSF) in the output region (Reoutput) is the full width at half of the maximum (FWHM), In an embodiment, there is provided a method, wherein one or more composants of the shaping profile are complex valued.

By 'composants of the shaping profile' may be understood that the shaping profile may differ for different composants of the input beam, such as for different composants corresponding to one, two or three geometrical dimensions, which may for example be relevant in case the input beam is a vector beam with spatially varying composants, where it is understood, that the shaping profile may correspond to a separate coding of each composant in the input beam .

By 'complex valued' may be understood that the shaping profile represents a profile which is a profile in both scalar amplitude and phase.

In an embodiment, there is provided a method, wherein different regions within the shaping profile have substantially opposite phase, such as opposite phase.

By 'different regions within the shaping profile' may be understood that different regions may correspond to different areas within the portion of the input beam which traverses the SLM.

By 'opposite phase' may be understood a phase difference of % (pi) radians corresponding to 180 degrees.

A possible advantage of having different regions within the shaping profile, which have substantially opposite phase may be that it enables that these different portions may interfere negatively at the output region. This may in turn enable providing advantageous point spread functions, such as substantially rectangular shaped point spread functions. In an embodiment, there is provided a method, wherein the shape of the shaping profile (Sprofiie) leads to a point spread function in the output region (Reoutput) where a slope of a main lobe of the point spread function at half of the maximum of the main lobe is steeper than a slope at half of the maximum of a

corresponding SINC function with similar maximum and similar full width at half maximum, such as the main lobe of the point spread function (PSF) is more rectangular in shape than a main lobe of a SINC function, such as the main lobe of the point spread function having a top-hat-like shape.

In an embodiment, there is provided a method, wherein the shape of the shaping profile leads to a point spread function in the output region (Reoutput) where the main lobe of the point spread function (PSF) is more rectangular in shape than a main lobe of a SINC function, such as the main lobe of the point spread function having a top-hat-like shape. By 'shape of the shaping profile leads to a point spread function' may be understood that the shape of the shaping profile is responsible for the shape of the point spread function, as is generally known. For example, a top-hat shape leads to a PSF with a shape as a SINC function, and vice versa. By 'main lobe' may be understood the main portion of the PSF, such as a middle portion of the PSF which lies between the first two local minima on each side of the center of the PSF.

By 'more rectangular in shape than a main lobe of a SINC function' may be understood that the sides, such as the slope of the main lobe at the half max, of the main lobe are steeper, such as the sides of the main lobe are steeper and a function value between the sides being more constant (such as the top being flatter). It may in particular by understood, that the degree to which a main lobe may be rectangular, may be assessed by fitting a rectangular function to the main lobe, and calculating the total deviation, such as the total deviation being calculated as an integral of the numerical (so as to take into account that the deviation can be positive and negative, and that contributions in both directions should be taken into account so as to add up without cancelling each other) local deviation, where a more rectangular function naturally leads to lower values of this integral of the total deviation.

By 'the main lobe of the point spread function having a top-hat-like shape' may be understood that the main lobe of the PSF may substantially correspond to a top- hat like shape, such as a boxcar shape, such as a rectangular shape, such as the shape of a RECT function. A possible advantage of having a substantially rectangularly shaped PSF may be that it enables forming the output intensity pattern as an array of closely spaced, rectangularly shaped "building blocks" or pixels or voxels, which due to their rectangular shape may closely fit to each other, so as to minimize any gaps or overlaps between them. In combination with the reduced side-lobes, this may enable forming a substantially contiguous pattern with little or no speckle.

In an embodiment, which may be a preferred embodiment, there is provided a method, wherein the shaping profile may be described mathematically by a SINC- like function, such as a SINC function.

In an embodiment, which may be a preferred embodiment, there is provided a method, wherein the shaping profile may be described mathematically by a SINC function.

In an embodiment, which may be a preferred embodiment, there is provided a method, wherein the shaping profile may be described mathematically by a JINC- like function, such as a JINC function. By 'SINC may be understood the SINC function as is known in the art, such as (when described with reference to the x-direction) :

such as (when described with reference to the x- and y-directions (where it corresponds to a diffraction pattern of a rectangular or square aperture)) :

SINC(x,y) = (5ίη(πχ)/ πχ)(5ίη(πν)/ πy) .

An advantage of having the shaping profile correspond to the SINC function may be, that the corresponding PSF is a top-hat function. Thus, having the shaping profile being described mathematically be a SINC function enables forming the PSF as a top-hat function, or a top-hat like function when taking into

consideration that for practical purposes and ideal top-hat like function may not be achievable. It may by understood when referring to the SINC function, that it includes at least a portion of the side lobes, such as different portions with different phase with respect to each other. In alternative embodiments, there is provided a method, wherein the shaping profile may be described mathematically by an apodized SINC function, such as a SINC function where a window function has been applied. An advantage of this may be, that it reduces effect of the abruct truncation applied by the SLM.

In an alternative embodiment, the shaping profile may be described

mathematically by a JINC function as is known in the art.

It may be understood that modifications, such as trivial modifications, to any one of the above-mentioned functions, such as the SINC and JINC functions, may be conceivable and is encompassed by the present invention, such as scaling, translation, applying an offset in value and/or position etc.

In an embodiment, there is provided a method, wherein

- a ratio Ro of the aperture width D of the SLM in at least one direction, such as two directions, with respect to the width Asinc of the sine mainlobe across the spatial light modulator, in at least said one direction, such as two directions, such as Ro being at least 1, such as Ro, being larger than 1, such as Ro being at least 2, such as Ro being larger than 2, such as Ro being at least 2, 3, 4, 5, 6, 7, 8, 9 or 10, 50 or 100, and

- a number of tilings (Nt) where the number of tilings (Nt) is greater than unity (Nt > 1), such as the number of tilings (Nt) being at least 2 (Nt > 2), such as the number of tilings (Nt) being an integer which is at least 2 (Nt > 2), of the modulation pattern in the given direction

are substantially related by, such as related by:

2Ro ~ Nt

such as substantially related by, such as related by:

2Ro = Nt.

It may be understood, that R0 may be positive integer, but that it may also be a real number, e.g ., decimal numbers such as 1.5, 5.5, 10. 75, etc. An advantage of having R0 being a large number (e.g ., corresponding to the aperture width D of the SLM being much larger than the width of the main lobe of the SINC or JINC), may be that it enables forming a very well defined top-hat function as the PSF and/or that it enables that the values of the SINC or JINC function has decreased towards the edges of the SLM aperture, so that the SINC or JINC is less abruptly cut off. An advantage of having R0 being a small number (e.g., corresponding to the aperture width D of the SLM being similar to the width of the main lobe of the SINC or JINC), may be that it enables keeping a relatively large, scalar, numerical amplitude across the SLM (i.e., with only a relatively small amount of relatively low-amplitude side-lobes). It may in general be understood that certain entities may be two-dimensional, such as the width of the SLM aperture, the number of tilings, the width of the mainlobe of the PSF (such as the SINC or JINC mainlobe). The invention may relate to any one dimension of these two dimensional entities. However, in particular embodiments, the numerical values of one or more of these entities are similar or even identical in both dimensions.

By 'width of the SINC mainlobe' (where the SINC in this context describes the shaping profile - not the PSF) may be understood the width between the first two zero-crossings (such as the portion between the two most central zero-crossings). For an offset SINC function, it may be understood that the width of the mainlobe of such offset SINC corresponds to the width for the corresponding non-offset SINC. 'Width of JINC mainlobe' may be understood in an analogous manner.

A possible advantage of arranging the ratio Ro and the number of tilings (Nt) as described above, may be that it facilitates that the point spread functions in the output pattern are closely spaced, such as minimizing overlaps and/or gaps between the PSFs or pixels or voxels.

This may further be described in the following calculations:

The width Axsinc of the sine mainlobe in the shaping profile is related to the top-hat width 2wx (wx is half-width) in the x-direction as

AXsinc,x = λΖ / Wx

where λ (lambda) is wavelength of light, and z is the observation distance. The rectangular sampling lattice in the hologram plane has spacings:

AXspacing = Nt-χλί / Dx

where f is focal length of the lens, Nt,x is number of tilings in the x-direction and Dx is aperture width of the SLM in the x-direction.

In order to the PDFs in the output region to be closely spaced, it is required, that the top-hat width is substantially equal (~) to, such as equal (=) to,the spacing in the output plane:

2Wx ~ AXspacing =>

2λζ/ ΔΧ₅ίηο,χ ~ Ν.-χλί/ Dx O

2 f/ AXsincx ~ Nt-χλί / Dx o , z = f

2 / AXsinc,x ~ Nt-x / Dx =>

The width Axsinc of the sine mainlobe may be rewritten in terms of the ratio Ro of the aperture width D_x of the SLM in the x direction with respect to the width Axsinc of the sine mainlobe:

2 / AXsinc,x ~ Nt-x / Dx =>

2 / (Dx / Ro) ~ Nt-x/ Dx o , AXsincx = D_x / Ro

2Ro ~ Nt-x

It is noted, that for an arrangement where the SINC function has zero crossings on the edges of the aperture of the SLM aperture, the width Axsinc of the sine mainlobe may be rewritten in terms of the number of zero-crossings No within the SLM (including the zero-crossings on the edge of the aperture) and the aperture width Dx of the SLM in the x direction:

2 / AXsinc,x ~ Nt-x / Dx =>

2 / (2Dx / No) ~ Nt-x/ Dx o , Ax_Sinc,x = 2D_X / No

No ~ Nt-x

In an embodiment, there is provided a method, wherein

- a number of zeroes (No) of the SINC function in a given direction across the spatial light modulator, such as No being at least 2, such as No being larger than 2, such as No being at least 2, 3, 4, 5, 6, 7, 8, 9 or 10, 50 or 100, and

are substantially related by, such as related by:

No ~ Nt

such as related by

No = Nt.

It is noted that:

2Ro Nt-x , from the calculations above

2DX/ASII Nt-x , via definition of Ro defined above

AsiNC 2Dx/Nt-x

AsiNC 2Dmotif-x , where Dmotif-x = D_x/Nt-x.

In an embodiment, the number of tilings (Nt) is less than 100, such as within 2- 100, such as less than or equal to 50, such as within 2- 50, such as less than or equal to 10, such as within 2- 10, such as less than or equal to 5, such as within 2- 5, such as 2 or 3 or 4 or 5. In an embodiment, there is provided a method, wherein shaping the input beam is carried out so that a further shaping profile is provided to the input beam so as to suppress ripple of the point spread function (PSF) in the output region (Reoutput), such as said further shaping profile being a window function, such as any one of Bartlett, Blackman, Connes, Cosine, Gaussian, Hamming, Hanning, Butterworth. By Vipple' may be understood small unwanted residual spatially periodic variation of the PSF in the output region, which may be due to truncation by the finite size SLM.

By 'a window function' may in general be understood a function serving to minimize the ripple caused by the truncation by the finite size SLM. Window functions are well known in the art.

A possible advantage of applying the window function may be that it enables reducing ripple of the PSF in the output region. In an embodiment, there is provided a method, wherein shaping the input beam comprises applying one or more of:

- a profile of scalar amplitude, such as passing the portion of the input beam (Bmput) whose optical paths traverses the spatial light modulator through an optical element with a spatially varying amplitude transmittance function,

- a profile of polarization,

- a profile of phase.

It may be noted, that shaping may involve subjecting the beam to masks which may or may not be similar to the shaping profile. For example, when using a GPC setup for providing the shaping profile, the masks may not necessarily be identical to the shaping profile provided to the input beam.

Patterns of amplitude, phase and polarization may be provided as is known in the art.

In an embodiment, there is provided a method, wherein modulating the input beam (Bmput) comprises applying the modulation pattern (Pa_m), where the modulation pattern (Pa_m) is given as one or more of:

- a pattern of scalar amplitudes,

- a pattern of polarization,

- a pattern of phase.

In an embodiment, there is provided a method, wherein the shaping profile comprises:

- a profile of scalar amplitude and a profile of phase,

and wherein the modulation pattern (Pa_m) comprises:

- a pattern of phase.

In the present embodiment, the shaping profile comprises both a profile of scalar amplitude and a profile of phase, such as would for example be the case for a SINC or JINC function. The modulation pattern comprises a pattern of phase. This may for example be realized by using a GPC setup for providing the shaping profile to the input beam so as to provide a shaped input beam and then using the spatial light modulator to provide the modulation pattern to this shaped input beam so as to provide a shaped and modulated input beam. The sequence may also be the opposite, i.e., SLM for modulation and then GPC for shaping.

Alternatively, a transmittance filter may provide a spatially varying, constant phase semi-shaped beam, and the SLM may provide both shaping-phase, so as to provide the shaped input beam and the modulation pattern phase, so as to provide the modulated beam, so as to effectively provide the shaped and modulated input beam.

In an embodiment, there is provided a method, wherein the shaping profile and the modulation pattern (Pa_m) comprises, respectively,

- a profile of scalar amplitude and a pattern of scalar amplitude, or

- a profile of scalar amplitude and a pattern of phase, or

- a profile of scalar amplitude and a pattern of polarization, or

- a profile of phase and a pattern of scalar amplitude, or

- a profile of phase and a pattern of phase, or

- a profile of phase and a pattern of polarization, or

- a profile of polarization and a pattern of scalar amplitude, or

- a profile of polarization and a pattern of phase, or

- a profile of polarization and a pattern of polarization.

It may furthermore be understood that further combinations are conceivable and encompassed by the present invention, such as, e.g., wherein the shaping profile is given by a profile of scalar amplitude and phase, and wherein the modulation pattern is given by a pattern of scalar amplitude.

In embodiments, the shaping is carried out with a smaller frequency, such as the shaping being quasi-static, such as static, compared to the modulation pattern, such as the modulation with the modulation pattern being dynamic.

In an embodiment, there is provided a method, wherein the diffraction is any one of:

- Fraunhofer diffraction, such as Fraunhofer diffraction with lenses or

Fraunhofer diffraction without lenses, and

Fresnel diffraction, such as Fresnel diffraction with lenses or Fresnel diffraction without lenses. 'Fresnel diffraction' is understood as is known in the art. It may be understood, that Fresnel diffraction may involve lenses or may not involve lenses.

'Fraunhofer diffraction' is understood as is known in the art. It may be

understood, that Fraunhofer diffraction may involve lenses or may not involve lenses.

In an embodiment, there is provided a method, wherein the output intensity pattern is provided as a :

- A Fraunhofer hologram, such as a Fraunhofer hologram generated with lenses or a Fraunhofer hologram generated without lenses, or

- A Fresnel hologram, such as a Fresnel hologram generated with

lenses or a Fresnel hologram generated without lenses. A 'Fresnel hologram' is understood as is known in the art. A 'Fraunhofer hologram' is understood as is known in the art.

For an example of Fresnel holography benefitting from tiling, reference is made to the article "Shifted Fresnel diffraction for computational holography", by Richard P. Muffoletto et al., OPTICS EXPRESS 5631, Vol. 15, No. 9, 2007, which reference is hereby incorporated by reference in entirety.

In an embodiment, there is provided a method, wherein the method is further comprising :

- Providing a lens (L), said lens having a focal length (fiens), - Placing said lens in an optical path between

i. the spatial light modulator (SLM), where a distance between the spatial light modulator and the lens substantially corresponds to the focal length (fiens), such as corresponds to the focal length (fiens), and

ii. the output region (Reoutput), where a distance between the output region (Reoutput) and the lens substantially corresponds to the focal length (fiens), such as corresponds to the focal length (fiens),

and wherein the step of - providing with the shaped and modulated input beam (smBinput) the output intensity pattern (Ioutput(x,y,z)) in the output region (Reoutput) as a diffraction pattern of the modulation pattern,

comprises

- focusing the shaped and modulated input beam (smBinput) on the output region (Reoutput) with the lens (L).

A possible advantage of applying a lens may be that it enables a more compact setup. In an embodiment, there is provided a method, wherein the shaped and modulated input beam does not traverse any lenses, such as wherein the diffraction is Fresnel diffraction. An advantage of this embodiment may be, that it is simple since it renders lenses superfluous. In an embodiment, there is provided a method, wherein the method comprises generating the modulation pattern by an iterative technique, such as any one of:

o iterative Fourier transform algorithm (IFTA),

o Gersberg-Saxton,

o direct binary search,

o simulated annealing.

According to a second aspect of the invention, there is provided an apparatus for receiving an input intensity pattern and for receiving an input beam (Bmput) and for providing an output intensity pattern (I_output(x,y,z)), such as a contiguous output intensity pattern (Ioutput(x,y,z)), in an output region (Reoutput) in response thereto, said apparatus comprising :

- A spatial light modulator (SLM),

- Means, such as a fixed modulation mask, a GPC setup and/or a

spatial light modulator, for shaping the input beam so as to achieve that a shaping profile in one or two dimensions (Sprofiie) is provided to at least a portion of the input beam (Bmput) whose optical paths traverses the spatial light modulator, so as to suppress side-lobes of a point spread function (PSF) in the output region (Reoutput) in one or two or three dimensions, A processor operably connected to at least the spatial light modulator, such as to the spatial light modulator and to the means for shaping the input beam, and the processor being arranged for enabling receiving the input beam (Bmput) and providing a shaped and modulated input beam (smBmput) by

i. shaping the input beam so as to achieve that a shaping

profile in one or two dimensions (Sprofiie) is provided to at least a portion of the input beam (Bmput) whose optical paths traverses the spatial light modulator, so as to suppress side- lobes of a point spread function (PSF) in the output region (Reoutput) in one or two or three dimensions, and

ii. modulating the input beam (Bmput), with the modulation

pattern (Pa_m) at the spatial light modulator (SLM), and the processor further being arranged for enabling :

iii. tiling the modulation pattern so that a spacing (Δ) of a

sampling lattice in the output region (Reoutput) substantially corresponds to, such as corresponds to, such as being equal to, a width of the point spread function (PSF) in the output region (Reoutput),

so as to enable providing with the shaped and modulated input beam (smBinput) the output intensity pattern (I_output(x,y,z)) in the output region (Reoutput) as a diffraction pattern of the modulation pattern. By 'Means for shaping the input beam so as to achieve that a shaping profile in one or two dimensions is provided' may in exemplary embodiments be understood any one or a combination of a fixed modulation mask (such as a modulation mask for modying any one or a combination of scalar amplitude, phase and

polarization), a GPC setup and/or a spatial light modulator.

By 'processor' may be understood a processor as is known in the art, optionally operatively connected to instructions, such as computer program code, such as software. According to a second aspect of the invention, there is provided an apparatus for receiving an input intensity pattern (Iin_Put(x,y,z)) and for receiving an input beam (Binput) and for providing an output intensity pattern (Ioutput(x,y,z)), such as a contiguous output intensity pattern (Ioutput(x,y,z)), in an output region (Reoutput) in response thereto, said apparatus comprising :

- A spatial light modulator (SLM), such as a spatial light modulator for modulating the input beam (Binput),

- Means, such as a fixed modulation mask, a GPC setup and/or a

spatial light modulator, for shaping the input beam so as to achieve that a shaping profile in one or two dimensions (Sprofiie) is provided to at least a portion of the input beam (Binput) whose optical paths traverses the spatial light modulator, so as to suppress side-lobes of a point spread function (PSF) in the output region (Reoutput) in one or two or three dimensions,

- A processor operably connected to at least the spatial light modulator, such as to the spatial light modulator and to the means for shaping the input beam,

said apparatus being arranged for carrying out the method according to the first aspect.

The apparatus may further comprise a source of the input beam, such as any one of an incandescent lamp or a LASER.

In an embodiment, there is provided apparatus comprising at least one lens arranged so that the shaped and modulated input beam (smBinput) traverses the lens.

In an embodiment, there is provided apparatus arranged so that the shaped and modulated input beam (smBinput) traverses no lenses, such as wherein the diffraction is Fresnei diffraction. An advantage of this embodiment may be, that it is simple since it renders lenses superfluous.

According to a third aspect of the invention, there is provided use of the method according to the first aspect and/or an apparatus according to the second aspect for any one of: - a holographic displaying,

- stimulation of one or more biological entities, such as stimulation of one or more neurons,

- photopolymerization, such as two-photon photopolymerization, - forming the output intensity pattern (Ioutput(x,y,z)) as a contiguous pattern,

- laser material processing, such as one shot material processing,

- photolithography,

- structured illumination microscopy.

It is noted that any combination of two or more embodiments is conceived and encompassed by the invention. The first, second and third aspect of the present invention may each be combined with any of the other aspects. These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

BRIEF DESCRIPTION OF THE FIGURES

The method, apparatus and use according to the invention will now be described in more detail with regard to the accompanying figures. The figures show one way of implementing the present invention and is not to be construed as being limiting to other possible embodiments falling within the scope of the attached claim set.

Figure 1 shows an exemplary apparatus according to an embodiment of the invention,

Figure 2 shows an exemplary apparatus,

Figure 3 shows another exemplary apparatus, Figure 4 shows an exemplary apparatus according to another embodiment of the invention,

Figure 5 shows an exemplary apparatus according to another embodiment of the invention,

Figure 6 is a flow-chart of a method according to the invention.

DETAILED DESCRIPTION OF AN EMBODIMENT

Figure 1 shows an exemplary apparatus 100 according to an embodiment of the invention. More particularly, figure 1 shows apparatus 100 for receiving an input intensity pattern (Iin_Put(x,y,z)), which in the present figure is indicated by a dotted line representing a pattern which a user desires in the output region, and for receiving an input beam (Binput), which in the present embodiment is a plane wave of electromagnetic radiation moving from left to right as indicated by the arrows, and for providing an output intensity pattern (Ioutput(x,y,z)), which in the present figure is indicated by the sum of the point-spread functions (PSF) in the output region which are shown as (seven) rectangular blocks where the illustrated length in the z-direction illustrates their individual intensity as a function of extent in the y-direction, , such as a contiguous output intensity pattern (Ioutput(x,y,z)), in an output region (Reoutput), where the output region in the present figure is an image plane as indicated by the dashed line, in response thereto, said apparatus comprising :

- A spatial light modulator (SLM), which in the present figure is a

phase only (PO-)SLM, and which in the present figure has aperture width D which is the same in both directions,

- Means, which in the present figure is a GPC setup (GPC), for shaping the input beam so as to achieve that a shaping profile, which in the present embodiment is a SINC shape as indicated by the shaped input beam (sBmput), i.e., a shape in both phase and scalar amplitude as provided by the GPC setup, in one or two dimensions (Sprofiie) is provided to at least a portion of the input beam (Binput) whose optical paths traverses the spatial light modulator, so as to suppress side-lobes of a point spread function (PSF) in the output region (Reoutput) in one or two or three dimensions, where it is noted that the present embodiment relies on shaping a modulation in two dimensions, i.e., in the xy-plane (where the plane of the paper is the zy-plane, and the x-axis is orthogonal to the paper in a direction into the paper) and where the output intensity pattern is provided as a diffraction pattern (DF) in two dimension in the output region which is an image plane, - A processor (not shown) operably connected to at least the spatial light modulator, such as to the spatial light modulator and to the means for shaping the input beam, and the processor being arranged for enabling receiving the input beam (Bmput) and providing a shaped and modulated input beam (smBinput, note that the profile shown in the figure is merely for illustrative purposes and does not necessarily bear any resemblance to a real life profile at the given position), by

i. shaping the input beam so as to achieve that a shaping

profile in one or two dimensions (Sprofiie) is provided to at least a portion of the input beam (Bmput), so as to provide the SINC shape of the present embodiment as indicated by the shaped input beam (sBinput) where the dashed line through the SINC is drawn as a guide to the eye so as to clearly indicate that the SINC profile is complex and comprises different portions with opposite phase, whose optical paths traverses the spatial light modulator, so as to suppress side- lobes of a point spread function (PSF) in the output region (Reoutput) in one or two or three dimensions, and

ii. modulating the input beam (Bmput), which in the present

figure corresponds to modulating the shaped input beam (sBinput), with the modulation pattern (Pa_m) at the spatial light modulator (SLM),

and the processor further being arranged for enabling :

iii. tiling the modulation pattern (Pa_m) so that a spacing (Δ) of a sampling lattice in the output region (Reoutput) substantially corresponds, such as corresponds to, such as being equal to, a width (w) of the point spread function (PSF) in the output region (Reoutput), where the point spread function as shown in the output region in the present figure substantially

corresponds to a rectangular function, such as top-hat function, due to the previous SINC shaping of the input beam, so as to enable providing with the shaped and modulated input beam (smBinput) the output intensity pattern (I_output(x,y,z)) in the output region (Reoutput) as a diffraction pattern (DF) of the modulation pattern (Pa_m). It may be understood that diffraction pattern (DF) and output pattern (Ioutput(x,y,z)) are similar. It may furthermore be noted that the figure shows providing a diffraction pattern as a Fraunhofer diffraction pattern, where a Fourier lens (FL) is placed a focal distance (f) away from both the SLM and the image plane.

Figure 2 shows an exemplary apparatus 200, which appears similar to the apparatus shown in FIG 1, but which lacks the GPC setup, i.e., the apparatus is not enabling shaping the input beam so as to reduce side lobes of the point-spred functions (PSF2) in the output region. As can be seen in the figure, the diffraction pattern DF2 is based on the modulated input beam (mBinput), but although the main lobe of the point-spred functions (PSF2) in the output region is quite narrow, there are side lobes of the point-spred functions (PSF2) which overlap with side lobes of adjacent point-spred functions (PSF2), and since the phase between the individual point-spread functions (PSF2) which effectively corresponds to pixels, cannot be controlled, this overlap inevitably leads to significant speckle (Sp) between the centres of the point spread functions (PSF2) . Furthermore, although the intensity value at the centre positions of the point-spread functions (PSF2) may match a level of the input intensity pattern, such as a contiguous input intensity pattern, there would be "gaps" in intensity between the point-spred functions (PSF2) due to their non-rectangular shape (also even without the occurrence of speckle).

Figure 3 shows another exemplary apparatus 300, which appears similar to the apparatus shown in FIG 1, but where the modulation pattern (Pa3m) is not tiled on the SLM, i.e., the spacing (Δ3) of the sample pattern in the sample region is not brought to correspond with the width (w) of the PSF. As can be seen in the figure, the diffraction pattern DF3 is based on the thus shaped and modulated input beam (smB3in_Put), but although the individual point-spred functions (PSF3) in the output region is similar to the point-spred functions (PSF) of FIG 1, the intensity output pattern (I3output) will suffer from defects and significant speckle, due to significant overlap between the individual PSF functions, since the spacing (Δ3) of the sample pattern in the sample region is not brought to correspond with the width (w) of the point-spred functions (PSF3), but is in fact smaller, and therefore will main lobes of the neighbouring point-spred functions (PSF3) overlap, and since the phase between the individual point-spred functions (PSF3) which effectively corresponds to pixels, cannot be controlled, this overlap inevitably leads to significant speckle.

Figure 4 shows an exemplary apparatus 400 according to another embodiment of the invention, where the GPC setup is partically replaced with a scalar amplitude filter (SAF), such as a transmittance mask. This mask is not capable of changing the phase (note the dashed line through the subsequent profile is drawn as a guide to the eye so as to clearly indicate that this "numerical SINC" profile comprises a single phase only), and hence no SINC can be made this way. As an alternative to the GPC setup in figure 1, the scalar amplitude filter (SAF) shapes the input beam (Bmput), into a partially shaped input beam (sB4i_nput) which has a partial shaping profile corresponding to a SINC where all negative values have been multiplied by minus one. In order to finish the shaping into a SINC, the spatial light modulator - in addition to the modulation pattern of FIG 1 which is modulating the input beam - also is responsible for part of the shaping, namely the phase-shaping, corresponding to shifting the phase of every second lobe of in the SINC function via a pattern (Pa4_m) applied at the SLM. As such, the apparatus 400 is an example of an apparatus where the shaping takes place in multiple steps, and partially overlaps with the modulation.

Figure 5 shows another exemplary apparatus 500 according to another

embodiment of the invention, which is similar to the apparatus 100 in FIG. 1, but which is arranged so that no lenses are necessary, and where a distance d5 between the SLM and the output region is chosen appropriately. An advantage of this is that it dispenses with the need for lenses.

Figure 6 is a flow-chart of a method according to the invention. More specifically, Fig. 6 shows a method (M) for providing an output intensity pattern (Ioutput(x,y,z)), such as a contiguous output intensity pattern (Ioutput(x,y,z)), in an output region (Reoutput), the method comprising :

- Receiving (SO) an input intensity pattern (Iin_Put(x,y,z)),

- Receiving (SI) an input beam ( Bmput) of electromagnetic radiation,

- providing (S2) a spatial light modulator (SLM),

- generating (S3) a modulation pattern (Pa_m) at the spatial light

modulator (SLM), so that a diffraction pattern (DF) of the modulation pattern (Pa_m) corresponds to the input intensity pattern (Iin_Put(x,y,z)),

- encoding (S4) the input beam (Bmput) by

i. shaping (S5) the input beam so as to achieve that a shaping profile in one or two dimensions (Sprofiie) is provided to at least a portion of the input beam (Bmput) whose optical paths traverses the spatial light modulator, so as to suppress side- lobes of a point spread function (PSF) in the output region (Reoutput) in one or two or three dimensions,

ii. modulating (S6) the input beam (Bmput), with the modulation pattern (Pa_m) at the spatial light modulator (SLM), so as to provide a shaped and modulated input beam (smBmput),

- providing (S7) with the shaped and modulated input beam (smBinput) the output intensity pattern (Ioutput(x,y,z)) in the output region (Reoutput) as a diffraction pattern (DF) of the modulation pattern (Pa_m),

wherein the method further comprises

- tiling (S8) the modulation pattern so that a spacing (Δ) of a sampling lattice in the output region (Reoutput) substantially corresponds to, such as corresponds to, such as being equal to, a width (w) of a main lobe of the point spread function (PSF) in the output region (Reoutput).

It may be understood that encoding (S4) and tiling (S8) takes place temporally before providing (S7) the output pattern. The steps are not necessarily arranged in the order in which they occur.

To sum up, there is presented, a method for providing an intensity pattern, such as an image, more particularly a contiguous intensity pattern with reduced speckle. The method comprises illuminating a spatial light modulator with a modulation pattern so as to form the intensity pattern as a diffraction pattern, where the method furthermore comprises shaping the input beam so that the point spread function in the output region where the diffraction pattern is formed has suppressed side lobes, such as the point spread function being substantially rectangular in shape, and wherein the method furthermore comprises tiling the modulation pattern so that the spacing between the individual point spread function corresponds to their widths. An effect of this may be that the output pattern is formed as a pattern of closely spaced point spread functions, which enables forming a contiguous pattern with reduced speckle.

In the following there is presented embodiments E1-E15:

El. A method (M) for providing an output intensity pattern (Ioutput(x,y,z)), such as a contiguous output intensity pattern (Ioutput(x,y,z)), in an output region (Reoutput), the method comprising :

- Receiving (SO) an input intensity pattern (Iin_Put(x,y,z)),

- Receiving (SI) an input beam (Bmput) of electromagnetic radiation,

- providing (S2) a spatial light modulator (SLM),

- generating (S3) a modulation pattern (Pa_m) at the spatial light modulator (SLM), so that a diffraction pattern (DF) of the

modulation pattern (Pa_m) corresponds to the input intensity pattern (Iin_Put(x,y,z)),

- encoding (S4) the input beam (Bmput) by

ii. modulating (S6) the input beam (Bmput), with the modulation pattern (Pam) at the spatial light modulator (SLM), so as to provide a shaped and modulated input beam (smBmput),

wherein the method further comprises

- tiling (S8) the modulation pattern (Pa_m) so that a spacing (Δ) of a sampling lattice in the output region (Reoutput) substantially corresponds to, such as corresponds to, such as being equal to, a width (w) of a main lobe of the point spread function (PSF) in the output region (Reoutput).

E2.A method according to any one of the preceding embodiments, wherein one or more composants of the shaping profile (Sprofiie) are complex valued.

E3.A method according to any one of the preceding embodiments, wherein different regions within the shaping profile have substantially opposite phase, such as opposite phase.

E4.A method according to any one of the preceding embodiments, wherein the shape of the shaping profile (Sprofiie) leads to a point spread function in the output region (Reoutput) where the main lobe of the point spread function (PSF) is more rectangular in shape than a main lobe of a SINC function, such as the main lobe of the point spread function having a top-hat-like shape.

E5.A method according to any one of the preceding embodiments, wherein the shaping (Sprofiie) profile may be described mathematically by a SINC function.

E6.A method according to embodiment E5, wherein

- a ratio Ro of the aperture width D of the SLM in at least one

direction, such as two directions, with respect to the width Asinc of the sine mainlobe across the spatial light modulator in at least said one direction, such as two directions, such as Ro being at least 1, such as Ro, being larger than 1, such as Ro being at least 2, such as Ro being larger than 2, such as Ro being at least 2, 3, 4, 5, 6, 7, 8, 9 or 10, 50 or 100, and

- a number of tilings (Nt) where the number of tilings (Nt) is greater than unity (Nt > 1), such as the number of tilings (Nt) being at least

2 (Nt > 2), such as the number of tilings (Nt) being an integer which is at least 2 (Nt > 2), of the modulation pattern in the given direction

are substantially related by, such as related by: 2Ro ~ Nt

such as substantially related by, such as related by:

2Ro = Nt. E7.A method according to any one of the preceding embodiments, wherein shaping the input beam is carried out so that a further shaping profile is provided to the input beam so as to suppress ripple of the point spread function (PSF) in the output region (Reoutput), such as said further shaping profile being a window function, such as any one of Bartlett, Blackman, Connes, Cosine, Gaussian, Hamming, Hanning, Butterworth.

E8.A method according to any one of the preceding embodiments, wherein shaping the input beam comprises applying one or more of:

- a profile of polarization,

- a profile of phase.

E9.A method according to any one of the preceding embodiments, wherein modulating the input beam (Bmput) comprises applying the modulation pattern (Pa_m), where the modulation pattern (Pa_m) is given as one or more of:

- a pattern of scalar amplitudes,

- a pattern of polarization,

- a pattern of phase.

E10. A method according to any one of the preceding embodiments,

wherein the shaping profile comprises:

- a profile of scalar amplitude and a profile of phase,

and wherein the modulation pattern (Pa_m) comprises:

- a pattern of phase. Ell. A method according to any one of the preceding embodiments, wherein the shaping profile and the modulation pattern (Pa_m) comprises, respectively,

- a profile of scalar amplitude and a pattern of scalar amplitude,

and/or

- a profile of scalar amplitude and a pattern of phase, and/or

- a profile of scalar amplitude and a pattern of polarization, and/or

- a profile of phase and a pattern of scalar amplitude, and/or

- a profile of phase and a pattern of phase, and/or

- a profile of phase and a pattern of polarization, and/or

- a profile of polarization and a pattern of scalar amplitude, and/or

- a profile of polarization and a pattern of phase, and/or

- a profile of polarization and a pattern of polarization. E12. A method according to any of the preceding embodiments, wherein the diffraction is any one of:

Fraunhofer diffraction, such as Fraunhofer diffraction with lenses or Fraunhofer diffraction without lenses, and

Fresnel diffraction, such as Fresnel diffraction with lenses or Fresnel diffraction without lenses.

E13. A method according to any of the preceding embodiments, wherein the method is further comprising :

- Providing a lens (L), said lens having a focal length (fiens),

Placing said lens in an optical path between

and wherein the step of - providing (S7) with the shaped and modulated input beam

(smBinput) the output intensity pattern (Ioutput(x,y,z)) in the output region (Reoutput) as a diffraction pattern (DF) of the modulation pattern (Pa_m),

comprises

- focusing the shaped and modulated input beam (smBinput) on the output region (Reoutput) with the lens (L). . An apparatus for receiving an input intensity pattern (Iin_Put(x,y,z)) and for receiving an input beam (Bmput) and for providing an output intensity pattern (I_output(x,y,z)), such as a contiguous output intensity pattern (Ioutput(x,y,z)), in an output region (Reoutput) in response thereto, said apparatus comprising :

- A spatial light modulator (SLM),

- Means, such as a fixed modulation mask, a GPC setup and/or a

spatial light modulator, for shaping the input beam so as to achieve that a shaping profile in one or two dimensions (Sprofiie) is provided to at least a portion of the input beam (Bmput) whose optical paths traverses the spatial light modulator, so as to suppress side-lobes of a point spread function (PSF) in the output region (Reoutput) in one or two or three dimensions,

- A processor operably connected to at least the spatial light

modulator, such as to the spatial light modulator and to the means for shaping the input beam, and the processor being arranged for enabling receiving the input beam (Bmput) and providing a shaped and modulated input beam (smBinput) by

i. shaping the input beam so as to achieve that a shaping

profile in one or two dimensions (Sprofiie) is provided to at least a portion of the input beam (Bmput) whose optical paths traverses the spatial light modulator, so as to suppress side- lobes of a point spread function (PSF) in the output region (Reoutput) in one or two or three dimensions, and ii. modulating the input beam (Bmput), with the modulation

pattern (Pam) at the spatial light modulator (SLM),

and the processor further being arranged for enabling : iii. tiling the modulation pattern (Pa_m) so that a spacing (Δ) of a sampling lattice in the output region (Reoutput) substantially corresponds to, such as corresponds to, such as being equal to, a width (w) of the point spread function (PSF) in the output region (Reoutput),

so as to enable providing with the shaped and modulated input beam (smBmput) the output intensity pattern (Ioutput(x,y,z)) in the output region (Reoutput) as a diffraction pattern (DF) of the modulation pattern (Pa_m).

E15. Use of the method according to any one of embodiments E1-E13 and/or an apparatus according to embodiment E14 for any one of:

- holographic displaying,

- photopolymerization, such as two-photon photopolymerization,

- forming the output intensity pattern (I_output(x,y,z)) as a contiguous pattern,

- laser material processing, such as one shot material processing, - photolithography,

- structured illumination microscopy.

For the above embodiments E1-E15, it may be understood that reference to preceding 'embodiments' may refer to preceding embodiments within

embodiments E1-E15.

Although the present invention has been described in connection with the specified embodiments, it should not be construed as being in any way limited to the presented examples. The scope of the present invention is set out by the accompanying claim set. In the context of the claims, the terms "comprising" or "comprises" do not exclude other possible elements or steps. Also, the mentioning of references such as "a" or "an" etc. should not be construed as excluding a plurality. The use of reference signs in the claims with respect to elements indicated in the figures shall also not be construed as limiting the scope of the invention. Furthermore, individual features mentioned in different claims, may possibly be advantageously combined, and the mentioning of these features in different claims does not exclude that a combination of features is not possible and advantageous.

Claims

A method (M) for providing an output intensity pattern (Ioutput(x,y,z)) in an output region (Reoutput), the method comprising :

- Receiving (SO) input intensity pattern (Iin_Put(x,y,z)) data,

- Receiving (SI) an input beam (Bmput) of electromagnetic radiation,

- providing

(S2) a spatial light modulator (SLM),

- generating

(S3) a modulation motif and tiling it to form a modulation pattern (Pa_m) encoded at the spatial light modulator (SLM), so that a diffraction pattern (DF) of the modulation pattern (Pa_m)

corresponds to the input intensity pattern (Iin_Put(x,y,z)),

- shaping and modulating

(S4) the input beam (Bmput) by

i. shaping

(S5) the input beam so as to achieve that a shaping profile in one or two dimensions (Sprofiie) is provided to at least a portion of the input beam (Bmput) whose optical paths traverses the spatial light modulator, wherein the shaping (Sprofiie) profile may be described mathematically by a SINC function or a JINC function,

ii. modulating

(S6) the input beam (Bmput), with the modulation pattern (Pam) at the spatial light modulator (SLM),

so as to provide a shaped and modulated input beam (smBmput),

- providing

(S7) with the shaped and modulated input beam (smBinput) the output intensity pattern (Ioutput(x,y,z)) in the output region (Reoutput) as a diffraction pattern (DF) of the modulation pattern (Pam),

wherein said tiling comprises

- tiling (S8) the modulation motif to form the modulation pattern

(Pa_m), such as tiling (S8) the modulation motif in one or two dimensions to form the modulation pattern (Pa_m), so that

i. the width Asinc of the SINC or JINC mainlobe of the shaping function, where said width Asinc of the SINC or JINC mainlobe is understood to be the width between the first two zero- crossings, across the spatial light modulator in at least said one direction, such as two directions, ii. the width Dmotif of the modulation motif in the corresponding direction or directions,

are substantially related by, such as related by:

Asinc ~ 2Dmotif

such as substantially related by, such as related by:

Asinc = 2D motif.

A method according to any one of the preceding claims, wherein one or more composants of the shaping profile (Sprofiie) are complex valued.

A method according to any one of the preceding claims, wherein different regions within the shaping profile have substantially opposite phase, such as opposite phase. 4. A method according to any one of the preceding claims, wherein the shape of the shaping profile (Sprofiie) leads to a point spread function in the output region (Reoutput) where a slope of a main lobe of the point spread function at half of the maximum of the main lobe is steeper than a slope at half of the maximum of a corresponding SINC function with similar maximum and similar full width at half maximum.

A method according to any one of the preceding claims, wherein shaping the input beam is carried out so that a further shaping profile is provided to the input beam so as to suppress ripple of the point spread function (PSF) in the output region (Reoutput), such as said further shaping profile being a window function.

A method according to any one of the preceding claims, wherein shaping the input beam comprises applying one or more of:

- a profile of polarization,

- a profile of phase. A method according to any one of the preceding claims, wherein

modulating the input beam (Bmput) comprises applying the modulation pattern (Pa_m), where the modulation pattern (Pa_m) is given as one or more of:

- a pattern of scalar amplitudes,

- a pattern of polarization,

- a pattern of phase.

8. A method according to any one of the preceding claims, wherein the

shaping profile comprises:

- a profile of scalar amplitude and a profile of phase,

and wherein the modulation pattern (Pa_m) comprises:

- a pattern of phase.

A method according to any one of the preceding claims, wherein the shaping profile and the modulation pattern (Pa_m) comprises, respectively,

- a profile of scalar amplitude and a pattern of scalar amplitude, or

- a profile of scalar amplitude and a pattern of phase, or

- a profile of scalar amplitude and a pattern of polarization, or

- a profile of phase and a pattern of scalar amplitude, or

- a profile of phase and a pattern of phase, or

- a profile of phase and a pattern of polarization, or

- a profile of polarization and a pattern of scalar amplitude, or

- a profile of polarization and a pattern of phase, or

- a profile of polarization and a pattern of polarization.

10. A method according to any of the preceding claims, wherein the method is further comprising :

- Providing a lens (L), said lens having a focal length (fiens),

Placing said lens in an optical path between

i. the spatial light modulator (SLM), where a distance between the spatial light modulator and the lens substantially corresponds to the focal length (fiens), such as corresponds to the focal length (fiens), and ii. the output region (Reoutput), where a distance between the output region (Reoutput) and the lens substantially corresponds to the focal length (fiens), such as corresponds to the focal length (fiens),

and wherein the step of

- providing (S7) with the shaped and modulated input beam

(smBinput) the output intensity pattern (I_output(x,y,z)) in the output region (Reoutput) as a diffraction pattern (DF) of the modulation pattern (Pa_m),

comprises

11. An apparatus for receiving an input intensity pattern (Iin_Put(x,y,z)) and for receiving an input beam (Bmput) and for providing an output intensity pattern (Ioutput(x,y,z)) in an output region (Reoutput) in response thereto, said apparatus comprising :

- A spatial light modulator (SLM), such as a spatial light modulator for modulating the input beam (Bmput),

- Means, such as a fixed modulation mask, a GPC setup and/or a

spatial light modulator, for shaping the input beam so as to achieve that a shaping profile in one or two dimensions (Sprofiie) is provided to at least a portion of the input beam (Bmput) whose optical paths traverses the spatial light modulator,

- A processor operably connected to at least the spatial light

modulator, such as to the spatial light modulator and to the means for shaping the input beam,

said apparatus being arranged for carrying out the method according to any one of claims 1-10.

12. Use of the method according to any one of claims 1-10 and/or an

apparatus according to claim 11 for any one of:

- holographic displaying,

- stimulation of one or more biological entities, such as stimulation of one or more neurons, - photopolymerization, such as two-photon photopolymerization,

- forming the output intensity pattern (Ioutput(x,y,z)) as a contiguous pattern,

- structured illumination microscopy.