FIELD OF THE INVENTION

The invention relates to a method of displaying - with a pixelated luminaire - an output image, as well as to a system including such pixelated luminaire. The invention also relates to a computer program product (configured to execute such method). Yet further, the invention relates to a specific use of the pixelated luminaire.

BACKGROUND OF THE INVENTION

Large display panels are known in the art. US20150172594A1, for instance, describes a digital signage system in which a display is arranged in a station or an airport, on a wall surface of a building, outside the front of a store in a shopping area, or the like, so as to display advertising contents on the display has been known. In such a digital signage system, advertising contents from a content server are transmitted to the display via a network, and the advertising contents can be changed over according to a schedule and displayed.

Accordingly, various video advertisements can be offered. Moreover, as the display to be used in the digital signage system, a display having a multi-display configuration in which a plurality of displays are two-dimensionally arranged in a matrix, and video pictures are displayed by using these displays as one large display can be used.

US2017/018215A discloses a lighting device that has a matrix display, a display driver, a controllable optic array, an optic driver, a memory with a programming, and a processor. The display driver is coupled to the matrix display, and in response to a first control input drives the matrix to generate light representing the image. The controllable optic array is coupled to the matrix display to optically process the image light output from the display to shape and/or redirect image light from the display. The optic driver is coupled to the controllable optic array, responsive to a second control input, to drive a state of each pixel of the controllable optic array. The processor has access to the memory and is coupled to the drivers to supply the first and second control inputs to the drivers. The programming in the memory, when executed by the processor configures the lighting device to perform functions, such as accessing an image selection and a general lighting distribution selection. Based on the image selection, via the matrix display visible through the controllable optical array, an image output is presented. Light also is emitted that has the selected general lighting distribution from at least a portion of the optic array for general illumination.

US2011/234644A discloses a display device with a display unit and a controller for generating and transmitting a scan signal and an image data signal to a scan driver and a data driver, respectively. The controller includes a memory unit storing a look up table of basic correction amounts for a test image data signal according a comparison result of comparing a measured value of an image of the display unit displaying the test image data signal with a target value of the test image data signal, and a data controller storing data for a modulation coefficient for applying the look-up table to the supplied image data signal.

US2018/047325 A discloses a display apparatus with a display section and circuitry. The display section comprises a plurality of display units arranged in a two- dimensional array, wherein each of the display units comprises a plurality of pixels arranged in a matrix, and each of the plurality pixels comprises a plurality of light-emitting devices that are each configured to emit a different color of light. The circuity is configured to generate a corrected image signal based on an uncorrected image signal and correction factors that correct luminance and chromaticity of the light-emitting devices.

SUMMARY OF THE INVENTION

Maturing LED technology and with the introduction of micro LEDs, pixelated luminaire applications are getting closer. However, focus in these luminaires is on the content and not on the quality of light. As such luminaires may contribute to general lighting in e.g. office spaces or hospitality spaces, or even may substantially contribute to the general lighting, the use of such luminaires may also lead to disadvantages such as general lighting in such space having undesired optical properties.

Hence, it is an aspect of the invention to provide an alternative luminaire or luminaire comprising system and/or method of controlling such luminaire, which preferably further at least partly obviates one or more of above-described drawbacks. The present invention may have as object to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative.

Amongst others, it is - in embodiments - herein suggested to use a program which analyses the integral light coming out of the luminaire and which determines one or more of its color point (CP), correlated color temperature (CCT), and color rendering index (CRI). Subsequently, it may analyze the image content and e.g. adjust the background of the image or color levels of the colored pixels in order to obtain the desired CCT on the black body line (BBL) and/or CRI above 70, such as above 80, or even higher, while essentially maintaining the integrity and the quality of the image. In embodiments, the spectral distribution and luminous flux of each individual pixel may be calculated and relatively adapted.

In a first aspect, the invention provides a method of displaying with a pixelated luminaire (“luminaire”) an output image based on an source image, wherein the pixelated luminaire comprises a total number of pixels, each configured to generate pixel light having a controllable color and/or intensity, wherein the pixelated luminaire is configured to generate luminaire light by displaying the output image with the pixelated luminaire, wherein the luminaire light during display of the output image has one or more luminaire light optical properties selected from the group consisting of color point, color temperature and color rendering index, wherein the method comprises comparing a value of the luminaire light optical properties of the luminaire light generated or to be generated during display of the output image with one or more values of predetermined target optical properties, and wherein, if one or more values of the luminaire light optical properties of the luminaire light generated or to be generated do not comply with one or more values of the one or more predetermined target optical properties, the method further comprises at least temporarily modifying in a modification stage one or more of color and intensity of the pixel light generated or to be generated of at least a subset of the total number of pixels, in order to generate the luminaire light during display of the output image with one or more of the one or more luminaire light optical properties having a value complying with one or more values of the one or more predetermined target optical properties or having a value closer to the value of the one or more of the one or more predetermined target optical properties than when not applying the modification stage.

With such method, it is possible to modify the image that is (to be) displayed, while essentially maintaining the image quality and/or integrity, but wherein the light that emanates from the display is more suitable as source of general lighting. Hence, the source image is still recognizable, while the colors and/or intensity of a number of the pixels may be modified relative to a unmodified display of the source image, thereby displaying the output image (or modified source image) which leads to the generation of light that may have an improved CRI, color point, or correlated color temperature (CCT) compared to a display of the output image wherein an unmodified source image is applied. Herein, the source image is especially a colored source image, such as including one or more of blue content, green content, yellow content and red content, especially at least blue content, green content and red content, or at least blue content and yellow content, or blue content, yellow content and red content. Especially, the source image may at least comprise blue content, green content and red content (and corresponding light may be generated when displaying the (unmodified) source image). However, during operation of the pixelated luminaire, black-white images may also be generated. Also the corresponding white light thereof may be modified.

Especially, however, the invention is herein further described in relation to the generation, and where necessary modification, of colored images. The luminaire light comprises the combined pixel light of the total number of pixels.

Basically, there are two (series of) embodiments. In first embodiments, the light of the displayed output image, i.e. the luminaire light during display of the output image, is analyzed, and based thereon, the output image is modified (i.e. a modified source image is displayed), which output image then, based on the feedback loop, leads to the generation of luminaire light, while displaying this output image, with better optical properties.

Of course, also a feed forward method may be applied. The output image that will be generated based on the source image can of course - in second embodiments - be predicted, and thereby also the optical properties of the luminaire light that is generated would the source image displayed (generation of the output image or display of the output image). Based thereon, the source image that is used for the output image may be modified, i.e. a modified source image, such that when the output image (based on the modified source image) is displayed, the thereby generated luminaire light has (already) better optical properties.

Of course, feedforward embodiments may be combined, for instance for control purposes, with feedback embodiments.

Hence, in embodiments the method may comprise providing a source image providing initial image optical properties for an output image comprising initial pixel optical properties of a plurality of pixels, a conformation stage comprising conforming the optical properties of the output image to predetermined target optical properties by controlling the pixel optical properties of the plurality of pixels, displaying the output image. The conformation stage may be executed conformation during display of the initial image, whereby during display thereof the initial image (gradually) changes to the output image, or the conformation stage may be executed before display of the initial image, such that immediately the output image leading to (more) desirable optical properties of the luminaire light is displayed. Therefore, herein the phrase“generated or to be generated” is used, especially to indicate the feedback or feed forward embodiments.

As indicated above, the invention provides a method of displaying with a pixelated luminaire an output image based on a source image.

The term“pixelated luminaire” especially refers to a luminaire comprising a plurality of solid state light sources. Groups of solid state light sources may be able to provide color tunable light. Such groups are herein indicated as pixels. The luminaire is especially a 2D array of such pixels, which may include arrays of hundreds or thousands, or even more of pixels (comprising solid state light sources). The luminaire is especially configured as display.

The luminaire may comprise pixels (including (solid state) light sources) in x columns and y rows (2D array). In embodiments, x is at least 50 and y is at least 50.

Especially, in embodiments x is at least 80 and y is at least 80. Even more especially, x is at least 100 and y is at least 100. In embodiments, 0.5<x/y<2.

The term“luminaire” may also refer to a plurality of functionally coupled luminaire. Hence, an array of functionally coupled luminaires may also be considered a luminaire. In this way large displays may be created, of several, or even tens or more of square meters.

In embodiments, the pixelated luminaire has a display area of at least 1 m ² , such as at least 2 m ² , like at least 4 m ² , such as in the range of 2-1000 m ² , like 4-250 m ² . The pixel size will in general be equal to or smaller than about 4 cm ² , such as equal to or smaller than 1 cm ² , like in the range of 0.5 mm ² - 1 cm ² .

The term“solid state light source” may refer to a semiconductor light-emitting device, such as a light emitting diode (LEDs), a resonant cavity light emitting diode

(RCLED), a vertical cavity laser diode (VCSELs), an edge emitting laser, etc.. The term “light source” may also refer to an organic light-emitting diode, such as a passive-matrix (PMOLED) or an active-matrix (AMOLED). In a specific embodiment, the light source comprises a solid state light source (such as a LED or laser diode). In an embodiment, the light source comprises a LED (light emitting diode). The term LED may also refer to a plurality of LEDs. Further, the term“light source” may in embodiments also refer to a so- called chips-on-board (COB) light source. The term“COB” especially refers to LED chips in the form of a semiconductor chip that is neither encased nor connected but directly mounted onto a substrate, such as a PCB. Hence, a plurality of semiconductor light sources may be configured on the same substrate. In embodiments, a COB is a multi LED chip configured together as a single lighting module. The term“light source” may also relate to a plurality of light sources, such as 2-2000 solid state light sources.

In embodiments, the pixels of the pixelated luminaire are defined by micro LEDs. Micro LEDs are known in the art and may be defined as a light emitting diode having a die dimension equal to or smaller than 100 pm.

In embodiments, one or more (such as a subset of) solid state light source(s) may be supplied with a luminescent material, configured to convert at least part of the light of the die of the solid state light source(s). The light emanating from the solid state source(s), including luminescent material light, is herein indicated as“solid state light source light”.

The light sources, or combination of a plurality of light sources for defining a pixel, may comprise an optical element such as a diffuser, a total internal reflection (TIR) collimator, a reflector or a lens.

Hence, in embodiments each light source may comprise an RGB LED package i.e. a package with a red LED, blue LED and a green LED. It may also comprise an RGBA package (A= amber LED). It may also comprise an RGBW LED package (W = white LED).

Herein, the term“light source” may also refer to the combination of (solid state) light sources that define a single pixel (with intensity and color tunable pixel light).

All (LED) light sources may also share same optical element such as a diffuser. Hence, downstream of the solid state light source, optics and/or a window may be configured. The optics may include one or more of a lens, a diffusor, etc.. The optics, when available, may be configured upstream of the window or may be integrated in the window. The window may especially refer to a layer of light transmissive material, such as a polymeric material.

The terms“upstream” and“downstream” relate to an arrangement of items or features relative to the propagation of the light from a light generating means (here the especially the light source), wherein relative to a first position within a beam of light from the light generating means, a second position in the beam of light closer to the light generating means is“upstream”, and a third position within the beam of light further away from the light generating means is“downstream”.

The phrase“output image based on a source image” may especially indicate that in principle all information of the source image is displayed in the output image. The herein described modification may be similar as to editing of photos in the sense that some parts may be sharpened and other parts may be less sharpened (blurred), glare may be increased or decreased for some parts, contrast may be adapted for some parts, colors may be adapted for some parts, filers may be used, e.g. from color to black and white (or in between), etc.. Hence, information (“content”) may essentially not be lost or only to an acceptable extend.

Image quality attributes may e.g. be quantified based on using panels. Since visual perception can be affected by environmental and viewing conditions, the International Telecommunications Union produced a set of recommendations for standardized testing methods for subjective image quality assessment, i.e. P.910 : Subjective video quality assessment methods for multimedia applications. International Telecommunication Union. 6 April 2008, ITU-T, Telecommunication Standardization Sector of ITU, series P: Telephone Transmission Quality, Telephone Installations, Local Line Networks, Audiovisual quality in multimedia services, which is herein incorporated by reference.

Especially the degradation category rating DCR may be applied (which method is herein incorporated by reference) for assessing image reproduction quality. The degradation category rating implies that the test sequences are presented in pairs: the first stimulus presented in each pair is always the source reference, while the second stimulus is the same source presented through one of the systems under test (this method is also called the double stimulus impairment scale method). When reduced picture formats are used (e.g., CIF, QCIF, SIF), it could be useful to display the reference and the test sequence

simultaneously on the same monitor. Guidelines on this presentation procedure are discussed in Annex C of ITU-T P.910 (which annex is thus also incorporated by reference). The time pattern for the stimulus presentation can be illustrated by Fig. 1 (Fig. 2 of the ITU-T P.910). If a constant voting time is used (e.g., several viewers run simultaneously from a tape), then the voting time should be less than or equal to 10 s. The presentation time may be reduced or increased according to the content of the test material. In this case, the subjects are asked to rate the impairment of the second stimulus in relation to the reference. The following five- level scale for rating the impairment should be used:

5 Imperceptible

4 Perceptible but not annoying

3 Slightly annoying

2 Annoying

1 Very annoying The necessary number of replications is obtained for the DCR method by repeating the same test conditions at different points of time in the test.

For the present invention, the comparison - if desired - may be done between the source image as displayed with the pixelated luminaire without executing the herein described modification stage and the output image which is a display of the source image but after the modification stage. When the impairment is considered slightly annoying or better (perceptible but not annoying or imperceptible), i.e. 3 or higher on a scale of 5 or 5 (“fair”) or higher on a scale of 0-10 (see also Annex B of ITU-T P.910), then herein the quality is considered to be maintained. Note that on a scale of 5, the number 5, or on a scale of 10, the number 10 is effectively the display of the source image (i.e. the source image is displayed with a quality of reproduction that is perfectly faithful to the original source image). Hence, a non-modified source image leads to an output image that is a reproduction that is perfectly faithful to the (original) source image.

The DCR of the output image relative to the source image may be determined by sequentially showing the source image (i.e. unmodified) and the output image based on the herein described modification. Alternatively, the images may be shown next to each other on the pixelated luminaire, for the purpose of a DCR evaluation.

Assessment of the DCR can be done via a panel of subjects. The possible number of subjects (“observers” or“panelists”) in a viewing test (as well as in usability tests on terminals or services) is from 4 to 40. Four is the absolute minimum for statistical reasons, while there is rarely any point in going beyond 40. The actual number in a specific test should really depend on the required validity and the need to generalize from a sample to a larger population. In general, at least 15 observers should participate in the experiment. They should not be directly involved in picture quality evaluation as part of their work and should not be experienced assessors. Nevertheless, in the early phases in the development of video communication systems and in pilot experiments carried out before a larger test, small groups of experts (4-8) or other critical subjects can provide indicative results. Prior to a session, the observers should usually be screened for normal visual acuity or corrected-to-normal acuity and for normal color vision. Concerning acuity, no errors on the 20/30 line of a standard eye chart [b-Snellen] should be made. The chart should be scaled for the test viewing distance and the acuity test performed at the same location where the video images will be viewed (i.e., lean the eye chart up against the monitor) and have the subjects seated. Concerning color, no more than 2 plates [b-Beck] should be missed out of 12. Before starting the experiment, a scenario of the intended application of the system under test should be given to the subjects. In addition, a description of the type of assessment, the opinion scale and the presentation of the stimuli is given in written form. The range and type of impairments should be presented in preliminary trials, which may contain video sequences other than those used in the actual tests. It must not be implied that the worst quality seen in the training set necessarily corresponds to the lowest subjective grade on the scale. Questions about procedure or about the meaning of the instructions should be answered with care to avoid bias and only before the start of the session.

When a plurality of different images are displayed, such as in the case of a move, one may - assuming the DCR has to be evaluated - evaluate the DCR for all images or for a subset of images. In average, the DCR should in embodiments be as indicated above, i.e. at least 3 on a scale of 1-5 or at least 5 on a scale of 0-10.

Hence, maintenance of quality may especially refer to a DCR should in of at least 3 on a scale of 1-5 or at least 5 on a scale of 0-10. Note however that such quality assessment may be used as (later) check on the quality. The modification in the modification, however, will in general be automated and follow predetermined rules, such as using algorithms (see below for example of such rules).

As indicated above, the pixelated luminaire comprises a total number of pixels. This total number can be very large, and can be hundreds of thousands, even millions, or even much more for very large luminaires (see also above).

Each pixel configured to generate pixel light having a controllable color and intensity. Hence, each pixel may include two or more, especially three or more solid state light sources having different colors, such as RGB (red, green, blue), or RGBA (red, green, blue, amber) or RGBW (red, green, blue, white). Any combination of RGB optionally with another color or white is herein indicated as RGB, such as an RGB pixel or RGB light source.

Such pixels are controllable, in the sense that the intensity can be controlled, at least between on and off, but especially in embodiments also to intermediate values, and in the sense that the color point can be controlled, as different colors can be admixed, especially in different ratios, such that a substantial range with the color diagram (within the spectrum locus) can be achieved, and white, as well as red (R), green (G), and blue (B) (and optionally other colors, see also above) may be generated by a pixel.

The terms“violet light” or“violet emission” especially relates to light having a wavelength in the range of about 380-440 nm. The terms“blue light” or“blue emission” especially relates to light having a wavelength in the range of about 440-495 nm (including some violet and cyan hues). The terms“green light” or“green emission” especially relate to light having a wavelength in the range of about 495-570 nm. The terms“yellow light” or “yellow emission” especially relate to light having a wavelength in the range of about 570- 590 nm. The terms“orange light” or“orange emission” especially relate to light having a wavelength in the range of about 590-620 nm. The terms“red light” or“red emission” especially relate to light having a wavelength in the range of about 620-780 nm. The term “pink light” or“pink emission” refers to light having a blue and a red component. The terms “visible”,“visible light” or“visible emission” refer to light having a wavelength in the range of about 380-780 nm.

The term“controlling” and similar terms especially refer at least to determining the behavior or supervising the running of an element. Hence, herein

“controlling” and similar terms may e.g. refer to imposing behavior to the element

(determining the behavior or supervising the running of an element), etc., such as e.g.

measuring, displaying, actuating, opening, shifting, changing temperature, etc.. Beyond that, the term“controlling” and similar terms may additionally include monitoring. Hence, the term“controlling” and similar terms may include imposing behavior on an element and also imposing behavior on an element and monitoring the element. The controlling of the element can be done with a control system, which may also be indicated as“controller”. The control system and the element may thus at least temporarily, or permanently, functionally be coupled. The element may comprise the control system. In embodiments, the control system and element may not be physically coupled. Control can be done via wired and/or wireless control. The term“control system” may also refer to a plurality of different control systems, which especially are functionally coupled, and of which e.g. one control system may be a master control system and one or more others may be slave control systems. A control system may comprise or may be functionally coupled to a user interface.

The image can only be shown by generating pixel light. Hence, by displaying the output image (or the source image), by definition luminaire light is created. The term “luminaire light” may refer to the total light output in the visible spectrum (380-780 nm) of the luminaire during displaying the output image. Hence, the pixelated luminaire is configured to generate luminaire light by displaying the output image with the pixelated luminaire. The pixel light generated by the luminaire defines the luminaire light.

For large luminaire, such as e.g. over 10 m ² , especially over 100 m ² , one may desire to consider segments of the luminaire that generate luminaire light per segment. For instance, the luminaire light may have completely different optical properties over large luminaires. This is not further discussed below. Below, the discussion relates to the luminaire light (which might - in embodiments - be related to a segment of the luminaire).

The luminaire light by definition has optical properties such as color point.

The luminaire light may also be white light or whitish light. Hence, the luminaire light may also have a correlated color temperature. Further, a color rendering index may be attributed to the luminaire light. Hence, the luminaire light - during display of the output image (or source image) has one or more luminaire light optical properties selected from the group consisting of color point, color temperature and color rendering index.

Would the output image when displayed have optical properties not complying with desired optical properties, the output image to be displayed may be modified in the modification stage. Hence, one may say that a modified source image is used as basis for the output image. Likewise, when a sensor perceives that the output image - during display thereof - leads to optical properties of the luminaire light not complying with desired optical properties, the output image may be modified. Hence, one may say that the source image is modified in the modification stage to provide an (improved or modified) output image.

Therefore, the method comprises in embodiments comparing the luminaire light optical properties of the luminaire light generated or to be generated during display of the output image with one or more predetermined target optical properties, and wherein, when one or more luminaire light optical properties of the luminaire light generated or to be generated do not comply with the one or more predetermined target optical properties, the method further comprises at least temporarily modifying in a modification stage one or more of color and intensity of the pixel light generated or to be generated of at least a subset of the total number of pixels. Hence, the modification stage may be applied before display of the output image, or may be applied during display of the output image, wherein in the latter embodiment during display of the output image the image is (gradually) modified to provide a (improved or modified) output image (during at least part of the remaining time the output image is displayed).

An image is displayed during a certain time. This may be seconds, or even minutes. However, this may also be fractions of a second, such as in the case of a movie. The time an image is displayed is herein also indicated as“cycle time”. When a modification is applied, this may be over the whole cycle time, or over the remaining cycle time when using a feedback method, or the over part of the (remaining) cycle time. Hence, method further comprises at least temporarily modifying in a modification stage one or more of color and intensity of the pixel light generated or to be generated. Therefore, in embodiments the method may comprise displaying the output image during a cycle time, wherein the method comprises applying the modification stage only during part of the cycle time.

Further, all pixel light may be modified. However, in embodiments only part of the pixel light may be modified, i.e. for a subset of the total number of pixels the modification has impact (on the respective pixel light) during the (part of the) period the output image is displayed.

For some output images, it may not be easy to reach predetermined target optical properties, for instance output images that are essentially green (though even in such instances solutions are provided (see below)). Further, it may not be possible to completely reach the predetermined target optical properties, but it may be possible to modify the output image generated or to be generated such that the optical properties are closer to one or more of the predetermined target optical properties. Therefore, in embodiments the luminaire light during display of the output image is generated with one or more of the one or more luminaire light optical properties having a value complying with one or more of the one or more predetermined target optical properties or having a value closer to the one or more of the one or more predetermined target optical properties then when not applying the modification stage.

As indicated above, the generated output image may be based on a modified source image, such that the output image during display thereof leads to luminaire light that has (more) desirable optical properties. Hence, in embodiments the modification stage comprises analyzing the source image and based on this analysis at least temporarily modifying in the modification stage one or more of color and intensity of the pixel light to be generated of at least a subset of the total number of pixels to generate the luminaire light during display of the (feed-forward modification based) output image.

Alternatively (or additionally, the generated output image may be modified during display of the output image, thereby modifying the luminaire light to luminaire light that has (more) desirable optical properties. Hence, in embodiments the method may further comprise using a sensor for analyzing the luminaire light optical properties of the luminaire light (during display of the output image) and based on this analysis at least temporarily modifying in the modification stage one or more of color and intensity of the pixel light to be generated of at least a subset of the total number of pixels to generate the luminaire light during display of the (feed-back modification based) output image. The term“sensor” may also refer to a plurality of different sensors. The sensor is especially an optical sensor. In specific embodiments, the sensor may be a camera. In the latter embodiment, feed-back modification may e.g. only address those wherein there is a (substantial) deviation from the one or more predetermined target optical properties.

A way to maintain the quality and/or integrity of the source image is to allow modification of background content, and not allow, or only allow to a small extend modification of foreground content. For instance, assuming a scene of people in a nature environment, the people may be part of foreground content whereas the nature environment may be background content. Maintenance of integrity and quality of the latter may be less relevant than of the former.

The method further comprises analyzing the source image on source image foreground content and source image background content, wherein the method further comprises only applying the modification stage on pixel light of one or more of the pixels used for displaying output image background content corresponding to source image background content. Yet further, however, in embodiments the method may further comprise applying the modification stage on the pixel light of one or more of the pixels used for displaying the output image foreground content corresponding to source image foreground content, while maintaining a quality of output image foreground content at least equal to or higher than of the output image background content of the output image when compared to source image foreground content and source image background content of the source image, respectively, when using a degradation category rating.

The term“background content” may also refer to a plurality of background contents, such as different parts of the image. The term“foreground content” may also refer to a plurality of foreground contents, such as different (other) parts of the image. Background content and foreground content may be recognized based on automatic image recognition. Optionally, in the case of a limited number of images, a user may define background and/or foreground content via a user interface. Foreground content may be at least 40%, such as 40- 90%, like 50-90%, such as up to 80% of the total content of the image; background content may be at least 10%, such as 10-50%, like 10-40%, such as up to 20% of the total content of the image.

Background content and foreground content may be identified with state of the art image recognition analysis. Especially when images are displayed in sequences, with overlapping information, background and foreground content maybe identified. For instance, the information of changes in a scene may be enough to determined background content and foreground content, because an image's regions of interest may be objects (humans, cars, text etc.) in its foreground, that may e.g. move relative to the background (content). Background content identification is a widely used approach for detecting moving objects in videos from e.g. static cameras. Methods for background content detection are known in the art, like e.g. MOG background subtraction, subspace learning background subtraction, statistical background subtraction, decomposition into low-rank plus additive matrices for

background/foreground Separation etc. etc. Background content and foreground content in static images (i.e. not in a movie), may be done with image recognition technologies, wherein e.g. automatically humans or animals, sharp parts (relative to less sharp parts), lens effects on the image, and/or central parts of the image (relative to peripheral parts), of an in image are defined as foreground content, and the remaining part of the image as background content.

Likewise, a way to keep the quality and/or integrity of the source image is to allow modification of peripheral content, and not allow, or only allow to a small extend modification of central content. For instance, assuming a scene of people in a nature environment, the people may in general be part of central content whereas the nature environment may be peripheral content. Maintenance of integrity and quality of the latter may be less relevant than of the former.

Therefore, alternatively ((or additionally) to the above embodiments in relation to background and foreground content), in embodiments the method may comprise analyzing the source image on source image center content and source image edge content, wherein the method further comprises only applying the modification stage on pixel light of one or more of the pixels used for displaying output image edge content corresponding to source image edge content. Yet further, in embodiments the method may further comprise applying the modification stage on the pixel light of one or more of the pixels used for displaying the output image center content corresponding to source image center content, while maintaining a quality of output image center content at least equal to or higher than of the output image edge content of the output image when compared to source image center content and source image edge content of the source image, respectively, when using a degradation category rating.

The term“edge content” may also refer to a plurality of edge contents, such as different parts, like shells, of the image. The term“center content” may also refer to a plurality of center contents, such as different (other) parts of the image. Edge content and center content may be recognized based on automatic image recognition. Optionally, in the case of a limited number of images, a user may define edge and/or center content via a user interface. Center content may be at least 40%, such as 40-90%, like 50-90%, such as up to 80% of the total content of the image; edge content may be at least 10%, such as 10-50%, like 10-40%, such as up to 20% of the total content of the image.

Center content and edge content may be identified with state of the art image recognition analysis.

In embodiments, the source image may be shrunk such that not the total luminaire display is used to display the source image. Remaining are may be used to provide (further) luminaire light that may correct the luminaire light provided by the displayed source image. For instance, a band of white light may be displayed around a displayed source image or between adjacent displayed source images. The image displayed is indicated as output image, of which part is thus based on the source image. A shrinking factor of up to 50%, such as up to 20% (i.e. shrinking to 80% of area of the luminaire display) may be applied. Hence, in embodiments the method may comprise displaying the source image with a subset of the total number of pixels, thereby providing the output image wherein a first part of the output image, generated by a first subset of pixels, is based on the source image, and a second part, generated by a second subset of pixels, wherein the method further comprises at least temporarily modifying in the modification stage one or more of color and intensity of the pixel light of the second subset of pixels.

The part that is shrunk may essentially literally display the source image, i.e. an unmodified source image. Alternatively, also the displayed source image may be modified, as e.g. described in relation to above embodiments.

When modifying the pixel light of at least a subset of the pixels, the pixels of which the pixel light is modified may all be adjacent, i.e. all pixels that are configured to generate the part of the target image are adjacent to each other, and no pixels in the area of adjacent pixels, generate or are configured to generate unmodified pixel light. In other embodiments, however, the modification is applied to a subset of all pixels that define an area of adjacent pixels that generate or are configured to generate the image part. For instance, the pixels of which the pixel light is modified or is to be modified are randomly chosen within such area. Alternatively, the pixels of which the pixel light is modified or is to be modified are configured in alternating order, such as one or more pixels of which the pixel light is not modified or to be modified configured in between two or more pixels of which the pixel light modified or to be modified. In this way, the modification may be configured in an ordered way wherein pixels of which the pixel light is modified or to be modified alternate with pixels of which the pixel light is no modified or to be modified. In embodiments, the one or more predetermined target optical properties may at least include the color rendering index. For instance, in embodiments the method may comprise executing the modification stage such that luminaire light is obtained having a CRI of at least 70, like at least 75, such as at least 80, like at least 85, such as at least 90, like even more especially in embodiments at least 95. In this way, (white) light may be provided that gives a good to sufficient color rendering.

Alternatively or additionally, the one or more predetermined target optical properties may at least include the color temperature. For instance, in embodiments the method may comprise executing the modification stage such that luminaire light is obtained having a color point within 20 SDCM, especially within 15 SDCM, such as within 10 SDCM from the black body locus, like within 5 SDCM. In this way, white light with a

predetermined color temperature may be provided.

The term white light herein, is known to the person skilled in the art. It especially relates to light having a correlated color temperature (CCT) between about 2000 and 20000 K, especially 2700-20000 K, for general lighting especially in the range of about 2700 K and 6500 K, and for backlighting purposes especially in the range of about 7000 K and 20000 K, and especially within about 15 SDCM (standard deviation of color matching) from the BBL (black body locus), especially within about 10 SDCM from the BBL, even more especially within about 5 SDCM from the BBL.

Hence, in specific embodiments the method may comprise executing the modification stage such that luminaire light is obtained having a CRI of at least 70 and having a color point within 20 SDCM, such as within 15 SDCM, from the black body locus.

Alternatively or additionally, the one or more predetermined target optical properties may at least include the color point.

Having chosen one or more predetermined target optical properties, it may be desirable that the one or more predetermined target optical properties are maintained over time (i.e. during the (remaining) cycle time), also when e.g. other images are subsequently displayed. Hence, in embodiments the method may further comprise displaying a plurality of different output images over time while maintaining one or more of the one or more luminaire light optical properties constant.

In yet a further aspect, the invention also provides a system comprising such (pixelated) luminaire. The system may especially be configured to execute during operation one or more of the above described (method) embodiments, which are described in relation to the method, but which are also applicable to the system. Especially, the pixelated luminaire is configured to display colored images. Of course, in embodiments the pixelated luminaire may also provide during operation black-white images.

Hence, the invention provides amongst others a system comprising (i) a pixelated luminaire for displaying an output image based on an source image, wherein the pixelated luminaire comprises a total number of pixels each configured to generate pixel light having a controllable color and intensity, wherein the pixelated luminaire is configured to generate luminaire light by displaying the output image with the pixelated luminaire, wherein the luminaire light during display of the output image has one or more luminaire light optical properties selected from the group consisting of color point, color temperature and color rendering index, and (ii) a control system, configured to execute in a controlling mode the method according to any one of the preceding claims.

The system, or apparatus, or device may execute an action in a“mode” or “operation mode” or“mode of operation”. Likewise, in a method an action or stage, or step may be executed in a“mode” or“operation mode” or“mode of operation”. The term“mode” may also be indicated as“controlling mode”. This does not exclude that the system, or apparatus, or device may also be adapted for providing another controlling mode, or a plurality of other controlling modes. Likewise, this may not exclude that before executing the mode and/or after executing the mode one or more other modes may be executed.

However, in embodiments a control system may be available, that is adapted to provide at least the controlling mode. Would other modes be available, the choice of such modes may especially be executed via a user interface, though other options, like executing a mode in dependence of a sensor signal or a (time) scheme, may also be possible. The operation mode may in embodiments also refer to a system, or apparatus, or device, that can only operate in a single operation mode (i.e.“on”, without further tunability).

The control system may be a separate control system functionally coupled to the luminaire. In other embodiments, a single device may comprise the luminaire and control system, such as a luminaire comprising the control system. The system may also include a user interface, such as a graphical user interface and/or a remote user interface.

The system may further include one or more sensors for controlling the luminaire and/or the displayed content and/or the optical properties of the luminaire light as function of one or more of time, period of the year, other light (daylight, other artificial light sources), human presence, human movement, etc. etc.

In specific embodiments, the system may further comprise a sensor for analyzing the luminaire light optical properties of the luminaire light, wherein the control system based on this analysis is configured to at least temporarily modify in the modification stage one or more of color and intensity of the generated pixel light of at least a subset of the total number of pixels to generate the luminaire light during display of the output image.

Such sensor may especially be used in a feedback type application (see also above).

As indicated above, the system may be used as additional light, but may even be used as sole light source in a space. Hence, in an aspect the invention also provides the use of the system for general lighting. Of course, other uses, such as the display of information, may also herein be included.

In yet a further aspect, the invention also provides a computer program product, which when run on a computer comprised by or functionally coupled to a system comprising a pixelated luminaire for displaying an output image based on an source image, wherein the pixelated luminaire comprises a total number of pixels each configured to generate pixel light having a controllable color and intensity, wherein the pixelated luminaire is configured to generate luminaire light by displaying the output image with the pixelated luminaire, wherein the luminaire light during display of the output image has one or more luminaire light optical properties selected from the group consisting of color point, color temperature and color rendering index, is capable of bringing about the method as defined herein. In embodiments, the computer may be comprised by the above-described control system.

The lighting device may be part of or may be applied in e.g. office lighting systems, household application systems, shop lighting systems, home lighting systems, accent lighting systems, spot lighting systems, theater lighting systems, pixelated display systems, segmented display systems, warning sign systems, medical lighting application systems, indicator sign systems, decorative lighting systems, portable systems, (outdoor) road lighting systems, urban lighting systems, green house lighting systems, horticulture lighting, etc.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, and in which:

Fig. 1 shows a time pattern for the stimulus presentation for use during a DCR assessment; and Figs. 2a-2h schematically depict some aspects of the herein described invention and its embodiments.

The schematic drawings are not necessarily to scale.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Fig. 1 shows a time pattern for the stimulus presentation for use during a DCR assessment (ITU-T P.910; Fig. 2 thereof). Here, reference Ai indicates a sequence A under test conditions i. References Ar, B indicate sequences A and B, respectively, in the reference source format. Reference Bj indicates sequence B under test condition j. Reference G indicates“grey”, i.e. no display of an image. Ar may e.g. refer to a display of an unmodified source image and Ai may indicate the output image after execution of the modification stage. Likewise, Br may e.g. refer to a display of an unmodified other source image and Bj may indicate the respective (other) output image after execution of the modification stage. During voting, panelist may indicate the impairment score, which is ideally at least 3 on a scale of 5 or 5 on a scale of 10. Voting is indicated with reference“V”. The times indicates are suggested times, and may optionally be changed.

In embodiments, a method of lighting is proposed comprising: (i) analyzing the spectrum of the total image: SUM spectrum and luminous flux of all pixels; (ii) analyzing the image content in terms of a foreground image and a background image (see e.g. Fig. 2b); (iii) analyzing the spectrum of the foreground image: SUM spectrum and luminous flux of all pixels of the foreground image; (iv) analyzing the spectrum of the background image: SUM spectrum and luminous flux of all pixels of the background image; (v) calculating what spectrum and luminous flux of the background image is needed to obtain e.g. the desired CCT on the BBL, and optionally e.g. CRI above 80, of the total image; and (vi) adapting the spectrum and luminous flux of the background image accordingly.

The DCR method may be used to check maintenance of quality and integrity after modification, if such check is desired.

Fig. 2a schematically depicts an embodiment of a system 1000 comprising a pixelated luminaire 100 for displaying an output image 200 based on an source image 300, wherein the pixelated luminaire 100 comprises a total number of pixels each configured to generate pixel light 111 having a controllable color and intensity, wherein the pixelated luminaire 100 is configured to generate luminaire light 101 by displaying the output image 200 with the pixelated luminaire 100, wherein the luminaire light 101 during display of the output image 200 has one or more luminaire light optical properties selected from the group consisting of color point, color temperature and color rendering index. The system 1000 may further comprise a control system 1100, configured to execute in a controlling mode the method as defined herein. The control system 1100 controls the pixelated luminaire 100, and controls display of images on the display. Hence, this Fig. 2a also schematically depicts the pixelated luminaire 100 per se. The pixelated luminaire 100 comprises a display having a display area 102 of the luminaire display, indicated with reference 103. The display area is essentially defined by the plurality of pixels.

By way of example, the pixelated luminaire 100 of Fig. 2a is displaying an output image 200 (on its display). This image is created by the pixel light 111 of the pixels (not individually visible) of the pixelated luminaire 100. Hence, in this way the pixelated luminaire 100 generated luminaire light 101, which can be seen as the integral of all pixel light 111.

The luminaire light 101 may in embodiments be sensed with a sensor 410. Alternatively or additionally, the luminaire light 101 may also be calculated as the spectral composition of the pixel light of each pixel as well as its intensity will be known by the control system 1100.

The individual pixels are not visible in Fig. 2a. Very schematically they are shown in Fig. 2b (as squares), which can be seen as part of a cross-section in the plane of the pixelated luminaire 100 (of Fig. 2a). All pixels 110 together defined the display area 102 of the (display of the) pixelated luminaire 100. The pixelated luminaire may comprise x columns and y rows of pixels. In embodiments, x is at least 50 and y is at least 50. Each pixel 110 may be able to generate white pixel light 111.

Fig. 2c very schematically shows embodiments of the processing. A source image 300 is displayed as output image (I). Here, an unmodified output image, i.e. the image on the display of the pixelated luminaire is displayed. It may be detected and/or calculated that the output image 200 leads to luminaire light having optical properties that are less optimal than desired.

Hence, the output image 200 may be modified to provide a modified output image 200’ (II). The modified output image is also displayed on the display of the pixelated luminaire and is therefore herein also indicated as output image. Hence, in embodiments the method may comprise using a sensor (see also above) for analyzing the luminaire light optical properties of the luminaire light and based on this analysis at least temporarily modifying in the modification stage one or more of color and intensity of the pixel light to be generated of at least a subset of the total number of pixels to generate the luminaire light during display of the output image 200.

The processing rout of III and IV indicate that based on the content of the source image 300, a modified source image 300’, which is also a source image, is generated (III), which is displayed as output image 200 (iv). Hence, the modification stage may comprise analyzing the source image 300 and based on this analysis at least temporarily modifying in the modification stage one or more of color and intensity of the pixel light to be generated of at least a subset of the total number of pixels to generate the luminaire light during display of the output image 200.

The processing of V,IV will in general be the route that is used to arrive at the modified output image 200’.

For degradation category rating the displayed unmodified source image will be compared with the display of the modified source image, i.e. the output image 200 (which can be seen as a modified output image of the output image that is a display of the unmodified source image (top right)). The display of the modified source image is the image at the bottom right. The modified source image itself is shown at the bottom left, and the unmodified source image is shown at the top left.

Fig. 2d schematically depicts an embodiment wherein the source image is considered to contain foreground content 311 and background content 312. When applying a modification of the pixel light, the foreground content and background content may be treated differently. For instance, in embodiments the method may comprise analyzing the source image 300 on source image foreground content 311 and source image background content 312, wherein the method further comprises only applying the modification stage on pixel light 111 of one or more of the pixels 110 used for displaying output image background content 212 corresponding to source image background content 312. Or, in specific embodiments herein the method may further comprise applying the modification stage on the pixel light 111 of one or more of the pixels 110 used for displaying the output image foreground content 211 corresponding to source image foreground content 311, while maintaining a quality of output image foreground content 211 at least equal to or higher than of the output image background content 212 of the output image 200 when compared to source image foreground content 311 and source image background content 312 of the source image 300, respectively, when using a degradation category rating.

Fig. 2e schematically depicts an embodiment wherein the source image 300 is considered to contain central content 321 and edge content 322 (or peripheral content). When applying a modification of the pixel light, the central content and edge content may be treated differently. Hence, in embodiments the method may comprise analyzing the source image 300 on source image center content 321 and source image edge content 322, wherein the method further comprises only applying the modification stage on pixel light 111 of one or more of the pixels 110 used for displaying output image edge content 222 corresponding to source image edge content 322. In specific embodiments the method may further comprises applying the modification stage on the pixel light 111 of one or more of the pixels 110 used for displaying the output image center content 221 corresponding to source image center content 321, while maintaining a quality of output image center content 221 at least equal to or higher than of the output image edge content 222 of the output image 200 when compared to source image center content 321 and source image edge content 322 of the source image 300, respectively, when using a degradation category rating.

In Fig. 2f, schematically an embodiment is depicted wherein shrinking is applied. Hence, the source image that is depicted on the display screen is smaller than the display screen allows. Hence, in principle the DCR (such as ITU-T P.910) of the displayed image may be 5 out of 5 or 10 out of 10, i.e. imperceptible, as that part of the output image that displays the source image is a perfect faithful reproduction of the source image 200. For the sake of understanding, this part of the output image 200 is indicated with reference 200”. Note, however, that is not excluded that also this part is based on a modification of the source image.

In embodiments, modification can be done according to predetermined rules. For instance, always foreground - background analysis can be done, and predetermined modification can be executed after this analysis. In embodiments, modification can be done according to predetermine rules, which are selected after analysis of the source image (as a rule preceding the actual modification stage). For instance, would analysis show that the luminaire light is or will be very colored, a shrinking modification may be executed.

Especially, modification is especially automated, e.g. using algorithms.

Fig. 2g schematically depicts the color diagram according to CIE 1931. This drawing is used to explain a foreground - background processing, though it may also be used for other embodiments described herein. Reference F indicates the color point of the pixel light that creates the foreground content. References Bl and B2 schematically depict the color points of the pixel light that creates the background content. By way of example, two different color points are chosen, Bl and B2, which lead to a sum color point Sl and S2, respectively. In the case of Bl, the relative contributions may be changed to arrive at the desired color point, which is indicated with reference T. Hence, one may arrive at this color point T by choosing the correct contributions of the intensity of the light of the pixels creating the foreground content and of the intensity of the light of the pixels creating the background content. However, in the case of B2, also a color point shift is necessary, as the color point T is not at the connection line between F and B2. This color point shift may be created by shifting the color point of the background content and/or of the foreground content, especially primarily via the background content (pixel light). This scenario may be more likely to happen. For instance, it may require calculation and advanced adaptation of the individual pixels of the background image. For example, adapt the red colored pixels more than e.g. the green pixels of the background image. Otherwise it is not possible to get the light of the total image at 3500 K on the BBL.

Similar images may be shown for center content and edge content. A shrinking modification may be used as a kind of dilution of the luminaire light originating from the displayed source image, with luminaire light of the remainder of the output image (see also Fig. 2f).

Hence, in embodiments the spectrum and luminous flux of the background image may be averaged over all the pixels of the background image. Alternatively or additionally in other embodiments, one may also introduce a gradient in the spectrum and/or luminous flux of the background image. For example, the pixels closer to the edge of the luminaire are adapted more. The obtained effect is preserving the total image and improved light effect. One may also adapt the spectrum and luminous flux of the background image taken into account the relative spectrum and/or luminous flux of the individual pixels of the background image. In this way, the background image may be preserved as much as possible. The obtained effect is that the integrity and the quality of the background image is maintained as good as possible.

One may only adapt the color levels of the colored pixels of the background image. Alternatively or additionally, one may also (slightly) adapt the spectrum and luminous flux of the foreground image. Alternatively or additionally, one may also identify more than one background image such as for example a first and a second background image. The first background image may be adapted more. Alternatively or additionally, one may also identify more than 1 foreground image such as for example a first and a second foreground image.

The first foreground image may be adapted slightly, while the second foreground image is not adapted. Fig. 2h schematically depicts a cross-section of a pixelated luminaire 100.

Also other features are included. Hence, Fig. 2h also schematically depicts the system 1000. The pixelated luminaire 100 has a display 103 having a display area 102. A row y (or column x) of pixels 110 is shown. Each pixel is provided by a light source that is color tunable. Here, a plurality of light sources 210 is shown per pixel, e.g. RGB solid state LEDs. The pixel light 111 of each pixel 111 is controlled via the control system 1100. Downstream of the light source(s) a beam shaping element, such as a collector, may be available. Further, downstream of the light source(s), and also downstream of the optional beam shaping element, a window and/or (window with integrated) diffusor may be configured. The window is indicated with reference W.

The term“plurality” refers to two or more.

The terms“substantially” or“essentially” herein, and similar terms, will be understood by the person skilled in the art. The terms“substantially” or“essentially” may also include embodiments with“entirely”,“completely”,“all”, etc. Hence, in embodiments the adjective substantially or essentially may also be removed. Where applicable, the term “substantially” or the term“essentially” may also relate to 90% or higher, such as 95% or higher, especially 99% or higher, even more especially 99.5% or higher, including 100%.

The term“comprise” includes also embodiments wherein the term “comprises” means“consists of’.

The term“and/or” especially relates to one or more of the items mentioned before and after“and/or”. For instance, a phrase“item 1 and/or item 2” and similar phrases may relate to one or more of item 1 and item 2. The term "comprising" may in an

embodiment refer to "consisting of' but may in another embodiment also refer to "containing at least the defined species and optionally one or more other species".

Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.

The devices, apparatus, or systems may herein amongst others be described during operation. As will be clear to the person skilled in the art, the invention is not limited to methods of operation, or devices, apparatus, or systems in operation. It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims.

In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim.

Use of the verb "to comprise" and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. Unless the context clearly requires otherwise, throughout the description and the claims, the words“comprise”, “comprising”, and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of“including, but not limited to”.

The article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements.

The invention may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In a device claim, or an apparatus claim, or a system claim, enumerating several means, several of these means may be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

The invention also provides a control system that may control the device, apparatus, or system, or that may execute the herein described method or process. Yet further, the invention also provides a computer program product, when running on a computer which is functionally coupled to or comprised by the device, apparatus, or system, controls one or more controllable elements of such device, apparatus, or system.

The invention further applies to a device, apparatus, or system comprising one or more of the characterizing features described in the description and/or shown in the attached drawings. The invention further pertains to a method or process comprising one or more of the characterizing features described in the description and/or shown in the attached drawings.

The various aspects discussed in this patent can be combined in order to provide additional advantages. Further, the person skilled in the art will understand that embodiments can be combined, and that also more than two embodiments can be combined.