Patent Description:
Imagers for measuring the spectrum of light received (e.g., reflected off or transmitted through) from an object are known in the art. Generally, such imagers are referred to as hyperspectral imagers. Such imagers normally employ one of the known in the art techniques such as spatial scanning, spectral scanning, non-scanning or spatio-spectral scanning to spectrally decompose the light entering the imager and generate a hyperspectral image cube. Also known in the art are imagers which acquire image data at selected spectral bands, such as Red, Green and Blue. The wavelengths may be separated by filters. Known in the art techniques, for simultaneously acquiring both a spectral measurement and an image at selected spectral bands require employing two or more sensors, or computing the selected spectral image from the hyperspectral data.

<CIT>, entitled "Spectral Camera with Mosaic of Filters for each Image Pixel," directs to a hyperspectral imaging camera, in which each spatial point sensed in the scene, is spread over a cluster of sensor elements in a sensor array. Geelen directs to material and manufacturing processes for producing Fabry-Perot filters monolithically with the image sensors. According to one embodiment, each cluster of sensor elements has a mosaic of different band pass filters. The clusters of sensor elements produce multiple copies of an image, each copy associated with a respective band. The images can be detected, read out, and stored as a reassembled hyperspectral image cube.

Further according to Geelen et al, each mosaic of sensors may contain a selection of spectral bands with equal bandwidths (i.e., equal wavelength resolution), repeated over the surface of the image sensor. Also, some bands can appear alternately (with lower spatial frequency) in the mosaics of sensors. Furthermore, some spectral bands can have different wavelength resolutions than other bands in the spectrum, or band selection can vary in different parts of the image, such as the periphery and the center of the image sensor. A processor reassembles the image for each band, employing interband prediction methods to estimate spectral data at higher spatial resolution than the spatial cluster frequency. An anti-aliasing part in the optical path can spread the image, for example, by optical filtering or by defocusing. Higher-order filters can be present in order to subtract unwanted higher-order signals from the first-order filtered signals.

<CIT>, entitled "Digital Camera with Integrated Infrared (IR) Response" directs to a digital camera system which includes a plurality of separate photo detector arrays. For example, one photo detector array samples light of a visible spectrum another photo detector array samples infrared (IR) radiation. However, the photo detector arrays are all integrated on or in the same semiconductor substrate. Further integrated on the same semiconductor substrate is a signal processing circuit which generates a composite image using the data representing the intensity of light sampled by the photo detectors.

<CIT>, entitled "Electronic Color Infrared Camera" directs to digital electronic camera which includes a solid state color image sensor having an array of image sensing elements and an array of color filters arranged over the image sensing elements for producing a color image. The filters include infrared filters that block blue light and pass infrared light. The camera further includes a signal processing circuit for processing the image signals from the sensor to produce a false color image.

<CIT>, entitled "In-line image sensor in combination with linear variable filter based spectrophotometer", is directed to a photosensitive apparatus including a full width array of photosensors and a first photosensor chip. The first photosensor chip includes a linear array of photosensors having a plurality of pixels arranged in a long direction and a linear variable filter adapted to transmit at least ten unique bandwidths of wavelengths of light along a length of the linear variable filter where the linear variable filter is fixedly secured to the linear array. Each respective pixel receives a unique bandwidth of wavelengths of light as a light passes through the linear variable filter and the length is aligned with the long direction. The full width array of photosensors is arranged perpendicular to a process direction of a printing device.

<CIT>, entitled "Geometric referencing of multi-spectral data" is directed to a sensing device for obtaining geometric referenced multi-spectral image data of a region of interest in relative movement with respect to the sensing device. The device includes a first two dimensional sensor element and a spectral filter. The sensing device obtains subsequent multi-spectral images during the relative motion of the region of interest with respect to the sensing device, thus providing spectrally distinct information for different parts of a region of interest using different parts of the first sensor. A second two dimensional sensor element, using the second sensor element, provides an image of the region of interest for generating geometric referencing information to be coupled to the distinct spectral information.

The claimed invention is defined by the features set out in the appended independent claim.

Unless explicitly indicated as "embodiment of the claimed invention", any embodiment in the description may include some but not all features defined in the appended claims and are hereby present for illustration purposes only and as being useful for understanding the claimed invention.

The disclosed technique overcomes the disadvantages of the prior art by providing a combined imaging and spectral measurement line-scan sensor array, which includes a plurality of sensor elements lines, each line including a plurality of sensor elements. The combined imaging and spectral measurement line-scan sensor array is integrated on a single semiconductor substrate. Herein, sensor elements are also referred as 'pixels'. According to one alternative, a portion of the pixel lines are designated for acquiring an image, referred to herein as 'imaging lines' while the remaining portion of the pixel lines are associated with spectral measurements and referred to herein as 'spectral measurement lines'. According to another alternative, all of the pixel lines are imaging lines. Each imaging line acquires an image over a respective spectral band. The spectral bands may be mutually exclusive, partially overlapping or completely overlapping. As such, an image acquired by the imaging lines by a color image in a selected color space (e.g., Red, Green and Blue - RGB, Cyan Magenta Yellow - CYM, XYZ and the like) as well as an image in the Short Wave Infrared (SWIR) and the Long Wave Infrared (LWIR) spectral bands or any combination thereof.

Each imaging line is associated with a respective spectral band referred to herein as the 'line spectral band'. Each pixel in each spectral measurement line is associated with a respective spectral band referred to herein as the 'pixel spectral band'. Each of multiple (e.g., of at least three, at least four, at least five etc.) pixels in each of spectral measurement lines is respectively associated with different respective pixel spectral bands. The different respective pixel spectral bands are non-identical to any one of the line spectral bands associated with each of the imaging spectral lines. In general, the line spectral bands are substantially larger (i.e., exhibit a larger bandwidth) than the pixel spectral band. Also, each spectral measurement line may be divided into a plurality of groups of adjacent pixels. Each group is associated with the same group spectral range and each pixel in the group is associated with a respective pixel spectral band.

Reference is now made to <FIG>, which is a schematic illustration of a combined imaging and spectral measurement line-scan sensor, generally referenced <NUM>, constructed and operative in accordance with an embodiment of the disclosed technique. Imaging sensor <NUM> includes three pixel lines <NUM><NUM>, <NUM><NUM> and <NUM><NUM>. Lines <NUM><NUM> and <NUM><NUM> are imaging lines for acquiring images over selected spectral bands. Each one of lines <NUM><NUM> and <NUM><NUM> is associated with a respective line band. Line <NUM><NUM> is associated with a first one spectral band and line <NUM><NUM> is associated with a second line spectral band. For example, line <NUM><NUM> is associated with the visible part of the spectrum (i.e., the first line spectral band is in the visible part of the spectrum) and line <NUM><NUM> is associated with the infrared (IR) part of the spectrum (i.e., the second line spectral band is in the IR part of the spectrum). The first line spectral band and the second line spectral band are either mutually exclusive, partially overlap or completely overlap within the same part of the spectrum. For example, the first line spectral band is Near Infrared (NIR) and the second line spectral band is Far infrared (FIR). As a further example, the first line spectral band is between <NUM> nanometers (nm) and <NUM> and the second line spectral band is between <NUM> and <NUM>. Accordingly, a filter exhibiting the desired respective response over the line spectral band (i.e., either a similar response or a different response) is placed over the pixels in lines <NUM><NUM> and <NUM><NUM>.

Line <NUM><NUM> is a spectral measurement line, for example, for measuring the spectrum of light received (e.g., reflected) from an object. Each one of pixels <NUM><NUM>-<NUM>N in line <NUM><NUM> is associated with a respective one of pixel spectral bands B<NUM>-BN. Accordingly, a filter (e.g., a Fabry-Perot filter) exhibiting a response over the desired spectral band is placed over each one of pixels <NUM><NUM>-<NUM>N in lines <NUM><NUM>. It is noted that the term 'placed' herein above and below relates to the physical association between a filter and respective pixel of group of pixels. In practice, for example, the filter or filters to be placed over pixels in an imaging sensor may be produced on a glass plate, covering the sensor area. The glass plate is then positioned over the sensor in alignment with the pixels. Also, the filter or filters may be directly deposited on the sensor itself. It is further noted that in <FIG>, the dashed lines represent pixels and the solid lines represent filters over pixels.

In general, within spectral measurement line <NUM><NUM>, each of multiple pixels <NUM><NUM>-<NUM>N is respectively associated with different respective spectral band (i.e., multiples of spectral bands B<NUM>-BN are different from each other). The different respective pixel spectral bands are non-identical to any one of the single spectral responses associated with each of the imaging spectral lines. Furthermore, these spectral bands need not be adjacent to each other (i.e., may not result in a single continuous band).

Optionally, as depicted in <FIG>, spacing exists between lines <NUM><NUM>, <NUM><NUM> and <NUM><NUM>. In <FIG> a gap, 'W1', exists between line <NUM><NUM> and line <NUM><NUM> and a gap, 'W2' exists between line <NUM><NUM> and line <NUM><NUM>. Gap W1 prevents light from the filters located over the pixels in line <NUM><NUM> to be received by the pixels in line <NUM><NUM> and vice versa. Similarly, Gap W2 prevents light from the filters located over the pixels in line <NUM><NUM> to be received by the pixels in line <NUM><NUM> and vice versa.

It is noted that a combined imaging and spectral measurements line-scan sensor may include more than two imaging lines and more than one spectral measurement lines. For example, when acquiring a Cyan, Magenta, Yellow and Black (CMYK) image simultaneously with a spectral measurement of the light reflected of object being imaged, an imaging sensor according to the disclosed technique shall include at least five lines, four imaging lines and one spectral measurement line. Three imaging lines exhibit a spectral response corresponding to cyan, magenta and yellow (i.e., in the visible part of the spectrum) and the fourth imaging line exhibit a spectral response in the IR part of the spectrum from which the value of black is derived. The fifth line is a spectral measurement line similar to the spectral measurement line described above. Also, each spectral measurement line may be divided into a plurality of groups of adjacent pixels. Each group is associated with the same group spectral range and each pixel in the group is associated with a respective pixel spectral band.

Reference is now made to <FIG>, which is a schematic illustration of another exemplary combined imaging and spectral measurement sensor, generally referenced <NUM>, constructed and operative in accordance with another embodiment of the disclosed technique. Exemplary sensor <NUM> acquires images in the visible part of the spectrum. Exemplary sensor <NUM> includes <NUM> lines of sensors <NUM><NUM>-<NUM><NUM>. Lines <NUM><NUM>, <NUM><NUM> and <NUM><NUM> are imaging lines associated with and lines <NUM><NUM>, <NUM><NUM> and <NUM><NUM> are spectral measurement lines associated. In <FIG>, the dashed lines represent pixels and the solid lines represent filters over pixels.

Each of one imaging lines <NUM><NUM>, <NUM><NUM> and <NUM><NUM> is associated with a single respective line spectral response. To that end, a filter exhibiting a response in the desired spectral band is placed over the pixels in each line. In sensor <NUM>, the spectral response associated with line <NUM><NUM> is in the long visible band also referred to herein as "red spectral band". The spectral response associated with line <NUM><NUM> is in the medium visible bands (e.g., between <NUM> and <NUM>) also referred to herein as "green spectral bands". The spectral response associated with line <NUM><NUM> is in the short visible band (e.g., between <NUM> and <NUM>) also referred to herein as "blue spectral band".

Also in sensor <NUM>, each one of spectral measurement lines <NUM><NUM>, <NUM><NUM> and <NUM><NUM> is divided into a plurality of groups of adjacent pixels. Spectral measurement line <NUM><NUM> is divided into groups <NUM><NUM>-<NUM>M. Spectral measurement line <NUM><NUM> is divided into groups <NUM><NUM>-<NUM>M and spectral measurement line <NUM><NUM> is divided into groups <NUM><NUM>-<NUM>M. Each group in each spectral measurement line is associated with the same group spectral range. Thus, the spectral band associated with groups <NUM><NUM>-<NUM>M is between <NUM> and <NUM>. The spectral band associated with groups <NUM><NUM>-<NUM>M is between <NUM> and <NUM> and the spectral band associated with groups <NUM><NUM>-<NUM>M is between <NUM> and <NUM>.

Furthermore, the corresponding pixels in each group of pixels are associated with the same respective pixel spectral band. To that end, a filter (e.g., a Fabry-Perot filter) exhibiting a response in the desired spectral band is placed over each pixel. For example, pixels <NUM><NUM>, <NUM><NUM>,. , <NUM>M1 are associated with the same spectral band (i.e., <NUM>-<NUM>), pixels <NUM><NUM>, <NUM><NUM>,. , <NUM>M1 are associated with the same spectral band (i.e., <NUM>-<NUM>) and pixels <NUM><NUM>, <NUM><NUM>,. , <NUM>M1 are associated with the same spectral band (i.e., <NUM>-<NUM>). Similarly, pixels <NUM><NUM>, <NUM><NUM>,. , <NUM>M2 are associated with the same spectral band (i.e., <NUM>-<NUM>), pixels <NUM><NUM>, <NUM><NUM>,. , <NUM>M1 are associated with the same spectral band (i.e., <NUM>-<NUM>) and pixels <NUM><NUM>, <NUM><NUM>,. , <NUM>M2 are associated with the same spectral band (i.e., <NUM>-<NUM>) etc. In general, similar to as mentioned above, within at least one of spectral measurement lines <NUM><NUM>, <NUM><NUM> and <NUM><NUM> each of multiple pixels is respectively associated with different respective pixel spectral bands. The different respective pixel spectral bands are non-identical to any one of the single spectral responses associated with each of the imaging spectral lines.

Optionally, as depicted in <FIG>, spacing exists between lines <NUM><NUM>-<NUM><NUM>. In <FIG>, a gap, 'W1', exist between line <NUM><NUM> and line <NUM><NUM> and a gap, 'W2' exists between line <NUM><NUM> and line <NUM><NUM>. Gap W1 prevents light from the filters located over the pixels in line <NUM><NUM> to be received by the pixels in line <NUM><NUM> and vice versa. Similarly, Gap W2 prevents light from the filters located over the pixels in line <NUM><NUM> to be received by the pixels in line <NUM><NUM> and vice versa. Also optionally, opaque strips, such as metal strips <NUM>, <NUM><NUM> and <NUM><NUM> are positioned between line <NUM><NUM> and <NUM><NUM>, between line <NUM><NUM> and <NUM><NUM>, between line <NUM><NUM> and <NUM><NUM> respectively. Metal strip <NUM><NUM> prevents light from the filters located over the pixels in line <NUM><NUM> to be received by the pixels in line <NUM><NUM> and vice versa. Metal strip <NUM><NUM> prevents light from the filters located over the pixels in line <NUM><NUM> to be received by the pixels in line <NUM><NUM> and vice versa. Metal strip <NUM><NUM> prevents light from the filters located over the pixels in line <NUM><NUM> to be received by the pixels in line <NUM><NUM> and vice versa. In general, a metal strip and a gap provide the same functionality (i.e., a metal strip and a gap are interchangeable). However, the width of a metal strip may be smaller than the width of a gap but fabricating a metal strip may be more complex. The term 'spacing' herein above and below relate to a gap or an opaque strip. Also a metal strip is brought herein as an example only. Any opaque material suitable for fabrication on the sensor substrate may be employed. Furthermore, a combination of an opaque strip and a gap may also be employed.

It is noted that spacing is required between the lines due to the uncertainty in the size of each pixel and filter regardless of the spectral response of the filters. For example, two adjacent pixels may exhibit width of <NUM> micrometers. However the filters placed over these pixels may exhibit widths different from <NUM> micrometers (e.g., due to manufacturing tolerances). As such, there is a probability that the coverage of a filter associate with one pixel overlaps adjacent pixels. Therefore, employing spacing such as described above alleviates such an uncertainty and result in a one to one correspondence between a filter and corresponding pixel or pixels. Nevertheless, when the process employed during manufacturing of an imaging sensor of the disclosed technique results in a sufficiently low probability that the coverage of a filter associated with one pixel would overlap adjacent pixels, then the use of metal strips or spacing may not be necessary. For example, the process employed may result in a probability of <NUM> percent that a filter shall overlap with a neighboring pixel by at most <NUM> nanometers. The designer may decide that with such probability and overlap, the performance of the sensor (e.g., Signal to Noise Ratio - SNR) would not be affected such that the sensor is rendered un-usable. As such, the designer may decide that opaque strips or spacing are not necessary.

Reference is now made to <FIG>, which is a schematic illustration of another exemplary combined imaging and spectral measurement sensor, generally referenced <NUM>, constructed and operative in accordance with a further embodiment of the disclosed technique. In sensor <NUM>, Lines <NUM>, <NUM>, <NUM><NUM>, <NUM><NUM> are imaging lines and lines <NUM><NUM> and <NUM><NUM> are spectral measurement lines. In <FIG>, the dashed lines represent pixels and the solid lines represent filters over the pixels. Each one of imaging lines <NUM>, <NUM>, <NUM><NUM>, <NUM><NUM> is associated with a single respective line spectral band.

Line <NUM> is an imaging line associated with the red spectral band. Accordingly, each of the pixels in line <NUM> includes a respective filter (e.g., a red dichroic filter). Line <NUM> is an imaging line associated with the green spectral band. Accordingly, each of the pixels in line <NUM> includes a respective filter (e.g., a green dichroic filter). Lines <NUM>, and <NUM><NUM> are imaging lines associated with the blue spectral band. As such, similar to lines <NUM> and <NUM>, each of the pixels in lines <NUM><NUM> and <NUM><NUM> includes a respective filter (e.g., a blue dichroic filter). When employed for line scanning (similarly to as explained below in conjunction with <FIG>), Time Delay Integration (TDI) may be employed with blue pixels in lines <NUM><NUM> and <NUM><NUM> thereby increasing the sensitivity of sensor <NUM> in the blue spectral band. It is noted that two imaging lines associated with the blue spectral response are employed since, in general, the pixels may exhibit a weaker response in the blue spectral than in the red and the green spectral bands. Furthermore, the lighting employed with the blue sensor may exhibit weaker emission in the blue spectral band than in the red and the green spectral bands. However, in general, either one of the red, blue or green spectral bands may be associated with one or more respective pixel lines.

Optionally, an opaque strip such as metal strip <NUM> is positioned between line <NUM> and <NUM>. This metal strip prevents light from the filters located over the pixels in line <NUM> to be received by the pixels in line <NUM>. Also optionally, line <NUM> and line <NUM><NUM> are separated with a combination of a metal strip <NUM> and two gaps 'W1' between line <NUM> and metal strip <NUM> and a gap 'W2' between metal strip <NUM> and line <NUM><NUM>. 'W2', separate line <NUM><NUM> and line <NUM><NUM>. Similar to as described above, a gap and a metal strip or a combination thereof have the same functionality of preventing light from the filters located over the pixels in one line to be received by the pixels in an adjacent line. It is noted that no spacing exists between lines <NUM><NUM> and <NUM><NUM> and between lines <NUM><NUM> and <NUM><NUM> since the pixels in these lines are designated to receive the same spectral band.

Spectral measurement lines <NUM><NUM> and <NUM><NUM> are divided into a plurality of groups <NUM><NUM>-<NUM>M of adjacent pixels. In the example depicted in <FIG>, each group includes twelve spectral bands. Each one of groups <NUM><NUM>-<NUM>M is associated with a respective group spectral range. In <FIG>, the spectral band associated with each one of groups <NUM><NUM>-<NUM>M is between <NUM> and <NUM>. In lines <NUM><NUM> and <NUM><NUM>, each filter (e.g., a Fabry-Perot filter) is placed over an area of four pixels (i.e., two pixels in line <NUM><NUM> and two pixels in line <NUM><NUM>). However, in <FIG>, each filter (i.e., except for the boundary filters) covers two vertically adjacent pixels, the half of the two left vertically adjacent pixels and the half of the two right vertically adjacent pixels (i.e., these pixels are associated with the same pixel spectral band as defined by the filter). Furthermore, only every second pair of vertically adjacent pixels <NUM><NUM>, <NUM><NUM>, <NUM><NUM>,. , <NUM>N is read out. Accordingly, only pairs <NUM><NUM>, <NUM><NUM>,. , <NUM>N-<NUM> of vertically adjacent pixels are read out while pairs <NUM><NUM>, <NUM><NUM>,. , <NUM>N are employed as barriers preventing light from the filters located over, for example, pair <NUM><NUM> of vertically adjacent pixels to be received by pairs <NUM><NUM> of vertically adjacent pixels.

Similar to as described above, in general, within spectral measurement lines <NUM><NUM> and <NUM><NUM> each of multiples of vertically adjacent pixels <NUM><NUM>, <NUM><NUM>, <NUM><NUM>,. , <NUM>N are respectively associated with different respective spectral bands. The different respective spectral bands are non-identical to any one of the single spectral responses associated with each of the imaging spectral lines. In other words, at least two pairs of vertically adjacent pixels <NUM><NUM>, <NUM><NUM>, <NUM><NUM>,. , <NUM>N is each associated with a different respect spectral band. It is noted that pairs of vertically adjacent pixels are brought herein as an example only, according to the disclosed technique, triplets, quadruplets etc. may be similarly employed.

<FIG> depicts an exemplary implementation of the case where for each pixel line (e.g., a spectral measurement line), a filter is placed over at least three adjacent pixels such that the filter overlaps the at least three adjacent pixels, completely covering a middle at least one of said at least three adjacent pixels. Also only the pixels that are completely covered by the filter are read out. For example, the filter exhibiting response in the wavelengths between <NUM>-<NUM> nanometers overlaps with pairs vertically adjacent pixels <NUM><NUM>, <NUM><NUM> and <NUM><NUM> (i.e., the respective pixel in each of spectral measurement lines <NUM><NUM> and <NUM><NUM>) and completely covers pair of vertically adjacent pixels <NUM><NUM>.

Reference is now made to <FIG>, which is a schematic illustration of the imaging and spectral measurement line-scan sensor, generally referenced <NUM>, constructed and operative in accordance with an embodiment of the claimed invention. Line-scan sensor <NUM> is similar to line-scan sensor <NUM> however with differences described below. In sensor <NUM>, Lines <NUM>, <NUM>, <NUM><NUM>, <NUM><NUM> are imaging lines and lines <NUM><NUM> and <NUM><NUM> are spectral measurement lines. In <FIG>, the dashed lines represent pixels. Each one of imaging lines <NUM>, <NUM>, <NUM><NUM>, <NUM><NUM> is associated with a single respective line spectral band.

Line <NUM> is an imaging line associated with the red spectral band. Accordingly, each of the pixels in line <NUM> includes a respective filter (e.g., a red dichroic filter). Line <NUM> is an imaging line associated with the green spectral band. Accordingly, each of the pixels in line <NUM> includes a respective filter (e.g., a green dichroic filter). Lines <NUM><NUM> and <NUM><NUM> are imaging lines associated with the blue spectral band. As such, similar to lines <NUM> and <NUM>, each of the pixels in lines <NUM><NUM> and <NUM><NUM> includes a respective filter (e.g., a blue dichroic filter). When employed for line scanning (similarly to as explained below in conjunction with <FIG>), Time Delay Integration (TDI) may be employed with blue pixels in lines <NUM><NUM> and <NUM><NUM> thereby increasing the sensitivity of sensor <NUM> in the blue spectral band. Similar to as described above, two imaging lines associated with the blue spectral response are employed since, in general the, the pixels may exhibit a weaker response in the blue spectral than in the red and the green spectral bands or the lighting employed with the sensor may exhibit weaker emission in the blue spectral band than in the red and the green spectral bands.

Optionally, an opaque strip such as metal strip <NUM> is positioned between line <NUM> and <NUM>. This metal strip prevents light from the filters located over the pixels in line <NUM> to be received by the pixels in line <NUM>. Also optionally, a gap, 'W1', separates line <NUM> and line <NUM><NUM> and a gap, 'W2', separates line <NUM><NUM> and line <NUM><NUM>. Similar to as described above, a gap and a metal strip or a combination thereof have the same functionality of preventing light from the filters located over the pixels in one line to be received by the pixels in an adjacent line. It is noted that no spacing exists between lines <NUM><NUM> and <NUM><NUM> and between lines <NUM><NUM> and <NUM><NUM> since the pixels in these lines are designated to receive the same spectral band.

Spectral measurement lines <NUM><NUM> and <NUM><NUM> are divided into a plurality of groups <NUM><NUM>-<NUM>M of adjacent pixels. In the example depicted in <FIG>, each group includes eight spectral bands. Each one of groups <NUM><NUM>-<NUM>M is associated with a respective group spectral range. In lines <NUM><NUM> and <NUM><NUM>, each filter (e.g., a Fabry-Perot filter), respective of each spectral band, is placed over an area of four pixels (i.e., two pixels in line <NUM><NUM> and two pixels in line <NUM><NUM>). Each two adjacent groups of four pixels <NUM><NUM>-<NUM>N is separated by two vertically adjacent pixels <NUM><NUM>-<NUM>N-<NUM>. Each of two vertically adjacent pixels <NUM><NUM>-<NUM>N-<NUM> are covered with an opaque material. This opaque material is employed as barriers preventing light from the filters located over, for example, group <NUM><NUM> of four pixels to be received by group <NUM><NUM>. Thus, only groups <NUM><NUM>-<NUM>N are read out.

Similar to as described above, in general, within spectral measurement lines <NUM><NUM> and <NUM><NUM> at least a group of four pixels <NUM><NUM>, <NUM><NUM>, <NUM><NUM>,. , <NUM>N and a second group of four pixels <NUM><NUM>, <NUM><NUM>, <NUM><NUM>,. , <NUM>N are respectively associated with a first spectral band and a second spectral band. The first spectral band is different from the second spectral band. In other words, at least two groups of four pixels <NUM><NUM>, <NUM><NUM>, <NUM><NUM>,. , <NUM>N is each associated with a different respect spectral band.

Reference is now made to <FIG>, which is a schematic illustration of a further exemplary line-scan imaging sensor, generally referenced <NUM>, constructed and operative in accordance with a further embodiment of the disclosed technique. Line scan sensor <NUM> includes six imaging lines <NUM><NUM>-<NUM><NUM>. Each one of imaging lines <NUM><NUM>-<NUM><NUM> is associated with a single respective line spectral band. To that end, a filter exhibiting a response in the desired spectral band is placed over the line of pixels. In sensor <NUM>, the spectral band associated with line <NUM><NUM> is between <NUM> and <NUM>. The spectral band associated with line <NUM><NUM> is between <NUM> and <NUM>. The spectral band associated with line <NUM><NUM> is between <NUM> and <NUM>. The spectral band associated with line <NUM><NUM> is between <NUM> and <NUM>. The spectral band associated with line <NUM><NUM> is between <NUM> and <NUM>. The spectral band associated with line <NUM><NUM> is between <NUM> and <NUM>.

Optionally, as depicted in <FIG>, spacing exists between lines <NUM><NUM>-<NUM><NUM>. In <FIG>, a gap, 'W1', separates line <NUM><NUM> and line <NUM><NUM> and a gap, 'W2' separates line <NUM><NUM> and line <NUM><NUM>. Gap W1 prevents light from the filters located over the pixels in line <NUM><NUM> to be received by the pixels in line <NUM><NUM> and vice versa. Similarly, Gap W2 prevents light from the filters located over the pixels in line <NUM><NUM> to be received by the pixels in line <NUM><NUM> and vice versa. Also optionally, opaque strips such as metal strips <NUM>, <NUM><NUM> and <NUM><NUM> are positioned between line <NUM><NUM> and <NUM><NUM>, between line <NUM><NUM> and <NUM><NUM>, between line <NUM><NUM> and <NUM><NUM> respectively. Metal strip <NUM><NUM> prevents light from the filters located over the pixels in line <NUM><NUM> to be received by the pixels in line <NUM><NUM> and vice versa. Metal strip <NUM><NUM> prevents light from the filters located over the pixels in line <NUM><NUM> to be received by the pixels in line <NUM><NUM> and vice versa. Metal strip <NUM><NUM> prevents light from the filters located over the pixels in line <NUM><NUM> to be received by the pixels in line <NUM><NUM> and vice versa.

The arrangement of lines <NUM><NUM>-<NUM><NUM>, with respect to the line spectral bands thereof is brought herein as an example only. As another example the line spectral band associated with line <NUM><NUM> is between <NUM> and <NUM>. The line spectral band associated with line <NUM><NUM> is between <NUM> and <NUM>. The line spectral band associated with line <NUM><NUM> is between <NUM> and <NUM>. The line spectral band associated with line <NUM><NUM> is between <NUM> and <NUM>. The line spectral band associated with line <NUM><NUM> is between <NUM> and <NUM>. The line spectral band associated with line <NUM><NUM> is between <NUM> and <NUM>.

In general, the complexity, and consequently the cost of a combined imaging and spectral measurement line-scan sensor, increases with the number of different filters employed (i.e., with respect to spectral response to the filter). In other words, the complexity increases as the number different filters exhibiting a different spectral response increases. As such, it would be advantageous to decrease the number of filters employed in a given system. Reference is now made to <FIG>, which are schematic illustrations of exemplary spectral responses of filters, generally referenced <NUM>, <NUM>, <NUM>, <NUM>, <NUM><NUM> and <NUM>, in accordance with another embodiment of the disclosed technique. In <FIG>, 'λ' represents wavelength. It is noted that spectral responses <NUM>, <NUM>, <NUM><NUM> and <NUM> are multi-peaked spectral responses and that each such multi-peaked spectral responses is associated with a single filter. In general, <FIG> depict the transmittance response of the filters. <FIG> depicts three spectral responses <NUM>, <NUM> and <NUM>, each corresponding to a respective filter, over a respective spectral range ΔλR1, ΔλR2 and ΔλR3. For the purpose of explanation, filters exhibiting a spectral response such as spectral response <NUM>, <NUM> and <NUM> shall be referred to herein as "wideband" filters. For example, spectral range ΔλR1, ΔλR2 and ΔλR3 are in the visible range of the electromagnetic where ΔλR1 corresponds to the blue range, ΔλR2 corresponds to the green range and ΔλR3 corresponds to the red range.

<FIG> depicts the spectral response <NUM> of a fourth filter. Spectral response <NUM> exhibits a multi-narrowband response over the spectral range Δλn4 and includes four spectral bands <NUM><NUM>, <NUM><NUM>, <NUM><NUM> and <NUM><NUM>, each over respective one of spectral ranges ΔλR41, ΔλR42, ΔλR43 and ΔλR44. Spectral band <NUM><NUM> is, for example, over the IR part of the spectrum.

<FIG> depicts the spectral response <NUM> of a fifth filter. Spectral response <NUM> exhibits a multi-narrowband response over the spectral range ΔλR5 and includes four spectral bands <NUM><NUM>, <NUM><NUM>, <NUM><NUM> and <NUM><NUM>, each over respective one of spectral ranges ΔλR51, ΔλR52, ΔλR53 and ΔλR54. Spectral band <NUM><NUM> is, for example, over the IR part of the spectrum.

<FIG> depicts the spectral response <NUM> of a sixth filter. Spectral response <NUM> exhibits a multi-narrowband response and includes over the spectral range ΔλR6 four spectral bands <NUM><NUM>, <NUM><NUM>, <NUM><NUM> and <NUM><NUM> each over respective one of spectral ranges ΔλR61, ΔλR62, ΔλR63 and ΔλR64. Spectral band <NUM><NUM> is, for example, over the IR part of the spectrum.

For the purpose of explanation, and as mentioned above, filters exhibiting a spectral response such as spectral response <NUM>, <NUM> and <NUM> shall be referred to herein as "multi-narrowband" filters. Also, the bandwidths, ΔλR41, ΔλR42, ΔλR43 and ΔλR44, of each spectral band <NUM><NUM>, <NUM><NUM>, <NUM><NUM> and <NUM><NUM>, are smaller than the bandwidth ΔλR4 of the spectral response <NUM> of the filter. Similarly, each of the bandwidths, ΔλR51, ΔλR52, ΔλR53 and ΔλR54, of each spectral band <NUM><NUM>, <NUM><NUM>, <NUM><NUM> and <NUM><NUM>, are smaller than the bandwidth ΔλR5 of the spectral response <NUM> of the filter, and the bandwidths, ΔλR61, ΔλR62, ΔλR63 and ΔλR64, of each spectral band <NUM><NUM>, <NUM><NUM>, <NUM><NUM> and <NUM><NUM>, is smaller than the bandwidth ΔλR6 of the spectral response <NUM> of the filter.

According to the embodiments of the disclosed technique described herein above in conjunction with <FIG>, and herein below in conjunction with <FIG> and <FIG>, a unique pixel spectral band is achieved by placing a "wideband" filter (e.g. exhibiting response <NUM> - <FIG>) and a "multi-narrowband filter" (e.g. exhibiting response <NUM> - <FIG>) one on top of the other, where the bandwidth of the wideband filter (e.g., ΔλR1) spans a narrower wavelength range than that of the multi-narrowband filter (e.g., ΔλR4) but is wider than the wavelength range spanned by each single band (e.g., ΔλR41) within the multi-narrowband filter. Superimposing, a wideband filter (e.g., exhibiting spectral response <NUM>), over a multi-narrowband filter (e.g., exhibiting for example spectral response <NUM>), results in a composite filter exhibiting a spectral response, for example, of only <NUM><NUM> over spectral range ΔλR41. <FIG> depicts the spectral response <NUM> resulting from superimposing a selected one of filters exhibiting responses <NUM>, <NUM> and <NUM> over a selected one of filters exhibiting responses <NUM>, <NUM> and <NUM>, respectively. Spectral response <NUM> exhibits a multi-band response including twelve spectral bands <NUM><NUM>, <NUM><NUM>, <NUM><NUM>, <NUM><NUM>, <NUM><NUM>, <NUM><NUM>, <NUM><NUM>, <NUM><NUM>, <NUM><NUM>, <NUM><NUM>, <NUM><NUM> and <NUM><NUM> (i.e., twelve channels), each over a respective spectral range Δλ<NUM>, Δλ<NUM>, Δλ<NUM>, Δλ<NUM>, Δλ<NUM>, Δλ<NUM>, Δλ<NUM>, Δλ<NUM>, Δλ<NUM>, Δλ<NUM>, Δλ<NUM> and Δλ<NUM>. Thus twelve channels are achieved with only six filters.

As mentioned above, according to one example, the filter exhibiting response <NUM>, <NUM> and <NUM> are RGB filters, where the filter exhibiting response <NUM> is associated with the color blue (e.g., a blue dichroic filter), the filter exhibiting response <NUM> is associated with the color green (e.g., a green dichroic filter), the filter exhibiting response <NUM> is associated with the color red (e.g., a red dichroic filter). In general, such filters are commonly employed in color imaging sensors. As such, employing such filters, along with additional filters which exhibit responses similar to responses <NUM>, <NUM> and <NUM> (<FIG> respectively), results in spectral measurement sensor with a reduced number of filters. The number of filters may further be reduced by employing an overlap (i.e., either existing overlap or designed overlap) between the RGB filters. Reference is now made to <FIG>, which is a schematic illustration of exemplary spectral responses of filters, generally referenced <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and <NUM>, in accordance with a further embodiment of the disclosed technique. <FIG> depicts the transmittance response of the filters. The overlap between spectral response <NUM> and spectral response <NUM> creates a spectral band over spectral range Δλ4. The overlap between spectral response <NUM> and spectral response <NUM> over creates a spectral band over spectral range Δλ8. The superposition of spectral response <NUM> and spectral response <NUM> creates a spectral band over spectral ranges Δλ1. The superposition of spectral response <NUM> and spectral response <NUM> creates a spectral band over spectral ranges Δλ2. The superposition of spectral response <NUM> and spectral response <NUM> creates a spectral band over spectral ranges Δλ3. Similarly the superposition of spectral response <NUM> with spectral responses <NUM>, <NUM> and <NUM> creates spectral bands over spectral ranges Δλ5, Δλ6 and Δλ7 respectively and the superposition of spectral response <NUM> with spectral responses <NUM>, <NUM> and <NUM> creates spectral bands over spectral ranges Δλ9, Δλ10 and Δλ11 respectively. Spectral ranges Δλ1- Δλ11 are, for example, in the visible part of the spectrum and spectral ranges Δλ12- Δλ14 are in the IR part of the spectrum. In the example brought forth in <FIG>, fourteen channels are achieved with only six filters.

The spectral responses depicted in <FIG> and <FIG> are for illustration purposes only. In general, the spectral responses of the filters should be designed according to design specifications and requirements. Such specification and requirements include, for example, overlapping of the transmittance spectral response between spectrally adjacent filters, the spectrum of the light illuminating the object, the inherent quantum efficiency (i.e., relative signal generated by light at each wavelength) of each pixel and the quantization resolution. An example of the effects of overlap of the transmittance spectral response between spectrally adjacent filters and quantization is brought forth herein below in conjunction with <FIG>.

Reference is now made to <FIG>, <FIG>, <FIG> and <FIG>, which are schematic illustrations of an exemplary combined imaging and spectral measurement sensor, generally referenced <NUM>, constructed and operative in accordance with another embodiment of the disclosed technique. <FIG> depicts a top view of sensor <NUM>, <FIG> depict side view of sensor <NUM> and <FIG> is an isometric view of sensor <NUM>. Spectral measurement line-scan sensor <NUM> includes three green filters <NUM>, <NUM> and <NUM> demarked 'G' in <FIG>, three red filters <NUM>, <NUM> and <NUM> demarked 'R' in <FIG> and three blue filters <NUM>, <NUM> and <NUM> demarked 'B' in <FIG>. Green filters <NUM>, <NUM> and <NUM> exhibit a spectral response similar to spectral response <NUM> or spectral response <NUM>. Red filters <NUM>, <NUM> and <NUM> exhibit a spectral response similar to spectral response <NUM> or spectral response <NUM>. Blue filters <NUM>, <NUM> and <NUM> exhibit a spectral response similar to spectral response <NUM> or spectral response <NUM>.

Filters <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and <NUM> are positioned over respective pixels (not shown) on sensor <NUM>. A filter <NUM> is placed over green filter <NUM>, red filter <NUM>, blue filter <NUM> and over pixel <NUM> (i.e., the space between pixel <NUM> and filter <NUM> is clear). Filter <NUM> exhibits, for example a spectral response similar to spectral response <NUM> (<FIG>). A filter <NUM> is placed over green filter <NUM>, red filter <NUM>, blue filter <NUM> and over pixel <NUM> (i.e., the space between pixel <NUM> and filter <NUM> is clear). Filter <NUM> exhibits, for example a spectral response similar to spectral response <NUM> (<FIG>). A filter <NUM> is placed over green filter <NUM>, red filter <NUM> and blue filter <NUM> and over pixel <NUM> (i.e., the space between pixel <NUM> and filter <NUM> is clear demarked 'CLR' in <FIG>). Filter <NUM> exhibits, for example a spectral response similar to spectral response <NUM> (<FIG>).

A metal strip <NUM> is placed between the pixels corresponding to filters <NUM>, <NUM> and <NUM> and pixels <NUM>, <NUM> and <NUM>. An opaque section <NUM> is placed between filter <NUM> and filter <NUM> and an opaque section <NUM> is placed between filter <NUM> and filter <NUM>. A gap Wv1 exists between green filter <NUM> and red filter <NUM>, between green filter <NUM> and red filter <NUM>, between green filter <NUM> and red filter <NUM>. A gap Wv2 exists between red filter <NUM> and blue filter <NUM>, between red filter <NUM> and red blue <NUM> and between red filter <NUM> and blue filter <NUM>. Similar to as mentioned above gaps Wv1 and Wv2 prevents light received by one pixel to be received by an adjacent pixel. Also similar to as mentioned above, either one of gaps Wv1 and Wv2 may be replaced with a metal strip or an opaque material suitable to be fabricated on a substrate of a sensor such as sensor <NUM>. In the example brought forth above in <FIG> above, nine channels are achieved with only six filters. This reduced number of filters enables easier placement of filters, such as filters <NUM>, <NUM> and <NUM> (<FIG>) since these filters are larger in size (i.e., relative to a filter placed over a single pixel), allowing for larger placement tolerances. Furthermore, the larger size optionally enables passive placement of filters <NUM>, <NUM> and <NUM>.

Sensor <NUM> may be employed, for example, for acquiring spectral measurements in the visible spectral band as well as in the IR band. With reference to <FIG>, pixel <NUM> receives energy over spectral ranges ΔλR41, ΔλR42, ΔλR43 and ΔλR44. In the example brought forth, spectral ranges ΔλR41, ΔλR42, ΔλR43 are in the visible spectral band and spectral range ΔλR44 is in the IR band. The pixel corresponding to filter <NUM> receives energy in over spectral range ΔλR41 (i.e., filter <NUM> filters out spectral ranges ΔλR42, ΔλR43 and ΔλR44). The pixel corresponding to filter <NUM> receives energy in over spectral range ΔλR42 (i.e., filter <NUM> filters out spectral ranges ΔλR41, ΔλR43 and ΔλR44). The pixel corresponding to filter <NUM> receives energy in over spectral range ΔλR43 (i.e., filter <NUM> filters out spectral ranges ΔλR41, ΔλR42 and ΔλR44). The energy received over spectral range ΔλR44 is a function of the energy received by each of the pixels corresponding to filters <NUM>, <NUM> and <NUM> and the energy received by pixel <NUM>.

Similarly, pixel <NUM> receives energy over spectral ranges ΔλR51, ΔλR52, ΔλR53 and ΔλR54. Spectral ranges ΔλR51, ΔλR52, ΔλR53 are in the visible spectral band and spectral range ΔλR54 is in the IR band. The pixel corresponding to filter <NUM> receives energy in the spectral range ΔλR51 (i.e., filter <NUM> filters out spectral ranges ΔλR52, ΔλR53 and ΔλR54). The pixel corresponding to filter <NUM> receives energy in spectral range ΔλR52 (i.e., filter <NUM> filters out spectral ranges ΔλR51, ΔλR53 and ΔλR54). The pixel corresponding to filter <NUM> receives energy in spectral range ΔλR53 (i.e., filter <NUM> filters out spectral ranges ΔλR51, ΔλR52 and ΔλR54). The energy received over spectral range ΔλR54 is a function of the energy received by each of the pixels corresponding to filters <NUM>, <NUM> and <NUM> and the energy received by pixel <NUM>.

Further similarly, pixel <NUM> receives energy over spectral ranges ΔλR61, ΔλR62, ΔλR63 and ΔλR64. Spectral ranges ΔλR61, ΔλR62, ΔλR63 are in the visible spectral band and spectral range ΔλR64 is in the IR band. The pixel corresponding to filter <NUM> receives energy in spectral range ΔλR61 (i.e., filter <NUM> filters out spectral ranges ΔλR62, ΔλR63 and ΔλR64). The pixel corresponding to filter <NUM> receives energy in over spectral range ΔλR62 (i.e., filter <NUM> filters out spectral ranges ΔλR61, ΔλR63 and ΔλR64). The pixel corresponding to filter <NUM> receives energy in spectral range ΔλR63 (i.e., filter <NUM> filters out spectral ranges ΔλR61, ΔλR62 and ΔλR64). The energy received over spectral range ΔλR64 is determined as a function of the energy received by each of the pixels corresponding to filters <NUM>, <NUM> and <NUM> and the energy the received by pixel <NUM>. Thus sensor <NUM> acquires an image over all of spectral ranges Δλ<NUM>, Δλ<NUM>, Δλ<NUM>, Δλ<NUM>, Δλ<NUM>, Δλ<NUM>, Δλ<NUM>, Δλ<NUM>, Δλ<NUM>, Δλ<NUM>, Δλ<NUM> and Δλ<NUM>.

As mentioned above, the spectral responses of the filters should be designed according to design specifications and requirements. Such specification and requirements include, for example, overlapping of the transmittance spectral response between spectrally adjacent filters, the spectrum of the light illuminating the object, the inherent quantum efficiency (i.e., relative signal generated by light at each wavelength) of each pixel and the quantization resolution. Reference is now made to <FIG>, which are a schematic illustration of an example of the effects of overlap of the spectral sensitivity curves associated with spectrally adjacent filters as well as the effects of quantization, in accordance with a further embodiment of the disclosed technique. In <FIG>, the horizontal axis relates to wavelength (abbreviated λ in <FIG>) and the vertical axes relates to reflectance values. In the example brought forth in <FIG> the wavelengths are measured between <NUM>-<NUM> and reflectance is measured between <NUM> and <NUM>. Also in the example depicted in <FIG>, three channels (i.e., filters) are employed for spectral measurement. It is however, noted that spectral measurement systems may employ up to <NUM> channels and more. Depicted in <FIG> are two graphs, <NUM> and <NUM> each of a respective reflectance curve <NUM> and <NUM> of light to be measured. Reflectance curves <NUM> exhibits a rectangular shape with the reflectance values of <NUM> between the wavelengths <NUM>-<NUM>. Reflectance curve <NUM> exhibits the reflectance value of <NUM> between the wavelength <NUM> and <NUM> and the reflectance value of <NUM> between the wavelengths <NUM> and <NUM>. Reflectance curves <NUM> and <NUM> represent, for example, the reflectance values of light (e.g., resulting from illumination of the object), which first impinges on an object and then is reflected therefrom.

With reference to <FIG> depicts spectral sensitivity curves <NUM><NUM>, <NUM><NUM> and <NUM><NUM> and <FIG> depicts spectral sensitivity curves <NUM><NUM>, <NUM><NUM> and <NUM><NUM> respective of three filters. The term "spectral sensitivity curve" relates herein to a curve representing a function of the filter transmittance, the illumination, and quantum efficiency of the pixel collectively. Spectral sensitivity curves <NUM><NUM>, <NUM><NUM> and <NUM><NUM> do not overlap with each other. Spectral sensitivity curves <NUM><NUM>, <NUM><NUM> and <NUM><NUM> also do not overlap with each other. Spectral sensitivity curve <NUM><NUM>, <NUM><NUM>, <NUM><NUM>, <NUM><NUM>, <NUM><NUM> and <NUM><NUM> exhibit a value of <NUM>. Spectral sensitivity curve <NUM><NUM> is between wavelength <NUM> and <NUM> (i.e., completely within the reflectance curve <NUM>). Spectral sensitivity curve <NUM><NUM> is between wavelength <NUM> and <NUM> (i.e., Half of spectral sensitivity curve <NUM><NUM> overlaps with reflectance curve <NUM>). Spectral sensitivity curve <NUM>, is between wavelength <NUM> and <NUM> (i.e., mutually exclusive with reflectance curve <NUM>). In general, the value generated by each pixel covered with a filter is proportional to the area under the spectral sensitivity curve of the filter. Therefore, the values generated by pixels covered with filters exhibiting sensitivity curves such as sensitivity curves <NUM><NUM>, <NUM><NUM> and <NUM><NUM> and receiving light exhibiting reflectance curve <NUM> are [<NUM>, <NUM>, <NUM>].

Spectral sensitivity curve <NUM><NUM> is between wavelength <NUM> and <NUM>, spectral sensitivity curve <NUM><NUM> is between wavelength <NUM> and <NUM> and spectral sensitivity curve <NUM><NUM> is between wavelength <NUM> and <NUM> (i.e., mutually exclusive with reflectance curve <NUM>). However, since the value of reflectance curve <NUM> between wavelengths <NUM> and <NUM> is <NUM>, the value of the reflectance curve <NUM>, as would be determined by a filter exhibiting spectral sensitivity curve <NUM><NUM> would have been <NUM>. Therefore, the values generated by pixels covered with filters exhibiting sensitivity curves such as sensitivity curves <NUM><NUM>, <NUM><NUM> and <NUM><NUM> and receiving light exhibiting reflectance curve <NUM> are also [<NUM>, <NUM>, <NUM>]. Employing a <NUM>-bit quantization analog to digital conversion both system results in quantized values of [<NUM>, <NUM>, <NUM>] representing reflectance curve <NUM> as well as reflectance curve <NUM>. Thus, it would have been impossible to discern between reflectance curve <NUM> and reflectance curve <NUM> when employing filters which exhibit non-overlapping spectral sensitivity curves.

With reference to <FIG> depicts spectral sensitivity curves <NUM><NUM>, <NUM><NUM> and <NUM><NUM> and <FIG> depicts spectral sensitivity curves <NUM><NUM>, <NUM><NUM> and <NUM><NUM> respective of three filters. Spectral sensitivity curve <NUM><NUM> overlaps with each of spectral sensitivity curves <NUM><NUM> and <NUM><NUM>. Spectral sensitivity curves <NUM><NUM> and <NUM><NUM> cross at the Full Width Half Maximum (FWHM) points of the sensitivity curve curves. Spectral sensitivity curves <NUM><NUM> and <NUM><NUM> also cross at the FWHM points of the sensitivity curve curves. Similarly, spectral sensitivity curve <NUM><NUM> overlaps with each of spectral sensitivity curves <NUM>, and <NUM><NUM>. Spectral sensitivity curves <NUM><NUM> and <NUM><NUM> cross at the FWHM points of the sensitivity curve curves. Spectral sensitivity curves <NUM><NUM> and <NUM><NUM> also cross at the FWHM points of the sensitivity curve curves.

The values generated by pixels covered with filters exhibiting sensitivity curves such as sensitivity curves <NUM><NUM>, <NUM><NUM> and <NUM><NUM> and receiving light exhibiting reflectance curve <NUM> are [<NUM>, <NUM>, <NUM>]. As above, employing <NUM>-bit quantization analog to digital conversion will result in quantized values of [<NUM>, <NUM>, <NUM>] representing reflectance curve <NUM>. However, the values generated by pixels covered with filters exhibiting sensitivity curves such as sensitivity curves <NUM><NUM>, <NUM><NUM> and <NUM><NUM> and receiving light exhibiting reflectance curve <NUM> are [<NUM>, <NUM>, <NUM>] representing reflectance curve <NUM>. Employing <NUM>-bit quantization analog to digital conversion will result in quantized values of [<NUM>, <NUM>, <NUM>]. The differences between the quantized pixel values of reflectance curve <NUM> and reflectance curve <NUM> is enough to sufficiently discern therebetween even is with an increase in the system noise.

With reference to <FIG>, <FIG> depicts spectral sensitivity curves <NUM><NUM>, <NUM><NUM> and <NUM><NUM> and <FIG> depicts spectral sensitivity curves <NUM><NUM>, <NUM><NUM> and <NUM><NUM> respective of three filters. Spectral sensitivity curve <NUM><NUM> overlaps with each of spectral sensitivity curves <NUM><NUM> and <NUM><NUM>. Spectral sensitivity curves <NUM><NUM> and <NUM><NUM> cross at point lower than the FWHM point. Spectral sensitivity curves <NUM><NUM> and <NUM><NUM> also cross at point lower than the FWHM point. Similarly, spectral sensitivity curve <NUM><NUM> overlaps with each of spectral sensitivity curves <NUM>, and <NUM><NUM>. Spectral sensitivity curves <NUM><NUM> and <NUM><NUM> cross at points lower than the FWHM points of the sensitivity curve curves. Spectral sensitivity curves <NUM><NUM> and <NUM><NUM> also cross at points lower than the FWHM points of the sensitivity curve curves.

The values generated by pixels covered with filters exhibiting sensitivity curves such as sensitivity curves <NUM><NUM>, <NUM><NUM> and <NUM><NUM> and receiving light exhibiting reflectance curve <NUM> are [<NUM>, <NUM>, <NUM>]. As above, employing <NUM>-bit quantization analog to digital conversion will result in quantized values of [<NUM>, <NUM>, <NUM>] representing reflectance curve <NUM>. However, the values generated by pixels covered with filters exhibiting sensitivity curves such as sensitivity curves <NUM><NUM>, <NUM><NUM> and <NUM><NUM> and receiving light exhibiting reflectance curve <NUM> are [<NUM>, <NUM>, <NUM>] representing reflectance curve <NUM>. Employing <NUM>-bit quantization analog to digital conversion will result in quantized values of [<NUM>, <NUM>, <NUM>]. Although the differences between the quantized pixel values of reflectance curve <NUM> and reflectance curve <NUM> is enough to sufficiently discern therebetween any increase in noise may render these two curves indiscernible. Increasing the quantization resolution (e.g., <NUM>-bit, <NUM>-bit etc.) shall result in a larger difference between the quantized values of reflectance curves <NUM> and reflectance curve <NUM>.

The description hereinabove in conjunction with <FIG> exemplified the tradeoff between the overlap between overlap of filter spectral sensitivity curves and quantization resolution, as well robustness to noise. Such tradeoffs and affects should be considered during the design of a color measurement system. Nonetheless, the design of overlapping filters results in better spectral coverage (i.e., relative to non-overlapping filters, when employed with various mathematical linear combinations of responses).

As mentioned above, a combined spectral measurement and imaging line-scan sensor according to the disclosed technique may be employed in a line scan camera. Such combined imaging and spectral measurement line-scan cameras may be employed in a printing press for either image acquisition, color measurement & control or inspection functionality. Reference is now made to <FIG>, which is a schematic illustration of a combined imaging and spectral measurement line-scan camera, generally referenced <NUM>, employed for viewing, inspecting and for measuring and/or controlling the color of an image <NUM> printed on a web <NUM>, constructed and operative in accordance with an embodiment of the claimed invention. Camera <NUM> employs a combined imaging and spectral measurement line-scan sensor <NUM>. Sensor <NUM> may be similar to any one of the above described sensors <NUM> (<FIG>), <NUM> (<FIG>), <NUM> (<FIG>), <NUM> (<FIG>) and <NUM> (<FIG>). Camera <NUM> is employed in a combined inspection and color control system for printing presses, which further includes a processor <NUM> coupled with line-scan camera <NUM>. In the exemplary scenario depicted in <FIG>, a printing press <NUM> prints an image <NUM> on a web <NUM>. Printing press <NUM> further prints, for example, six color targets <NUM><NUM>-<NUM><NUM> employed for color control. It is noted that in <FIG>, color targets <NUM><NUM>-<NUM><NUM> are depicted as being printed on the margins of image <NUM>. However, color targets <NUM><NUM>-<NUM><NUM> may alternatively be printed in the image or constitute a part of the printed image. In other words, regions within the image are designated for color control purposes.

Typically, the size of color targets <NUM><NUM>-<NUM><NUM> are on the order of several millimeters square (e.g., <NUM> millimeters by <NUM> millimeters). Typically, the size of a magnified pixel (i.e., the size of a pixel in the field of view on the web) is on the order of tens to hundreds of micrometers. Thus, with reference to the example brought forth in <FIG>, <FIG> and <FIG>, each spectral measurement of a single target is acquired by a group of pixels in the spectral measurement lines (e.g., lines <NUM><NUM>, <NUM><NUM> and <NUM><NUM> - <FIG>, lines <NUM><NUM> and <NUM><NUM> - <FIG>, lines <NUM><NUM> and <NUM><NUM> - <FIG>). However, the pixels acquiring the spectral measurement of a single target may not necessarily be from the same group of pixels (i.e., the groups that are depicted in <FIG>, <FIG> and <FIG>). Rather, some of the spectral bands may be acquired by pixels from one group and the other spectral bands may be acquired by pixels from an adjacent group. For example, with reference to <FIG>, spectral bands <NUM>-<NUM> in line <NUM><NUM> may be acquired by pixels from the fourth group and spectral bands <NUM>-<NUM> may be acquired by pixels from the fifth group. As a similar example, with reference to <FIG>, spectral bands <NUM>-<NUM> may be acquire by pixels from the third group and spectral bands <NUM>-<NUM> may be acquired by pixels from the fourth group.

During the print run, image <NUM> and color targets <NUM><NUM>-<NUM><NUM> pass in front of camera <NUM> and camera <NUM> acquires a plurality of combined line images and spectral measurement. Camera <NUM> provides these combined line images and spectral measurement to processor <NUM>. Processor <NUM> renders a two dimensional image (e.g., an RGB image) of the entire substrate width from images acquired by the imaging lines of sensor <NUM>. Processor <NUM> may employ this two dimensional image to locate color targets <NUM><NUM>-<NUM><NUM> in the image. Processor <NUM> then employs the location of color targets <NUM><NUM>-<NUM><NUM> in the two dimensional image to determine the spectral measurement information associated with each of color targets <NUM><NUM>-<NUM><NUM> from the corresponding pixels or groups of pixels in the spectral measurement lines of sensor <NUM>. In essence, the spectral measurement information provides the spectral response of each of color targets <NUM><NUM>-<NUM><NUM>. Accordingly, processor <NUM> may determine the color associated with each of color targets <NUM><NUM>-<NUM><NUM> in a selected color space (e.g., CIEL*a*b*, CIEL*u*v* and the like). The processor <NUM> may employ the two dimensional image to determine further press parameters such as pressure.

Claim 1:
A line-scan sensor (<NUM>) for combined imaging and spectral measurements, integrated on a single semiconductor substrate, said sensor including:
a plurality of pixel lines, each pixel line including a plurality of pixels, at least one of said pixel lines being an imaging line (<NUM>, <NUM>, <NUM><NUM>, <NUM><NUM>) designated for acquiring at least one image of an object and at least one of said pixel lines, different from said at least one imaging line, being a spectral measurement line (<NUM><NUM>, <NUM><NUM>), designated for acquiring a spectral measurement of light received from said object,
each imaging line (<NUM>, <NUM>, <NUM><NUM>, <NUM><NUM>) being associated with a single respective spectral response within a spectral range,
each pixel in each spectral measurement line (<NUM><NUM>, <NUM><NUM>) being associated with a respective pixel spectral band,
each of at least three pixels in each of said spectral measurement lines (<NUM><NUM>, <NUM><NUM>) being respectively associated with different respective pixel spectral bands, said different respective pixel spectral bands being non-identical to any one of said single spectral responses associated with each said imaging lines,
wherein said at least one of pixel lines being said spectral measurement line (<NUM><NUM>, <NUM><NUM>) includes two spectral measurement lines, and
wherein each two horizontally adjacent groups of four pixels (<NUM><NUM>-<NUM>n) in the two spectral measurement lines are separated by two vertically adjacent pixels (<NUM><NUM>-<NUM>n-<NUM>), said two vertically adjacent pixels (<NUM><NUM>-<NUM>n-<NUM>) are covered with an opaque material.