WO2011063939A1

WO2011063939A1 - Image acquisition device, image-generating device and spectroscope for spatially resolved spectroscopy

Info

Publication number: WO2011063939A1
Application number: PCT/EP2010/007109
Authority: WO
Inventors: Albrecht Geist; Eberhard Derndinger
Original assignee: Carl Zeiss Ag
Priority date: 2009-11-27
Filing date: 2010-11-24
Publication date: 2011-06-03
Also published as: DE102009056178A1

Abstract

The invention relates to an image acquisition device for the digital acquisition of a two-dimensional colour image comprising a plurality of light-sensitive sensor pixels (26) and a plurality of juxtaposed colour splitter elements (24), wherein at least two sensor pixels (26) are assigned to each colour splitter element (24). Furthermore, each colour splitter element (24) is designed such that it distributes polychromatic light (34) impinging thereon to the sensor pixels (26) assigned thereto at a distribution ratio that is dependent on the spectral composition of the impinging light. According to the invention, the colour splitter elements (24) are arranged in a two-dimensional pattern.

Description

PICTORIAL PICTURES, PICTURE PRODUCTION DEVICE

AND SPECTROSCOPE FOR LOCATED SPECTROSCOPY

BACKGROUND OF THE INVENTION

1. Field of the invention

The invention relates to an image sensor (also called an image sensor) for the digital recording of a two-dimensional color image, an imaging device for reproducing a two-dimensional color image and a spectroscope for two-dimensionally spatially resolved spectroscopy.

2. Description of the Related Art

Imagers for the digital recording of a two-dimensional) len color image, as they are often used in photo or video cameras, usually have a matrix-like arrangement of photosensitive sensor pixels. The sensor pixels are provided with a color filter which is only for light of a spectral component, z. B. red, green or blue light, are permeable 15. If, for example, incident light contains a green spectral component and strikes this light on a sensor pixel whose color filter is transparent to green light, the sensor pixel generates an electrical output signal that depends on the intensity of the green spectral component. A 20 evaluation of the image sensor determines the color information of the image to be recorded from the output signals of all sensor pixels provided with color filters.

However, a disadvantage of this known type of imagers is that most of the light incident on the sensor pixels is absorbed by the color filters. Therefore, such image sensors have a relatively low photosensitivity.

CONFIRMATION COPY A higher photosensitivity have image sensors in which not all, but only a part of the sensor pixels is provided with color filters. The remaining sensor pixels detect the intensity of the incident light color independently, ie for all wavelengths within the visible spectrum. However, the gain in photosensitivity is paid for in this variant with a loss of color information.

Extensive use of the incident light is possible with imagers in which the incident light is distributed to a plurality (usually three) of imagers using a dichroic prism or other color divider, which detect the intensity of the light incident on them in a wavelength independent manner. However, such image sensors require significantly more construction space, require a high adjustment effort and are therefore relatively expensive.

From EP 0 383 308 A2 an image sensor for use in scanners according to the preamble of claim 1 is known, wherein the color divider elements, which are arranged along a single line and designed as diffractive optical elements, the incident polychromatic light on three lines from sensor pixels. The color divider elements are in this case arranged in the vicinity of an image plane of an imaging optical unit, in which an image of the illuminated scanner slot is formed. The division onto the color pixel associated sensor pixels takes place along the scan direction. Since no absorbing color filters are used, this known scanner is very sensitive to light.

In order to be able to record a two-dimensional color image with this known scanner, it must be scanned line by line. However, only a small fraction of the total available amount of light is always utilized at a given time, which ultimately even more light is lost than in the image recorder described above with color filters.

Similar scanners with color divider elements, which are designed as diffractive optical elements, are known from US Pat

5,233,703 and US 5,481,381.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a particularly light-sensitive image recorder for the digital recording of a two-dimensional color image. According to the invention, this object is achieved by an image sensor having a plurality of photosensitive sensor pixels and a plurality of color divider elements arranged next to one another. Each color divider element is assigned at least two sensor pixels. Furthermore, each color divider element is designed in such a way that it distributes incident polychromatic light onto its associated sensor pixels with a distribution ratio that depends on the spectral composition of the incident light. According to the invention, the color divider elements are arranged in a two-dimensional pattern. The inventors have realized that it is possible to realize a highly photosensitive imager when a plurality of small color divider elements are arranged in a two-dimensional pattern in or in the immediate vicinity of a recording plane in which the two-dimensional color image is to be recorded. Each color divider element spectrally dissects the incident light and distributes the spectral components to its assigned sensor pixels. Since the spectral decomposition of the incident colored light is largely lossless with the aid of diffractive or refractive optical elements, virtually no light is lost in the determination of the color information. Therefore, the imager according to the invention has a very high photosensitivity. Where sensor pixels usually provided with color filters are arranged, according to the invention there are color divider elements which spectrally dissect the incident light and direct it to the sensor pixels. Since the color divider elements are arranged not in a single line, but in a two-dimensional pattern, the color image does not have to be scanned, so that the image sensor is also suitable for video cameras, for example.

In this case, a two-dimensional pattern is understood to mean that at least one color divider element in a first direction and one color divider element in a second direction orthogonal thereto are adjacent to each color divider element to which at least two sensor pixels are assigned. The pattern will generally be regular and may in particular have rows and columns. However, there are also irregular or varying over its area varying patterns into consideration. The entire pattern of color filter elements preferably covers an area whose aspect ratio is less than 5: 1. As already mentioned, the color splitter elements are preferably arranged in a recording plane in which the color image is to be recorded and which can coincide with an image plane of a preceding imaging optics. However, it is also possible to arrange the color splitter elements axially offset from the object axially to such a recording plane, in order then - but at the expense of lower image sharpness - to exploit that the light beams emanating from the color splitter elements converge and thus more easily onto the sensor pixels can be directed. In general, the color divider elements will be designed to divert different spectral components of the incident polychromatic light in different directions, as in diffractive ones, for example optical elements or prisms is the case. In principle, however, it is also considered that the color divider elements make a division of the different spectral components in a different way. For example, the wavelength dependence of certain birefringent elements could be used to code the color information in the polarization state. At another, possibly even further away, the light could be distributed to the associated sensor pixels with the aid of polarization-selective optical elements. Particularly suitable as color-splitter elements are diffractive optical elements. Preferably, the zeroth diffraction order is suppressed and only the first diffraction order is used. For this purpose, the diffractive optical elements can have blazed diffraction structures. When used in transmission diffractive optical elements, the first diffraction order is always emitted obliquely. To compensate for this offset of the deflection angle, the diffractive structures may be carried by a wedge-shaped prism so that light of a certain wavelength can pass through the color-splitter element without deflection.

Instead of diffractive optical elements and refractive optical elements, in particular prisms or arrangements of multiple prisms can be used as a color divider elements. In this case, the use of a straight-line prism is particularly preferred, since this too has the property that light of a certain wavelength can pass through the straight-viewing prism without deflection.

In one embodiment of the invention, each color divider element is associated with a collection optical collection element located between the color divider element and the sensor pixels so as to be exposed to all light rays from the respective color divider element to that color divider element assigned sensor pixels be directed. Such an optical collection element, in which it is z. B. can be a lens or an achromatisiertes diffractive optical element, can be used to focus the incident light and to direct to the sensor pixels that light of a wavelength falls only on at most one sensor pixel. This effect can be achieved even if the color divider elements themselves have a collecting effect.

However, extraction of color information is also possible if the color-splitter elements are designed and arranged relative to the sensor pixels such that light of one wavelength falls on at least two sensor pixels assigned to the same color splitter element. If the distribution ratio for the respective wavelength between the at least two sensor pixels is known, its spectral components can be determined even when polychromatic light strikes. Any ambiguities that may be present may be resolved by considering the output signals generated by sensor pixels associated with a neighboring color divider element. Allowing the light of one wavelength to coincide with multiple sensor pixels simultaneously also reduces the need to provide additional collection optical elements that focus the deflected light and direct them to individual sensor pixels.

Further simplifications are possible if at least one, but not all pixels assigned to a color divider element are additionally assigned to an adjacent color divider element. In this case, neighboring color divider elements share sensor pixels, so that their

Number can be significantly reduced. Although inevitably accompanied by a loss of resolution, but this can with the help of known interpolation algorithms, as they were developed for the frequently used Bayer pattern, can be partially compensated.

If at least one sensor pixel is associated with adjacent color divider elements, then there must be at least one wavelength at which the color divider elements deflect light from the same direction of at least one wavelength in a direction that is different for the two color divider elements , In general, this will cause adjacent color divider elements to be pairwise different. It is preferred in this context if the different directions are mirror-symmetrical with respect to a plane of symmetry which extends between the two color-splitter elements.

If the adjacent color divider elements are diffractive optical elements with diffractive structures which are supported by wedge-shaped prisms, then, in the case of adjacent color divider elements to which at least one sensor pixel is assigned in common, the wedge-shaped prisms have alternating wedge angles. In another embodiment, each color divider element is associated with a first, a second and a third sensor pixel. The first sensor pixel is additionally assigned to a color divider element adjacent to one side, and the second sensor pixel is additionally assigned to a color divider element adjacent to another side. In this case, it is preferable that the light incident on the third sensor pixel have wavelengths that are on average between the wavelengths of the light incident on the first and second sensor pixels. In general, this will be light in the green spectral range.

In a further embodiment, each sensor pixel is associated with an optical element having a collecting or dissipating effect, that between the color divider element and the sensor pixels are arranged to be exposed only to the light rays directed by the respective color divider element onto a single associated sensor pixel. The optical element with a collecting or scattering effect has the task of individually bundling or dispersing the light incident on the sensor pixels and thus achieving an adaptation to the size of the photosensitive surface of the sensor pixel and the numerical aperture, in which maximum sensitivity is achieved. In particular, it can be achieved that no or less light falls into interspaces between the sensor pixels.

In another embodiment, disposed between each color divider element and the sensor pixels is a refractive ray displacement element associated with the color divider element which alters the split ratio at which the color divider element disperses polychromatic light incident thereon to the pixels associated therewith and the parallel optical surfaces having. With the aid of such a beam displacement element, the distribution ratio can be changed in such a way that an optimal adaptation to the spectral sensitivity of the suppository of the human eye responsible for color perception is achieved. The optical surfaces of the beam displacement element may be kinked or curved.

The image recorder may have evaluation electronics which are designed such that they combine output signals of the sensor pixels associated with a color divider element with spectral sensitivity functions and derive color values from them.

The invention further relates to a digital camera with an imaging optical system, with which an object can be imaged on an image plane, and with an image recorder according to the invention. Preferably, the color divider elements are then arranged in or in the immediate vicinity of an image plane of the imaging optics, as already mentioned above.

It is furthermore preferred if the imaging optics is telecentric at least on the image side. In this way, it is ensured that the incident on the color divider elements bundles of light with vertical principal ray pass through the image plane, which facilitates the design of the color divider elements. It is furthermore preferred if the imaging optics have a double-sided numerical aperture of less than 0.1 and preferably less than 0.05. Such a small numerical aperture is convenient because most eligible color-splitter elements additionally distract the spectrally dispersed light as the direction of incidence of the incident

Light changed. This incident directions change only slightly, as is the case with small image side numerical apertures of the imaging optics, as is the loss of color information, which results from the additional distraction ^'as a result of varying the angle of incidence is low.

The invention can conversely also be used for imaging devices for the reproduction of color images, which essentially requires only an inversion of the light propagation direction. An image generating device according to the invention has a plurality of switchable light pixels and a plurality of overlay elements arranged next to one another. Each overlay element is associated with at least two light pixels that produce light of different colors. Furthermore, the overlay elements are arranged in a two-dimensional pattern, wherein each overlay element is designed such that it overlays the light, which strikes from different directions with different colors, to form a common beam. Each overlay element may be associated with a gathering optical collection element located between the overlay element and the light pixels such that it is exposed to all light rays directed from the light pixels to the associated overlay element.

Furthermore, the overlay elements can be configured and arranged relative to the light pixels such that light of a wavelength of at least two light pixels is generated and falls on the overlay element associated therewith.

At least one, but not all, luminous pixels associated with an overlay element can additionally be assigned to an adjacent overlay element.

In this case, adjacent heterodyne elements can deflect light which is incident with the same wavelength from one direction, which is different for the two adjacent heterodyne elements, in the same direction. The different directions of the incident light are preferably mirror-symmetrical with respect to a symmetry plane extending between the two overlay elements.

Each overlay element can be assigned a first, a second and a third light pixel, wherein the first light pixel is additionally assigned to an overlay element adjacent to one side and the second light pixel is additionally assigned to an overlay element adjacent to another side.

In this case, light generated by the third light-emitting pixel preferably has wavelengths that lie, on average, between the wavelengths of light generated by the first and second light-emitting pixels. Each light-emitting pixel may be associated with an optical element having a collecting or dispersing effect, which is arranged between the superposition element and the light-emitting pixels such that it is only exposed to the light rays generated by a single light-emitting pixel.

At least one overlay element may comprise a diffractive optical element. Preferably, the overlay element then has a wedge-shaped prism with diffractive structures carried therefrom. In adjacent overlay elements to which at least one luminous pixel is assigned in common, the wedge-shaped prisms may have alternating wedge angles.

At least one overlay element may comprise a refractive optical element, in particular a prism and more particularly a straight-line prism.

Each light pixel may include a diffractive optical element and a light switch. The light switch may be, for example, a switchable LCD element or a tiltable mirror. The invention also relates to a digital image projector with an imaging optical system, with which an object can be imaged onto an image plane, and with an image generation device according to the invention.

The overlay elements are preferably arranged in an image plane of the imaging optics, which can be telecentric at least on the object side and has an object-side numerical aperture of less than 0.1 and more preferably less than 0.05.

The invention also relates to a spectroscope for spatially resolved spectroscopy with a plurality of photosensitive sensor pixels and a plurality of juxtaposed Color separator elements. Each color divider element is associated with at least four sensor pixels. Further, each color divider element is configured to distribute polychromatic light incident thereon to its associated sensor pixels at a split ratio that depends on the spectral composition of the incident light. According to the invention, the color divider elements are arranged in a two-dimensional pattern.

BRIEF DESCRIPTION OF THE DRAWINGS Further features and advantages of the invention will become apparent from the following description of an embodiment with reference to the drawings. Show:

1 shows a color camera according to the invention according to a first

Exemplary embodiment in a simplified meridional section;

Figure 2 is an enlarged detail of an image pick-up which is part of the color camera shown in Figure 1;

Figure 3 is a plan view of that shown in FIG

imagers;

FIG. 4 shows a color camera according to the invention according to a second exemplary embodiment of the invention in a simplified meridional section;

FIG. 5 shows an enlarged detail of an image recorder, which is part of the color camera shown in FIG. 4, with a beam path for light with a wavelength in the red spectral component;

FIG. 6 shows a representation as in FIG. 5, but for

Light with a wavelength in the blue spectral range; Figure 7 is a representation as in Figure 5, but for

Light with a wavelength in the green spectral component;

Figure 8 is a plan view of the image sensor in the

Figure 4 shown color camera;

9 shows an enlarged detail of an image sensor for the color camera shown in FIG. 4 according to a first embodiment variant;

FIG. 10 shows an enlarged detail of an image recorder for the color camera shown in FIG. 4 according to a second embodiment variant;

Figure 11 is a side sectional view of an imager, are used in the color divider elements diffractive optical elements; FIGS. 12a and 12b show a detail of the image sensor shown in FIG. 6 with a beam path for vertical or oblique incidence of light;

FIG. 13 shows a side view of an image recorder in which straight-viewing prisms are used as color divider elements;

Figure 14 is an enlarged view of two adjacent

Straight-ahead prisms with marked beam path;

FIG. 15 shows an imaging device according to the invention

according to a first embodiment of the invention in a simplified meridional section;

FIG. 16 shows an imaging device according to the invention

according to a second embodiment of the invention in a simplified meridional section; FIG. 17 shows a spectroscope according to the invention for spatially resolved spectroscopy in a simplified meridional section.

DESCRIPTION OF PREFERRED EMBODIMENTS

I. Color camera

1. First embodiment

FIG. 1 shows a color camera according to the invention designated overall by 10 in a meridional section shown schematically. The color camera 10 has a housing 12 which accommodates an imaging optics 14 and an image recorder 16. The imaging optics 14 forms an object indicated at 18, which is located in an object plane 20 of the imaging optics 14, in an image plane 22 of the imaging optics 14. In Figure 1, the imaging optics 14 is simplified as a single converging lens indicated; Of course, the imaging optics 14 may also include multiple lenses and other optical elements.

The image plane 22 of the imaging optics 14 coincides with a recording plane of the image recorder 16 in which it receives the image of the object 18 generated by the imaging optics 14; In the following, therefore, the same reference numeral 22 is used for the image plane and the recording plane. In the receiving plane 22, a plurality of color divider elements 24 are arranged in a two-dimensional regular pattern. The area covered by the color divider elements 24 in the receiving plane 22 has an aspect ratio of at most 5: 1 and determines the maximum size of the image that can be picked up by the imager 16.

The color divider elements 24 have the task of spectral polychromatic light emanating from the object 18 and incident in the receiving plane 22 on the color divider elements 24 to disassemble and distribute the various spectral components on sensor pixels 26, which are arranged on a carrier 28. The sensor pixels 26 detect the intensity of the incident light as far as possible independently of the wavelength and produce intensity-dependent electrical output signals. These output signals are fed to evaluation electronics 30 of the image recorder 16, which calculates therefrom color values for the individual color divider elements 24, for example in an RGB color space. These color values may then be stored in a memory 32 of the imager 16.

The spectral decomposition of the polychromatic light with the aid of the color divider elements 24 will be explained in more detail below with reference to FIG. 2, which shows an enlarged detail of a part of the image sensor 16 shown in FIG.

The color divider elements 24 are configured to divert different spectral components of the incident colored light 34 in different directions. For the sake of simplicity, it is first assumed here that incident polychromatic light 34 is collimated and impinges perpendicularly on the color divider elements 24. If these deflect the spectral components of the incident light 34 in different directions, without influencing the parallelism of the light per se, emerge from exit surfaces of the color divider elements 24 collimated beams whose propagation direction depends on the wavelength.

In the illustrated embodiment, the imager 16 includes a matrix-like array of converging lenses 36 mounted between the color divider elements 24 and the sensor pixels 26. Each color divider element 24 is associated with a converging lens 36, wherein the distance between the color divider elements 24 and the converging lenses 36 is so small, that the entire light passing through a color divider element 24 also passes through the respectively assigned converging lens 36.

In the exemplary embodiment illustrated here, each color divider element 24 is assigned three sensor pixels 26, specifically a first sensor pixel 26a for the blue spectral component, a second sensor pixel 26b for the green spectral component and a third sensor pixel 26c for the red spectral component. The sensor pixels 26 are arranged at least approximately in a focal plane of the converging lenses 36, so that they focus the collimated, but in different directions propagating beams on the sensor pixels 26, as shown in Figures 1 and 2 for three different wavelengths in the blue, green and red spectral component is indicated by dotted, solid or dashed lines. The converging lens 36 sets the different

Propagation directions of the individual wavelengths in places to where the blue, green and red spectral component associated sensor pixels 26a, 26b and 26c are located.

By evaluating the output signals of the sensor pixels 26a, 26b, 26c assigned to a color divider element 24, the evaluation electronics 30 can determine how much light in the blue, green and red spectral range impinges on the color divider element 24, and from this a color value for the impinging Derive light. Each color divider element 24 thus represents a pixel that can be resolved in the acquisition plane 22. The size and density of the color divider elements 24 thus determines the resolution of the imager 16.

As a rule, the color divider elements 24 generate a continuous spectrum over at least a relatively large wavelength range so that light also falls into intermediate spaces between the sensor pixels 26a, 26b and 26c. This light is lost for evaluation by the imager 16, why the spaces between the sensor pixels 26a, 26b, 26c should be as small as possible.

FIG. 3 shows a section of the image sensor 16 in plan view. The color divider elements 24 indicated by thick black lines cover in each case a converging lens 36 and three sensor pixels 26a, 26b, 26c. In this embodiment, each pixel to which a color divider element 24, a condenser lens 36, and three sensor pixels 26a, 26b, 26c are assigned are constructed identically. Depending on the structure of the color divider elements 24 to be explained, it is therefore even possible to combine a plurality of color divider elements 24 to form larger components and to divide them only in a functional respect via the assignment to the sensor pixels 26. In FIG. 3, such a possible summary of several color divider elements is indicated by dashed lines, which are merely intended to indicate a functional separation of the adjacent color divider elements.

To the right of FIG. 3, two alternative arrangements of sensor pixels 26 and lenses 36 are shown. In the exemplary embodiment shown on the top right, the sensor pixels 26 have a hexagonal base surface, so that they can be arranged on the carrier 28 with minimal spacings and, with reference to a group of three sensor pixels 26a, 26b, 26c, associated with a color divider element 24 , The associated color divider element must in this case be designed such that it is able to deflect the different spectral components not only in one plane, but in two orthogonal planes. In the variant shown at the bottom right in FIG. 3, the rotationally symmetrical lens 36 is replaced by a cylindrical lens 136, which thus has refractive power only along one direction. Perpendicular to this direction extend the sensor pixels 126 across the entire dimension of the associated color divider element 126.

With approximately lossless color divider elements 24, the image sensor 16 according to the exemplary embodiment illustrated in FIGS. 1 to 3 makes it possible to supply almost 100% of the light incident in the recording plane 22 to the sensor pixels 26. Therefore, the imager 16 of the color camera 10 has a very high luminous efficacy. The color camera 10 can therefore achieve excellent color resolutions even in unfavorable lighting conditions.

2. Second embodiment

FIG. 4 shows, in a representation similar to FIG. 1, a color camera according to the invention designated overall by 10 'according to a second exemplary embodiment. The same or corresponding components are identified by the same reference numerals.

In contrast to the color camera 10 shown in FIGS. 1 to 3, no converging lenses 36 are provided in the image sensor 16 of the color camera 10 'which focus the spectral components of the incident light deflected by the color elements 24 onto the individual sensor pixels 26.

Rather, it is deliberately allowed in this embodiment that each color divider element 24 directs light of any wavelength not only to a single sensor pixel 26, but also to the two adjacent sensor pixels. Thus, in FIG. 4 light from a color divider element 24a of a wavelength that is not deflected hits not only one sensor pixel 26b but also some of the neighboring sensor pixels 26a and 26c. The same applies to a light beam with a shorter wavelength, which is indicated by dotted lines, and for a light beam with a longer wavelength, which is indicated by dashed lines. Thus, in the embodiment illustrated in FIGS. 1 to 3, while the distribution ratio for a specific wavelength was 0: 0: 1, 0: 1: 0 or 1: 0: 0, the division ratio is in the exemplary embodiment shown in FIG a: b: c, with a, b, c 0. The distribution ratio will be slightly different for each wavelength. For the wavelengths shown in FIG. 4, which are approximately in the middle of the blue, green and red spectral components, the distribution ratio can be, for example, 2: 1: 1, 1: 2: 1 and 1: 1: 2, respectively much light falls on the spectrally "correct" sensor pixel as on the two "wrong" sensor pixels.

The distribution ratio depends in particular on the structure of the color divider elements 24, but also on the arrangement of the sensor pixels 26. If the distribution ratio is known for all wavelengths, the evaluation electronics 30 can calculate the color values from the electrical output signals generated by the sensor pixels 26 using algorithms known per se. The operation is so far not unlike that of the human eye, in which the responsible for the color sensation suppositories are also sensitive to all wavelengths and the color information results only from the differences in sensitivity for a particular wavelength. However, such a determination of the color values is only possible if the distribution ratio is not 1: 1: 1 for all wavelengths, ie light of a certain wavelength falls in equal parts on three adjacent sensor pixels. For the dimensions of the sensor pixels 26, this means, in particular, that their width may not be one third of the width of a beam splitter element 24, which in turn approximately corresponds to the cross section of the output from the color divider elements 26 light beam of a particular wavelength. In the first embodiment described above, the width was the sensor pixel is smaller than this value; However, if the widths should be greater than this value, then each beam splitter element 26 can not be clearly assigned to three different sensor pixels 26a, 26b, 26c.

Rather, several (but not all) of a color divider element 24 associated sensor pixels 26 must be additionally assigned to an adjacent color divider element, as shown in FIG 4 can be removed. In turn, this double assignment requires that adjacent color divider elements 24 need not deflect incident light of the same wavelength in the same direction but in different directions.

This will be explained below with reference to FIGS. 5 to 7, which show an enlarged section from FIG. 4. Shown are two adjacent color divider elements 24a, 24b, 24c and sensor pixels 26, which are marked for better distinctness with the first letters of the primary colors red, green and blue.

FIG. 5 shows how light of a wavelength in the red spectral component is deflected by the color divider elements 24. The deflection takes place in such a way that this light falls primarily on the sensor pixel 26 associated with the red spectral color, which are designated by the lower case letter r. As can be seen in FIG. 5, adjacent color divider elements 24 in each case deflect light of this wavelength in opposite directions. The directions in which the light of this wavelength is deflected by adjacent color divider elements, are mirror-symmetrical with respect to a plane of symmetry extending between the respective adjacent color divider elements. Since the number of sensor pixels 26 assigned to the red spectral component is only half as large as the number of color divider elements 24, pairs of adjacent color divider elements must each share a sensor pixel 26 for the spectral component red. Since this sensor pixel 26 can not distinguish which color divider If this light is directed towards it, this means that the resolution for the wavelength in the red spectral range shown in FIG. 5 is smaller by a factor of 1/2 than the resolution that results arithmetically from the number of color divider elements 24.

FIG. 6 shows in a representation similar to FIG. 5 the conditions for light whose wavelength lies in the blue spectral component. The explanations explained above with reference to FIG. 5 apply accordingly here. FIG. 7 shows, in a representation likewise similar to FIG. 5, a special case in which light with a wavelength of the green spectral component strikes the sensor pixels 26 without being deflected by the color divider elements 24. Light of this wavelength does not overlap with light of the same wavelength that has passed through an adjacent color divider element. Consequently, at this wavelength, each sensor pixel g for the spectral component is assigned in green exactly to a color divider element 24. Thus, compared to red or blue light, this resolution achieves twice the resolution given by the number of color divider elements 24.

In general, the light has a wavelength that is between the wavelengths whose distribution is shown on the sensor pixels 26 in Figs. 5-7. For these wavelengths, the resolution is computationally between the minimum resolution shown in Figures 5 and 6 and the maximum resolution shown in Figure 7.

FIG. 8 shows the image recorder 16 of the color camera 10 'in a plan view. In the upper third, different hatchings indicate that the adjacent ones are in each case

Color divider elements 24 incident light of the same wavelength (apart from the special case of undeflected light shown in Figure 7) in different Rieh- deflected as shown in Figures 5 and 6. In the middle third of Figure 8, the hatching is omitted in order to understand the arrangement of the color divider elements 24 relative to the underlying detectable sensor pixels 26 can; in the lower third of the color divider elements 24 are not shown.

As already mentioned, the sensor pixels 26 in this exemplary embodiment form an arrangement in which the sensor pixels labeled with the letter g appear twice as often for the green spectral component as the sensor pixels labeled with the letters r and b corresponding to the red and the blue spectral component are assigned. This imbalance of the individual spectral components takes into account the higher sensitivity of the human eye to green light and is therefore also realized in conventional imagers in which the individual photosensitive sensor pixels are provided with color filters and arranged in the Bayer pattern.

Similar to the Bayer pattern, in the arrangement of the sensor pixels 26 shown in FIG. 8, color values for positions between sensor pixels 26 which are assigned to a specific spectral component can be interpolated.

With approximately lossless color divider elements 24, the image sensor 16 according to the exemplary embodiment illustrated in FIGS. 4 to 8 makes it possible to supply almost 100% of the light incident in the recording plane 22 to the sensor pixels 26. Therefore, the imager 16 of the color camera 10 'also has a very high luminous efficacy. The color camera 10 'can therefore still achieve excellent color resolutions even in unfavorable lighting conditions. However, the structural design is even simpler than in the case of the color camera 10 according to the first embodiment shown in FIGS. 1 to 3, since the arrangement of converging lenses 34 is omitted. In addition, assuming minimum size the sensor pixel 26, the color divider elements in the color camera 10 'shown in FIGS. 4 to 8, must be significantly smaller, since not three, but only two sensor pixels 26 must be arranged on the surface of a color divider element 24. Correspondingly smaller and less expensive, with the same resolution, and the imaging optics 14 fail.

The imager 16 is also less sensitive to adjustment errors. If the arrangement of the color divider elements 24 during assembly is not aligned correctly with respect to the arrangement of the sensor pixels 26, this can be compensated later by a mathematical modification of the division ratios which are used by the evaluation electronics 30 in determining the color values become . FIG. 9 shows a variant of the second exemplary embodiment illustrated in FIGS. 4 to 8, in which collecting lenses 38 are likewise arranged between the color divider elements 24 and the sensor pixels 26, as in the first exemplary embodiment shown in FIGS. However, the collecting lenses 38 are not arranged in the vicinity of the color divider elements 24, but in the vicinity of the sensor pixels 26. As a result, the converging lenses 38 will only pass through light which is incident on a sensor pixel 26 to which the respective converging lens 38 is assigned. The converging lenses 38 make it possible to direct all the light which passes through the color divider elements 24 to the sensor pixels 26, even if, as indicated in FIG. 9, they are separated from one another by greater distances. Further, the converging lenses 38 allow the spectrally dispersed light having a numerical aperture to fall on the sensor pixels 26 at which they have optimum sensitivity. In contrast to the collection lenses 36 shown in Figure 2 but can be here by a small lateral displacement of the converging lenses 38 cause the light to strike all sensor pixels 26 at similar angles.

FIG. 10 shows a further variant of the image sensor 16 shown in FIGS. 4 to 8, in which between each

Color splitter element 24 and the sensor pixels 26 a the color divider element 24 associated beam displacement element 40 is arranged, which changes the division ratio, with which the spectral components of the incident light are distributed to the relevant color divider element 24 sensor pixel 26. In the illustrated embodiment, the beam displacement elements 40 are formed as a roof-like bent plates with parallel surfaces 42, 44. A bend line 46 of the beam displacement elements 40 extends perpendicular to the direction in which the spectral components are deflected by the color divider elements 24. As can be seen in the middle of FIG. 10, the beam displacement element displaces light of a wavelength lying in the green spectral component such that more light than the embodiment shown in FIG. 7 strikes the sensor pixel associated with the green spectral component and therefore marked with the letter g. In this way, the division ratio is increased in favor of the sensor pixels g. Due to the parallelism of the interfaces 42, 47, the propagation direction of the light does not change as it passes through the beam displacement element 40.

In the illustrated embodiment, the beam displacement is greatest for normal incidence on the beam displacement element 40, as shown in the center of FIG. The more oblique the light is, the less the distribution ratio changes; for light, which falls mainly on the red or blue spectral component associated sensor pixels r and b, although finds a Shifting the light instead, but this has no or at most low impact on the distribution ratio.

With such or otherwise shaped Strahlverlagerungs-- elements 40, which do not change the numerical aperture, for a given type of color divider elements 24, the division ratio can be changed so that an optimal, adapted to the spectral sensitivity of the human eye color determination is possible. Thus, the beam displacement elements 40 in particular corrugated parallel

Have interfaces 42, 44.

The roof-shaped beam displacement elements 40 arranged next to one another in a row can also be combined to form a plurality of strip-shaped components or even to a single larger component which has approximately the size of the image to be recorded. In FIG. 10, the beam displacement elements 40 arranged next to one another are therefore delimited from one another only by dashed lines.

3. Suitable Color Divider Elements The following describes examples of color divider elements that can be used in the imagers 16 of the color cameras 10, 10 'described above. a. Diffractive optical elements

FIG. 11 shows, in an enlarged section, a section through a plurality of color divider elements 24 and their associated sensor pixels 26. Each color divider element 24 has a prismatic, essentially wedge-shaped, support 45, which carries diffraction structures 47.

In the exemplary embodiment illustrated, the diffraction structures 47 are configured as blazed structures which are dimensioned in this way and exposed to the incident light 34. are directed to suppress the zeroth diffraction order and the majority of the incident light 34 is deflected in one of the first two diffraction orders. This diffraction is dependent on the wavelength of the light, so that the desired dependence of the deflection angle on the wavelength results. The application of the diffraction structures 47 to the wedge-shaped support 45 ensures that there is no net deflection on average. In other words, in FIG. 11 as much light is deflected by a color divider element 24 to the right as to the left, whereby the spectral components are divided symmetrically relative to the direction in which the light 34 impinges on the color divider elements 24.

The color divider elements 24 are mutually arranged on an envelope, whereby each two adjacent color divider elements 24 are different, but symmetrical with respect to a plane of symmetry extending along the boundary between the color divider elements. In this way it is achieved that the wavelength-dependent deflection of the light takes place in the manner described above with reference to FIGS. 5 and 6. As a result, for example, the two color divider elements 24 shown on the left in FIG. 11 direct the blue spectral component onto the common sensor pixel 26a, as was explained above with reference to FIG.

So far, for the sake of simplicity, it has been assumed that the light 34 strikes the color splitter elements 24 parallel to the optical axis, which is defined by the symmetry axis of the imaging optics 14. With axis-parallel light, however, no image can be realized; rather, converge to the receiving plane 22, which coincides with the image plane of the imaging optics 14, beams with a nonzero numerical aperture, so that on the color divider elements 24, an image of the object 18 is formed. In 1, such a converging beam is indicated by dashed lines and designated 46.

FIGS. 12a and 12b show how the deflection of the spectral components changes with an oblique incidence of light when the color splitter elements 24 are designed as diffractive optical elements as shown in FIG. It can be seen in FIG. 12a how light having a wavelength in the blue spectral component is deflected by a color splitter element 24 and falls on a sensor pixel 26, which is associated with the spectral color blue and is therefore marked with the letter b.

In the illustration on the right in FIG. 12b, on the other hand, it has been assumed that the light falls on the color divider element 24 at an angle, which is not at all different, from the optical axis, as indicated by arrows. Calculations have shown that the oblique incident light hardly affects the spectral splitting as such. This means that for two different wavelengths, the difference in the deflection angle is maintained approximately at oblique light.

However, the oblique incidence of light has the result that there is a kind of offset of the deflection angle, i. H. all wavelength-dependent deflection angles change by a certain amount. This offset causes obliquely incident light to leave the color divider element 24 at a different angle than perpendicularly incident light of the same wavelength and thus also incident on the sensor pixels 26 at a different split ratio.

In FIG. 12b, this offset in the plane of the sensor pixel 26 for light 34, which strikes the color splitter element 24 at a maximum angle inclined to the optical axis, is denoted by d; the dashed lines indicate for comparison the light path for perpendicularly incident light. For light incident on the other side inclined to the optical axis on the color divider element 24 and is indicated in the figure 12b with dotted arrows, there is a corresponding offset from the amount d to the opposite direction. In FIG. 12 this is indicated by dotted lines.

The offset by the amount d on both sides results in light of a particular wavelength not illuminating the area of two sensor pixels 26 as a whole, but of more than two sensor pixels. However, the associated smearing of the color information is still tolerable, as long as this additionally illuminated area is not greater than about half the area of a sensor pixel.

In order to keep this smearing of the color information as low as possible, it should be ensured by the imaging optics 14 that the numerical aperture NA of the light impinging on the color divider elements 24 is as small as possible. For this reason, imaging optics which enlarge the objects 18 in the object plane 20 onto the recording plane 22 are particularly suitable. The image-side numerical aperture is then smaller by the amount of the image scale than the object-side numerical aperture of the imaging optics 14. Well suited, for example, microscope objectives whose image-side numerical aperture is often less than 0.1 or even 0.05. b. Refractive optical elements

In the exemplary embodiment illustrated in FIG. 13, the color divider elements 24 are designed as refractive optical elements. Each color divider element consists of a straight-line prism of the type known in the art as the Amici prism. Each straight prism comprises three prisms 50, 52 and 54, the refractive surfaces of which each enclose an angle of 60 °. The three prisms 50, 52, 54 are arranged one behind the other on envelope and cemented together in a conventional manner. The two outer prisms 50, 54 are made of crown glass, while the middle prism 52 is made of flint glass. This results in the beam path illustrated in FIG. 14 for light of different wavelengths.

By appropriate selection of the optical materials for the prisms 50, 52, 54 is achieved that light with a desired center wavelength, which is indicated in the figure 14 with a solid line, can emerge from the Geradsichtprisma without deflection. Light with larger or smaller wavelengths are deflected symmetrically thereto, as indicated in Figure 14 by dashed or dotted lines. If two such Amici straight-front prisms are arranged on an envelope, as shown in FIGS. 13 and 14, the deflection directions alternate periodically so that two adjacent straight-line prisms can share a sensor pixel, as described above with reference to FIGS and FIG. 6 has been explained and shown in FIG.

Even with the formation of the colored parts elements as straight-view prisms, an oblique incidence of light leads to a smearing of the color information. Therefore, even with the use of straight-view prisms, the image-side numerical aperture of the imaging optics 14 should be as small as possible.

II. Color Image Projector

The planar arrangement of color divider elements in the receiving plane 22 according to the invention can be used in the light reversal direction to superimpose light of different colors produced by light pixels in order to produce a two-dimensional color image therefrom in an image-forming device. This will be explained below with reference to FIGS. 15 and 16 by means of exemplary embodiments which each show a color image projector 110. Parts corresponding to one of the above-described embodiments for a color camera 10 or 10 'are designated by reference numerals increasing by one hundred.

The color image projector 110 shown in a schematic meridional section in FIG. 15 has a housing 112 in which an imaging optics indicated at 114 and an image generation device 116 are arranged. The image generation device 116 contains a digital data memory 132, which is connected to a control electronics 130 for light pixels 126, which are applied to a carrier 128. Each group of three light-emitting pixels 126 is assigned a superposition element 124, wherein the superimposition elements are arranged side by side in a two-dimensional pattern in an object plane of the imaging optics 114. The overlay elements 124 respectively associated luminous pixels 126 generate different spectral colors, which are superimposed by the superposition elements 124 to a polychromatic light beam. The light beams impinging on the overlay elements 124 from different directions are thereby combined by the overlay elements 124 in such a way that they are telecentric, i. with parallel to the optical axis main rays, the superposition elements

124 leave. For the arrangement and design of the light pixels 126 and the overlay elements 124, the considerations and variants described above with reference to FIGS. 2 to 14 apply correspondingly. The image formed on the overlay elements 124 is now imaged with the aid of the imaging optics 114 on an image plane 120 on which it can be viewed. So that the light beams generated by the individual light pixels 126 are superimposed as completely as possible in the superposition elements 124, the light beams emerging from the superposition elements 124 must have a small numerical aperture, as is the case for an object point on the left edge of FIG

Object level of the imaging optics 114 is indicated by a dashed beam. Due to this small numerical aperture, the optical conductivity of imaging optics 114, which is defined as the product of numerical aperture and field size, is also small. The small optical conductivity, in turn, allows the use of small and simply constructed imaging optics 114.

The light pixels 126 should be as small as possible, since their dimensions determine the size of the overlay elements 124 and thus the resolution of the color image projector 110 significantly. Since such small light pixels 126 usually generate only relatively little light, in the exemplary embodiment of a color image projector 110 'shown in FIG. 16 it is intended to produce colored light spots using the color divider elements described in FIGS. 1 to 14.

For this purpose, the image generation device 116 does not have any self-radiating luminous pixels 126 there, but a light source 160 which illuminates a first arrangement of color divider elements 124a via a collimator lens 162. These color divider elements 124a are constructed in the same way as described above with reference to FIGS. 4 to 8. In place of the local sensor pixels 26, however, an array of switchable light control pixels 164 occurs in the image generation device 116. The transmittance of the light control pixels 164 can thereby be changed from one with a digital one

Image memory 132 connected control electronics 130 individually and continuously change, as indicated by different degrees of blackening in three of the light control pixels 164 shown in Figure 16. Through the spectral Divided by the color divider elements 126a, the light control pixels 164 are illuminated with light of different colors.

The light emitted by the light control pixels 164 is then superimposed by the following superposition elements 124b, so that a colored image is formed on the exit surface of the superposition elements 124b, which can be imaged onto an image plane 120 with the aid of the imaging optics 114. The light control pixels 164 thus correspond functionally to the light pixels 126 of the embodiment of a color image proctor 110 shown in FIG. 15, because they too can emit colored light of variable intensity.

The light control pixels 164 may, for example, be realized as LCD cells, as is known, for example, from flat panel displays. However, tiltable micromirrors which can be part of a microelectromechanical system (MEMS), as is frequently used, for example, in beamers, are also suitable as light control pixels 164.

The image generating device 116 shown in FIG. 16 makes it possible to use very high-intensity light sources and to produce the light generated therefrom virtually loss-free, ie. H. without the use of absorbing color filters, for the generation of the color image in the image plane 120 to use.

III. Spectrograph The embodiment shown in FIGS. 1 to 3 for a color camera 10 can be modified such that a spectroscope for spatially resolved spectroscopy is obtained. In this case, only the number of sensor pixels 26 needs to be increased sufficiently. FIG. 17 shows an exemplary embodiment of a spectrograph 210, in which each color divider element 24 is assigned nine sensor pixels. The larger the number of sensor pixels, which corresponds to a single color are associated with divider element 23, the higher the spectral resolution of the spectrograph 210.

Otherwise, the construction of the spectrograph 210 corresponds to those explained above with reference to FIGS. 1 to 3 for the color camera 10.

Claims

1. imager for the digital recording of a two ^¬ dimensional color image, comprising a plurality of light sensitive sensor pixels (26) and having a plurality of juxtaposed color separator elements (24), wherein a) each color separator element (24) at least two

Sensor pixels (26) are assigned and b) each color divider element (24) is designed such that it distributes incident thereon polychromatic light (34) to its associated sensor pixels (26) with a distribution ratio, which depends on the spectral composition of the impinging

Light dependent, characterized in that c) the color divider elements (24) are arranged in a two-dimensional pattern.

2. Imager according to claim 1, characterized in that the color divider elements (24) are designed such that they divert different spectral components of the incident colored light (34) in different directions.

3. Image recorder according to claim 1 or 2, characterized in that at least one color divider Element (24) comprises a diffractive optical element.

4. Image recorder according to claim 3, characterized in that the color divider element comprises a wedge-shaped prism (45) with diffractive structures (47) carried therefrom.

5. Imager according to one of the preceding claims, characterized in that at least one color divider element comprises a refractive optical element (50, 52, 54).

6. Image recorder according to claim 5, characterized in that the refractive optical element comprises a Geradsichtprisma.

7. Imager according to one of the preceding claims, characterized in that the Farbteiler- elements (24) are formed and arranged relative to the sensor pixels that light of one wavelength falls on at least two of the same color divider element associated sensor pixel (26).

8. Image recorder according to one of the preceding claims, characterized in that at least one, but not all of a color divider element (24) associated sensor pixels are additionally associated with an adjacent color divider element.

9. An image sensor according to claim 8, characterized in that there is at least one wavelength at which adjacent color divider elements (24) to which at least one sensor pixel (26) assigned together is net, deflecting light from the same direction of this wavelength in a direction that is different for the two color divider elements (24).

An imager according to claim 9, characterized in that the different directions are mirror-symmetrical with respect to a plane of symmetry extending between the two color divider elements (24).

Image sensor according to claim 10 and claim 4, characterized in that in adjacent color divider elements (24) to which at least one sensor pixel (26) is assigned in common, the wedge-shaped prisms (45) have alternating wedge angles.

Image sensor according to one of the preceding claims, characterized in that between each color divider element (24) and the sensor pixels (26) a refractive ray displacement element (40) associated with the color divider element is arranged which alters the division ratio and the parallel optical surfaces (42 , 44).

Digital camera (10), with an imaging optical unit (14), with which an object (18) can be imaged on an image plane (22), and with an image recorder (16) according to one of the preceding claims, characterized in that the imaging optics (14 ) has a picture-side numerical aperture of less than 0.1, preferably less than 0.05. An imaging device for reproducing a color image, comprising a plurality of switchable light pixels (126) and a plurality of juxtaposed overlay elements (124), wherein a) each overlay element (124) at least two light pixels (126) are assigned, the light of different colors b) the overlay elements (124) in one

Two-dimensional pattern are arranged, and wherein c) each overlay element (124) is formed such that it overlaps light which is incident from different directions with different colors, to a common beam.

Spectroscope (210) for the spatially resolved Spektro ^¬ microscopy, with a plurality of light-sensitive sensor pixels and having a plurality of juxtaposed color separator elements (24), wherein a) each color separator element (24) comprises at least four sensor pixels (26) are associated and b) of each color splitter Element (24) is designed such that it distributes colored light impinging thereon onto its associated sensor pixels (26) at a distribution ratio which depends on the spectral composition of the incident light, characterized in that the color divider elements (24) are arranged in a two-dimensional pattern.