Method for classifying light-emitting semiconductor components and image sensor application having an image sensor and a semiconductor element

Abstract

The invention relates to a method for classifying a light-emitting semiconductor component (301) for an image sensor application, wherein the semiconductor component (301) is designed as a light source for an image sensor (302), comprising the following steps: providing the light-emitting semiconductor component (301); determining at least one of the following parameters of the light emitted with an emission spectrum by the light-emitting semiconductor component (301) during operation: R=∫qR(λ).Math.S(λ)dλ.Math.texp, G=∫qG(λ).Math.S(λ)dλ.Math.texp, B=∫qB(λ).Math.S(λ)dλ.Math.texp, wherein qR(λ), qG(λ), and qB(λ) are spectral sensitivities of a red, green, and blue color channel of the image sensor (302), S(λ) is the emission spectrum of the light-emitting semiconductor component (301), texp is an exposure time, and λ designates a wavelength; classifying the light-emitting semiconductor component (301) into a class from a group of classes, which are characterized by different value ranges of at least one parameter that depends on at least one of the parameters R, G, and B. The invention further relates to an image sensor application.

Claims

1. A method for classifying a light-emitting semiconductor component for an image sensor application, wherein the light-emitting semiconductor component is configured as a light source for an image sensor, comprising: providing the light-emitting semiconductor component comprising at least two light-emitting semiconductor chips; determining at least one of R, G, or B of a light emitted during operation with an emission spectrum by the light-emitting semiconductor component;
wherein R=∫q.sub.R(λ).Math.S(λ)dλ.Math.t.sub.exp;
wherein G=∫q.sub.G(λ).Math.S(λ)dλ.Math.t.sub.exp;
wherein B=∫q.sub.B(λ).Math.S(λ)dλ.Math.t.sub.exp; wherein q.sub.R(λ), q.sub.G(λ) and q.sub.B(λ) are spectral sensitivities of a red, green, and blue color channel of the image sensor, S(λ) is the emission spectrum of the light-emitting semiconductor component, t.sub.exp is an exposure time, and λ designates a wavelength; categorizing the light-emitting semiconductor component in a class from a group of classes which are characterized by different value ranges of at least one parameter that depends on at least one of R, G, or B; selecting the light-emitting semiconductor component for use with one or more other light-emitting semiconductor components having a same class as the class of the light-emitting semiconductor component; and illuminating the light source based on the selecting.

2. The method according to claim 1, wherein the light-emitting semiconductor component is categorized in the class from the group of classes which are characterized by respective value ranges of parameters:
rg1=R/(R+G+B), or bg1=B/(R+G+B), or both.

3. The method according to claim 1, wherein the light-emitting semiconductor component is categorized in the class from the group of classes which are characterized by respective value ranges of parameters:
rg2=G/R, or bg2=G/B, or both.

4. The method according to claim 1, wherein the light-emitting semiconductor component is categorized in the class from the group of classes which are characterized by respective value ranges of parameters:
rg3=G/R, or bg3=G/B, or both.

5. The method according to claim 2, wherein the class in which the light-emitting semiconductor component is categorized is characterized by rg1 and bg1 values which correspond to corresponding rg1 and bg1 values of sunlight or of light according to a standard illuminant A or D or light of a Planckian emitter.

6. The method according to claim 1, wherein the image sensor forms part of a video camera, a photographic apparatus, a mobile telephone, or a medical imaging device.

7. The method according to claim 1, wherein the light-emitting semiconductor component forms part of a video camera, a photographic apparatus, a mobile phone, a stadium lighting system, a stage lighting system, a studio lighting system, or a medical imaging device.

8. The method according to claim 1, wherein the light-emitting semiconductor component emits white light during operation.

9. The method according to claim 1, wherein the image sensor is a CCD sensor or a CMOS sensor.

10. An apparatus comprising: an image sensor; and a light-emitting semiconductor component which is configured as a light source for the image sensor and comprises at least two light-emitting semiconductor chips, wherein the light-emitting semiconductor component is selected by: determining at least one of R, G, or B of a light emitted during operation with an emission spectrum by the light-emitting semiconductor component;
wherein R=∫q.sub.R(λ).Math.S(λ)dλ.Math.t.sub.exp;
wherein G=∫q.sub.G(λ).Math.S(λ)dλ.Math.t.sub.exp;
wherein B=∫q.sub.B(λ).Math.S(λ)dλ.Math.t.sub.exp; wherein q.sub.R(λ), q.sub.G(λ) and q.sub.B(λ) are spectral sensitivities of a red, green, and blue color channel of the image sensor, S(λ) is the emission spectrum of the light-emitting semiconductor component, t.sub.exp is an exposure time, and λ designates a wavelength; categorizing the light-emitting semiconductor component in a class from a group of classes which are characterized by different value ranges of at least one parameter that depends on at least one of R, G, or B; selecting the light-emitting semiconductor component for use with one or more other light-emitting semiconductor components having a same class as the class of the light-emitting semiconductor component; and illuminating the light source.

11. The method according to claim 3, wherein the class in which the light-emitting semiconductor component is categorized is characterized by rg2 and bg2 values which correspond to corresponding rg2 and bg2 values of sunlight or of light according to a standard illuminant A or D or light of a Planckian emitter.

12. The method according to claim 4, wherein the class in which the light-emitting semiconductor component is categorized is characterized by rg3 and bg3 values which correspond to corresponding rg3 and bg3 values of sunlight or of light according to a standard illuminant A or D or light of a Planckian emitter.

13. The method of claim 1, wherein the light-emitting semiconductor component and the one or more other light-emitting semiconductor components having the same class are configured for use in an illuminating application of the image sensor.

14. A method for classifying a light-emitting semiconductor component for an image sensor application, wherein the light-emitting semiconductor component is configured as a light source for an image sensor, comprising: providing the light-emitting semiconductor component comprising at least two light-emitting semiconductor chips; determining at least one of R, G, or B of a light emitted during operation with an emission spectrum by the light-emitting semiconductor component;
wherein R=∫q.sub.R(λ).Math.S(λ)dλ.Math.t.sub.exp;
wherein G=∫q.sub.G(λ).Math.S(λ)dλ.Math.t.sub.exp;
wherein B=∫q.sub.B(λ).Math.S(λ)dλ.Math.t.sub.exp; wherein q.sub.R(λ), q.sub.G(λ) and q.sub.B(λ) are spectral sensitivities of a red, green, and blue color channel of the image sensor, S(λ) is the emission spectrum of the light-emitting semiconductor component, t.sub.exp is an exposure time, and λ designates a wavelength; categorizing the light-emitting semiconductor component in a class from a group of classes which are characterized by different value ranges of at least one parameter that depends on at least one of R, G, or B; sorting the light-emitting semiconductor component into a category from a group of categories; and selecting the light-emitting semiconductor component during illumination for use with one or more other light-emitting semiconductor components having a same class as the class of the light-emitting semiconductor component.

Description

(1) Shown in:

(2) FIG. 1 is a simulation of color locations of various light-emitting semiconductor components,

(3) FIG. 2 is a schematic diagram of a method for classifying a light-emitting semiconductor component pursuant to an exemplary embodiment,

(4) FIGS. 3A and 3B are image sensor applications pursuant to further exemplary embodiments and

(5) FIG. 4 a chromaticity diagram with color locations of light-emitting semiconductor components pursuant to a further exemplary embodiment.

(6) Identical, similar or seemingly identical elements can be provided with the same reference signs in the exemplary embodiments and illustrations. The elements shown and the size ratios thereof among each other should not be viewed as true-to-scale; instead individual elements, such as layers, parts, components and areas, for example, can be shown exaggeratedly large for the sake of better representation and/or for the sake of better understanding.

(7) As described above in the general section, various light-emitting semiconductor components can comprise different emission spectrums but still have identical standard color values in the CIE standard chromaticity diagram. However, the color locations of the different emission spectrums in the color space of an image sensor can sometimes significantly differ from each other. That is due to the fact that the CIE standard chromaticity diagram is based on the human eye and the sensitivity thereof, from which the sensitivity of the image sensor deviates, and therefore different spectral components of the emission spectrum have differing degrees of weighting in the two color spaces. FIG. 1 shows a simulation for the color locations of a plurality of light-emitting semiconductor components with different emission spectrums in the XYZ color space, i.e. in the CIE standard chromaticity diagram, as well as in the image sensor chromaticity diagram. The upper horizontal and the right vertical axes designate the relative deviation of the chromaticity coordinates cx, cy from a mean value of μ.sub.cx, μ.sub.cy of the entirety of all simulated semiconductor components in the XYZ color space, whereas the lower horizontal and left vertical axes designate the relative deviation of corresponding chromaticity coordinates from corresponding mean values in the image sensor color space. The axial assignment in the diagram is also indicated by the arrows.

(8) The emission spectrums of the different light-emitting semiconductor components are simulated in such a way that they may be varied but still all result in the same color location in the XYZ color space. Thus, only one point 11 (filled-in circle) is recognizable in the diagram shown, which represents the overlapping color locations in the XYZ color space. Conversely, a plurality of different chromaticity coordinates results from the different emission spectrums in the image sensor color space and thus a cloud of points (filled-in quadrats) of which point 12 is exemplarily designated by a reference numeral.

(9) Different light-emitting semiconductor components, i.e. semiconductor components with different emission spectrums having the same chromaticity coordinates in the XYZ color space can thus form a large cloud of different color locations in the image sensor color space, and therefore each of the light-emitting semiconductor components can lead to different raw data values for the image sensor.

(10) FIG. 2 describes a method for classifying a light-emitting semiconductor component for an image sensor application, wherein the semiconductor component is configured as light source for an image sensor, said method taking into account the effect shown in FIG. 1 and implementing a classification in the color space of the image sensor. To this end, a light-emitting semiconductor component is provided in a first step 1. The light-emitting semiconductor component, which can be designed pursuant to the description in the general section and can comprise one or more light-emitting semiconductor chips in combination with one or more wavelength conversion substances, if need be, has an emission spectrum S(λ).

(11) In a further method step 2, at least one of the following parameters of the light emitted during operation with the emission spectrum S(λ) by the light-emitting semiconductor component is determined:
R=∫q.sub.R(λ).Math.S(λ)dλ.Math.t.sub.exp,
G=∫q.sub.G(λ).Math.S(λ)dλ.Math.t.sub.exp,
B=∫q.sub.B(λ).Math.S(λ)dλ.Math.t.sub.exp,

(12) In this respect, q.sub.R(λ), q.sub.G(λ) and q.sub.B(λ) are the spectral sensitivities of a red, green and blue color channel of the image sensor, which are known by prior determination of from manufacturer specifications. The spectral sensitivities comprise, for example, the physical unit CV/(W/sr/m.sup.2/nm)/t.sub.exp, wherein the “code value CV is dependent upon the irradiated amount of light and the exposure time t.sub.exp. Accordingly, the emission spectrum S(λ) is the spectral density. The integration ensues via a wavelength range containing all the relevant wavelengths contained in the spectral sensitivities and in the emission spectrum S(λ), i.e. via a wavelength range in the visible spectral range of 350 nm to 800 nm or from 380 nm to 750 nm, for example. The R, G and B values thus determined define the image sensor color space.

(13) The emission spectrum can, for example, be specified in advance or be known from manufacturer specifications. An alternative possibility is the use of a measurement device which, for example, takes into account the color channels of the image sensor and emits the latter pursuant to the previously stated determination of the parameters R, G and B.

(14) The image sensor can, for example, be a CCD sensor or a CMOS sensor having a plurality of image sensor elements in the form of sensor pixels. The individual color channels can each be formed by part of the image sensor elements with corresponding color filters.

(15) In a further (method) step 3, the light-emitting semiconductor component is categorized in a class among a group of classes, which are characterized by various value ranges of at least one parameter that depend upon at least one of the parameters R, G and B. Thus, at least one of the parameters R, G and B is taken into account in the classification. The individual classes are characterized by value ranges, which can be defined by a target value and a deviation therefrom. The relative deviation from the target value in the value range of each class can, for example, be less than or equal to 20%. Furthermore, more minimal deviations are also possible, as described above in the general section.

(16) It is particularly advantageous if the classification ensues in a relative, standardized image sensor color space defined by parameters, which are not dependent on the exposure time t.sub.exp. For example, in step 3 the light-emitting component can be categorized in a class from a group of classes characterized by the respective value ranges of the parameters rgX and/or bgX. In this respect, X can be=1, 2 or 3.
−X=1: rg1=R/(R+G+B),bg1=B/(R+G+B),
−X=2: rg2=G/R,bg2=G/B,
−X=3: rg3=R/G,bg3=B/G.

(17) One or more of the light-emitting semiconductor components categorized in classes by the previously described method can be used for image sensor applications in which images or image sequences are picked up by means of an image sensor.

(18) FIG. 3a shows an exemplary embodiment of an image sensor application formed by a camera in a mobile telephone 300. As indicated by the dashed line, said mobile telephone 300 comprises at least one light-emitting semiconductor component 301 and an image sensor 302 and is provided and configured for picking up both individual images and image sequences. The mobile telephone 300 represents a plurality of mobile telephones, which preferably all comprise one or more light-emitting semiconductor components 301, which are selected from the same class or the same classes pursuant to the previously described method. This advantageously allows the emission spectrums of the light-emitting semiconductor components 301 in each mobile telephone 300 in the respective image sensor 302 to substantially achieve the identical raw data in the individual color channels, thus allowing a uniform adjustment of the white balance algorithm even in the event of a plurality of mobile telephones, and therefore removes the need for every mobile telephone produced to be separately calibrated.

(19) Alternatively to the mobile telephone 300 shown, the image sensor application can, for example, also be a video camera or a photographic appliance or a medical imaging device.

(20) FIG. 3B shows a further embodiment of an image sensor application configured for picking up images or image sequences in a stadium, on a stage or in a studio and having a stadium, stage or studio lighting system. The lighting 303, which can be formed by one or more spotlights or by a floodlight system, for example, and which comprises a plurality of light-emitting semiconductor components 301, allows a scene to be illuminated that can be picked up by means of the camera 304. Said camera 304 has an image sensor 302. As described in conjunction with the preceding embodiment, a method pursuant to the preceding description is also used for selecting the light-emitting semiconductor components 301 during the illuminating application of the embodiment of FIG. 3B.

(21) In particular, for example, it can be advantageous to use light-emitting semiconductor components 301 in the previously described image sensor applications, the classifying parameters of which, in particular the rgX and bgX values thereof, correspond to the sun or an equivalent ambient light according to a standard illuminant A or D or a Planckian emitter. In the event of minimal scattering around suitable target values and a corresponding classification, the adjustment of the white balance algorithm can possibly be omitted. In particular, a reproducible white balance can take place in the event of identical color locations in the image sensor color space.

(22) Should a plurality of light-emitting semiconductor components with different chromaticity coordinates originating from different classes of the previously described method be used, including a plurality of light-emitting semiconductor components, for example, in the event of two light-emitting semiconductor components the latter thus form a line 401 in the image sensor space, which intersects the Planckian black body curve twice, as shown in FIG. 4. In the event of more than two light-emitting semiconductor components with different emission spectrums being used, the latter form a polygon in the image sensor color space, which includes part of the Planckian black body curve. The varied light-emitting semiconductor components allow different mixed spectrums for the image sensor application to be generated, thus in turn allowing mixed spectrums, which are adjusted to a plurality of ambient light types, to be generated by an adjustment of the resulting rgX and bgX values.

(23) The exemplary embodiments described in conjunction with the illustrations can comprise further or alternative features pursuant to the description in the general section.

(24) The description on the basis of the exemplary embodiments does not limit the invention thereto. Instead, the invention comprises every new feature as well as every combination of features, which in particular includes every combination of features in the claims, even if such claim or such combination is not itself explicitly stated in the claims or exemplary embodiments.