# US 8,786,741 B2 · Digital multi-spectral camera system having at least two independent digital cameras

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- Number: US 8,786,741 B2
- Document ID: US8786741B2
- Status: Granted
- Kind: B2
- Application number: 13/824,976
- Filed: 2011-07-21
- Published: 2013-09-19
- Granted: 2014-07-22
- Earliest claimed: 2010-09-28
- Assignees: Leica Geosystems AG
- Applicants: Martin Timm; Martin Welzenbach
- Inventors: Martin Timm; Martin Welzenbach
- Web page: https://patentgrep.com/patent/US8786741B2

## CPC

- H04N 23/88: for colour balance, e.g. white-balance circuits or colour temperature control
- G01C 11/02: Picture taking arrangements specially adapted for photogrammetry or photographic surveying, e.g. controlling overlapping of pictures
- G01J 3/2803: {using photoelectric array detector}
- G01J 3/36: Investigating two or more bands of a spectrum by separate detectors
- H04N 23/71: Circuitry for evaluating the brightness variation
- H04N 25/11: Arrangement of colour filter arrays [CFA]; Filter mosaics
- H04N 25/131: including elements passing infrared wavelengths
- H04N 25/41: {Extracting pixel data from a plurality of image sensors simultaneously picking up an image, e.g. for increasing the field of view by combining the outputs of a plurality of sensors}
- H10F 77/331: {for filtering or shielding light, e.g. multicolour filters for photodetectors}
- G01J 2003/1213: {Filters in general, e.g. dichroic, band}
- H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION
- G01C: MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY (measuring liquid level G01F; radio navigation, determining distance or velocity by use of propagation effects, e.g. Doppler effects, propagation time, of radio waves, analogous arrangements using other waves G01S)
- G01J: MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY (light sources F21, H01J, H01K, H05B; investigating properties of materials by optical means G01N)
- H10F: INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION

## Abstract

A digital camera system having at least two independent digital cameras, which capture image signals in different narrow-band spectral ranges, wherein each of the at least two independent digital cameras comprises at least one separate two-dimensional digital image sensor, preferably a CCD sensor or a CMOS sensor, and at least one filter element corresponding to the particular narrow-band spectral range connected upstream of the at least one two-dimensional digital image sensor and having at least one filter region. The at least one color filter element additionally comprises at least one neutral region, which is translucent in a spectral range that includes at least the different narrow-band spectral ranges of the at least two independent digital cameras, in particular in a panchromatic spectral range, and which is assigned to at least one specific neutral, in particular unused, pixel region of the associated at least one two-dimensional digital image sensor.

## Claims

### Claim 1

A digital camera system, comprising:
an image processing unit; and
at least two independent digital cameras, which capture image signals in different narrow-band spectral regions, which each have a separate shutter and/or a separate objective lens and which each have at least one separate sheet-like digital image sensor and at least one color filter element with at least one filter region, which at least one color filter element is arranged upstream of the at least one sheet-like digital image sensor and corresponds to the respective narrow-band spectral region, which at least one color filter element additionally has at least one neutral region, which is light-transmissive in a spectral region, which at least comprises the different narrow-band spectral regions of the at least two independent digital cameras and which is arranged over at least one specific neutral pixel region of the associated at least one sheet-like digital image sensor, wherein the image processing unit is configured to carry out a method for setting a color balance for the digital camera system, wherein deviations in the exposure times and/or the recorded light quantities between the at least two independent digital cameras of the digital camera system are determined during synchronous image recording by the at least two independent cameras of the same scene, wherein, after the synchronous image recording has taken place, the light quantities recorded in the respective neutral pixel regions of the sheet-like digital image sensors of the at least two independent digital cameras are compared to one another, whereupon, while processing an image of the same scene recorded synchronously in the respective different narrow-band spectral regions by the at least two independent digital cameras, an equalization calculation is performed in such a way that the image signals of the respective narrow-band spectral regions are respectively left unchanged, damped or amplified in accordance with the previously determined deviations.

### Claim 2 (depends on 1)

The digital camera system as claimed in claim 1, wherein the at least two independent digital cameras are arranged in such a way with respect to one another that at least approximately the same scene can be recorded in the different narrow-band spectral regions of the at least two independent digital cameras and a multispectral image of the scene can be combined from the image signals of the different narrow-band spectral regions.

### Claim 3 (depends on 1)

The digital camera system as claimed in claim 1, wherein the at least two independent digital cameras have substantially equivalent recording properties apart from the respective color filter elements thereof corresponding to the different narrow-band spectral regions and/or have substantially the same design, wherein the sheet-like digital image sensors thereof, the optionally present separate shutters thereof and the objective lenses thereof have substantially the same design.

### Claim 4 (depends on 1)

The digital camera system as claimed in claim 1, wherein the at least one color filter element has two strip-shaped neutral regions at opposite sides of the filter region.

### Claim 5 (depends on 1)

The digital camera system as claimed in claim 1, further comprising:
a first independent digital camera with a first color filter element, which is light-transmissive in a spectral region with wavelengths from approximately 600 nm to approximately 700 nm;
a second independent digital camera with a second color filter element, which is light-transmissive in a spectral region with wavelengths from approximately 500 nm to approximately 600 nm;
a third independent digital camera with a third color filter element, which is light-transmissive in a spectral region with wavelengths from approximately 400 nm to approximately 500 nm; and
a fourth independent digital camera with a fourth color filter element, which is light-transmissive in a spectral region with wavelengths from approximately 700 nm to approximately 900 nm.

### Claim 6 (depends on 5)

The digital camera system as claimed in claim 5, wherein the first, the second, the third and the fourth color filter element respectively have a neutral region, which is light-transmissive in a spectral region from approximately 400 nm to approximately 900 nm.

### Claim 7 (depends on 1)

The digital camera system as claimed in claim 1 for photogrammetry for recording aerial images from aircraft.

### Claim 8 (depends on 1)

A method for setting a color balance for a digital camera system as claimed in claim 1, wherein deviations in the exposure times and/or the recorded light quantities between the at least two independent digital cameras of the digital camera system are determined during synchronous image recording by the at least two independent cameras of the same scene, wherein, after the synchronous image recording has taken place, the light quantities recorded in the respective neutral pixel regions of the sheet-like digital image sensors of the at least two independent digital cameras are compared to one another, whereupon, while processing an image of the same scene recorded synchronously in the respective different narrow-band spectral regions by the at least two independent digital cameras, an equalization calculation is performed in such a way that the image signals of the respective narrow-band spectral regions are respectively left unchanged, damped or amplified in accordance with the previously determined deviations.

### Claim 9 (depends on 8)

An image processing unit of a digital camera system, configured to carry out a method as claimed in claim 8.