Method and device for suppressing electromagnetic background radiation in an image

• US 20040208340A1
• Filed: 02/03/2004
• Published: 10/21/2004
• Est. Priority Date: 07/06/2001
• Status: Active Grant

• Current Assignee: Leica Geosystems AG (Hexagon AB)
• Original Assignee: Leica Geosystems AG (Hexagon AB)
• Inventors: Kirschner, Holger
• Granted Patent: US 7,809,182 B2
• Time in Patent Office: Days
• US Class Current: 382/103
• CPC Class Codes: F41G 3/145 using a target illuminator
• CPC Class Codes: G01S 17/89 for mapping or imaging
• CPC Class Codes: G01S 7/487 Extracting wanted echo signals , e.g. pulse detection

Abstract

The invention relates to a method and a corresponding device with which images (A, B) for the same sensing range, however in different wavelength ranges (P, N1, N2), are recorded at the same time or about the same time, and with which a signal to be detected is recorded for an image (A) serving as a P-image, and the wavelength of the signal is suppressed for an image (B) serving as an N-image. The intensity of the background in the P-image (A) is deduced from the N-image (B) while using a model for the interfering radiation or background radiation (2). The position of the signal to be detected is determined by comparing the image contents of the P-image (A) and the background image (C) derived from the N-image (B).

Claims

1. Method for suppressing electromagnetic background radiation (2) in a defined spectral range (P) relative to a signal to be detected, in particular, for position determination of a laser spot (3),

comprising means for recording electromagnetic radiation (6), preferably comprising at least one detector (6a, 6b) consisting of a plurality of components, and

comprising means for signal and information processing (7),

at least one uni-dimensional or multidimensional P-image (A) for the defined spectral range (P) and

at least one uni-dimensional or multidimensional N-image (B) for at least one further defined spectral range (N1, N2) differing from that of the P-image (A)

being recorded by the means for recording electromagnetic radiation (6), preferably at the same time,

characterized in that

the image brightness S_SP of the background radiation (2) in the P-image (A) is deduced and the signal to be detected is extracted by the means for signal and

information processing (7) from the N-image (B) on the basis of a model of the spectral distribution of the background radiation (2),

the spectral ranges (P, N1, N2) of the P-image (A) and of the N-image (B) being determined as a two-band neighbourhood method by the choice of a wavelength band in each case for the P-image (A) and the N-image (B) , and

the wavelength band of the N-image (B) being either on the short-wave or on the long-wave side of the wavelength band of the P-image (A) and preferably an overlap of the two wavelength bands being minimized.

3. Method according to claim 1,

characterized in that

the spectral range (P, N1, N2) of the at least one N-image (B) is determined by the choice of two wavelength bands,

the wavelength bands of the at least one N-image (B) in each case being on the short-wave and/or long-wave side of the wavelength band (P) of the at least one P-image (A).

4. Method according to claim 1,

characterised in that,

for estimating and eliminating contributions of different interfering radiation sources,

the image brightness S_SP of the background radiation (2) is derived by carrying out at least one or more of the methods according to any of claims 1 to 3 once or several times, in particular for different spectral ranges.

5. Method according to claim 1,

characterized in that,

the derivation of the image brightness S_SP of the background radiation (2) in the P-image (A) is carried out using at least one of the following methods

extrapolation of at least one image brightness S_SN recorded in the N-image (B),

calculation of the weighted mean value of at least two image brightnesses S_SNi recorded in the N-image (B).

2. Method for suppressing electromagnetic background radiation (2) in a defined spectral range (P) relative to a signal to be detected, in particular for position determination of a laser spot (3),

comprising means for recording electromagnetic radiation (6), preferably comprising at least one detector (6a, 6b) consisting of a plurality of components, and comprising means for signal and information processing (7),

at least one uni-dimensional or multidimensional P-image (A) for the defined spectral range (P) and

at least one uni-dimensional or multi-dimensional N-image (B) for at least one further defined spectral range (N1, N2) differing from that of the P-image (A)

being recorded by the means for recording electromagnetic radiation (6), preferably at the same time,

characterized in that

the image brightness S_SP of the background radiation (2) in the P-image (A) is deduced and the signal to be detected is extracted by the means for signal and information processing (7) from the N-image (B) on the basis of a model of the spectral distribution of the background radiation (2),

the spectral ranges (P, N1, N2) of the P-image (A) and of the N-image (B) being determined by the choice of at least one wavelength band in each case for the P-image (A) and the N-image (B),

the wavelength bands each sensing different lines (1, 5a, 5b).

6. Device for suppressing electromagnetic background radiation (2) in a defined spectral range (P) relative to a signal to be detected, in particular for position determination of a laser spot (3) to be detected,

comprising means for recording electromagnetic radiation (6), and

comprising means for signal and information processing (7),

the means for recording electromagnetic radiation (6) being designed for, preferably simultaneous, recording of at least one P-image (A) and at least one N-image (B)

and the means for signal and information processing (7) being designed so that electromagnetic background radiation (2) can be suppressed from the different content of P-image (A) and N-image (B) adjusted by the means for signal and information processing (7),

characterized in that

the means for recording electromagnetic radiation (6) have at least two detectors for recording images (A, B) in at least two different, defined spectral ranges (P, N1, N2) and

the means for signal and information processing (7) are designed so that the electromagnetic background radiation (2) can be suppressed on the basis of a model of the spectral distribution of the background radiation (2).

7. Device according to claim 6,

characterized in that

the spectral range of the means for recording electromagnetic radiation (6) is limited by at least one spectral filter (6d, 6e) and/or

the means for recording electromagnetic radiation (6) have at least one detector (6a, 6b) which consists of two or more semiconductor materials which result in a spectrally selective response behaviour of the detector (6a, 6b).

8. Device according to claim 6,

characterized in that

the means for signal and information processing (7) are designed so that the at least one P-image (A) and the at least one N-image (13) are translatable and/or rotatable relative to one another and/or can be changed on the relative imaging scale, preferably by digital signal processing.

9. Measuring instrument, in particular for geodetic surveying,

characterized in that

it has a device for spectrally selective suppression of an electromagnetic background radiation (2), in particular for position determination of a laser signal (3) to be detected, according to claim 6.

10. Use of a device according to claim 6 for identifying a laser spot (3) as a mark for subsequent measuring processes, in particular, for distance measurements to the marked point.

11. Use of a device according to claim 6 for identifying a source of a laser spot, in particular for identifying a target-illuminating laser (target designation).