DE102009042692A1 - Infrared detector i.e. infrared camera, has zone filter arranged in optical path between infrared sensor and window, where zone filter passes light of wavelength range through zone and light of another wavelength range through another zone - Google Patents

Abstract

The invention relates to an infrared detector in which an infrared sensor (5) accommodated in a vacuum housing (2) is aligned along an optical axis (A) with a window (3) closing off the vacuum housing (2), so that one with a first lens ( 1) captured image (B) through the window (3) on the infrared sensor (5) is mapped. To increase the robustness and to simplify the construction of such an infrared detector, the invention proposes that in the beam path between the infrared sensor (5) and the window (3) a zone filter (4) is turned on, in which a first zone (Z1) permeable to Light of a first wavelength range, a second zone (Z2) is transparent to light of a second wavelength range different from the first wavelength range.

Description

The invention relates to an infrared detector according to the preamble of claim 1.

Such an infrared detector is for example from the US Pat. No. 7,157,706 B2 or the US 2008/0304126 A1 known. In the known infrared detector an infrared sensor in the beam path upstream of a diaphragm with variable aperture. The infrared sensor and the diaphragm are surrounded by a vacuum housing, which is provided in the beam path with a window. The window, in turn, is preceded by a lens in the beam path with which an image captured thereby is imaged through the window and the diaphragm onto the infrared sensor. In the known infrared detector to achieve a large signal to noise ratio, the aperture of the diaphragm is adapted to an opening angle of an upstream optics. For this purpose, an aperture of the aperture can be adapted to the particular lens used. The provision of a shutter with a variable aperture within a vacuum housing is expensive. Apertures with a variable aperture are prone to repair.

The object of the invention is to eliminate the disadvantages of the prior art. In particular, an infrared detector constructed as simply and robust as possible, with which images in several different wavelength ranges can be detected. According to a further object of the invention, the infrared detector should have the largest possible signal-to-noise ratio.

This object is solved by the features of claim 1. Advantageous embodiments of the invention will become apparent from the features of claims 2 to 16.

According to the invention it is provided that in the beam path between the infrared sensor and the window, a zone filter is turned on, in which a first zone is transparent to light of a first wavelength range and a second zone transmissive to light of the first wavelength range different second wavelength range. With the proposed zone filter, it is possible in a surprisingly simple and cost-effective manner to dispense with a diaphragm with a variable aperture. The proposed infrared camera is robust and prone to interference. It can be manufactured inexpensively and allows the capture of images in several different wavelength ranges. The proposed infrared detector is also characterized in that it has a high signal-to-noise ratio.

In the proposed zone filter, the second zone advantageously surrounds the first zone. The zone filter can have different geometries. It may for example be round, oval or rectangular.

In the case of a round design, the first and the second zone are expediently formed coaxially. However, the two zones can - especially if they are not round - also be arranged concentrically or symmetrically to each other. In addition, it is also conceivable that the two zones are not arranged in a single plane, but in different planes (with respect to the optical beam path). The second zone may also be surrounded by a frame which is impermeable to all wavelengths.

Furthermore, it has proven expedient that the first wavelength range is greater than the second wavelength range. In particular, the second wavelength range may be included in the first wavelength range, i. H. form a subset of it. The first wavelength range may extend from 3 to 15 μm, preferably from 3 to 12 μm. From the first wavelength range, a wavelength interval of more than 5 μm and less than 8 μm is expediently excluded. The wavelength interval causes an interference signal caused by the atmosphere. By excluding the wavelength interval from the first wavelength range, unwanted background noise can be largely eliminated. - The wavelength interval can also be locked by a turned on in the beam filter. Such a filter may be part of the window, for example.

The second wavelength range may extend from 8 to 15 μm, preferably 8 to 12 μm. With the first wavelength range, therefore, images in the middle and far infrared, with the second wavelength range only images in the far infrared range can be detected.

According to a further embodiment, the infrared detector in the beam path is preceded by a diaphragm with a fixed predetermined aperture. In this case, the diaphragm may be provided in a diaphragm housing surrounding the infrared sensor. In this embodiment, the zone filter can cover the aperture. In this case, it is not absolutely necessary for the zone filter to surround the second zone with a frame that is impermeable to all wavelengths.

According to a further embodiment, a cooling device for cooling the infrared sensor and the zone filter is provided. It may be z. B. act for a Stirling refrigerator. Thus, in particular the infrared sensor and the zone filter can be at a temperature in the range of about 50 to 120 K to be cooled. In this case, the vacuum housing may be formed in the manner of a Dewar. By providing the cooling device, it is possible to keep unwanted background radiation as low as possible.

According to a further embodiment, a first lens is provided for imaging the image. The first lens is arranged outside the vacuum vessel along the optical axis of the window. The first lens may also be part of an imaging optic. In the imaging optics, it may be z. B. to act mirror optics.

According to a further embodiment, a second lens different from the first lens is provided, which can be switched on simultaneously with or instead of the first lens in the beam path. The first and the second lens may be part of an exchange optics.

The first and the second lens are expediently designed corresponding to the zone filter. An image captured by the first lens may be imaged onto the infrared sensor substantially through the first and second zones. An image captured by the second lens may be imaged substantially by the first zone on the infrared sensor. This makes it possible to capture images in the mid-infrared range as well as images in the middle and far-infrared range.

An exemplary embodiment will be explained in more detail below with reference to the drawings. Show it:

1 a schematic representation of an infrared camera and

2 a plan view of the zone filter according to 1 ,

At the in 1 shown infrared camera along an optical axis A is a first lens 1 , a vacuum housing 2 closing window 3 , a zone filter 4 and an infrared sensor 5 arranged. The infrared sensor 5 is inside a shutter housing 6 added. In the infrared sensor 5 it can be a conventional infrared imaging sensor. A provided in the beam path invisible aperture is denoted by the reference numeral 7 designated. With the reference number 8th is a cooling device referred to, on which the diaphragm housing 6 is mounted. By means of the cooling device 8th In particular, the infrared sensor 5 and the zone filter 4 cooled.

In 1 is further denoted by the reference numeral 9 denotes a second lens which coincides with or alternatively to the first lens 1 can be turned on in the beam path. One to the first lens 1 corresponding first opening angle is denoted by the reference f1 and one to the second lens 9 corresponding second opening angle denoted by the reference f2.

2 shows a plan view of the zone filter 4 , The zone filter 4 includes in concentric arrangement a first zone Z1, which is surrounded by an annular second zone Z2. The annular second zone Z2 is in turn surrounded by an annular third zone Z3. The first zone Z1 is here permeable to infrared light in the range of 3 to 5 microns and 8 to 12 microns. The second zone Z2 is permeable to infrared light in the range of 8 to 12 microns. The third zone Z3 is impermeable to all wavelengths. The zones arranged here in one plane (with respect to the optical beam path) can also be arranged in two or different planes.

The function of the infrared camera is the following:
The zone filter 4 is disposed at a position within the imaging optics, to which usually a limiting the field of view aperture is provided. Ie. the zone filter 4 is preferably in the Fourier plane in front of the infrared sensor 5 intended.

An image B becomes when the first lens is turned on in the beam path 1 with the first lens 1 on the infrared sensor 5 displayed. Here are the first lens 1 and the zone filter 4 arranged so that the light at the first opening angle f1 on the first Z1 and second zone Z2 of the zone filter 4 falls. With the first lens 1 is an image in the wavelength range of 8 to 12 microns on the infrared sensor 5 displayed.

Will instead of the first lens 1 the second lens 9 turned on in the beam path, so is the image B at a smaller second opening angle f2 on the infrared sensor 5 displayed. The light essentially falls on the first zone Z1 of the zone filter 4 , By the second zone Z2 a wavelength range smaller than 8 microns is hidden.

In the proposed infrared camera replaces the zone filter 4 , which may be made of germanium or silicon, for example, with suitable coatings, a complicated and susceptible formed aperture with adjustable aperture. The proposed infrared camera is robust and prone to interference. It is suitable for capturing images in different infrared wavelength ranges.

LIST OF REFERENCE NUMBERS

1

first lens

2

vacuum housing

3

window

4

zone filters

5

infrared sensor

6

trim housing

7

aperture

8th

cooling device

9

second lens

A

optical axis

B

image

Z1

first zone

Z2

second zone

Z3

third zone

f1

first opening angle

f2

second opening angle

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 7157706 B2 [0002]
• US 2008/0304126 A1 [0002]

Claims (17)

Infrared detector, in which one in a vacuum housing ( 2 ) received infrared sensor ( 5 ) along an optical axis (A) with a vacuum housing ( 2 ) closing windows ( 3 ), so that an image (B) captured by an imaging optic passes through the window (FIG. 3 ) on the infrared sensor ( 5 ) is imaged, characterized in that in the beam path between the infrared sensor ( 5 ) and the window ( 3 ) a zone filter ( 4 ) in which a first zone (Z1) is transparent to light of a first wavelength range and a second zone (Z2) is transparent to light of a second wavelength range different from the first wavelength range. An infrared detector according to claim 1, wherein the second zone (Z2) surrounds the first zone (Z1). Infrared detector according to one of the preceding claims, wherein the first (Z1) and the second zone (Z2) are formed coaxially, concentrically or symmetrically. Infrared detector according to one of the preceding claims, wherein the first wavelength range is greater than the second wavelength range. Infrared detector according to one of the preceding claims, wherein the second wavelength range is included in the first wavelength range. Infrared detector according to one of the preceding claims, wherein the first wavelength range extends from 3 to 15 microns, preferably from 3 to 12 microns. An infrared detector according to claim 6, wherein a wavelength interval of more than 5 μm and less than 8 μm is excluded from the first wavelength range. Infrared detector according to one of the preceding claims, wherein the second wavelength range extends from 8 to 15 microns, preferably from 8 to 12 microns. Infrared detector according to one of the preceding claims, wherein the infrared sensor ( 5 ) in the beam path a diaphragm ( 7 ) is arranged upstream with fixed aperture. Infrared detector according to one of the preceding claims, wherein the diaphragm ( 7 ) in one the infrared sensor ( 5 ) surrounding diaphragm housing ( 6 ) is provided. Infrared detector according to one of the preceding claims, wherein the zone filter ( 4 ) the aperture ( 7 ) covers. Infrared detector according to one of the preceding claims, wherein a cooling device ( 8th ) for cooling the infrared sensor ( 5 ) and the zone filter ( 4 ) is provided. Infrared detector according to one of the preceding claims, wherein the imaging optics are a first lens ( 1 ). Infrared detector according to one of the preceding claims, wherein one of the first lens ( 1 ) different second lens ( 9 ), which simultaneously with or on the first lens ( 1 ) is switched on in the beam path. Infrared detector according to one of the preceding claims, wherein one with the first lens ( 1 ) captured image (B) substantially through the first (Z1) and the second zone (Z2) on the infrared sensor ( 5 ) is displayed. Infrared detector according to one of the preceding claims, wherein one with the second lens ( 9 ) detected image (B) substantially through the first zone (Z1) on the infrared sensor ( 5 ) is displayed. Infrared detector according to one of the preceding claims, wherein the first zone (Z1) and the second zone (Z2) are arranged in different planes.

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