Imaging pyrometer

• US 6,758,595 B2
• Filed: 09/13/2002
• Issued: 07/06/2004
• Est. Priority Date: 03/13/2000
• Status: Expired due to Fees

• Current Assignee: CSEM Centre Suisse D'Electronique et de Microtechnique SA
• Original Assignee: CSEM Centre Suisse D'Electronique et de Microtechnique SA
• Inventors: Seitz, Peter
• Primary Examiner(s): Fulton, Christopher W.
• Assistant Examiner(s): Jagan, Mirellys
• Application Number:
  US10/221,639
• Publication Number:
  US 20030108083A1
• Time in Patent Office: 662 Days
• Field of Search: 374/137, 374/141, 374/124, 374/121, 374/120, 250/332, 250/339.05, 250/330, 250/339.02, 250/338.3
• US Class Current: 374/137
• CPC Class Codes: G01J 2005/0077 Imaging
• CPC Class Codes: G01J 3/36 Investigating two or more bands of a spectrum by separate detectors
• CPC Class Codes: G01J 5/08 Optical arrangements
• CPC Class Codes: G01J 5/0801 Means for wavelength selection or discrimination
• CPC Class Codes: G01J 5/0846 having multiple detectors for performing different types of detection, e.g. using radiometry and reflectometry channels
• CPC Class Codes: G01J 5/602 using selective, monochromatic or bandpass filtering
• CPC Class Codes: H04N 23/11 for generating image signals from visible and infrared light wavelengths
• CPC Class Codes: H04N 5/33 Transforming infrared radiation cameras or camera modules for generating image signals from infrared radiation H04N23/20; circuitry of SSIS for transforming infrared radiation into image signals H04N25/20

Abstract

In the imaging pyrometer, at least three types of pixels (L, S, V) for sensing electromagnetic radiation in at least three different spectral ranges are arranged in a mosaic pattern. In a neighborhood, there are two types of pixels with relatively narrow spectral sensitivity ranges in the infrared (IR), a first one (L) for sensing longer IR wavelengths and the other one (S) for shorter IR wavelengths. Additionally, there is a third pixel type (V) present for receiving electromagnetic radiation in a broader band such as the visible part of the electromagnetic spectrum. This is preferably realized by placing a mosaic filter pattern directly on pixels of an appropriate optoelectronic image sensor, for example by evaporation and photolithographic definition. The pyrometer makes it possible to measure two images of a scene simultaneously and in perfect geometric registration: a reliable temperature map, based on the two-wavelength pyrometric measurement technique, and a high-resolution picture of the scene, for example in the visible spectral range. The dynamic range for the temperature map measurement and the simultaneous picture acquisition are be increased compared to the prior art, so that both images are acquired under favorable signal-to-noise conditions, and the measurable temperature range between about 350° C. and several 1000° C. is accessible without additional neutral density filters or aperture stops.

Claims

1. A method for simultaneously determining surface temperature distributions (x,y)) and images of remote objects, comprising the steps of:

generating one single image of said objects,

sensing said image essentially simultaneously in a first infrared spectral range, in a second infrared spectral range, which is different from said first infrared spectral range, and in at least one further spectral range, which is different from said first and second infrared spectral ranges, and

determining a surface the temperature distribution ((x,y)) from said images sensed in said first and second infrared spectral ranges, wherein a visual image (l(x,y)) is determined from said image or images sensed in said at least one further spectral range without being influenced by images sensed in said first and second infrared spectral ranges.

2. The method according to claim 1, wherein said at least one further spectral range lies within or comprises a visible part of the electromagnetic spectrum.

4. The method according to claim 1, wherein the objects are illuminated by light with wavelengths that are at least partially contained in said at least one further spectral range.

5. The method according to claim 1, wherein said image is sensed by an optoelectronic sensor (1) with a plurality of pixels, each pixel sensing with an exposure time, and the exposure times are chosen in dependence upon a radiation level of said image.

6. The method according to claim 5, wherein for at least two different pixels the exposure times for sensing are set individually.

7. The method according to claim 6, wherein said pixels are arranged in rows and columns and for each row, each column or each pixel the exposure times are set individually.

8. Use of the method according to claim 1, in laser welding, laser drilling or cutting, gas or electric welding, hot-air fusion of plastic materials, combustion process monitoring, combustion motor optimization, monitoring of heat treatment or in glass, metal or ceramic processing.

3. The method according to claim 3, wherein at least two images are sensed in two successive readouts and an exposure, a readout window, a readout speed and/or a dynamic range are varied from one readout to the other.

9. An imaging pyrometer for simultaneously determining surface temperature distributions ((x,y)) and images of remote objects, comprising:

an optoelectronic sensor (1) with a plurality of pixels of at least three different types (L, S, V) for sensing electromagnetic radiation whereof

a first pixel type (L) is designed for sensing in a first infrared spectral range a second pixel type (S) is designed for sensing in a second infrared spectral range, which is different from said first infrared spectral range, and,

at least one further pixel type (V) is designed for sensing in at least a further spectral range, which is different from said first and said second infrared spectral range,

means (5) for determining a temperature distribution ((x,y)) from output signals of pixels of said first (L) and second (S) type, wherein the imaging pyrometer comprises means (5) for determining a visual image (l(x,y)) from output signals of pixels of said at least one further pixel type (V) without being influenced by the output signals of the pixels of said first (L) and second (S) pixel types, and

the first, second and at least one further pixel types (L, S, V) are arranged in a mosaic pattern on said optoelectronic sensor.

10. The imaging pyrometer according to claim 9, wherein said at least one further pixel type (V) is senses a visible part of the electromagnetic spectrum.

11. The imaging pyrometer according to claim 9, wherein a surface density of said at least one further pixel type (V) is larger than a surface density of said first pixel type (L) and larger than a surface density of said second pixel type (S).

12. The imaging pyrometer according to claim 9, wherein at least two of said first, second, and at least one further pixel type (L,S,V), comprise filters for electromagnetic radiation, said filters being selected from the group consisting of dielectric layer stacks, dye filters, and diffractive filters.

13. The imaging pyrometer according to claim 12, wherein said first pixel type (L) comprises a first narrow-band transmission filter having a central wavelength (λ

_L)of 1.06 μ

m and a spectral width of about 0.07 μ

m, and said second pixel type (S) comprises a second narrow-band transmission filter having a central wavelength (λ

s) of 0.99 μ

m and a spectral width of about 0.07 μ

m.

14. The imaging pyrometer according to claim 9, wherein said mosaic pattern consists of a periodic repetition of a unit cell, which comprises all pixel types (L, S, V) involved in the pyrometer.

15. The imaging pyrometer according to claim 14, wherein said unit cell is a square of 2×

2 pixels, two diagonally arranged pixels of the unit cell being of said first pixel type (L) and of said second pixel type (S), respectively, and the other two pixels being of said at least one further pixel type (V, V₁, V₂).

16. The imaging pyrometer according to claim 9, wherein said optoelectronic sensor is a solid-state image sensor of technology selected from the group consisting of:

CCD, CMOS, and APS.

17. The imaging pyrometer according to claim 16, wherein said optoelectronic sensor is a CMOS APS sensor comprising a pixel with a photodiode (11), said photodiode (11) being connected to a source follower transistor (12) and, via a reset transistor (15), to a reference voltage (V_DD), and wherein said follower transistor (12) is connected to a load transistor via a row select transistor (13).

18. The imaging pyrometer according to claim 9, wherein each pixel senses impinging radiation during an exposure time, and the imaging pyrometer additionally comprises means (15) for setting the exposure times of said pixels in dependence of a radiation level impinging on said pixels.

19. The imaging pyrometer according to claim 18, comprising means (15) for individually setting the exposure times for at least two different pixels.

20. The imaging pyrometer according to claim 19, wherein said pixels are arranged in rows and columns and the imaging pyrometer comprises means (15) for individually setting the exposure times for each row, each column or each pixel.

21. Use of the imaging pyrometer according to claim 9 in laser welding, laser drilling or cutting, gas or electric welding, hot-air fusion of plastic materials, combustion process monitoring, combustion motor optimization, monitoring of heat treatment or in glass, metal or ceramic processing.