Spectral imaging of moving objects with a stare down camera

• US 20110228116A1
• Filed: 03/16/2010
• Published: 09/22/2011
• Est. Priority Date: 03/16/2010
• Status: Active Grant

• Current Assignee: Opotek, LLC
• Original Assignee: Eli Margalith
• Inventors: Margalith, Eli
• Granted Patent: US 8,687,055 B2
• Time in Patent Office: Days
• US Class Current: 348/222.1
• CPC Class Codes: G01J 2003/1282 Spectrum tailoring
• CPC Class Codes: G01J 3/2803 using photoelectric array detector
• CPC Class Codes: G01N 21/255 Details, e.g. use of specially adapted sources, lighting or optical systems
• CPC Class Codes: G01N 21/39 using tunable lasers
• CPC Class Codes: G01N 21/8901 Optical details; Scanning details per se G02B
• CPC Class Codes: G01N 21/8903 using a multiple detector array
• CPC Class Codes: G01N 21/93 Detection standards; Calibrating baseline adjustment, drift correction

Abstract

A spectral imaging system for collecting spectral information of a two dimensional heterogeneous objects while in motion relative to the imaging system without the use of a spectrograph, filters or any dispersive optics. The system includes a pulsed light source tunable in wavelength for producing short pulses of wavelength tuned light at a plurality of selected narrow band wavelengths within a spectral range and one or more optical components for conveying or directing the short pulses of light to a two dimensional region that is substantially stationary with respect to the imaging system and through which the two dimensional target is moving. The system also includes a many pixel camera synchronized with the tunable pulsed light source. The camera is adapted to detect light in the selected narrow band wavelengths produced by the tunable pulsed light source and reflected from or transmitted through the two dimensional target in motion relative to the imaging system and to provide image frame information with each frame at a defined wavelength band. A processor processes information from said tunable light source and said camera and to produce multi-spectral images of the target.

Claims

1. A spectral imaging system for collecting spectral information of a two dimensional objects in motion relative to the imaging system, said system comprising:

A) a pulsed light source tunable in wavelength for producing short pulses of wavelength tuned light at a plurality of selected narrow band wavelengths within a spectral range,

B) one or more optical components for conveying or directing said short pulses of light to a two dimensional region that is substantially stationary with respect to the imaging system and through which the two dimensional objects are moving relative to the imaging system, and

C) a camera synchronized with said tunable pulsed light source and comprising a many pixel array detector, said camera being adapted to;

i) detect light in the selected narrow band wavelengths produced by said tunable pulsed light source and reflected from or transmitted through said two dimensional objects in motion relative to the imaging system and

ii) provide a plurality of image frames with each frame at a defined wavelength band,

D) a processor adapted to process information from said tunable light source and said camera and to produce multi-spectral images of said objects from said information.

2. The spectral imaging system as in claim 1 wherein said tunable light source comprised an optical parametric oscillator driven by a short pulse laser.

3. The spectral imaging system as in claim 1 wherein the tunable light source and camera are stationary and positioned above the moving objects.

4. The spectral imaging system as in claim 1 wherein many pixel array detector is a near infrared focal plane array detector.

5. The device as in claim 1 wherein said one or more optical components for conveying or directing said short pulses of light to said target is one or more optical fibers.

6. The device as in claim 1 wherein said one or more optical components for conveying or directing said short pulses of light to said target comprises refractive or reflective optical elements.

7. The device as in claim 2 wherein said camera is a gated camera synchronized with said optical parametric oscillator to maximize signal to noise ratio.

8. The device as in claim 2 wherein the optical parametric oscillator comprises a bulk non-linear crystal.

9. The device as in claim 2 wherein the optical parametric oscillator comprises a periodically polled non-linear crystal.

10. The device as in claim 1 wherein said camera is positioned to monitor reflections from said objects.

11. The device as in claim 1 wherein said camera is positioned to monitor transmissions through said objects.

12. The device as in claim 1 wherein said object is a pharmaceutical product.

13. The device as in claim 1 wherein said objects is an array of samples containing identical or different materials.

14. The system as in claim 1 wherein system parameters are defined as follows:

Np=number of pixels in the motion direction

Nps=number of pixels in the strip'"'"'s width

Ns=number of strips in the field of view

PIX=Virtual pixel dimensions

PRR=pulse repletion rate of the laser

V=target speed (conveyor belt speed)=

Δ

λ

=Wavelength range

#F=number of frames (spectral bands in the spectral data)

SR=Spectral resolution

Ws=Strip width,

and the system parameters are adjusted such that each strip is exposed only once to each wavelength as it travels across the target area so the number of pulses that a strip is exposed to is equal to number strips in the target area, which is also equal to the number of data points (#F) in the collected spectral data, so;

15. The system as in claim 12 wherein the strip width is as narrow as a single pixel.

16. The system as in claim 12 wherein the strip width is wider than a single pixel.

17. The system as in claim 12 wherein the system is adapted such that the wavelength tuning scans over an entire wavelength range in the same time that it takes for an object to travel across the target area so that the time to complete the scan is provided by the following equation:

18. The system as in claim 1 and further comprising at least one reflectance standard placed in the field of view of the camera wherein said processor is adapted to utilize light signals collected by said camera reflected from said at least one reflectance standard to normalize other collected data.

19. The system as in claim 1 and further comprising optics to sample the intensity of the illuminating beam using a reflectance standard and a detector utilize light signals reflected from said reflectance standard to normalize other collected data.

20. The system as in claim 1 wherein said processor is adapted to store pixel-by-pixel calibration data in order to correct for variation in pixel response from target data.