Specification for Thermographic Video Camera.docx

Specification for Thermographic Video Camera Prepared by: Jonathan Williams, AD/TSD

Introduction The Mu2e production target design effort requires a thermographic video camera for prototype thermal test monitoring at a high level of accuracy and detail to validate target performance and guarantee particle production yield for timely completion of the experiment. This specification covers the minimum requirements for a camera that meets the needs of the test series and project.

Performance Requirements The camera shall provide a minimum image resolution in horizontal and vertical directions of 640 by 512 pixels, respectively, with a noise-equivalent temperature difference (NETD) of 20 millikelvin (mK) or less.

Accuracy of the camera shall be +/- 1C. This may be relaxed to +/- 1% of full range at the high end of the measurement range or for high-temperature calibrations beyond the listed standard or default range.

The frame rate with full-frame capture shall be 60 frames per second or greater. Windowing of the sensor (operating at a reduced image size to operate at a higher frame rate) is viewed as an added benefit, but 640x512 minimum resolution at minimum 60 fps must be achievable without windowing.

The camera sensor shall be sensitive to the medium-wave infrared (MWIR) band of 3 to 5 microns. Broadband MWIR (for example, 1 to 5 micron) sensors are not necessarily an improvement for this measurement application and may be more expensive, and the specific compatibility of any 1-5 micron system must be evaluated for the use case of viewing through a sapphire window into a vacuum chamber and for open-air measurement. A 1-5 micron system with optional filtering to 3-5 microns is a plausible solution. A 3-5 micron wavelength compatibility requires no additional verification by the requestor, and is strongly preferred. Other wavelength bands that exclude 3-5 microns such as long wave infrared (e.g., a sub-band of 7-10 microns) are not permissible, as these are not compatible with the transmittance of our chamber windows.

At minimum, the camera shall be capable of imaging temperatures within the range of 20 Celsius to 1300 Celsius. If any calibrations, wavelength-specific optics, or filters are required to observe this temperature range, those must be included as part of the deliverables. A wider temperature range within the same optics/calibration combination (to avoid frequent recalibration or optics changes across various test setups) is viewed as a strong benefit.

The camera is intended to be used at a range of working distances between 0.2 meters and 1 meter. Lens focusing must be able to accommodate this range. Manual focusing is required at minimum, motorized focus is permissible. Fixed focus lenses (nonadjustable by the end user) do not meet this specification. Notwithstanding this, other lenses shall allow for imaging at greater distances if desired later on.

The camera shall be capable of imaging a 75 mm long target at 0.2 m working distance within the long axis of the frame, with a pixel size on target of 0.15 mm or smaller. The smallest f-stop number (widest aperture) feasible within a manufacturer’s standard offerings is preferred, as this allows more light to reach the sensor for better sensitivity. If the proposed f-number is greater than f/4 (referring to a narrower aperture), the manufacturer must make particularly certain the camera meets all the accuracy and sensitivity specifications described above.

For example, one satisfactory implementation of this requirement (as estimated by one vendor) is to use a f/2.5 focal system with a 25 mm lens and a 640x512 px sensor with 15 micron pixel pitch on the sensor for the above imaging condition. Preference would be assigned to the f/2.5 system over an available f/4 system, and an f/5.6 system would be impermissible.

Note: This example does not replace the working distance, pixel-size-on-target, or sensitivity requirements described above, but represents one solution presented by one vendor as meeting these requirements. Other focal systems and lenses are not strictly incompatible with this specification, but must be evaluated against the target size criterion above. A suitable vendor will provide documentation of the imaging size at the distances of interest.

The camera lenses shall be removable and user-replaceable with other focal lengths.

The camera shall be compatible with the GenICam interface standard for control over gigabit Ethernet.

The camera shall provide separate ports for triggering and video output in addition to the ethernet port required for GenICam.

All necessary power supplies required to operate the camera shall be provided as part of the deliverables.

The camera shall be packaged for shipment to prevent damage, and delivered in working order to Fermilab.

Thermal analysis software compatible with the camera is desired, but any software must be a non-subscription perpetual license that is transferable between computers at the convenience of the operator.

Mechanical Requirements The camera shall be operable in a general industrial shop environment, excluding hazardous environment conditions such as combustible atmospheres. A suggested operating temperature range is -40 C to 50 C, but this is expected to vary slightly between manufacturers.

Any cooling required by the imaging sensor must be integral to the camera system (e.g., built-in closed-cycle cryocoolers or fans) and not provided by an external device (such as an external industrial water chiller). In particular, the camera shall NOT require external cryogenic cooling, including but not limited to liquid nitrogen in an open cycle.

The camera shall be operable in any orientation.

The camera shall provide a mounting plate compatible with typical camera tripods and screw mounts (e.g., ¼”-20, 3/8”-16, and/or #10-24 screw mount patterns).

All other considerations being held equal, and in the case of equal or near-equal sensor performance, a camera with a smaller mechanical footprint or envelope is preferred.