This paper presents the design, fabrication and performance of an uncooled micro-optomechanical infrared (IR) imaging system consisting of a focal-plane array (FPA) containing bi-material cantilever pixels made of silicon nitride (SiNx) and gold (Au), which serve as infrared absorbers and thermomechanical transducers. Based on wave optics, a visible optical readout system is designed to simultaneously measure the deflections of all the cantilever beams in the FPA and project the visible deflection map onto a visible charge-coupled device (CCD) imager. The IR imaging results suggest that the detection resolution of current design is 3-5 K, whereas noise analysis indicates the current resolution to be around 1 K. The noise analysis also shows that the theoretical noise-equivalent temperature difference (NETD) of the system can be below 3 mK.

/pdf/optomechanical-uncooled-infrared-imaging-system-design-2dhvofeija.pdf

Optomechanical uncooled infrared imaging system: design, microfabrication, and performance

We present a state-of-the-art overview of microthermomechanical infrared sensor technology. The working principle of this sensor is based on a bi-material actuated micromechanical deflection, generated by an induced temperature rise due to incident infrared radiation absorption. In order to generate a thermal image the thermomechanical deflections of the freestanding microstructures are read by either capacitive, piezoresistive or optical means. Research and development activities in this field began in the early 1990s. The development of this technology within the last 20 years has resulted in innovations such as uncooled multiband infrared detection, high-speed infrared sensing and uncooled THz imaging. This paper outlines representative milestones of this technology and analyses important results of notable groups. Significant activities on capacitive and optical readout techniques of thermomechanical infrared arrays are presented. Furthermore the advantages of microthermomechanical infrared sensors over current well-established uncooled infrared technologies are summarized. In conclusion the latest developments of this technology offer a highly potential solution for a variety of important energy-saving, safety and security applications.

https://www.degruyter.com/downloadpdf/j/oere.2014.22.issue-1/s11772-014-0176-0/s11772-014-0176-0.xml

Microthermomechanical infrared sensors

An uncooled infrared (IR) imaging system based on thermomechanical deformation of bi-material cantilever beams combined with optical detection of beam deflection has been developed. The focal plane array (FPA) contains 300 x 300 cantilever sensors, which are optimized to detect IR radiation in the 8-14 μm wavelength range. Noise and response analysis show that the noise-equivalent temperature difference (NETD) of the system is 200 mK using f/1 IR optics and 10 Hz frame capture rate. The NETD is found to be limited by the shot noise of the visible CCD imager used in the optical readout. Statistical correlation between two repeated tests separated by 10 minutes shows that the response of over 70 percent pixels are repeatable to within 60 percent.

Characterization and performance of optomechanical uncooled infrared imaging system

An uncooled infrared detector having an optical readout is described. Infrared heat is sensed with bimate-na! cantilevers which bend in response to temperature changes. One side of the bimaterial cantilever isan optical reflector. Visible light reflecting off the bent cantilever is detected with a CCD camera to pro-vide the sensor output. We describe this device as a micro-optomechanical infrared receiver with opticalreadoutMIRROR. Devices based upon this principle have successfully imaged infrared. Changes to thesystem are in progress to improve sensitivity. 1. INTRODUCTION Uncooled infrared detectors have captured the imagination of the thermal imaging community becausethey eliminate the need for expensive mechanical coolers requiring frequent maintenance. The leading uncooled detectors employ resistive bolometers or capacitive ferroelectric elements. Like cooled detectors,these devices require an electrical readout circuit typically made using a combination of analog and digitalCMOS circuitry.

Micro-optomechanical infrared receiver with optical readout—MIRROR

This article presents the theory and experimental results of an optical imaging technique that simultaneously measures the deflections of a focal plane array of bimaterial microcantilevers that are used as thermomechanical infrared sensors. Based on Fourier optics, this technique is used for infrared vision of room-temperature objects with a noise-equivalent temperature difference (NETD) in the range of 2-5 K. Efforts are currently underway to improve the NETD to the range of 30-50 mK.

Y . Zhao

Papers

Application of fourier optics for detecting deflections of infrared-sensing microcantilever arrays