Haitao Shi

Optical sensitivity analysis of deformed mirrors for microcantilever array IR imaging

Optical sensitivity is a major issue to improve the sensor responsivity and the spatial resolution of uncooled optomechanical focal plane arrays (FPA). The optical sensitivity is closely related to the mirror length and the undesired mirror deformation induced from the imbalanced residual stresses in different layers. In this paper, the influences of mirror length and deformation on the optical sensitivity are discussed by Fourier Optics. Theoretical analysis and experiments demonstrate that the optical sensitivity is seriously degraded by undesired mirror deformation, and that there exists an optimal mirror length which makes the optical sensitivity achieve its maximum under a certain mirror deformation. Based on the results, an optimized mirror configuration is presented to increase the optical sensitivity of substrate-free bi-material microcantilever array (SFBMA).

Design optimization and performance analysis of deformed optical readout focal plane array

An optical readout focal plane array (FPA) usually has a bent cantilever due to the micro-machining techniques. This bent morphology has a strong negative impact on optical sensitivity, which is a key factor that affects the imaging performance. In this study, an optical readout FPA with a stiffener-supported pixel is presented in order to reduce the deformation. The theoretical analysis has been developed to optimize the structure. Based on this, an FPA with a stiffener-supported pixel is fabricated. It is demonstrated that the curvature radius and optical sensitivity can increase by 5 times and 5.74 times respectively with respect to that without a stiffener. Better thermal imaging has been achieved.

Performance of an optimized substrate-free focal plane array for optical readout uncooled infrared detector

This note presents an optimized substrate-free focal plane array (FPA), which is implemented in an optical readout uncooled infrared (IR) detector. The supporting frame of such FPA is a temperature-variable one due to the large decreases in both the heat capacity and the thermal conductance. This brings a unique thermal characteristic: the supporting frame functions as a “thermal isolation” frame which reduces the thermal conductance and therefore increases the temperature change and also functions as a “thermal diffusion” frame which certainly results in the temperature prechange in the ones not absorbing IR radiation. This characterization could significantly increase the temperature change of microcantilevers and therefore improve the performance of the substrate-free FPA. In the proposed IR detector, the fabricated 160×160 FPA has an average noise equivalent temperature difference (NETD) and a response time of 330 mK and 16 ms, respectively. The performance of the IR detector theoretically increases b...

Optical sensitivity non-uniformity analysis and optimization of a tilt optical readout focal plane array

An optical readout focal plane array (FPA) usually has a differently tilted reflector/absorber at the initial state due to the micromachining technique. The angular deviation of the reflector/absorber has a strong impact on the optical sensitivity non-uniformity, which is a key factor which affects the imaging uniformity. In this study, a theoretical analysis has been developed, and it is found that the stress matching in SiO2-Aluminum (Al) bilayer leg could make a contribution towards reducing the optical sensitivity non-uniformity. Ion implantation of phosphorus (P) has been utilized to control the stress in SiO2 film. By controlling the implantation energy and dose, the stress and stress stability are modified. The optical readout FPA has been successfully fabricated with the stress-control technique based on P+ implantation. It is demonstrated that the gray response non-uniformity of optical readout FPA has decreased from 25.69% to 10.7%.

EFFECT OF REFLECTOR DEFORMATION ON OPTICAL DETECTION SENSITIVITY FOR OPTICAL READOUT INFRARED IMAGING SYSTEM: EFFECT OF REFLECTOR DEFORMATION ON OPTICAL DETECTION SENSITIVITY FOR OPTICAL READOUT INFRARED IMAGING SYSTEM

Based on the optical readout method with knife edge filter,the relationship between the optical detection sensitivity and reflector length was discussed under the circumstance that the reflector was bent.Analysis indicates that the optical sensitivity increases with the reflectors lengthening at first,then it reaches a maximum value,and then it decreases as the reflector continues to lengthen.For the reflectors with different curvature radii and lengths,analysis shows that the sensitivity will reach a maximum value when the expression L2/R=λ(L is length of reflector,R is curvature of the reflector,λ is wavelength of illumination light) is satisfied.The optical detection sensitivities of the fabricated FPAs with different pixel sizes as 200μm,120μm and 60μm were obtained experimentally.The result coincides with the theoretical analysis.