The mid-infrared birefringence coefficients, including photoelastic coefficients, phase delay, and fast axis angle, are important indicators for evaluating infrared crystal materials. These coefficients can detect deviations introduced during optical glass processing and stress birefringence generated under external forces, which are mostly used to measure the influence of birefringence deviation of optical window under atmospheric pressure before assembly. This paper introduces a dual photoelastic modulators (PEMs) system for detecting birefringence in the near infrared to midinfrared range. The hardware of this system includes a 3390nm laser, a -45°polarizer, a 0°PEM, a +45°PEM, a 90°polarizer, a photodetector, a lock-in amplifier with filter circuit module, and a host computer, which can achieve modulation and demodulation of the polarization state of light and extraction of weak electric signal. The software interface of this system includes, data acquisition card channel setting interface, electrical signal waveform display interface and birefringence coefficient data processing interface. The polarization state analysis method using Stokes parameters and Mueller matrices, along with data processing techniques, enables automated and precise measurement of mid-infrared birefringence coefficients in crystals. Multiple sets of measurement data yield a phase delay of 9.863541 nm for a 15mm thick Si crystal and a phase delay of 8.971042 nm for a 12mm thick ZnS crystal. The repeatability of the measurement device is 0.020, and the measurement uncertainty is 0.019. This system can be extended for precision measurement of stress birefringence in multi-wavelength infrared crystals. It not only fills the gap in testing equipment for mid-infrared crystal photoelastic coefficients but also provides valuable guidance for the design, evaluation, and application of crystal stress birefringence systems.
Modulation transfer function (MTF) is one of significant parameters for designing and evaluationg an photoelectric imaging system.As the traditional MTF measurement algorithm cannot meet the need of dynamic measurement for photoelectric system. A device composed of composed of three parts, including dynamic target generation unit, carrier motion simulation unit, data processing and control unit was setup. It is found that when the platform vibrates at low frequency, the decreasing speed of the dynamic transfer function of the television imaging system increases with the increase of the vibration frequency. When the platform vibrates at high frequency, the decreasing velocity of the dynamic transfer function of the television imaging system changes very weakly with the increase of the vibration frequency of the platform. When the platform vibrates at high frequency, the fluctuation of the decreasing velocity of the dynamic transfer function of the television imaging system decreases continuously with the increase of the vibration frequency, and gradually approaches 1 when the platform is at rest1.42 times.
Modulation transfer function (MTF) is one of significant parameters for designing and evaluating an photoelectric imaging system. As the traditional MTF measurement algorithm cannot meet the need of discrete sampling characteristics for photoelectric system, an automatic interpolaton and sub-pixel matching algorithm based on slit tilting method is proposed.Through the least-square analysis of line spread function (LSF),the tilting angle can be automatically calculated, and interpolaton of sub-pixel data can be precisely reconstructed. The noise of oscillation can be effectively restrained by a hanning window function. A device composed of target generator system, off-axis reflective collimator, mechanical adjustment, electrical control system, video acquisition module and comprehensive software was setup. The validity of the method was verified by experiments. The repeatability reached 0.007。
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.