Search Results (3)

For gravitational wave observation, an optical design of the telescope has been implemented to perfectly match the laser interferometry system, and stray light analysis is used to quantify the impact of mirror roughness noise on interferometric measurement sensitivity. An off-axis six-mirror afocal optical design, comprising a parabolic primary, hyperbolic secondary and plane-parabolic collimation group, delivers an optical system with a 400 mm entrance pupil, 100× expansion ratio, and λ/30@1064 nm Root Mean Square (RMS) wavefront quality. To obtain a feasible exit pupil position which can easily integrate the laser interferometer, the theoretical mathematical relationships among the exit pupil position, primary–secondary mirror spacing, and radius of curvature of the secondary mirror and the sixth mirror are derived. Accordingly, the effective exit pupil position is extended to 174 mm to match the laser interferometer. The sixth mirror is the primary source of backscattered light. With the RMS roughness of the primary, secondary, and three folding mirrors set to 6.4 Å, 1.6 Å, and 3.7 Å, respectively, the Point Source Transmittance (PST) value can be kept below 3.6 × 10⁻¹⁰ when the RMS roughness of the sixth mirror is less than 1.1 Å. Tolerance analysis is carried out to obtain the feasible engineering distribution of optical parameters, and the statistical results show that the system RMS wavefront error is smaller than 0.01λ@1064 nm. Full article

Lenses/mirrors with fast data acquisition speeds and extended focal depths have practical importance in terahertz (THz) imaging systems. Thus, a high-speed 600 GHz-band THz imaging scanner system with enhanced focal depth is presented in this work. A polygon mirror with a 250 Hz scanning frequency and an integrated off-axis parabolic (OAP) mirror with an ~170 mm focal depth were employed for 2D imaging. The simulation and experimental results show that a spatial resolution of ~2 mm can be achieved as the imaging distance varies from ~85 to 255 mm. The proposed system was applied to image a hidden metal object as a potential security application, demonstrating that this system can image targets with an enhanced focal depth. Full article

This paper presents a miniaturized, broadband near-infrared (NIR) spectrometer with a flame-retardant 4 (FR4)-based scanning micrograte. A 90° off-axis parabolic mirror and a crossed Czerny–Turner structure were used for creating an astigmatism-free optical system design. The optical system of the spectrometer consists of a 90° off-axis parabolic mirror, an FR4-based scanning micrograte, and a two-color indium gallium arsenide (InGaAs) diode with a crossed Czerny–Turner structure optical design. We used a wide exit slit and an off-axis parabolic mirror with a short focal length to improve the signal-to-noise ratio (SNR) of the full spectrum. We enabled a miniaturized design for the spectrometer by utilizing a novel FR4 micrograte for spectral dispersion and spatial scanning. The spectrometer can detect the full near-infrared spectrum while only using a two-color InGaAs diode, and thus, the grating scanning angle of this spectrometer is small when compared to a dual-detector-based spectrometer. In addition, the angle signal can be obtained through an angle sensor, which is integrated into the scanning micrograte. The real-time angle signal is used to form a closed-loop control over the scanning micrograte and calibrate the spectral signal. Finally, a series of tests was performed. The experimental results showed that the spectrometer has a working wavelength range of 800–2500 nm. The resolution is 10 nm at a wavelength range of 800–1650 nm and 15 nm at a wavelength range of 1650–2500 nm. Similarly, the stability of these two wavelength ranges is better than ±1 nm and ±2 nm, respectively. The spectrometer’s volume is 80 × 75 × 65 mm³ and its weight is 0.5 kg. The maximum spectral fluctuation does not exceed 1.5% and the signal-to-noise ratio is 284 after only one instance of averaging. Full article