KEYWORDS: Modulation transfer functions, Composites, Signal to noise ratio, Point spread functions, Optical filters, Digital filtering, Linear filtering, Error analysis, Imaging systems
The MTF test always suffered from the noises. Unfortunately, it was very difficult to eliminate the co-frequency noise, when the noise located in the sampling frequency region. Based on the previous research on the multi column realignment averaging method, a novel composite processing method was proposed to remove the noises, without losing valid information. By establishing an accurate mathematical model and benchmark, and comparing with each other under the different conditions, the composite processing method can hold the valid information and suppress noise well. The error of this method was less than 0.04, when the signal-to-noise ratio of the slanted slit image was only 10 dB. It was believed that this method would be further improved in the accuracy and robustness.
This paper introduces the influence of the frequency response of the optical eye diagram analyzer on the test results, and the common methods of the frequency response calibration of the optical eye diagram analyzer. The principle of using femtosecond laser to calibrate the filter frequency response of the optical eye diagram analyzer is analyzed. The femtosecond laser is approximated to the impact function, and the impulse response of the filter can be obtained. The frequency response of the filter is calculated by Fourier transform. A scheme of calibrating filter frequency response of optical eye diagram analyzer with femtosecond laser is proposed. The pulse width and repetition frequency of femtosecond laser are tested. The influence of the stability of femtosecond laser repetition frequency on the test results is analyzed. At the same time, this paper introduces the test results of the frequency response of calibrating the optical eye diagram analyzer by the optical heterodyne method, and comparatively analyzes the optical heterodyne method and the femtosecond laser method. The experimental results show that it is feasible to calibrate the frequency response of the photoelectric module of Oscilloscope by femtosecond laser, and the repeatability of 3dB bandwidth is less than 6%.
In this paper, a series of research on the stable output method of Mach-Zehnder frequency domain depolarization system is carried out. Based on the analysis of Mach-Zehnder frequency domain depolarization technology and DOP measurement technology, it is pointed out that the instability of DOP of the depolarization system has an adverse effect on the calibration of the DOP meter with the extremum search method. It is clear that the instability problem is mainly due to the accurate alignment deviation of optical fiber. As a result, a set of solutions to improve the stability is proposed and verified by experiments. The technical core of this scheme is to extend the SOP of the depolarization system from half range control to full range control, reduce the correlation between SOP control and power control, and overcome the problem of optical fiber axis deviation in conventional technology. Through the experimental verification, the Mach-Zehnder frequency domain depolarization system based on the scheme proposed in this paper can effectively control the stability of the DOP of the output light within ± 0.1%, which can effectively calibrate the DOP meter with the extremum search method.
Responsivity is one of the important technical parameters of the detector. With the development of ultraviolet detector technology, ultraviolet focal plane array devices have also been rapidly developed. Therefore, it is increasingly important to accurately measure the response of ultraviolet detectors. This paper analyzes the principle of UV focal plane array response measurement, uses the alternative method to measure the response of the UV focal plane array detection device, and establishes the UV focal plane array response measurement device. The results of uncertainty analysis show that the uncertainty of the UV focal plane array device response measurement system is about 4.2 %, can meet the measurement requirements.
Terahertz time-domain spectroscopy (THz-TDS) technology has developed rapidly in the past decades, and it has become an important method in the field of spectral analysis. Traditional THz-TDS can only analyze isotropic materials. But the need to add polarization analysis in THz-TDS is becoming more and more urgent. In this paper, a polarization THz-TDS system is established. The birefringence and polarization dependent loss parameters of YVO4, Iceland spar, MgF2, quartz in the terahertz band had been measured. Among them, the birefringence parameter of quartz, MgF2 and Iceland spar at 0.9 THz is in good agreement with the literature. The minimum polarization dependent loss of the four crystals between 0.2THz and 1.5THz are 3.03dB, 4.42dB, 4.4dB and 2.94dB, respectively.
The infrared small spot system is the main equipment to test the crosstalk of the infrared focal plane array device. According to the current test method can’t meet the infrared light spot characteristics of the test problem, the use of infrared imaging device scanning technology to build a small infrared light beam characteristics of the calibration System, to achieve the infrared light spot characteristics of the measurement, and the system of the uncertainty was assessed. Finally, chooses an infrared small spot optical system is used to verify the measurement uncertainty of the system. It can be seen from the data analysis that the method can measure the characteristics of the infrared light beam and meet the measurement of the infrared small spot optical system. Infrared small spot system development and infrared focal plane crosstalk test to play a certain help.
In this paper, a series of experiments on dispersion compensation in terahertz time-domain spectrometers are performed. The Influence of femtosecond laser pulse width on the performance of terahertz time-domain spectrometers is systematically studied. A terahertz time-domain spectroscopy system was constructed using fiber-coupled photoconductive antennas. Through the adjustment of the grating spacing and the replacement of different lengths of fiber cable, the laser pulse width acting on the antenna was multiplexed from 130fs to 2.46ps, and the performance of the terahertz time domain spectroscopy system under different pulse widths was tested. The experimental results show that, with the increase of the femtosecond laser pulse width, the signal intensity of the terahertz time domain waveform and the high frequency part of the terahertz spectrum decrease significantly. Quantitative comparative analysis was performed using the average signal-to-noise ratio, validating the necessity of using dispersion compensation and femtosecond laser pulse width testing in the terahertz time-domain spectroscopy system.
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.