This PDF file contains the front matter associated with SPIE Proceedings Volume 13498, including the Title Page, Copyright information, Table of Contents, and Conference Committee information.

Single-point diamond cutting technology is extensively used for machining high-precision optical surfaces with microstructures. Coherence scanning interferometry (CSI), offers high measurement efficiency and can achieve sub-nanometer noise levels. Integrating CSI system in a diamond cutting machine may allow on-machine surface measurement with an extended degree of freedom by utilizing the motion axes of the machine and avoid repositioning errors of the machined part after the off-line measurement. However, environmental vibrations inside the cutting machine may introduce measurement errors. In this study, we investigate the impact of vibration on the transfer function of CSI, and develop an anti-vibration surface reconstruction algorithm for on-machine CSI measurement. The influence of high-frequency vibrations is mitigated using a specially-designed filter, while the influence of low-frequency vibrations is addressed through inverse phase compensation. This method is validated experimentally with an ultra-precision single-point diamond turning machine.

Random sphere absolute measurement is a simple and efficient method. It assumes that the mean of the surface in different regions of the test sphere necessarily converge to the ideal plane. Although a large number of experiments have verified this assumption, the relevant theory has not yet been perfected. In this study, we develop a mathematical model for the random sphere absolute measurement from the perspective of moments of random variables. It shows that the random range of the test spheres significantly affects the repeatability of measurement. Meanwhile, based on this mathematical model, we proposed the multiple sphere random theory. In the experiment, the RMS repeatability for single sphere random absolute measurements is 0.00045λ under the condition of large random range and 0.00017λ under the condition of small random range. The experiment verifies the influence of the random range on the repeatability of the measurement. Meanwhile, a multiple spheres random absolute measurement experiment was completed, which achieved a similar repeatability to the single sphere random under the condition of poorer surface quality of the test sphere and fewer averaging times. The RMS repeatability is 0.00022λ. This method greatly reduced the cost of the sphere absolute measurement.

Field Programmable Gate Array (FPGA) based Tapped Delay Line (TDL)- Time-to-Digital Converters (TDC) are widely used in photoelectric measurement due to flexible design and low cost. These types of TDCs require calibration to quantify the inconsistent bin width of the delay line for better accuracy. This paper proposes a code density method based on Geiger-Mode Avalanche Photodiode (GM-APD) avalanche signals for calibration. The paper analyzes the Poisson distribution of GM-APD’s avalanche signals. Then, using an experiment to verify that the proposed method is convenient and effective for TDL-TDC’s calibration, reduces the Differential Nonlinearity (DNL) and Integral Nonlinearity (INL) in measurement.

Target contrast is an important factor that affects the accuracy of viewing distance evaluation result of low light level device. There is a great difference between night sky spectrum and day spectrum, and the contrast of night target is different from that of day, so it is very important to measure the night target contrast accurately. Based on the basic concept of contrast and the relationship between brightness and illumination, and according to the high matching between the spectral response characteristic of the 3rd image intensifier and starlight spectrum, the way to measure the night target contrast by image intensified CMOS is proposed in this paper. And a measuring device calibrated by standard light source of 2856K color temperature in the laboratory is founded. Then, the device calibrated is used to measure the target contrast in urban. The results show that the deviation of the target contrast measuring device based on image intensified CMOS is less than 6.5% after laboratory calibration, the target contrast measurement results in urban are consistent with the visual observation results, and the target contrast measurement results are reliable. The results in this paper can provide an effective measurement method to ensure the accuracy of viewing distance evaluation results of low light level device.

In phase-sensitive optical time domain reflectometer (Φ-OTDR), the existence of interference fading signal leads to misjudgment and missing judgment in vibration sensing. In this paper, a fading recognition model of back propagation (BP) neural network is constructed, features are extracted from beat frequency generated based on frequency shift delay loop. A fading recognition accuracy of 91.82% is achieved. Rotated-vector-sum algorithm is introduced to aggregate signal labelled non-fading. Vibration location and phase demodulation is realized and on this basis, this method improves the interference fading suppression probability.

Accurate and efficient focal plane testing is the basis for evaluating Infrared focal plane arrays(IRFPA). In this paper, an all-in-one test system is developed to accurately and efficiently evaluate the performance of focal plane devices and ensure reliability in practical applications for short-wave infrared focal plane devices from 900 nm to 1700 nm. The all-in-one machine is paired with software, the test data is automatically exported. Through the test and verification of an InGaAs PIN focal plane detector, the key data such as responsivity, photoresponse non-uniformity(PRNU), responsivity and quantum efficiency were obtained, and the test results were given and analyzed. At the same time, the influence of temperature on the dark current is tested. The ambient temperature of -20°C to 30°C is suitable for the device. The experimental results practice the effectiveness of the test system.

Due to its dynamic and non-invasive characteristics, it is difficult to obtain stable and accurate measurement results using contact thermocouple temperature measurement. The temperature measurement accuracy of infrared thermal imaging cameras in non-invasive temperature measurement is affected by factors such as flame emissivity and radiation path attenuation, and there is also a large temperature measurement error. Among them, the colorimetric thermometer can avoid the influence of the emissivity of the measured target, and has the advantages of high accuracy, strong anti-interference ability, and wide temperature measurement range. However, in engineering use, due to the energy zero points set by long-wave and short-wave radiation, the data calculated and output based on the principle of colorimetric thermometry has a "temperature breakpoint" phenomenon. Based on this kind of engineering situation, this paper proposes a temperature calibration method for colorimetric thermometers and a temperature data breakpoint repair method. The actual measurement and verification experiment of a high-temperature blackbody furnace has proven the effectiveness of this temperature data breakpoint repair method, providing more accurate temperature data values for experiments such as flame temperature testing.

The accurate characterization of engine blade strain field and its change history is of great significance to ensure the safety of aircraft service and guide the material selection and structural design of the new generation of blades. However, because of its work in the complex environment of space limitation and multi-physical field coupling, the traditional detection methods are not applicable, and there is an urgent need to develop a three-dimensional visual imaging technology with simple structure and reliable performance. In this paper, a digital image correlation measurement method based on a single color camera is proposed, using specially designed filters and imaging lenses to cooperate with each other to ensure the spatial resolution of the acquired image while reducing the cost, and the related experiments confirm the effectiveness of this scheme in improving the accuracy of engine blade deformation measurement. It should be noted that the method is equally beneficial to other target reconstruction and scene perception problems in other complex environments and restricted spaces.

The ultraviolet (UV) light at 222nm can be absorbed by microbial DNA and RNA, changing their structures and achieving the effect of sterilization. Unlike commonly used UVC light, 222nm UV light is harmless to humans, making it a crucial role in disinfection and sterilization. Consequently, calibration of 222nm UV radiometers is also of great significance. In this paper, according to the characteristics of KrCl excimer lamp, the effects of different types of filters on the spectrum of sterilization lamp are studied, as well as the calibration method of UV radiometer, and the measurement uncertainty is evaluated.

This paper reported the research and establishment of a set of spectral retro-reflection standard measurement and calibration device. Based on the physical definition and measurement principle of spectral retro-reflection standard, a calibration device that can provide stable and reliable measurement results in the spectral band of 380nm - 780nm and under key retro-reflection measurement geometric conditions (incident angle: -4° - 30°, observation angle: 0.2° - 1°) was constructed and implemented through the precise optical path design integrating a stable light source and optical fiber spectrometer. Experiments showed that the device performed well in measurement accuracy and consistency. Measurement verification experiments were carried out with the national retro-reflection coefficient calibration device, and the optimal consistency measurement results for the same sample under characteristic conditions were better than 1.0%. This work has positive significance for further promoting the application of retroreflective materials in transportation, safety, intelligent connected vehicles and other fields.

The test targets for the perception function of autonomous vehicles are crucial equipment for evaluating the reliability and safety of automotive ADAS systems. However, due to the lack of effective regulatory technical means, a large number of obviously deformed and damaged targets are still used repeatedly and for extended periods until they are completely damaged during testing. The test results obtained using poor-quality or even unqualified targets pose potential safety risks that cannot be ignored for subsequent open road testing and consumer use, highlighting the urgent need to establish practical and effective quantitative calibration methods for the optical characteristics of these targets. In response to this urgent need, this paper studies and establishes a calibration method for the optical spatial distribution reflection characteristics of typical humanoid targets. Furthermore, based on a novel three-dimensional polyhedral standard body, industrial cameras, and a bidirectional reflection distribution function analysis algorithm using the photographic method, a set of traceable on-site calibration devices is constructed. This has positive significance for establishing and improving relevant regulatory technical means, evaluation standards, and technical specifications, as well as exploring traceable technology for supervising the entire life cycle of test target quality.

The operation principle of scanning DBR laser was introduced and its multi-channel driving parameters was summarized. Based on FPGA, a multi-channel high-speed and high-precision current drive circuit was designed and fabricated, a scanning laser tuning characteristic testing system was integrated, and parameter control and testing programs were designed to achieve automatic testing. Experimental tests have proven that the developed testing system can well meet the testing requirements of scanning lasers, with a simple structure, high accuracy, and fast speed.

The polyvinyl alcohol (PVA) with non-toxic and environmentally friendly properties has good temperature and humidity sensitivity. The refractive index (RI) is affected by both temperature and humidity. However, the high-temperature irreversibility and the moisture loss of PVA limit its application in temperature sensing. How to effectively reduce the temperature measurement errors caused by moisture loss and cross-sensitivity is an effective way to obtain a highly sensitive temperature sensor based on PVA. In this work, a PVA partly coated singlemode multi-mode single-mode (SMS) fiber temperature sensor is demonstrated. The multi-mode interference (MMI) effect in the SMS fiber structure provides measurable characteristic spectra for temperature sensing. The cross-sensitivity between humidity and temperature in PVA can be effectively reduced by using capillary sealing to prevent water loss. At the same time, partially stripped the coating layer of the coreless fiber to avoid high transmission loss caused by high RI coating. This partly coated structure can reduce dependence on measured light intensity. Experimental measurements indicated that the sensitivity of the sensor is 12.9264nm/°C, which is suitable for measuring small temperature changes with an accuracy of about 1.547 × 10⁻³ °C.

With the development of precision manufacturing technology, the demand for fast measurement of surface morphology and structure at the micro and nano scale is becoming increasingly important. Laser scanning confocal microscopy is widely used for morphology characterization of micro and nano structures due to its high resolution and no need for special sample processing. In order to ensure the measurement accuracy of the measured sample morphology, confocal microscopy generally uses smaller axial scanning steps and more scanning layers, which increases the measurement time; And for samples with a measured area exceeding the transverse scanning field of view of the galvanometer, multiple fields of view need to be measured and spliced to obtain a complete surface morphology. Therefore, the measurement time is multiplied, which is difficult to meet the needs of large-scale rapid detection and iteration of micro and nano processed products in the field of precision manufacturing. In order to achieve fast and large range measurement of micro/nano structure samples, this paper proposes a method of using the linear region of laser scanning transverse differential confocal curve to quickly measure the surface morphology of a field of view, and combining with displacement stage scanning, feature point detection, and morphology image stitching to achieve rapid measurement of large range micro/nano structure morphology. This method uses a galvanometer to quickly scan and obtain the front and rear focal light intensity signals 𝐼_𝐴 and 𝐼_𝐵. The linear region near the zero point of the differential confocal intensity curve are fitted using a cubic polynomial to obtain a linear sensing curve with good linearity and an accurate correspondence between the zero point and the height of the sample. This enables the fast acquisition of micro/nano structure surface morphology within the effective measurement range of the sensing curve without axial scanning. As for samples with heights exceeding the effective measurement range of the linear sensing curve, measurements can be completed quickly with a larger axial scanning step and fewer scanning layers compared to confocal microscopy. For large range samples, this method first quickly measures the surface morphology within a horizontal field of view, then sets a certain proportion of overlapping areas, switches to a new measurement field by the XY lateral displacement stage, and sequentially completes the scanning of multiple sub areas of the samples. Finally, the SURF feature point detection algorithm is used to extract the feature points of the overlapping areas for morphology map stitching, achieving high-precision and rapid measurement of large range micro/nano structures. The measurement method proposed in this article has fast speed and high accuracy, providing an efficient detection method for the field of precision manufacturing.

In simultaneous dual-wavelength interferometry (SDWI), we present a dual-wavelength squeezing interferometry for the extended measuring range. Combining with single-wavelength interferometric conjugate complex functions coupling and double phase shift strategy, the proposed method can retrieve the longer synthetic-wavelength phase with the lower spatial carrier. Based on the novel double phase shift strategy, several groups of phase-shift dual-wavelength interferogram are acquired with every four frames in each group. And the phase-shift step is designed as π/2 at one single wavelength in each group, while π/2 at synthetic wavelength between the adjacent groups. For the dual-wavelength squeezing interferometry, the temporal phase shift among each group is converted into spatial carrier in the generated single spatialtemporal fringe (STF). Therefore, it does not need extra spatial carrier in the initial dual-wavelength interferogram for the spectral separation. The single-wavelength interferometric complex functions could be easily obtained by the Fourier transform and appropriate spectral filter performed on the dual-wavelength STF. The obtained single-wavelength interferometric conjugate complex functions are coupled by multiplication to extract the needed synthetic-wavelength interferogram from every group. And then the extracted synthetic-wavelength interferogram from each group with π/2 phase shift are demodulated by conventional phase-shift algorithm directly. Finally, the method is tested in experiment data for recovering phase from dual-wavelength fringe patterns with closed fringes.