scholarly journals Round robin comparison study on the form measurement of optical freeform surfaces

2020 ◽  
Vol 16 (1) ◽  
Author(s):  
Ines Fortmeier ◽  
Reyko Schachtschneider ◽  
Vit Ledl ◽  
Ondrej Matousek ◽  
Jens Siepmann ◽  
...  
Keyword(s):  
Round Robin ◽  
Measuring Instruments ◽  
Freeform Surfaces ◽  
Optical Surfaces ◽  
The Status ◽  
Metrology Research ◽  
Optical Freeform Surfaces ◽  
Best Fit ◽  
Comparison Measurements ◽  
Stable Material

AbstractA round robin comparison of freeform form measurements was carried out by the project partners and stakeholders of a European metrology research project. Altogether six measuring instruments were considered: five different (pointwise and areal) optical devices and one tactile device. Three optical freeform surfaces were used for the comparison measurements, where two specimens were measured by five instruments and one specimen by four instruments. In this paper, the evaluation methods and results of this round robin are presented for the three freeform surfaces made from a temperature-stable material, Super Invar ®. The freeforms had diameters of 40 mm, 50 mm and 100 mm and best-fit radii of 39.75 mm (convex), 40.9 mm (convex) and 423.5 mm (concave). For comparison, the bilateral pointwise differences between the available measurements were calculated. The root-mean-square values of these differences ranged from 15 nm to 110 nm (neglecting spherical contributions) and provided an insight into the status of typical freeform measurement capabilities for optical surfaces.

scholarly journals Movements of the Eastern Ribbonsnake (Thamnophis sauritus) in Nova Scotia

2016 ◽  
Vol 129 (4) ◽  
pp. 379
Author(s):  
T. L. Imlay ◽  
J. Saroli ◽  
T. B. Herman ◽  
S. W. Mockford
Keyword(s):  
Nova Scotia ◽  
Annual Variation ◽  
Prey Availability ◽  
Home Range Size ◽  
Water Levels ◽  
Suitable Habitat ◽  
Home Ranges ◽  
Daily Movement ◽  
The Status ◽  
Best Fit

The disjunct Eastern Ribbonsnake (Thamnophis sauritus) population in southwest Nova Scotia is listed as “threatened” by the committee on the Status of Endangered Wildlife in Canada. A study of the movements of the species at two lakeshore locations known to support a high density of Eastern Ribbonsnakes was undertaken in 2007 and 2008. Average seasonal movements at both sites ranged from 17 m to 84 m for juvenile snakes and 21 m to 130 m for adults; one neonate was recaptured during the study after travelling 32 m. The maximum distance travelled by an individual snake was 391 m in one season. The best-fit model to explain differences in daily movement patterns included year (P = 0.041), indicating that there is annual variation in the movements of this species. Low recapture rates precluded accurate estimates of home-range size, which varied roughly from 0.16 ha to 0.78 ha. Both movements and home ranges were larger than previously documented in Nova Scotia, but maximum distances travelled were consistent with a previous study in Michigan. Most documented movements were along the lakeshore within contiguous, suitable habitat. More work is needed to understand the frequency of large movements and triggers that initiate movements, e.g., changes in water levels, habitat suitability, or prey availability.

Designing optical freeform surfaces for extended sources

2013 ◽  
Author(s):  
Rolf Wester ◽  
Gideon Müller ◽  
Michael Berens ◽  
Jochen Stollenwerk ◽  
Peter Loosen
Keyword(s):  
Freeform Surfaces ◽  
Extended Sources ◽  
Optical Freeform Surfaces

Inspection Technology for F-Theta Lens: Practices and Discussions

2007 ◽  
Vol 364-366 ◽  
pp. 1191-1196 ◽  
Author(s):  
Hua Li ◽  
Suet To ◽  
Ling Bao Kong ◽  
Chi Fai Cheung ◽  
Wing Bun Lee
Keyword(s):  
Measurement Methods ◽  
Freeform Surface ◽  
Measurement Technology ◽  
Measuring Instruments ◽  
Freeform Surfaces ◽  
Existing Problems ◽  
Laser Scanners ◽  
Pros And Cons ◽  
Lens Surface

This paper presents the inspection technology for a freeform surface component which is named F-theta lens. F-theta lens is widely used in laser scanners, printers, etc. Freeform characterization is one of the main approaches to verify the manufacturing precision of freeform surface. At present, there is still a lack of techniques for the characterization of freeform surfaces. This study aimed to explore some approaches to inspect freeform surfaces. Two types of measurement methods, namely contact and non-contact measurement methods, are employed to measure the F-theta lens surface. The pros and cons, the existing problems, different applications and areas for improvement of the two methods are discussed. A series of advanced measuring instruments are used in the measurement process. A brief description of measurement mechanisms of these instruments is also presented. As a whole, this paper contributes to the development of the precision measurement technology for optical freeform surfaces.

Application of radial basis functions to represent optical freeform surfaces

2010 ◽  
Author(s):  
Ozan Cakmakci ◽  
Ilhan Kaya ◽  
Gregory E. Fasshauer ◽  
Kevin P. Thompson ◽  
Jannick P. Rolland
Keyword(s):  
Radial Basis Functions ◽  
Basis Functions ◽  
Freeform Surfaces ◽  
Radial Basis ◽  
Optical Freeform Surfaces

scholarly journals Fiducial-aided on-machine positioning method for precision manufacturing of optical freeform surfaces

2018 ◽  
Vol 26 (15) ◽  
pp. 18928 ◽  
Author(s):  
Shixiang Wang ◽  
Chifai Cheung ◽  
Mingjun Ren ◽  
Mingyu Liu
Keyword(s):  
Precision Manufacturing ◽  
Freeform Surfaces ◽  
Positioning Method ◽  
Optical Freeform Surfaces

scholarly journals The Manufacturing of a Multi-surface Monolithic Telescope with Freeform Surfaces

2019 ◽  
Vol 215 ◽  
pp. 06004
Author(s):  
Todd Blalock ◽  
Brian Myer ◽  
Brittany Cox ◽  
Jessica Nelson
Keyword(s):  
Mechanical Stability ◽  
Optical Systems ◽  
Optical Performance ◽  
Freeform Surfaces ◽  
Optical Surfaces ◽  
Spherical Surfaces

Monolithic multi-surface telescopes combined with freeform optical surfaces provide improvements in optical performance in a smaller footprint as compared to systems with spherical surfaces, while providing superior mechanical stability to traditional telescope assemblies. Three different monolithic telescope concepts, in different configurations and optical performance were produced as proof of concepts. The results of the telescopes are presented as well as the unique manufacturing and testing challenges to produce these monolithic optical systems.

State verification scheme for means of measuring DC and AC electrical resistance

2021 ◽  
pp. 26-30
Author(s):  
Mark D. Klionsky ◽  
Igor A. Samodurov
Keyword(s):  
Electrical Resistance ◽  
High Frequency ◽  
Measuring Instruments ◽  
Shunt Resistance ◽  
Working Standard ◽  
Verification Scheme ◽  
The Status ◽  
State Verification Scheme ◽  
Working Standards ◽  
First Time

The need to develop a new state verification scheme (SVS) is caused by the emergence of high-precision bridges, resistance measures and boxes with a low temperature coefficient (0,02–0,5) ppm/К, highly stable transient measures, electronic resistance calibrators, and high frequency resistance measures. Recommendations how to assign the status of a working standard to measures, R-meters and measuring shunts with accuracy from 0,005 % to 0,500 %, sufficient for verification of measuring instruments, are given. SVS consists of two parts: part 1 covers electrical resistance measures, boxes and R-meters, part 2 – to measuring shunts and shunt resistance meters. Part 2 was introduced to the SVS for the first time. The revised indicators of accuracy for working standards of all levels are considered, conditions for the investigation of measuring instruments for assigning the status of a working standard, criteria for assessing metrological characteristics are given.

Population viability of the Snake River chinook salmon (Oncorhynchus tshawytscha)

1995 ◽  
Vol 52 (7) ◽  
pp. 1442-1448 ◽  
Author(s):  
John M. Emlen
Keyword(s):  
Chinook Salmon ◽  
Oncorhynchus Tshawytscha ◽  
Population Viability ◽  
Snake River ◽  
Management Actions ◽  
Population Dynamics Model ◽  
The Status ◽  
Salmon Population ◽  
Mortality Improvement ◽  
Best Fit

In the presence of historical data, population viability models of intermediate complexity can be parameterized and utilized to project the consequences of various management actions for endangered species. A general stochastic population dynamics model with density feedback, age structure, and autocorrelated environmental fluctuations was constructed and parameterized for best fit over 36 years of spring chinook salmon (Oncorhynchus tshawytscha) redd count data in five Idaho index streams. Simulations indicate that persistence of the Snake River spring chinook salmon population depends primarily on density-independent mortality. Improvement of rearing habitat, predator control, reduced fishing pressure, and improved dam passage all would alleviate density-independent mortality. The current value of the Ricker α should provide for a continuation of the status quo. A recovery of the population to 1957–1961 levels within 100 years would require an approximately 75% increase in survival and (or) fecundity. Manipulations of the Ricker β are likely to have little or no effect on persistence versus extinction, but considerable influence on population size.

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