scholarly journals Analysis of influence of long back focal length on athermal design based on infrared multispectral camera

2021 ◽  
Vol 70 (18) ◽  
pp. 184201-184201
Author(s):  
Xu Huan-Yao ◽  
◽  
Xu Liang ◽  
Shen Xian-Chun ◽  
Xu Han-Yang ◽  
...  
Keyword(s):  
Focal Length ◽  
Back Focal Length ◽  
Multispectral Camera

Variant of the anastigmatic telescope with three mirrors for back focal length

2011 ◽  
Vol 50 (13) ◽  
pp. 1905
Author(s):  
J. Herrera ◽  
S. Vázquez ◽  
E. Luna ◽  
L. Salas ◽  
J. Nuñez ◽  
...  
Keyword(s):  
Focal Length ◽  
Back Focal Length

scholarly journals A Double Swath Configuration for Improving Throughput and Accuracy of Trait Estimate from UAV Images

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Wenjuan Li ◽  
Alexis Comar ◽  
Marie Weiss ◽  
Sylvain Jay ◽  
Gallian Colombeau ◽  
...  
Keyword(s):  
Plant Height ◽  
Precision Agriculture ◽  
Focal Length ◽  
Critical Issue ◽  
Quality Level ◽  
Ground Sample ◽  
Height Estimates ◽  
Uav Images ◽  
Time Required ◽  
Multispectral Camera

Multispectral observations from unmanned aerial vehicles (UAVs) are currently used for precision agriculture and crop phenotyping applications to monitor a series of traits allowing the characterization of the vegetation status. However, the limited autonomy of UAVs makes the completion of flights difficult when sampling large areas. Increasing the throughput of data acquisition while not degrading the ground sample distance (GSD) is, therefore, a critical issue to be solved. We propose here a new image acquisition configuration based on the combination of two focal length (f) optics: an optics with f=4.2 mm is added to the standard f=8 mm (SS: single swath) of the multispectral camera (DS: double swath, double of the standard one). Two flights were completed consecutively in 2018 over a maize field using the AIRPHEN multispectral camera at 52 m altitude. The DS flight plan was designed to get 80% overlap with the 4.2 mm optics, while the SS one was designed to get 80% overlap with the 8 mm optics. As a result, the time required to cover the same area is halved for the DS as compared to the SS. The georeferencing accuracy was improved for the DS configuration, particularly for the Z dimension due to the larger view angles available with the small focal length optics. Application to plant height estimates demonstrates that the DS configuration provides similar results as the SS one. However, for both the DS and SS configurations, degrading the quality level used to generate the 3D point cloud significantly decreases the plant height estimates.

Meniscus Shape and Optical Performance of a MEMS-Based Liquid Micro-Lens System

2008 ◽  
Author(s):  
Shong-Leih Lee ◽  
Chao-Fu Yang
Keyword(s):  
Electric Field ◽  
Laplace Equation ◽  
Focal Length ◽  
Optical Systems ◽  
Lens System ◽  
Meniscus Shape ◽  
Optical Aberration ◽  
Numerical Result ◽  
Micro Lens ◽  
Back Focal Length

It is very difficult to fabricate tunable optical systems having an aperture below 1000 micrometers with the conventional means on macroscopic scale. Krogmann et al. (J. Opt. A: Pure Appl. Opt. vol. 8, 2006, pp. S330-S336) presented a MEMS-based tunable liquid micro-lens system with an aperture of 300 micrometers. The system exhibited a tuning range of back focal length between 2.3 mm and infinity by using the electrowetting effect to change the contact angle of the meniscus shape on silicon with a voltage of 0−45V. However, a serious optical aberration was found in their lens system. In the present study, a numerical simulation is performed for this same physical configuration by solving the Young-Laplace equation on the interface of the lens liquid and the surrounding liquid. The resulting meniscus shape produces a back focal length that agrees with the experimental observation excellently. To eliminate the optical aberration, an electric field is applied on the system. The electric field alters the Young-Laplace equation and thus changes the meniscus shape and the quality of the lens system. The numerical result shows that the optical aberration of the lens system can be essentially eliminated when a proper electric field is applied.

Non-Destructive Measurement of Doublet Objective Lens Structure Parameters Based on ZEMAX

2014 ◽  
Vol 635-637 ◽  
pp. 694-697
Author(s):  
Xin Bian ◽  
Feng Huang ◽  
Guo Rong Cao ◽  
Zheng Ling Wang
Keyword(s):  
Refractive Index ◽  
Focal Length ◽  
Optimal Combination ◽  
Radius Of Curvature ◽  
Objective Lens ◽  
Structure Parameters ◽  
Evaluation Function ◽  
Destructive Measurement ◽  
Non Destructive ◽  
Back Focal Length

A method for structure parameters of doublet objective lens with non-destructive measurement is proposed based on the ZEMAX software. The focal length, back focal length, central thickness and the radius of curvature of the first surface and last surface are measured by a spherical interferometer and other instruments. Using the inversion of the evaluation function and optimizing of the ZEMAX, the series of refractive index of the materials and the cemented surface of the doublet objective lens are derived. Then the optimal combination of the glass materials is selected by the aberration tolerances of the doublet objective lens. The examples show that the result is satisfactory.

An On-Line Digital Optical Bench Tester Based on Conoscopy for Lens Quality Evaluation

2013 ◽  
Author(s):  
Wei Hsuan Hsu ◽  
Paul C.-P. Chao ◽  
Wei Dar Chen ◽  
Che-Hung Tsai
Keyword(s):  
Focal Length ◽  
Index Of Refraction ◽  
Modulation Transfer ◽  
Field Curvature ◽  
A Cell ◽  
On Line ◽  
Quick Estimate ◽  
Liquid Crystal Lens ◽  
Back Focal Length

This study aims to develop an on-line tester machine for evaluating the image quality of a camera lens that is used in a lens module in a cell phone. This tester is not only suitable for conventional solid lens, but also applicable to the developing tunable liquid crystal lens by using the conoscopy approach to measure focus length and its quality. On the other hand, the approach using a commercial inspection chart along with a automatic feeding machine is also adopted for a quick estimate on the focusing quality that is primarily based on Modulation Transfer Function (MTF). In addition to the MTF, the proposed tester aims to has other functions of measuring Effect Focal Length (EFL), Back Focal Length (BFL), Field of View (FOV), Field curvature, Distortion, Astigmatism, Lateral/Axial Color, the distribution of index of refraction and phase retardation pattern. The constructed tester is capable of measuring varied optical performance indices for the next-generation tunable lens.

scholarly journals Computation of Analytical Zoom Locus Using Padé Approximation

Mathematics ◽  
2020 ◽  
Vol 8 (4) ◽  
pp. 581 ◽  
Author(s):  
Kang Min Kim ◽  
Sun-Ho Choe ◽  
Jae-Myung Ryu ◽  
Hojong Choi
Keyword(s):  
Rational Function ◽  
Focal Length ◽  
Padé Approximation ◽  
Analytic Form ◽  
Zoom Lens ◽  
Lens System ◽  
Depth Of Focus ◽  
Pade Approximation ◽  
Conventional Calculation ◽  
Back Focal Length

When the number of lens groups is large, the zoom locus becomes complicated and thus cannot be determined by analytical means. By the conventional calculation method, it is possible to calculate the zoom locus only when a specific lens group is fixed or the number of lens groups is small. To solve this problem, we employed the Padé approximation to find the locus of each group of zoom lenses as an analytic form of a rational function consisting of the ratio of polynomials, programmed in MATLAB. The Padé approximation is obtained from the initial data of the locus of each lens group. Subsequently, we verify that the obtained locus of lens groups satisfies the effective focal length (EFL) and the back focal length (BFL). Afterwards, the Padé approximation was applied again to confirm that the error of BFL is within the depth of focus for all zoom positions. In this way, the zoom locus for each lens group of the optical system with many moving lens groups was obtained as an analytical rational function. The practicality of this method was verified by application to a complicated zoom lens system with five or more lens groups using preset patents.

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