scholarly journals Effects of Lens Focal Length on Perception of Depth and Lateral Distances in Photographic Images

2007 ◽  
Vol 61 (11) ◽  
pp. 1649-1652 ◽  
Author(s):  
Tomomi Takezawa
Keyword(s):  
Focal Length ◽  
Photographic Images ◽  
Lens Focal Length

scholarly journals Evaluating effects of focal length and viewing angle in a comparison of recent face landmark and alignment methods

2021 ◽  
Vol 2021 (1) ◽  
Author(s):  
Xiang Li ◽  
Jianzheng Liu ◽  
Jessica Baron ◽  
Khoa Luu ◽  
Eric Patterson
Keyword(s):  
Focal Length ◽  
Ground Truth ◽  
Detection Methods ◽  
Viewing Angle ◽  
Deep Convolutional Neural Networks ◽  
Landmark Detection ◽  
High Performing ◽  
Detection Techniques ◽  
And Performance ◽  
Lens Focal Length

AbstractRecent attention to facial alignment and landmark detection methods, particularly with application of deep convolutional neural networks, have yielded notable improvements. Neither these neural-network nor more traditional methods, though, have been tested directly regarding performance differences due to camera-lens focal length nor camera viewing angle of subjects systematically across the viewing hemisphere. This work uses photo-realistic, synthesized facial images with varying parameters and corresponding ground-truth landmarks to enable comparison of alignment and landmark detection techniques relative to general performance, performance across focal length, and performance across viewing angle. Recently published high-performing methods along with traditional techniques are compared in regards to these aspects.

Absorption efficiency analysis and optical resonator simulation of Ho:YLF laser pumped with Tm:fiber laser

Laser Physics ◽  
2021 ◽  
Vol 32 (1) ◽  
pp. 015001
Author(s):  
Majid Babaiy Tooski ◽  
Abbas Maleki ◽  
Abdolah Eslami Majd ◽  
Hassan Ebadian
Keyword(s):  
Slope Efficiency ◽  
Doping Concentration ◽  
Continuous Wave ◽  
Focal Length ◽  
Beam Width ◽  
Absorption Efficiency ◽  
Optical Resonator ◽  
Threshold Power ◽  
Continuous Wave Operation ◽  
Lens Focal Length

Abstract In this paper, a Tm:fiber laser pumped Ho:YLF laser is simulated. The absorption efficiency, optimum crystal length, and optical resonator are analytically studied and simulated using LASCAD software, and the atomic-level degeneracies are considered in evaluating the absorption efficiency. In this way, the absorption efficiencies of 65% and 87% are obtained for single-pass 30 mm Ho:YLF crystal with doping concentration 0.5% and 1% respectively. These calculated efficiencies are verified by our experimental measurements and they coincide with acceptable errors. To estimate a proper length for the Ho:YLF crystal with specified doping concentration, the up-conversion, and the reabsorption effects are considered. As a result, we find the 30 mm length crystal is suited for reducing the absorption threshold and prohibiting reabsorption while saturation is controlled. The threshold power and slope efficiency for 65 W pumped powers are calculated by LASCAD software, and the thermal lens focal length of −665 mm is obtained. For a nearly constant beam width inside the cavity and suitable beam overlap efficiency, a concave-concave configuration is chosen for the optical resonator. In the continuous-wave operation, the output power is funded to be 38.4 W and the slope efficiency would be 66%.

Measurement of Lens Focal Length with Hartmann-Shack Wave Front Sensor Based on 4F System

Applied laser ◽  
2013 ◽  
Vol 33 (2) ◽  
pp. 212-215
Author(s):  
许江华 Xu Jianghua ◽  
朱岚 Zhu Lan ◽  
陈家璧 Chen Jiabi ◽  
庄松林 Zhuang Songlin
Keyword(s):  
Wave Front ◽  
Focal Length ◽  
Lens Focal Length

Comparative Study of Some Fiber-Optic Remote Raman Probe Designs. Part II: Tests of Single-Fiber, Lensed, and Flat- and Bevel-Tip Multi-Fiber Probes

1996 ◽  
Vol 50 (7) ◽  
pp. 849-860 ◽  
Author(s):  
Thomas F. Cooney ◽  
H. Trey Skinner ◽  
S. M. Angel
Keyword(s):  
Fiber Optic ◽  
Focal Point ◽  
Focal Length ◽  
Numerical Aperture ◽  
Optical Filters ◽  
Organic Liquids ◽  
Raman Signal ◽  
Immersion Medium ◽  
Lens Focal Length ◽  
Overlap Model

We compare relative performances of flat-tipped, beveled (two-fiber and six-around-one), and single-lensed focused fiber-optic Raman probes and, where feasible, evaluate the utility of optical filters for reducing fiber background. The sensitivity profile of each probe is determined by measuring the relative intensity of light backscattered off a flat surface as a function of distance from the probe tip. The experimental results are compared with a simple light-cone-overlap model incorporating fiber numerical aperture, fiber and immersion medium refractive indices, separation between excitation and collection fibers, number of fibers, and fiber bevel angle and/or lens focal length. The model and sensitivity profiles are used to interpret the sampling regions for Raman spectra obtained by using each of the probes with a clear, transparent sample (single-crystal sparry calcite), a white, partially transparent sample (acetaminophen tablet), and a set of organic liquids of varying refractive index. The sensitivity of the tested commercial lensed probe drops off symmetrically about the focal point. For both solid samples, the intensity of fiber background follows a profile determined primarily by laser backscattering off the surface, whereas the sample Raman signal follows a profile dependent upon sampling depth.

Numerical Simulations of Fractional Fourier Transform of Hypergeometric-Gaussian Beam

2013 ◽  
Vol 765-767 ◽  
pp. 780-784 ◽  
Author(s):  
Zhen Feng Yang ◽  
Wen Dan Miao ◽  
Zhen Jun Yang ◽  
Shu Min Zhang
Keyword(s):  
Fourier Transform ◽  
Numerical Simulations ◽  
Gaussian Beam ◽  
Intensity Distribution ◽  
Fractional Fourier Transform ◽  
Focal Length ◽  
Beam Width ◽  
Laser Beams ◽  
New Type ◽  
Lens Focal Length

The fractional Fourier transform (FRFT) of a new type of laser beams called the hypergeometric-Gaussian beam (HyGGB) is investigated in detail. The analytical expression for the FRFT of a HyGGB is derived. The properties of a HyGGB in the FRFT plane with different parameters are illustrated. The results show that the intensity distribution of a HyGGB in the FRFT plane strongly depends on the fractional order, the lens focal length and the initial beam width.

scholarly journals Phase shift of amplitude-modulated optical signals in graphene oxide water dispersions due to thermal lens focal length oscillation

2014 ◽  
Vol 31 (5) ◽  
pp. 1018 ◽  
Author(s):  
Sonia Melle ◽  
Oscar G. Calderón ◽  
Ana Egatz-Gómez ◽  
E. Cabrera-Granado ◽  
F. Carreño ◽  
...  
Keyword(s):  
Graphene Oxide ◽  
Phase Shift ◽  
Thermal Lens ◽  
Focal Length ◽  
Optical Signals ◽  
Lens Focal Length

scholarly journals Tunable subwavelength ultrasound focusing in mesoscale spherical lenses using liquid mixtures

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Sergio Pérez-López ◽  
José Miguel Fuster ◽  
Igor V. Minin ◽  
Oleg V. Minin ◽  
Pilar Candelas
Keyword(s):  
Liquid Mixture ◽  
Focal Length ◽  
Dynamic Control ◽  
Liquid Mixtures ◽  
Acoustic Properties ◽  
Spherical Lens ◽  
Continuous Tuning ◽  
Subwavelength Resolution ◽  
Miscible Liquids ◽  
Lens Focal Length

Abstract In this work, we present a configurable spherical lens for underwater focusing applications, which consists on a hollow ABS container filled with a liquid mixture. Two miscible liquids with different sound speeds are required to implement this novel configurable lens. We show that by adjusting the mixing ratio between the volumes of both liquids, the sound speed of the liquid mixture can be accurately selected. This results in a modification of the acoustic jet properties and a continuous tuning on the lens focal length. This procedure can be fully automatized providing a dynamic control mechanism that can shift the lens focal length to any desired value inside a continuous range in both directions. Depending on the acoustic properties of the selected liquids, subwavelength resolution or even beyond the diffraction limit resolution can be achieved. We provide experimental measurements for ethanol-water mixtures achieving subwavelength resolution for a certain focal length ranging between 34.6 and 42.8 mm.

Minimal Exposure, Rotary Hollow-Cone Illumination and Focus Wobble Added to The Deflection System of an HVEM

1981 ◽  
Vol 39 ◽  
pp. 302-303
Author(s):  
James B. Pawley
Keyword(s):  
Electron Microscopy ◽  
Structural Information ◽  
Focal Length ◽  
Objective Lens ◽  
Angular Deviation ◽  
Hollow Cone ◽  
Exposure System ◽  
Deflection System ◽  
Lens Focal Length ◽  
Fundamental Limitation

Radiation damage places the fundamental limitation on the retrieval of structural information from co-valently bonded material by electron microscopy. Our interest here is simply to describe a system developed for the HVEM which will reduce to a practical minimum the amount of radiation to which the sample must be exposed in order to make a micrograph. Several methods have been described to accomplish this end in the 100 kV microscope. They usually involve pre-focusing on one area of the sample and then misaligning the column mechanically or by electromagnetic deflection in order to image a nearby part of the sample which remains unirradiated until just before the exposure of the micrograph. The only HVEM minimal exposure system seems to be the shutter fitted above the sample on the Cambridge 600 kV HREM.As the angular deviation caused by off axis displacement of the imaged area is inversely proportional to objective lens focal length, the degradation of imaging quality caused by such a displacement will be relatively less in the HVEM because of its longer focal length (EM-7 with side entry stage f=8.5mm).

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