Aperture Efficiency and Wide Field-Of-View Optical Systems Mark R
Total Page:16
File Type:pdf, Size:1020Kb
Load more
Recommended publications
-
Breaking Down the “Cosine Fourth Power Law”
Breaking Down The “Cosine Fourth Power Law” By Ronian Siew, inopticalsolutions.com Why are the corners of the field of view in the image captured by a camera lens usually darker than the center? For one thing, camera lenses by design often introduce “vignetting” into the image, which is the deliberate clipping of rays at the corners of the field of view in order to cut away excessive lens aberrations. But, it is also known that corner areas in an image can get dark even without vignetting, due in part to the so-called “cosine fourth power law.” 1 According to this “law,” when a lens projects the image of a uniform source onto a screen, in the absence of vignetting, the illumination flux density (i.e., the optical power per unit area) across the screen from the center to the edge varies according to the fourth power of the cosine of the angle between the optic axis and the oblique ray striking the screen. Actually, optical designers know this “law” does not apply generally to all lens conditions.2 – 10 Fundamental principles of optical radiative flux transfer in lens systems allow one to tune the illumination distribution across the image by varying lens design characteristics. In this article, we take a tour into the fascinating physics governing the illumination of images in lens systems. Relative Illumination In Lens Systems In lens design, one characterizes the illumination distribution across the screen where the image resides in terms of a quantity known as the lens’ relative illumination — the ratio of the irradiance (i.e., the power per unit area) at any off-axis position of the image to the irradiance at the center of the image. -
“Digital Single Lens Reflex”
PHOTOGRAPHY GENERIC ELECTIVE SEM-II DSLR stands for “Digital Single Lens Reflex”. In simple language, a DSLR is a digital camera that uses a mirror mechanism to either reflect light from a camera lens to an optical viewfinder (which is an eyepiece on the back of the camera that one looks through to see what they are taking a picture of) or let light fully pass onto the image sensor (which captures the image) by moving the mirror out of the way. Although single lens reflex cameras have been available in various shapes and forms since the 19th century with film as the recording medium, the first commercial digital SLR with an image sensor appeared in 1991. Compared to point-and-shoot and phone cameras, DSLR cameras typically use interchangeable lenses. Take a look at the following image of an SLR cross section (image courtesy of Wikipedia): When you look through a DSLR viewfinder / eyepiece on the back of the camera, whatever you see is passed through the lens attached to the camera, which means that you could be looking at exactly what you are going to capture. Light from the scene you are attempting to capture passes through the lens into a reflex mirror (#2) that sits at a 45 degree angle inside the camera chamber, which then forwards the light vertically to an optical element called a “pentaprism” (#7). The pentaprism then converts the vertical light to horizontal by redirecting the light through two separate mirrors, right into the viewfinder (#8). When you take a picture, the reflex mirror (#2) swings upwards, blocking the vertical pathway and letting the light directly through. -
Introduction to CODE V: Optics
Introduction to CODE V Training: Day 1 “Optics 101” Digital Camera Design Study User Interface and Customization 3280 East Foothill Boulevard Pasadena, California 91107 USA (626) 795-9101 Fax (626) 795-0184 e-mail: [email protected] World Wide Web: http://www.opticalres.com Copyright © 2009 Optical Research Associates Section 1 Optics 101 (on a Budget) Introduction to CODE V Optics 101 • 1-1 Copyright © 2009 Optical Research Associates Goals and “Not Goals” •Goals: – Brief overview of basic imaging concepts – Introduce some lingo of lens designers – Provide resources for quick reference or further study •Not Goals: – Derivation of equations – Explain all there is to know about optical design – Explain how CODE V works Introduction to CODE V Training, “Optics 101,” Slide 1-3 Sign Conventions • Distances: positive to right t >0 t < 0 • Curvatures: positive if center of curvature lies to right of vertex VC C V c = 1/r > 0 c = 1/r < 0 • Angles: positive measured counterclockwise θ > 0 θ < 0 • Heights: positive above the axis Introduction to CODE V Training, “Optics 101,” Slide 1-4 Introduction to CODE V Optics 101 • 1-2 Copyright © 2009 Optical Research Associates Light from Physics 102 • Light travels in straight lines (homogeneous media) • Snell’s Law: n sin θ = n’ sin θ’ • Paraxial approximation: –Small angles:sin θ~ tan θ ~ θ; and cos θ ~ 1 – Optical surfaces represented by tangent plane at vertex • Ignore sag in computing ray height • Thickness is always center thickness – Power of a spherical refracting surface: 1/f = φ = (n’-n)*c -
Sample Manuscript Showing Specifications and Style
Information capacity: a measure of potential image quality of a digital camera Frédéric Cao 1, Frédéric Guichard, Hervé Hornung DxO Labs, 3 rue Nationale, 92100 Boulogne Billancourt, FRANCE ABSTRACT The aim of the paper is to define an objective measurement for evaluating the performance of a digital camera. The challenge is to mix different flaws involving geometry (as distortion or lateral chromatic aberrations), light (as luminance and color shading), or statistical phenomena (as noise). We introduce the concept of information capacity that accounts for all the main defects than can be observed in digital images, and that can be due either to the optics or to the sensor. The information capacity describes the potential of the camera to produce good images. In particular, digital processing can correct some flaws (like distortion). Our definition of information takes possible correction into account and the fact that processing can neither retrieve lost information nor create some. This paper extends some of our previous work where the information capacity was only defined for RAW sensors. The concept is extended for cameras with optical defects as distortion, lateral and longitudinal chromatic aberration or lens shading. Keywords: digital photography, image quality evaluation, optical aberration, information capacity, camera performance database 1. INTRODUCTION The evaluation of a digital camera is a key factor for customers, whether they are vendors or final customers. It relies on many different factors as the presence or not of some functionalities, ergonomic, price, or image quality. Each separate criterion is itself quite complex to evaluate, and depends on many different factors. The case of image quality is a good illustration of this topic. -
Section 10 Vignetting Vignetting the Stop Determines Determines the Stop the Size of the Bundle of Rays That Propagates On-Axis an the System for Through Object
10-1 I and Instrumentation Design Optical OPTI-502 © Copyright 2019 John E. Greivenkamp E. John 2019 © Copyright Section 10 Vignetting 10-2 I and Instrumentation Design Optical OPTI-502 Vignetting Greivenkamp E. John 2019 © Copyright On-Axis The stop determines the size of Ray Aperture the bundle of rays that propagates Bundle through the system for an on-axis object. As the object height increases, z one of the other apertures in the system (such as a lens clear aperture) may limit part or all of Stop the bundle of rays. This is known as vignetting. Vignetted Off-Axis Ray Rays Bundle z Stop Aperture 10-3 I and Instrumentation Design Optical OPTI-502 Ray Bundle – On-Axis Greivenkamp E. John 2018 © Copyright The ray bundle for an on-axis object is a rotationally-symmetric spindle made up of sections of right circular cones. Each cone section is defined by the pupil and the object or image point in that optical space. The individual cone sections match up at the surfaces and elements. Stop Pupil y y y z y = 0 At any z, the cross section of the bundle is circular, and the radius of the bundle is the marginal ray value. The ray bundle is centered on the optical axis. 10-4 I and Instrumentation Design Optical OPTI-502 Ray Bundle – Off Axis Greivenkamp E. John 2019 © Copyright For an off-axis object point, the ray bundle skews, and is comprised of sections of skew circular cones which are still defined by the pupil and object or image point in that optical space. -
Multi-Agent Recognition System Based on Object Based Image Analysis Using Worldview-2
intervals, between −3 and +3, for a total of 19 different EVs To mimic airborne imagery collection from a terrestrial captured (see Table 1). WB variable images were captured location, we attempted to approximate an equivalent path utilizing the camera presets listed in Table 1 at the EVs of 0, radiance to match a range of altitudes (750 to 1500 m) above −1 and +1, for a total of 27 images. Variable light metering ground level (AGL), that we commonly use as platform alti- tests were conducted using the “center weighted” light meter tudes for our simulated damage assessment research. Optical setting, at the EVs listed in Table 1, for a total of seven images. depth increases horizontally along with the zenith angle, from The variable ISO tests were carried out at the EVs of −1, 0, and a factor of one at zenith angle 0°, to around 40° at zenith angle +1, using the ISO values listed in Table 1, for a total of 18 im- 90° (Allen, 1973), and vertically, with a zenith angle of 0°, the ages. The variable aperture tests were conducted using 19 dif- magnitude of an object at the top of the atmosphere decreases ferent apertures ranging from f/2 to f/16, utilizing a different by 0.28 at sea level, 0.24 at 500 m, and 0.21 at 1,000 m above camera system from all the other tests, with ISO = 50, f = 105 sea level, to 0 at around 100 km (Green, 1992). With 25 mm, four different degrees of onboard vignetting control, and percent of atmospheric scattering due to atmosphere located EVs of −⅓, ⅔, 0, and +⅔, for a total of 228 images. -
Holographic Optics for Thin and Lightweight Virtual Reality
Holographic Optics for Thin and Lightweight Virtual Reality ANDREW MAIMONE, Facebook Reality Labs JUNREN WANG, Facebook Reality Labs Fig. 1. Left: Photo of full color holographic display in benchtop form factor. Center: Prototype VR display in sunglasses-like form factor with display thickness of 8.9 mm. Driving electronics and light sources are external. Right: Photo of content displayed on prototype in center image. Car scenes by komba/Shutterstock. We present a class of display designs combining holographic optics, direc- small text near the limit of human visual acuity. This use case also tional backlighting, laser illumination, and polarization-based optical folding brings VR out of the home and in to work and public spaces where to achieve thin, lightweight, and high performance near-eye displays for socially acceptable sunglasses and eyeglasses form factors prevail. virtual reality. Several design alternatives are proposed, compared, and ex- VR has made good progress in the past few years, and entirely perimentally validated as prototypes. Using only thin, flat films as optical self-contained head-worn systems are now commercially available. components, we demonstrate VR displays with thicknesses of less than 9 However, current headsets still have box-like form factors and pro- mm, fields of view of over 90◦ horizontally, and form factors approach- ing sunglasses. In a benchtop form factor, we also demonstrate a full color vide only a fraction of the resolution of the human eye. Emerging display using wavelength-multiplexed holographic lenses that uses laser optical design techniques, such as polarization-based optical folding, illumination to provide a large gamut and highly saturated color. -
Depth of Field Lenses Form Images of Objects a Predictable Distance Away from the Lens. the Distance from the Image to the Lens Is the Image Distance
Depth of Field Lenses form images of objects a predictable distance away from the lens. The distance from the image to the lens is the image distance. Image distance depends on the object distance (distance from object to the lens) and the focal length of the lens. Figure 1 shows how the image distance depends on object distance for lenses with focal lengths of 35 mm and 200 mm. Figure 1: Dependence Of Image Distance Upon Object Distance Cameras use lenses to focus the images of object upon the film or exposure medium. Objects within a photographic Figure 2 scene are usually a varying distance from the lens. Because a lens is capable of precisely focusing objects of a single distance, some objects will be precisely focused while others will be out of focus and even blurred. Skilled photographers strive to maximize the depth of field within their photographs. Depth of field refers to the distance between the nearest and the farthest objects within a photographic scene that are acceptably focused. Figure 2 is an example of a photograph with a shallow depth of field. One variable that affects depth of field is the f-number. The f-number is the ratio of the focal length to the diameter of the aperture. The aperture is the circular opening through which light travels before reaching the lens. Table 1 shows the dependence of the depth of field (DOF) upon the f-number of a digital camera. Table 1: Dependence of Depth of Field Upon f-Number and Camera Lens 35-mm Camera Lens 200-mm Camera Lens f-Number DN (m) DF (m) DOF (m) DN (m) DF (m) DOF (m) 2.8 4.11 6.39 2.29 4.97 5.03 0.06 4.0 3.82 7.23 3.39 4.95 5.05 0.10 5.6 3.48 8.86 5.38 4.94 5.07 0.13 8.0 3.09 13.02 9.93 4.91 5.09 0.18 22.0 1.82 Infinity Infinite 4.775 5.27 0.52 The DN value represents the nearest object distance that is acceptably focused. -
What's a Megapixel Lens and Why Would You Need One?
Theia Technologies white paper Page 1 of 3 What's a Megapixel Lens and Why Would You Need One? It's an exciting time in the security department. You've finally received approval to migrate from your installed analog cameras to new megapixel models and Also translated in Russian: expectations are high. As you get together with your integrator, you start selecting Что такое мегапиксельный the cameras you plan to install, looking forward to getting higher quality, higher объектив и для чего он resolution images and, in many cases, covering the same amount of ground with нужен one camera that, otherwise, would have taken several analog models. You're covering the basics of those megapixel cameras, including the housing and mounting hardware. What about the lens? You've just opened up Pandora's Box. A Lens Is Not a Lens Is Not a Lens The lens needed for an IP/megapixel camera is much different than the lens needed for a traditional analog camera. These higher resolution cameras demand higher quality lenses. For instance, in a megapixel camera, the focal plane spot size of the lens must be comparable or smaller than the pixel size on the sensor (Figures 1 and 2). To do this, more elements, and higher precision elements, are required for megapixel camera lenses which can make them more costly than their analog counterparts. Figure 1 Figure 2 Spot size of a megapixel lens is much smaller, required Spot size of a standard lens won't allow sharp focus on for good focus on megapixel sensors. a megapixel sensor. -
EVERYDAY MAGIC Bokeh
EVERYDAY MAGIC Bokeh “Our goal should be to perceive the extraordinary in the ordinary, and when we get good enough, to live vice versa, in the ordinary extraordinary.” ~ Eric Booth Welcome to Lesson Two of Everyday Magic. In this week’s lesson we are going to dig deep into those magical little orbs of light in a photograph known as bokeh. Pronounced BOH-Kə (or BOH-kay), the word “bokeh” is an English translation of the Japanese word boke, which means “blur” or “haze”. What is Bokeh? bokeh. And it is the camera lens and how it renders the out of focus light in Photographically speaking, bokeh is the background that gives bokeh its defined as the aesthetic quality of the more or less circular appearance. blur produced by the camera lens in the out-of-focus parts of an image. But what makes this unique visual experience seem magical is the fact that we are not able to ‘see’ bokeh with our superior human vision and excellent depth of field. Bokeh is totally a function ‘seeing’ through the lens. Playing with Focal Distance In addition to a shallow depth of field, the bokeh in an image is also determined by 1) the distance between the subject and the background and 2) the distance between the lens and the subject. Depending on how you Bokeh and Depth of Field compose your image, the bokeh can be smooth and ‘creamy’ in appearance or it The key to achieving beautiful bokeh in can be livelier and more energetic. your images is by shooting with a shallow depth of field (DOF) which is the amount of an image which is appears acceptably sharp. -
Using Depth Mapping to Realize Bokeh Effect with a Single Camera Android Device EE368 Project Report Authors (SCPD Students): Jie Gong, Ran Liu, Pradeep Vukkadala
Using Depth Mapping to realize Bokeh effect with a single camera Android device EE368 Project Report Authors (SCPD students): Jie Gong, Ran Liu, Pradeep Vukkadala Abstract- In this paper we seek to produce a bokeh Bokeh effect is usually achieved in high end SLR effect with a single image taken from an Android device cameras using portrait lenses that are relatively large in size by post processing. Depth mapping is the core of Bokeh and have a shallow depth of field. It is extremely difficult effect production. A depth map is an estimate of depth to achieve the same effect (physically) in smart phones at each pixel in the photo which can be used to identify which have miniaturized camera lenses and sensors. portions of the image that are far away and belong to However, the latest iPhone 7 has a portrait mode which can the background and therefore apply a digital blur to the produce Bokeh effect thanks to the dual cameras background. We present algorithms to determine the configuration. To compete with iPhone 7, Google recently defocus map from a single input image. We obtain a also announced that the latest Google Pixel Phone can take sparse defocus map by calculating the ratio of gradients photos with Bokeh effect, which would be achieved by from original image and reblured image. Then, full taking 2 photos at different depths to camera and defocus map is obtained by propagating values from combining then via software. There is a gap that neither of edges to entire image by using nearest neighbor method two biggest players can achieve Bokeh effect only using a and matting Laplacian. -
12 Considerations for Thermal Infrared Camera Lens Selection Overview
12 CONSIDERATIONS FOR THERMAL INFRARED CAMERA LENS SELECTION OVERVIEW When developing a solution that requires a thermal imager, or infrared (IR) camera, engineers, procurement agents, and program managers must consider many factors. Application, waveband, minimum resolution, pixel size, protective housing, and ability to scale production are just a few. One element that will impact many of these decisions is the IR camera lens. USE THIS GUIDE AS A REFRESHER ON HOW TO GO ABOUT SELECTING THE OPTIMAL LENS FOR YOUR THERMAL IMAGING SOLUTION. 1 Waveband determines lens materials. 8 The transmission value of an IR camera lens is the level of energy that passes through the lens over the designed waveband. 2 The image size must have a diameter equal to, or larger than, the diagonal of the array. 9 Passive athermalization is most desirable for small systems where size and weight are a factor while active 3 The lens should be mounted to account for the back athermalization makes more sense for larger systems working distance and to create an image at the focal where a motor will weigh and cost less than adding the plane array location. optical elements for passive athermalization. 4 As the Effective Focal Length or EFL increases, the field 10 Proper mounting is critical to ensure that the lens is of view (FOV) narrows. in position for optimal performance. 5 The lower the f-number of a lens, the larger the optics 11 There are three primary phases of production— will be, which means more energy is transferred to engineering, manufacturing, and testing—that can the array.