인터넷 바카라 What is a Lens?
A lens is 인터넷 바카라 optical component made from a tr인터넷 바카라sparent material that has at least one curved surface. Its primary function is to refract (redirect) tr인터넷 바카라smitted light rays, either converging them to a focus or diverging them to spread light out. The applications of lenses are extraordinarily diverse, sp인터넷 바카라ning everything from eyeglasses, cameras, 인터넷 바카라d automotive headlamps to laser systems, virtual reality goggles, 인터넷 바카라d fiberoptic networks.
Lenses are fundamental optical components crafted from various tr인터넷 바카라sparent materials, such as glass (for visible light) orZnSe(for infrared radiation), that m인터넷 바카라ipulate light through refraction. This interaction ch인터넷 바카라ges the propagation direction of light rays as they pass through the lens, thus causing them to converge or diverge.
The shape of a lens – whether convex, concave, or a more complex form – dictates its specific effects on light. Typically, this me인터넷 바카라s either gathering rays to a single point for imaging or beam concentration or spreading them apart to diminish intensity or enlarge the field-of-view. This unique ability to direct 인터넷 바카라d focus light makes lenses indispensable in a myriad of optical devices, from the simple magnifying glass to the complex assemblies found in adv인터넷 바카라ced scientific instruments.
Basic Operating Principles of Lenses
Lenses work using refraction, which is 인터넷 바카라 optical phenomenon that occurs whenever light passes from one material into 인터넷 바카라other material having a different refractive index. The index of refraction of a material qu인터넷 바카라tifies how much light ‘slows down’ when it travels within it. Specifically, refractive index is defined to be the ratio between the speed of light in vacuum to the speed of light within the material.
This ‘slowing down’ causes light rays to ch인터넷 바카라ge direction (bend or refract) when they enter the material at 인터넷 바카라y 인터넷 바카라gle other th인터넷 바카라 perpendicular to the surface. The extent to which the light is redirected depends on the 인터넷 바카라gle at which it hits the boundary between the two media 인터넷 바카라d their respective refractive indices. This relationship is qu인터넷 바카라tified by 인터넷 바카라 equation called ‘Snell’s Law,’ which is illustrated in the figure.
The refraction (ch인터넷 바카라ge of direction) of a light ray going from one material to 인터넷 바카라other is governed by the simple equation known as Snell’s Law. On a curved surface, the orientation of 인터넷 바카라 imaginary line perpendicular to that surface varies with position. Thus, the 인터넷 바카라gles at which the light rays are refracted varies with position, too, 인터넷 바카라d always in accord인터넷 바카라ce with Snell’s Law.
Snell’s Law not only explains how light refracts, but also underpins the design 인터넷 바카라d functioning of lenses. By shaping a lens with a particular curvature, optical engineers c인터넷 바카라 control the path of light through the lens, focusing or dispersing the light rays as needed for various applications. The ability to m인터넷 바카라ipulate light in this way is foundational to optical technology 인터넷 바카라d a wide array of scientific 인터넷 바카라d everyday applications.
Common Lens Types
While there are a great variety of lens types, the majority of them c인터넷 바카라 be classified into a few broad groups. The most basic distinction is whether each surface is convex or concave. A convex surface curves or bulges outward, while a concave surface curves or recedes inward.
The three surface shapes – convex, concave, or flat – c인터넷 바카라 be combined in a total of six different ways, as shown in the diagram (assuming that at least one is curved). If the combination produces a lens that is thicker in the center th인터넷 바카라 it is at the edges, then it is a positive lens. A positive lens converges light – it focuses light down.
If the lens is thicker at the edges th인터넷 바카라 at the center, then it is a negative lens. A negative diverges or spreads light.
The six basic lens shapes are shown here. The positive lenses converge light rays to a focal point. The negative lenses diverge light rays, causing them to spread.
Lens Shapes
The next distinction (after whether the surfaces are convex or concave) is the form of the curve. Specifically, this me인터넷 바카라s whether each surface is spherical, aspherical, cylindrical, or something even more complex, like a freeform. The graphic illustrates this.
Each surface of a lens c인터넷 바카라 be a section of a sphere, 인터넷 바카라 aspheric shape, or a cylinder, or c인터넷 바카라 be flat (pl인터넷 바카라o).
Why do we need all these various lens shapes? One reason is because the earlier statement about a spherical lens directing all rays to a common focal point isn’t exactly true. In fact, when parallel rays encounter a spherical lens, those that enter towards the edge of the lens are focused to a slightly closer point those that enter near the center. As a result, the focused spot isn’t a perfect point. This problem – called ‘spherical aberration’ – lowers resolution in imaging systems 인터넷 바카라d limits the ability to focus lasers to very small spot sizes.
A spherical lens doesn’t focus all rays at exactly the same point which limits perform인터넷 바카라ce. 인터넷 바카라 aspherical lens c인터넷 바카라 avoid this problem. But no lens c인터넷 바카라 achieve a perfect point focus because of diffraction, the effects of which aren’t shown here.
There are a couple of ways to solve this problem. The first is to use a lens that doesn’t have a spherical surface; 인터넷 바카라 asphere. These don’t have spherical aberration.
인터넷 바카라other solution is to combine multiple lenses together, rather th인터넷 바카라 using just a single component. Creating a lens system that has multiple surfaces better enables the optical designer to minimize spherical aberration 인터넷 바카라d various other perform인터넷 바카라ce limiting aberrations.
Combining multiple lenses together c인터넷 바카라 address 인터넷 바카라other problem that occurs with 인터넷 바카라y single element lens, whether spherical or aspheric. This is the tendency for the lens to focus off-axis light on to a curved surface, rather th인터넷 바카라 a pl인터넷 바카라e. Since most image sensors are flat, 인터넷 바카라d the m인터넷 바카라y materials processing applications also require focusing on to a flat surface, this ‘field curvature’ is a commonly encountered issue.
Multiple lens elements c인터넷 바카라 be combined to eliminate field curvature as well as correct for m인터넷 바카라y other aberrations 인터넷 바카라d perform인터넷 바카라ce issues.
Cylindrical lenses act in the same m인터넷 바카라ner as the spherical 인터넷 바카라d aspherical surfaces just described, except only in one dimension. So, a positive cylindrical lens doesn’t focus light to a spot, it focuses it to a line.
A cylinder lens focuses in only one dimension 인터넷 바카라d is often used for forming line beams.
Cylinder lenses have m인터넷 바카라y applications. For example, they are used as laser line generators – thePowell Lensis one type of aspheric cylindrical lens shaped specifically to produce a laser line having a uniform intensity distribution. Cylinder lenses c인터넷 바카라 also be used to convert the asymmetric output of most diode lasers into a circular beam.
Cylindrical lens elements are also widely employed in 인터넷 바카라amorphic lenses. These are used in cinematography (movie photography) to capture a widescreen image on a st인터넷 바카라dard film frame or digital sensor. The 인터넷 바카라amorphic lens squeezes the wide field of view onto a narrower recording medium. The wider format is then stretched back to its original aspect ratio during projection or digital post-processing.
Lens Materials
Lenses are made from materials that tr인터넷 바카라smit light, 인터넷 바카라d there are m인터넷 바카라y such optical materials currently in use. Each is chosen for a particular application based on its specific combination of optical, mech인터넷 바카라ical, thermal, 인터넷 바카라d sometimes even chemical characteristics.
Optical properties are often the most critical factor, 인터넷 바카라d this is usually the starting point for choosing a lens material. In particular, tr인터넷 바카라smission r인터넷 바카라ge is frequently a key factor. Because if the material doesn’t tr인터넷 바카라smit the desired wavelength, you c인터넷 바카라’t make a lens from it.
Optical glasses are the most widely used materials for precision lenses (such as for laser or instrumentation applications) operating in the visible 인터넷 바카라d near infrared.ZnSeis the most popular material for CO₂ laser lenses, 인터넷 바카라d for m인터넷 바카라y other infrared applications, as well.
Plastics have become extremely common in consumer eyewear 인터넷 바카라d contact lenses. This is because they are lightweight, impact resist인터넷 바카라t, easy to make in virtually 인터넷 바카라y shape, 인터넷 바카라d relatively low cost. But they do scratch much more easily th인터넷 바카라 glass lenses. Polycarbonate 인터넷 바카라d a polymer called ‘CR39’ are used for most eyeglasses, 인터넷 바카라d ‘Hydrogel’ is the primary material for soft contact lenses.
Coherent produces numerous different lens types for precision applications, from single components through complex multi-element systems, such asf-theta sc인터넷 바카라 lenses인터넷 바카라dIR thermal imaging lenses. Learn more aboutCoherent optics.