What is a 바카라 노하우 디시 Lens?
바카라 노하우 디시 lenses are optics used to generate a uniform-intensity laser line. They employ a unique cylindrical aspheric surface shape to accomplish this. 바카라 노하우 디시 lenses are used in applications as diverse as machine vision and flow cytometry.
Most lasers emit circular or elliptically shaped 바카라 노하우 디시s (in cross-section). The intensity profile across the 바카라 노하우 디시 is typically Gaussian or very nearly so. This Gaussian intensity distribution is beneficial for many applications. But there are also instances in which a uniform intensity distribution (often referred to as a “flat-top”) is more desirable.
There are several ways to convert a Gaussian beam into a uniform intensity distribution (in both one and two dimensions). The most powerful and flexible way is based on the 바카라 노하우 디시 lens. Let’s look at why flat-top beams are sometimes needed, how the 바카라 노하우 디시 lens works, and what benefits it offers over other technologies.
Gaussian 바카라 노하우 디시s – The Good and the Bad
The drawing illustrates a circular Gaussian 바카라 노하우 디시. This 바카라 노하우 디시 is much more intense in the center than at the edges. A Gaussian 바카라 노하우 디시 is the natural result of the physics underlying most lasers, which is why it is so common.
Most lasers naturally produce a round cross-section 바카라 노하우 디시 with a Gaussian intensity distribution – which is much brighter in the center than at the edges. A uniform intensity 바카라 노하우 디시, both circular and square, is shown for comparison.
The Gaussian profile 바카라 노하우 디시 often turns out to be advantageous over a uniform intensity 바카라 노하우 디시 (either round or square) for several reasons. A key one is that a Gaussian 바카라 노하우 디시 can be focused to a smaller spot than a uniform circular 바카라 노하우 디시 of the same diameter. This comes in very handy in many applications. For example, in most materials processing uses, a smaller focused 바카라 노하우 디시 improves the ability to produce minute features, In many laser-based microscopy techniques, smaller focused spot size increases image resolution.
But there are some cases in which the opposite is true, especially when the laser is being formed into a line 바카라 노하우 디시 (a 바카라 노하우 디시 longer in length than width). Line 바카라 노하우 디시s are used in many illumination tasks. Uniform intensity is desirable here because evenly illuminating a scene or object simplifies subsequent image processing and increases image contrast and resolution.
Transforming Gaussian 바카라 노하우 디시s
A unique property of Gaussian 바카라 노하우 디시s is that when they’re focused, expanded, or otherwise reshaped using traditional optics, they maintain their Gaussian intensity profile. It’s actually quite difficult to get rid of it.
The most simple and direct way to transform a Gaussian 바카라 노하우 디시 into one having a uniform intensity distribution is to pass the 바카라 노하우 디시 through an aperture which simply blocks all but the central, and most uniform, portion of the 바카라 노하우 디시. There are two disadvantages to this approach. First, a very large fraction of the laser power is discarded – as much as 75%. Second, the resulting 바카라 노하우 디시 still isn’t all that uniform.
The simplest way to transform a Gaussian 바카라 노하우 디시 to a uniform intensity profile is to just select out the center portion of the 바카라 노하우 디시 and discard the rest. But this approach yields the poorest results.
Transforming a Gaussian 바카라 노하우 디시 to flat-top distribution without throwing out a lot of light is more difficult. But it can be done with both diffractive and refractive techniques.
Diffractive optics work by creating interference between various diffracted orders to spatially redistribute the light in a laser 바카라 노하우 디시. This can produce virtually any arbitrary intensity profile, including nearly flat-top, as well as a wide variety of patterns.
There are two big negatives of diffractive optics for making uniform line 바카라 노하우 디시s. First, they’re not very efficient. They lose a fair amount of light into unwanted diffraction orders. Second, they are typically very wavelength-sensitive. This is particularly problematic when using them with diode lasers.
바카라 노하우 디시let arrays are a purely refractive approach. These are optics containing multiple 바카라 노하우 디시es, each much smaller than the input beam. The output pattern produced by each 바카라 노하우 디시let overlaps in the far field, creating the desired uniform intensity distribution.
Two configurations of cylindrical 바카라 노하우 디시let arrays.
It’s very difficult to achieve a high degree of uniformity in the final beam with 바카라 노하우 디시let arrays. There is usually a substantial amount of high-frequency ripple in the intensity. Additionally, 바카라 노하우 디시let arrays also require specialized tooling to produce, limiting their usefulness to high-volume applications.
The 바카라 노하우 디시 Lens
바카라 노하우 디시 lenses are another type of refractive optic that overcomes the limitations of both diffractive optics and lenslet arrays. The 바카라 노하우 디시 lens is an aspheric cylindrical lens shaped specifically to efficiently transform a Gaussian input beam into a diverging beam with a uniform intensity distribution. Because a 바카라 노하우 디시 lens is a type of cylindrical lens, it only homogenizes the beam in one dimension.
바카라 노하우 디시 lenses.
The figure illustrates the shape of the 바카라 노하우 디시 Lens surface and compares its operation with that of a traditional cylindrical lens. The 바카라 노하우 디시 Lens redirects light from the center to the edge of the beam in order to eliminate the central “hot spot.” The cylindrical lens also causes the beam to fan out in one dimension but preserves its Gaussian profile. So, it produces a line beam that is much brighter in the center than at the edges.
The 바카라 노하우 디시 lens (left) is compared to a traditional cylindrical lens (right). Both optics transform a round Gaussian profile laser beam into a diverging fan of light which makes a line on any surface on which it is projected. The 바카라 노하우 디시 lens shifts light from the center to the edge of the beam to produce a uniform intensity line, while the cylindrical lens maintains the Gaussian profile of the beam, so its line is much brighter in the center.
The 바카라 노하우 디시 lens delivers superior results over diffractive optics in almost every aspect of performance. Most importantly, the 바카라 노하우 디시 Lens is more efficient (loses less light), and produces a steep-edged pattern, with little light outside the desired region.
This 바카라 노하우 디시 lens is also fairly insensitive to input wavelength. This makes it usable with diode lasers, since it is unaffected by unit-to-unit variations in wavelength, as well as the inherent bandwidth and wavelength temperature dependence of these sources. The result is that an overall intensity uniformity of ±5% over the entire pattern can be routinely achieved in production beam homogenizers without having to wavelength select or bin diode lasers.
바카라 노하우 디시 lenses aren’t perfect, though. Each is designed for a specific input beam diameter and won’t produce optimal results with larger or smaller beams. They are also sensitive to alignment (in the axis perpendicular to the cylindrical surface). Misalignment reduces the intensity uniformity of the projected line.
Understanding 바카라 노하우 디시 Lens Specifications
Fabricating the cylindrical asphere on a 바카라 노하우 디시 lens with high precision is challenging, and the quality of 바카라 노하우 디시 lenses varies between manufacturers. This means the performance of a real-world 바카라 노하우 디시 lens may depart significantly from its design values. This makes it important to know how to read published specifications.
The primary specifications for a 바카라 노하우 디시 lens are its operating wavelength, intended input beam diameter (which is defined to be at the 1/e² intensity points, since the input 바카라 노하우 디시 is Gaussian), and output 바카라 노하우 디시 fan angle. These are shown schematically in the drawing. Since the output 바카라 노하우 디시 is intended to be uniform, and not Gaussian, the fan angle is measured at the point at which the power has dropped to 80% of its peak value (rather than the 1/e² power point).
Primary nominal specifications for a 바카라 노하우 디시 lens are the input beam diameter and output beam fan angle.
Typically, the most important performance parameter for a 바카라 노하우 디시 lens is its intensity uniformity. Manufacturing variations and tolerance effects can produce intensity variations (particularly at the beam edges), non-flat top profiles, periodic structure, and scatter.
Power 바카라 노하우 디시 fan angle is usually measured from the points at which the intensity has dropped to 80% of its peak value. Intensity uniformity is specified differently by various manufacturers.
Most manufacturers define line uniformity using the formula given in the preceding drawing. However, they typically only apply this specification to the central 80% of the line (also indicated in the drawing). But excluding the edges of the 바카라 노하우 디시 creates an unrealistic picture of actual performance, because this is where non-uniformities are typically most pronounced.
In contrast, Coherent applies the 바카라 노하우 디시 uniformity specification over 100% of the line length. The same applies to our specifications for line straightness and contained power (the ratio of power contained in the line between the 80% and the 1/e² peak power points). This is a much more stringent and difficult-to-meet specification. The result is theCoherent 바카라 노하우 디시 Lensd바카라 노하우 디시iver better measurement accuracy, signal-to-noise ratio, and unit-to-unit consistency.