In spherical aberration, rays of light from a point on the optical axis of a spherical lens do not all meet at the same image point. Rays passing closer to the center are focussed farther away than the rays passing through a circular zone near its rim. A circular cross-section is formed whenever a plane held perpendicular to the optical axis is made to intersect a cone. The area of the cross-section varies with the distance along the optical axis. The smallest size is known as the circle of least confusion. The most spherical aberration-free image is found at this distance.

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The image shows two images, one resulting from a central cone of rays and the other from a cone passing through the rim.

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The image depicts a case of spherical aberration. The most spherical aberration-free image is found at the circle of least confusion.

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your home infrared appliances via PC and Android. The USB Infrared transmitter is compatible with Linux, Windows and *Android. The unit features IR transmitter that emmits infrared signals with wavelenght of 940nm @38khz , which is the Standard IR frequency for most of the IR controlled home appliances on the market. The unit has 3 powerful infrared LEDS which triples the operating range and enlarges the IR LED viewing angle to about 180 degrees. The USB Infrared transmitter’s powerful infrared LEDs, provide a operating range of more than 10 meters line of sight, which makes it useful for automating large rooms , halls etc.

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Astigmatism is the result of the failure of a single zone of the lens to focus the image of an off-axis point at a single point. In the figure, we see two planes perpendicular to each other passing through the optical axis. These planes are known as the meridian plane and the sagittal plane, the meridian plane being the one containing the off-axis object point. Skew rays, rays not in the meridian plane are focused farther away from the lens than those lying in the plane. In either case, the rays do not meet in a point focus but as lines perpendicular to each other. Intermediate between these two positions, the images are elliptical in shape.

In optics, aberration is a property of optical systems such as lenses that results in light being spread out over some region of space rather than being focused to a point. An image-forming optical system with aberration will produce an image that is not sharp. Aberration can be caused due to a variety of reasons such as lens size, material, thickness and position of the object. In this article, let us learn more about aberration and its type.

The failure of a lens to focus all colours in the same plane is known as chromatic aberration. The refractive index for red is least at the red end of the spectrum, hence the focal length of a lens in the air will be greater for red and green than it would be for blue and violet. Chromatic aberration affects magnification along the optical axis and the axis perpendicular to it. The former is known as longitudinal chromatic aberration and the latter is known as lateral chromatic aberration.

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The Default IRman Driver for Lirc does not allow transmit by default, below is a modified downloadable version, which works with LIRC. If you use the USB Infrared Transmitter in Windows, then you need to download the .inf driver below . The Driver will allow you to use the USB  Transmitter with WinLirc.

The name “Coma” is derived from the fact that a point image is blurred into a comet shape when rays from an off-axis object point are imaged by different zones of the lens. In spherical aberration, the images of an object point that fall on a plane perpendicular to the optical axis are circular in the shape of varying sizes and superimposed about a common centre. In a coma, the images of an off-axis object point are circular, of varying size, but displaced with respect to each other.

The unit is open source and open hardware licensed under GNU GPL 2.0 and it comes with source code, schematics and production files. The USB Infrared transmitter is compatible with Winlirc , via the IRToy driver for WinLirc, and in Linux you can use it via the IRman LIRC driver. The unit is based on the PIC 18f2550 microcontroller, working at 20MHz.

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The Irdroid USB Infrared transmitter provides infrared interface for your PC and your Android Device. It allows you to control and automate all

The curvature of field and distortion refer to the location of image points with respect to one another. The former three aberrations mentioned so far can be corrected by making corrections in the design of the lens, but these two aberrations could remain. In curvature of the field, the image of a plane object perpendicular to the optical axis will lie on a paraboloidal surface known as the Petzval Surface. Distortion, on the other hand, refers to the deformation of an image. There are two kinds of deformation, namely barrel distortion and pincushion distortion.

In an ideal lens, light from any given point of an object would pass through the lens and come together at a single point in the image plane. Contrary to ideal lenses, real lenses do not focus light to a single point. These deviations from the idealized lens performance are known as an aberration of the lens.

When the light of a single wavelength is considered, there are five monochromatic aberrations to be considered and they are:

When the light is not monochromatic (not of a single wavelength), a sixth aberration is found in lenses but not in mirrors and is named chromatic aberration.