A pixel is a picture element. One pixel contains an amount of information digitally coded. The simplest binary code is 1 bit. This can be 0 or 1 (2 alternatives). 2 bits can be 00, 01, 10, 11 (4 alternatives). It follows then that,
If each pixel in an image is 8 bits, then for a black and white pixel there are 256 shades of grey between black and white. The more bits in a pixel, the more alternatives i.e. better resulting image/definition. For a colour pixel, the 8 bits would be for each of RGB (and Alpha if included).
A logarithm is a power (index) which another number can be raised to. It is a convenient way of representing very large and very small numbers on a simple scale.
An array of pixels in an image can be altered in a number of ways, two of which are: (to remove noise or smooth edges)
To work these out, you work out the mean or median value of the 9 surrounding pixels including the pixel which looks out of place. Then you replace all of the values by the mean or median value you have just worked out.
A lens is a device for either concentrating or diverging light. In its usual form, a lens consists of glass or other optically transparent material (such as perspex) with two shaped surfaces of a particular curvature. It is the refractive index of the lens material and the curvature of the two surfaces that give a particular lens its particular properties. A lens works by refracting the light that passes through it.
Where, v is the distance from the image to the lens, u is the distance from the object to the lens and f is the focal length. The focal length of a lens is the distance along the optical axis from the lens to the focus (or focal point). The reciprocal of these works out the curvature of the waves, or the power of the lens (1/f) in dioptres. U has to be negative because of Cartesian sign convention (and in effect, it has a negative effect on the curvature of the waves).
When the curvature of the waves is zero, the light is said to be collimated (the rays are parallel). A light can be collimated by a number of processes, the easiest being to shine it on a concave mirror with the source at the focus. Collimated light is sometimes said to be focused at infinity which, for experimental puproses is approximately 2m.
For a positive (converging) lens, the focal length is positive, and is the distance from the lens at which a collimated beam of light will be focused to a single spot. For a negative (diverging) lens, the focal length is negative, and is the distance in front of the lens to the point at which a collimated beam appears to be emerging from after passing through the lens.
A sensor is a device that detects, or senses, a signal or physical condition. A sensor is a type of transducer.