Sensor

A sensor in a digital camera is a light-sensitive monochrome analogue device used to convert the received light source into a signal for recording. The sensor of a digital camera uses a digital chip with an array of photosites to measure the light intensity from lens. Three filters, red, green, and blue, are used as an overlay to give three values that represent the color of the light for any pixel of the image sensor array. These analogue RGB values of the sensor array is then sampled and encoded by the digital circuit as a numeric code for stroage.

Types of Image Sensor

The common types of image sensors are charge-coupled device, CCD and active-pixel sensor, CMOS sensors. Both CCD and CMOS sensors are analog devices used to convert captured light into electrical signals.

Color Filter Array of Image Sensor

The color filter arrary of image sensor is used to sample the light intensity of the capatured image with respect to each color separately. The common color filter array designs are linear filter array, color filter mosaic array, and layer structure filter. The structure of filter array also affects the effective color pixel density of image sensor.

Linear Filter Array

The filter pixels in the same row of a linear filter array are of the same color. The repeating pattern of a tri-linear filter array is strips of red, green, and blue filters.

Color Filter Mosaic array

The repeating pattern of a color filter mosaic array is a small square or rectangular submosaic array. The repeating pattern of a Bayer color filter mosaic array is a two-by-two submosaic with 1 red, 2 green, and 1 blue filter pixel where two green filter pixels are arranged in a diagonal setup.

Layer Structure Filter

The practical layer structure filter is a Foveon X3 layered sensor stack in the silicon wafer. The upper part of the silicon wafer absorbs blue light and is used as a blue sensor. The middle part of the silicon wafer absorbs green light and is used as a green sensor. While the lower part of the silicon wafer absorbs red light and is used as a red sensor.

Image Sensor Format

Since there is no standard image sensor format, the dimensions of a image sensor may vary with the digital camera design. Some common sensor formats are:

Format	Width, mm	Height, mm	Aspect Ratio
1/10"	1.28	0.96	4:3
1/8"	1.6	1.2	4:3
1/6"	2.4	1.8	4:3
1/4"	3.6	2.7	4:3
1/3.2"	4.54	3.42	4:3
Film 8mm	4.8	3.5	11:8
1/3"	4.8	3.6	4:3
1/2.5"	5.76	4.29	4:3
Film Super 8mm	5.79	4.01	13:9
1/2.3	6.17	4.55	4:3
1/2"	6.4	4.8	4:3
Film 16mm	10.26	7.49	11:8
1/1.2"	10.67	8	4:3
Film Super 16mm	12.52	7.41	5:3
1"	13.2	8.8	3:2
Movie 35mm	22	16	11:8
Full-frame	36
Film 35mm, Full-frame	36	24	3:2
Film 120	60	60	1:1
Film Large-form	120	101	5:4