Image Sensor
- The Mechanisms Behind the Image Sensor
- Creating a Digital Image
- Digital Imaging Performance (Resolution and Colour Resolution)
The Mechanisms Behind the Image Sensor
An image sensor is generally made up of many small photodiodes that convert light into an electrical signal. As light hits the surface of the device and is focused onto each photodiode via a micro lens, the image sensor then converts it into an electrical signal before outputting the final image.
Image sensors are able to gather light intensity information, but by themselves, are unable to reproduce colours.
In order to create a colour image, an RGB (red, green, blue) filter is placed in front of the photodiodes.
Alternatively, a CMYG (cyan, magenta, yellow, green) filter can be used, though an RGB filter will provide for better colour reproduction and is better suited for digital imaging.
The number of pixels in the image sensor
The number of pixels in the image sensor can be described in terms of the number of total pixels, the number of effective pixels, and the number of virtual pixels.
In a colour image sensor, there are pixels that line the perimeter of the device and help to control the colour and light intensity of an image, although they do not directly contribute to the formation of an image.
Total pixels refer to the number of pixels contained within an image sensor, regardless of whether or not they are used to generate an image.
Effective pixels describe the number of pixels used, including the ones that help determine the colour being displayed by each pixel. Virtual pixels refer to the pixels that are actually used to generate and form an image.
Creating a Digital Image
In order to display an image with a digital microscope, an image sensor with a colour filter converts the light received from the lens into digital signals.
After processing those signals, the data is then converted into an image and displayed on-screen.
- A
- Image sensor
- B
- Analogue signal
- C
- Pixel conversion
- D
- Digital signal
- E
- Digital operation
- F
- Display
Digital Imaging Performance (Resolution and Colour Resolution)
Two of the performance indicators for digital imaging are display resolution and colour resolution.
Display resolution refers to the construction of an image from a given number of pixels, with a higher pixel count being associated with a higher resolution image. Colour resolution refers to the ability of each pixel to represent subtle brightness and colour tones in the digital image.
- A
- The number of horizontal and vertical pixels that make up an image = Display resolution
- B
- The number of colour or brightness levels one pixel can represent = Colour resolution
