Digital Camera

Digital cameras are devices that perform image decomposition and photoelectric signal conversion. Image decomposition is the process of breaking down a complete image into several independent pixels (the smallest units that make up a television image). Generally speaking, the more pixels there are, the clearer the image. Each pixel is represented by a single color and brightness. The camera device can convert the light signals of each pixel in the image into corresponding electrical signals, and then transmit them to the output terminal in a certain order. Digital cameras are divided into two categories: camera tubes and solid-state (semiconductor) camera devices.

Camera tubes and electron beam devices are further divided into several types, such as image tubes, photomultiplier image tubes, orthorectified image tubes, and photoconductive camera tubes. Small lead oxide phototransistors are commonly used in new cameras. All kinds of camera tubes have a vacuum glass shell, which contains a target surface and an electron gun. The subject is imaged on the target surface through the window on the glass shell, and the illumination distribution of each point on the target surface is converted into the corresponding potential distribution using the photoelectric emission effect or photoconductive effect of the target surface, turning the light image into an electrical image. Driven by the deflection coil outside the tube, the electron beam scans the target surface point by point and line by line, and outputs the potential signals of each pixel on the scanning path in sequence.

② Solid state imaging devices. A new type of charge coupled device (CCD). Hundreds of thousands of device units are arranged in an array, and the surface has photosensitive properties. The subject is imaged on the array, and the amount of charge stored in each unit is proportional to the illuminance. By using clock pulses and shift control signals, the signals of each unit in the array can be moved out in a certain order to obtain an image electrical signal with varying intensity over time.

A preamplifier is a video amplifier that amplifies the weak signal output by the camera device to a specified amplitude. To ensure a good signal-to-noise ratio, it is required that the preamplifier has the smallest possible noise figure.