A Vacuum Fluorescent Display (VFD) is a display device that uses electron emission and fluorescent materials technology to generate visible light.

1. What is a vacuum fluorescent display

Vacuum fluorescent display is a display technology that uses fluorescent materials to emit visible light and excites it through an electron beam. It is composed of a vacuum-encapsulated glass tube, which contains anode and cathode, fluorescent material and conductive layer, etc. Vacuum fluorescent displays are typically used for digital and character displays. Their advantages include high contrast, wide viewing angles and long lifespan.

The working principle of a vacuum fluorescent display is to activate the electron emission at the anode and cathode by applying voltage and make it hit the fluorescent material. Fluorescent materials emit visible light when excited by an electron beam, forming bright spots or characters. Different combinations of anodes and cathodes and fluorescent materials can produce light of different colors, thereby achieving various display effects.

2. Classification of vacuum Fluorescent displays

According to different structures and applications, vacuum fluorescent displays can be classified into the following categories:

Single-color VFD: Single-color VFDS use fluorescent materials of a single color, typically green or bluish green. It is suitable for display scenarios that require simple and high-contrast, such as calculators and digital clocks.

Multi-color VFD: Multi-color VFD uses fluorescent materials of various colors and can achieve display effects in multiple colors, such as red, green, blue, etc. This makes multi-color VFDS more suitable for applications that require richer display effects, such as automotive instrument panels and home appliance control panels.

Graphic VFD: Graphic VFD features higher resolution and more complex display functions. It can display images, graphics and text, etc. Graphic VFDS are widely used in scenarios such as industrial instruments and information display screens.

3. Working Principle of vacuum Fluorescent display

The working principle of vacuum fluorescent display is based on Cathode Ray Tube (Cathode ray tube, CRT) technology. The following is the working process of a vacuum fluorescent display:

Anode and cathode: A vacuum fluorescent display contains one or more electrodes, which are located at the bottom and top of the display. Electron emission is generated at the cathode by applying voltage.

Fluorescent material: The front panel of a vacuum fluorescent display is coated with a layer of fluorescent material, which is usually composed of trisalts of phosphate and other additives. When an electron beam hits a fluorescent material, it gets excited and emits visible light.

Conductive layer: The conductive layer is located behind the fluorescent material and is used to control the direction and focusing of the electron beam. The conductive layer is usually composed of conductive glass or metal, which enables the electron beam to directly hit the fluorescent material.

Control circuit: The vacuum fluorescent display also contains a control circuit, which is responsible for managing the anode and cathode voltages as well as the position and intensity of the electron beam. Through the control circuit, the driving and brightness adjustment of the vacuum fluorescent display can be achieved.

The working process of a vacuum fluorescent display is as follows:

When an appropriate voltage is applied to the cathode, the cathode begins to emit an electron beam.

The electron beam, under the control of the conductive layer, is focused into a fine beam current and directed towards the fluorescent material.

When an electron beam hits a fluorescent material, it excites the atoms or molecules within the fluorescent material. These excited atoms or molecules rearrange to release energy, which is emitted in the form of visible light.

The light emitted by the fluorescent material passes through the glass panel for display.

The control circuit receives signals from the input source and controls the anode and cathode voltages as well as the position and intensity of the electron beam based on the signals.

The control circuit also determines which anodes and cathodes are activated at specific time points based on the input signal, thereby generating the required image or character.

Vacuum fluorescent displays have many advantages. First of all, they have high contrast and bright colors, making the displayed content clearly visible. Secondly, vacuum fluorescent displays have a wide viewing Angle, and even at a relatively large viewing Angle, the images can remain consistent. In addition, vacuum fluorescent displays have a long lifespan and can withstand harsh environments such as high temperatures and humidity.

However, vacuum fluorescent displays also have some limitations. Due to the use of vacuum tube technology, vacuum fluorescent displays are relatively large and bulky, making it difficult to achieve flexible display. In addition, vacuum fluorescent displays consume more power and are less energy-efficient than liquid crystal displays and organic light-emitting diodes (OLeds).

In summary, a vacuum fluorescent display is a display device that generates visible light by using fluorescent materials and electron beam emission technology. It achieves display effects through the control of anode and cathode voltages and electron beams, and has the advantages of high contrast, wide viewing angles and long lifespan. Despite some limitations, vacuum fluorescent displays are still widely used in some specific application fields.