Direct-View Storage Tubes (DVSTs) have been around since the early 20th century and have played a significant role in the development of television and medical imaging. In this article, we will delve into the history, types, components, applications, and advantages and disadvantages of Direct-View Storage Tubes.
Direct-View Storage Tubes are a type of cathode-ray tube that was developed in the early 20th century. They are used in various applications, including television and medical imaging. The technology works by converting an optical image into an electrical signal, which is then stored on a phosphor-coated plate.
There is another way to maintain a screen image aside from constantly refreshing the display. This is done by storing the picture information inside the CRT (Cathode Ray Tube) itself. A Cathode Ray Tube that uses this method is called a Direct-View Storage Tube (DVST).
In a DVST, the picture information is stored as a charge distribution right behind the screen that’s coated with phosphor. To achieve this, two electron guns are used. The primary gun is responsible for storing the picture pattern, while the flood gun maintains the picture display. This technology provides an alternative way of maintaining a screen image without the need for constant refreshing.
Direct-View Storage Tube (DVST) monitors offer advantages and disadvantages compared to the more common refresh CRT monitors. The main advantage of a DVST monitor is that it does not require constant refreshing, allowing for displaying very complex pictures at high resolutions without any flicker.
However, one significant disadvantage of DVST systems is that they usually do not display color. Another disadvantage is that selected parts of a picture cannot be erased; instead, the entire screen must be erased and the modified picture is redrawn, which can take several seconds for a complex picture. These drawbacks have led to storage displays being largely replaced by raster systems.
History of Direct-View Storage Tubes
The first Direct-View Storage Tube was developed in 1929 by Vladimir Zworykin, a Russian-American inventor. The device, known as the Iconoscope, was used in the early days of television broadcasting. Later, the Image Orthicon and Vidicon were developed, which improved the Iconoscope’s technology.
Types of Direct-View Storage Tubes
There are three types of Direct-View Storage Tubes: the Iconoscope, Image Orthicon, and Vidicon.
The Iconoscope is the earliest type of Direct-View Storage Tube. It uses a mosaic of photoelectric cells to convert an optical image into an electrical signal. The signal is then amplified and displayed on a cathode-ray tube.
The Image Orthicon, developed in the 1940s, uses an electron beam to scan an image and convert it into an electrical signal. The signal is then stored on a photosensitive plate ( A photosensitive plate refers to a type of photographic film or plate that is sensitive to light and used to capture images in photography. It is a physical medium coated with a light-sensitive emulsion that reacts to light exposure, resulting in a chemical change that produces a visible image. These plates were commonly used in early forms of photography before the invention of digital cameras and are still used today in some specialized fields of photography ).
The Vidicon, developed in the 1950s, uses a photosensitive plate that is scanned by an electron beam. The electron beam dislodges electrons from the photosensitive material, which are then amplified and displayed on a cathode-ray tube.
Components of Direct-View Storage Tubes
Direct-View Storage Tubes have three main components: the electron gun, target plate, and deflection coils.
The electron gun emits a beam of electrons that is focused on the target plate.
The target plate is a photosensitive plate that is coated with a layer of phosphor. When the electron beam hits the plate, it dislodges electrons from the phosphor, which are then stored as an electrical charge.
The deflection coils are used to steer the electron beam across the target plate.
Applications of Direct-View Storage Tubes
Direct-View Storage Tubes have various applications, including television, medical imaging, and scientific research.
Direct-View Storage Tubes were used in the early days of television broadcasting. They were eventually replaced by other technologies, such as the CRT.
Direct-View Storage Tubes are still used in some medical imaging devices, such as X-ray machines and CT scanners.
Direct-View Storage Tubes are used in scientific research for a variety of purposes, such as studying the structure of atoms and molecules.
Advantages and Disadvantages of Direct-View Storage Tubes
Like any technology, Direct-View Storage Tubes have their advantages and disadvantages.
One advantage of Direct-View Storage Tubes is their high resolution. They are capable of producing detailed images, making them useful in applications such as medical imaging and scientific research.
Direct-View Storage Tubes also have a fast response time, making them suitable for applications where a fast refresh rate is required, such as television.
One major disadvantage of Direct-View Storage Tubes is their limited lifespan. The phosphor coating on the target plate can degrade over time, leading to a decrease in image quality.
Direct-View Storage Tubes are also relatively bulky and require a high voltage to operate, which can be a safety concern.
Direct-View Storage Tubes have a long history and have played an important role in the development of various technologies, including television and medical imaging. While they have some advantages, such as high resolution and fast response time, they also have their disadvantages, such as limited lifespan and safety concerns.
Are Direct-View Storage Tubes still used in modern technology?
While Direct-View Storage Tubes have been largely replaced by other technologies, such as LCDs and LEDs, they are still used in some specialized applications, such as medical imaging.
What is the difference between the Iconoscope and the Vidicon?
The Iconoscope uses a mosaic of photoelectric cells to convert an optical image into an electrical signal, while the Vidicon uses a photosensitive plate that is scanned by an electron beam.
Can Direct-View Storage Tubes be repaired if they fail?
Direct-View Storage Tubes can be difficult to repair and may require specialized knowledge and equipment. In many cases, it may be more cost-effective to replace the device.
What is the lifespan of a Direct-View Storage Tube?
The lifespan of a Direct-View Storage Tube depends on a variety of factors, such as usage and operating conditions. In general, they have a limited lifespan due to the degradation of the phosphor coating on the target plate.
What are some potential safety concerns with Direct-View Storage Tubes?
Direct-View Storage Tubes require a high voltage to operate, which can be a safety concern if proper precautions are not taken. Additionally, the phosphor coating on the target plate may contain hazardous materials, such as lead.