Different Types of Displays and How They Work

Displays are devices which take input in the form of still image or video signals output from a computer or other device and output it in the form of images or video. There are various types of displays, each with their own distinctive features.

CRT Displays

These displays use vacuum tubes called cathode ray tubes (CRTs), which create images using electron beams. Because of their thickness, they have large spatial footprints. They also consume a great deal of power, and their use has recently been on the decline.

Liquid Crystal Display

These displays use voltage to control the state of liquid crystals and produce images by using a backlight or capturing external light. They are very bright, and are therefore easy to see in bright places, while also requiring smaller power supplies. However, they are thicker than organic light emitting diode (OLED) displays due to their backlights.

Organic Light Emitting Diode (OLED) Displays

Unlike liquid crystal displays, in these displays individual diodes emit light. Each pixel is made up of organic light emitting diodes which emit light when an electrical current is applied. They require no backlights, consume little power and can be made extremely thin. However, they are prone to an image problem called "burn-in," and have shorter lifespans than liquid crystal displays.

Plasma Displays

Plasma discharge within these displays generates ultraviolet light which strikes phosphors, producing images. They have the advantage of fast response speeds, but they generate a great deal of heat and use a large amount of current, thus consuming a great deal of power. Furthermore, due to how they work, they are not well-suited for achieving higher definitions.

How Liquid Crystal Displays Work

There are several types of displays, but currently the most common is the liquid crystal display. Canon's professional reference displays also use liquid crystal technology. Liquid crystal displays consume little power, are bright, and have long service lives.

What are Liquid Crystals?

Liquid crystals are a state of matter between a solid and a liquid. Squid ink and soap suds are examples of liquid crystals. When liquid, their molecules flow and are scattered. When solid, their molecules lose their fluidity and are arranged in neat rows. In the liquid crystal state, the molecules have the property of gradually orienting themselves in an orderly arrangement.

Liquid crystal molecules are somewhat regularly oriented in their natural state

The Structure of a Liquid Crystal Display

Liquid crystal displays use this property by having the liquid crystals pass or block light to produce images. The liquid crystal molecules are shaped like rods. When arranged horizontally, they prevent light from below from passing through them. When arranged vertically, they allow the light to pass. The angle of the rods is controlled using an electrical current to adjust the luminance. This is the fundamental principle behind liquid crystal displays.

The structure of a liquid crystal display

Liquid crystal displays are made up of two transparent panels encasing liquid crystals and a polarizing filter that only allows light oriented in a particular direction to pass. When a light source is placed behind the display, the light from the light source is polarized with a certain orientation. The angle of the liquid crystal rods will then determine whether or not the light can pass through the next polarizing filter. Turning the current on or off makes it possible to produce white and black, and combining this with a filter for red, green, and blue, the three primary colors of light, makes possible to display various colors.

Relationship between liquid crystal molecules and voltage
(Left: No voltage applied Right: Voltage applied)

The two panels that enclose the liquid crystal, known as "alignment films," are grooved. The liquid crystal molecules line up along these grooves. When the grooves are rotated 90 degrees, the liquid crystal molecules are also twisted 90 degrees. When light that has been passed through a polarizing filter passes through the twisted molecules, this light is also twisted 90 degrees. The arrangement of the molecules in the liquid crystal can be changed by passing voltage through it. When the voltage is applied, the molecules line up with the electric field, untwisting them and allowing light to pass straight through the liquid crystal layer. This untwisted light is then blocked by the other polarizing filter, which prevents it from passing. By applying and then removing voltage, the light can be blocked or allowed to pass.

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Unlike ordinary consumer televisions and computer monitors, professional reference displays require a high level of precision with regard to image quality, color uniformity and luminance uniformity.

Canon has developed its own high-quality image processor and backlight to produce displays with high levels of image quality and precision that can leverage the full potential of professional video devices such as digital cinema cameras and broadcast lenses.
They also support state-of-the-art technologies including high dynamic range (HDR), which can depict a wider luminance range than standard dynamic range.

Canon's image processor, which uses proprietary technologies to achieve high precision computation, offers accurate color reproduction and uniform luminance.

High-quality Image Processor

A Proprietary Engine that Achieves High Image Quality and Precision

One of the most important pieces of equipment on a film or broadcast production site is a reference display, a device used to check the image quality of the content being produced. Having an reference device with image quality that meets the standards for film and broadcasting makes it possible to achieve the same high level of quality, regardless of where in the world the content is being created.
On video production sites that require high precision, reference values must be strictly adhered to. Therefore, image processors must incorporate functionality that include faithful color reproduction, accurate gradations, and high-precision uniformity, and they must be coordinated with the panel and backlight to achieve optimal on-screen correction and highly precise aging correction.
Canon has developed a new image processing engine capable of high-precision processing for its high-resolution 4K and 8K reference displays to ensure the visual expression, quality, and reliability demanded of reference displays. Furthermore, Canon has incorporated its imaging know-how, cultivated over its long history of camera development, into its algorithms to achieve a high level of image quality. Canon is dedicated to quality and performs highly precise adjustments before shipping to ensure that each unit achieves the faithful color reproduction, high-precision uniformity, and long-term consistency expected of the company's reference displays.

Backlights that Produce a Wide Color Gamut and High Luminance

Canon's professional reference displays employ a 4K or 8K high-resolution, wide-viewing-angle in-plane-switching (IPS) liquid crystal panel unit that enables the display of high-resolution, high-quality content that meets DCI cinema standards and UHD broadcasting standards.
Canon uses high-purity LEDs for its backlights, thus achieving a wider color gamut. This makes possible faithful reproduction of rich colors that would not be possible on older display models.
What's more, due to recent advances in HDR technology, Canon's professional reference displays were among the first in the video production industry to support HDR standards (HLG: Hybrid Log Gamma, PQ: ST2084). To achieve high luminance and contrast, Canon's displays incorporate more backlight LEDs than conventional standard-dynamic-range (SDR) displays as well as optimized circuit patterns and boards to ensure consistency even at high luminance levels.

HDR is a technology capable of expressing a wider brightness range than SDR. Thanks to Canon's proprietary image processing engine design and backlight technology, the company's professional reference displays deliver high-definition 4K and 8K images with high luminance and accurate gradations, enabling a level of visual expression in video production not possible with conventional SDR.
For example, the details of clouds in a blue sky, which might have been clipped whites when using SDR, can be clearly seen when using HDR thanks to its improved overall contrast. In addition, HDR expands not only the range of brightness (luminance) but also the range of colors that can be expressed (color volume). This means that HDR enables reproduction of a wider range of natural colors, making images look more realistic and three-dimensional.
Display firmware also features several HDR monitoring assistance functions, for which Canon was presented an Engineering Excellence Award at the 2018 Hollywood Professional Association (HPA) Awards. Users who create HDR content require functions for quantitatively assessing input signals. The functions of Canon professional reference displays, such as displaying a histogram showing the luminance distribution in graph form, and the false color function, which uses false colors to indicate brightness in an intuitive way, have been met with glowing praise.

color volume

Canon will continue striving to enhance the convenience of HDR workflows and efficiently develop products that support even higher resolutions and luminance.