This week in the Display 101 series we are talking about the viewing angle of smart displays, and how to choose the right viewing angle for your project.
Viewing angle explained
The viewing angle is the maximum angle at which the user can see the image with the acceptable quality.
Its concept is closely related to the grey scale inversion phenomenon. When the user exceeds a certain angle (viewing angle), he can note a sudden change of displayed colors. It mainly emerges with the grey color’s domination in the displayed image.
The viewing angle is measured from the display’s normal axis to each of the four directions. Theoretically, the maximum angle is 90° and it might vary for each measuring direction. The three-dimensional angular range is called a viewing cone.
The most popular matrix types on the market are TN, VA, MVA, and IPS.
TN type is the most cost-efficient technology. The angles are mostly narrower than in case of the other types, but low prices and short matrix reaction time compensates the smaller viewing cone. In order to extend the viewing angles, O-film can be added to the display. When buying TN-type display you should always pay attention to the viewing direction expressed in hour angle. It describes the direction from which the user should look at the display.
VA and MVA types are characterized by a rather short reaction time, wide angles and high contrast. It classifies them somewhere between TN and IPS type.
IPS matrix technology has not only most of VA’s advantages but also very good color reproduction and highest viewing angles in both axes. The most common IPS disadvantage is the black color depth which is lower than in VA type.
What viewing angle I need for my module?
If the application requires high viewing angles, the display with full viewing angles (178.5°~180° in each axis) should be chosen. In this case, you should look for MVA and IPS type displays.
When the price is the most important factor you can find a cost optimization in buying TN type displays.
Remember to check the right viewing direction for your application. The simplest rule is to choose a 12 o’clock display when a user is looking at it from the top direction, and 6 o’clock display when looking from the bottom.
NOTE: Do not mistake the viewing direction with greyscale inversion. Greyscale inversion is always opposite to the viewing direction. For example, the 12 o’clock display will have a color inversion at 6 o’clock.
The intermediate solution is the TN type with viewing angles extended by adding O-film. The O-film solution we already described in one of the previous articles: