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  1.   Trademarks
  2. 1Introduction
  3. 2Determining the Right Brightness for Your Product
  4. 3The Impact of Ambient Light Level
  5. 4The Impact of Screen Size
  6. 5Trade-Offs Associated With Brightness
  7. 6Other Considerations
  8. 7Summary
  9. 8Additional Resources
  10. 9Revision History

1 Introduction

Brightness requirements are one of the key considerations to account for when designing any projection system.

The terms projector brightness and image brightness are used throughout this paper. Here is how they are defined for the sake of this paper:

  • Projector brightness is the amount of visible light emitted from a projector or projection system(5). It is measured in ANSI(2) lumens (lm) and is independent of image size. With TI DLP technology, it is possible to create projectors spanning a broad brightness range: from 30 lumens for projectors embedded into products like smartphones or tablets, to over 10,000 lumens for large venue projectors. Projection systems can include several different types of illumination sources including lamps, LEDs, and lasers. Factors that impact projector brightness include illumination source type (lamp, LED, or laser), illumination source output capability (radiant watts), illumination source input power (electrical), optical design, and the DLP active array area.
  • Image brightness is a measure of the brightness of an image reflected off of a surface. It is measured in nits (candelas per square meter) and is proportional to lumens per square meter projected onto the surface.(3) For a fixed display area (image size), the more lumens a system can output, the higher the nits. Likewise, for a fixed number of lumens from the projection system, the smaller the display area, the higher the nits. Image brightness also depends on the projection surface; different surfaces have different reflective characteristics, but exploring the impact and trade-offs of surface characteristic is beyond the scope of this document.

The term projector can often have limiting connotations. Classically, a projector is a system used only to display a video or image on a wall, and while this is still the case, projection systems can be utilized to display any form of visuals or infographics on virtually any display surface. These can be used for smart home displays, digital signage, laser TVs, and many other potential applications. DLP technology enables projection systems of many sizes for use in countless applications, in addition to supporting bright, vivid displays for classically defined projectors.

The two of the most frequently asked questions from customers who are new to TI DLP technology are: “How much brightness is needed for my application,” and “how bright can the projection system get?” In other words:

  • What is the right brightness (in lumens) for my product, given the application and user environment?
  • Given specific power size and cost requirements, what is the maximum brightness that my product can achieve?

The first question is often asked by product developers for whom image quality is the highest priority, whereas the second question is often asked by product developers who have certain technical constraints, most frequently power, size, and cost, which will ultimately constrain the maximum brightness of the projection system.

5. Projector brightness is technically defined as luminous flux, which is the energy within the visible wavelengths radiated from a source per unit time. The SI unit of luminous flux is the lumen.
2. ANSI (American National Standards Institute) lumens are measured by averaging the brightness of nine points across the projected image, thus taking into account differences in brightness uniformity across different projectors.
3. Technically, for an arbitrary reflector (surface), Nits = (Lumens × Screen Gain) / (π × m2), but a discussion about screen gain is outside the scope of this application note. In this application note, it is being assumed that all reflective surfaces are Lambertian with a screen gain of 1 unless otherwise noted.