DLPA116 October   2020 DLP2021-Q1 , DLP3021-Q1

 

  1.   Trademarks
  2. 1Static projection in automotive applications
  3. 2Brightness Requirements
    1. 2.1 Main Parameters that Influence Display Brightness
      1. 2.1.1 Ambient Lighting Conditions
      2. 2.1.2 Projection Surface Impact on Display Brightness
      3. 2.1.3 Size of the Displayed Image
      4. 2.1.4 Brightness of the Displayed Image
    2. 2.2 Other Brightness Considerations
      1. 2.2.1 Time of Day
      2. 2.2.2 Projector Contrast
      3. 2.2.3 Other Application Constraints
    3. 2.3 Brightness Capabilities with DLP Technology
  4. 3Summary
  5. 4References

2.1.4 Brightness of the Displayed Image

The estimated brightness of a DGP image can be calculated with the numbers provided in the previous sections. Combining image size, projection surface, ambient conditions, and projected lumens will give the brightness of the projected image, and this can be used to predict how visible the image will be in various ambient lighting conditions.

Equation 2. Projector Flux [ l m ] × Reflectivity Image Size [ m 2 ] × π = Image Brightness [ c d m 2 ]
Equation 3. L C R = ( Image Brightness+Ambient Brightness ) Ambient Brightness

Rearranging the above equations to solve for required projector flux (in lumens) as a function of LCR, ambient brightness, image size, and surface reflectivity, the equation becomes the following.

Equation 4. Projector Flux [ l m ] = Ambient Brightness [ c d m 2 ] × ( L C R − 1 ) × Image Size [ m 2 ] × π Reflectivity

As an example, assume the ambient lighting condition of asphault is 10 lux (approximate illuminance during twilight) and the desired image is 0.09 m2 (~18" diagonal) and has an LCR of 25. Using Equation 5, the 10 lux ambient illuminance on asphault gives an ambient luminance of

Equation 5. 10 [ lux ] π × 0.15 = 0.48 [ c d m 2 ]

Using Equation 4 and these ambient conditions, the minimum required projector brightness is

Equation 6. 0.48 [ c d m 2 ] × ( 25 − 1 ) × 0.09 [ m 2 ] × π 0.15 = 21.6 [ l m ]

For a large logo or animation projection (~18") displayed on asphault at twilight with high visibility (LCR of 25) the DGP projector would need to output slightly more than 20 lumens. This is a feasible brightness for a projector based on the DLP3021-Q1 automotive grade DMD.