TIDUEE5A October   2018  – May 2022

 

  1.   Description
  2.   Resources
  3.   Features
  4.   Applications
  5.   5
  6. 1System Description
    1. 1.1 Key System Specifications
  7. 2System Overview
    1. 2.1 Block Diagrams
    2. 2.2 Design Considerations
    3. 2.3 Highlighted Products
      1. 2.3.1 DLP3030-Q1
      2. 2.3.2 DLPC120-Q1
      3. 2.3.3 TMS320F28023
    4. 2.4 System Design Theory
      1. 2.4.1 Head-up Display Parameter Design and Tradeoffs
        1. 2.4.1.1 Field of View and Eyebox
        2. 2.4.1.2 Resolution
        3. 2.4.1.3 Virtual Image Distance
      2. 2.4.2 Picture Generation Unit Design Decisions
        1. 2.4.2.1 Etendue Efficiency Match
        2. 2.4.2.2 Aperture Size: Selecting f/# of Optics
        3. 2.4.2.3 Thermal Design
        4. 2.4.2.4 LED Selection Summary
      3. 2.4.3 Design Summary
  8. 3Hardware, Software, Testing Requirements, and Test Results
    1. 3.1 Required Hardware and Software
      1. 3.1.1 Hardware
      2. 3.1.2 Software
    2. 3.2 Testing and Results
      1. 3.2.1 Test Setup
      2. 3.2.2 Test Results
  9. 4Design Files
    1. 4.1 Schematics
    2. 4.2 Bill of Materials
    3. 4.3 PCB Layout Recommendations
      1. 4.3.1 Layout Prints
    4. 4.4 Cadence Project
    5. 4.5 Gerber Files
    6. 4.6 Assembly Drawings
  10. 5Software Files
  11. 6Related Documentation
    1. 6.1 Trademarks
  12. 7Terminology
  13. 8Revision History

2.4.2.2 Aperture Size: Selecting f/# of Optics

The f/# of an optical system refers to the size of the aperture. For a DLP projector, there are apertures in the illumination and projection path, and typically the f/# of each one should match. The DLP3030-Q1 DMD has a tilt angle of ±12°, which corresponds to f/2.4, as dictated by the following angle-f/# relationship:

Equation 4. f/# = 1 / (2 × sin(θ))

However, an optical designer may prefer to open or close the aperture, by decreasing or increasing the f/# respectively. By opening the aperture, this allows more light to pass through and increases the brightness. However, this also allows light from the illumination- and flat-state pupils to leak into the off-state pupil, which raises the black level and degrades the contrast. Closing the aperture reducing the etendue match and allows less light through, but also increases the contrast by separating the pupils.

Figure 2-8 shows this tradeoff of contrast and brightness with a varying f/#. To support a HUD design with 1500:1 contrast, and aperture of f/2.6 should be used.

GUID-D28F4C2A-8F83-42C3-A085-22AE6F6D2EED-low.gifFigure 2-8 Picture Generation Unit Contrast and Brightness vs f/#