DLPA073A September   2016  – September 2016 DLP2010 , DLPC2607 , DLPC3430 , DLPC3435

 

  1.   TI DLP Pico Technology for Aftermarket Head-up Displays
    1.     Trademarks
    2. 1 Introduction
    3. 2 Applicable Documents
    4. 3 Terminology
      1. 3.1 Types of AM-HUD
      2. 3.2 HUD Terminology
    5. 4 AM-HUD Key Requirements
      1. 4.1 Field of View
      2. 4.2 Resolution
      3. 4.3 Virtual Image Distance
      4. 4.4 Eyebox
      5. 4.5 Image Brightness
    6. 5 AM-HUD System
    7. 6 AM-HUD System Design Trade-Offs
      1. 6.1 Light Output vs. Eyebox and Field of View
      2. 6.2 Combiner and Diffuser Specification
        1. 6.2.1 Diffuser Screen Dimensions
        2. 6.2.2 Combiner Specification
      3. 6.3 Projection Unit Specification
    8. 7 Electronic System
    9. 8 Conclusions and Getting Started
  2.   Revision History

6.3 Projection Unit Specification

An existing DLP projection engine can be used in an AM-HUD design. The key specifications for projection units are brightness, throw ratio, resolution and minimum focus distance. In this section, these values are calculated.

Brightness

The total light output from a projector is measured in lumens. The following factors need to be considered in estimating the required light output from the projector:

  • Combiner reflectivity ~ 20%
  • Diffuser transmission efficiency ~ 90%
  • The diffuser's light scatter is normally larger than the eyebox. Only approximately 40-50% of light reaches the eyebox.
  • Imaging Area Utilization

The aspect ratio of the HUD image in this example is 12:6 and the suggested DLP panel (WVGA) has an aspect ratio of 16:9. The resulting HUD image is formed by a subset of the panel's available area, according to the following equation:

eqn_ar_4.png

Throw Ratio

The following equations can be used to calculate distance between projection unit and combiner:

eqn_ar_5.png

Projection unit specification is shown in Table 4:

Table 4. Projection Unit Specification

Features Values
Brightness ~45 lumens
Resolution WVGA (854x480)
Minimum focus distance 77 mm
Throw ratio ~1.74