Hardware and Software for Capturing HDR Light Fields

Last edited on: July 17, 2021 12:57 AM

This project aims to design a system that captures HDR light fields to generate image-based 3D reconstruction for display on the HDR multi-focal stereoscope. The setup consists of an Arduino used to control the Stepper Motor and a Raspberry Pi used to send instructions to the Arduino and capture/receive images from the camera.

Hardware design

Arduino wiring

The Stepper Driver used in this setup is DQ542MA and the Stepper Motor used is NEMA 17 42BYGH-W811.

Connection between Stepper Driver and Arduino:

  • PUL+ from Driver to Arduino PIN7
  • PUL- from Driver to Arduino PIN5
  • DIR+ from Driver to Arduino PIN7
  • DIR- from Driver to Arduino PIN6
  • ENBL+ from Driver to Arduino PIN7

Connection between Stepper Driver and Stepper Motor:

  • A+ from Driver to Stepper BLACK wire
  • A- from Driver to Stepper GREEN wire
  • B+ from Driver to Stepper RED wire
  • B- from Driver to Stepper BLUE wire

Connection between Button and Arduino:

  • Button YELLOW wire to Arduino PINA0

DIP switch setting

The first three bits of the DIP switch are used to set the dynamic current. For an output current of 2.37A, SW 1, 2, 3 is set to OFF, OFF, ON.

Micro step resolution is set by the last four bits of the DIP switch. For 1600 pulse per revolution, SW 5, 6, 7, 8 is set to OFF, OFF, ON, ON.

Power supply

The power supply for the Stepper Driver is 18V (3 parallel sets of 2 9V batteries in series).

Serial communication with Python

Dependencies

Installing libgphoto2:

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sudo apt-get install libgphoto2-dev

Installing python-gphoto2 and pySerial for python3 with pip:

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sudo pip3 install gphoto2
sudo pip3 install pyserial

Usage Examples

Specify the port and baud rate for the serial communication between Arduino and Raspberry Pi in python/camera.py:

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port = '/dev/ttyACM0'
baud_rate = 9600

Set the parameters for HDR Light Field capture in python/gui.py:

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camera_name = 'SonyA7r1'
# hdr_merging = False

(Optional) Merge the captured images into HDR light field (requires OpenCV):

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from merge import merge_light_field
merge_light_field(capture_path, camera_name, n_exposures)

GUI design with python

GUI allows for basic motor and camera control:

  • Motor speed can be set from 1 to 10. (disabled)
  • Camera location can range from 0 to 1000.
  • Number of exposures and stops can be set according to camera settings.
  • Number of views can range from 1 to 1001.
  • Click Capture to capture a single image.
  • Click Capture LF to capture HDR light field.

Uncomment relevant code in python/gui.py to enable different controls.

Release History

  • 0.2.0
    • Edited code structure and added more controls
    • CHANGE: Seperate control.py into and control.py and gui.py
  • 0.1.0
    • The first proper release
    • CHANGE: Add arduino and python
  • 0.0.1
    • Work in progress
Computer Vision
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