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Focus Calibration for MirrorAphrodite

This guide explains how to calibrate the distance-to-focus mapping for the Arducam 64MP Hawkeyes camera used in the MirrorAphrodite smart mirror system.

Prerequisites

  1. Raspberry Pi with the Arducam 64MP Hawkeyes camera connected
  2. HC-SR04 ultrasonic distance sensor connected to GPIO pins 23 (trigger) and 24 (echo)
  3. Required Python packages installed (see requirements-calibration.txt)

Installation

  1. Install system dependencies:

    sudo apt update
sudo apt install -y python3-picamera2 python3-gpiozero python3-matplotlib python3-numpy

  2. Install Python dependencies:

    pip install -r requirements-calibration.txt

Running the Calibration

  1. Run the calibration script:

    python3 calibrate_focus.py

  2. Follow the on-screen instructions to calibrate focus at different distances.

Calibration Process

The calibration process involves the following steps:

  1. Measure Distance: The script uses the ultrasonic sensor to measure your current distance from the camera.

  2. Adjust Focus: You'll interactively adjust the focus value until the image appears perfectly sharp.

  3. Save Calibration Point: The distance and optimal focus value are saved as a calibration point.

  4. Repeat: Move to different distances and repeat the process to build a comprehensive calibration curve.

  5. Generate Mapping: After collecting enough data points, the script can generate the optimal distance-to-focus mapping.

Calibration Tips

  1. Collect Diverse Data Points: Try to collect data points at various distances, especially at:

    • Very close range (20-30cm)
    • Close range (40-60cm)
    • Medium range (70-100cm)
    • Far range (110-150cm)

  2. Consistent Lighting: Maintain consistent lighting conditions during calibration.

  3. Face Position: Keep your face centered in the frame during calibration.

  4. Fine Adjustments: Use the fine adjustment mode ('f' key) for precise focus tuning.

  5. Verify Results: After calibration, test the generated focus mapping at various distances.

Understanding the Output

The calibration script produces several outputs:

  1. JSON Data File: focus_calibration.json contains all calibration points.

  2. Calibration Curve: focus_calibration_curve.png shows the relationship between distance and focus.

  3. Code Snippet: distance_focus_map_code.txt contains the code to update in your distance_sensor.py file.

Applying the Calibration

After calibration, copy the generated distance_focus_map from the code snippet into the distance_sensor.py file to update the focus mapping.

Troubleshooting

  • Distance Sensor Issues: Ensure the HC-SR04 sensor is properly connected and not obstructed.
  • Camera Issues: Make sure the camera is properly connected and recognized by the system.
  • Focus Problems: If focus adjustment doesn't seem to work, restart the script and try again.