Face Positioning & Camera Alignment

Correct face positioning is critical to ensure reliable physiological signal extraction (heart rate, breathing rate, etc.) during a scan.

The Saphere widget continuously analyzes the camera stream to verify that:

• A human face is detected
• The face is fully visible within the camera frame
• The face is centered and correctly aligned
• The face is at an appropriate distance from the camera
• The upper chest area is also visible to support breathing analysis

When one or more of these conditions are not met, the widget displays real-time positioning guidance messages to the end user. These messages are intended to help the user adjust their position before the scan, in order to restore valid capture conditions.

Positioning Messages & Their Meaning

Each message below corresponds to a specific framing or detection condition that is not currently satisfied.

The dashed guides displayed on the camera preview represent the detected position and size of the face and upper chest regions used for signal extraction..

🟡 “Please put your face in front of the camera”

What this means (user-facing)

No face is currently visible to the camera.

Why this message is shown (technical)

• No human face is detected in the camera frame
• Face detection confidence is below the required threshold

What the user should do

• Positioning their face directly in front of the camera
• Ensure their face is clearly visible and unobstructed

🟡 “Please move to the right”

What this means (user-facing)

Part of the face is outside the left side of the camera frame.

Why this message is shown (technical)

• The detected face bounding box exceeds the left boundary of the frame
• Some facial landmarks are missing or partially visible

What the user should do

• Move slightly to the right
• Keep their entire face inside the camera frame

🟡 “Please move to the left”

What this means (user-facing)

Part of the face is outside the right side of the camera frame.

Why this message is shown (technical)

• The detected face bounding box exceeds the right boundary of the frame

What the user should do

• Move slightly to the left
• Center their face within camera frame

🟡 “Please move down”

What this means (user-facing)

The face is positioned too high in the camera frame.

Why this message is shown (technical)

• The upper part of the face exceeds the top boundary of the frame
• Some facial regions may be cropped

What the user should do

• Lower their head slightly
• Keep their full face inside the camera frame

🟡 “Please move upwards”

What this means (user-facing)

The face is correctly visible, but the upper chest area is not fully inside the frame.

Why this message is shown (technical)

• Breathing rate computation requires capturing both the face and the chest
• The chest region extends below the camera frame
• The chest framing height is expected to be equal to the face height

What the user should do

• Move slightly upwards or slightly away from the camera
• Ensure both their face and their upper chest are visible

🟡 “Please move forward slightly”

What this means (user-facing)

The face is too far from the camera.

Why this message is shown (technical)

• The detected face size is below the minimum threshold (≈ 150 pixels)
• Signal quality is insufficient at this distance

What the user should do

• Move slightly closer to the camera
• Keep a natural, frontal posture

🟡“Please move back slightly”

What this means (user-facing)

The face is too close to the camera.

Why this message is shown (technical)

• The face and chest region exceeds the camera frame
• Some areas are clipped or outside the visible region

What the user should do

• Move slightly away from the camera
• Keep their entire face and chest inside the guide

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