Blooming - Bright Spots in the Point Cloud

Introduction

Blooming is a phenomenon in imaging where intense light saturates the sensor, causing unintended brightness and distortion in the image. This article explains the causes and effects of blooming and its implications in machine vision.

What is Blooming?

When light becomes too intense, the affected pixels on the camera sensor become “blinded” or over-saturated. This leads to blooming, and the excess light spills over into neighboring pixels, making them appear brighter than they should. The extent of this spillover depends on how bright the light source is.

Key characteristics

  • Over-saturation: The affected regions become completely white, losing all detail.

  • Localized or widespread: Blooming may affect the entire image or just specific areas.

  • Common causes: Direct light sources like the sun or bright lamps, or indirect reflections from specular surfaces.

Example 1: Sun Reflection on Water

When sunlight reflects off the ocean, it creates a large white spot in the image, making it hard to see any details in that area.

Blooming in the ocean image

Example 2: Dandelion in Front of the Sun

A dandelion in front of the sun may appear to glow orange in certain areas. This glow happens because bright sunlight spills into nearby pixels, making them appear brighter than they really are.

Blooming in the flower image

Causes and Consequences of Blooming

Blooming can cause problems in machine vision systems, especially when trying to capture accurate depth information. Common causes include:

Reflective Surfaces

Surfaces that reflect light (from ambient or projector) directly back into the camera, such as specular or smooth materials, can cause blooming. This reflection often saturates the camera sensor.

Depth Errors

Pixels that are too bright (over-saturated) cannot provide accurate depth measurements. The 3D data for these pixels is usually removed, leaving gaps or “holes” in the point cloud.

Example: Camera facing a Flat Surface

If a camera is placed directly above a flat surface like a table, light from the projector can reflect straight back into the camera. This creates white spots in the image and areas without depth data in the point cloud.

Blooming in the Zivid point cloud

For tips on how to reduce blooming and deal with its effects in color images and point clouds, please see Blooming.