BRDF Measurement Using Environment Maps for External Light Compensation

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Solution Overview

Problem

Conventional methods for estimating the Bidirectional Reflectance Distribution Function (BRDF) of real objects fail to accurately account for external light and indirect light, leading to measurement errors, especially in environments with surrounding reflections, and require restrictive conditions like darkrooms or black-painted frames to minimize external light influence.

Innovation Solution

An image processing apparatus that acquires environment maps and captured images from multiple directions to determine reflection characteristics of objects, considering direct and indirect light sources, using a system with a CPU, image input device, and segmentation solid angles to estimate BRDF without restrictive measurement environments.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If conventional BRDF measurement techniques are used that assume parallel illumination light, then the measurement process is simplified, but measurement accuracy degrades in environments with external light and reflected light from surrounding frames

Engineering Contradiction:

Improvemeasurement process complexityVSAvoidBRDF measurement accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent converts the harmful effect of external light and reflected light into a beneficial factor by incorporating environment maps that capture the complete lighting environment. Instead of treating external light as noise to be eliminated, the system uses it as data to compute the actual incident light distribution, thereby improving measurement accuracy without requiring restrictive darkroom conditions

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent changes the measurement approach by transitioning from assuming parallel illumination to actually measuring the incident light distribution through environment maps. This parameter change allows the system to account for the true lighting conditions including external light sources and reflected light, resolving the contradiction between measurement simplicity and accuracy

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If restrictive measurement environments like darkrooms or black-painted frames are used to eliminate external light influence, then measurement accuracy improves, but the ease of operation and adaptability of the measurement system deteriorates

Engineering Contradiction:

ImproveBRDF measurement accuracyVSAvoidmeasurement environment setup convenience

Core Design Contradiction:

Measurement precisionVSEase of operation

Solution Approach 1:

The patent eliminates the need for restrictive measurement environments by converting external light from a harmful factor into useful measurement data. The environment map captures the complete lighting environment including external light sources, allowing the system to compute accurate incident light distribution without requiring darkrooms or special frame treatments

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent creates a universal measurement system that can operate in any lighting environment by using environment maps to adapt to the actual conditions. The system is no longer restricted to specific environments like darkrooms but can function universally across different lighting conditions, improving ease of operation and adaptability

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Device complexity

If the assumption of parallel illumination light is made for simplicity, then the measurement model is simplified, but error increases particularly for three-dimensional objects where object size is significant relative to light source distance

Engineering Contradiction:

Improvemeasurement model complexityVSAvoidBRDF measurement accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent replaces the simplified mechanical assumption of parallel illumination with an actual optical measurement system using environment maps. This substitution allows the system to capture the true incident light distribution from multiple directions, accurately accounting for the three-dimensional geometry of objects without requiring complex computational models

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS10593026B2Image processing apparatus, image processing method, and storage medium

Publication Date: 2020.03.17 CANON KK

AI summary

An apparatus includes a first acquisition unit configured to, with a viewpoint set to a position of an object, acquire a plurality of environment maps for each position of light sources, the environment maps being obtained by imaging a surrounding environment from the viewpoint, a second acquisition unit configured to acquire a plurality of captured images for each position of the light sources, the captured images being obtained by imaging from a plurality of directions the object irradiated with light by the light sources, and a determination unit configured to determine reflection characteristics of the object based on the environment maps and the plurality of captured images.