Switchable Back Wall for Shadow-Free Face Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing recording systems for optical face detection face challenges in varying lighting conditions and limited space at border checkpoints, where they must provide shadow-free illumination and allow security personnel to maintain visibility, while also being adaptable to different structural situations.
Innovation Solution
A recording system with a rear wall that can be switched between opaque and transparent configurations using thermochromic or electrosensitive materials, allowing for adjustable light transmission and preventing shadows, combined with a lighting system that illuminates the person from the side and uses a light guide to ensure shadow-free image capture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a stationary, opaque backdrop is used for recording, then shadow-free illumination and ISO/IEC compliant images are achieved, but security personnel cannot see the area behind the backdrop
Solution Approach 1:
The backdrop is transformed from a static opaque structure to a dynamic switchable system that can change between opaque and transparent states. This allows the backdrop to adapt its optical properties based on operational requirements, resolving the contradiction between maintaining image quality compliance and enabling security visibility.
Solution Approach 2:
The optical parameters of the backdrop (transparency/opacity) are changed on demand using electrochromic or liquid crystal materials. By controlling the transmission coefficient of the backdrop material, the system can switch between providing shadow-free illumination for compliant images and allowing visibility for security monitoring.
2Ease of manufacture
If the backdrop is placed against a wall for structural stability, then positioning is simplified, but security personnel cannot see through the backdrop to monitor the area behind
Solution Approach 1:
The backdrop incorporates switchable transparency materials that allow it to be installed in fixed positions against walls for structural stability, while still enabling dynamic control over visibility. Security personnel can switch the backdrop to transparent mode when monitoring is needed.
3Measurement precision
If lighting is positioned to illuminate the face directly, then facial features are clearly captured, but shadows are cast on the face
Solution Approach 1:
The lighting system uses multiple light sources positioned at different locations (front, side, and back lighting) to provide uniform illumination across the entire face. This distributed lighting approach ensures that no single shadow is cast, while still capturing clear facial features for identification.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables secure, shadow-free facial image capture while allowing security personnel to monitor the area behind the rear wall, enhancing security and compliance with ISO/IEC standards, and accommodating varying lighting conditions.
Implementation Method 1
an opaque configuration, in which light originating from at least a predetermined spectral range and incident on the back of the back wall is absorbed or reflected from the back
Implementation Method 2
an opaque configuration, in which light originating from at least a predetermined spectral range and incident on the back of the back wall is absorbed or reflected from the back
Implementation Method 3
the possibility of using a thermochromic material for the back wall, which changes light absorption depending on the temperature
Implementation Method 4
the back panel can be electrosensitively switched between the opaque configuration and the transmission configuration
Implementation Method 5
use electrically switchable LC glass (liquid crystal) or PDLC glass (polymer-dispersed liquid crystal)
Implementation Method 6
the front panel acts as a light guide, such that light coupled into the front panel can be coupled out via the front of the back wall
Implementation Method 7
the front panel has a multitude of particles and/or defects designed to scatter incident light
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
The invention relates to a recording system (100) for optically capturing at least one face (102) of a person (104), comprising a camera (106) whose optics are directed towards a rear wall (112) forming a background for the recording, which has a front (108) facing the camera (106) and a rear (110) facing away from the camera (106), and a lighting device (114) configured to illuminate the rear wall (112) and/or the person (104). The back wall (112) is configured to be switched between an opaque configuration, in which light originating from at least a specified spectral range and incident on the back (110) of the back wall (112) is absorbed or reflected from the back (110), and a transmission configuration, in which light incident on the back (110) of the back wall (112) is transmitted to the front (108) of the back wall (112).The invention also relates to a method for optically detecting at least one face (102) of a person (104).