Distance Calibration between Reference Plane and Screen in Direct Phase Measuring Deflectometry

Shujun Huang, Yue Liu, Nan Gao, Zonghua Zhang, Feng Gao, Xiangqian Jiang

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

The recently developed direct phase measuring deflectometry (DPMD) method can directly measure the three-dimensional (3D) shape of specular objects with discontinuous surfaces, but requires a calibrated distance between a reference plane and liquid crystal display screen. Because the plane and screen are different distances from the imaging device, they cannot be clearly captured given the limited depth of field (DOF) of the lens. Therefore, existing machine vision-based methods cannot be used to effectively calibrate a DPMD system. In this paper, a new distance calibration method that uses a mirror with a hollow ring matrix pattern and a mobile stage is presented. The direction of the mobile stage in the camera coordinate system is determined by the mirror’s pattern at several positions in the camera’s DOF so that the reference position outside of the DOF can be calculated. The screen’s position can also be calibrated by displaying patterns at a known scale. Therefore, the required distance is accurately obtained in the camera coordinate system. Evaluation results show that the maximum value of the absolute error is less than 0.031 mm. The experimental results on an artificial stepped mirror and a reflected diamond distribution surface demonstrate the accuracy and practicality of the proposed method.
LanguageEnglish
Article number144
Number of pages15
JournalSensors
Volume18
Issue number1
DOIs
Publication statusPublished - 6 Jan 2018

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Calibration
Mirrors
Cameras
cameras
mirrors
Diamond
Liquid crystal displays
Liquid Crystals
Computer vision
Lenses
Diamonds
computer vision
Imaging techniques
hollow
diamonds
liquid crystals
lenses
Equipment and Supplies
evaluation
rings

Cite this

@article{1147ca586d204991bdbc7a1ad137868f,
title = "Distance Calibration between Reference Plane and Screen in Direct Phase Measuring Deflectometry",
abstract = "The recently developed direct phase measuring deflectometry (DPMD) method can directly measure the three-dimensional (3D) shape of specular objects with discontinuous surfaces, but requires a calibrated distance between a reference plane and liquid crystal display screen. Because the plane and screen are different distances from the imaging device, they cannot be clearly captured given the limited depth of field (DOF) of the lens. Therefore, existing machine vision-based methods cannot be used to effectively calibrate a DPMD system. In this paper, a new distance calibration method that uses a mirror with a hollow ring matrix pattern and a mobile stage is presented. The direction of the mobile stage in the camera coordinate system is determined by the mirror’s pattern at several positions in the camera’s DOF so that the reference position outside of the DOF can be calculated. The screen’s position can also be calibrated by displaying patterns at a known scale. Therefore, the required distance is accurately obtained in the camera coordinate system. Evaluation results show that the maximum value of the absolute error is less than 0.031 mm. The experimental results on an artificial stepped mirror and a reflected diamond distribution surface demonstrate the accuracy and practicality of the proposed method.",
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Distance Calibration between Reference Plane and Screen in Direct Phase Measuring Deflectometry. / Huang, Shujun; Liu, Yue; Gao, Nan; Zhang, Zonghua; Gao, Feng; Jiang, Xiangqian.

In: Sensors, Vol. 18, No. 1, 144, 06.01.2018.

Research output: Contribution to journalArticle

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