An Innovative Method for 3-D Shape, Strain and Temperature Full-Field Measurement Using a Single Type of Camera: Principle and Preliminary Results

Abstract

An innovative technique for measuring both the shape, the displacement, the strain and the temperature fields at the surface of an object using a single stereovision sensor is proposed. The sensor is based on two off-the-shelf low-cost high-resolution uncooled CCD cameras. To allow both dimensional and thermal measurements, the sensor operates in the visible and near infrared (NIR) spectral band (0.7-1.1 µm), and a radiometric and geometric calibration of the sensor is required. This technique leads to a low-cost camera-based simplified instrumentation that gives simultaneously dimensional/kinematical and thermal field measurements.Key words: geometric camera calibration, radiometric camera calibration, shape measurements, strain measurements, temperature measurements, full-field measurements, stereovision, digital image correlation (DIC), stereo-correlation, 3-D metrology, experimental mechanics. Preprint submitted to Experimental MechanicsJune 2007 1 Introduction For temperature measurements, many sensors are also available, from the classical thermocouples up to more sophisticated non-contact sensors like infrared cameras or pyrometers [14,15]. Thus, getting the strains and temperature at the same time implies generally a multi-instrumentation of the set-up and it is not so easy to combine the measurements of various categories in order to get the strains and the temperature at a given point of the specimen surface. 2 classical thermocamera with the 3-D shape data provided by a stereovision sensor. Their technique requires three cameras (an IR camera and two CCD cameras for the stereovision sensor) and a specific calibration procedure is needed to perform the fusion of the thermal and kinematical data provided by two different types of cameras. Satzger et al. [17] propose to utilize an infrared camera with a fringe projection technique to obtain a cloud of 3-D points and

Hybrid Stereocorrelation Using Infrared and Visible Light Cameras

“…One of the advantages of projecting the temperature fields onto a 3D model is to be able to perform emissivity corrections since it depends on the observation angle [12]. Two CCD cameras and a technique exploiting the sensitivity of the sensors in the near infrared radiations allows SC and temperature measurements to be performed [13]. However, this technique is applicable for very high temperature experiments (i.e., above 300 °C).…”

“…The temperature is kept constant even though methods exist to consider temperature changes [25]. It is also possible to measure temperature changes as digital level variations [13], [25]. Therefore a gray level relaxation accounting for brightness and contrast readjustments [7], [9], [28] takes into account such effects.…”

Contactless Monitoring of Shrinkage and Temperature Distribution during Hybrid Microwave Sintering

“…[7] This near IR and visible emission is collected by the CCD camera and converted digitally into intensity levels. Relationships between each intensity level and the temperature are given by calibration with a pyrometer.…”

Application of a Multi‐Camera Stereo DIC Set‐up to Assess Strain Fields in an Erichsen Test: Methodology and Validation

“…Moreover, the image has already been significantly blurred at the far end of the specimen. Consequently, most of the applications and investigations of the stereo DIC are confined to measure limited out‐of‐plane deformations [7–17]. To obtain a complete full field and gain accuracy in cases such as the one shown in Figure 1, an idea of multi‐camera stereo DIC set‐up has been introduced in the past, where ‘multi‐camera’ refers to three or more cameras.…”