Location: Sugarbeet and Bean ResearchTitle: Structured-illumination reflectance imaging (SIRI) for enhanced detection of fresh bruises in apples
|LU, YUZHEN - Michigan State University|
|LI, RICHARD - Michigan State University|
Submitted to: Postharvest Biology and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/8/2016
Publication Date: 2/15/2016
Citation: Lu, Y., Li, R., Lu, R. 2016. Structured-illumination reflectance imaging (SIRI) for enhanced detection of fresh bruises in apples. Postharvest Biology and Technology. 117:89-93.
Interpretive Summary: Imaging techniques, including broadband-based color and near-infrared, multispectral and hyperspectral, have been extensively researched over the past decades for quality or defect detection of horticultural products like apple. While some of these techniques are being widely used commercially, they are not quite effective in ascertaining tissue abnormalities beneath the surface, especially subtle defects like fresh bruise in fruit like apple. Hence a new, more effective technique is needed to meet the increasing needs for food quality evaluation by the horticultural and food industries. In this research, a structured-illumination reflectance imaging technique was developed for the detection of fresh bruises in apples. The technique utilizes spatially-modulated illumination to control light penetration and spatial detection resolution in the product. Experiments were conducted to acquire reflectance images from a strongly light-scattering simulation sample embedded with defects of different sizes at different depths from the surface as well as apple samples of two different cultivars with fresh bruises, under the structured illumination at different spatial frequencies. Image processing algorithms were then developed for demodulating the acquired images. Results showed that by changing the spatial frequency of the light illumination, this new imaging technique was able to enhance the detection of defects beneath the surface of the samples. Fresh bruises in the test apples were easily detected by the technique, which, otherwise, could not be achieved using conventional imaging technique. This new technique has great potential for effective detection of surface and subsurface defects in apples and other horticultural products.
Technical Abstract: A structured-illumination reflectance imaging technique was developed for the detection of fresh bruises in apples. Experiments were first conducted on a strongly scattering nylon sample embedded with foreign objects of different sizes at different depths, and then on apples of two different cultivars with fresh bruises. Compared to planar illumination, the amplitude images obtained by the technique were found more effective for ascertaining the sub-surface defects, and the detection resolution and depth depended on the spatial frequency of the structured illumination. The technique was able to detect fresh bruises in the test apples, which, otherwise, could not be detected by conventional uniform-illumination imaging technique.