title: Optical Techniques for Fruit Firmness Assessment

authors: Rowe, Philip

subjects: Fruit

abstract: This thesis describes the design and development of a new high-speed multispectral imaging (MSI) system compatible with a commercial grading line. The purpose of this system was to carry out spatially resolved spectroscopy to assess fruit firmness. Captured images were analysed using diffusion theory and modified Lorentzian models to extract a sample’s optical properties (absorption and reduced scattering coefficients) and optical parameters respectively. The high-speed MSI system was designed to capture images of fruit using a high-resolution complementary metal–oxide–semiconductor camera, 12.5 mm lens, and discrete lasers operating at 685, 850, and 904 nm. Each laser illuminates a separate fruit, and the camera captures the interacting light with a single frame encompassing all three fruit. Depending on the size of each fruit the spatial resolution with the 12.5 mm lens ranged from 0.15 to 0.22 mm/pixel.

Initial measurements were made on 200 ‘Royal Gala’ apples to identify the relationships between the optical properties or parameters and either acoustic or the industry standard penetrometer firmness measurements. Performance of the high speed MSI system was poor compared to the results seen in the literature using alternative spatially resolved spectroscopic systems and other apple varieties. Only weak correlations (R = 0.33) were found between the individual optical measurements and firmness. 

Unsatisfactory performance from the high-speed system led to the development of a static MSI system to measure stationary fruit and the development of an inverse adding-doubling (IAD) system to provide an independent measurement of the samples optical properties. The purpose of these systems was to help understand the measurement, reduce variability, and give an indication of the upper level of performance possible. The static MSI system featured a number of improvements  including the addition of a 980 nm laser, the elimination of an asymmetry caused by laser polarisation, improved temperature control, an electronic shutter system, precise location control of the fruit, and a new 25 mm lens improving spatial resolution (0.057mm/pixel).

A second study was carried out using the new MSI and IAD systems on 92 ‘Royal Gala’ apples. Fruit were sliced to expose a flat measurement surface eliminating variation caused by fruit curvature and skin pigments. With these refinements and simplifications the relationships between optical properties or parameters and penetrometer firmness strengthened. As fruit softened and penetrometer firmness fell the reduced scattering coefficient measured by both the IAD and MSI system increased with correlation coefficients ranging from -0.62 to -0.70. The absorption coefficients measured by the two systems showed the expected features related to the absorption of chlorophyll and carotenoid pigments, and water absorption. As the fruit softened chlorophyll absorption decreased as the pigments are broken down and carotenoid absorption increased as new pigments are synthesised. No useful relationships were identified between the optical measurements and acoustic firmness. Multiple linear regression models were formed to predict penetrometer firmness using either the optical properties or modified Lorentzian parameters. The best performing model used a combination of the absorption and scattering coefficients, and had a correlation coefficient of 0.8 and a standard error of 5.87 N.

text: Optical Techniques for Fruit Firmness Assessment This thesis describes the design and development of a new high-speed multispectral imaging (MSI) system compatible with a commercial grading line. The purpose of this system was to carry out spatially resolved spectroscopy to assess fruit firmness. Captured images were analysed using diffusion theory and modified Lorentzian models to extract a sample’s optical properties (absorption and reduced scattering coefficients) and optical parameters respectively. The high-speed MSI system was designed to capture images of fruit using a high-resolution complementary metal–oxide–semiconductor camera, 12.5 mm lens, and discrete lasers operating at 685, 850, and 904 nm. Each laser illuminates a separate fruit, and the camera captures the interacting light with a single frame encompassing all three fruit. Depending on the size of each fruit the spatial resolution with the 12.5 mm lens ranged from 0.15 to 0.22 mm/pixel.

Initial measurements were made on 200 ‘Royal Gala’ apples to identify the relationships between the optical properties or parameters and either acoustic or the industry standard penetrometer firmness measurements. Performance of the high speed MSI system was poor compared to the results seen in the literature using alternative spatially resolved spectroscopic systems and other apple varieties. Only weak correlations (R = 0.33) were found between the individual optical measurements and firmness. 

Unsatisfactory performance from the high-speed system led to the development of a static MSI system to measure stationary fruit and the development of an inverse adding-doubling (IAD) system to provide an independent measurement of the samples optical properties. The purpose of these systems was to help understand the measurement, reduce variability, and give an indication of the upper level of performance possible. The static MSI system featured a number of improvements  including the addition of a 980 nm laser, the elimination of an asymmetry caused by laser polarisation, improved temperature control, an electronic shutter system, precise location control of the fruit, and a new 25 mm lens improving spatial resolution (0.057mm/pixel).

A second study was carried out using the new MSI and IAD systems on 92 ‘Royal Gala’ apples. Fruit were sliced to expose a flat measurement surface eliminating variation caused by fruit curvature and skin pigments. With these refinements and simplifications the relationships between optical properties or parameters and penetrometer firmness strengthened. As fruit softened and penetrometer firmness fell the reduced scattering coefficient measured by both the IAD and MSI system increased with correlation coefficients ranging from -0.62 to -0.70. The absorption coefficients measured by the two systems showed the expected features related to the absorption of chlorophyll and carotenoid pigments, and water absorption. As the fruit softened chlorophyll absorption decreased as the pigments are broken down and carotenoid absorption increased as new pigments are synthesised. No useful relationships were identified between the optical measurements and acoustic firmness. Multiple linear regression models were formed to predict penetrometer firmness using either the optical properties or modified Lorentzian parameters. The best performing model used a combination of the absorption and scattering coefficients, and had a correlation coefficient of 0.8 and a standard error of 5.87 N.

year: 2015

title: The time machine. Norman Taylor Memorial Lecture 2002

authors: Lowe, David J.

abstract: I've chosen to talk about five topics dealing with longstanding pedological or paleoenvironmental problems involving tephrostratigraphy. I'll begin with the oldest tephras and work 'stratigraphically upwards' to the youngest. Along the way I'll mention or show a few of the people I've worked with, or who were involved historically in the research areas. I've allowed around five or six minutes for each topic (but I'd be grateful if you didn't set your stopwatches!). As promised, the second part of the talk will begin when we reach the year 1952. Among a range of personal observations relating to the birth of the society and to Norman Taylor, I will attempt to explain how I came to be giving this lecture today.

text: The time machine. Norman Taylor Memorial Lecture 2002 I've chosen to talk about five topics dealing with longstanding pedological or paleoenvironmental problems involving tephrostratigraphy. I'll begin with the oldest tephras and work 'stratigraphically upwards' to the youngest. Along the way I'll mention or show a few of the people I've worked with, or who were involved historically in the research areas. I've allowed around five or six minutes for each topic (but I'd be grateful if you didn't set your stopwatches!). As promised, the second part of the talk will begin when we reach the year 1952. Among a range of personal observations relating to the birth of the society and to Norman Taylor, I will attempt to explain how I came to be giving this lecture today.

year: 2002

title: He Paiaka Totara: Māori Psychologists Wānanga, report to Ngā Pae o te Māramatanga

authors: Waitoki, Waikaremoana

abstract: Sustainability for the growing number of Māori psychologists depends on a resilient system that reflects the centrality of Māori knowledge, tikanga, kawa and moemoea. Paiaka refers to whakapapa, identity, roots and connectedness. As Māori psychologists how we might use this term with Māori whānau and each other differs according to our own unique skills and abilities - our pūmanawa. (He Paiaka wānanga, August, 29, 2015).

text: He Paiaka Totara: Māori Psychologists Wānanga, report to Ngā Pae o te Māramatanga Sustainability for the growing number of Māori psychologists depends on a resilient system that reflects the centrality of Māori knowledge, tikanga, kawa and moemoea. Paiaka refers to whakapapa, identity, roots and connectedness. As Māori psychologists how we might use this term with Māori whānau and each other differs according to our own unique skills and abilities - our pūmanawa. (He Paiaka wānanga, August, 29, 2015).

year: 2016