Kazuhiko Namba

Features Extraction for Eggplant Fruit Grading System Using Machine Vision

Machine vision based grading for agricultural crops has been well developed and accepted as an attractive grading method. However, machine vision based grading for eggplant fruit is not available yet. This study reports on the attempt to develop an eggplant grading machine using six CCD cameras as the sensing device. Feature extraction algorithms were developed to extract eggplants features, i.e., length, diameter, volume, curvature, color homogeneity, calyx color, calyx area, and surface defect. The system could acquire six images per fruits covering the entire surface of the eggplant fruits. An agreement rate of 78.0% was achieved in the feasibility study where the machine vision based grading was compared with manual grading. The throughput of the developed system was 0.3 second per fruit. Details of the system, an outline of the algorithm, and performance results are reported in this article.

Surface Gloss Measurement on Eggplant Fruit

Surface gloss is one of the important quality factors affecting consumers opinion on purchasing eggplant fruits. The current manual gloss grading method is subject to human bias and the outcome is often very ambiguous. This study developed a sensing device consisting of two CCD monochrome cameras and three long tungsten lights and an associated quantitative method of measuring surface gloss of eggplant fruit using the device. Distinguishing various glossiness states of the fruit were made possible by analyzing the specular reflectance of the fruit surface. Specular reflection of the light on fruit surface was measured by digital image analysis method. Gradient filter was applied on the gray-level image for measuring magnitude of intensity changes. The algorithm consistency and validation test on the samples showed the algorithm was feasible of quantitatively assessing eggplant fruit surface gloss with an accuracy rate of 0.806. Details of the sensing devices, outline of the algorithm and preliminary results are presented in this article.

Three-dimensional sensing system for agricultural robots

A three-dimensional sensing system that consisted of a laser scanner and a lift was developed for agricultural robot to capture precise external information. The laser scanner was moved vertically by the lift to collect three-dimensional distance information around the robots. In the experiments by using a laser scanner and a color camera, each tomato fruit in a same cluster was discriminates successfully. Furthermore, the sensing system detected not only objects but also human motion around a robot when infrared sensors were added to the sensing system.

Three Dimensional Sensing System Using Laser Scanner

A three-dimensional sensing system that consisted of a laser scanner and a lift was developed for agricultural robot to capture precise external information. The laser scanner was moved vertically by the lift to collect three-dimensional distance information around the robots. In the experiments by using a laser scanner and a color camera, each tomato fruit in a same cluster was discriminates successfully. Furthermore, the sensing system detected not only objects but also human motion around a robot when infrared sensors were added to the sensing system.

An illumination system for machine vision inspection of agricultural products

An effect of PL filter on imaging that eliminates halation on object surface is well known. However, it has not been easy to use the filter in front of halogen, incandescent, or HID lamps which radiate a lot of heat, because PL film is melted with a temperature of about 60 degree centigrade. Although fluorescence lamps or LEDs can be used with PL filters, their intensity and color rendering are inferior to them. Diffusers or domes with reflection plates are often used when halogen lamps are used, but unavoidable halation and surroundings reflection occur on glossy surface. In this presentation, a direct lighting device (called DL) developed for fruit grading systems is introduced. DL mainly consisted of a PL filter, two heat absorption filters, a halogen lamp, and a fan. Since the absorption wavelength bands of the two filters were different, major heat did not reach the PL filter. In addition, cold air was introduced to the PL filter by its fan. Most parts of plants have cuticular layers on their surfaces to keep moisture within themselves. In this study, three categories are created for objects corresponding to degree of gloss on surfaces and surface materials: category 1 (apples, tomato, eggplants, bell peppers), category 2 (pear, kiwi, peach), and category 3 (potatoes, radish). A color CCD camera was set at the top of object with four DLs and images were acquired. To compare the PL filtering images, a dome and diffusers were also used for the image acquisition. From experiments through three types of illumination devices, it was observed that PL filtering images not only could eliminate halation on products of the category 1 but also could express true colors of the products. Microscopic images showed proportional relation between thickness of cuticular layers and halation on surfaces.

Influence of Environmental Conditions on the Chrysanthemum Leaf Yellow Spot - Measurement of the Leaf Yellow Spot at Early Stage -

Abstract In recent years, yellow spots appear on the leaf of chrysanthemums in many species, which brought commercial problems. The purpose of this study is to examine the measurement of the spot in order to make the influence of environmental conditions clear. Image instrumentation with transmitted light made possible to measure the spot at early stage, which was difficult for reflected light. The method is used the gap of the light quantity between the spot and others. It is involved in chlorophylls and the use of the suitable light color make measuring easy. The portable device using this method was produced experimentally and leaf yellow spot was measured with this device, which brought the basic data, the state get worse with time and the relationship between the spot and environmental conditions.

Study of Efficient Lighting Periods Based on Plant Stoma Reaction

The objective of this study was to detect the plant stoma response under the lighting conditions of continuous and 1 to 15 minutes of lighting. In this study, a real-time measurement system was developed to observe a living plant stoma continuously for a long period in a growth chamber, using a microscope and a color TV camera. A video recording system was adopted to obtain details of stoma movement, and images were captured every 30 seconds. From the experimental results, it was observed that the stoma opened slowly 5 minutes after the lights were turned on, and then opened rapidly until it reached the maximum pore size. In guard cells, light stimulus activates a proton pump, the resulting hyper polarization of the plasma membrane opens voltage-sensitive K+ channels, and then the water entering the guard cells opens the stoma after the K+ ions have entered. This process may cause 5 minutes of delay, and delay was also observed after the light was turned off. 10 minutes of lighting opened the stoma to the maximum size. For better utilization of lighting, it was suggested to turn a light on 10 minutes at 30 minuets before the lighting period to open stomata widely at the beginning of the lighting period, so then plants can start the photosynthesis immediately without any effect of the response of stomata opening. To prove this, carbon dioxide absorptions were measured and as a result 8 % of the photosynthesis benefit was given with these on/off controls.