The objective of the present study was to identify criteria of optical properties from sound grains using visible laser with wavelength of 632.8 nm and power 8 mw. The experiments and measurements for the optical and electrical properties were carried out for a random sample from four grain varieties. Obtained results are summarized as follows:
a) The absorption percentages were higher than reflection percentages, reflections were 18.61, 16.31, 9.61, 7.63, 7.00, and 6.90%. Meanwhile, absorption were 81.39, 83.69, 90.39, 92.38, 93.00, and 93.10% for hollow phase corn, flat phase corn, hollow phase wheat, flat phase wheat, and rice and bean grains, respectively, b) There is variation between reflection and absorption percentages for the same grains which had different two phases such as corn and wheat grain, c) The electrical reflection decreased gradually as follows: 5.88, 5.67, 5.46, 5.06, 3.94, and 3.62 mV for hollow phase corn, flat phase corn, hollow phase wheat, paddy rice, flat phase wheat, and bean grains, respectively according to the reflection intensity of laser, d) The values (high, low, and closed) of the reflection intensity for grains were (198, 119, and 148.9 lux), (189, 105, and 130.5 lux), (90, 55, and 76.9 lux), (86, 40, and 61 lux), (83, 35, and 56 lux), and (66, 46, and 55.2 lux). Meanwhile, the absorption intensities were (681, 602, and 651.1 lux), (695, 611, and 669.5 lux), (745, 710, and 723.1 lux), (760, 714, and 739 lux), (765, 717, and 744 lux), and (754, 734, and 744.8 lux) for hollow phase corn, flat phase corn, hollow phase wheat, paddy rice, flat phase wheat, and bean grains, respectively, e) The criteria of optical properties from sound grains are arranged descending order as follows: The reflections were: Bean (6.90%) >, Flat phase-Wheat (7.0%) >, Hollow phase-Wheat (7.63) >, Rice (9.61%) >, Flat phase-Corn (16.31) >, and Hollow phase-Corn (18.61%). Meanwhile, the absorptions were: Hollow phase-Corn (81.39.61%) >, Flat phase-Corn (83.69%) >, Rice (90.39%) >, Hollow phase-Wheat (92.38%) >, Flat phase-Wheat (93.0%) >, and Bean (93.10%), and f) Sorting and separating different grains can be according to optical properties of laser.