US 3871774 A
Unhulled grains are irradiated with a laser beam and the variation in the quantity of the laser beam transmitting through the grains caused by the scattering and absorption due to the presence of cracks in the grains is detected optically or electrically.
Description (OCR text may contain errors)
United States Patent 1191 Murata Mar. 18, 1975 METHOD AND APPARATUS FOR DETECTING CRACKS IN UNHULLED  References Cited GRAINS UNITED STATES PATENTS  Inventor: Noboru Murata, Tokyo, Japan 1,031,669 7/1912 Twamley 356/201 1731 Assigneez 0K1 Electric Industry Ltd-1 13382331? 111133; 12225222521111111"" .111332/131 Tokyo, Japan 3,721,501 3/1973 Atkinson et al. 356/201  Filed: Aug. 16, 1973 Primary Examiner--Vincent P. McGraw  Appl' 388766 Attorney, Agent, or FirmDike, Bronstein, Roberts,
Cushman and Pfund  Foreign Application Priority Data Sept. 8, 1972 Japan 47-89621 [5 ABSTRACT Sept. 11, 1972 Japan 47-106258[U] Unhuned grains are irradiated with a laser beam and the variation in the quantity of the laser beam trans- U-S. s
through grains aused the cattering  Int. Cl. G0ln 21/22, GOln 21/32 and absorption due to the presence of cracks in the  Field of Search 356/103, 104, 200, 201,
grains is detected optically or electrically.
9 Claims, 6 Drawing Figures PATENYEB HAR 1 8 I975 SHEETIUFZ F/G.2a
BACKGROUND OF THE INVENTION DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiment illustrated in FIG. 1 comprises a This invention relates to a method and apparatus for laser oscillator l, a condenser lens 2 for focusing the detecting the internal condition of grains, and more particularly to a method and apparatus for detecting cracks in the grains of unhulled rice by means of a laser beam.
It is desired to stock over a long period uncleaned grains of rice so as to preserve their taste. As the rice grains contain a large quantity of water it is difficult to 7 separate the rice grains from husks without cracking or breaking the rice grains. For this reason, it is usual to mow rice plants, and after drying with sun light, the unhulled rice grains are thrashed and then the husks are removed. Such a method of natural drying, however, requires a relatively long time and large labour, making it impossible to ship uncleaned rice grains immediately after harvest. Accordingly, it is a recent trend to cut ears only and after forced drying the same the husks are separated. However, it is difficult to dry the rice grains to a suitable degree. If dried too much, cracks are formed in the uncleaned rice grains so that when they are separated from the husks they would be pulverized. To determine the degree of drying, it has been proposed to irradiate the unhulled rice grains with soft X- rays for photographing the cracks. Although this method is reliable to some extent, the cost of installation and operation ofthe apparatus is expensive.
SUMMARY OF THE INVENTION Accordingly, it is an object of this invention to provide a new and improved method and apparatus for readily detecting the cracks in unhulled grains.
According to one aspect of this invention there is provided a method of detecting cracks in unhulled grains comprising the steps of irradiating the grains with a laser beam thereby causing it to be scattered or absorbed by the cracks in the grains and measuring the variation in the quantity of the laser beam after transmitting through the grains.
According to another aspect of this invention, there is provided apparatus for detecting cracks in unhulled grains comprising a source of laser beam, means for projecting said laser beam upon unhulled grains, and means for detecting the variation in the quantity of the laser beam after transmitting through said grains.
The invention is particularly suitable for detecting the cracks in unhulled grains of rice for determining the degree of dryness of the grains.
BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings; FIG. 1 is a diagram to explain the principle of operation of one embodiment of this invention;
FIG. 2 shows a manner of scattering and absorption of a laser beam in a rice grain, in which FIG. 2a shows a case wherein there is no crack and FIG. 2b a case wherein there is a crack in the rice grain;
FIG. 3 is a diagram to explain the principle of operation of another embodiment of this invention;
FIG. 4 shows the output from a photoelectric transducer where there is a crack and FIG. 5 showsv a block diagram of the embodiment shown in FIG. 3.
laser light generated by the laser oscillator into a laser beam at its focus 3. Grains of unhulled rice to be examined 4, 7 and 8 are conveyed through a guide 9 to the focus. The laser beam transmitted through the rice grain is magnified by an objective lens 10 to project an image 11 of the grain on a screen, not shown.
FIGS. 2a and 2b show enlarged longitudinal sectional views of unhulled rice grains, in which 6 shows a un cleaned rice grain which is covered by a husk 4a together with a germ 4b. The laser beam impinging upon the rice grain 6 is scattered and or absorbed in the grain, and if there is a crack 5 in the grain, the scattered and or absorbed lights would be attenuated by the crack 5 so that the lights would not reach the portion 6' of the grain behind the crack. Accordingly, as the unhulled rice grains are conveyedthrough the guide 9 in a direction perpendicular to the laser beam, the portion 6 behind the crack 5 looks dark when the grain occupies a position shown in FIG. 2b, whereas when the grain is situated a little above the position shown in FIG. 2b, that is when the laser beam impinges upon the portion 6', the portion of the grain above the crack 5 looks dark. Such rapid change in the amounts of the scattered and or absorbed laser beam can be readily observed in an image 11 projected by a lens 10 on the screen.
Instead of projecting the image 11 on a screen, a high sensitivity photoelectric transducer such as an photoelectric multiphier may be used to record the change in the scattered and or absorbed laser light on a recording paper. Further, by incorporating such an electric detecting device into a forced drying system it is possible to dry the rice grains to any desired degree.
In the foregoing description it was assumed that the crack 5 extends in the direction of propagation of the laser beam. In the case shown in FIG. 3, the crack 21 extends at an angle with respect to the direction of propagation of a laser beam 20. In this case, the amount of the laser beam transmitting through the rice grain decreases when there is a crack. To detect the variation in the amount of the transmitted laser beam, a photoelectric t 'ansducer 22 is used. As shown in FIG. 4, the output from the photoelectric transducer 22 decreases greatly when there is a crack 21.
FIG. 5 shows a connection diagram of crack detecting apparatus embodying the principle just described. The detecting apparatus comprises a laser oscillator 31, a condenser lens 32 for condensing the laser light into a fine beam 33, a support 34 for supporting a unhulled rice grain 35, a plate formed with a slit 36 and a photoelectric transducer 37 arranged to receive the laser beam 33 after it has transmitted through the grain of the rice 35 and the slit 36. The electrical output from the photoelectric transducer 37 is amplified by an amplifier 38 and is then applied to a comparator 40 which compares the amplified output with an output from a source of reference signal 39 which is set to produce an output equal to the output from the photoelectric transducer 37 when there is no crack in the rice grain. When the output from comparator 40 is large, a lamp 41 is lighted whereas when the output is small a lamp 42 is lighted. Accordingly, when there is no crack in the rice grain the output from comparator 40 is zero thereby lighting lamp 41. On the other hand, if there is a crack, the output from the photoelectric transducer 37 is reduced and the output from comparator 40 is increased thereby energizing lamp 42 or other suitable alarming device.
it is not necessary to continuously operate the detecting apparatus. Actually the detecting apparatus may be operated intermittently at a definite internal for example minutes.
What is claimed is: t
l. A method of detecting cracks in unhulled grains comprising the steps of irradiating the grains with a laser beam thereby causing said laser beam to be scattered and or absorbed by said grains and indicating the variation in the quantity of said laser beam after transmitting through said grains as a function of the portion of a grain not illuminated because of a crack in said grain.
2. The method according to claim 1 wherein a laser light from a laser oscillator is focused into a laser beam by a condenser lens, and said grains are moved across said laser beam at the focus of said lens.
3. The method according to claim 1 wherein said unhulled grains are unhulled rice grains.
4. Apparatus for detecting cracks in unhulled grains comprising a source of laser beam, means for projecting said laser beam upon unhulled grains, and means for detecting the variation in the quantity of said laser beam after transmitting through said grains as a function of the portion of a grain not illuminated because of a crack in said grain.
5. The apparatus according to claim 4 wherein said last mentioned means comprises a lens disposed to receive the laser beam transmitted through said grains for projecting images of said cracks on a screen.
6. The apparatus according to claim 4 wherein said last mentioned means comprises a photoelectric transducer disposed to receive said laser beam transmitted through said grains, and means responsive to the output of said photoelectric transducer.
7. The apparatus according to claim 6 wherein said means responsive to the output of said photoelectric transducer comprises a source of reference signal and a comparator which compares said output with said reference signal which is set to be equal to said output when there is no crack in said grains.
8. The apparatus according to claim 4 wherein said grains are unhulled rice grains.
9. Theapparatus according to claim 4 in which a laser light generated by a laser oscillator is converted into a laser beam by means of a condenser lens, and wherein means is provided to successively convey the unhulled grains across said laser beam at the focus of said condenser lens.