Abstract:
The refraction type non-destruction measuring apparatus of the present invention has a prism having a predetermined refractive index, projecting means for projecting near infrared light onto an object to be examined through the prism, a contact material filling the space between the object to be examined and the prism and having a refractive index set in conformity with the characteristic of the object to be examined, and light receiving means for receiving the internal reflected light of the light having entered the interior of the object to be examined through the contact material and the prism.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to an apparatus for measuring the degree of sugariness of fruit or vegetables such as apples and peaches. 
     2. Related Background Art 
     As shown in FIG. 6 of the accompanying drawings, the juice of fruit or a vegetable has heretofore been used as an object  50  to be examined, and the object to be examined has been sandwiched between prisms  52  and  54  having the same refractive index. 
     In this apparatus, monochromatic visible light from a light source  56  enters the object  50  to be examined through the prisms  52  and  54 , and the incident light is refracted by the difference between the refractive indices of the object  50  to be examined and the prisms  52 ,  54 . A line sensor  58  for receiving the refracted light is divided into light and dark portions by the presence or absence of the application of emergent light. 
     The direction of emergence of the emergent light differs depending on the refractive index of the object to be examined and therefore, the refractive index of the object to be examined can be found from the boundary position of the refracted light which has arrived at the line sensor  58 , and further, the degree of sugariness of the fruit or a vegetable which is the object to be examined is obtained (by the relational expression of ICUMSA (International Commission on Uniformity Method of Sugar Analysis) (Table 1). 
     
       
         
               
             
               
             
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Relation between Brix and Refractive Index 
               
             
          
           
               
                 1974 ICUMSA 
               
             
          
           
               
                 % 
                 n D   20   
                 % 
                 n D   20   
                 % 
                 n D   20   
                 % 
                 n D   20   
                 % 
                 n D   20   
               
               
                   
               
               
                  0 
                 1.33299 
                 20 
                 1.36384 
                 40 
                 1.39986 
                 60 
                 1.44193 
                 80 
                 1.49071 
               
               
                  1 
                 1.33442 
                 21 
                 1.36551 
                 41 
                 1.40181 
                 61 
                 1.44420 
                 81 
                 1.49333 
               
               
                  2 
                 1.33586 
                 22 
                 1.36720 
                 42 
                 1.40378 
                 62 
                 1.44650 
                 82 
                 1.49597 
               
               
                  3 
                 1.33732 
                 23 
                 1.36889 
                 43 
                 1.40576 
                 63 
                 1.44881 
                 83 
                 1.49862 
               
               
                  4 
                 1.33879 
                 24 
                 1.37060 
                 44 
                 1.40776 
                 64 
                 1.45113 
                 84 
                 1.50129 
               
               
                  5 
                 1.34026 
                 25 
                 1.37233 
                 45 
                 1.40978 
                 65 
                 1.45348 
                 85 
                 1.50398 
               
               
                  6 
                 1.34175 
                 26 
                 1.37406 
                 46 
                 1.41181 
                 66 
                 1.45584 
                 86 
                 1.5067  
               
               
                  7 
                 1.34325 
                 27 
                 1.37582 
                 47 
                 1.41385 
                 67 
                 1.45822 
                 87 
                 1.5094  
               
               
                  8 
                 1.34477 
                 28 
                 1.37758 
                 48 
                 1.41592 
                 68 
                 1.46061 
                 88 
                 1.5121  
               
               
                  9 
                 1.34629 
                 29 
                 1.37936 
                 49 
                 1.41799 
                 69 
                 1.46303 
                 89 
                 1.5149  
               
               
                 10 
                 1.34782 
                 30 
                 1.38115 
                 50 
                 1.42009 
                 70 
                 1.46546 
                 90 
                 1.5177  
               
               
                 11 
                 1.34937 
                 31 
                 1.38296 
                 51 
                 1.42220 
                 71 
                 1.46790 
               
               
                 12 
                 1.35093 
                 32 
                 1.38478 
                 52 
                 1.42432 
                 72 
                 1.47037 
               
               
                 13 
                 1.35250 
                 33 
                 1.38661 
                 53 
                 1.42647 
                 73 
                 1.47285 
               
               
                 14 
                 1.35408 
                 34 
                 1.38846 
                 54 
                 1.42863 
                 74 
                 1.47535 
               
               
                 15 
                 1.35568 
                 35 
                 1.39032 
                 55 
                 1.43080 
                 75 
                 1.47787 
               
               
                 16 
                 1.35729 
                 36 
                 1.39220 
                 56 
                 1.43299 
                 76 
                 1.48040 
               
               
                 17 
                 1.35891 
                 37 
                 1.39409 
                 57 
                 1.43520 
                 77 
                 1.48295 
               
               
                 18 
                 1.36054 
                 38 
                 1.39600 
                 58 
                 1.43743 
                 78 
                 1.48552 
               
               
                 19 
                 1.36218 
                 39 
                 1.39792 
                 59 
                 1.43967 
                 79 
                 1.48811 
               
               
                   
               
             
          
         
       
     
     In this example, monochromatic visible light is applied to an object  50  to be examined which is the juice of fruit or a vegetable through a prism  62 . When the angle of incidence at this time is suitably selected, the incident light is totally reflected by the surface  64  of the object to be examined  50  which is in contact with the prism  62 . A line sensor  58  which receives the totally reflected light is divided into light and dark portions by the presence or absence of the application of the reflected light. The angle at which the total reflection begins differs depending on the refractive index of the object to be examined and, therefore, it is similar to the above-described example of the prior art that the refractive index and the degree of sugariness of the fruit or vegetable which is the object to be examined are obtained from the boundary position of the line sensor  58 . 
     In these apparatuses, however, juice had to be picked with the fruit or vegetable destroyed. Therefore, the fruit or vegetable had to be destroyed and consumed each time measurement was done, and the degree of sugariness of the fruit or vegetable to be sold could not be measured. 
     In contrast with these, an example of the prior art as shown in FIG. 8 of the accompanying drawings is known as a method of measuring an object to be examined without destroying it. 
     In this example, fruit or a vegetable which is not yet destroyed is used as an object  66  to be examined, instead of the object  50  to be examined in FIG.  7 . The principle of measurement is similar to that in the example of FIG.  7 . 
     However, if the contact between the prism  62  and the surface  68  of the object to be examined is insufficient or if air is present near it, total reflection does not take place on the surface  68  of the object to be examined. Also, if the surface of the object to be examined has an inclination angle with respect to the prism  62 , accurate measurement cannot be done due to the influence of this inclination angle. 
     Further, an apparatus using near infrared absorption analysis has been put into practical use as a method of measuring fruit or a vegetable without destroying it, but this apparatus is bulky and expensive, and requires a power source. 
     SUMMARY OF THE INVENTION 
     To solve the above-noted problems, the present invention provides a refraction type non-destruction measuring apparatus having a prism having a predetermined refractive index, projecting means for projecting near infrared light onto an object to be examined through the prism, a contact material filling the space between the object to be examined and the prism and having a refractive index set in conformity with the characteristic of the object to be examined, and light receiving means for receiving the interval reflected light of the light having entered the interior of the object to be examined through the contact material and the prism. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a first embodiment of the present invention. 
     FIG. 2 shows a second embodiment of the present invention. 
     FIG. 3 is a graph showing the relation between an inclination angle and the angle of total reflection. 
     FIG. 4 shows a third embodiment of the present invention. 
     FIGS. 5A and 5B are a top plan view and a cross-sectional view, respectively, showing a fourth embodiment of the present invention. 
     FIG. 6 shows an example of the prior art. 
     FIG. 7 shows an example of the prior art. 
     FIG. 8 shows an example of the prior art. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 shows a first embodiment of the present invention. 
     An object  2  to be examined is in contact with a prism  6  through a contact material  4 . Light projected from a light source  8  is applied to the object  2  to be examined through the prism  6  and the contact material  4 . The reflected light of this light from the surface  10  of the object to be examined emerges through the contact material  4  and the prism  6  and is detected by a line sensor  12 . 
     The object  2  to be examined is fruit or a vegetable such as an apple or a peach. The light projected from the light source  8  onto the object  2  to be examined is near infrared light having good transmittability to fruit or vegetables, and monochromatic light having its center wavelength at 700 to 720 nm or 790 to 810 nm is used as this light. Such projected light is used and therefore, the projected  5  light is not intercepted by the surface  10  of the object to be examined, and can be projected onto the interior of the object  2  to be examined without destroying the object to be examined. 
     The gel of transparent silicon having elasticity is used as the contact material  4 . By using such a contact material, it becomes possible to bring it into contact with the prism  6  without interposing air on the way to the prism even if the surface  10  of the object to be examined is not flat. 
     Also, the refractive indices Np, Nc and Ns of the prism  6 , the contact material  4  and the object  2  to be examined, respectively, are made to have the following relation: 
     
       
         Np&gt;Nc&gt;Ns  (1)  
       
     
     The present invention intends to measure the critical angle when the light projected from the light source  8  onto the object  2  to be examined is totally reflected by the surface  10  of the object to be examined by the line sensor  12 , and to measure the refractive index of the object to be examined and further the degree of sugariness of the fruit or vegetable which is the object to be examined from the critical angle. That is, when expression (1) is established, the light projected from the light source  8  at an angle of incidence a is refracted at an angle β smaller than α, from the relation that Np&gt;Nc. At this time, 
     
       
           Np ·sin α= Nc ·sin β.  
       
     
     (Snell&#39;s law). When this refracted light is incident on the surface  10  of the object to be examined at an angle exceeding a certain critical angle γ due to the relation that Nc&gt;Ns, total reflection takes place. At angles smaller than γ, there coexist the refracted light and reflected light to the interior of the object to be examined. From expression (1), it never happens that total reflection takes place on the boundary surface between the contact material  4  and the prism  6  before total reflection takes place on the surface of the object  2  to be examined beyond the critical angle γ. The light reflected from the object  2  to be examined is refracted again in the boundary between the contact material  4  and the prism  6  and arrives at the line sensor  12 . 
     In the line sensor  12  the difference between light and darkness appears on the portion thereof irradiated with the reflected light by the total reflection from the object  2  to be examined and the portion thereof not irradiated. The critical angle γ on the surface  10  of the object  2  to be examined can be found from the critical value  14  of the light and darkness, the refractive index Np of the prism  6 , the refractive index Nc of the contact material  4  and the angle α. Thereby the refractive index of the object  2  to be examined can be found. The degree of sugariness of the fruit or vegetable which is the object to be examined can be found from the refractive index thereof by the relational expression of ICUMSA (International Commission on Uniformity Method of Sugar Analysis) (Table 1). 
     FIG. 2 shows a second embodiment of the present invention in which the surface of the object to be examined is slightly inclined with respect to the surface of a prism  16 . The inclination angle is δ. In such a case, the boundary value  14  on a line sensor  12  created by light totally reflected on the surface  10  of the object to be examined is fluctuated by the inclination. In the present embodiment, the relations among the constructions and refractive indices of the object to be examined, the contact material and the prism are similar to those in the first embodiment, but the refractive indices of the object to be examined and the contact material are very approximate values (or may be the same value). 
     
       
         Np&gt;Nc≧Ns  
       
     
     At this time, the following relations exist: 
     
       
           Np ·sin α 2   =Nc ·sin β 2    
       
     
       Nc ·sin γ 2   =Ns    
     
       
           Nc ·sin β 3   =Np ·sin α 3    
       
     
     
       
         β 2 =γ 2 +δ 
       
     
     
       
         β 3 =γ 2 −δ 
       
     
     Further, by δ being minute, 
     
       
         cos δ=1  
       
     
     
       
         sin δ=δ.  
       
     
     From the above-mentioned relations,                sin                   α   2       =       Ns     N                 p       -       Nc     N                 p          δ          1   -       (     Ns   Nc     )     3                     (   2   )                                
     and the angle of total relation α 3  depends on the refractive index Nc and the inclination angle δ of the contact material. 
     In the present embodiment, the refractive index Nc of the contact material and the refractive index Ns of the object to be examined are approximate values or the same value and therefore, it is seen from expression (2) that the angle of total reflection α 3  assumes a value having no relation with the inclination angle. This is shown in FIG.  3 . FIG. 3 represents changes in the angle of total reflection α 3  relative to the inclination angle δ when in expression (2), Ns=1.3329 to 1.36384 (0 to 20% Brix) and Nc=1.36384 (20% Brix) and Np=1.7 and Ns=0, 5, 10, 15, 20% Brix. As can be seen from this graph, if the refractive index Nc of the contact material and the refractive index Ns of the object to be examined are the same value, namely, Nc=Ns=1.36384 (20% Brix), the angle of total reflection α 3  assumes a constant value having no relation with the inclination angle δ. It is also seen that the more approximate values Nc and Ns assume, the smaller becomes the influence of the inclination angle upon the angle of total reflection. The other action and effect of the present embodiment are similar to those of the first embodiment. 
     FIG. 4 shows a third embodiment of the present invention. 
     The third embodiment has a light source  18  movable in parallelism to the prism surface  16  of the prism  6 . The constructions of the prism  6 , the contact material  4 , the object  2  to be examined and the line sensor  12  are similar to those in the first embodiment and the second embodiment. The relations among the refractive indices Np, Nc and Ns of the prism  6 , the contact material  4  and the object  2  to be examined, as in the first embodiment, are 
     
       
         Np&gt;Nc&gt;Ns.  
       
     
     Since the light source  18  is movable in parallelism to the prism surface  16 , the angle of incidence on the prism surface  16  is always constant. 
     The surface  10  of the object  2  to be examined has an inclination with respect to the prism surface  16 , and the boundary value  14  on the line sensor created by the light totally reflected on the surface  10  of the object to be examined is fluctuated by the inclination. However, by the construction of the present embodiment, the light source  18  is moved and projects light, and lights totally reflected by several locations on the surface  10  of the object to be examined which correspond to the movement of the light source  18  are detected as a plurality of boundary values  14  on the line sensor  12 . It is possible to eliminate the influence of the inclination angle  6  by averaging these boundary values. If as in the second embodiment, 
     
       
         Np&gt;Nc≧Ns,  
       
     
     it will be possible to measure the refractive index of the object to be examined more accurately. 
     FIGS. 5A and 5B show a fourth embodiment of the present invention. In this embodiment, three kinds of contact materials  20 ,  22  and  24  are disposed in a rotating mechanism  26 . By the rotation of the rotating mechanism  26 , it is possible to select a contact material to be used and dispose it on the prism  6 . The object  2  to be examined may be placed on the contact material before or after the selection of the contact material. The contact between the prism  6  and the selected contact material and between the contact material and the object  2  to be examined is sufficient owing to the gravity of the object  2  to be examined and the elasticity of the contact material, and it does not happen that air intervenes between the prism  6  and the contact material or between the contact material and the object  2  to be examined. The three kinds of contact materials have different refractive indices. 
     In the present embodiment, the light projected from the light source  8  is applied to the object  2  to be examined through the prism  6  and the selected contact material, and the light reflected by the surface  10  of the object to be examined emerges through the contact material and the prism  6 , and is detected by the line sensor  12 . 
     When the object  2  to be examined is inclined with respect to the prism surface  16 , the boundary value  14  on the line sensor created by the light totally reflected on the surface  10  of the object to be examined is fluctuated by the inclination. In the construction of the present embodiment, however, the contact materials of different refractive indices are usable and therefore, by selecting a contact material having a refractive index most approximate to the refractive index of the object to be examined, it is possible to suppress the influence of the inclination of the object  2  to be examined as shown in FIG.  3 . 
     Any number of contact materials more than two may be adopted, and the greater is the number, the more accurate measurement can be effected. 
     In the first to fourth embodiments, the contact material may be a high refractive index solution such as cane sugar contained in a transparent bag having strength, or a high refractive index solution itself such as cane sugar. 
     Also, the object to be examined may be liquid flowing through a pipe in a factory. In this case, measurement is effected with the space between the window of the pipe and the prism filled with the contact material. Further, the object to be examined may be liquid in a container of glass or the like. In this case, measurement is effected with the space between the surface of the container and the prism filled with the contact material. 
     As described above, according to the present invention, the degree of sugariness of fruit or vegetables can be measured irrespective of the shape of the fruit or vegetables without the fruit or vegetables being destroyed. 
     Further, no power source is necessary and the apparatus can be made compact and portable and is easy and inexpensive to manufacture.