JP2004317381A - Apparatus for nondestructively measuring sugar content of fruits and vegetables - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small-sized portable apparatus for nondestructively measuring a sugar content of fruits and vegetables without an error using transmitted light from a fruit or vegetable obtained by irradiating the fruit or vegetable with monochromatic light having a specific wavelength. <P>SOLUTION: The apparatus comprises a light source control section 220 which irradiates a measurement point of the fruit or vegetable with light 11, 12 of two different near-infrared wavelength ranges, light detectors 51, 52 which receive transmitted light 12, 22 and 13, 23 generated by the light 11, 12 passing through the measurement point, and detect the amount of transmitted light received at two separate points. Relative transmittance, the ratio between the amount of transmitted light of the same wavelength at the two detection points, is calculated for each wavelength, and using the relative transmittance for each wavelength, the sugar content of the fruit and vegetable is calculated. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００５】
ここで、４つの特定波長にλ_１＝８７０ｎｍ，λ_２＝８７８ｎｍ，λ_３＝８８９ｎｍ，λ_４＝９０６ｎｍを採用することを提案している。ここで、Ｃ：糖濃度，Ａ：吸光度，λ：波長を示す。またｋ_０，ｋ_１，ｋ_２，ｋ_３，ｋ_４は実測糖度を用いて最小２乗法で決定された係数である。
【０００６】
ところで、前記従来の糖度測定装置の場合、検出される反射光は表皮近傍からの反射光がほとんどで、得られる糖濃度も表皮近傍の糖濃度となる。本方式の場合、表皮の薄いリンゴや桃では有効であるが、表皮の厚いミカンやメロンに前記方式を適用した場合、反射光は皮の部分からの成分だけとなり、実の成分情報がほとんど含まれず、実の糖度計測が困難である。
【０００７】
このような問題点に対して、皮の厚い青果物に対して近赤外領域の波長の光で糖濃度計測を実現する透過光を利用した技術が開示されている（例えば特許文献３，４及び非特許文献２参照）。特許文献３及び非特許文献２の技術では、近赤外領域の波長の光を青果物に照射して照射位置とほぼ反対側で透過光を検出し、分光器により得た透過光スペクトルを用いて吸光度及び吸光度の二次微分値を計算し、５つの特定波長の吸光度の二次微分値を用いて下記式により糖度を算出することを提案している。
【０００８】
【数２】

【０００９】
ここで、Ｃ：糖濃度，Ａ：吸光度，λ：波長を示す。またｋｉ（ｉ＝０，１，２，３，４）は、５つの特定波長λ_１＝７４５ｎｍ，λ_２＝７６９ｎｍ，λ_３＝７８６ｎｍ，λ_４＝９１４ｎｍ，λ_５＝８４４ｎｍで、実測糖度を用いて最小２乗法で決定された係数を示す。以上、前記青果物からの透過光を検出することで皮の厚いミカンに対して良好な測定精度を得ている。ところで、数２に表れる吸光度の２階微分値は近似的に下記式で表される。
【００１０】
【数３】

【００１１】
吸光度の２階微分値を算出するには、特定波長（λ_０）前後の波長の吸光度が必要になる。つまり、数２を用いて糖度を算出するには５つの特定波長にその前後の波長を加え１５ヶ以上の波長での吸光度が必要になる。１５ヶ以上の波長を有する前記光源としては、近赤外領域で連続した波長成分を含んだハロゲンランプ等の白色光源が一般的に用いられる。前記白色光源を青果物に照射して得られる透過光から特定波長のスペクトルを得るには回折格子等から構成される複雑な分光器が必要になるため、実用化されている装置のほとんどが大型の据え置きタイプとなっている。
【００１２】
このような問題点に対し、本件出願人は近赤外領域の波長の光を用いた青果物の糖度測定装置において、桃やリンゴなど皮の薄い青果物のみならず皮の厚いミカンやメロン等の青果物の糖濃度が測定でき、しかも従来の糖度測定装置のように回折格子等から構成される複雑な分光器を必要としない青果物の非破壊糖度測定装置を発明し、出願している（特願２００１−３０９１９０号）。
【００１３】
この青果物の非破壊糖度測定装置を図１０に基づいて説明する。波長の異なる２つの照射光１０２，２０２を青果物１に照射するための光源１０，２０と反射プリズム４０，レンズ４１を備え、また照射光１０２，２０２の一部１０１，２０１を検出するためのサンプリングミラー４２，レンズ４３，ＮＤフィルター４５，光検出器４４を備えている。さらに青果物１からの透過光１０３，２０３を検出するためにレンズ５０と光検出器５１を、また信号処理部２３０，中央制御部２００，表示部２１０，光源制御部２２０を備えている。
【００１４】
中央制御部２００は、信号処理部２３０でデジタル化された光検出器４４，５１からの検出信号をもとに、後述する算定式で青果物の糖度を算出し、表示部２１０で表示する。光源制御部２２０は、光源１０，２０に電流を供給するための図示しない電源とスイッチ部を有している。中央制御部２００からの指令信号に従い、光源制御部２２０のスイッチ部により光源１０，２０への電流供給のＯＮ，ＯＦＦ制御が行われる。
【００１５】
以上の構成を有する糖度測定装置の動作を説明する。まず、中央制御部２００からの指令信号に従い、光源制御部２２０から光源１０のみに電流が供給される。光源１０から発した照射光１０２はプリズム４０を透過し、レンズ４１により青果物１に照射される。サンプリングミラー４２により照射光１０２から一部取り出されたモニター光１０１はレンズ４３で光検出器４４の受光面に集められる。一方、青果物１からの透過光１０３はレンズ５０で光検出器５１の受光面に集められる。
【００１６】
光検出器４４，５１から、それぞれモニター光１０１，透過光１０３の光強度に比例した検出信号（電圧）が出力され、信号処理部２３０でデジタル化処理される。デジタル化処理された光検出器４４，５１からの検出電圧Ｖ_４４，Ｖ_５１を基に中央制御部２００で単色光源１０から発した照射光１０２に対する青果物１の透過率Ｔ_１が算出される。
【００１７】
中央制御部２００で行われるの透過率Ｔ_１の算出方法について説明する。モニター光１０１，照射光１０２，透過光１０３の光量をそれぞれＩ_１，Ｉ_２，Ｉ_３とする。単色光源１０から発した照射光１０２に対する青果物１の透過率Ｔ_１は次式で求められる。
Ｔ_１＝Ｉ_３／Ｉ_２＝Ｉ_３／Ｉ_１／ｋ・・・（１．４）
【００１８】
ここで、ｋはサンプリングミラー４２の反射率，ＮＤフィルター４５の透過率によって決まる定数を表す。次に光検出器４４，５１における光量−電圧変換係数をそれぞれβ_４４，β_５１とすると光検出器４４，５１で検出される検出信号（電圧）Ｖ_４４，Ｖ_５１は下記式で表される。
Ｖ_４４＝β_４４＊Ｉ_１・・・（１．５）
Ｖ_５１＝β_５１＊Ｉ_３・・・（１．６）
【００１９】
これらの各式（１．４），（１．５），（１．６）より、青果物１の透過率Ｔ_１は下記式で算出される。
Ｔ_１＝（β_４４／β_５１／ｋ）×Ｖ_５１／Ｖ_４４・・・（１．７）
【００２０】
ここで、（ ）内の値は、糖度測定装置固有の定数で、透過率の値が分かった材料等を用いて簡単に校正することができる。単色光源２０から発する照射光２０２に対する透過率Ｔ_２も前記Ｔ_１同様にして測定することができる。青果物１の糖度は、算出した透過率Ｔ_１，Ｔ_２を用いて下記式で算出する。
Ｃ＝ｋ_０＋ｋ_１＊ｌｎ（Ｔ_１）／ｌｎ（Ｔ_２）・・・（１．８）
【００２１】
ここでｋ_０，ｋ_１は実測糖度を用いて最小２乗法で決定された係数を示す。式（１．８）を用いて糖度推定を行うための最適な波長の組み合わせとして、２つの異なった波長が９５０〜１０１０ｎｍの範囲と１０２０〜１０８０ｎｍの範囲の中からそれぞれ選ばれたものであることを提案している。
【００２２】
以上前記した先願発明によれば、２種類の特定波長の単色光を青果物に照射し、その透過光を検出する。検出された透過光には青果物内部の実の糖度情報が含まれており、みかんやメロンのように皮の厚い青果物の糖度測定が可能となる。また、２種類の特定波長の単色光を用いた本発明の糖度測定装置では、白色光源を用いた従来の糖度測定装置のように透過または反射光スペクトルを検出するための複雑な分光器を必要としない装置が実現でき、また光源に小型の半導体レーザー等を用いることができるため、小型・軽量の糖度測定装置が実現できる。
【００２３】
しかしながら、この先願発明には、前記照射光１０２（２０２）の照射位置Ｐ_０と透過光１０３（２０３）の検出位置Ｐ_１との直線距離ｒが、図１１に示すように果実の大きさ等に依存してわずかに変化する。その変化量δｒ＝ｒ−ｒ’とすると、δｒ＝１ｍｍあたり約４Ｂｒｉｘ％の糖度の測定誤差が生じてしまうという欠点があり、果実の大きさに合わせて直線距離ｒの変化量δｒを調整する機構を設けたとしても、果実の糖度計としての精度を実現するにはδｒを０．２ｍｍ以下にする高精度な調整が必要になる問題があった。
【００２４】
【特許文献１】
特開平２−１４７９４０号公報
【特許文献２】
特開平４−２０８８４２号公報
【特許文献３】
特開平６−１８６１５９号公報
【特許文献４】
特開平６−２１３８０４号公報
【非特許文献１】
園芸学会誌、６１，４４５（１９９２）
【非特許文献２】
園芸学会誌、６２，４６５（１９９３）
【００２５】
【発明が解決しようとする課題】
本発明が解決しようとする課題は、従来のこれらの問題点を解消し、特定波長の単色光を青果物に照射して得られる青果物からの透過光から青果物糖度を非破壊的に誤差なく測定する小型で携帯容易な青果物の糖度測定装置を提供することにある。
【００２６】
【課題を解決するための手段】
かかる課題を解決した本発明の構成は、
１） 青果物の測定部位に複数の異なる波長からなる光を照射する照射手段を設け、同照射手段の光が青果物の測定部位を透過した透過光を異なる距離をおいた２箇所で受光してその透過光量を検出する透過光量検出手段を設け、同透過光量検出手段で検出した２箇所での同波長の透過光量の比である相対透過度を各波長毎に算出し、同各波長の相対透過度を用いて青果物の糖度を算定する演算手段を設けた青果物の非破壊糖度測定装置
２） 照射手段が、２つの異なる波長の光を照射するもので、演算手段が、２箇所で検出した各透過光量のうち透過距離が短い方をＩ_{１ ． λ１}，Ｉ_{１ ． λ２}とし、透過距離が長い方をＩ_{２ ． λ１}，Ｉ_{２ ． λ２}とし、２つの異なる波長の相対透過度Ｒ_λ１，Ｒ_λ２を式Ｒ_λ１＝Ｉ_{２ ． λ１}／Ｉ_{１ ． λ１}，Ｒ_λ２＝Ｉ_{２ ． λ２}／Ｉ_{１ ． λ２}とし、予め実測した糖度と相対透過度Ｒ_λ１，Ｒ_λ２を用いて次式の係数ｋ_０，ｋ_１を求め、糖度Ｃを式Ｃ＝ｋ_０＋ｋ_１＊ｌｎ（Ｒ_λ１）／ｌｎ（Ｒ_λ２）に従って算定するようにしたものである前記１）記載の青果物の非破壊糖度測定装置
３） 照射手段が、２つの異なる波長の光を照射するもので、演算手段が、２箇所で検出した各透過光量のうち透過距離が短い方をＩ_{１ ． λ１}，Ｉ_{１ ． λ２}とし、透過距離が長い方をＩ_{２ ． λ１}，Ｉ_{２ ． λ２}とし、２つの異なる波長の相対透過度Ｒ_λ１，Ｒ_λ２を式Ｒ_λ１＝Ｉ_{２ ． λ１}／Ｉ_{１ ． λ１}，Ｒ_λ２＝Ｉ_{２ ． λ２}／Ｉ_{１ ． λ２}とし、同各相対透過度Ｒ_{λ １}，Ｒ_{λ ２}に基づいて２つの異なる波長の吸光度Ａ_１，Ａ_２を式Ａ_１＝−１ｎ（Ｒ_{λ １}），Ａ_２＝−１ｎ（Ｒ_λ２）とし、予め実測した糖度と吸光度Ａ_１，Ａ_２を用いて次式の係数ｋ_０，ｋ_１を求め、糖度Ｃを式Ｃ＝ｋ_０＋ｋ_１＊Ａ_１／Ａ_２に従って算定するようにしたものである前記１）記載の青果物の非破壊糖度測定装置
４） 照射手段が照射する２つの異なる波長の光が、９４０〜１０００ｎｍの範囲と１０４０〜１０９０ｎｍの範囲の近赤外領域の中から選ばれたものである前記２）又は３）記載の青果物の非破壊糖度測定装置
５） 照射手段が、３つの波長の光を照射するもので、演算手段が、２箇所で検出した各透過光量のうち透過距離が短い方をＩ_{１ ． λ１}，Ｉ_{１ ． λ２}，Ｉ_{１ ． λ３}とし、透過距離が長い方をＩ_{２ ． λ１}，Ｉ_{２ ． λ２}，Ｉ_{２ ． λ３}とし、３つの波長の相対透過度Ｒ_λ１，Ｒ_λ２，Ｒ_λ３を式Ｒ_λ１＝Ｉ_{２ ． λ１}／Ｉ_{１ ． λ１}，Ｒ_λ２＝Ｉ_{２ ． λ２}／Ｉ_{１ ． λ２}，Ｒ_λ３＝Ｉ_{２ ． λ３}／Ｉ_{１ ． λ３}とし、予め実測した糖度と相対透過度Ｒ_λ１，Ｒ_λ２，Ｒ_λ３を用いて次式の係数ｋ_０，ｋ_１を求め、糖度Ｃを式Ｃ＝ｋ_０＋ｋ_１＊ｌｎ（Ｒ_λ１／Ｒ_λ３）／ｌｎ（Ｒ_λ２／Ｒ_λ３）に従って算定するようにしたものである前記１）記載の青果物の非破壊糖度測定装置
６） 照射手段が、３つの波長の光を照射するもので、演算手段が、２箇所で検出した各透過光量のうち透過距離が短い方をＩ_{１ ． λ１}，Ｉ_{１ ． λ２}，Ｉ_{１ ． λ３}とし、透過距離が長い方をＩ_{２ ． λ１}，Ｉ_{２ ． λ２}，Ｉ_{２ ． λ３}とし、３つの波長の相対透過度Ｒ_λ１，Ｒ_λ２，Ｒ_λ３を式Ｒ_λ１＝Ｉ_{２ ． λ１}／Ｉ_{１ ． λ１}，Ｒ_λ２＝Ｉ_{２ ． λ２}／Ｉ_{１ ． λ２}，Ｒ_λ３＝Ｉ_{２ ． λ３}／Ｉ_{１ ． λ３}とし、同各相対透過度Ｒ_{λ １}，Ｒ_{λ ２}，Ｒ_λ３に基づいて３つの異なる波長の吸光度Ａ_１，Ａ_２，Ａ_３を式Ａ_１＝−１ｎ（Ｒ_{λ １}），Ａ_２＝−１ｎ（Ｒ_λ２），Ａ_３＝−１ｎ（Ｒ_λ３）とし、予め実測した糖度と吸光度Ａ_１，Ａ_２，Ａ_３を用いて次式の係数ｋ_０，ｋ_１を求め、糖度Ｃを式Ｃ＝ｋ_０＋ｋ_１＊（Ａ_１−Ａ_３）／（Ａ_２−Ａ_３）に従って算定するようにしたものである前記１）記載の青果物の非破壊糖度測定装置
７） 照射手段が照射する３つの異なる波長の光が、その内２つが９４０〜１０００ｎｍの範囲と１０４０〜１０９０ｎｍの範囲の近赤外領域の中から選ばれたもので、残りの１つが９１０〜９３０ｎｍ又は１０１０〜１０３０ｎｍの範囲の近赤外領域の中から選ばれたものである前記５）又は６）記載の青果物の非破壊糖度測定装置。
にある。
【００２７】
【発明の実施の形態】
本発明において、照射手段で異なる複数の単色光を青果物に照射すると、単色光は青果物内部で散乱・吸収を受けて果外に放射されて透過光となる。この透過光を透過光量検出手段で単色光の照射位置から異なる距離をおいた２箇所で検出する。検出した２つの透過光からその比である相対透過度を計算し、同相対透過度を用いて青果物の糖度を算出する。検出された透過光には青果物内部の実の糖度情報が含まれており、ミカンやメロンのように皮の厚い青果物の糖度測定が可能となる。
【００２８】
また、光源に２ヶの単色光源を用いることで、白色光源を用いた従来の糖度測定装置のように透過または反射光スペクトルを検出するための複雑な分光器を必要としない装置が実現できる。また、果実の大きさに依存して単色光の照射位置と透過光の検出位置との直線距離が変化しても、糖濃度の測定誤差への影響を少なくした青果物の非破壊糖度測定装置が実現できる。
【００２９】
なお、本発明で用いている透過光量Ｉ_{１ ． λ１}，Ｉ_{２ ． λ１}及び相対透過度Ｒ_λ１の各記号は、Ｉ_１，Ｉ_２の数字が検出位置を示し、λ１，λ２，λ３は波長の種類を示しているものである。以下、本発明の各実施例を図面に基づいて基本的に説明する。
【００３０】
【実施例】
実施例１（図１，２参照）：図１に示す実施例１の糖度測定装置は、照射光１１，２１を青果物１に照射するための光源１０，２０と、反射プリズム４０，レンズ４１を備える。また青果物１からの透過光１２，２２を検出するためにレンズ５０と光検出器５１から構成される透過光量検出手段Ｉと、透過光１３，２３を検出するためにレンズ６０と光検出器６１から構成される透過光量検出手段ＩＩを備え、さらに信号処理部２３０，中央制御部２００，表示部２１０，光源制御部２２０を備えている。
【００３１】
中央制御部２００は、信号処理部２３０でデジタル化された光検出器５１，６１からの検出信号をもとに、後述する算定式で青果物の糖度を算出し、表示部２１０で表示する。光源制御部２２０は、光源１０，２０に電流を供給するための図示しない電源、スイッチ部を有している。中央制御部２００からトリガ信号Ｔ_１０（Ｔ_２０）がスイッチ部に入力されると、トリガ信号Ｔ_１０（Ｔ_２０）の立ち上がりに同期してスイッチ部がＯＮとなり、光源１０（光源２０）に電流が供給される。
【００３２】
以上の構成を有する糖度測定装置の動作を説明する。まず、中央制御部２００から送信されるトリガ信号Ｔ_１０がＨｉｇｈとなると、光源制御部２２０の図示しないスイッチ部がトリガ信号Ｔ_１０の立ち上がりに同期してＯＮとなり、光源１０に電流が供給され単色光１１が発生する。一方、トリガ信号Ｔ_２０はＬｏｗのままとなっており、光源２０には電流が供給されず照射光２１は発生していない。
【００３３】
次に、光源１０から発した照射光１１はプリズム４０を透過してレンズ４１により青果物１上に照射され、照射光１１は青果物内部で散乱・吸収を受けて果外のあらゆる方向に放射されて透過光となる。前記照射光１１の照射位置Ｐ_０から直線距離ｒ_１離れた青果物１上の位置Ｐ_１からの透過光１２はレンズ５０で光検出器５１の受光面に集められ、前記照射光１１の照射位置Ｐ_０から直線距離ｒ_２離れた青果物１上の位置Ｐ_２からの透過光１３はレンズ６０で光検出器６１の受光面に集められる。なお、図１ではｒ_１＜ｒ_２とし、光検出器５１，６１にはフォトダイオードを用いている。
【００３４】
光検出器５１，６１からそれぞれ透過光１２，１３の光強度に比例した検出信号が出力され、信号処理部２３０でデジタル化処理される。デジタル化処理された光検出器５１，６１からの検出信号を基に中央制御部２００で後述する算定式で相対透過度Ｒ_λ１が算出される。相対透過度Ｒ_λ１の算出演算が終わると、トリガ信号Ｔ_１０がＬｏｗに、またトリガ信号Ｔ_２０がＨｉｇｈになる。このトリガ信号Ｔ_１０（Ｔ_２０）に基づき、前記光源制御部２２０内の図示しないスイッチ部の開閉により、光源１０がＯＦＦ（消灯）し、光源２０がＯＮ（点灯）する。
【００３５】
続いて、前述した照射光１１による透過相対度Ｒ_λ１の算出手順と同様に、照射光２１による相対透過度Ｒ_λ２の算出が実行される。照射光２１による相対透過度Ｒ_λ２の算出演算が終了するとトリガ信号Ｔ_１０、Ｔ_２０はともにＬｏｗとなり、光源１０，２０はともにＯＦＦ（消灯）して、青果物１の糖度計測作業は終了する。中央制御部２００では算出した相対透過度Ｒ_λ１，Ｒ_λ２から青果物１の糖度を後述する算定式で算出し、その結果を表示部２１０に表示する。
【００３６】
次に、中央制御部２００で行われる相対透過度Ｒ_λ１，Ｒ_λ２の算出方法について説明する。照射光１１，透過光１２，１３の光量をそれぞれＩ_{０ ． λ１}，Ｉ_{１ ． λ１}，Ｉ_{２ ． λ１}とする。照射光１１に対する青果物１の相対透過度Ｒ_λ１は下記式で表される。
Ｒ_λ１＝Ｉ_{２ ． λ１}／Ｉ_{１ ． λ１}・・・（１．９）
【００３７】
光検出器５１，６１における光量−電圧変換係数をそれぞれβ_５１，β_６１とすると、光検出器５１，６１で検出される検出信号（電圧）Ｖ_５１，Ｖ_６１は下記式で表される。
Ｖ_５１＝β_５１＊Ｉ_{１ ． λ１}・・・（１．１０）
Ｖ_６１＝β_６１＊Ｉ_{２ ． λ１}・・・（１．１１）
【００３８】
これら各式（１．９），（１．１０），（１．１１）より、青果物１の相対透過度Ｒ_λ１は下記式で算出され、照射光１１の光量Ｉ_{０ ． λ１}に依存しない形で表される。
Ｒ_λ１＝（β_５１／β_６１）＊Ｖ_６１／Ｖ_５１・・・（１．１２）
【００３９】
ここで、（ ）内の値は、糖度測定装置固有の定数で、光量が分かった光源を用いて簡単に校正することができる。照射光２１に対する青果物１の相対透過度Ｒ_λ２の算出も前記照射光１１に対する青果物１の相対透過度Ｒ_λ１と同様にして求めることができる。青果物１の糖度Ｃは、算出した相対透過度Ｒ_λ１，Ｒ_λ２を用いて下記式で算出する。
Ｃ＝ｋ_０＋ｋ_１＊ｌｎ（Ｒ_λ１）／ｌｎ（Ｒ_λ２）・・・（１．１３）
【００４０】
ここでｋ_０，ｋ_１は実測糖度を用いて最小２乗法で決定された係数を示す。式（１．１３）を用いて糖度推定を行うための異なる２つの波長として、実施例１では９４０〜１０００ｎｍの範囲と１０４０〜１０９０ｎｍの範囲の中からそれぞれ選ばれた波長としている。
【００４１】
また、前記した波長範囲にある照射光１１，２１を発する光源１０，２０としてレーザーを用いることができる。このレーザーに半導体レーザーを用いれば、小型の糖度測定装置が実現できる。また、発光ダイオード等の発光素子を光源１０，２０に用いることも可能である。また近赤外領域の波長の光を連続的に発する白色光源を光源１０，２０に用いる場合、光源１０，２０からの光を前述した波長のみを透過させる光学フィルターを用いることで実現しても良い。さらに、図２に示すように光源１０，２０からの照射光１１，２１を光ファイバー７００を用いて青果物１に照射し、さらに青果物１上の検出点Ｐ_１、Ｐ_２からの透過光１２，１３（２２，２３）を光ファイバー７０１，７０２を用いて前記光検出器５１，６１に導光してもよい。
【００４２】
実施例２（図３参照）：図３に示す実施例２は、３つの波長を用いた青果物の非破壊糖度測定装置の例である。図３に示す実施例２の糖度測定装置は、照射光１１，２１，３１を青果物１に照射するための光源１０，２０，３０と、レンズ４１０，４２０，４３０と、光ファイバー７１０，７２０，７３０及び同各光ファイバー７１０，７２０，７３０を束ねて青果物１に前記照射光１１，２１，３１を照射する光ファイバー７００を備えている。また青果物１からの透過光１２，２２，３２を検出するための光ファイバー７０１，レンズ５０，光検出器５１から構成される透過光量検出手段Ｉと、透過光１３，２３，３３を検出するための光ファイバー７０２，レンズ６０，光検出器６１から構成される透過光量検出手段ＩＩを備え、さらに信号処理部２３０，中央制御部２００，表示部２１０，光源制御部２２０を備えている。
【００４３】
中央制御部２００は、信号処理部２３０でデジタル化された光検出器５１，６１からの検出信号をもとに、後述する算定式で青果物の糖度を算出し、表示部２１０で表示する。光源制御部２２０は、光源１０，２０，３０に電流を供給するための図示しない電源，スイッチ部を有している。中央制御部２００からトリガ信号Ｔ_１０（Ｔ_２０，Ｔ_３０）がスイッチ部に入力されると、トリガ信号Ｔ_１０（Ｔ_２０，Ｔ_３０）の立ち上がりに同期してスイッチ部がＯＮとなり、光源１０（光源２０，光源３０）に電流が供給される。
【００４４】
各照射光１１，２１，３１に対応した青果物１の相対透過度Ｒ_λ１，Ｒ_λ２，Ｒ_λ３は前記実施例１と同様の手順で算出することができる。青果物１の糖度は、算出した相対透過度Ｒ_λ１，Ｒ_λ２，Ｒ_λ３を用いて下記式で算出する。
Ｃ＝ｋ_０＋ｋ_１＊ｌｎ（Ｒ_λ１／Ｒ_λ３）／ｌｎ（Ｒ_λ２／Ｒ_λ３）・・・（１．１４）
【００４５】
ここでｋ_０，ｋ_１は実測糖度を用いて最小２乗法で決定された係数を示す。式（１．１４）を用いて糖度推定を行うための異なる３つの波長として、実施例２では照射光１１，２１が９４０〜１０００ｎｍの範囲と１０４０〜１０９０ｎｍの範囲の中からそれぞれ選ばれたものとし、また残りの照射光３１が９１０〜９３０ｎｍ又は１０１０〜１０３０ｎｍの範囲の中から選ばれた波長としている。
【００４６】
実施例３（図４参照）：実施例１，２では青果物に照射する光を波長の異なる２つ又は３つの単色光に限定して説明した。これにより、白色光源を用いた従来の糖度測定装置のように透過、または反射光スペクトルを検出するための複雑な分光器を必要としない装置が実現できる。また、果実の大きさに依存して単色光の照射位置と透過光の検出位置との直線距離が変化しても、糖濃度の測定誤差への影響を少なくした青果物の非破壊糖度測定装置が実現できる。
【００４７】
一方、従来の白色光源と分光器を用いた青果物の非破壊糖度測定装置においても、果実の大きさに依存して単色光の照射位置と透過光の検出位置との直線距離が変化しても、糖濃度の測定誤差への影響を少なくすることができる。従来の白色光源と分光器を用いた青果物の非破壊糖度測定装置に適用した例を図４を用いて説明する。
【００４８】
図４に示した非破壊糖度測定装置では、近赤外領域の波長の光を含むハロゲンランプ等の白色光源１００とその電源１１０を備え，光源１００からの光１０１をレンズ１２０と光ファイバー７００を介して青果物１に照射する。青果物１に照射された光１０１は果実内部で散乱・吸収を受けて果外のあらゆる方向に放射されて透過光となる。光ファイバー７００による光１０１の青果物１上の照射位置Ｐ_０から直線距離ｒ_１，ｒ_２の青果物１上の位置Ｐ_１，Ｐ_２からの透過光１０２，１０３を光ファイバー７０１，７０２により分光器３００まで導光する。分光器３００はレンズ３２０，３１０と、シャッター３２１，３１１，プリズム３３０，回折格子３４０，多チャンネル検出器３５０から構成される。
【００４９】
多チャンネル検出器３５０にはＣＣＤ等のリニアアレイセンサーが用いられる。位置Ｐ_１から放射された透過光１０２の透過スペクトルを計測する場合、シャッター３１１が開き、多チャンネル検出器３５０上に透過光１０２の透過スペクトルＳ_１が得られる。この場合、シャッター３２１は閉まっている。同様にして位置Ｐ_２から放射された透過光１０３の透過スペクトルＳ_２を測定する場合、シャッター３２１が開き、多チャンネル検出器３５０上に透過光１０３の透過スペクトルＳ_２が得られる。この場合、シャッター３１１は閉まっている。以上の様にして測定した前記透過スペクトルＳ_１，Ｓ_２から透過率スペクトルＴ＝Ｓ_２／Ｓ_１を算出する。得られた透過率スペクトルから式（１．１３），式（１．１４）に従い糖度Ｃを算出することができる。
【００５０】
各実施例の非破壊糖度測定方法について検討した結果を図５〜１１に示す。図５は透明な石英セル容器に入れたグルコース水溶液に種々の波長の単色光を照射し、その透過率スペクトルＴを算出し、その透過率から下記式により算出される吸光度比γと糖濃度の相関についてＳＮ比η＞４となる波長の組み合わせ領域を斜線で示している。
γ＝ｌｎ（Ｔ（λ_１））／ｌｎ（Ｔ（λ_２））・・・（１．１５）
【００５１】
ＳＮ比ηは式（１．１５）で表される吸光度比γと糖濃度の関係を直線回帰した場合の回帰直線の傾きβ，回帰誤差σを用いてη＝（β／σ）^２で定義した。つまり吸光度比γを用いた糖度の推定誤差は（１／η）^０．５で算出され、図７中、η＞４以上となる領域での波長の組み合わせを用いた吸光度比γによる糖濃度の推定誤差は０．５ｗｔ％以下となっている。図７より９４０〜１０００ｎｍの範囲と１０４０〜１０９０ｎｍの範囲を四角で囲んだ領域は前記吸光度比γで糖濃度を推定する為の最適な波長の組み合わせであることがわかる。
【００５２】
上記波長の最適な組み合わせの中から、市販の半導体レーザーで入手できる波長９８０ｎｍ，１０６０ｎｍを選択し、その波長での吸光度比γと水溶液中のグルコース濃度との関係を図６に示す。吸光度γによる測定誤差は０．３ｗｔ％以下を実現している。
【００５３】
一方、果実などの散乱体に対しても、グルコース水溶液で得られた最適な波長の組み合わせがそのまま成り立つ。図７に果実を模した散乱体に対して、吸光度比γと糖濃度の関係について文献「Ａ．Ｉｓｈｉｍａｒｕ：Ｗａｖｅ Ｐｒｏｐａｇａｔｉｏｎ ａｎｄ Ｓｃａｔｔｅｒｉｎｇ ｉｎ Ｒａｎｄｏｍ Ｍｅｄｉａ， Ａｃａｄｅｍｉｃ Ｐｒｅｓｓ， Ｎｅｗ Ｙｏｒｋ（１９７８）」を参考に理論計算した結果を示す。図７の計算では波長として９８０ｎｍ，１０６０ｎｍを選択した。図１で説明した直線距離ｒ_１，ｒ_２をそれぞれ３０ｍｍ，４０ｍｍに設定した。等価散乱係数は糖濃度，波長によらず一定とし、ここでは０．４４ｍｍ^−１とした。また波長，糖濃度に依存した吸収係数はグルコース水溶液を用いて測定した結果を用いた。図７より水溶液と同じ波長の組み合わせにおいて吸光度比γと糖濃度の相関が高いことがわかる。
【００５４】
次に、図２に示した実施例２の非破壊糖度測定装置で実際にリンゴに対して糖度を測定した結果を図８に示す。光源には波長９８０ｎｍ，１０６０ｎｍの市販の半導体レーザーを用いた。測定誤差として０．８Ｂｒｉｘ％以下が得られ、本発明の有効性が立証された。
【００５５】
次に、実施例１，２記載の糖度測定装置において、図１中直線距離ｒ_１を変化させた場合の糖度の測定誤差について解析した結果を図９に示す。図１０に示した従来技術では、直線距離が１ｍｍ変化すると約４ｗｔ％の測定誤差が生じる。非破壊糖度計に要求される精度が１ｗｔ％であることから、直線距離の変化を０．２ｍｍ以下にしなければならない。直線距離の調整機構を設けても高精度な調整機構が必要になる。一方、実施例１の装置では直線距離の変化１ｍｍに対して糖度の測定誤差が１ｗｔ％以下で従来技術の１／４以下となる。さらに実施例２を用いた糖度計では直線距離の変化に対する糖度の測定誤差が従来技術の約１／６０となる。
【００５６】
【発明の効果】
以上説明したように、本発明によれば複数の異なる特定波長の単色光を青果物に照射し、その透過光を前記単色光の照射位置からの直線距離が異なる位置でそれぞれ検出する。検出された透過光には青果物内部の実の糖度情報が含まれており、ミカンやメロンのように皮の厚い青果物の糖度測定が可能となる。また、２〜３種類の特定波長の単色光を用いた本発明の糖度測定装置では、白色光源を用いた従来の糖度測定装置のように透過又は反射光スペクトルを検出するための複雑な分光器を必要としない装置が実現でき、また光源に小型の半導体レーザー等を用いることができるため、小型・軽量の糖度測定装置が実現できる。さらに、果実の大きさに依存して単色光の照射位置と透過光の検出位置との直線距離が変化しても、糖濃度の測定誤差への影響を少なくした青果物の非破壊糖度測定装置が実現できる。
【図面の簡単な説明】
【図１】実施例１の非破壊糖度測定装置の説明図である。
【図２】実施例１の非破壊糖度測定装置の説明図である。
【図３】実施例２の非破壊糖度測定装置の説明図である。
【図４】実施例３の非破壊糖度測定装置の説明図である。
【図５】グルコース水溶液における最適波長の組み合わせ領域を示す図である。
【図６】グルコース水溶液における吸光度比と糖濃度の関係を示す図である。
【図７】果実を模した散乱体での吸光度比と糖濃度の関係を示す図である。
【図８】実施例１の非破壊糖度測定装置でリンゴを測定した結果を示す図である。
【図９】果実の大きさの変化による測定誤差を示す図である。
【図１０】従来技術における青果物の糖度測定装置の説明図である。
【図１１】従来技術における青果物の糖度測定装置の説明図である。
【符号の説明】
１、１’ 青果物
１０，２０，３０ 光源
１１，２１，３１ 照射光
１２，１３ 透過光
２２，２３ 透過光
３２，３３ 透過光
４１，４３ レンズ
５０，６０ レンズ
４０ プリズム
４４，５１，６１ 光検出器
４２ サンプリングミラー
４５ ＮＤフィルター
１００ 白色光源
１１０ 白色光源用電源
１２０ レンズ
２００ 中央制御部
２１０ 表示部
２２０ 光源制御部
２３０ 信号処理部
３００ 分光器
３１０，３２０ レンズ
３１１，３２１ シャッター
３３０ プリズム
３４０ 回折格子
３５０ 多チャンネル検出器
４１０，４２０，４３０ レンズ
７００，７０１，７０２ 光ファイバー
７１０，７２０，７３０ 光ファイバー[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a non-destructive measuring device for the sugar content of fruits and vegetables that measures an index relating to the sweetness of fruits and vegetables, and more specifically, non-destructively measuring the sugar content of fruits and vegetables from transmitted light from fruits and vegetables obtained by irradiating fruits and vegetables with monochromatic light having a specific wavelength. Technology for measuring without
[0002]
[Prior art]
Generally, at the time of shipment of fruits and vegetables such as vegetables and fruits, it is necessary to select a grade by inspection of internal quality such as sugar content in addition to appearance inspection of shape and color. Furthermore, it is desired that the internal quality of the sugar content can be fed back to cultivation management. Conventionally, the sugar content of fruits and vegetables is generally determined by chemical analysis using fruit juice extracted from several samples or by a destructive method using a refractive index refractometer. This destruction method has a long measurement time and cannot measure the sugar content of each fruit or vegetable, and there are problems such as variation in the sugar content within the lot from which the sample was extracted. A method using light having a wavelength in the near infrared region has been researched and developed or put into practical use.
[0003]
Therefore, there is disclosed a technique for irradiating fruits and vegetables with light having a wavelength in the near-infrared region, measuring the absorbance of a specific wavelength by receiving the reflected light, and measuring the sugar content of the fruits and vegetables from the measured value (for example, non-patented). Reference 1 and Patent Documents 1 and 2). In the technique of Non-Patent Document 1, light from a light source including light having a wavelength in the near-infrared region is irradiated on fruits and vegetables, and the spectrum of light diffusely reflected on the pericarp surface and the pericarp layer near the pericarp is constituted by a diffraction grating or the like. We have proposed a method of measuring the sugar content of fruits and vegetables from the diffuse reflectance spectrum using the following spectrometer.
[0004]
[Expression 1]

[0005]
Here, four specific wavelengths λ₁= 870 nm, λ₂= 878 nm, λ₃= 889 nm, λ₄= 906 nm is proposed. Here, C: sugar concentration, A: absorbance, and λ: wavelength. Also k₀, K₁, K₂, K₃, K₄Is a coefficient determined by the least squares method using the measured sugar content.
[0006]
By the way, in the case of the conventional sugar content measuring device, most of the detected reflected light is reflected light from the vicinity of the epidermis, and the obtained sugar concentration is also the sugar concentration near the epidermis. In the case of this method, it is effective for apples and peaches with a thin skin, but when the above method is applied to oranges and melons with a thick skin, the reflected light is only the component from the skin part, and most of the actual component information is included It is difficult to measure the actual sugar content.
[0007]
In order to solve such a problem, techniques using transmitted light for measuring sugar concentration with light having a wavelength in the near-infrared region for fruits and vegetables having a thick skin are disclosed (for example, Patent Documents 3 and 4 and Non-Patent Document 2). In the techniques of Patent Literature 3 and Non-Patent Literature 2, fruits and vegetables are irradiated with light having a wavelength in the near-infrared region, transmitted light is detected at a position substantially opposite to the irradiation position, and a transmitted light spectrum obtained by a spectroscope is used. It has been proposed to calculate the absorbance and the second derivative of the absorbance, and to calculate the sugar content by the following formula using the second derivative of the absorbance at five specific wavelengths.
[0008]
[Expression 2]

[0009]
Here, C: sugar concentration, A: absorbance, and λ: wavelength. Also, ki (i = 0, 1, 2, 3, 4) has five specific wavelengths λ.₁= 745 nm, λ₂= 769 nm, λ₃= 786 nm, λ₄= 914 nm, λ₅= 844 nm, the coefficient determined by the least squares method using the measured sugar content. As described above, by detecting the transmitted light from the fruits and vegetables, good measurement accuracy is obtained for oranges with a thick skin. By the way, the second derivative of the absorbance shown in Expression 2 is approximately expressed by the following equation.
[0010]
[Equation 3]

[0011]
To calculate the second derivative of the absorbance, a specific wavelength (λ₀) Absorbance at the wavelengths before and after is required. That is, in order to calculate the sugar content using Equation 2, the absorbance at 15 or more wavelengths is required by adding the wavelengths before and after the five specific wavelengths. As the light source having 15 or more wavelengths, a white light source such as a halogen lamp containing a continuous wavelength component in the near infrared region is generally used. To obtain a spectrum of a specific wavelength from transmitted light obtained by irradiating the fruits and vegetables with the white light source, a complicated spectroscope composed of a diffraction grating or the like is required, and therefore most of practically used apparatuses are large-sized. It is a stationary type.
[0012]
In order to solve such a problem, the present applicant has developed a sugar content measuring apparatus for fruits and vegetables using light having a wavelength in the near-infrared region, and not only fruits and vegetables having a thin skin such as peaches and apples but also fruits and vegetables such as oranges and melons having a thick skin. Has been invented and applied for a non-destructive sugar content measuring device for fruits and vegetables, which can measure the sugar concentration of fruits and vegetables and does not require a complicated spectroscope composed of a diffraction grating or the like as in the conventional sugar content measuring device (Japanese Patent Application 2001). No. 309190).
[0013]
The nondestructive sugar content measuring device for fruits and vegetables will be described with reference to FIG. Light sources 10 and 20 for irradiating fruits and vegetables 1 with two irradiation lights 102 and 202 having different wavelengths are provided, a reflecting prism 40 and a lens 41, and sampling for detecting parts 101 and 201 of the irradiation lights 102 and 202. A mirror 42, a lens 43, an ND filter 45, and a photodetector 44 are provided. Further, a lens 50 and a photodetector 51 for detecting the transmitted lights 103 and 203 from the fruits and vegetables 1, and a signal processing unit 230, a central control unit 200, a display unit 210, and a light source control unit 220 are provided.
[0014]
The central control unit 200 calculates the sugar content of the fruits and vegetables using a calculation formula described later based on the detection signals from the photodetectors 44 and 51 digitized by the signal processing unit 230, and displays the sugar content on the display unit 210. The light source control unit 220 has a power supply and a switch unit (not shown) for supplying current to the light sources 10 and 20. In accordance with a command signal from the central control unit 200, ON / OFF control of current supply to the light sources 10 and 20 is performed by the switch unit of the light source control unit 220.
[0015]
The operation of the sugar content measuring device having the above configuration will be described. First, in accordance with a command signal from the central control unit 200, current is supplied only from the light source control unit 220 to the light source 10. Irradiation light 102 emitted from the light source 10 passes through the prism 40 and is irradiated on the fruit and vegetable 1 by the lens 41. The monitor light 101 partially extracted from the irradiation light 102 by the sampling mirror 42 is collected on a light receiving surface of a photodetector 44 by a lens 43. On the other hand, the transmitted light 103 from the fruits and vegetables 1 is collected by the lens 50 on the light receiving surface of the photodetector 51.
[0016]
Detection signals (voltages) proportional to the light intensities of the monitor light 101 and the transmitted light 103 are output from the photodetectors 44 and 51, respectively, and digitized by the signal processing unit 230. The detection voltage V from the photodetectors 44 and 51 that have been digitized₄₄, V₅₁The transmittance T of the fruits and vegetables 1 to the irradiation light 102 emitted from the monochromatic light source 10 by the central control unit 200 based on₁Is calculated.
[0017]
The transmittance T performed by the central control unit 200₁The calculation method of will be described. The amounts of the monitor light 101, the irradiation light 102, and the transmitted light 103₁, I₂, I₃And Transmittance T of fruits and vegetables 1 to irradiation light 102 emitted from monochromatic light source 10₁Is obtained by the following equation.
T₁= I₃/ I₂= I₃/ I₁/K...(1.4)
[0018]
Here, k represents a constant determined by the reflectance of the sampling mirror 42 and the transmittance of the ND filter 45. Next, the light amount-voltage conversion coefficients in the photodetectors 44 and 51 are respectively represented by β₄₄, Β₅₁, The detection signal (voltage) V detected by the photodetectors 44 and 51₄₄, V₅₁Is represented by the following equation.
V₄₄= Β₄₄* I₁... (1.5)
V₅₁= Β₅₁* I₃... (1.6)
[0019]
From these equations (1.4), (1.5), and (1.6), the transmittance T of the fruit and vegetable 1 is obtained.₁Is calculated by the following equation.
T₁= (Β₄₄/ Β₅₁/ K) × V₅₁/ V₄₄... (1.7)
[0020]
Here, the values in parentheses are constants specific to the sugar content measuring device, and can be easily calibrated using a material or the like whose transmittance value is known. Transmittance T for irradiation light 202 emitted from monochromatic light source 20₂Also said T₁It can be measured in the same manner. The sugar content of the fruit and vegetable 1 is calculated by the calculated transmittance T₁, T₂Is calculated using the following equation.
C = k₀+ K₁* Ln (T₁) / Ln (T₂) ... (1.8)
[0021]
Where k₀, K₁Indicates a coefficient determined by the least squares method using the measured sugar content. Two different wavelengths are selected from a range of 950 to 1010 nm and a range of 1020 to 1080 nm, respectively, as an optimal combination of wavelengths for estimating the sugar content using equation (1.8). Has been proposed.
[0022]
According to the above-mentioned prior invention, fruits and vegetables are irradiated with two types of monochromatic light having specific wavelengths, and the transmitted light is detected. The detected transmitted light contains the sugar content information of the fruits inside the fruits and vegetables, and the sugar content of fruits and vegetables having a thick skin such as tangerines and melons can be measured. In addition, the sugar content measuring device of the present invention using two types of monochromatic light of a specific wavelength requires a complicated spectroscope for detecting a transmitted or reflected light spectrum like a conventional sugar content measuring device using a white light source. Since a small semiconductor laser or the like can be used as a light source, a small and lightweight sugar content measuring device can be realized.
[0023]
However, this prior invention does not include the irradiation position P of the irradiation light 102 (202).₀And the detection position P of the transmitted light 103 (203)₁11 slightly changes depending on the size of the fruit and the like as shown in FIG. If the change amount δr = rr ′, there is a disadvantage that a measurement error of about 4 Brix% per δr = 1 mm occurs, and the change amount δr of the linear distance r is adjusted according to the size of the fruit. Even if a mechanism is provided, there has been a problem that high-precision adjustment of δr to 0.2 mm or less is required in order to realize the accuracy of a fruit sugar meter.
[0024]
[Patent Document 1]
JP-A-2-147940
[Patent Document 2]
JP-A-4-208842
[Patent Document 3]
JP-A-6-186159
[Patent Document 4]
JP-A-6-213804
[Non-patent document 1]
Journal of Horticultural Society, 61, 445 (1992)
[Non-patent document 2]
Journal of Horticultural Society, 62, 465 (1993)
[0025]
[Problems to be solved by the invention]
The problem to be solved by the present invention is to solve these conventional problems and non-destructively measure the sugar content of fruits and vegetables from transmitted light from fruits and vegetables obtained by irradiating fruits and vegetables with monochromatic light of a specific wavelength. It is an object of the present invention to provide a small and easy-to-carry fruit and vegetable sugar content measuring device.
[0026]
[Means for Solving the Problems]
The configuration of the present invention that has solved such a problem includes:
1) Irradiation means for irradiating light having a plurality of different wavelengths to a measurement site of fruits and vegetables is provided, and the light of the irradiation means receives transmitted light transmitted through the measurement site of fruits and vegetables at two places at different distances. A transmitted light amount detecting means for detecting the transmitted light amount is provided, and a relative transmittance, which is a ratio of a transmitted light amount of the same wavelength at two places detected by the transmitted light amount detecting means, is calculated for each wavelength, and a relative transmittance of each wavelength is calculated. Of non-destructive sugar content of fruits and vegetables provided with calculation means for calculating sugar content of fruits and vegetables using the degree
2) The irradiating means irradiates two different wavelengths of light, and the calculating means determines that the shorter one of the transmitted light amounts detected at two locations has a shorter transmission distance._{1 . λ1}, I_{1 . λ2}And the longer transmission distance is I_{2 . λ1}, I_{2 . λ2}And the relative transmittance R of two different wavelengths_λ1, R_λ2To the formula R_λ1= I_{2 . λ1}/ I_{1 . λ1}, R_λ2= I_{2 . λ2}/ I_{1 . λ2}And the previously measured sugar content and relative permeability R_λ1, R_λ2And the coefficient k of the following equation₀, K₁And the sugar content C is calculated by the formula C = k₀+ K₁* Ln (R_λ1) / Ln (R_λ2The non-destructive sugar content measuring device for fruits and vegetables according to the above 1), which is calculated according to the method described in 1) above.
3) The irradiating means irradiates light of two different wavelengths, and the calculating means determines that the shorter of the transmission distance among the respective transmitted light amounts detected at two locations_{1 . λ1}, I_{1 . λ2}And the longer transmission distance is I_{2 . λ1}, I_{2 . λ2}And the relative transmittance R of two different wavelengths_λ1, R_λ2To the formula R_λ1= I_{2 . λ1}/ I_{1 . λ1}, R_λ2= I_{2 . λ2}/ I_{1 . λ2}And the relative transmittance R_{λ 1}, R_{λ 2}Absorbance A at two different wavelengths based on₁, A₂To the formula A₁= -1n (R_{λ 1}), A₂= -1n (R_λ2) And the previously measured sugar content and absorbance A₁, A₂And the coefficient k of the following equation₀, K₁And the sugar content C is calculated by the formula C = k₀+ K₁* A₁/ A₂The non-destructive sugar content measuring device for fruits and vegetables according to the above 1), wherein the sugar content is calculated according to the following.
4) The fruit or vegetable according to 2) or 3) above, wherein the two different wavelengths of light emitted by the irradiating means are selected from a near infrared region in a range of 940 to 1000 nm and a range of 1040 to 1090 nm. Non-destructive sugar content measuring device
5) The irradiating means irradiates light of three wavelengths, and the calculating means determines that one of the transmitted light amounts detected at two points, which has a shorter transmission distance, is I_{1 . λ1}, I_{1 . λ2}, I_{1 . λ3}And the longer transmission distance is I_{2 . λ1}, I_{2 . λ2}, I_{2 . λ3}And the relative transmittance R of the three wavelengths_λ1, R_λ2, R_λ3To the formula R_λ1= I_{2 . λ1}/ I_{1 . λ1}, R_λ2= I_{2 . λ2}/ I_{1 . λ2}, R_λ3= I_{2 . λ3}/ I_{1 . λ3}And the previously measured sugar content and relative permeability R_λ1, R_λ2, R_λ3And the coefficient k of the following equation₀, K₁And the sugar content C is calculated by the formula C = k₀+ K₁* Ln (R_λ1/ R_λ3) / Ln (R_λ2/ R_λ3The non-destructive sugar content measuring device for fruits and vegetables according to the above 1), which is calculated according to the method described in 1) above.
6) The irradiating means irradiates light of three wavelengths, and the arithmetic means determines that the shorter of the transmission distance among the respective transmitted light amounts detected at two locations is equal to I_{1 . λ1}, I_{1 . λ2}, I_{1 . λ3}And the longer transmission distance is I_{2 . λ1}, I_{2 . λ2}, I_{2 . λ3}And the relative transmittance R of the three wavelengths_λ1, R_λ2, R_λ3To the formula R_λ1= I_{2 . λ1}/ I_{1 . λ1}, R_λ2= I_{2 . λ2}/ I_{1 . λ2}, R_λ3= I_{2 . λ3}/ I_{1 . λ3}And the relative transmittance R_{λ 1}, R_{λ 2}, R_λ3Absorbance A at three different wavelengths based on₁, A₂, A₃To the formula A₁= -1n (R_{λ 1}), A₂= -1n (R_λ2), A₃= -1n (R_λ3) And the previously measured sugar content and absorbance A₁, A₂, A₃And the coefficient k of the following equation₀, K₁And the sugar content C is calculated by the formula C = k₀+ K₁* (A₁-A₃) / (A₂-A₃The non-destructive sugar content measuring device for fruits and vegetables according to the above 1), which is calculated according to the method described in 1) above.
7) The light of three different wavelengths irradiated by the irradiation means, two of which are selected from the near infrared region in the range of 940 to 1000 nm and 1040 to 1090 nm, and the remaining one is 910 to 910 The nondestructive sugar content measuring device for fruits and vegetables according to the above 5) or 6), which is selected from the near infrared region in the range of 930 nm or 1010 to 1030 nm.
It is in.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, when a plurality of different monochromatic lights are irradiated on fruits and vegetables by the irradiating means, the monochromatic lights are scattered and absorbed inside the fruits and vegetables, radiated outside the fruits, and become transmitted light. This transmitted light is detected at two places at different distances from the irradiation position of the monochromatic light by the transmitted light amount detecting means. The relative transmittance, which is the ratio of the two detected transmitted lights, is calculated, and the sugar content of the fruit or vegetable is calculated using the relative transmittance. The detected transmitted light contains the sugar content information of the fruits inside the fruits and vegetables, and the sugar content of fruits and vegetables with a thick skin such as oranges and melons can be measured.
[0028]
Further, by using two monochromatic light sources as the light source, it is possible to realize an apparatus that does not require a complicated spectroscope for detecting a transmitted or reflected light spectrum like a conventional sugar content measuring apparatus using a white light source. In addition, even if the linear distance between the irradiation position of monochromatic light and the detection position of transmitted light changes depending on the size of the fruit, a nondestructive sugar content measuring device for fruits and vegetables that reduces the influence on the measurement error of the sugar concentration is reduced. realizable.
[0029]
The transmitted light amount I used in the present invention_{1 . λ1}, I_{2 . λ1}And relative transmittance R_λ1Each symbol is I₁, I₂Indicate the detection position, and λ1, λ2, λ3 indicate the type of wavelength. Hereinafter, each embodiment of the present invention will be basically described with reference to the drawings.
[0030]
【Example】
Example 1 (see FIGS. 1 and 2): The sugar content measuring device of Example 1 shown in FIG. 1 includes light sources 10 and 20 for irradiating irradiation light 11 and 21 to fruits and vegetables 1, a reflecting prism 40 and a lens 41. Prepare. Further, a transmitted light amount detecting means I composed of a lens 50 and a photodetector 51 for detecting the transmitted lights 12 and 22 from the fruits and vegetables 1, and a lens 60 and a photodetector 61 for detecting the transmitted lights 13 and 23. And a signal processing unit 230, a central control unit 200, a display unit 210, and a light source control unit 220.
[0031]
The central control unit 200 calculates the sugar content of fruits and vegetables using a calculation formula described later based on the detection signals from the photodetectors 51 and 61 digitized by the signal processing unit 230, and displays the sugar content on the display unit 210. The light source control unit 220 has a power supply and a switch unit (not shown) for supplying current to the light sources 10 and 20. Trigger signal T from central control unit 200₁₀(T₂₀) Is input to the switch section, the trigger signal T₁₀(T₂₀The switch unit is turned on in synchronization with the rise of ()), and current is supplied to the light source 10 (light source 20).
[0032]
The operation of the sugar content measuring device having the above configuration will be described. First, the trigger signal T transmitted from the central control unit 200₁₀Becomes High, a switch unit (not shown) of the light source control unit 220 triggers the trigger signal T.₁₀Is turned on in synchronization with the rise of the current, the current is supplied to the light source 10, and the monochromatic light 11 is generated. On the other hand, the trigger signal T₂₀Remains low, no current is supplied to the light source 20, and no irradiation light 21 is generated.
[0033]
Next, the irradiation light 11 emitted from the light source 10 passes through the prism 40 and is irradiated on the fruits and vegetables 1 by the lens 41. The irradiation light 11 is scattered and absorbed inside the fruits and vegetables and radiated in all directions outside the fruits. It becomes transmitted light. The irradiation position P of the irradiation light 11₀Linear distance r from₁Position P on the distant fruits and vegetables 1₁Transmitted light 12 is collected by the lens 50 on the light receiving surface of the photodetector 51, and is irradiated with the irradiation position P of the irradiation light 11.₀Linear distance r from₂Position P on the distant fruits and vegetables 1₂Transmitted light 13 is collected by a lens 60 on a light receiving surface of a photodetector 61. In FIG. 1, r₁<R₂The photodiodes are used for the photodetectors 51 and 61.
[0034]
Detection signals proportional to the light intensities of the transmitted lights 12 and 13 are output from the photodetectors 51 and 61, respectively, and are digitized by the signal processing unit 230. Based on the detection signals from the photodetectors 51 and 61 that have been digitized, the central control unit 200 calculates the relative transmittance R using a calculation formula described later._λ1Is calculated. Relative transmittance R_λ1Is completed, the trigger signal T₁₀Is Low and the trigger signal T₂₀Becomes High. This trigger signal T₁₀(T₂₀), The light source 10 is turned off (turned off) and the light source 20 is turned on (turned on) by opening and closing a switch unit (not shown) in the light source control unit 220.
[0035]
Subsequently, the transmission relative degree R by the irradiation light 11 described above._λ1, The relative transmittance R by the irradiation light 21_λ2Is calculated. Relative transmittance R by irradiation light 21_λ2When the calculation of the calculation is completed, the trigger signal T₁₀, T₂₀Are both Low, the light sources 10 and 20 are both turned off (turned off), and the work of measuring the sugar content of the fruits and vegetables 1 ends. The central control unit 200 calculates the relative transmittance R_λ1, R_λ2, The sugar content of the fruits and vegetables 1 is calculated by a calculation formula described later, and the result is displayed on the display unit 210.
[0036]
Next, the relative transmittance R performed by the central control unit 200_λ1, R_λ2The calculation method of will be described. The light amounts of the irradiation light 11 and the transmitted lights 12 and 13 are respectively represented by I_{0 . λ1}, I_{1 . λ1}, I_{2 . λ1}And Relative transmittance R of fruits and vegetables 1 to irradiation light 11_λ1Is represented by the following equation.
R_λ1= I_{2 . λ1}/ I_{1 . λ1}... (1.9)
[0037]
The light-amount-to-voltage conversion coefficients in the photodetectors 51 and 61 are β₅₁, Β₆₁Then, the detection signal (voltage) V detected by the photodetectors 51 and 61₅₁, V₆₁Is represented by the following equation.
V₅₁= Β₅₁* I_{1 . λ1}... (1.10.)
V₆₁= Β₆₁* I_{2 . λ1}... (1.11)
[0038]
From these equations (1.9), (1.10) and (1.11), the relative transmittance R of the fruit and vegetable 1 is obtained._λ1Is calculated by the following equation, and the light amount I of the irradiation light 11 is_{0 . λ1}Is expressed in a form independent of.
R_λ1= (Β₅₁/ Β₆₁) * V₆₁/ V₅₁... (1.12)
[0039]
Here, the values in parentheses are constants specific to the sugar content measuring device, and can be easily calibrated using a light source whose light quantity is known. Relative transmittance R of fruits and vegetables 1 to irradiation light 21_λ2The relative transmittance R of the fruits and vegetables 1 to the irradiation light 11 is also calculated._λ1Can be obtained in the same manner as The sugar content C of fruit and vegetable 1 is calculated relative permeability R_λ1, R_λ2Is calculated using the following equation.
C = k₀+ K₁* Ln (R_λ1) / Ln (R_λ2) ... (1.13)
[0040]
Where k₀, K₁Indicates a coefficient determined by the least squares method using the measured sugar content. In the first embodiment, two different wavelengths for estimating the sugar content using the formula (1.13) are wavelengths selected respectively from the range of 940 to 1000 nm and the range of 1040 to 1090 nm.
[0041]
In addition, lasers can be used as the light sources 10 and 20 that emit the irradiation light 11 and 21 in the above-described wavelength range. If a semiconductor laser is used as this laser, a small sugar content measuring device can be realized. Further, a light emitting element such as a light emitting diode can be used for the light sources 10 and 20. When a white light source that continuously emits light having a wavelength in the near-infrared region is used as the light sources 10 and 20, it can be realized by using an optical filter that transmits light from the light sources 10 and 20 through only the above-described wavelengths. good. Further, as shown in FIG. 2, the irradiation light 11 and 21 from the light sources 10 and 20 are radiated to the fruit and vegetable 1 using the optical fiber 700, and the detection point P on the fruit and vegetable 1 is further increased.₁, P₂May be guided to the photodetectors 51 and 61 by using optical fibers 701 and 702.
[0042]
Example 2 (see FIG. 3): Example 2 shown in FIG. 3 is an example of a nondestructive sugar content measuring device for fruits and vegetables using three wavelengths. The sugar content measuring device according to the second embodiment shown in FIG. 3 includes light sources 10, 20, 30 for irradiating the irradiation light 11, 21, 31 to the fruits and vegetables 1, lenses 410, 420, 430, and optical fibers 710, 720, 730. And an optical fiber 700 for bundling the optical fibers 710, 720, 730 and irradiating the fruits and vegetables 1 with the irradiation light 11, 21, 31. Also, a transmitted light amount detecting means I composed of an optical fiber 701, a lens 50, and a photodetector 51 for detecting the transmitted light 12, 22, 32 from the fruit and vegetable 1, and a detecting device for detecting the transmitted light 13, 23, 33. A transmission light amount detecting means II including an optical fiber 702, a lens 60, and a photodetector 61 is provided. Further, a signal processing unit 230, a central control unit 200, a display unit 210, and a light source control unit 220 are provided.
[0043]
The central control unit 200 calculates the sugar content of fruits and vegetables using a calculation formula described later based on the detection signals from the photodetectors 51 and 61 digitized by the signal processing unit 230, and displays the sugar content on the display unit 210. The light source control unit 220 has a power supply and a switch unit (not shown) for supplying current to the light sources 10, 20, and 30. Trigger signal T from central control unit 200₁₀(T₂₀, T₃₀) Is input to the switch section, the trigger signal T₁₀(T₂₀, T₃₀) Is turned on in synchronization with the rising edge of ()), and a current is supplied to the light source 10 (the light source 20, the light source 30).
[0044]
Relative transmittance R of fruits and vegetables 1 corresponding to each irradiation light 11, 21, 31_λ1, R_λ2, R_λ3Can be calculated in the same procedure as in the first embodiment. The sugar content of fruit and vegetable 1 is calculated relative permeability R_λ1, R_λ2, R_λ3Is calculated using the following equation.
C = k₀+ K₁* Ln (R_λ1/ R_λ3) / Ln (R_λ2/ R_λ3) ... (1.14)
[0045]
Where k₀, K₁Indicates a coefficient determined by the least squares method using the measured sugar content. In Example 2, the irradiation light 11 and 21 were selected from a range of 940 to 1000 nm and a range of 1040 to 1090 nm as three different wavelengths for performing the sugar content estimation using the formula (1.14). And the remaining irradiation light 31 has a wavelength selected from the range of 910 to 930 nm or 1010 to 1030 nm.
[0046]
Third Embodiment (see FIG. 4): In the first and second embodiments, the light irradiated on fruits and vegetables is limited to two or three monochromatic lights having different wavelengths. This makes it possible to realize a device that does not require a complicated spectroscope for detecting a transmitted or reflected light spectrum, unlike a conventional sugar content measuring device using a white light source. In addition, even if the linear distance between the irradiation position of monochromatic light and the detection position of transmitted light changes depending on the size of the fruit, a nondestructive sugar content measuring device for fruits and vegetables that reduces the influence on the measurement error of the sugar concentration is reduced. realizable.
[0047]
On the other hand, even in a conventional nondestructive sugar content measuring device for fruits and vegetables using a white light source and a spectroscope, even if the linear distance between the irradiation position of monochromatic light and the detection position of transmitted light changes depending on the size of the fruit. In addition, the influence of the sugar concentration on the measurement error can be reduced. An example applied to a conventional non-destructive sugar content measuring device for fruits and vegetables using a white light source and a spectroscope will be described with reference to FIG.
[0048]
The non-destructive sugar content measuring device shown in FIG. 4 includes a white light source 100 such as a halogen lamp including light having a wavelength in the near-infrared region, and a power supply 110. Light 101 from the light source 100 is transmitted through a lens 120 and an optical fiber 700. And irradiate the fruits and vegetables 1. The light 101 applied to the fruits and vegetables 1 is scattered and absorbed inside the fruits and emitted in all directions outside the fruits to become transmitted light. Irradiation position P of light 101 on fruits and vegetables 1 by optical fiber 700₀Linear distance r from₁, R₂Position P on vegetable 1₁, P₂Are transmitted to the spectroscope 300 by the optical fibers 701 and 702. The spectroscope 300 includes lenses 320 and 310, shutters 321 and 311, a prism 330, a diffraction grating 340, and a multi-channel detector 350.
[0049]
As the multi-channel detector 350, a linear array sensor such as a CCD is used. Position P₁When measuring the transmission spectrum of the transmitted light 102 emitted from, the shutter 311 is opened and the transmission spectrum S of the transmitted light 102 is displayed on the multi-channel detector 350.₁Is obtained. In this case, the shutter 321 is closed. Similarly, position P₂Spectrum S of transmitted light 103 emitted from₂Is measured, the shutter 321 is opened, and the transmission spectrum S of the transmitted light 103 is displayed on the multi-channel detector 350.₂Is obtained. In this case, the shutter 311 is closed. The transmission spectrum S measured as described above₁, S₂From the transmittance spectrum T = S₂/ S₁Is calculated. The sugar content C can be calculated from the obtained transmittance spectrum according to the equations (1.13) and (1.14).
[0050]
5 to 11 show the results of the examination of the non-destructive sugar content measurement method in each example. FIG. 5 shows that the glucose aqueous solution placed in a transparent quartz cell container is irradiated with monochromatic light of various wavelengths, its transmittance spectrum T is calculated, and the absorbance ratio γ and the sugar concentration calculated from the transmittance by the following equation are calculated. The shaded area indicates the combination of wavelengths where the SN ratio η> 4 for the correlation.
γ = ln (T (λ₁)) / Ln (T (λ₂)) ... (1.15)
[0051]
The SN ratio η is calculated by using the slope β of the regression line and the regression error σ when the relationship between the absorbance ratio γ and the sugar concentration represented by the formula (1.15) is linearly regressed, and η = (β / σ)²Defined. That is, the estimation error of the sugar content using the absorbance ratio γ is (1 / η)^0.5In FIG. 7, the estimation error of the sugar concentration based on the absorbance ratio γ using the combination of wavelengths in the region where η> 4 or more is 0.5 wt% or less. From FIG. 7, it can be seen that the region surrounded by a square in the range of 940 to 1000 nm and the range of 1040 to 1090 nm is an optimal combination of wavelengths for estimating the sugar concentration based on the absorbance ratio γ.
[0052]
Wavelengths of 980 nm and 1060 nm, which can be obtained with commercially available semiconductor lasers, are selected from the above optimum combinations of wavelengths. FIG. 6 shows the relationship between the absorbance ratio γ at that wavelength and the glucose concentration in the aqueous solution. The measurement error due to the absorbance γ is 0.3 wt% or less.
[0053]
On the other hand, even for a scatterer such as a fruit, the optimum combination of wavelengths obtained with an aqueous glucose solution holds as it is. The theoretical calculation of the relationship between the absorbance ratio γ and the sugar concentration for the scatterer simulating a fruit in FIG. 7 with reference to the document “A. Ishimaru: Wave Propagation and Scattering in Random Media, Academic Press, New York (1978)”. The results obtained are shown. In the calculation of FIG. 7, 980 nm and 1060 nm were selected as the wavelengths. The linear distance r described in FIG.₁, R₂Was set to 30 mm and 40 mm, respectively. The equivalent scattering coefficient is constant regardless of the sugar concentration and wavelength, and is 0.44 mm here.^-1It was. As the absorption coefficient depending on the wavelength and the sugar concentration, a result measured using an aqueous glucose solution was used. FIG. 7 shows that the correlation between the absorbance ratio γ and the sugar concentration is high in the same combination of wavelengths as in the aqueous solution.
[0054]
Next, FIG. 8 shows the results of actually measuring the sugar content of apples using the nondestructive sugar content measuring device of Example 2 shown in FIG. A commercially available semiconductor laser having a wavelength of 980 nm and 1060 nm was used as a light source. A measurement error of 0.8 Brix% or less was obtained, demonstrating the effectiveness of the present invention.
[0055]
Next, in the sugar content measuring devices described in Examples 1 and 2, the linear distance r in FIG.₁FIG. 9 shows the result of analysis on the measurement error of the sugar content when the value was changed. In the prior art shown in FIG. 10, a measurement error of about 4 wt% occurs when the linear distance changes by 1 mm. Since the accuracy required for the non-destructive sugar content meter is 1 wt%, the change in the linear distance must be 0.2 mm or less. Even if a linear distance adjusting mechanism is provided, a high-precision adjusting mechanism is required. On the other hand, in the apparatus of the first embodiment, the measurement error of the sugar content is 1 wt% or less for a change in the linear distance of 1 mm, which is 1/4 or less of the conventional technology. Further, in the saccharimeter using the second embodiment, the measurement error of the saccharimeter with respect to the change of the linear distance is about 1/60 of that of the conventional art.
[0056]
【The invention's effect】
As described above, according to the present invention, fruits and vegetables are irradiated with a plurality of monochromatic lights having different specific wavelengths, and the transmitted light is detected at positions having different linear distances from the irradiation positions of the monochromatic lights. The detected transmitted light contains the sugar content information of the fruits inside the fruits and vegetables, and the sugar content of fruits and vegetables with a thick skin such as oranges and melons can be measured. Further, in the sugar content measuring device of the present invention using two or three types of monochromatic light having a specific wavelength, a complicated spectroscope for detecting a transmitted or reflected light spectrum like a conventional sugar content measuring device using a white light source is used. And a small-sized semiconductor laser or the like can be used as a light source, so that a small and lightweight sugar content measuring device can be realized. Furthermore, even if the linear distance between the irradiation position of monochromatic light and the detection position of transmitted light changes depending on the size of the fruit, a nondestructive sugar content measuring device for fruits and vegetables that reduces the influence on the measurement error of the sugar concentration has been developed. realizable.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a non-destructive sugar content measuring device of Example 1.
FIG. 2 is an explanatory view of a non-destructive sugar content measuring device of Example 1.
FIG. 3 is an explanatory diagram of a non-destructive sugar content measuring device of Example 2.
FIG. 4 is an explanatory view of a nondestructive sugar content measuring device according to a third embodiment.
FIG. 5 is a diagram showing an optimum wavelength combination region in an aqueous glucose solution.
FIG. 6 is a diagram showing the relationship between the absorbance ratio and the sugar concentration in an aqueous glucose solution.
FIG. 7 is a diagram showing the relationship between the absorbance ratio of a scatterer imitating a fruit and the sugar concentration.
FIG. 8 is a diagram showing the results of measuring apples with the nondestructive sugar content measuring device of Example 1.
FIG. 9 is a view showing a measurement error due to a change in fruit size.
FIG. 10 is an explanatory view of a sugar content measuring device for fruits and vegetables in a conventional technique.
FIG. 11 is an explanatory view of an apparatus for measuring sugar content of fruits and vegetables in a conventional technique.
[Explanation of symbols]
1,1 'fruits and vegetables
10,20,30 Light source
11, 21, 31 Irradiation light
12,13 transmitted light
22, 23 transmitted light
32,33 Transmitted light
41, 43 lenses
50, 60 lenses
40 Prism
44,51,61 Photodetector
42 Sampling mirror
45 ND filter
100 white light source
110 White light source power supply
120 lenses
200 Central control unit
210 Display
220 Light source controller
230 signal processing unit
300 spectrometer
310, 320 lens
311,321 Shutter
330 Prism
340 diffraction grating
350 Multi-channel detector
410, 420, 430 lenses
700,701,702 Optical fiber
710, 720, 730 Optical fiber

Claims (7)

Irradiation means for irradiating light of different wavelengths to the measurement site of fruits and vegetables is provided, and the light of the irradiation means receives the transmitted light transmitted through the measurement site of fruits and vegetables at two places at different distances, and the amount of transmitted light Is provided, and the relative transmittance, which is the ratio of the amount of transmitted light of the same wavelength at two locations detected by the transmitted light amount detector, is calculated for each wavelength, and the relative transmittance of each wavelength is calculated. A nondestructive sugar content measuring device for fruits and vegetables, provided with arithmetic means for calculating the sugar content of fruits and vegetables using the same. The irradiating means irradiates light of two different wavelengths, and the calculating means determines which one of the transmitted light amounts detected at two locations has a shorter transmission distance as I _{1 . λ1, I 1. λ2,} and the longer transmission distance I _{2 . λ1, I 2. λ2,} and the relative transmittances R _λ1 and R _λ2 of two different wavelengths are represented by the formula R _λ1 = I _{2 . λ1} / I _{1 . λ1,} R _λ2 = _{I 2. λ2} / I _{1 . λ2} , the coefficients k ₀ and k ₁ of the following equation are obtained using the previously measured sugar content and the relative transmittances R _λ1 and R _λ2 , and the sugar content C is calculated as C = k ₀ + k ₁ * ln (R _λ1 ) / ln ( The nondestructive sugar content measuring apparatus for fruits and vegetables according to claim 1, wherein the apparatus is calculated according to _Rλ2 ). The irradiating means irradiates light of two different wavelengths, and the calculating means determines which one of the transmitted light amounts detected at two locations has a shorter transmission distance as I _{1 . λ1, I 1. λ2,} and the longer transmission distance I _{2 . λ1, I 2. λ2,} and the relative transmittances R _λ1 and R _λ2 of two different wavelengths are represented by the formula R _λ1 = I _{2 . λ1} / I _{1 . λ1,} R _λ2 = _{I 2. λ2} / I _{1 . λ2} , the absorbances A ₁ and A ₂ at two different wavelengths are _calculated based on the relative transmittances R _{λ 1} and R _{λ 2} as A ₁ = -1n (R _{λ 1} ) and A ₂ = -1n (R _{λ 2} ), The coefficients k ₀ and k ₁ of the following equation are obtained using the previously measured sugar content and the absorbances A ₁ and A ₂ , and the sugar content C is calculated according to the formula C = k ₀ + k ₁ * A ₁ / A _2. The non-destructive sugar content measuring device for fruits and vegetables according to claim 1, which is prepared. The non-destructive sugar content of fruits and vegetables according to claim 2 or 3, wherein the two different wavelengths of light irradiated by the irradiation means are selected from a near infrared region in a range of 940 to 1000 nm and a range of 1040 to 1090 nm. measuring device. The irradiating means irradiates light of three wavelengths, and the calculating means determines which one of the transmitted light amounts detected at two places, having a shorter transmission distance, as I _{1 . λ1, I 1. λ2} , I _{1 . λ3,} and the longer transmission distance I _{2 . λ1, I 2. λ2, I 2. λ3,} and the relative transmittances R _λ1 , R _λ2 , R _λ3 of the three wavelengths _{are represented} by the formula R _λ1 = I _{2 . λ1} / I _{1 . λ1,} R _λ2 = _{I 2. λ2} / I _{1 . λ2,} R _λ3 = _{I 2. λ3} / I _{1 . λ3} , the coefficients k ₀ , k ₁ of the following equation _are obtained using the previously measured sugar content and the relative permeability R _λ1 , R _λ2 , R _λ3 , and the sugar content C is calculated by the equation C = k ₀ + k ₁ * ln (R _λ1 / 2. The nondestructive sugar content measuring device for fruits and vegetables according to claim 1, wherein the calculation is performed in accordance with ( _Rλ3 ) / ln ( _Rλ2 / _Rλ3 ). The irradiating means irradiates light of three wavelengths, and the calculating means determines which one of the transmitted light amounts detected at two places, having a shorter transmission distance, as I _{1 . λ1, I 1. λ2} , I _{1 . λ3,} and the longer transmission distance I _{2 . λ1, I 2. λ2, I 2. λ3,} and the relative transmittances R _λ1 , R _λ2 , R _λ3 of the three wavelengths _{are represented} by the formula R _λ1 = I _{2 . λ1} / I _{1 . λ1,} R _λ2 = _{I 2. λ2} / I _{1 . λ2,} R _λ3 = _{I 2. λ3} / I _{1 .} and _{[lambda] 3,} the respective relative transmittance R λ _1, R λ _2, the R _{[lambda] 3} absorbance _A 1 for three different wavelengths on the basis _of, A 2, _{A 3} wherein _{A 1 = -1n (R λ 1} ), A 2 ₌ -1n (R _λ2), and _{a 3 = -1n (R λ3)} , determine the coefficients _k 0, _{k 1} of the following equation using the sugar content and the absorbance _{a 1,} a 2, _{a 3} which measuring beforehand, sugar content C the formula _{C = k 0 + k 1 *} (a 1 -A 3) / (a 2 -A 3) is obtained so as to calculate in accordance with claim 1 fruits or vegetables nondestructive sugar content measuring apparatus according. The light of three different wavelengths irradiated by the irradiation means, two of which are selected from the near infrared region in the range of 940 to 1000 nm and 1040 to 1090 nm, and the other one is 910 to 930 nm or The nondestructive sugar content measuring device for fruits and vegetables according to claim 5 or 6, which is selected from the near infrared region in the range of 1010 to 1030 nm.

Images