田间黄花梨糖度的可见/近红外光谱检测方法

提出了一种可克服背景光对田间光谱测量影响的方法。采集田间水果光谱时，环境背景光的干扰强，难以获取样品有效光谱信息。在田间采用套袋方式遮挡现场光线能得到较理想的结果，但检测效率低，仪器暗场校正和参考光谱校正等方法有利于减小模型误差，但不能有效消除环境光照的干扰。通过在测量探头前加装快门，打开快门时测得样品在仪器光源和背景光共同作用下的现场光谱，关闭快门时测得样品仅在现场环境光线作用下的背景光谱，将背景光谱从现场光谱中扣除进行背景光校正。利用偏最二乘法建立田间(背景光校正前、后)以及室内样品光谱建立黄花梨糖度预测模型，预测值与真实值的相关系数分别为0.1，0.69，0.92，均方根误差分别为0.89。Brix，0.42。Brix，0.27。Brix，预测集的RPD分别为0.79，1.69，2.58，结果表明实验所采用的背景光校正方法可有效减小田间环境光照对黄花梨可见/近红外光谱采集的影响，可用于田间水果的近红外光谱采集，有利于充分发挥可见/近红外光谱技术在果实采收前的田间管理、采收成熟度检测等方面的潜力。

Evaluation of Sugar Content of Huanghua Pear on Trees by Visible/Near Inf rared Spectroscopy

A method of ambient light correction was proposed to evaluate the sugar content of Huanghua pears on tree by visible /near infrared diffuse reflectance spectroscopy (Vis/NIRS). Due to strong interference of ambient light, it was difficult to collect the efficient spectral of pears on tree. In the field, covering the fruits with a bag blocking ambient light can get better results, but the efficiency is fairly low, the instrument corrections of dark and reference spectra may help to reduce the error of the model, however, the interference of the ambient light cannot be eliminated effectively. In order to reduce the effect of ambient light, a shutter was attached to the front of probe. When opening shutter, the spot spectrum were obtained, on which instrument light and ambient light acted at the same time. While closing shutter, background spectra were obtained, on which only ambient light acted，then the ambient light spectra was subtracted from spot spectra. Prediction models were built using data on tree (before and after ambient light correction) and after harvesting by partial least square (PLS). The results of the correlation coefficient(R) are 0.1, 0.69, 0.924; the root mean square error of prediction(SEP) are 0.89。Brix, 0.42。Brix, 0.27。Brix; ratio of standard deviation(SD) to SEP(RPD) are 0.79, 1.69, 2.58, respectively. The results indicate that, method of background correction used in the experimentcan reduce the effect of ambient lighting on spectral acquisition of Huanghua pears in field, efficiently. This method can be used to collect the visible/near infrared spectrum of fruits in field, and may give full play to visible/near-infrared spectroscopy in preharvest management and maturity testing of fruits in the field.