Optics: measuring and testing – For light transmission or absorption – By comparison
Reexamination Certificate
2000-06-01
2001-05-15
Font, Frank G. (Department: 2877)
Optics: measuring and testing
For light transmission or absorption
By comparison
C356S231000, C209S581000, C209S588000, C209S589000
Reexamination Certificate
active
06233051
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus for measuring an internal quality of such an object as the greengrocery (fruits and vegetables) on a non-destructive basis.
2. Related Background Art
An example of the conventional apparatus for measuring the internal quality of the fruits or vegetables on a non-destructive basis was a device disclosed, for example, in Japanese Patent Application Laid-Open No. 6-213804. The conventional apparatus will be described below referring to FIG.
37
and FIG.
38
.
In the apparatus illustrated in
FIG. 37
, light
854
is projected from lamp
853
toward an object to be inspected (inspected object)
852
such as a mandarin, an orange, an apple, or the like mounted on belt conveyor
850
and a spectroscope
858
receives light
856
having been transmitted by and emitted from the inspected object
852
. The spectroscope
858
measures an absorption spectrum of the transmitted light
824
and the internal quality of the inspected object can be determined based on the absorption spectrum.
With this apparatus, variations occurred in measured values as a plurality of inspected objects
852
on the conveyor
850
were measured continuously. This is conceivably caused by change of a base line (which is a value as a reference of measurement) of the measured values of the spectroscope with a lapse of measurement time. This change mainly results from changes of the spectroscope and the apparatus itself and from change in ambient circumstances.
Another device for measuring the internal quality of the fruits or vegetables such as melons or the like on a non-destructive basis was, for example, a device disclosed in Japanese Patent Application Laid-Open No. 6-288903. The conventional device will be described below referring to FIG.
39
.
In this device, near-infrared light is projected from lamps
876
toward the inspected object
874
such as a melon or the like mounted on a shield basket
872
on belt conveyor
870
and the spectroscope
880
receives light having been transmitted by and emitted from the inspected object
874
through optical fiber
878
. The spectroscope
880
measures an absorption spectrum of the transmitted light and the internal quality of the inspected object
880
can be determined based on this absorption spectrum.
With this device, variations occurred in measured values as a plurality of inspected objects
874
each mounted on a plurality of shield baskets
872
were measured continuously. This is conceivably caused by change of the base line (which is a value as a reference or standard of measurement) of the measured values of the spectroscope
880
with a lapse of measurement time. This change mainly results from changes in the spectroscope
880
and in the ambient circumstances.
With the conventional apparatus, however, adjustment (i.e., calibration) of the base line changing with a lapse of measurement time was carried out only at the start of measurement, so that the variations occurred in the measured values with progress of measurement with a lapse of time.
On the other hand, for carrying out the calibration in the middle of the measurement, the conveyor line had to be stopped on every occasion of calibration and the measurement also had to be suspended. Therefore, the measurement time was lengthened for execution of the calibration.
In the apparatus illustrated in
FIG. 38
, light
862
reflected by half mirror
860
is projected toward the inspected object
852
mounted on the belt conveyor
850
and the spectroscope
858
receives light
864
having been reflected by the inspected object
852
and having passed through the half mirror
860
, whereby the internal quality of the inspected object
852
can be determined as in the case of the apparatus of FIG.
37
. In this device the spectroscope
858
and reference reflecting plate
866
for calibration are opposed to each other on either side of the belt conveyor
850
and with the reflected light from this reflecting plate
866
the calibration can be carried out at a position where the inspected object is absent on the conveyor
850
.
The calibration according to this method, however, cannot be applied to the device of
FIG. 37
for measuring the light having been transmitted by the inspected object.
An object of the present invention is, therefore, to provide a device for measuring an internal quality of a fruit or vegetable with light having been transmitted by the inspected object, the device being arranged in such structure that the calibration of the device can be carried out without interruption of the measurement, so as to eliminate the change of the base line, whereby the internal quality of the fruit or vegetable can be measured accurately.
On the other hand, in the measurement of the internal quality by spectral analysis as described above, it is common practice to project the light from the light source such as a halogen lamp or the like toward the fruit or vegetable, divide the transmitted light through the fruit or vegetable into a plurality of channels having different wavelengths, convert the intensity of the transmitted light in each channel to current, measure the current to detect an absorption spectrum of the fruit or vegetable, and determine a sugariness or the like of the fruit or vegetable, based thereon. In such measurement, it is inevitable to suffer fluctuations of the light source lamp, specifically, temporal change and deterioration of spectral characteristics (color temperature), and fluctuations due to environmental change of ambient temperature or the like on one hand and it is also inevitable to experience fluctuations and the like due to temporal change or environmental change of the measurement system on the other hand, which results in causing errors in the measurement.
In order to avoid it, in the case of such measurement, the calibration of the device is carried out at intervals of a certain time. The calibration is carried out by measuring the quantity of the transmitted light through a predetermined calibration body instead of the fruit or vegetable being an object originally intended to be inspected. A typical calibration method is as follows. In each wavelength channel, a measurement transmittance T is calculated according to the following equation to effect the calibration:
T=I
s
/I
r
where I
r
is the intensity of the transmitted light (more exactly, intensity of current converted therefrom) through the calibration body and I
s
is the intensity of the transmitted light (more exactly, intensity of current converted therefrom) of the fruit or vegetable to be inspected. Namely, a value of transmittance of an inspected object is calibrated by taking a ratio thereof to the transmittance of the calibration body, thereby canceling the change of the transmitted light due to the variations of the light source and the measurement system.
For more accurate measurement, the transmittance is also sometimes computed according to the following equation:
T=
(
I
s
−D
)/(
I
r
−D
)
where D is dark current of the measurement system when the input into the spectroscope is zero.
The calibration body used in such calibration is normally an object with flat absorption characteristics such as an ND filter (neutral density filter) or the like. The reason why the light from the light source is not monitored directly but is monitored through the ND filter on the occasion of the calibration is that the intensity of light needs to be of a light intensity level close to the intensity of the transmitted light through actual inspected bodies in order to make the calibration accurate. It is, therefore, common practice to select the transmittance of the ND filter for calibration so that the quantity of the transmitted light therethrough is within a predetermined range with respect to the quantity of the transmitted light through the actual inspected bodies.
As described above, the calibration is carried out using the calibration body such as the ND filter or the like against th
Aoki Toyohiko
Fujita Akihiko
Hashimoto Hirotsugu
Kimura Mikio
Ota Takeshi
Font Frank G.
Kubovcik & Kubovcik
Lauchman Layla
Mitsui Mining & Smelting Co. Ltd.
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