Optical analyzer for agricultural products

• US 4,040,747 A
• Filed: 08/15/1974
• Issued: 08/09/1977
• Est. Priority Date: 08/24/1972
• Status: Expired due to Term

• Current Assignee: NIR Instruments Company
• Original Assignee: Neotec, Inc.
• Inventors: Webster, Donald R.
• Primary Examiner(s): Evans, F. L.
• Application Number:
  US05/497,727
• Time in Patent Office: 1,090 Days
• Field of Search: 356/36, 356/39, 356/51, 356/83, 356/84, 356/96, 356/97, 356/99, 356/100, 356/179, 356/180-186, 356/188, 356/189, 356/195, 356/201, 356/204-206, 356/209-212 , 356/243-246, 350/311, 350/315, 350/318, 235/151.35, 250/226, 250/233
• US Class Current: 356/418
• CPC Class Codes: G01J 2001/182 with SH sample and hold circuits
• CPC Class Codes: G01J 2003/1243 Pivoting IF or other position variation
• CPC Class Codes: G01J 2003/2866 Markers; Calibrating of scan
• CPC Class Codes: G01N 2021/3129 Determining multicomponents by multiwavelength light
• CPC Class Codes: G01N 2021/3159 Special features of multiplexing circuits
• CPC Class Codes: G01N 2021/4769 Fluid samples, e.g. slurries, granulates; Compressible powdery of fibrous samples
• CPC Class Codes: G01N 21/314 with comparison of measurements at specific and non-specific wavelengths dual wavelength spectrometry G01J3/427
• CPC Class Codes: G01N 21/35 using infrared light G01N21/39 takes precedence
• CPC Class Codes: G01N 21/3563 for analysing solids; Preparation of samples therefor
• CPC Class Codes: G01N 21/4738 Diffuse reflection precedence is given to G01N21/55 - G01N21/57 if specular component is taken into consideration, e.g. also for testing fluids, fibrous materials
• CPC Class Codes: G01N 2201/1283 Opaque part
• CPC Class Codes: G01N 33/10 Starch-containing substances, e.g. dough
• CPC Class Codes: Y10S 250/91 Food sample analysis using invisible radiant energy source

Abstract

An automatic test instrument for gaging the percentage of various constituents in organic substances by comparing the reflective optical density of the subject at various wavelengths. Narrow band optical filters are connected together in the form of a rotatable paddle wheel positioned so that the filters can be individually swept through the incident light path between the specimen and wideband light source. As the filter wheel turns, the band of light passed by each filter is progressively shifted with the changing angle of the filter relative to the light path. The filter wheel configuration includes opaque vanes extending from the ends of the filters to periodically interrupt the passage of light to the specimen. Photocells are positioned to sense the level of light reflected from the specimen. The output of the photocells is sampled at pedetermined times relative to the rotation of the filter wheel to yield values indicative of reflected intensity at certain wavelengths. Using these values, an electronic circuit in one embodiment calculates three optical density difference values corresponding to moisture, protein and oil content of the specimen. The difference values are automatically inserted in three linear equations which are solved to obtain readings representing the true percentages of oil, water and protein contained in the specimen. Each time a new specimen is loaded for testing, the instrument is automatically calibrated against a standard sample, preferably Teflon (Trademark). The output of the photocells is amplified in a special circuit which subtracts the level of dark period current from the output when the photocells are illuminated.

Claims

1. Optical measuring apparatus, comprising means for illuminating an object with a plurality of wavelengths of light in a continuous sequence, light sensitive means operatively positioned to produce an output indicative of the level of light received from said object, logic means responsive to said continuous sequence for producing a plurality of outputs indicative of illumination of said object by certain wavelengths of light, logarithmic amplifier means operatively receiving the output of said light sensitive means, a pair of sample and hold circuits operatively connected to receive the output of said logarithmic amplifier means and connected respectively for selective control by said logic means, differential amplifier means operatively connected to receive the outputs of said pair of sample and hold circuits to produce an output indicative of Δ

OD, wherein Δ

OD represents the difference in optical density at a pair of different wavelengths, a plurality of additional sample and hold circuits operatively connected to receive the output of said differential amplifier and respectively connected for selective control by said logic means to store separate outputs indicative of Δ

OD at different pairs of wavelengths, and computer means operatively receiving the outputs of said additional sample and hold circuits for computing the value of mathematical function of the outputs of said additional sample and hold circuits.

2. The apparatus of claim 1, wherein said function is ##EQU1## where K_o and K_i are constants, (Δ

OD)_i represents the respective outputs of said additional sample and hold circuits, and the subscript i identifies individual ones of said additional sample and hold circuits.

3. The apparatus of claim 1, wherein said computer means includes three computing circuits operatively receiving the outputs of said additional sample and hold circuits for respectively computing the values of the following expressions:

space="preserve" listing-type="equation">K.sub.0 + K.sub.1 (Δ

OD).sub.w + K.sub.2 (Δ

OD).sub.o + K.sub.3 (Δ

OD).sub.p ;

space="preserve" listing-type="equation">K.sub.4 + K.sub.5 (Δ

OD).sub.w + K.sub.6 (Δ

OD).sub.o + K.sub.7 (Δ

OD).sub.p ; and

space="preserve" listing-type="equation">K.sub.8 + K.sub.9 (Δ

OD).sub.w + K.sub.10 (Δ

OD).sub.o + K.sub.11 (Δ

OD).sub.p ;

where K₀ to K₁₁ are constants, (Δ

OD)_w, (Δ

OD)_o, and (Δ

OD)_p correspond to the outputs of three of said additional sample and hold circuits, and w, o, and p indicate that the wavelengths at which Δ

OD is measured are relatively sensitive to water, oil and protein, respectively, output means for displaying the values computed by said computing circuits, and output selector means interposed between said output means and said computing circuits for passing individual ones of said computing circuit outputs to said output means.

4. The apparatus of claim 1, further comprising a plurality of calibration units connected respectively between said additional sample and hold circuits and said computer means and movable means for alternatively positioning a standard sample and a test sample in said light path, each said calibration unit including means responsive to the position of said movable means for storing a signal representative of the output of the associated sample and hold circuit when said standard sample is in the light path and for subtracting said value from the output of said sample and hold circuit when the test sample is in said light path.

5. Optical measuring apparatus, comprising means for illuminating an object with a plurality of wavelengths of light in a sequence, light sensitive means positioned to receive light from said object for producing an output indicative of the level of received light, logic means responsive to said sequence for producing a plurality of outputs indicative of illumination of said object by certain wavelengths of light, logarithmic amplifier means operatively receiving the output of said light sensitive means for producing an output indicative of the optical density of said object at said wavelengths, a plurality of sample and hold circuits operatively connected to store the output of said amplifier means at selected times and connected for individual control by said logic means, and computer means connected to receive the stored outputs of said sample and hold means including means for multiplying values of said stored outputs by corresponding selected constant coefficients, means for combining the resulting terms in accordance with a predetermined formula to produce a value indicative of the proportion of a certain constituent in said object, and means for varying said selected coefficients in accordance with selected values represented on insertable cards.

6. The apparatus of claim 5, further comprising a plurality of separately insertable cards each bearing indicia to which said computer varying means is responsive representative of a specific set of said selected constants corresponding to said stored outputs.

7. The apparatus of claim 6, wherein said cards correspond respectively to different biologically organic products.

8. An optical test instrument comprising a housing, illuminating means mounted in said housing defining a light path, a sample holder movable between first and second predetermined positions relative to said housing for loading a test sample and analyzing said test sample respectively, said light path intersecting first and second corresponding areas on said holder at said first and second positions thereof, a standard sample mounted on said holder at said first area, means for positioning said test sample at said second area, said sample holder being movably mounted in said housing such that when said holder is moved to said first position access is provided to said test sample positioning means for replacing said test sample, at least one photosensitive element positioned to receive light from said test sample or said standard sample when positioned in said light path, an electronic circuit for analyzing the output of said photosensitive element to produce a measurement output, an electronic self-calibration unit operatively receiving said measurement output and responsive to the position of said sample holder for modifying said measurement output in accordance with the output of said element when said standard sample is positioned in said light path and said test sample positioning means is in position for loading a new test sample, said self-calibration unit including an amplifier having an input connected to receive said measurement output, electronic means for storing the output of said amplifier and for producing an output signal representing the stored output of said amplifier, switch means connected between the output of said amplifier and said storing means responsive to the position of said sample holder, said switch means interconnecting the output of said amplifier with said storing means when said sample holder is in said first position and disconnecting the output of said amplifier from said storing means when said sample holder is in said second position, the output of said storing means being connected to the input of said amplifier such that the signal representing the output of said amplifier is subtracted from said measurement output.

9. The instrument as recited in claim 8, wherein said standard sample is made of PTFE.

10. An optical test instrument for measuring the level of light reflected from a biological organic test sample comprising a light source for illuminating an area with at least one predetermined bandwidth of light, a standard sample containing a synthetic polymer positionable in said area, said test sample being alternatively positionable in said area, light sensitive means positioned to receive light from said test sample or said standard sample when positioned in said area for producing an electrical output indicative of the level of received light, and calibration means operatively receiving the output of said light sensitive means and responsive to the positioning of said standard sample in said illuminated area for modifying the output of said light sensitive means when said test sample is in said area, said calibration means modifying said output by subtracting the storage level indicative of the output when said standard sample is in said area from the output when said test sample is in said area.

11. An optical test instrument comprising a housing, illuminating means mounted in said housing defining a light path, a sample holder movable between first and second predetermined positions relative to said housing for loading a test sample and analyzing said test sample respectively, said light path intersecting first and second corresponding areas on said holder at said first and second positions thereof, a standard sample mounted on said holder at said first area, means for positioning said test sample at said second area, said sample holder being movably mounted in said housing such that when said holder is moved to said first position access is provided to said test sample positioning means for replacing said test sample, at least one photosensitive element positioned to receive light from said test sample or said standard sample when positioned in said light path, means for storing a calibration value representative of the output of the photosensitive element when said holder is in said first position, and means for subtracting said calibration value from the output of said photosensitive element when said holder is in said second position.

12. The instrument of claim 11 comprising switch means connected between said photosensitive element and said storing means responsive to the position of said sample holder for automatically connecting said photosensitive element to said storage means when said holder is moved to said first position.

13. An optical test instrument comprising a housing, illuminating means mounted in said housing defining a light path, a sample holder movable between first and second predetermined positions relative to said housing, said light path intersecting first and second corresponding areas on said holder at said first and second positions thereof, a standard sample mounted on said holder at said first area, means for positioning a test sample at said second area, at least one photosensitive element positioned to receive light from said test sample or said standard sample when positioned in said light path, an electronic circuit for analyzing the output of said photosensitive element to produce a measurement output voltage, an amplifier connected to amplify said measurement output voltage, and means to generate a signal voltage varying in accordance with the value of said measurement output voltage when said sample holder is in said first position and to apply said signal voltage to the input of said amplifier to algebraically combine with said measurement output to provide at the output of said amplifier an automatic correction to said measurement output when said sample holder is in said second position.