Color grading apparatus utilizing infrared light source

#This invention is an improvement over the method and apparatus for color grading disclosed in the copending U.S. Pat. No. 3,998,555, issued on Dec. 21, 1976, and entitled: Color Grading Apparatus. As discussed in this copending application, there has been utilized, especially in commercial food processing, apparatus for measuring accurately reflected light in various wavelength regions to determine various properties of products.

#Such apparatus has been especially useful in the controlling of continuous processing machinery such as equipment for blanching or roasting of peanuts, french-fried potatoes, or for peeling potatoes, et cetera. In such controlled processes, the color of the product is detected as it leaves the processing area. The color changes as the degree of processing is altered and the resultant signal responsive to the color is used to control the processing variables. In this manner the process is controlled continuously for the regulation of the heat to gain a desired degree of cooking or for regulating the degree of peeling a product by altering the speed at which the product is fed through the processor, or for regulating other variables in such equipment.

#To eliminate the effects of the reflected light changing in intensity due to such variables as changes in the product volume, distance from the photosensors to the products, et cetera, the reflected light is usually measured in two ranges with the resultant signals compared to generate a ratio signal. By generating such a ratio signal, the variations in the signals resulting from variables not being controlled are canceled out. In the past the light regions measured have usually been centered around 5430 A in the green region and around 6400 A in the red region. By using these wavelength regions, light sources and components are somewhat readily available.

#FIG. 1 is a cross-sectional view of a typical product testing device with the circuit in block diagram form in which the invention can be applied;

#FIG. 2 shows the Argon gas discharge lamp used in the present invention;

#FIG. 3 is a graph of the light intensities and wavelengths emitted by the Argon light source of FIG. 3;

#Apparatus suitable for incorporation of the subject invention is shown in FIG. 1 wherein a sample 10 carried by a conveyor belt 11 is tested for color. In a typical system the conveyor carries a product, usually a food product, from an oven or another form of processing station. It is desired to enable the control of the immediately preceding process by testing the color of the product as it comes out and readjusting the process so that the color of the product falls within a predetermined color range thereby indicating a proper processing procedure has been accomplished.

#The product is tested by exposing it to light of a predetermined frequency range such as that emitted by the light sources 12 and 14 positioned within the housing 15 and directly above an opening 16 in alignment with and directly over the product being tested. The light sources preferably are of a cylindrical configuration with a center opening through which reflected light from the product can pass to the lens system 17 leading into an enclosed lightproof housing 18. The light thereafter strikes a dichroic mirror 19 which passes one predetermined light region and reflects another. The light passing through the dichroic reflector strikes a filter 20 and a photodiode 21. The reflected light passes through a separate filter 22 and strikes a photodiode 24. In this manner the reflected light is detected in two separate light regions of predetermined frequencies. However the filtering of the reflected light must be efficient to make the light intensities a true indication of the color of the product.

#Two light regions are detected which subsequently are compared for the generation of a ratio so as to eliminate variables affecting the reflected light intensities but which have little to do with the color or processing of the product. For instance, if the product quantity on the support or conveyor belt varies, the color of the conveyor belt can show through the lesser quantity product and change the intensity of reflected light in various frequency ranges. In addition, if the product is piled higher in some places than others such that it is closer to the light sources and the lens system 20, the intensity of reflected light also changes. In addition, the overall intensities of the light sources may diminish with use and to some degree the use of two color regions will lessen this effect, however this advantage assumes that the intensities of the two light sources will diminish somewhat equally with time, which is usually true.