A light-reflection defect detection apparatus and method for sensing the presence of food products or other articles and detecting defects therein is described using pulsed light-emitting semiconductor devices, such as light-emitting diodes (LEDs). The LEDs emit at least three different wavelengths of light including two of visible light (i.e., red and green light) and one of infrared light. Viewers each including photosensor, such as a photoelectric detector, are employed to sense the light reflected from the article and to produce sensor output signals which are sampled and stored before being transmitted to a digital computer for signal processing. The groups of LEDs are pulsed ON and OFF by a capacitor discharge pulse generator circuit which causes a substantially constant current to flow through the LEDs so that they emit light of uniform intensity. The defect detection apparatus and method is especially useful in detecting defects in elongated food products such as French-fry potato strips.
A device (1) for photoelectrically sensing the color of an object (18) includes a plurality of light emitting diodes (4, 6, 8) emitting light in a narrow range of wavelengths and where the light is transmitted through a corresponding fiber optic bundle (10, 12, 14) with a diameter in proportion to the transmission loss of the bundle and in inverse proportion to the emitted light energy of the corresponding light emitting diode and in proportion to the spectral response of a receiving photodiode (24). A receiving section (22) utilizes a PIN type photodiode (24) with an input section (40) that matches the shape of a receiving optical fiber bundle termination (42) where the photodiode (24) converts the reflected light from the object (18) into electrical signals which are then processed by a microprocessor (28) which also controls the activation of the light emitting diodes (4, 6, 8) and outputs a signal indicative of the color of the object (18).
A method and apparatus for classifying articles according to their color, wherein a first pair of wavelengths is selected on a plurality of light reflection curves in terms of a reflected light wavelength spectrum. An article to be inspected is illuminated with light comprising the first pair of wavelengths and light reflected therefrom is measured to detect light reflection values corresponding to this first pair or wavelengths. A primary signal is produced, which represents a resulting difference between the detected light reflection values, this signal being indicative of the color of the inspected article. At least one secondary wavelength is selected on the reflected light wavelength spectrum, and the inspected article is illuminated with light comprising this secondary wavelength and light reflected therefrom is measured to produce a secondary signal which is further indicative of the color of the inspected article. A computer provides a classification frame comprising a first pattern consisting of a first and second crossing set of lines respectively defined by mathematical analysis, this classification frame defining a plurality of color classes. The computer classifies the inspected article in one of the plurality of color classes defined by the frame whenever the primary and secondary signals comply with a specific condition. The computer rejects the inspected article whenever the primary and secondary signals do not comply with this specific condition.
The invention alters the light emission proportion of each of five LEDs for each of a plurality of accumulation cycles in a main scanning direction, in accordance with light emission conditions that are configured in the lighting condition register, causes the emission spectra of the multicolored illumination that composites the light emitted from the five LEDs to approximate three types of color-matching functions that are represented with CIEXYZ or other standard color space, and thus, use a sensor to convert the light that is illuminated by the five LEDs onto an original, and reflected therefrom, into an electrical signal.
An optical detection device for screening magnetic tape for physical defects. The device has three light emitting diodes in a row perpendicular to the direction of travel of the tape. Two rows of photovoltaic detectors having three and two detectors, respectively, are parallel to the row of diodes. The diodes direct light toward the surface of the tape. If no physical defects are present, the light is reflected at the tape surface to the detectors. If a physical defect is present, the light is scattered by the defect and the amount of light which reaches the detector is reduced.
Method and apparatus for sensing the color of articles wherein a first pair of wavelengths is selected on a plurality of light reflection curves in terms of reflected light wavelength spectrum, these curves being associated with a plurality of articles constituting a sample representative of the color range to be sensed. The first pair of wavelengths delimits a first range of wavelengths corresponding to light reflection values in these curves, the light reflection values in each of the curves being in a substantially linear relationship over said first range of wavelengths. Each article to be inspected is illuminated with light comprising the first pair of wavelengths, and the light reflected therefrom is measured to detect light reflection values corresponding to the first pair of wavelengths. A primary signal is produced which represents a resulting difference between said detected light reflection values, this signal being indicative of the color of the inspected article.
