A colorimeter includes an objective for focusing an object image on a first half of a viewing screen. A standard light reference beam is projected onto the second half of the screen. A moving shutter alternately blocks the first half then the second half of the screen. A light detector is responsive to the alternating images on the screen as they pass through color filters. The detector output may provide information of spectral distribution or color deviation of the object, relative to the standard reference. FIELD OF THE INVENTION The invention generally relates to colorimeters, and more particularly to a colorimeter for measuring color and spectrum distribution, based on the formation of an optical image of an object prior to measurement. BRIEF DESCRIPTION OF THE PRIOR ART The "narrow" definition of color flows from the rules set down by the C. I. E. (International Commission for Illumination) for the measurement of color on flat, uniform, opaque surfaces. It prescribes the "illuminants" which may be used (A, B, C, and variations thereof) and the angles for incident and reflected light, the latter being collected by a photosensor. These angles are normally prescribed at 45 deg. and 0 deg. respectively. The "broad" definition of color takes into account the fact that color is a subjective sensation. It therefore associates "color" with light input to a particular area of the retina. Such light may come from illuminated objects or light sources. It is broken down into three "stimuli" X Y Z whose value can be derived by integration from the spectrum distribution of the light. This is also true of light collected from reflecting surfaces as in the "narrow" definition, above. Tristimulus functions are involved in the integration. The "narrow" definition takes in, strictly speaking, only flat, opaque, non-luminous objects or surfaces. There are similar definitions for "transmitted" color of transparent objects illuminated from behind, but these do not widen the scope of the definition very much. Conventional colorimeters are based on the "narrow" definition, which limits the range of objects that can be measured. However, they can be fitted with an "integrating chamber" which corresponds to another, equally narrow, definition of color. These chambers are so designed that light coming from all parts of the object in all directions is sampled and collected on the photosensor. Use of such devices is somewhat impractical and their light efficiency tends to be low. All colorimeters compare the object to be measured, or "sample," with a "standard" which may be a tile placed on the instrument, or a built-in part: it may be white and identical for all measurements or it may be slightly different from the sample (in differential measurements). This comparison may be carried out in various ways. It may be "sequential," in which case the standard is placed on the instrument port first and the instrument is "zeroed" on this, or stores the values in a memory. After this, the sample is read. Other instruments automatically replace the standard with the sample periodically, with frequency high enough that comparison is "continuous" for all intents and purposes. In any case, however, the advantage of instrument comparison as against visual comparison, which is still the most popular method, is that the latter cannot tell us how much difference there is, or of what kind (except in a very elementary sense). BRIEF DESCRIPTION OF THE PRESENT INVENTION The present invention is capable of measuring color and spectrum energy distribution, based on the formation of an optical image of the object, prior to measurement. This permits application to a wide variety of products, including some of which do not lend themselves to color measurement with conventional means, such as irregularly shaped, non-rigid or fragmented foods or agricultural products. The present invention utilizes an image method which can provide quantitative visual comparison, as well as automatic continuous comparison. The above-mentioned objects and advantages of the present invention will be clearly understood when considered in conjunction with the accompanying drawings, in which:
In a color printing method, a color photosensitive material is exposed in the photographing step to object illuminating light, which is recorded thereon as an optical density by photographic treatments. In the printing step, the optical density is detected to determine blue, green and red exposures, which cause the object illuminating light to be reproduced on a color positive photosensitive material so as to have neutal gray or to be colored to a standard color. An object image on the color/photosensitive material is printed on the color positive photosensitive material with the most suitable color reproduction with the same three-color component exposures as those determined in printing the object illuminating light.
One form of evaluation apparatus comprising a plurality of light sources vertically arranged by one side of a carrier line in width direction Y perpendicular to carrying direction X of the carrier line; and a light-receiving section arranged by an opposite side of the carrier line in the width direction Y perpendicular to the carrying direction X of the carrier line. Another form of evaluation apparatus comprising a plurality of light sources capable of irradiating measuring lights of given quantity; means for regulating the quantity of measuring lights from the light sources in accordance with sizes of vegetables and fruits; a light-receiving window of given openness provided in a carrier line, the light-receiving window capable of leading measuring lights having been transmitted through the vegetables and fruits toward a light-receiving section; and means for regulating quantities of transmitted light provided to the light-receiving window, the means for regulating quantities of transmitted light being capable of regulating the openness of the light-receiving window.
A differential imaging colorimeter system and method which utilizes a RGB color camera to provide accurate differential colorimetry which can be employed as a portable, dedicated, offline system. The system utilizes a portable processor such as a laptop computer, a hand-held imaging head comprising a color camera, a lens, a plurality of white LED lights, a base plate defining an imaging region, housed in an opaque cover, wherein the imaging head provides a RGB video image to the portable processor; and a software program loaded on the portable processor for applying a geometric transform on an image obtained with the imaging head to match a stored reference image. The computer calculates differential colorimetry values to compare current images with a stored reference image.
One form of evaluation apparatus comprising a plurality of light sources vertically arranged by one side of a carrier line in width direction Y perpendicular to carrying direction X of the carrier line; and a light-receiving section arranged by an opposite side of the carrier line in the width direction Y perpendicular to the carrying direction X of the carrier line. Another form of evaluation apparatus comprising a plurality of light sources capable of irradiating measuring lights of given quantity; means for regulating the quantity of measuring lights from the light sources in accordance with sizes of vegetables and fruits; a light-receiving window of given openness provided in a carrier line, the light-receiving window capable of leading measuring lights having been transmitted through the vegetables and fruits toward a light-receiving section; and means for regulating quantities of transmitted light provided to the light-receiving window, the means for regulating quantities of transmitted light being capable of regulating the openness of the light-receiving window.
A spectrometer apparatus uses a spectrum resolving sensor containing an opto-electronic monolithic array of photosensitive elements, each preferably sub-millimeter in size and pitch, and a continuous variable optical filter, that is permanently aligned with the array. Polychromatic light passing through the variable filter is spectrally resolved in accordance with the local filter transmission function, and is incident upon the photosensitive elements in the array. The electrical output of each element in the array is thence a function of the local transmission function of the variable filter and the output of all the elements provides the spectral contents of the polychromatic light. High spectral resolving power is obtained by subtraction of the output signal of adjacent elements in the array.
