Abstract: A color measuring apparatus is provided with a radial illumination unit for projecting illumination light to a measurement object at a first illumination angle in a plurality of directions, a unidirectional illumination unit for projecting illumination light to the measurement object at a second illumination angle in a single direction, a unidirectional light receiving unit for receiving a light ray reflected at a first angle .theta.1 from the direction of regular reflection out of illumination light projected from the radial illumination unit and reflected by the measurement object, and a light ray reflected at a second angle .theta.2 from the direction of regular reflection out of illumination light projected from the unidirectional illumination unit and reflected by the measurement object, the second angle .theta.2 being larger than the first angle .theta.1, and a processing unit for calculating a color value at the first angle .theta.1 and a color value at the second angle .theta.

Abstract: An apparatus for measuring a characteristic of an object, the apparatus includes: a light projector which projects light to an object; a photosensor which senses light which has been projected by the light projector and reflected from the object; a calculator which calculates a characteristic of the object based on an output of the photosensor; an angle detector which detects respective angles of the light projector and the photosensor with respect to the object; an adjustment mechanism which adjusts the respective angles of the light projector and the photosensor; and a controller which controls the adjustment mechanism based on a detection result of the angle detector so that the light projector and the photosensor come into their respective desired angles.

Abstract: An optical density detector which comprises a first light source for emitting a first light which belongs to a wavelength region in which the first light is hardly absorbed by a specific material contained in a sample, a second light source for emitting a second light which belongs to a wavelength region in which the second light is absorbed, substantially as compared with the first light, by the specific material, wherein a peak-wavelength of the second light is shifted by change of a temperature and change of an absorption of the specific material caused by the peak-wavelength shift is characteristic of a linear equation with a gentle grade, light receiving device for measuring a quantity of the first and the second lights which are transmitted through the sample, an arithmetic unit for calculating difference of absorbance between the first light and the second light of which both change depending on the density of the specific material, a temperature measuring device for measuring the temperature of the fi