A compact C-shaped scanner employs at least two sensors and has a mechanism to standardize or calibrate the sensors. The upper and lower elongated beams of the C-frame include a mid-beam sensor and an outer beam sensor. The scanner can monitor the entire width of a continuous sheet by advancing the scanner back and forth along a scanning distance that is only about half that of the sheet width thereby minimizing the required offsheet distance by an amount approaching half the width of the sheet being monitored. Standardization tiles consisting of references materials that are positioned laterally from the edges of the moving sheet allow for calibration of the sensors which operate either in the transmissive or reflective mode. Selected sheet properties or characteristics of the sheet material can be measured. The two sensors can operate in the transmissive or four sensors can operate in the reflective mode.

The problem solved by the present invention is to provide a pinhole detection device with an improved accuracy of detecting pinholes. The detection unit of the pinhole detection device includes a plurality of optical fibers that transmit light that has passed through the object to be inspected. The plurality of optical fibers are arranged side by side while facing a light source. When a maximum detectable angle at which the pinhole with respect to an optical axis of the light source is detectable is defined as , a maximum angle of incidence of light that can be transmitted by the optical fiber with respect to the optical axis of the light source is set in a range of +0 to +5.