| 摘要 |
PURPOSE:To make it possible to detect the position of an edge part, by attenuating the wavelength of light generated from a steel plate by a filter and passing only the sensitivity region of the image pick-up element of an industrial television and the wavelength of illumination light coinciding with said sensitivity region. CONSTITUTION:A filter 8 attenuating light emitted from a steel plate 4 and permitting only the passage of the wavelength of an illumination light source (halogen lamp) and that of the region coinciding with the element sensitivity of the image pick-up tube of an industrial television 3 is attached to the front surface of the industrial television 3 to avoid the lowering in voltage change in a video signal wave form. When the steel plate 4 is heated in a furnace and a wavelength approaches a visible region from an infrared region, the visible light region of the light from the halogen lamp is passed but the heat radiation light from the surface of the steel plate 4 is perfectly cut and, therefore, the lowering in contrast is suppressed. Therefore, as the contrast of the surface of the steel plate and that of a reflective plate becomes stronger, the value of voltage difference becomes large and the signal proportional to the positional change of an edge part is formed on the basis of the change in voltage and set as a control signal for correcting a position. |
