PURPOSE: To convert infrared-rays with a long wavelength into a visible image by providing a multi-element grid receiving infrared-rays from the outside to change its potential and controlling an electron beam emitted by a face-shaped cathode.

CONSTITUTION: An infrared-ray image 7 of a target is formed by an infrared-ray lens 8 on the face of a multi-element grid 4. The multi-element grid 4 is constituted of a thin film thermistor 12 changing its electric resistance according to the temperature of infrared-rays, a thin film fixed resistor 13 and electrodes 14, 15 and 16 connecting them on an insulating film 11 provided on a substrate 19, the bias voltage is applied across the electrode 14 and the electrode 16. These elements are provided in a mosaic shape. The electric resistance of the thin film thermistor 12 is changed in response to the temperature distribution of the infrared-ray image 7 formed on the surface, a potential distribution image corresponding to the infrared-ray image 7 is formed on the multi-element grid 4 face. When A uniform electron beam is fed from a cathode 3, the electron beam passing the electron beam passing hole group of the multi-element grid 4 is modulated and accelerated by an electron lens 5 and hits a fluorescent screen 6 to form a visible image 9.