Abstract: A monitoring target plane is photographed with infrared-rays by each infrared-ray camera. A converter converts format of image data from each infrared-ray camera from analog format into digital format. A control unit, when detecting an abnormal area consisting of pixels having a density value over a fixed value in the image data, calculates an azimuth and an angle of elevation toward the sun from an abnormal location on the monitoring target plane that corresponds to that abnormal area, and judges that a fire occurs if an azimuth toward the abnormal location from the infrared-ray camera photographing the image data including the abnormal area is not coincident with the calculated azimuth toward the sun, or if an angle of depression toward the abnormal location from this infrared-ray camera is not coincident with the calculated angle of elevation toward the sun.

Abstract: Temperature data of each picture element output from a infrared camera looking at a scene to be watched is compared with the same data of a previous frame. Temperature data which has changed from the previous frame is input to a histogram operator having a region defined by the temperature change and quantity of the picture elements. When the quantity of picture elements in the defined region exceeds a threshold level, it is recognized that a certain object having considerable temperature change and size has been detected. Thus, a signal is output to trigger an alarm system, or to sustain circulating frame memories which have recorded the previous scenes so that the scenes of visible light as well as the temperatue patterns for frames before, on, and after the trigger signal can be reproduced as visual images of a display screen.

Abstract: A infrared/visible integrated imaging apparatus having a video signal mixing device for superimposing a visible video signal upon an infrared video signal. The mixing device has a discriminating circuit setting electrical discrimination between an infrared video signal having a level higher than a predetermined black level and having a lower than the predetermined black level. The visible video signal simultaneously output with the infrared video signal having the level higher than a predetermined black level is practically cut off with a visible video signal selecting circuit. The partially cut off video signal is then superimposed on the thermal video signal for display. The level of each of the two video signals is independently controllable.