An image display apparatus comprising a rotatable member carrying an array of light emitting devices; a drive for rotating the member, and a control for selectively energizing each of the light emitting devices in a predetermined sequence as the member rotates so as to present a visible image. The image display device is incorporated in a fan cooling unit having a plurality of blades, the rotatable member being one of the blades of the fan cooling unit. The fan cooling unit includes a sensing arrangement responsive to rotation of the blades, for triggering the control for the energization of the light emitting devices in dependence on the speed of rotation of the blades.

A method of creating an image involves providing a plurality of light sources arranged in a one-dimensional matrix. The one-dimensional matrix is made up of a vertical column and at least two horizontal rows in which each of the horizontal rows has no more than one of the light sources. The light sources are blinked at their safe maximum current for at least two image_times that are within the range from about 30 milliseconds to about 200 milliseconds without damaging the light sources or electronic circuity controlling the light sources. Each of the image_times includes two or more display_times that are equal to LED On time. The light sources are moved relative to an observer, such that the observer will observe a two-dimensional image.

A display device is constructed with a support for cyclic or repetitive motion. An array of lights is mounted on the support for sweeping across a region of space during motion of the support. A microcontroller or other microprocessor is coupled to the lights for turning on and off the respective lights of the array. A periodically actuated switch such as an inertial switch is coupled to the microcontroller for measuring the time period or cycle time of a cycle of the cyclic or repetitive motion of the support and for indicating initiation of a cycle. The microcontroller is programmed for synchronizing the turning on and off of respective lights of the array according to the time period or cycle time of a cycle of the cyclic or repetitive motion of the support for forming at least one image across the region of space swept by the array of lights using persistence of vision of a viewer. According to one example the support is a hand held wand for hand held swinging motion back and forth. The array of lights is a column of LED's mounted along the wand for sweeping across a two dimensional area of space. The swinging motion of the wand back and forth can form e.g. alphanumeric characters, words, and sentences for conveying messages. Animated images may also be displayed. Other display devices in other environments with periodic, cyclic, or repetitive motion are also described.

A light emitting device including a plurality of pieces of LEDs D01, D02 to D16, one or more driving circuit(s) for supplying the plurality of LEDs D01, D02 to D16 with electrical power, the number of the driving circuit(s) being less than the number of the LEDs D01, D02 to D16, one or more multiplexer(s) being between the plurality of LEDs D01, D02 to D16 and each of the one or more driving circuit(s), a storage member for storing an image data, and a main control unit for letting the plurality of LEDs emit light by outputting a control signal to each of the multiplexer(s) based on the image data, is provided.

A linear array of red LEDs 10R is provided so as to extend in a direction substantially perpendicular to a direction in which a swing-type display device is swung, and a linear array of green LEDs 10G is further provided, the red LEDs 10R and green LEDs 10G being arranged in pairs of two. A CPU activates each of the red LEDs 10R and green LEDs 10G for a predetermined period to emit light in a luminance level in accordance with image data. As a result, an image corresponding to the image data is displayed in the trajectory of the swing due to persistence of vision. Thus, an image can be displayed in various colors.