1. Field of the Invention
This invention generally relates to a panel type recording device for use in conference and class rooms, and, in particular, to an electronic blackboard capable of automatically recording information written on a recording surface.
2. Description of the Prior Art
For many years, a writing panel, such as a blackboard, has been used as an aid in conference, teaching, etc. The writing panel may take the form of a blackboard, though the color may be often actually green, in which case chalk is used as a writing utensil to write information on the blackboard. The writing panel also may take the form of a white panel, in which case a marker containing an erasable ink is used as a writing utensil. In either case, desired information can be written on the panel and the information can be erased for making the panel available for writing other information. However, the information written on the writing panel cannot be conveniently stored or recorded on a separate recording medium.
Under the circumstances, there has been developed a so-called electronic blackboard which is a recordable writing panel capable of recording information written on a writing medium. Such a recordable writing panel device is advantageous since it can produce the information written on the writing panel in the form of a hard copy and thus it is not necessary for somebody to rewrite the information on a separate sheet of paper. In such an electronic backboard, use is often made of a Charge Coupled Device (CCD) image sensor for reading the information written on the writing medium so as to convert the visual information into an electrical signal. For the CCD image sensor to function properly in reading the information, the degree of illumination on the surface of the writing medium must be maintained at an appropriate level; otherwise, no useful information can be recorded. The prior art electronic blackboard is believed not to be equipped to insure the fact that the proper condition for reading information written on the writing medium has been set prior to the reading operation by the CCD image sensor. Thus, sometimes, the information is incompletely read, leading to a hard copy having incomplete information.