Electronic blackboard apparatus

Claim 2

An electronic blackboard apparatus, comprising an electonic blackboard unit (1) having a surface plate (4) the surface of which is formed as a writing surface capable of being used repeatedly, position-detecting means (6, 7) for detecting position coordinates of a writing instrument (27) having a core member (31) for displaying video information including characters and figures on said writing surface, and an output section (46, 47) for outputting said video information of said writing surface, characterized in that said writing instrument (27) includes a magnetism generator (30) for applying a magnetic bias to said position-­detecting means when said core member is in contact with said writing surface, there is provided an eraser (35; 107; 116) having an erasing member (37; 109; 118) for erasing said video information including said characters and figures on said writing surface and a magnetism generator (m1, m2) for applying a magnetic bias to said position-detecting means when said erasing member is in contact with said writing surface, said surface plate (4) is made of a non-magnetic material, and said position-detecting means include a position-­detecting tablet (6,7) for detecting the position coordinates of a local magnetic bias applied via said surface plate and a position-detecting control unit (40) for driving said position-detecting tablet and for computing the position coordinates of said writing instrument and said eraser.

Claim 3

An electronic blackboard apparatus according to Claim 1, wherein said position-detecting tablet is comprised of: first magnetostrictive transmission medium elements (8) constituting an assembly of a plurality of magnetostrictive transmission medium elements, each of which is located on the rear side of said surface plate, is arranged in parallel with each other, and constitutes a first array layer (6) substantially parallel with said writing surface on said rear side of said surface plate; second magnetostrictive transmission medium elements (18) having an arrangement equivalent to that of said first magnetostrictive transmission medium elements and constituting a second array layer (7) superposed on said first array layer, each of said second magnetostrictive transmission medium elements being substantially perpendicular to said first magneto­strictive transmission medium elements; Exciting coils (9, 19) constituted by a set of a coil (9) wound around each end of said first magnetostrictive transmission medium elements and adapted to commonly excite said each end and a coil (19) wound around each end of said second magnetostrictive transmission medium elements and adapted to commonly excite said each end; and detection coils (11, 21) constituted by a set of coils (11) respectively wound around each of said first magnetostrictive transmission medium elements over the entire length thereofand adapted to fetch induced voltages based on magnetostrictive vibration waves in said first magnetostrictive transmission medium elements and coils (21) respectively wound around each of said second magnetostrictive transmission medium elements over the entire length thereof and adapted to fetch induced voltages based on magnetostrictive vibration waves in said second magnetostrictive transmission medium elements, and said position-detectingcontrol unit is comprised of: a pulse oscillator (45) for supplying a pulse current to said exciting coils at an appropriate timing; and a computing unit for measuring a time from the time of said excitation until the time of fluctuations in said induced voltages of said detection coils on the basis of said fluctuations at the time when said magneto-vibration waves generated from said each end of said first or second magnetostrictive transmission medium elements reach the position of contact of said writing instrument at the time of said excitation.

Claim 4

An eraser for use with an electronic blackboard in which each position in a writing region is defined by X coordinates and Y coordinates using each one end of said writing region in the X- and Y-derections as reference positions and reaching each other end thereof, a writing position is indicated with the use of a writing instrument (27), and a written image is processed electronically, said eraser (107; 116) comprising: position-indicating means (m1, m2) provided at the vicinity of opposite end portions of the surface of an erasing member (109; 118) contacting a writing surface and adapted to indicate first and second positions; and inclination-discriminating means (110′, 110; 119) for discriminating to which side a straight line connecting said first and second positions is inclined using an X-axis or a Y-axis on said writing surface as a reference line.

Claim 5

An eraser for use with an electronic blackboard in which each position in a writing region is defined by X coordinates and Y coordinates using each one end of said writing region in the X- and Y-derections as reference positions and reaching each other end thereof, a writing position is indicated with the use of a writing instrument (27), and a written image is processed electronically, said eraser (107; 116) comprising: position-indicating means (m1, m2) provided at the vicinity of opposite end portions of the surface of an erasing member (109; 118) contacting a writing surface and adapted to indicate first and second positions; and inclination-discriminating means (110′, 110; 119) for discriminating to which side a straight line connecting said first and second positions is inclined using an X-axis or a Y-axis on said writing surface as a reference line.

Claim 6

An eraser according to claim 3 comprising at least two switches (SW₁ - SW₄) actuated when said erasing member (109; 118) comes into contact with said writing surface and adapted to indicate an erasing position by a combination with an indication of said position-indicating means.

Claim 7

An eraser for an electronic blackboard according to claim 4, wherein a switch (SW₁′, SW₂′) for obtaining a signal corresponding to a pressing force is used to enlarge or reduce the region of an erasing portion in correspondence with said pressing force.