A coordinate input apparatus comprises: a vibration pen to generate a vibration; a vibration propagating plate to propagate the vibration generated by the pen by touching the pen to the plate; vibration sensors to detect the vibration propagated to the plate; a supporting member which supports the plate and whose vibration propagating velocity is slower than the plate; a position coordinate calculating circuit to calculate the position coordinates of the pen on the plate on the basis of the detection signals from the sensors; and a display which is provided below the supporting member and displays the calculated coordinates. The plate is made of metal or transparent glass and the supporting membrr is made of a transparent synthetic resin. The supporting member is directly in contact with the plate at a rough surface, its acoustic impedance value is different from the plate, and its vibration attenuation ratio is larger than that of the plate. Since the vibration wave component propagated to the sensors is not influenced by the interference of the vibration propagated in the support member, the coordinates can be accurately detected on the basis of the vibration detection waveforms without distortion.
In a coordinates input apparatus in which a vibration input from a vibration pen is detected by a plurality of vibration sensors attached to a transparent vibration propagating plate such as an acrylic or glass plate and the coordinate position of the vibration pen is detected from the vibration propagation times until the vibration sensors, the sensors and the vibration proof material are arranged in a manner such that a distance between the attaching boundary surface of the vibration proof material attached to the peripheral portion of the vibration propagating plate and the center of each sensor which is attached to the input side than the attaching boundary surface of the vibration proof material lies within a range from 0.5 time to a value less than 1.0 time as large as the diameter of the sensor, preferably, within a range from 1.0 mm to a value less than 2.0 mm.
A coordinate input apparatus for detecting a vibration transmitted from a vibration input pen by a plurality of vibration sensors arranged on a vibration transmission member, and for determining coordinates of the vibration input pen from vibration propagation times required between the position of the vibration input pen to the positions of the vibration sensors, includes a vibration-isolating member formed in a peripheral portion of the vibration transmission member. The vibration-isolating member has a multi-layered structure consisting of a plurality of vibration-isolating layers formed so that a layer nearer to the vibration transmission plate has a lower acoustic impedance than that of a layer farther from the vibration transmission plate.
A coordinate input apparatus according to the present invention eliminates distortion caused by interference of a asymmetrical plate wave with an asymmetrical plate wave from the vibrations which are detected after they have been propagated in a vibration transmitting member and performs a highly accurate position coordinate detection. The vibrations of a pen which is brought into contact with the vibration transmitting member are detected by sensors provided on both the front and rear surfaces of the vibration transmitting member to determine a coordinate of a position where the vibrating pen has been brought into contact. At that time, the vibration sensors mounted on the front and rear of the vibration transmitting member in an opposed relation detect vibrations on the two surfaces of the transmitting member. The signals which are detected by each pair of front and rear sensors represent vibrations in which the asymmetrical plate waves having the same phase and the 180.degree. out-of-phase asymmetrical plate waves are superimposed on top of one another. The signals of the two sensors are input to a differential circuit. A resultant differential signal is input to a signal waveform detecting circuit. Since the differential signal is a signal in which the asymmetrical waves are cancelled with each other and in which the asymmetrical waves are amplified by twice, reduction in the vibration detection accuracy which is caused by distortion of waveforms can be prevented.
A coordinates input apparatus which detects vibration, inputted by a vibration-input pen, by a plurality of vibration sensors provided on a vibration-transmitting tablet, and derives coordinates of a vibration-input point based on vibration transmitting time on the vibration-transmitting tablet. The vibration-transmitting tablet comprises a glass substrate and two sheets of resinous film laminated on the glass substrate. The two sheets of resinous film are laminated on both surfaces of the glass substrate in an orientation such that the stretched directions of the resinous film differ for 90 degrees. By this, a vibration-transmitting tablet where sheets of protection film are laminated, and a coordinates input apparatus which minimizes the changes in vibration propagation velocity depending on the propagation directions, are realized.
A coordinate input apparatus which can attain an accurate coordinate input operation, includes a sensor for detecting an input variation. The vibration is amplified, and an envelope detection circuit generates the envelope of the amplified vibration. A gate signal generation circuit receives the envelope and a second-order differential signal of the envelope generated by an inflection point detection circuit. The gate signal generation circuit attenuates the envelope and adds a predetermined offset to the attenuated envelope. The gate signal generation circuit compares the sum signal with the second-order differential signal to generate a gate signal. In the duration of the gate signal, a tg comparator detects, as a group delay time, a time up to the zero cross point of the second-order differential signal, and a tp comparator detects, as a phase delay time, a time up to the zero cross point in a predetermined order of a phase signal. An arithmetic control circuit calculates the coordinate position of a vibration input source on the basis of these delay times.
