Encoder system using linear array sensor for high resolution

An encoder system comprising:

• a) an encoder element comprising a series of alternating transparent and opaque segments arranged sequentially along a path on said element wherein adjacent ones of said segments meet in a transition, the spacing between segments of like optical properties defining a relatively coarse pitch relationship;
• b) a charge-coupled device comprising an array of photoelectric sensor elements in closely spaced, fine pitch relation arranged sequentially along a path, said device providing signals containing information on the state of said sensor elements at a given time;
• c) optical means for optically coupling said encoder element and said charge-coupled device so that transitions on said encoder element are imaged onto said charge coupled device;
• d) said encoder element and said charge coupled device being oriented relative to each other so that said path of said encoder element segments and said path of said array sensor elements are in operative relationship such that upon movement of said encoder element relative to said charge coupled device said encoder element transitions are imaged onto said charge coupled device along said path of said array sensor elements;
• e) said encoder element adapted for movement relative to said charge coupled device so that the location of imaged transitions on said charge-coupled device is a function of the speed and position of said encoder element;
• and
• f) processing means connected to said charge-coupled device for converting information on the state of said sensor elements including the location of imaged transitions thereon into first and second output signals containing information on the position and velocity, respectively, of said encoder element.

An encoder system comprising:

• a) an encoder element adapted for rotation about an axis, and having a series of segments arranged along a substantially circular path substantially concentric with said axis, adjacent segments being of different optical characteristics and meeting in a transition, two adjacent segments comprising a cycle and said element having a number of cycles (Nc) equally spaced around said path;
• b) an array of photosensitive elements having a longitudinal axis, said elements being spaced at a specific sensor pitch (Sp) along said axis;
• c) optical means for directing light along a path through said segments and onto said array for imaging segments at a predetermined magnification (Mag) onto a number (Sn) of said photosensitive elements;
• d) the minimum number of encoder element cycles being defined by the relationship:
• ##EQU13## where r is the radius of the encoder element measured from the axis thereof to a point on said path where light is incident on said segments;
• and
• e) the resolution (Res) of said encoder system being defined by the relationship:
• ##EQU14##

An encoder system comprising:

• a) an encoder element adapted for linear movement and having a series of segments arranged along a substantially linear path, adjacent segments having different optical characteristics and meeting in a transition, two adjacent segments comprising a cycle, and said element having a number of cycles equally spaced along said path and the number of said cycles in a unit length being the encoder element pitch (Ep);
• b) an array of photosensitive elements having a longitudinal axis, said elements being spaced at a specific pitch (Sp) along said axis;
• c) optical means for directing light along a path through said segments and onto said array for imaging segments at a predetermined magnification (Mag) onto a number (Sn) of said photosensitive elements;
• d) the encoder element pitch being defined by the relationship:
• ##EQU16## and e) the resolution (Res) of said encoder system being defined by the relationship:
• ##EQU17##

An encoder method for position and velocity control comprising the steps of:

• a) providing an encoder in operative relationship to the output of a system to be controlled, said encoder having a series of segments arranged sequentially along a path with adjacent segments having different properties and meeting in a transition, there being a plurality of transitions spaced along said path in a relatively coarse pitch relation;
• b) providing an array of sensor elements sequentially along a path in closely spaced fine pitch relation each having two states;
• c) providing a coupling medium between said encoder and said array which is responsive to the properties of said encoder and which causes a change in the state of said sensor elements in response to movement of said encoder;
• d) orienting said encoder and said array of sensor elements relative to each other so that said path of said encoder segments and said path of said array sensor elements are in operative relationship such that upon movement of said encoder relative to said array said encoder segments cause a change in state of said array sensor elements along said path of said array sensor elements;
• e) moving said encoder relative to said array so that said array provides signals containing information as to the location of said transitions;
• and
• f) utilizing said array signals to provide position and velocity signals for controlling said system.

An encoder system comprising:

• a) an encoder element comprising a series of segments arranged along a path on said element, said segments having two different properties and adjacent segments being of different properties, the spacing between segments of like properties defining a relatively coarse pitch relationship;
• b) an array of sensor elements in closely-spaced fine pitch relation each having two states;
• c) means for providing a coupling medium between said encoder element and said array which is responsive to the properties of said encoder element segments and which causes a change in state of said sensor elements in response to movement of said encoder element relative to said array;
• c) said encoder element adapted for movement relative to said array so that the number of sensor elements changed in state during a given time is a function of the speed and position of said encoder element;
• and
• e) processing means connected to said array for converting information on the state of said sensor elements including the number of sensor elements changed in state into first and second output signals containing information on the position and velocity, respectively, of said encoder element, said processing means comprising processor means including storage means and calculating means and conversion and timing means for establishing a sampling interval and for converting signals from said array during said sampling interval into signals containing information on the present relationship between said encoder element and said array for storage in said storage means and for operation by said calculating means so that said calculating means compares the present encoder element-array relationship to the previous encoder element-array relationship stored in said storage means and calculates the present position and velocity of said encoder element to provide said first and second output signals.

An encoder system comprising:

• a) an encoder element comprising a series of alternating transparent and opaque segments arranged along a path on said element wherein adjacent ones of said segments meet in a transition, the spacing between segments of like optical properties defining a relatively coarse pitch relationship;
• b) a charge-coupled device comprising an array of photoelectric sensor elements in closely spaced, fine pitch relation, said device providing signals containing information on the state of said sensor elements at a given time;
• c) optical means for optically coupling said encoder element and said charge-coupled device so that transitions on said encoder element are imaged onto said charge coupled device;
• d) said encoder element adapted for movement relative to said charge coupled device so that the location of imaged transitions on said charge-coupled device is a function of the speed and position of said encoder element;
• and
• e) processing means connected to said charge-coupled device for converting information on the state of said sensor elements including the location of imaged transitions thereon into first and second output signals containing information on the position and velocity, respectively, of said encoder elements, said processing means comprising processor means including storage means and calculating means and conversion and timing means for establishing a sampling interval and for converting signals from said charge-coupled device during said sampling interval into signals containing information on the present location of transitions imaged on said charge coupled device for storage in said storage means and for operation by said calculating means, so that said calculating means compares the present transition location to the previous transition location stored in said storage means and calculates the present position and velocity of the encoder element to provide said output signal.

An encoder method for position and velocity control comprising the steps of:

• a) providing an encoder in operative relationship to the output of a system to be controlled, said encoder having a series of segments arranged along a path with adjacent segments having different properties and meeting in a transition, there being a plurality of transitions spaced along said path in a relatively coarse pitch relation;
• b) providing an array of sensor elements in closely spaced fine pitch relation each having two states;
• c) providing a coupling medium between said encoder and said array which is responsive to the properties of said encoder and which causes a change in the state of said sensor elements in response to movement of said encoder;
• d) moving said encoder relative to said array so that said array provides signals containing information as to the location of said transitions;
• and
• e) utilizing said array signals to provide position and velocity signals for controlling said system comprising providing a sampling interval, determining the present transition location during each sampling interval, storing the present transition location, comparing the present transition location to the previously stored transition location to obtain a difference quantity, adding the difference quantity to the previous stored transition location to obtain a position information quantity to provide the position signal, and dividing the difference quantity by the sampling interval to obtain a velocity information quantity to provide the velocity signal.