Optical character reader

• US 4,809,351 A
• Filed: 12/11/1986
• Issued: 02/28/1989
• Est. Priority Date: 06/07/1985
• Status: Expired due to Fees

• Current Assignee: SABA Technologies Incorporated
• Original Assignee: SABA Technologies Incorporated
• Inventors: Busse, Frederick L., Anderson, Robert L. Jr., Abramovitz, Robert G., Shorthill, Lawrence R., Celarier, Stuart A., Poublan, Jean-Yves H.
• Primary Examiner(s): Boudreau, Leo H.
• Application Number:
  US06/940,294
• Time in Patent Office: 810 Days
• Field of Search: 382/59, 382/61, 382/62, 382/65, 382/67, 382/68, 235/472, 235/474
• US Class Current: 382/313
• CPC Class Codes: G06V 10/147 Details of sensors, e.g. sensor lenses fingerprint or palmprint sensors G06V40/13; vascular sensors G06V40/145; eye sensors G06V40/19
• CPC Class Codes: G06V 30/142 using hand-held instruments; Constructional details of the instruments

Abstract

An optical scanning system operates asynchronously by electro-optically detecting movement of a scanning unit directly from the data being scanned. A first embodiment of the system includes two sets of optical sensors in a hand-held unit. One set extends transversely of a scanning direction for detecting the optical pattern, and a second set is approximately aligned with the scanning direction for detecting relative movement between the pattern and the scanning unit. Relative movement is detected by detecting a pattern in a first subset of the second set of sensors and then sensing a shift of the detected pattern to a second subset of the second set of sensors. In response to detecting a unit movement, the optical states of the first set of sensor elements are polled to record a portion of the pattern along the line. This response is preferably triggered indirectly by calculating an average time interval between relative movements and periodically polling the first set of sensors at a rate set by this average interval. Upon detecting a uniform optical state of the second set of sensors, such as when scanning across a blank region in the pattern, sensing of the optical state of the first sensors continues at periodic intervals so long as the uniform state continues to be detected. The optical information is thus obtained in a succession of steps, and is assembled by the host computer. A second embodiment of the system differs from the first embodiment in that the former uses a rectangular array of imaging elements arranged in rows and columns and calculates an estimate of the instantaneous rate of relative movement. Each of the rows of imaging elements is aligned generally parallel to the scanning direction and changes optical states in a manner analogous to that of the line of second imaging elements described above. The second embodiment promotes increased accuracy during collection of optical information for situations in which the scanning direction is misaligned from the optical information and the scanning velocity is nonuniform.

Claims

1. A method for scanning a pattern of optical information on a surface, comprising:

projecting a plurality of first imaging elements along a line onto the surface;

projecting at least two second imaging elements onto the surface alongside the line of first imaging elements;

moving the first and second imaging elements laterally of the line in a scanning direction across the pattern;

sensing an optical state of the second imaging elements;

detecting a change in the optical state of the second imaging elements corresponding to relative movement between the second imaging elements and the pattern;

calculating an average rate of the relative movement;

generating a signal in accordance with the detected change in optical state of the second imaging elements;

in response to the signal, sensing at periodic intervals corresponding to the calculated average rate of movement an optical state of the first imaging elements corresponding to a portion of the pattern along the line;

detecting a uniform optical state of the second imaging elements; and

initiating the sensing of optical state of the first imaging elements at the periodic intervals so long as the uniform state continues to be detected.

2. A method for scanning a pattern of optical information on a surface, comprising:

projecting a plurality of first imaging elements along a line onto the surface;

projecting at least two second imaging elements onto the surface alongside the line of first imaging elements;

moving the first and second imaging elements laterally of the line in a scanning direction across the pattern;

sensing an optical state of the second imaging elements;

detecting a change in the optical state corresponding to relative movement between the second imaging elements and the pattern;

generating a signal in accordance with the detected change in optical state of the second imaging elements;

in response to the signal, sensing an optical state of the first imaging elements corresponding to a portion of the pattern along the line;

starting a first timer when a first change is detected in the optical state of the second imaging elements;

stopping the first timer when a next change is detected in the optical state of the second imaging elements;

storing in a memory the elapsed time measured by the timer;

calculating from the elapsed time stored in the memory an average time interval between detected changes in the optical state of the second imaging elements;

repeating the above sequence of starting and stopping the first timer, storing the measured time, and calculating an updated average time each time a change is detected in the optical state of the second imaging elements; and

while the above sequence is repeating, concurrently executing the steps;

starting a second timer;

when the second timer has reached the average time most recently computed in the above-described sequence of steps, sensing the optical state of the first imaging elements; and

repeating the above two steps.

3. The method of claim 2, in which the storing step includes storing a predetermined number of successive elapsed times and, each time the above sequence is repeated, deleting the oldest stored time and storing the most recent elapsed time.

4. The method of claim 3, including initially storing a predetermined average time interval.

5. The method of claim 2, in which the storing step includes storing up to a predetermined number of successive elapsed times and, each time the above sequence is repeated, summing the stored times and dividing by the number of stored times, to calculate the average time interval.

6. A method of detecting movement of an optical scanning device in a scanning direction relative to a surface on which optical data appear, comprising:

projecting onto the surface plural optical imaging elements arranged in rows and columns to form a two dimensional array, the rows having directional components generally parallel to the scanning direction;

moving the array of optical imaging elements relative to the surface in the scanning direction;

sensing from the array of optical imaging elements a sequence of frames of output data corresponding to the optical data; and

computing from the frames of output data estimates of the speed of the movement of the array of optical imaging elements relative to the surface, the computation of the estimates of the speed of movement including detecting in a frame of output data for each row in the array, positions of adjacent imaging elements providing different output data;

detecting in a succeeding frame of output data for each row in the array, positions of adjacent imaging elements providing different output data;

calculating the number of changes of positions of the adjacent imaging elements for the frame and the succeeding frame of output data; and

determining whether the number of changes of positions exceeds a predetermined standard value, thereby to provide an indication of the amount succeeding frames of output data.

7. A method of detecting movement of an optical scanning device in a scanning direction relative to a surface on which optical data appear, comprising:

projecting onto the surface plural optical imaging elements arranging in rows and columns to form a two dimensional array, the rows having directional components generally parallel to the scanning direction;

moving the array of optical imaging elements relative to the surface in the scanning directions;

sensing from the array of optical imaging elements a sequence of frames of output data corresponding to the optical data;

detecting in a frame of output data for each row in the array, positions of adjacent imaging elements providing different output data;

detecting in a succeeding frame of output data for each row in the array, positions of adjacent imaging elements providing different output data;

calculating the number of changes of positions of the adjacent imaging elements for the frame and the succeeding frame of output data;

calculating ratios of the number of changes of positions from a frame to an adjacent frame for successive frames in the sequence; and

comparing the computed ratios to a predetermined standard value to provide an estimate of the instantaneous speed of the relative movement.