IPC분류정보
국가/구분 |
United States(US) Patent
등록
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국제특허분류(IPC7판) |
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출원번호 |
US-0946797
(2001-09-04)
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발명자
/ 주소 |
- Swanson,Mark R.
- Apperson,William C.
- Zahrte, Sr.,Donald K.
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출원인 / 주소 |
- Renaissance Learning, Inc.
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대리인 / 주소 |
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인용정보 |
피인용 횟수 :
3 인용 특허 :
9 |
초록
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A device and method for reading optical marks are disclosed. The device, an optical mark reader (OMR) has an array of photo sensors with light-emitting diodes (LEDs), which are driven by digital-to-analog converters (DACs), which are in turn controlled by a microcontroller. When calibrating the OM
A device and method for reading optical marks are disclosed. The device, an optical mark reader (OMR) has an array of photo sensors with light-emitting diodes (LEDs), which are driven by digital-to-analog converters (DACs), which are in turn controlled by a microcontroller. When calibrating the OMR, the sensors read a white card, and the microcontroller adjust the DACs so that the outputs of all sensors are at a voltage close to the saturation points of the photo-transistors in the sensors so that the maximum useable ranges of the sensors are utilized. The sensors then read one or more patterns of known grayscales and their response voltages are recorded. The microcontroller generates an array of voltage values as a function of grayscale for each sensor and store the values in a memory device. When reading an optical marks, the sensor output voltage in response to a mark is looked up in the table of voltages values stored in the memory device to determine the grayscale of the mark. Various algorithms may be employed to calculate an apparent grayscale to allow the test taker's true intent be ascertained without requiring the test taker to make a perfect mark.
대표청구항
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What is claimed is: 1. An optical mark reader, comprising: a. a plurality of light sources, each configured and arranged to illuminate an area of a surface, the illuminated area having a reflectance; b. a plurality of light detectors, each configured and arranged to receive at least a portion of an
What is claimed is: 1. An optical mark reader, comprising: a. a plurality of light sources, each configured and arranged to illuminate an area of a surface, the illuminated area having a reflectance; b. a plurality of light detectors, each configured and arranged to receive at least a portion of any light reflected by the surface from a respective one of the plurality of light sources and output a signal indicative of the intensity of the received light; c. a controller operatively connected to the plurality of detectors and configured and arranged to receive the signals output from the plurality of detectors; and d. a plurality of power sources, each power source operatively connected to one of the plurality of light sources and operatively connected to the controller, and configured and arranged to supply power to the light source in response to signals from the controller, wherein the controller is configured and arranged to generate, responsive to the output of each of the plurality of detectors, a signal indicative of the reflectance of the respective illuminated area. 2. The optical mark reader of claim 1, further comprising a memory device operatively connected to the controller, wherein the controller is configured and arranged to read information from, and write information to, the memory device, wherein the memory device is encoded with calibration information, wherein the controller is configured and arranged to generate the signal indicative of the reflectance of the respective illuminated area in further response to the calibration information. 3. The optical mark reader of claim 2, wherein the controller is switchable to a calibration mode, in which mode the controller is configured and arranged to generate, responsive to the signals output from each of the plurality of detectors, a control signal that alters the power output of the power source to the light source connected to the power source until the signal output from the detector reaches a predetermined level when the respective illuminated area has a first predetermined reflectance, and to store a code indicative of the final control signal in the memory device. 4. The optical mark reader of claim 3, wherein the controller is configured and arranged to derive calibration information based at least partially on the signals output from each of the detector receiving reflected light from an area with a second predetermined reflectance, and encode the memory device with calibration information. 5. The optical mark reader of claim 1, wherein the plurality of light sources are light-emitting diodes and the power sources are configured and arranged to receive digital signals from the controller and supply power to the light-emitting diodes according to the digital signals received from the controller. 6. The optical mark reader of claim 5, wherein the power sources are digital-to-analog converters, with the analog side configured and arranged to power the light-emitting diodes, and the digital side configured and arranged to receive digital signals from the controller. 7. The optical mark reader of claim 1, further comprising a computer interface module between the controller and a computer, wherein the controller is configured and arranged to transmit data to, and receive data from, the computer through the computer interface. 8. The optical mark reader of claim 7, wherein the controller comprises a memory area for storing program and is configured and arranged to receive programs from the computer through the computer interface. 9. A method of calibrating an optical mark reader, the method comprising: a. illuminating a surface area having a predetermined reflectance using a light emitter of the optical mark reader, wherein the light emitter is one of a plurality of light emitters in an array; b. receiving at least a portion of any light reflected by the surface area using a light detector of the optical mark reader, wherein the light detector is one of a plurality of light detectors in an array; c. measuring a signal generated by the light detector responsive to the received light; and d. electronically adjusting a power source connected to the light emitter to vary the intensity of the illumination by the light emitter until the signal measured in step (c) becomes a predetermined value, wherein the power source is one of a plurality of power sources, and each power source is connected to a single light emitter. 10. The method of claim 9, wherein step (d) includes supplying power to the light emitter using a power controller that is configured and arranged to supply power to the light emitter in response to a digital signal and applying a variable digital signal applied to the power controller. 11. The method of claim 10, wherein step of supplying power includes supplying power to the light emitter using a digital-to-analog converter. 12. The method of claim 9, further comprising e. illuminating a surface area of a second reflectance using the light emitter; f. receiving at least a portion of the light reflected by the surface area from the light emitter; g. generating a signal indicative of the intensity of the light received by the light receiver; h. calculating one or more calibration factors based on the signal. 13. A method of inspecting a bubble on a scan card, the method comprising: a. measuring the darkness of the surface within the bubble at a plurality of locations; b. recording the peak darkness among the measurements; c. calculating the average of all darkness measured at the plurality of locations; d. generating a signal as a function of the peak darkness and the average. 14. The method of claim 13, wherein step (d) includes generating a signal indicative of the peak darkness if the difference between the peak darkness and the average is smaller than a predetermined percentage of the peak darkness, and generating a signal indicative of the average if the difference is not smaller than the predetermined percentage.
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