# US 7,743,993 B2 · Barcode scanner with linear automatic gain control (AGC), modulation transfer function detector, and selectable noise filter > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,743,993 B2 - Document ID: US7743993B2 - Status: Granted - Kind: B2 - Application number: 11/709,969 - Filed: 2007-02-22 - Published: 2007-07-12 - Granted: 2010-06-29 - Earliest claimed: 2004-04-16 - Assignees: Microscan Systems, Inc. - Inventors: Jesse J. Kolstad; Bryan L. Davis - Web page: https://patentgrep.com/patent/US7743993B2 ## CPC - G06K 7/10851: {Circuits for pulse shaping, amplifying, eliminating noise signals, checking the function of the sensing device (basic electronic circuitry H03)} - G06K: GRAPHICAL DATA READING (image or video recognition or understanding G06V); PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS ## Abstract According to embodiments of the present invention, a barcode scanner platform is provided in which the gain of an analog signal representative of a barcode is controlled using a control loop. In embodiments, an MTF detector generates a value (e.g., DC) representative of a low frequency portion (wide or out of optical focus elements) of the analog signal and a second value (e.g., DC) representative of a high frequency portion (narrow elements or in optical focus elements) of the analog signal. The processor uses the first and the second values and a reference amplitude to determine a gain signal. The processor provides the gain signal to an AGC circuit that provides a linear response to the gain signal using matched JFETs. A noise filter can be enabled or disabled based on the first value, the second value, and/or the barcode scanner platform read rate. ## Claims ### Claim 1 A method, comprising: determining that an amplitude of a first frequency portion of an analog signal representing a barcode is approximately equal to an amplitude of a second frequency portion of the analog signal; determining that a noise filter is OFF; determining that a read rate is less than a predetermined value; and turning the noise filter ON in response to the read rate being less than the predetermined value. ### Claim 2 (depends on 1) The method of claim 1, further comprising: determining that the read rate increased; and leaving the noise filter ON in response to the increased read rate. ### Claim 3 (depends on 1) The method of claim 1, further comprising: determining that the read rate decreased; and turn the noise filter OFF in response to the decreased read rate. ### Claim 4 An apparatus, comprising: logic to determine that an amplitude of a first frequency portion of an analog signal representative of a barcode is approximately equal to an amplitude of a second frequency portion of the analog signal, to determine that a noise filter is OFF, to determine that a read rate is less than a predetermined value, and to turn the noise filter ON in response to the read rate being less than the predetermined value. ### Claim 5 (depends on 4) The apparatus of claim 4, further wherein frequencies in the first frequency portion are lower than frequencies in the second frequency portion. ### Claim 6 (depends on 4) The apparatus of claim 4, wherein frequencies in the first frequency portion are higher than frequencies in the second frequency portion. ### Claim 7 (depends on 4) The apparatus of claim 4, wherein frequencies in the first frequency portion are within frequencies in the second frequency portion. ### Claim 8 (depends on 4) The apparatus of claim 4, wherein the logic is further to determine that the read rate increased and to leave the noise filter ON in response to the increased read rate. ### Claim 9 (depends on 4) The apparatus of claim 4, wherein the logic is further to determine that the read rate decreased and to turn the noise filter OFF in response to the decreased read rate. ### Claim 10 An apparatus, comprising: a first gain element and a second gain element matched to the first gain element to generate a linear response to a gain signal, the gain signal being based on a predetermined amplitude for a first analog signal, the first analog signal being representative of a barcode; circuitry to apply the linear response to the first analog signal to generate a second analog signal; circuitry to determine an amplitude of a first frequency portion of the second analog signal, and to determine an amplitude of a second frequency portion of the second analog signal; and logic to determine that the amplitude of the first frequency portion is approximately equal to the amplitude of the second frequency portion to determine that a noise filter is OFF, to determine that a read rate is less than a predetermined value, and to turn the noise filter ON in response to the read rate being less than the predetermined value. ### Claim 11 (depends on 10) The apparatus of claim 10, wherein the first and/or the second gain element is a transistor. ### Claim 12 (depends on 11) The apparatus of claim 11, wherein the first and/or the second gain element is an FET. ### Claim 13 (depends on 12) The apparatus of claim 12, wherein the first and/or the second gain element is a JFET, a MOSFET, and/or a GaAs FET. ### Claim 14 (depends on 11) The apparatus of claim 11, wherein the first and/or the second gain element is a bipolar junction transistor (BJT). ### Claim 15 (depends on 14) The apparatus of claim 14, wherein the first and/or the second gain element is a heterojunction bipolar junction transistor (HBJT). ### Claim 16 (depends on 10) The apparatus of claim 10, wherein the first and/or the second gain element is a vacuum tube. ### Claim 17 (depends on 10) The apparatus of claim 10, further wherein frequencies in the first frequency portion are lower than frequencies in the second frequency portion. ### Claim 18 (depends on 10) The apparatus of claim 10, wherein frequencies in the first frequency portion are higher than frequencies in the second frequency portion. ### Claim 19 (depends on 10) The apparatus of claim 10, wherein frequencies in the first frequency portion are within frequencies in the second frequency portion. ### Claim 20 (depends on 10) The apparatus of claim 10, wherein the logic is further to determine that the amplitude of the second frequency portion of the analog signal is less than the amplitude of a first frequency portion of the analog signal. ### Claim 21 (depends on 10) The apparatus of claim 10, wherein the logic is further to apply a second gain to the analog signal based on the amplitude of the first frequency portion of the analog signal. ### Claim 22 (depends on 10) The apparatus of claim 10, wherein the logic is further to determine that the read rate increased and to leave the noise filter ON in response to the increased read rate. ### Claim 23 (depends on 10) The apparatus of claim 10, wherein the logic is further to determine that the read rate decreased and to turn the noise filter OFF in response to the decreased read rate. ### Claim 24 An apparatus, comprising: a gain element having a response; a map of the gain element response, the combination of the gain element and the map of the gain element response to generate a linear response to a gain signal, the gain signal based on a predetermined amplitude for a first analog signal, the first analog signal being representative of a barcode; circuitry to apply the linear response to the first analog signal to generate a second analog signal; logic to determine an amplitude of a first frequency portion of the second analog signal, and to determine an amplitude of a second frequency portion of the second analog signal; and logic to determine that the amplitude of the first frequency portion is approximately equal to the amplitude of the second frequency portion to determine that a noise filter is OFF, to determine that a read rate is less than a predetermined value, and to turn the noise filter ON in response to the read rate being less than the predetermined value. ### Claim 25 (depends on 24) The apparatus of claim 24, wherein the gain element is a transistor. ### Claim 26 (depends on 25) The apparatus of claim 25, wherein the gain element is an FET. ### Claim 27 (depends on 26) The apparatus of claim 26, wherein the gain element is a JFET, a MOSFET, and/or a GaAs FET. ### Claim 28 (depends on 25) The apparatus of claim 25, wherein the gain element is a bipolar junction transistor (BJT). ### Claim 29 (depends on 28) The apparatus of claim 28, wherein the gain element is a heterojunction bipolar junction transistor (HBJT). ### Claim 30 (depends on 24) The apparatus of claim 24, wherein the gain element is a vacuum tube. ### Claim 31 (depends on 24) The apparatus of claim 24, further wherein frequencies in the first frequency portion are lower than frequencies in the second frequency portion. ### Claim 32 (depends on 24) The apparatus of claim 24, wherein frequencies in the first frequency portion are higher than frequencies in the second frequency portion. ### Claim 33 (depends on 24) The apparatus of claim 24, wherein frequencies in the first frequency portion are within frequencies in the second frequency portion. ### Claim 34 (depends on 24) The apparatus of claim 24, wherein the logic is further to determine that the amplitude of the second frequency portion of the analog signal is less than the amplitude of a first frequency portion of the analog signal. ### Claim 35 (depends on 24) The apparatus of claim 24, wherein the logic is further to apply a second gain to the analog signal based on the amplitude of the first frequency portion of the analog signal. ### Claim 36 (depends on 24) The apparatus of claim 24, wherein the logic is further to determine that the read rate increased and to leave the noise filter ON in response to the increased read rate. ### Claim 37 (depends on 24) The apparatus of claim 24, wherein the logic is further to determine that the read rate decreased and to turn the noise filter OFF in response to the decreased read rate. ### Claim 38 An apparatus, comprising: logic to apply a first gain to an analog signal representative of a barcode based on a predetermined amplitude for the analog signal, to determine an amplitude of a first frequency portion of the analog signal, and to determine an amplitude of a second frequency portion of the analog signal; and logic to determine that the amplitude of the first frequency portion is approximately equal to the amplitude of the second frequency portion to determine that a noise filter is OFF, to determine that a read rate is less than a predetermined value, and to turn the noise filter ON in response to the read rate being less than the predetermined value. ### Claim 39 (depends on 38) The apparatus of claim 38, further wherein frequencies in the first frequency portion are lower than frequencies in the second frequency portion. ### Claim 40 (depends on 38) The apparatus of claim 38, wherein frequencies in the first frequency portion are higher than frequencies in the second frequency portion. ### Claim 41 (depends on 38) The apparatus of claim 38, wherein frequencies in the first frequency portion are within frequencies in the second frequency portion. ### Claim 42 (depends on 38) The apparatus of claim 38, wherein the logic is further to determine that the amplitude of the second frequency portion of the analog signal is less than the amplitude of a first frequency portion of the analog signal. ### Claim 43 (depends on 38) The apparatus of claim 38, wherein the logic is further to apply a second gain to the analog signal based on the amplitude of the first frequency portion of the analog signal. ### Claim 44 (depends on 38) The apparatus of claim 38, wherein the logic is further to determine that the read rate increased and to leave the noise filter ON in response to the increased read rate. ### Claim 45 (depends on 38) The apparatus of claim 38, wherein the logic is further to determine that the read rate decreased and to turn the noise filter OFF in response to the decreased read rate. ### Claim 46 An apparatus, comprising: a first gain element and a second gain element matched to the first gain element to generate a linear response to a gain signal, the gain signal being based on a predetermined amplitude for a first analog signal, the first analog signal being representative of a barcode; circuitry to apply the linear response to the first analog signal to generate a second analog signal; and logic to determine an amplitude of a first frequency portion of the second analog signal is approximately equal to an amplitude of a second frequency portion of the second analog signal, to determine that a noise filter is OFF, to determine that a read rate is less than a predetermined value, and to turn the noise filter ON in response to the read rate being less than the predetermined value. ### Claim 47 (depends on 46) The apparatus of claim 46, wherein the first and/or the second gain element is a transistor. ### Claim 48 (depends on 47) The apparatus of claim 47, wherein the first and/or the second gain element is an FET. ### Claim 49 (depends on 48) The apparatus of claim 48, wherein the first and/or the second gain element is a JFET, a MOSFET, and/or a GaAs FET. ### Claim 50 (depends on 47) The apparatus of claim 47, wherein the first and/or the second gain element is a bipolar junction transistor (BJT). ### Claim 51 (depends on 50) The apparatus of claim 50, wherein the first and/or the second gain element is a heterojunction bipolar junction transistor (HBJT). ### Claim 52 (depends on 46) The apparatus of claim 46, wherein the first and/or the second gain element is a vacuum tube. ### Claim 53 (depends on 46) The apparatus of claim 46, wherein the logic is further to determine that the read rate increased and to leave the noise filter ON in response to the increased read rate. ### Claim 54 (depends on 46) The apparatus of claim 46, wherein the logic is further to determine that the read rate decreased and to turn the noise filter OFF in response to the decreased read rate. ### Claim 55 An apparatus, comprising: a gain element having a response; a map of the gain element response, the combination of the gain element and the map of the gain element response to generate a linear response to a gain signal, the gain signal based on a predetermined amplitude for a first analog signal, the first analog signal being representative of a barcode; circuitry to apply the linear response to the first analog signal to generate a second analog signal; and logic to determine an amplitude of a first frequency portion of the second analog signal is approximately equal to an amplitude of a second frequency portion of the second analog signal, to determine that a noise filter is OFF, to determine that a read rate is less than a predetermined value, and to turn the noise filter ON in response to the read rate being less than the predetermined value. ### Claim 56 (depends on 55) The apparatus of claim 55, wherein the gain element is a transistor. ### Claim 57 (depends on 56) The apparatus of claim 56, wherein the gain element is an FET. ### Claim 58 (depends on 57) The apparatus of claim 57, wherein the gain element is a JFET, a MOSFET, and/or a GaAs FET. ### Claim 59 (depends on 56) The apparatus of claim 56, wherein the gain element is a bipolar junction transistor (BJT). ### Claim 60 (depends on 59) The apparatus of claim 59, wherein the gain element is a heterojunction bipolar junction transistor (HBJT). ### Claim 61 (depends on 55) The apparatus of claim 55, wherein the gain element is a vacuum tube. ### Claim 62 (depends on 55) The apparatus of claim 55, wherein the logic is further to determine that the read rate increased and to leave the noise filter ON in response to the increased read rate. ### Claim 63 (depends on 55) The apparatus of claim 55, wherein the logic is further to determine that the read rate decreased and to turn the noise filter OFF in response to the decreased read rate.