1. A system for locating a signal source in a wireless local area network (WLAN), comprising:
at least one WLAN signal source positioned at a known location that transmits a wireless radio frequency (RF) signal;
a plurality of receivers, wherein each receiver is configured to:
receive the RF signal from the at least one WLAN signal source, and
generate, and transmit to a processor, a time-of-arrival measurement for the RF signal relative to a clock of the receiver;
wherein the clocks of the plurality of receivers are unsynchronized; and
the processor configured to:
receive the time-of-arrival measurements from the plurality of receivers, and
for each receiver, define a respective time relationship between the clock of the receiver and a system time based on the received time-of-arrival measurement from the receiver.
2. A system according to claim 1, and further comprising a tag transmitter positioned at each WLAN signal source.
3. A system according to claim 2, wherein each tag transmitter transmits an RF signal having data identifying an object to which the tag transmitter is associated.
4. A system according to claim 1, wherein each receiver comprises a wireless access point of the WLAN.
5. A system according to claim 1, and further comprising a plurality of WLAN signal sources at fixed, known locations.
6. A system according to claim 1, and further comprising a tag transmitter embedded at a receiver and operative as a WLAN beacon.
7. A system according to claim 1, wherein said processor is operative for determining clock timing relationships for clocks based on one of at least propagation or processing delays in the receivers for synchronizing receiver performance.
8. A system according to claim 1, wherein each WLAN signal source includes a circuit for transmitting a pseudo-random spread spectrum RF signal.
9. A system according to claim 1, wherein said processor is operative for processing first-to-arrive signals at each receiver.
10. The system of claim 1, wherein each of the receivers is further configured to:
receive a second wireless RF signal from a WLAN signal source at an unknown location; and
generate, and transmit to the processor, a second time-of-arrival measurement for the second RF signal relative to the clock of the receiver; and
wherein the processor is configured to receive the second time-of-arrival measurements from each of the receivers and, for each time-of-arrival measurement, apply the respective time relationship between the clock of the receiver from which the time-of-arrival measurement was received and the system time to determine a time-of-arrival measurement relative to the system time.
11. The system of claim 1, wherein the system time is defined as a mean or a median of the unsynchronized clocks of the plurality of receivers.
12. The system of claim 1, wherein the system time is unsynchronized with at least all but one of the clocks of the receivers.
13. The system of claim 1, wherein the processor configured to define the respective time relationship includes being configured to define the respective time relationship between the clock of the receiver and the system time based on a known distance between the WLAN signal source and the receiver.
14. A system for locating a wireless station in communication with a wireless local area network (WLAN) comprising:
a plurality of wireless mobile devices each forming a WLAN signal source that transmits RF signals;
a plurality of cells defining a WLAN and each having a receiver forming an access point in the WLAN and configured to communicate with WLAN signal sources, wherein at least one of the WLAN signal sources is positioned at a known location, and wherein each of the receivers is configured to:
receive an RF signal from the at least one WLAN signal source positioned at the known location, and
generate, and transmit to a processor, a time-of-arrival measurement for the RF signal relative to a clock of the receiver;
wherein the clocks of the of receivers are unsynchronized; and
the processor configured to:
receive the time-of-arrival measurements from the receivers, and
for each receiver, define a respective time relationship between the clock of the receiver and a system time based on the received time-of-arrival measurement from the receiver.
15. A system according to claim 14, and further comprising a tag transmitter positioned at a signal source.
16. A system according to claim 15, wherein each tag transmitter transmits an RF signal having data identifying an object to which the tag transmitter is associated.
17. A system according to claim 15, wherein each tag transmitter includes a circuit for transmitting a pseudo-random spread spectrum RF signal from signal sources.
18. A system according to claim 15, and further comprising a tag transmitter embedded at a receiver and operative as a WLAN beacon.
19. A system according to claim 14, wherein said processor is operative for determining clock timing relationships for clocks based on one of at least propagation or processing delays in the receivers for synchronizing receiver performance.
20. A system according to claim 14, wherein said processor is operative for processing first-to-arrive signals at each of the receivers.
21. A method for locating a signal source in a wireless local area network (WLAN), the method comprising:
propagating a wireless radio frequency (RF) signal from a WLAN signal source at a known location to a plurality of receivers; and
at each receiver, generating time-of-arrival measurements of the RF signal relative to a clock of the receiver, wherein the clocks of the receivers are unsynchronized;
at each receiver, transmitting the time-of-arrival measurements of the RF signal relative to the clock of the receiver to a processor;
receiving the time-of-arrival measurements at the processor; and
defining a respective time relationship between the clock of each receiver with a system time based on the time-of-arrival measurements.
22. A method according to claim 21, further comprising transmitting RF signals from tag transmitters positioned at the WLAN signal sources at known and unknown locations.
23. A method according to claim 21, further comprising receiving the RF signal within receivers as access points of the WLAN.
24. A method according to claim 21, further comprising propagating RF signals from a plurality of WLAN signal sources at fixed, known locations.
25. A method according to claim 21, further comprising propagating an RF signal from a tag transmitter embedded at a receiver and operative as a WLAN beacon.
26. A method according to claim 21, further comprising determining clock timing relationships for clocks based on one of at least propagation or processing delays in the receivers for synchronizing receiver performance.
27. A method according to claim 21, further comprising maintaining a model of timing relationships of clocks at the receivers.
28. A method according to claim 21, further comprising transmitting an RF signal from at least one tag transmitter having data identifying the object to which the tag is associated.
29. A method according to claim 21, further comprising transmitting a pseudo random spread spectrum RF signal from WLAN signal sources.
30. A method according to claim 21, further comprising processing first-to-arrive signals at each receiver.
31. A method according to claim 21, further comprising forming a tracking loop to track clock relationships that occur naturally over time.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. An optical reader comprising:
a portable housing;
a first imaging module having a first imaging axis;
a second imaging module having a second imaging axis, wherein said first and second imaging modules are disposed so that said first and second imaging axes converge toward one another;
wherein each of said first and second imaging modules include an image sensor having an array of photosensitive elements, a support assembly, and at least one illumination LED;
a control circuit in communication with each of said first and second imaging modules;
wherein said first and second imaging modules are encapsulated in said portable gun style housing, and
wherein said control circuit is programmed, in response to receipt of a trigger signal to:
(a) capture a first frame of image data via actuation of said illumination LED and said image sensor of said first imaging module;
(b) determine whether said first frame of image data includes decodable indicia;
(c) automatically subjects to a decode attempt a second frame of image data if said determination step (b) indicates that decodable indicia is not or is likely not represented in said first frame, wherein said second frame of image data is captured via actuation of said at least one LED of said second imaging module and said image sensor of said first imaging module, wherein no illumination LED of said first imaging module is actuated when said second frame of image data is captured.
2. The reader of claim 1, wherein said control circuit in determining whether decodable indicia is represented in said first frame of image data attempts to decode decodable indicia represented in said first frame of image data.
3. The reader of claim 1, wherein said control circuit captures said second frame of image data contemporaneously while capturing said first frame of image data.
4. The reader of claim 1, wherein said control circuit in determining whether decodable indicia is represented in said first frame of image data preliminarily evaluates image data of said first frame without attempting to decode decodable indicia represented therein.
5. The reader of claim 1, wherein said control circuit in preliminarily evaluating said image data evaluates said image data to determine whether a saturation condition is present.
6. The reader of claim 1, wherein said first imaging module is a 1D imaging module and wherein said second imaging module is a 2D imaging module.
7. The reader of claim 1, wherein said first and second imaging modules are configured to have first and second best focus distances, wherein, said first best focus distance is at least 1 inch apart from said second best focus distance.
8. The reader of claim 1, wherein said trigger signal is an automatically generated trigger signal generated by decodable indicia being moved in a field of view of said reader.
9. The reader of claim 1, further comprising a trigger, wherein said trigger signal is generated when said trigger is pulled.
10. The reader of claim 1, wherein said first portable housing is a gun-style housing.
11. The optical reader of claim 1, wherein said first and second imaging modules are configured to have first and second fixed best focus distances, and wherein said first fixed best focus distance is at least one inch apart from said second fixed best focus distance.
12. The optical reader of claim 1, wherein said control circuit further in response to a receipt of a trigger signal, disables all LEDs of said first imaging module during a frame exposure period for said second frame of image data.
13. A method for reducing specular reflection read errors in an optical reader that is responsive to a trigger signal, said method comprising the steps of:
(a) disposing in a common housing first and second electro-optical imaging assemblies in spaced apart relation, each of said first and second electro-optical imaging assemblies having a solid state area image sensor comprising a plurality of rows and plurality of columns of photosensitive picture elements, each electro-optical imaging assembly further having an illumination assembly that projects an illumination pattern which spans a two dimensional area,
(b) actuating said trigger to initiate a bar code read session, said bar code read session comprising the steps of
(i) capturing a first frame of image data including a plurality of pixel values, said first frame of image data being captured via actuation of said solid state area image sensor of said first electro-optical imaging assembly and said illumination assembly of said first electro-optical imaging assembly;
(ii) capturing a second frame of image data including a plurality of pixel values, said second frame of image data being captured via actuation of said solid state image sensor of said first electro-optical imaging assembly and said illumination assembly of said second electro-optical imaging assembly, wherein said illumination assembly of said first electro-optical assembly is controlled so that said illumination assembly of said first imaging assembly is disabled during an exposure period for said second frame of image data;
(iii) attempting to decode a decodable indicia represented in said first frame of image data captured in step (i);
(iv) attempting to decode a decodable indicia represented in said second frame of image data captured in step (ii); and
(v) outputting a decoded message if one of said decoding steps (iii) or (iv) is successful.
14. The method of claim 13, wherein said first frame and said second frame of image data each includes a plurality of gray scale pixel values.
15. The method of claim 13, wherein said disposing step includes the step of disposing said electro-optical assemblies in vertical orientation relative to one another.
16. The method of claim 13, wherein said disposing step includes the step of disposing said electro-optical assemblies in horizontal orientation relative to one another.
17. The method of claim 13, wherein said disposing step includes the step of disposing said first and second electro-optical imaging assemblies in a common hand held housing.
18. The method of claim 13, wherein said disposing step includes the step of disposing said first and second electro-optical assemblies in such relation that imaging axes of said first and second electro-optical assemblies diverge.
19. The method of claim 13, wherein said disposing step includes the step of disposing said first and second electro-optical assemblies in such relation that imaging axes of said first and second electro-optical assemblies converge.
20. The method of claim 13, wherein said disposing step includes the step of disposing said first and second electro-optical assemblies in such relation that imaging axes of said first and second electro-optical assemblies are substantially parallel.
21. The method of claim 13, further including the step of configuring said fist and second electro-optical assemblies to have first and second respective fixed best focus distances that are at least one inch apart.
22. A bar code reading device configured for reduction of specular reflection read errors, said bar code reader comprising:
(a) a first electro-optical assembly having a first solid state image sensor and a first illumination assembly;
(b) a second electro-optical assembly having a second solid state image sensor and a second illumination assembly, said second electro-optical assembly being spaced apart from said first electro-optical assembly;
(c) wherein said first and second electro-optical assemblies each has a fixed best focus position, and wherein a best focus position of said first electro-optical assembly differs from a best focus position of said second electro-optical assembly by at least 1 inch;
(d) a control circuit coupled to both of said first electro-optical assembly and said second electro-optical assembly,
(e) wherein said control circuit while actuating said first illumination assembly to project an area illumination pattern captures a first frame of image data via actuation of said first image sensor;
(f) wherein said control circuit while actuating said second illumination assembly to project an illumination pattern captures a second frame of image data via actuation of said first image sensor;
(g) wherein said control circuit during an exposure period for said second frame of image data, disables said first illumination assembly so that light from said first illumination assembly does not affect amplitudes of pixel values that make up said second frame of image data; and
(h) wherein said control circuit attempts to decode decodable indicia represented by at least one of said first frame or said second frame of image data.
23. The bar code reading device of claim 22, further comprising a hand held housing supporting said first and second electro-optical assemblies.
24. The bar code reading device of claim 22, wherein said control circuit is configured to preliminarily evaluate said first frame of image data in order to determine whether to attempt to decode said second frame of image data.
25. The bar code reading device of claim 22, wherein said bar code reading device is configured so that said control circuit operates in accordance with elements (e), (f), (g), and (h) when receiving a trigger actuation signal.
26. The bar code reading device of claim 22, further comprising a trigger, wherein said bar code reading device is configured so that said control circuit operates in accordance with elements (e), (f), (g), and (h) when said trigger is actuated.
27. The bar code reading device of claim 22, further comprising a hand held housing, wherein said first and second electro-optical assemblies are disposed vertically relative to one another within said hand held housing.
28. The bar code reading device of claim 22, further comprising a hand held housing, wherein said first and second electro-optical assemblies are disposed horizontally relative to one another within said hand held housing.
29. The bar code reading device of claim 22, wherein said first and second electro-optical assemblies include first and second imaging axes, and wherein said first and second electro-optical assemblies are disposed so that said first and second imaging axes diverge.
30. The bar code reading claim 22, wherein said first first and second electro-optical assemblies include first and second imaging axes, and wherein said first and second electro-optical assemblies are disposed so that said first and second imaging axes converge.
31. The bar code reading device of claim 22, wherein said first and second electro-optical assemblies include first and second imaging axes, and wherein said first and second electro-optical assemblies are disposed so that said first and second imaging axes are substantially parallel to one another.
32. A data collection device comprising:
(a) a housing;
(b) a first imaging module disposed in said housing comprising a first solid state image sensor and at least one illumination LED;
(c) a second imaging module also disposed in said housing spaced apart from said first imaging module and including a second solid state image sensor, said second imaging module also including at least one illumination LED;
(d) a trigger;
(e) a control circuit in communication with each of said first and second imaging modules, wherein said control circuit is configured to capture image data either by actuation of said first image sensor or by actuation of said second image sensor;
(f) wherein at least one of said first solid state image sensor or said second solid state image sensor is an area solid state image sensor having a plurality of rows, and a plurality of columns, of photosensitive picture elements;
(g) wherein said control circuit, in response to an actuation of said trigger captures a first frame of image data during a first frame capture period, said first frame of image data being captured via actuation of said first solid state image sensor and said at least one illumination LED;
(h) wherein said control circuit further in response to said trigger being actuated captures a second frame of image data, said second frame of image data being captured via actuation of said first image sensor and said at least one illumination LED of said second imaging module, wherein said control circuit controls said at least one LED of said first imaging module so that amplitudes of pixel values of said second frame of image data are not affected by said at least one illumination LED of said first imaging module; and
(i) wherein said control circuit further in response to said trigger being actuated attempts to decode decodable indicia represented in at least one of said first or second frames of image data.
33. The data collection device of claim 32, wherein each of said first and second imaging modules includes a plurality of LEDs.
34. The data collection device of claim 32, wherein each of said first and second imaging modules further includes an aiming pattern generator.
35. The data collection device of claim 32, wherein each of said first and second imaging modules projects an illumination pattern that spans a two dimensional area.
36. The data collection device of claim 32, wherein each of said first and second imaging modules projects an illumination pattern that spans a two dimensional area that encompasses a field of view of its respective imaging module.
37. The data collection device of claim 32, wherein each of said first and second imaging modules have best focus distances that are fixed and not equal to one another.
38. The data collection device of claim 32, wherein said control circuit is configured to preliminarily evaluate said first frame of image data in order to determine whether to attempt to decode said second frame of image data.
39. The data collection device of claim 32, wherein said first and second imaging modules are disposed vertically relative to one another within said housing.
40. The data collection device of claim 32, wherein said first and second imaging modules are disposed horizontally relative to one another within said housing.
41. The data collection device of claim 32, wherein said first and second imaging modules include first and second imaging axes, and wherein said first and second modules are disposed so that said first and second imaging axes diverge.
42. The data collection device of claim 32, wherein said first and second imaging modules include first and second imaging axes, and wherein said first and second modules are disposed so that said first and second imaging axes converge.
43. The data collection device of claim 32, wherein said first and second imaging modules include first and second imaging axes, and wherein said first and second imaging modules are disposed so that said first and second imaging axes are substantially parallel to one another.
44. A data collection device comprising:
(a) a housing;
(b) a first imaging module disposed in said housing comprising a first solid state image sensor and an illumination assembly including light diffusing optics and at least one illumination light source;
(c) a second imaging module also disposed in said housing adjacent relative to said first imaging module and including a second solid state image sensor, said second imaging module also comprising an illumination assembly including light diffusing optics and at least one illumination light source;
(d) a control circuit in communication with each of said first and second imaging modules, wherein said control circuit is configured to capture image data either via actuation of said first image sensor or via actuation of said second image sensor;
(e) wherein at least one of said first solid state image sensor and said second solid state image sensor is an area solid state image sensor having an plurality of rows, and a plurality of columns, of photosensitive picture elements;
(f) wherein said control circuit, in response to receipt of a trigger signal captures a frame of image data, said frame of image data being captured via actuation of said first solid state image sensor and said at least one illumination light source of said second imaging module, wherein said control circuit controls said at least one light source of said first imaging module so that image signals processed to develop said frame of image data are not affected by said at least one illumination light source of said first imaging module; and
(g) wherein said control circuit further in response to receipt of said trigger signal attempts to decode decodable indicia represented in said frame of image data.
45. The data collection device of claim 44, wherein each of said first and second imaging modules includes a plurality of LEDs.
46. The data collection device of claim 44, wherein each of said first and second imaging modules further including an aiming pattern generator.
47. The data collection device of claim 44, wherein each of said first and second imaging modules projects an illumination pattern that spans a two dimensional area.
48. The data collection device of claim 44, wherein each of said first and second imaging modules projects an illumination pattern that spans a two dimensional area that encompasses a field of view of its respective imaging module.
49. The data collection device of claim 44, wherein each of said first and second imaging modules have best focus distances that are fixed and not equal to one another.
50. The data collection device of claim 44, wherein said control circuit is configured to preliminarily evaluate said first frame of image data in order to determine whether to attempt to decode said second frame of image data.
51. The data collection device of claim 44, wherein said first and second imaging modules are disposed vertically relative to one another within said housing.
52. The data collection device of claim 44, wherein said first and second imaging modules are disposed horizontally relative to one another within said housing.
53. The data collection device of claim 44, wherein said first and second imaging modules include first and second imaging axes, and wherein said first and second imaging modules are disposed so that said first and second imaging axes diverge.
54. The data collection device of claim 44, wherein said first and second imaging modules include first and second imaging axes, and wherein said first and second imaging modules are disposed so that said first and second imaging axes converge.
55. The data collection device of claim 44, wherein said first and second imaging modules include first and second imaging axes, and wherein said first and second imaging modules are disposed so that said first and second imaging axes are substantially parallel to one another.
56. The data collection device of claim 44, wherein said first and second imaging modules are spaced apart.
57. The data collection device of claim 44, wherein said data collection device includes a manual trigger, and wherein said device is configured so that said control circuit receives said trigger signal when said manual trigger is actuated.
58. The data collection device of claim 44, wherein said data collection device is configured so that said data collection device receives said trigger signal automatically in response to an object being presented to said device.
59. The data collection device of claim 44, wherein said data collection device is configured so that said data collection device receives said trigger signal automatically in response to a decodable indicia being presented to a field of view of said device.
60. The data collection device of claim 44, wherein said data collection device is a fixed position presentation device.
61. The data collection device of claim 44, wherein said data collection device is a fixed position presentation device, and wherein said data collection device is configured so that said data collection device receives said trigger signal automatically in response to an object being presented to said device.
62. The data collection device of claim 44, wherein said housing is a hand held housing.
63. The data collection device of claim 44, wherein said first solid state image sensor is a dimensional solid state image sensor and said second solid state image sensor is an area solid state image sensor.
64. The data collection device of claim 44, wherein said first solid state image sensor is a one dimensional solid state image sensor and said second solid state image sensor is a one dimensional solid state image sensor.
65. The data collection device of claim 44, wherein at least one of said first and second imaging modules are modularly installed self contained units that are assembled into packaged form prior to being disposed in said housing.