System and method for illuminating a target of a barcode reader
A code reader may include a light source configured to illuminate a target area in which items are to be located for reading machine-readable indicia associated with the items, an image sensor configured to capture an image of the target area, an illumination drive circuit in electrical communication with the light source, and an image capture circuit. The image capture circuit may be configured to (i) enable and disable the image sensor to capture an image of the target area during the high illumination and a portion(s) of the low illumination of the target area, and (ii) read an image captured by the image sensor. The illumination drive signals may cause the illumination drive circuit to generate a high illumination drive signal to cause the light source to produce a high illumination, and generate a low illumination drive current to cause said light source to produce a low illumination.
1. A code reader, comprising:
a light source configured to illuminate a target area in which items are to be located for reading machine-readable indicia associated with the items;
an image sensor configured to capture an image of the target area;
an illumination drive circuit in electrical communication with the light source; and
an image capture circuit configured to:
generate illumination control signals that cause the illumination drive circuit to:
generate an illumination drive signal from a single illumination pulse, the illumination drive signal including:
a high illumination drive current signal portion of the illumination drive signal to cause the light source to produce a high illumination; and
a low illumination drive current signal portion of the illumination drive signal to cause the light source to produce a low illumination, the high and low illumination drive current signal portions being continuous with one another;
enable and disable the image sensor to capture an image of the target area during the high illumination and at least a portion of the low illumination of the target area; and
read an image captured by the image sensor.
2. The code reader according to claim 1 , wherein the image sensor is at least one of a global shutter complementary metal-oxide-semiconductor (CMOS) sensor and a charged couple device (CCD) sensor.
3. The code reader according to claim 1 , further comprising a processing unit in electrical communication with the image sensor, the processing unit configured to:
identify that an item inclusive of a machine-readable indicia is in the target area by image processing the image, the machine-readable indicia representative of a code associated with the item; and
decode the code of the machine-readable indicia.
4. The code reader according to claim 1 , further comprising:
a transimpedance amplifier circuit in electrical communication with the image capture circuit; and
a light sensing device in electrical communication with the transimpedance amplifier circuit, the light sensing device configured to generate a return signal representative of reflected light in response to the light source illuminating the target area.
5. The code reader according to claim 4 , wherein the transimpedance amplifier circuit is configured to extract a signal out of the return signal of the light sensing device to identify when an item is in the target area.
6. The code reader according to claim 4 , wherein the light sensing device is a photodiode.
7. The code reader according to claim 4 , wherein the reflected light includes:
a first portion associated with light reflected in response to the high illumination;
a second portion associated with light reflected in response to the low illumination; and
a third portion associated with ambient light of the target area.
8. The code reader according to claim 4 , wherein the return signal is indicative of objects being in the target area, the return signal being processed by the image capture circuit to adjust a shutter of the image sensor.
9. The code reader according to claim 8 , wherein the image capture circuit is configured to continuously process return signals during a reading process.
10. The code reader according to claim 4 , wherein the image capture circuit is configured to execute an algorithm to determine whether the return signal is representative of reflected high illumination or low illumination.
11. The code reader according to claim 10 , wherein the algorithm is further configured to determine at least one of:
(i) a most probable distance of an item from the code reader;
(ii) a most probable movement direction and speed of the item with respect of the reader;
(iii) a most probable size of the item;
(iv) a most probable light reflecting capability of the item; and
(v) ambient light amplitude modulation, if present, caused by oscillating artificial light sources.
12. The code reader according to claim 1 , wherein the light source is a light-emitting diode (LED) chain.
13. The code reader according to claim 1 , wherein the low illumination drive current signal is applied to the light source to generate an illumination signal that is less than, at a peak, about 20 percent of an illumination signal generated by the light source in response to the high illumination drive current signal.
14. The code reader according to claim 13 , wherein the illumination drive circuit includes an energy storage component that, when discharged, generates the high illumination drive current signal, and when discharged and less than charged, is configured to output the low illumination drive current signal.
15. The code reader according to claim 1 ,
wherein the illumination drive circuit includes an energy storage component that produces electrical current for use in generating the illumination drive signal with the high and low illumination drive current signal portions, and
wherein, after the energy storage component is discharged to produce a light strobe with the high illumination, the illumination drive circuit further being configured to:
limit an electrical current signal in producing the low level illumination; and
apply a remainder of the electrical current signal to charge the energy storage component.
16. The code reader according to claim 15 ,
wherein the illumination drive circuit includes an energy storage component; and
wherein the illumination drive circuit is further configured to seamlessly alternate between generating the high illumination drive current signal and low illumination drive current signal so as to continuously illuminate the target area of the code reader.
17. The code reader according to claim 1 , wherein the image capture circuit is further configured to generate a frame synchronization signal that is periodic and indicates a frame rate of the image sensor.
18. The code reader according to claim 1 , wherein the image capture circuit defines an image sensor exposure time that spans across the high illumination drive current signal and a portion of the low illumination drive signal portions.
19. The code reader according to claim 18 , wherein the image capture circuit further defines an illumination time that spans across the high illumination drive current signal and the low illumination drive signal portions.
20. The code reader according to claim 18 , wherein the illumination control signals are further configured to cause the illumination drive circuit to generate the illumination drive signal with an additional drive signal portion within an image frame, and wherein the image capture circuit further defines an illumination time that spans across the high illumination drive current signal portion, the low illumination drive signal portion, and the additional drive signal portion within an image frame.