Optical arrangement for use in imaging engines and devices using imaging engines
At least some embodiments of the present invention generally relate to the field of optics, and more specifically, to compact optical arrangements for use in imaging engines likes the ones used in handheld barcode readers. In an embodiment, an imaging engine having a field of view (FOV) includes an imaging sensor and an optical lens configured to (i) fold the FOV once between the imaging sensor and an exit window of the imaging engine and/or the window of a barcode reader within which the imaging engine may be implemented, and (ii) correct for field curvature.
1. An imaging engine for use in a barcode reader, comprising:
an optical lens arrangement;
a printed circuit board (PCB) positioned relative to the optical lens arrangement; and
an imaging sensor positioned on the PCB, the imaging sensor having a plurality of photosensitive elements forming a substantially flat surface,
wherein:
the optical lens arrangement includes a first lens-sub-arrangement and a second lens-sub-arrangement positioned relative to the first lens-sub-arrangement,
the first lens-sub-arrangement includes an optical axis along which there is at least some degree of rotational symmetry in the first lens-sub-arrangement, the first lens-sub-arrangement having a first end and a second end opposite the first end,
the second lens-sub-arrangement includes a fold lens, the fold lens having (i) a first side positioned proximate the second end of the first lens-sub-arrangement, the first side configured to refract light incoming along the optical axis into the fold lens along a first path, (ii) a second side configured to reflect the light via total internal reflection (TIR) and redirect the light along a second path, and (iii) a third side positioned within the second path, the third side configured to refract the light directed along the second path out of the fold lens and direct the light toward the imaging sensor, and
at least one of the first side of the fold lens, the second side of the fold lens, and the third side of the fold lens is configured to correct for a field curvature.
2. The imaging engine of claim 1 , wherein the first lens-sub-arrangement incudes a first lens having a positive optical power, a third lens having a positive optical power, and a second lens having a negative optical power and interposed between the first lens and the third lens.
3. The imaging engine of claim 2 , wherein:
the first lens has a refractive index between 1.45 and 1.8;
the second lens has a refractive index between 1.45 and 1.8; and
the third lens has a refractive index between 1.45 and 1.9.
4. The imaging engine of claim 2 , wherein:
the first lens has an Abbe value between 46 and 65;
the second lens has an Abbe value between 20 and 40; and
the third lens has an Abbe value between 50 and 70.
5. The imaging engine of claim 1 , wherein the second lens-sub-arrangement further includes a focusing lens configured to be movable along a focusing axis normal to the substantially flat surface.
6. The imaging engine of claim 1 , wherein the fold lens has a prism shape.
7. The imaging engine of claim 1 , wherein at least a portion of the first lens-sub-arrangement is moveable along the optical axis to focus an image to be captured by the imaging sensor.
8. The imaging engine of claim 1 , wherein each of the first side of the fold lens and the third side of the fold lens is curved, and wherein the second side of the of the fold lens is one of flat or curved.
9. The imaging engine of claim 1 , wherein the first lens-sub-arrangement and the second lens-sub-arrangement are fixedly secured relative to each other such that no component of first lens-sub-arrangement is moveable relative to any component of the second lens-sub-arrangement.
10. An imaging engine for use in a barcode reader, comprising:
an optical lens arrangement;
a printed circuit board (PCB) positioned relative to the optical lens arrangement; and
an imaging sensor positioned on the PCB, the imaging sensor having a plurality of photosensitive elements forming a substantially flat surface, the substantially flat surface defining a first plane,
wherein:
the optical lens arrangement includes a first lens-sub-arrangement and a second lens-sub-arrangement positioned relative to the first lens-sub-arrangement,
the first lens-sub-arrangement includes an optical axis along which there is at least some degree of rotational symmetry in the first lens-sub-arrangement, the first lens-sub-arrangement having a first end and a second end opposite the first end,
the second lens-sub-arrangement includes a fold lens, the fold lens having (i) a first side positioned proximate the second end of the first lens-sub-arrangement, the first side configured to refract light incoming along the optical axis into the fold lens along a first path, (ii) a second side configured to reflect the light via total internal reflection (TIR) and redirect the light along a second path, and (iii) a third side positioned within the second path, the third side configured to refract the light directed along the second path out of the fold lens and direct the light toward the imaging sensor,
the optical axis is substantially parallel with the first plane.
11. The imaging engine of claim 10 , wherein the first lens-sub-arrangement incudes a first lens having a positive optical power, a third lens having a positive optical power, and a second lens having a negative optical power and interposed between the first lens and the third lens.
12. The imaging engine of claim 10 , wherein at least one of the first side of the fold lens, the second side of the fold lens, and the third side of the fold lens is configured to correct for a field curvature.
13. The imaging engine of claim 11 , wherein:
the first lens has a refractive index between 1.45 and 1.8, and an Abbe value between 46 and 65;
the second lens has a refractive index between 1.45 and 1.8, and an Abbe value between 20 and 40; and
the third lens has a refractive index between 1.45 and 1.9, and an Abbe value between 50 and 70.
14. The imaging engine of claim 11 , wherein:
the fold lens has a refractive index between 1.45 and 1.8, and an Abbe value between 20 and 65.
15. The imaging engine of claim 10 , wherein the second lens-sub-arrangement further includes a focusing lens configured to be movable along a focusing axis normal to the substantially flat surface.
16. The imaging engine of claim 10 , wherein the fold lens has a prism shape.
17. The imaging engine of claim 10 , wherein at least a portion of the first lens-sub-arrangement is moveable along the optical axis to focus an image to be captured by the imaging sensor.
18. The imaging engine of claim 10 , wherein each of the first side of the fold lens and the third side of the fold lens is curved, and wherein the second side of the of the fold lens is flat.
19. The imaging engine of claim 10 , wherein the first lens-sub-arrangement and the second lens-sub-arrangement are fixedly secured relative to each other such that no component of first lens-sub-arrangement is moveable relative to any component of the second lens-sub-arrangement.
20. The imaging engine of claim 10 , wherein the second path of the light is angled between 45 and 135 degrees relative to the optical axis.
21. A barcode reader comprising:
a housing; and
an imaging engine secured within the housing, the imaging engine including:
an optical lens arrangement;
a printed circuit board (PCB) positioned relative to the optical lens arrangement; and
an imaging sensor positioned on the PCB, the imaging sensor having a plurality of photosensitive elements forming a substantially flat surface, the substantially flat surface defining a first plane,
wherein:
the optical lens arrangement includes a first lens-sub-arrangement and a second lens-sub-arrangement positioned relative to the first lens-sub-arrangement,
the first lens-sub-arrangement includes an optical axis along which there is at least some degree of rotational symmetry in the first lens-sub-arrangement, the first lens-sub-arrangement having a first end and a second end opposite the first end,
the second lens-sub-arrangement includes a fold lens, the fold lens having (i) a first side positioned proximate the second end of the first lens-sub-arrangement, the first side configured to refract light incoming along the optical axis into the fold lens along a first path, (ii) a second side configured to reflect the light via total internal reflection (TIR) and redirect the light along a second path, and (iii) a third side positioned within the second path, the third side configured to refract the light directed along the second path out of the fold lens and direct the light toward the imaging sensor, and
the second path of the light is angled between 45 and 135 degrees relative to the optical axis.
22. The barcode reader of claim 21 , wherein the first lens-sub-arrangement incudes a first lens having a positive optical power, a third lens having a positive optical power, and a second lens having a negative optical power and interposed between the first lens and the third lens.
23. The barcode reader of claim 21 , wherein the second lens-sub-arrangement further includes a focusing lens configured to be movable along a focusing axis normal to the substantially flat surface.
24. The barcode reader of claim 21 , wherein the fold lens has a prism shape.
25. The barcode reader of claim 21 , wherein at least a portion of the first lens-sub-arrangement is moveable along the optical axis to focus an image to be captured by the imaging sensor.
26. The barcode reader of claim 21 , wherein each of the first side of the fold lens and the third side of the fold lens is curved, and wherein the second side of the of the fold lens is flat.
27. The barcode reader of claim 21 , wherein the first lens-sub-arrangement and the second lens-sub-arrangement are fixedly secured relative to each other such that no component of first lens-sub-arrangement is moveable relative to any component of the second lens-sub-arrangement.
28. The barcode reader of claim 21 , wherein the optical axis is substantially parallel with the first plane.
29. The barcode reader of claim 21 , wherein at least one of the first side of the fold lens, the second side of the fold lens, and the third side of the fold lens is configured to correct for a field curvature.
30. An imaging engine for use in a barcode reader, comprising:
an optical lens arrangement;
a printed circuit board (PCB) positioned relative to the optical lens arrangement; and
an imaging sensor positioned on the PCB, the imaging sensor having a plurality of photosensitive elements forming a substantially flat surface,
wherein:
the optical lens arrangement includes a first lens-sub-arrangement and a second lens-sub-arrangement positioned relative to the first lens-sub-arrangement,
the first lens-sub-arrangement includes an optical axis along which there is at least some degree of rotational symmetry in the first lens-sub-arrangement, the first lens-sub-arrangement having a first end and a second end opposite the first end,
the second lens-sub-arrangement includes a fold lens, the fold lens having (i) a first side positioned proximate the second end of the first lens-sub-arrangement, the first side configured to refract light incoming along the optical axis into the fold lens along a first path, (ii) a second side configured to reflect the light via total internal reflection (TIR) and redirect the light along a second path, and (iii) a third side positioned within the second path, the third side configured to refract the light directed along the second path out of the fold lens and direct the light toward the imaging sensor, and
the second lens-sub-arrangement is configured to correct for a field curvature.
31. The imaging engine of claim 30 , wherein the PCB includes decoding circuitry configured to decode data encoded in an image of a barcode captured by the imaging sensor.