Telephoto lens for compact long range barcode reader
An imaging engine including a telephoto lens for compact long range barcode readers is disclosed herein. An example imaging engine includes an imaging sensor and a telephoto lens assembly. The example telephoto lens assembly includes a first lens, disposed along an optical axis; a second lens, disposed along the optical axis to correct for pupil aberrations of the image projected after a fourth lens onto the imaging sensor; a third lens, disposed along the optical axis to correct for chromatic aberration of the image projected after the fourth lens onto the imaging sensor; and the fourth lens, disposed along the optical axis to correct for optical field curvature of the image projected after the fourth lens onto the imaging sensor.
1. An imaging engine for decoding barcodes, the imaging engine comprising an imager and a telephoto lens assembly for long range imaging of a barcode via the imaging engine, the telephoto lens assembly including:
a first lens, disposed along an optical axis to receive light from an object of interest;
a second lens, disposed along the optical axis to receive light from the first lens and further to correct for pupil aberration of the image projected after a fourth lens onto the imager;
a third lens, disposed along the optical axis to receive light from the second lens and further to correct for chromatic aberration of the image projected after the fourth lens onto the imager, wherein the chromatic aberration is introduced by the first lens; and
the fourth lens, disposed along the optical axis to receive light from the third lens and further to correct for optical field curvature of the image projected after the fourth lens onto the imager.
2. The imaging engine of claim 1 , wherein the first lens and the third lens are singlet glass lenses and the second lens and the fourth lens are singlet plastic lenses.
3. The imaging engine of claim 2 , wherein the first lens is formed of a Crown type glass having positive optical power, and wherein the third lens is formed of a Flint type glass having negative optical power.
4. The imaging engine of claim 2 , wherein the second lens is a Flint type plastic lens, the fourth lens is a Crown type plastic lens, and the second lens and the fourth lens are aspheric lenses, further wherein the second lens has a first aspheric surface along the optical axis and a second aspheric surface opposite the first aspheric surface disposed along the optical axis, and further wherein the fourth lens has a first aspheric surface along the optical axis and a second aspheric surface opposite the first aspheric surface disposed along the optical axis.
5. The imaging engine of claim 1 , wherein the telephoto lens assembly further comprises an aperture stop disposed along the optical axis and between the first lens and the second lens.
6. The imaging engine of claim 1 , wherein the telephoto lens assembly further comprises a light collecting aperture disposed along the optical axis of at least 1.5 millimeters.
7. The imaging engine of claim 1 , wherein the telephoto lens assembly has an effective focal length (EFL) of at least 11 millimeters.
8. The imaging engine of claim 1 , wherein total length from the first lens to the imager is less than or equal to 11 millimeters, and further wherein each of the first lens, the second lens, the third lens, and the fourth lens has a central thickness of at least 1 millimeter.
9. The imaging engine of claim 1 , wherein the telephoto lens assembly is mounted on a robotic arm with multiple degrees of freedom.
10. The imaging engine of claim 1 , wherein the telephoto lens assembly is configured so as to avoid contact between the fourth lens and the imager.
11. An imaging engine for decoding barcodes, the imaging engine comprising an imager and a telephoto lens assembly for long range imaging of a barcode via the imaging engine, the telephoto lens assembly including:
a first lens, disposed along an optical axis to receive light from an object of interest;
a second lens, disposed along the optical axis to receive light from the first lens and further to correct for pupil aberrations of the image projected after a fourth lens onto the imager;
a third lens, disposed along the optical axis to receive light from the second lens and further to correct for chromatic aberration of the image projected after the fourth lens onto the imager, wherein the chromatic aberration is introduced by the first lens; and
the fourth lens, disposed along the optical axis to receive light from the third lens and further to correct for optical field curvature of the image projected after the fourth lens onto the imager;
wherein no elements that modify the light wavefront are disposed between any of the first lens and the second lens, the second lens and the third lens, or the third lens and the fourth lens.
12. The imaging engine of claim 11 , wherein the first lens and the third lens are singlet glass lenses and the second lens and the fourth lens are singlet plastic lenses.
13. The imaging engine of claim 12 , wherein the first lens is formed of a Crown type glass having positive optical power, and wherein the third lens is formed of a Flint type glass having negative optical power.
14. The imaging engine of claim 12 , wherein the second lens is a Flint type plastic lens, the fourth lens is a Crown type plastic lens, and the second lens and the fourth lens are aspheric lenses, further wherein the second lens has a first aspheric surface along the optical axis and a second aspheric surface opposite the first aspheric surface disposed along the optical axis, and further wherein the fourth lens has a first aspheric surface along the optical axis and a second aspheric surface opposite the first aspheric surface disposed along the optical axis.
15. The imaging engine of claim 11 , wherein the telephoto lens assembly further comprises an aperture stop disposed along the optical axis and between the first lens and the second lens.
16. The imaging engine of claim 11 , wherein the telephoto lens assembly further comprises a light collecting aperture disposed along the optical axis of at least 1.5 millimeters.
17. The imaging engine of claim 11 , wherein the telephoto lens assembly has an effective focal length (EFL) of at least 11 millimeters.
18. The imaging engine of claim 11 , wherein total length from the first lens to the imager is less than or equal to 11 millimeters, and further wherein each of the first lens, the second lens, the third lens, and the fourth lens has a central thickness of at least 1 millimeter.
19. The imaging engine of claim 11 , wherein the telephoto lens assembly is mounted on a robotic arm with multiple degrees of freedom.
20. The imaging engine of claim 11 , wherein the telephoto lens assembly is configured so as to avoid contact between the fourth lens and the imager.