Method for detecting forensic evidence

• US 20040119975A1
• Filed: 02/07/2003
• Published: 06/24/2004
• Est. Priority Date: 12/20/2002
• Status: Active Grant

• Current Assignee: CAO Group, Inc.
• Original Assignee: CAO Group, Inc.
• Inventors: Cao, Densen, Li, Hongyan, Ostler, Calvin D., Lin, Zhaohui
• Granted Patent: US 6,954,270 B2
• Time in Patent Office: Days
• US Class Current: 356/318
• CPC Class Codes: G01J 3/10 Arrangements of light sources specially adapted for spectrometry or colorimetry
• CPC Class Codes: G01N 2021/6471 Special filters, filter wheel
• CPC Class Codes: G01N 21/255 Details, e.g. use of specially adapted sources, lighting or optical systems
• CPC Class Codes: G01N 21/64 Fluorescence; Phosphorescence
• CPC Class Codes: G01N 21/6447 by visual observation
• CPC Class Codes: G01N 21/645 Specially adapted constructive features of fluorimeters
• CPC Class Codes: G01N 2201/0221 Portable; cableless; compact; hand-held

Abstract

A semiconductor forensic light is disclosed. The forensic light may use a variety of semiconductor light sources to produce light that contrasts forensic evidence against its background for viewing, photographing and collection. Example semiconductor light sources for the forensic light include light emitting diodes and laser chips. A heat sink, thermoelectric cooler and fan may be included to keep the forensic light cool. A removable light source head may be included on the forensic light to provide for head swapping to give the user access to different wavelengths of light.

Claims

1. A method for detecting forensic evidence comprising:

accessing a semiconductor forensic light that has

a handle,

a plurality of light heads attachable to and detachable from said handle, each of said light heads being capable of emitting a light of different wavelength than another of said heads,

at least one of said light heads including

a semiconductor light emitting device that can emit light of a wavelength useful in detecting forensic evidence, and

a primary heat sink to which said semiconductor light emitting device is affixed, said primary heat sink serving to draw heat away from said semiconductor light emitting device, and

at least one light exit on said light head, said light exit being sized and shaped to permit light to exit said light head for use in detecting forensic evidence,

placing said semiconductor forensic light in a physical location where forensic evidence is expected to be discovered,

actuating a switch on said handle to cause a light beam to be emitted by said semiconductor forensic light,

causing said light beam to shine on an area that may contain forensic evidence,

observing a contrast between forensic evidence in said light beam and the background where it rests.

2. A method as recited in claim 1 further comprising photographing said forensic evidence.

3. A method as recited in claim 1 further comprising collecting said forensic evidence.

4. A method as recited in claim 1 wherein said forensic light further comprises:

a secondary heat sink to which said primary heat sink is affixed, said secondary heat sink serving to dissipate heat produced by said semiconductor light emitting device,

a thermoelectric cooler located on said secondary heat sink, said thermoelectric cooler experiencing a drop in temperature when subjected to a voltage, and

a fan serving to move air past said thermoelectric cooler in order to cool the light source, and

at least one ventilation aperture on said light head for permitting air to enter and exit the light head to facilitating heat dissipation.

5. A method as recited in claim 1 wherein said semiconductor light producing device is an LED module that include the primary heat sink, an LED chip located in a well on the primary heat sink, and a dome over said LED chip, the LED chip including a substrate and epitaxial layers;

and

further comprising the step of supplying electrical power to said epitaxial layers in order to produce said light beam.

6. A method as recited in claim 1 wherein said forensic light further comprises a light reflector in said light head for reflecting light from said light source out of said light head.

7. A method as recited in claim 1 wherein said heat sink includes a material selected from the group consisting of copper, aluminum, silver, magnesium, steel, silicon carbide, boron nitride, tungsten, molybdenum, cobalt, chrome, Si, SiO₂, SiC, AlSi, AlSiC, and diamond.

8. A method as recited in claim 1 wherein said semiconductor light producing device includes epitaxial layers located on a substrate and wherein said substrate is selected from the group consisting of Si, GaAs, GaN, ZnS, ZnSe, InP, Al₂O₃, SiC, GaSb, and InAs.

9. A method as recited in claim 1 wherein said semiconductor light producing device includes epitaxial layers located on a substrate, and at least one of the epitaxial layers is selected from the group consisting of:

a buffer layer to reduce defects in the chip that may arise due to differences in material properties between the epitaxial layers and the substrate,

a contact layer,

a cladding layer serving to confine injected electrons, and

an active layer that emits the light when excited by electrons, the light emitted being useful in forensic detection of evidence;

and further comprising;

injecting electrons into said active layer,

permitting said active layer to emit photons,

permitting said photons to exit said semiconductor forensic light as a light beam.

10. A method as recited in claim 9 wherein light emitted from said semiconductor light producing device is of a wavelength in the range of 200 to 1500 nm.

11. A method as recited in claim 1 wherein said light beam has a color that is selected from the group consisting of blue, green, yellow, red, infrared and ultraviolet.

12. A method as recited in claim 1 wherein said light beam has a wavelength centered around a wavelength selected from the group consisting of 405 nm, 450 nm, 525 nm, 590 nm, and 630 nm.

13. A method as recited in claim 1 wherein said light beam is applied to forensic evidence selected from the group consisting of blood, saliva, other body fluids, hair, flesh, bone fragments, teeth, human skin damage such as bruises, bite marks, cuts, shoe prints, fingerprints, footprints, tire prints, gunpowder residue, bullets and portions thereof, paint, grease, oil, glass fragments, metal rubbings, fibers, dust patterns, alteration of documents, narcotics, and herbal evidence.

14. A method as recited in claim 1 wherein said light beam has an intensity within the range of 1 mW to 9000 mW.

15. A method for detecting forensic evidence comprising:

accessing a semiconductor forensic light that has

a semiconductor light emitting device that can emit light of a wavelength useful in detecting forensic evidence, and

a primary heat sink to which said semiconductor light emitting device is affixed, said primary heat sink serving to draw heat away from said semiconductor light emitting device, and

at least one light exit, said light exit being sized and shaped to permit light to exit said light head for use in detecting forensic evidence,

placing said semiconductor forensic light in a physical location where forensic evidence is expected to be discovered,

actuating a switch to cause a light beam to be emitted by said semiconductor forensic light,

causing said light beam to shine on an area that may contain forensic evidence,

observing a contrast between forensic evidence in said light beam and the background where it rests.

16. A method as recited in claim 15 further comprising photographing said forensic evidence.

17. A method as recited in claim 15 further comprising collecting said forensic evidence.

18. A method as recited in claim 16 wherein said forensic light further comprises:

a secondary heat sink to which said primary heat sink is affixed, said secondary heat sink serving to dissipate heat produced by said semiconductor light emitting device,

a thermoelectric cooler located on said secondary heat sink, said thermoelectric cooler experiencing a drop in temperature when subjected to a voltage, and

a fan serving to move air past said thermoelectric cooler in order to cool the light source, and

at least one ventilation aperture on said light head for permitting air to enter and exit the light head to facilitating heat dissipation.

19. A method as recited in claim 15 wherein said forensic light further comprises:

a secondary heat sink to which said primary heat sink is affixed, said secondary heat sink serving to dissipate heat produced by said semiconductor light emitting device.

20. A method as recited in claim 15 wherein said semiconductor light producing device is an LED module that include the primary heat sink, an LED chip located in a well on the primary heat sink, and a dome over said LED chip, the LED chip including a substrate and epitaxial layers;

and

further comprising the step of supplying electrical power to said epitaxial layers in order to produce said light beam.

21. A method as recited in claim 15 wherein said forensic light further comprises a light reflector in said light head for reflecting light from said light source out of said light head.

22. A method as recited in claim 15 wherein said semiconductor light producing device includes epitaxial layers located on a substrate, and at least one of the epitaxial layers is selected from the group consisting of:

a buffer layer to reduce defects in the chip that may arise due to differences in material properties between the epitaxial layers and the substrate,

a contact layer,

a cladding layer serving to confine injected electrons, and

an active layer that emits the light when excited by electrons, the light emitted being useful in forensic detection of evidence;

and further comprising;

injecting electrons into said active layer,

permitting said active layer to emit photons,

permitting said photons to exit said semiconductor forensic light as a light beam.

23. A method as recited in claim 15 wherein said light beam has a color that is selected from the group consisting of blue, green, yellow, red, infrared and ultraviolet.

24. A method as recited in claim 15 wherein said light beam has a wavelength centered around a wavelength selected from the group consisting of 405 nm, 450 nm, 525 nm, 590 nm, and 630 nm.

25. A method as recited in claim 15 wherein said light beam is applied to forensic evidence selected from the group consisting of blood, saliva, other body fluids, hair, flesh, bone fragments, teeth, human skin damage such as bruises, bite marks, cuts, shoe prints, fingerprints, footprints, tire prints, gunpowder residue, bullets and portions thereof, paint, grease, oil, glass fragments, metal rubbings, fibers, dust patterns, alteration of documents, narcotics, and herbal evidence.

26. A method as recited in claim 15 further comprising the step of utilizing a photon multiplier which in turn projects light and an image onto an view screen.