Method for detecting forensic evidence

• US 7,267,457 B2
• Filed: 04/22/2005
• Issued: 09/11/2007
• Est. Priority Date: 09/24/1999
• Status: Expired due to Term

• Current Assignee: CAO Group, Inc.
• Original Assignee: CAO Group, Inc.
• Inventors: Cao, Densen, Li, Hongyan, Ostler, Calvin D., Lin, Zhaohui
• Primary Examiner(s): Ward; John Anthony
• Application Number:
  US11/112,720
• Publication Number:
  US 20060245176A1
• Time in Patent Office: 872 Days
• Field of Search: 362/231, 362/234, 362/249, 362/253, 362/276, 362/294, 362/295, 362/800, 362/804, 433/29, 250/459.1, 250/461.1, 250/461.2, 356/317, 356/378, 356/318
• US Class Current: 362/294
• CPC Class Codes: F21V 29/54 using thermoelectric means, e.g. Peltier elements
• CPC Class Codes: F21V 29/67 characterised by the arrangement of fans
• CPC Class Codes: F21V 29/70 characterised by passive heat-dissipating elements, e.g. heat-sinks
• CPC Class Codes: F21V 29/83 the elements having apertures, ducts or channels, e.g. heat radiation holes
• CPC Class Codes: G01J 3/10 Arrangements of light sources specially adapted for spectrometry or colorimetry
• CPC Class Codes: G01N 21/255 Details, e.g. use of specially adapted sources, lighting or optical systems
• CPC Class Codes: G01N 21/29 using visual detection G01N21/31 takes precedence
• CPC Class Codes: G01N 2201/0221 Portable; cableless; compact; hand-held

Abstract

A method for detecting forensic evidence. The method includes use of a forensic light that may utilize 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 beutilized 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:

a. accessing a semiconductor forensic light that has

i. a handle,

ii. a plurality of light heads attachable to and detachable from said handle,

iii. each of said light heads being capable of emitting a light of different wavelength than another of said heads,

iv. 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

v. 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

vi. 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,

b. determining the type of forensic evidence sought to be discovered,

c. selecting a light head capable of emitting the light required for the type of forensic evidence sought to be discovered and attaching said head to the semiconductor forensic light,

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

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

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

g. 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. 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,

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

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

d. 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, SiOn, Sic, AISi, AISiC, 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, AI2O3, 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;

a. injecting electrons into said active layer,

b. permitting said active layer to emit photons, and

c. 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:

a. determining the type of forensic evidence sought to be discovered,

b. accessing a semiconductor forensic light capable of emitting the light required for the type of forensic evidence sought to be discovered and that has

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

ii. 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

iii. 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,

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

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

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

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

16. 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;

a. injecting electrons into said active layer,

b. permitting said active layer to emit photons, and

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

17. A method as recited in claim 16 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.

18. A method as recited in claim 17 further comprising the step of utilizing a photon multiplier which in turn projects light and an image onto a view screen.