Device for localizing an object in a turbid medium using a modulated light source

• US 5,807,262 A
• Filed: 12/19/1996
• Issued: 09/15/1998
• Est. Priority Date: 12/22/1995
• Status: Expired due to Fees

• Current Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Original Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Inventors: Papaioannou, Dimitrios, t Hooft, Gert W.
• Primary Examiner(s): Kamm, William E.
• Assistant Examiner(s): MANTIS MERCADER, ELENI M
• Application Number:
  US08/770,031
• Time in Patent Office: 635 Days
• Field of Search: 128/664, 128/665, 128/633, 250/341.1, 250/339.12, 356/345, 356/39, 356/40, 356/41, 600/473, 600/476, 600/310
• US Class Current: 600/473
• CPC Class Codes: A61B 5/0091 for mammography
• CPC Class Codes: A61B 5/4312 Breast evaluation or disorder diagnosis A61B5/0091 takes precedence

Abstract

A device (700) for localizing an object (726) in a turbid medium (710) includes one light source (722) and two detectors (723,724), being symmetrically situated relatively to the light source (722), around a turbid medium (710). By applying a pulse modulated light source an optimal frequency could be determined to perform measurement at optimal sensitivity of the system. To enable a fast scanning system that could be used in for example mammography, a plurality of light sources (1209) and plurality of detectors (1201 to 1208) could be used. A processing system (105) selects then repetitively one light source (1209) and a different detector pairs, that are symmetrically situated relatively towards the light source (1209). Another embodiment that could be used in the mammography includes rotating mirrors (1303,1309) to scan a measuring space (1304) adapted to contains an object (1305), for example a human breast. The detector used in this embodiment includes a streak camera (1313). A lens (1308) and one of the rotating mirrors (1309) images two exit locations (1306,1307) of the measuring space (1304) that are symmetrically situated toward an entrance location (1303) of the measuring space on the entrance slit (1312) of the streak camera (1313). The output-image (1315) of the streak camera (1313) is imaged by an image pick-up device (1316) and processed by a processing system (1318) to obtain an image of the object in the measuring space (1304). A monitor (1319) displays the obtained image.

Claims

1. A device for localizing an object in a turbid medium, comprising:

a first light source for irradiating the turbid medium by means of modulated light having a modulation in the form of pulses having a duration and a repetition frequency,

detector for generating a detector signal from modulated light emanating from the turbid medium, and

a processing unit for determining optical parameters of the turbid medium from the detector signal,

wherein the duration and repetition frequency of said pulses is chosen to introduce into the turbid medium a superposition of photon density waves with different frequencies including the repetition frequency and higher harmonics thereof.

2. A device as claimed in claim 1, further comprising a second light source for irradiating the turbid medium by means of modulated light, the modulation of the modulated light of the second light source being the same as but shifted in time with respect to the modulation of the modulated light of the first light source.

3. A device as claimed in claim 2, further comprising means for scanning a measuring space capable of containing the turbid medium.

4. A device as claimed in claim 1, further comprising means for scanning a measuring space capable of containing the turbid medium.

15. A device as claimed in claim 4, wherein the plurality of detectors are arranged on a single straight line.

16. A device as claimed in claim 15, wherein the detectors are coupled to the entrance slit of a streak camera.

5. A device for localizing an object in a turbid medium comprising:

a light source for irradiating the turbid medium by means of modulated light having a modulation frequency,

a first detector and a second detector for generating a first detector signal and a second detector signal, respectively, in response to modulated light emanating from the turbid medium, and

processing means for determining optical parameters of the turbid medium, said processing means being arranged to determine the amplitude and the phase of a difference signal of the first and second detector signals.

6. A device as claimed in claim 5, further comprising a plurality of detectors, including said first and second detectors, which are arranged in one plane, said first and second detectors being selected from the plurality of detectors by the processing unit.

7. A device as claimed in claim 6, wherein the plurality of detectors comprises four detectors arranged in a square, the light source is arranged at substantially equal distances from the detectors, and a measuring space capable of containing the turbid medium is situated between the light source and the detectors.

8. A device as claimed in claim 7, further comprising means for scanning a measuring space capable of containing the turbid medium.

9. A device as claimed in claim 7, wherein the detectors are coupled to the entrance slit of a streak camera.

10. A device as claimed in claim 6, wherein the plurality of detectors are arranged according to a regular polygon which encloses a measuring space in which the turbid medium can be placed, the light source being arranged substantially halfway between two adjacent detectors, and the processing unit is arranged to select two detectors which are symmetrically situated relative to the light source.

11. A device as claimed in claim 10, further comprising means for scanning a measuring space capable of containing the turbid medium.

12. A device as claimed in claim 10, wherein the device comprises a plurality of equidistant light sources, including said first light source which are arranged substantially halfway between two adjacent detectors on the polygon, the processing unit being arranged to execute the following steps repetitively:

selecting one of the light sources,

selecting for every selected light source, several times, different detector pairs which are symmetrically situated relative to the selected light source, and

measuring amplitude and/or phase from a difference signal of detector signals from the selected detector pairs.

13. A device as claimed in claim 12, wherein the detectors are coupled to the entrance slit of a streak camera.

14. A device as claimed in claim 10, wherein the detectors are coupled to the entrance slit of a streak camera.

17. A device as claimed in claim 6, wherein the detectors are coupled to the entrance slit of a streak camera.

18. A device as claimed in claim 6, further comprising means for scanning a measuring space capable of containing the turbid medium.

19. A device as claimed in claim 5, wherein the detectors are coupled to the entrance slit of a streak camera.

20. A device as claimed in claim 5, further comprising means for scanning a measuring space capable of containing the turbid medium.