Photoacoustic signal detecting device

Claim 2

A photoacoustic signal detecting device comprising: a light source (21, 81); modulation means (22, 82) for intensity-modulating the light emitted from the light source at a predetermined frequency; focusing means (300; 24; 25; 26; 28; 400, 86; 87; 88; 100), constructed in a confocal optical system, for focusing the light modulated by said modulation means (300, 400) on a sample (170); and light interference detection means (310; 31; 33; 34; 35; 36; 180; 41, 410; 104; 105; 106; 108; 111), constructed in a confocal optical system, for detecting, through light, interference the thermal distortion of the sample created when the light is focused on the sample by said focusing means (300, 400).

Claim 3

A photoacoustic signal detecting device according to claim 1, wherein said focusing means (300, 400) has a pin-hole (25) for removing high order dif­fraction light components (161a, 161b) around the light spot emitted from said light source.

Claim 4

A photoacoustic signal detecting device according to claim 1, wherein said light interference detection means (310, 410) comprises: a detection light source (31) which is used for detecting light interference; and a pin-hole (34) for removing high order diffraction light components (161a, 161b) around the light spot emitted from said detection light source (31).

Claim 5

A photoacoustic signal detecting device according to claim 1, wherein said light interference detection means (310, 410) comprises: a photo-electric converting element (41) for detecting an interference light containing information relative to the thermal distortion in said sample (170); and a pin-hole (40), arranged before said photo-­electric converting element (41), for removing high order diffraction light components (161a, 161b) around the light spot of said interference light.

Claim 6

A photoacoustic signal detecting device according to claim 1, wherein said focusing means (300) comprises: a plurality of lenses (24, 26) in a confocal relation; a pin-hole (25), arranged at the confocal point of said plurality of lenses, for removing high order diffraction light components (161a, 161b) around the light spot of said modulated light; and an objective lens (28) for focusing on said sample the light the high order diffraction light components (161a, 161b) of which has been removed at said pin-hole (25), said light interference detection means (310) comprises: a detection light source (31); a plurality of lenses (33, 35) in a confocal relation; a pin-hole (34), arranged at the confocal point of said plurality of lenses, for removing high order dif­fraction light components around the light spot emitted from said detection light source; a beam splitter (36) for separating the light from said detection light source (31) into two light beams, one of which is used as a reference light and the other of which is focused and reflected on said sample and contains information relative to the thermal dis­tortion of the sample (170) due to photoacoustic effect; a polarizing plate (180) for polarizing these two light beams; and a photo-electric converting element (41) for detecting an interference light of said two light beams which have permeated through said polarizing plate.

Claim 7

A photoacoustic signal detecting device according to claim 1, further comprising an auto-focusing adjusting means (330, 430) which includes two photo-­electric converting elements (45, 48) for detecting the light reflected from said sample and, by comparing the detection currents from said two photo-electric converting elements (45, 48), adjusts the position of said focusing means (300, 400) or said sample (170) so that the diameter of the light spot formed on the sample by said focusing means is always constant.

Claim 8

A photoacoustic signal detecting device according to claim 1, further comprising an auto-focusing adjusting means (330, 430) which comprises: a Z stage (30) for fixing said sample (170), the position of which can be controlled in the vertical direction; a first beam splitter (56, 112) for branching into two light beams the light from said light source (31, 81) which has been focused and reflected on said sample; a second beam splitter (42) for further branch­ing into light beams one light beam from said first beam splitter (56, 112); a first lens (43) for focusing the one beam from said second beam splitter; a first photo-electric converting element (45) which is located behind the rear focal point (Fa) of said first lens; a second lens (46) for focusing the other beam from said second beam splitter (42); a second photo-electric converting element (48) which is located before the rear focal point (Fa) of second lens; and a comparing circuit (54) for comparing the currents detected by said first and second photo-electric converting elements (45, 48) to adjust the position of said focusing means (300) or said sample (170) so that the diameter of the light spot formed on said sample by said focusing means is always constant.

Claim 9

A photoacoustic signal detecting device according to claim 7, further comprising a light source dedicated to auto-focusing which is provided independently from the light source (31, 81) for light interference detection.

Claim 10

A photoacoustic signal detecting device according to claim 1, wherein said light source is a laser.

Claim 11

A photoacoustic signal detecting device according to claim 1, wherein said light source (21, 81) is a mercury lamp.

Claim 12

A photoacoustic signal detecting device according to claim 1, wherein said modulation means is an acoustic-optical modulation element (22).

Claim 13

A photoacoustic signal detecting device according to claim 1, wherein said modulation means modulates the light emitted from said light source (81) and also separates it into a zero order light and a first order diffraction light; pin-holes (87, 105) included in said focusing means removes high order diffraction light components around of the light spots of said zero order light and said first order diffraction light; and said focusing means (100) focuses and irradiates said zero order light on the sample, said zero order light being reflected on the sample and containing information relative to the thermal distortion of the sample created due to photoacoustic effect; and said light interference detection means (310, 410) causes said first diffraction light and said zero order light to interfere to detect a resultant interference light, thereby detecting said thermal distortion of the sample.

Claim 14

A photoacoustic signal detecting device comprising: a light source (81); modulation means (82) for intensity-modulating the light emitted from said light source at a predetermined frequency and separating it into a zero order light and a first order diffraction light; focusing means (400), constructed in a confocal optical system, for focusing said zero order light onto a sample, said zero order light being reflected on the sample and containing information reltive to the thermal distortion in the sample created due to photoacoustic effect; light interference detection means (410), constructed in a confocal optical system, for causing said first order diffraction light and said zero order light to interfere with each other to detect the resultant interference light; and auto-focusing adjusting means (430) for adjusting said focusing means so that said zero order light is focused on said sample.

Claim 15

A photoacoustic signal detecting device comprising: a light source (81); modulation means (82) for intensity-modulating the light emitted from said light source at a predetermined frequency and separating it into a zero order light and a first order diffraction light; focusing means (400), constructed in a confocal optical system, for focusing said zero order light onto a sample, said zero order light being reflected on the sample and containing information reltive to the thermal distortion in the sample created due to photoacoustic effect; light interference detection means (410), constructed in a confocal optical system, for causing said first order diffraction light and said zero order light to interfere with each other to detect the resultant interference light; and auto-focusing adjusting means (430) for adjusting said focusing means so that said zero order light is focused on said sample.

Claim 16

A photoacoustic signal detecting device according to claim 13, wherein said focusing means (400) comprises: a first lens (86) for focusing said zero order light at the rear focal point thereof, a first pin-hole (87) located at said rear focal point of the first lens, a second lens (88) for changing the light having passed through said first pin-hole into a parallel light, and an objective lens (100), in a confocal relation with said second lens, for focusing said zero order light onto the sample; and said light interference detection means (410) comprises: a third lens (104) for focusing said first order diffraction light at the rear focal point thereof, a second pin-hole (105) located at said rear focal point (152) of the third lens (104), a fourth lens (106) for changing the light having passed through said second pin-hole (105) into a parallel light, a polarization plate (108) for polarizing said first order diffraction light having passed through said fourth lens and said zero order light having been reflected on the sample and containing information relative to the thermal distortion in the sample due to photoacoustic effect, and a photo-electric converting element (111) for detecting an interference light of said zero order light and said first order diffraction light which have passed through said polarization plate (108).