JPH0797077B2 - Slab type optical waveguide for optical measurement - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a slab type optical waveguide for optical measurement, and more specifically, it introduces excitation light into the optical waveguide to produce an optical waveguide with an evanescent wave component. The present invention relates to a slab type optical waveguide for measuring the optical characteristics of a measurement target existing near the surface.

<Prior art> Conventionally, a slab type optical waveguide is used, and only the labeled fluorescent substance existing in the vicinity of the surface of the optical waveguide is excited by the evanescent wave component slightly exuding from the optical waveguide, and based on the excited fluorescence. An optical measurement method for measuring the presence or absence of immunity and the degree of immunity is known, and in order to embody this method, as shown in FIG. 6, a test solution is placed on one surface of the slab type optical waveguide (91). The housing chamber (92) is integrally formed, and the excitation light emitted from a laser light source (not shown) is introduced into the optical waveguide (91) through the dichroic mirror (93) to guide the fluorescence emitted from the marker fluorescent body. It is proposed that the light is emitted through a waveguide (91), reflected by a dichroic mirror (93), and then made incident on a detector (95) through an optical filter (94).

When the above configuration is adopted, the antibody (96) is immobilized on the surface of the optical waveguide (91) in advance, and this antibody (96) is allowed to receive the antigen (97) in the test liquid, and further The fluorescently labeled antibody (98) labeled with a fluorescent substance is received by the antigen (97). That is, the amount of the fluorescently labeled antibody (98) received will be determined based on the amount of the antigen (97) in the test solution. Then, only the labeled fluorescent substance (98a) of the fluorescent labeled antibody (98) received by the evanescent wave component obtained by introducing the excitation light into the optical waveguide (91) is excited to emit fluorescent light. Therefore, the intensity of the emitted fluorescence is proportional to the amount of antigen (97) in the test solution. Also,
This fluorescence will be guided through the optical waveguide (91).

Therefore, only the fluorescence that has been guided through the optical waveguide (91) is reflected by the dichroic mirror (93), and the excitation light component is blocked by the optical filter (94) so that the detector (9
By injecting into 5), the presence or absence of immunity and the degree of immunity can be measured.

<Problems to be Solved by the Invention> Since the fluorescence immunoassay device shown in FIG. 6 is adapted to excite the fluorescence only on one surface of the optical waveguide (91), the intensity of the excited fluorescence. Therefore, there is a problem that the accuracy of the immunoassay cannot be increased so much.

This point will be described in more detail. Since the slab type optical waveguide is easy to injection-mold, it is almost always obtained by injection-molding plastic. In this case, since plastic exhibits fluorescence to some extent and Raman scattering, when performing immunoassay using a plastic slab-type optical waveguide, it is caused by the fluorescence and Raman scattering. The resulting noise will be superimposed on the fluorescent light, which will reduce the measurement accuracy. In particular, when the amount of the antigen is very small, the influence of noise becomes extremely large, and the immunoassay cannot be performed at all.

In order to alleviate such a problem, the inventors of the present invention considered fixing the antibody (96) to the entire surface of the slab type optical waveguide in advance and contacting the entire surface of the slab type optical waveguide with the test solution. . If such a configuration is adopted, only the fluorescence excited by the evanescent wave component increases, so the influence of the noise can be reduced to that extent, and the measurement accuracy can be improved. In particular,
For the upper and lower surfaces (upper surface and lower surface in the figure) of the slab type optical waveguide, the excitation light is introduced at an angle close to the critical angle by a prism for introducing the excitation light, and the optical path length is made sufficiently long to provide sufficient phosphor excitation. Can be achieved. However, the excitation light can be introduced into the side surface of the slab type optical waveguide only at an angle determined by the F value of the projection lens. Therefore, if the excitation light is to be introduced at an angle close to the critical angle, a projection lens having an F value corresponding to the critical angle may be used.
When an optical waveguide with a refractive index of 1.49 is used and the surface of the optical waveguide is in contact with water (refractive index is approximately 1.33), the F value is generally
It can be lowered to less than 0.5, but it limits the usable projection lens. On the other hand, when a projection lens having a large F value is used, it is difficult to make the introduction angle of the excitation light to the side surface of the optical waveguide close to the critical angle, and as a result, the excitation of the fluorescent body on the side surface is difficult. It cannot be performed sufficiently and the measurement accuracy cannot be sufficiently enhanced.

Although only the case of performing the fluorescent immunoassay has been described above, the same inconvenience also occurs in the case of measuring an enzyme reaction or the like accompanied by color development.

<Objects of the Invention> The present invention has been made in view of the above problems,
An object of the present invention is to provide a novel slab type optical waveguide for optical measurement, which can bring the incident angle of excitation light close to a critical angle even when a projection lens having an F value that is not too small is used.

<Means for Solving the Problems> A slab type optical waveguide for optical measurement of the present invention for achieving the above object is a pair of surfaces of the slab type optical waveguide which are opposed to each other. At least one of the narrow surfaces in the plane is a tapered surface in which the distance between the pair of narrow surfaces gradually decreases toward the excitation light emitting side.

<Operation> In the case of the slab type optical waveguide for optical measurement having the above configuration, the optical waveguide main body having a rectangular cross section is housed in the casing containing the test liquid, and the excitation light is introduced into the optical waveguide. When measuring the change state of the optical characteristics of the measurement object that exists near the surface of the optical waveguide due to the evanescent wave component, the introduction angle of the excitation light to the wide surface of the optical waveguide main body can be easily determined by the critical angle. The angle can be close to. The introduction angle of the excitation light to the surface with a narrow width is initially considerably larger than the critical angle, but since it propagates inside the optical waveguide body while being totally reflected from the tapered surface, the width is increased at each total reflection. The angle of incidence on a narrow surface approaches the critical angle. Therefore, the optical path length of the excitation light that propagates while being reflected by the narrow surface becomes long. However, the optical characteristics include fluorescence, light absorption, and scattering.

The same effect can be achieved when only one of the narrow surfaces is a tapered surface or when both surfaces are tapered surfaces.

<Example> Hereinafter, detailed description will be given with reference to the accompanying drawings illustrating an example.

FIG. 1 is a perspective view showing an embodiment of the slab type optical waveguide of the present invention, in which a wedge-shaped prism (2) for introducing excitation light is provided at one end of an optical waveguide main body (1) having a rectangular cross section. It is integrally molded. The prism (2) has a casing (5) that engages in a surplus portion that does not optically affect the measurement and surrounds the entire range of the optical waveguide body (1). The antibody (4) is immobilized on the entire surface of the optical waveguide body (1).

FIG. 2 is a sectional view taken along line II-II of FIG. 1, in which the upper surface (1a) and the lower surface (1b) (wide surface) of the optical waveguide main body (1) are parallel. FIG. 3 is a sectional view taken along the line III-III in FIG. 1, in which both side surfaces (1c) (1d) (the narrow surface) of the optical waveguide main body (1) are non-parallel. Specifically, one side surface (1c) should be parallel to the optical axis (BS) of the optical waveguide body (1), and the other side surface (1d) should be close to the side surface (1c) on the emission end side. It is inclined by this predetermined angle (α) with respect to the optical axis (BS). Hereinafter, this angle α is referred to as a taper angle (α).

When carrying out an immunoassay using the slab type optical waveguide having the above structure, first, a test solution containing the antigen (4a) in the casing (5) and a fluorescently labeled antibody () labeled with a fluorescent substance (4c) ( 4b) is housed. In this state, the antigen (4a) is received by the antibody (4) fixed to the optical waveguide body (1),
Furthermore, the fluorescently labeled antibody (4b) is accepted by the antigen (4a). Therefore, the amount of the antigen (4a) in the test solution, that is, the amount of the fluorescence-labeled antibody (4b) corresponding to immunity, should be the optical waveguide body (1).
Constrained near the surface of.

Further, since the excitation light is guided to the prism (2) by a projection lens (not shown), in the plane shown in FIG. 2, the optical waveguide has an incident angle (θ1) determined based on the shape of the prism (2). It is incident on the upper surface (1a) and the lower surface (1b) of the main body (1). Since the shape of the prism (2) can be freely determined, the incident angle (θ
If the shape is determined so that 1) is almost equal to the critical angle, the optical path length of the excitation light can be lengthened and the amount of the labeled fluorescent substance (4c) that can be excited can be increased (2 in Fig. 2). (See dotted line). Further, in the plane shown in FIG. 3, it is impossible to control the incident angle by the prism (2),
The incident angle determined based on the F value of the projection lens is the incident angle (θ2) with respect to the side surface (1c) of the optical waveguide main body (1) as it is.
become. However, since the side surface (1d) is inclined by the taper angle (α) with respect to the optical axis (BS), even if the initial incident angle on the side surface (1c) is (θ2), the side surface (1c) ) And incident on the side surface (1d), the incident angle is (θ2
-Α), and when the light enters the side surface (1c) next, the incident angle becomes (θ2-2α), and thereafter, each time it is similarly reflected, the incident angle becomes smaller by α and approaches the critical angle. (See the solid line in FIG. 4). Therefore, the optical path length of the excitation light can be made longer than in the case where the taper angle α is not provided and the incident angle (θ2) does not change at all (see the chain double-dashed line in FIG. 4).

As a result, the number of excited labeled fluorescent substances (4c) increases, so that the intensity of the obtained fluorescent light also increases, and the optical waveguide body (1)
Since the influence of noise caused by itself can be reduced, the accuracy of immunoassay can be improved.

Further, in this embodiment, the optical waveguide main body (1) is tapered as a whole, so that the injection molding becomes easy.

<Embodiment 2> FIG. 5 is a horizontal cross-sectional view showing another embodiment. The difference from the above embodiment is that both side surfaces (1c) and (1d) should be close to the other side surface on the emission end side. It is only a point that is inclined by a predetermined angle (α) with respect to the optical axis (BS).

Therefore, in the case of this embodiment, the incident angle is decreased by α in the first reflection, and thereafter, the incident angle is decreased by 2α, which is closer to the critical angle than in the above-mentioned embodiment. The optical path length can be further increased, and the accuracy of immunoassay can be further improved.

However, in any of the examples, since the length of the optical waveguide body (1) is predetermined based on the widths of the upper surface (1a) and the lower surface (1b), the excitation light is transmitted through the optical waveguide body (1). It is sufficient to set the taper angle α so that the incident angle does not exceed the critical angle even when propagating to the terminal end.

In any of the above examples, instead of immobilizing the antibody (3) on the optical waveguide body (1), an antigen or a hapten (ha) is used.
pten) can be fixed.

Further, in the above-mentioned both examples, the fluorescent immunoassay was described as an example. However, for example, an enzyme or the like was immobilized instead of the antibody (4), and the excitation light caused by an enzymatic reaction or the like accompanied by color development was detected. It can be applied not only to measurement based on a decrease in the amount of emitted light, but also to measurement of optical characteristics such as fluorescence, absorption and scattering.
Further, it is possible to integrally form a prism also at the emission end of the optical waveguide main body (1), and it is possible to integrally form prisms of different shapes (for example, asymmetric wedge prisms). Various design changes can be made within the scope of the present invention.

<Effects of the Invention> As described above, according to the present invention, the incident angle of excitation light with respect to a narrow surface can be reduced each time reflection is performed to approach the critical angle, and the optical path length as a whole can be lengthened. There is a unique effect that the intensity of the optical measurement signal can be increased and the measurement accuracy can be improved.

[Brief description of drawings]

1 is a perspective view showing an embodiment of the immunoassay measuring apparatus of the present invention, FIG. 2 is a sectional view taken along line II-II of FIG. 1, and FIG. 3 is a sectional view taken along line III-III of FIG. FIG. 4 is a schematic view showing the propagation characteristics of the excitation light in the plane shown in FIG. 3, FIG. 5 is a horizontal cross-sectional view showing another embodiment, and FIG. 6 is a schematic view showing a conventional example. (1) …… Main body of optical waveguide, (1c) (1d) …… Side, (2) …… Prism, (5) …… Casing

Claims (1)

[Claims] 1. A cross-sectional shape of a plane perpendicular to the optical axis of the excitation light is rectangular, the excitation light is introduced so as to propagate while being totally reflected, and an evanescent wave component caused by the total reflection of the excitation light causes the light to be generated near the surface. A slab-type optical waveguide for measuring a change state of optical characteristics of an existing measurement target, the pair of surfaces (1c) (1d) facing each other of the slab-type optical waveguide, At least one of the surfaces (1c) and (1d) having a narrow width in the plane is a tapered surface in which the distance between the pair of narrow surfaces (1c) and (1d) gradually decreases toward the excitation light emitting side. Slab type optical waveguide for optical measurement.