JPH05333286A - Luminous flux flattening optical system - Google Patents

Abstract

PURPOSE:To provide the luminous flux flattening optical system which can irradiate the cell in the flow cell of a flow sight meter with a laser beam having a narrow width, flat central part and high energy density, can be easily produced and is small in size and low in cost and to enable the formation of the laser beam to a larger shape or smaller shape and further to a square shape. CONSTITUTION:The laser beam is expanded or reduced by a condenser lens 2 or an expanding or reducing lens system and is made incident on a calcite crystal 4 to obtain two parallel luminous fluxes 7 and 8 of the polarization directions orthogonal with each other. These luminous fluxes are superposed on each other on an irradiation surface 6. The four luminous fluxes lining up in one row are obtd. by two sheets of calcite crystal plates and are superposed on the irradiation surface. Two sheets of the calcite crystal plates are relatively rotated, by which a square spot is obtd. The calcite crystals are produced by adhering the crystals to a glass substrate 5 for reinforcement, etc., then polishing the substrate. This luminous flux flattening element is inserted between the condenser lens 2 and the irradiation surface 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for efficiently irradiating cells flowing in a flow cell with a laser beam in a flow cytometer.

[0002]

2. Description of the Related Art Conventional flow cytometers and laser beam machines are required to efficiently collect a laser beam. In the flow cytometer, cells passing through the flow cell are irradiated with a laser beam to measure fluorescence intensity or scattering intensity from the cells for cell analysis. In this case, since the laser beam intensity is generally distributed in a Gaussian shape, there are differences in fluorescence intensity and scattering intensity from the cell when the center of the laser beam passes through the cell and when it is deviated from the center. The laser beam intensity distribution is made as flat as possible.

However, although the signal fluctuation width can be reduced by flattening the laser beam intensity, there is a problem that the signal intensity is lowered on average and the detection sensitivity is lowered. In Japanese Patent Application Laid-Open No. 1-279487, "Flowing Cell Analysis Device" and Japanese Patent Application Laid-Open No. 2-315099, "Particle Analysis Device", laser beams are divided into two or four and the positions are shifted to overlap each other. The flat part of the light flux is enlarged to solve the above problem.

FIG. 2 is a block diagram of an optical system when the above laser beam is divided into two. Linearly polarized laser beam 1
Is rotated in its polarization direction by the half-wave plate 3 and is separated by the Wollaston prism 9 into two light beams 7 and 8 whose positions are slightly apart from each other. And stack them. The Wollaston prism 9 is made of two optically anisotropic crystals with the crystal axis directions orthogonal to each other and the angle of the bonding surface not parallel to the end surface, and the polarization directions of the optical beams 7 and 8 are The light beams are made orthogonal to each other to prevent interference between light beams. The light beams 7 and 8 are separated by a branch angle θ according to the direction of the plane of polarization of the incident light and correspond to an ordinary ray and an extraordinary ray. The energy density distribution of light on the irradiation surface is the sum of two light fluxes.

The thick line in FIG. 3 (B) is the combined intensity distribution of the light beams 7 and 8 on the irradiation surface 6, and it can be seen that the flat portion in the central portion becomes wider and at the same time the energy density increases. On the other hand, when an attempt is made to widen the flat portion by an ordinary optical system, the distribution of the laser light flux becomes as shown in FIG. But,
The Wollaston prism 9 of FIG. 2 is expensive because it is not easy to manufacture, and the optical system becomes long because the condenser lens 2 is inserted between the Wollaston prism 9 and the irradiation surface 6. Further, although it is possible to further flatten the light flux by dividing the light flux into four by using two sets of the Wollaston prisms described above, it is necessary to make an adjustment considering the phase because interference occurs between every other light flux. There was a problem.

Japanese Unexamined Patent Publication No. 59-69728 discloses a method for improving the problem of the Wollaston prism (FIG. 2). That is, a combination of a birefringent crystal plate and a ½ wavelength plate having different thicknesses is irradiated with laser light to divide the emitted light into two, and the above birefringent crystal plate and ½ wavelength plate are combined. A plurality of laser beams are alternately provided to separate the laser light into a plurality of emitted lights to form an elliptical beam having a small ratio of the short axis and the long axis, thereby enhancing the reflection intensity during scanning. ..

[0007]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
The method disclosed in Japanese Patent No. 728 does not disclose a method in which the laser beam is made into a minute spot to make the shape of the elliptical beam more flat and sharp. There is also a problem that the output beam size cannot be freely adjusted by enlarging or reducing the spot size of the laser beam. further,
It was also impossible to arrange the divided laser beams in a rectangular shape or the like other than the above-mentioned one row without mutual interference between the lights. It is an object of the present invention to adjust the size and arrangement of the divided laser beams so that various cells in a flow cell of a flow cytometer can be efficiently irradiated with a laser beam, which is small in size and low in cost. It is to provide a light beam flattening optical system that is easy to manufacture.

[0008]

In order to solve the above-mentioned problems, a collection for reducing or expanding the incident light beam is provided in front of a half-wave plate and an optical crystal having a birefringence such as a calcite (calcite) crystal. Provide an optical lens or a reduction / enlargement optical system. In addition, a plurality of sets of the half-wave plate and the birefringent optical crystal are provided along the optical axis. Also,
A cylindrical lens is used as the condenser lens.

Further, the incident light beam is separated into two by the first half-wave plate and the first birefringent optical crystal, and the second light beam is divided into two.
The second birefringent optical crystal is rotated by 45 ° by a / 2 wavelength plate so that it is separated into four light beams arranged in a line. Further, the second birefringent optical crystal is rotated by 90 ° with respect to the first birefringent optical crystal so as to separate the incident light flux into four rectangular light fluxes. Further, in the flow cytometer device, the incident light flux is applied to the cells through the light flux flattening optical system.

[0010]

The condenser lens or the reduction / enlargement optical system reduces or enlarges the incident light beam and makes it enter the half-wave plate and the birefringent optical crystal. Further, the cylindrical lens changes the spot shape of incident light into a flat shape. Further, the plurality of sets of half-wave plates and the birefringent optical crystal divide the incident light beam into a plurality of beams.

The first 1/2 wavelength plate and the first birefringent optical crystal split the incident light beam into two,
The incident light flux is split into four light fluxes arranged in a row by being rotated by 45 ° by the two-wavelength plate and being incident on the second birefringent optical crystal. Further, by rotating the second birefringent optical crystal by 90 ° with respect to the first birefringent optical crystal, the incident light flux is separated into four rectangular light fluxes. Further, in the flow cytometer device, cells are irradiated with the incident light flux obtained by the light flux flattening optical system.

[0012]

【Example】

[Embodiment 1] FIG. 1 is a block diagram of an embodiment of a light beam flattening optical system according to the present invention. The linearly polarized laser beam 1 is condensed by the condenser lens 2, passes through the half-wave plate 3, and is incident on the calcite (calcite) crystal 4. When the calcite crystal 4 is thin, the calcite crystal 4 is reinforced by the reinforcing optical glass 5, and when the calcite crystal 4 has a sufficient thickness, the reinforcing glass 5 can be omitted.

The laser light beam 1 is separated by a calcite crystal 4 into an extraordinary ray 7 and an ordinary ray 8 whose polarization directions are orthogonal to each other, and each is emitted in parallel to the optical axis. The ordinary ray 8 goes straight through the calcite crystal, and the extraordinary ray 7 is bent about 6 ° with the optical axis in the crystal. The distance d between the extraordinary ray 7 and the ordinary ray 8 is proportional to the thickness t of the calcite crystal and is represented by the equation (1). d = t · tan6 ° (1)

Since the half-wave plate 3 rotates the polarization direction of the incident light beam 1 by 45 °, the polarization directions of the ordinary ray 8 and the extraordinary ray 7 emitted from the calcite crystal 4 are orthogonal to each other and interfere with each other. And the energy intensities of the extraordinary ray 7 and the ordinary ray 8 on the irradiation surface 6 are the same,
As shown in FIG. 3B, the energy density distribution of light on the irradiation surface 6 can be the sum of both light fluxes. In the present invention, since the laser beam 1 is condensed into a fine spot by the condenser lens 2, the extraordinary ray 7 and the ordinary ray 8 are also miniaturized, and the distribution of the elliptical light formed on the irradiation surface 6 is narrow and sharp. Can be The spot sizes of the ordinary ray 7 and the ordinary ray 8 are set by the size of the laser beam 1 and the focal length of the condenser lens 2.

Further, the shape of the above energy density distribution needs to be changed according to the purpose of use. When the central part of the energy density distribution is made as narrow as possible and as flat as possible, each spot size of the ordinary ray 7 and the ordinary ray 8 is made small by the condenser lens 2, and at the same time, the thickness of the calcite crystal 4 is made thin to make the distance d Also try to make it smaller. When the energy density distribution is wide and flat, the spot size of the ordinary ray 7 and the ordinary ray 8 is expanded by the condenser lens 2, and at the same time, the thickness of the calcite crystal 4 is increased to increase the distance d. To do.

The calcite crystal 4 is manufactured by adhering it to the reinforcing optical glass 5 and then polishing it to a predetermined thickness. When the calcite crystal 4 is thin, the reinforcing optical glass 5 reinforces the calcite crystal 4 to facilitate its production. Further, since the half-wave plate 3 and the calcite crystal 4 are incorporated between the condenser lens 2 and the irradiation surface 6, the length in the optical axis direction can be made relatively short and the optical system can be made small. .. Further, since the distance d between the ordinary ray 8 and the extraordinary ray 7 does not depend on the position on the surface of the calcite crystal 4, the position adjustment of the laser beam incident on the calcite crystal 4 is omitted and the assembly adjustment process is simplified. Can be converted.

However, when focusing the condenser lens 2,
The work of adjusting the polarization direction of the / 2 wave plate 3 and the angle of the calcite crystal 4 is necessary. The half-wave plate 3 may be provided in front of the condenser lens 2. As described above, it is possible to provide a compact light beam flattening optical system that is easy to manufacture and adjust, and is inexpensive.

[Embodiment 2] FIG. 4 is a diagram showing the construction of another embodiment of the light beam flattening optical system according to the present invention, in which a wide elliptical light beam can be obtained. In FIG. 4, the focal length of the beam expanding optical system composed of the concave lens 26 and the convex lens 27 is adjusted to expand the size of the optical beam incident on the condenser lens 2.

[Embodiment 3] FIG. 5 is a schematic view of another embodiment of the light beam flattening optical system according to the present invention. In FIG. 5, instead of the condenser lens 2, two cylindrical lenses 10 and 11 are used to separately determine the light flux converging size in the light beam flattening direction and the light beam non-flattening direction. That is, the cylindrical lens 10 determines the light beam width in the light beam flattening direction, and the cylindrical lens 11 determines the light beam width in the direction orthogonal to the light beam flattening direction. If the light flux width in the direction orthogonal to the light beam flattening direction is within the surface of the cylindrical lens 11, the cylindrical lens 11 may be inserted between the calcite crystal 4 and the irradiation surface 6.

[Embodiment 4] FIG. 6 is a constitutional view of another embodiment of the light beam flattening optical system according to the present invention, in which two calcite crystals are used and a half-wave plate 20 is used to form the calcite crystal 4. The ordinary and extraordinary rays from
When rotated by °, the four light beams are condensed on the irradiation surface 6 side by side in one line, so by appropriately selecting the thicknesses of the calcite crystals 4 and 21 and superimposing the separated four light beams, Further excellent light flux flatness characteristics can be obtained. At this time, since the polarization directions of the adjacent light beams are orthogonal to each other, the adjacent light beams do not interfere with each other. Interference occurs because the polarization directions of the other light fluxes are the same, but the intensity is small. Reference numeral 22 is a reinforced optical glass that reinforces the calcite crystal 21.

Further, when the second calcite crystal 21 is rotated by 90 ° with respect to the first calcite crystal 4, it is 4
The four light beams can be arranged in a quadrangle, and the four light beams can be overlapped to obtain a square spot.
Such a square spot is particularly effective when a large cell is uniformly irradiated with the laser beam.

The present invention can also be applied to optical materials having the same properties as the above calcite crystals. Further, the application range of the present invention can be applied not only to flow cytometers but also to optical systems such as laser beam machines and laser printers that require flattening of light flux.

[0023]

According to the present invention, there is provided a light beam flattening optical system having the following effects, for example, the efficiency of collecting a laser light beam in a flow cytometer and its uniformity are improved to detect a fluorescence or scattering detection signal from a cell. Fluctuation can be reduced and detection sensitivity can be improved. (1) A laser beam is condensed into a small amount by a condenser lens or a reduction optical system, and is separated by a half-wave plate and a calcite crystal, so that a light spot with a narrow width and a flat center portion and a high energy density is formed. Obtainable.

(2) The calcite crystal having a small thickness for generating the light spot can be easily manufactured by polishing the calcite crystal previously bonded to the reinforcing glass substrate. (3) The shape of the light spot can be freely enlarged or reduced by using the enlargement / reduction optical system portion.

(4) Since the shape of the light spot does not depend on the optical axis position of the calcite crystal plane, the adjustment of the optical axis position can be omitted. (5) Since the light flux flattening element has a simple structure, it is easy to manufacture, and since the light flux flattening element can be inserted between the condenser lens and the irradiation surface, the entire optical system can be downsized. (6) The spot shape can be made square by relatively rotating the two calcite crystal plates.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a light beam flattening optical system according to the present invention.

FIG. 2 is a configuration diagram of a light beam flattening optical system using a conventional Wollaston prism.

FIG. 3 is an intensity distribution diagram of a light beam that flattens a light beam.

FIG. 4 is a configuration diagram of another light beam flattening optical system according to the present invention.

FIG. 5 is a configuration diagram of a light beam flattening optical system of the present invention using a cylindrical lens.

FIG. 6 is a configuration diagram of a light beam flattening optical system of the present invention using four light beams.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Laser beam, 2 ... Condensing lens, 3, 20 ... 1/2 wavelength plate, 4, 21 ... Calcite crystal, 5, 22 ... Reinforcing glass plate, 6 ... Irradiation surface, 7 ... Extraordinary ray, 8 ... Rays, 9 ... Wollaston prism, 10, 11 ... Cylindrical lens.

Claims (6)

[Claims] 1. A light beam flattening optic which separates an incident light beam into an ordinary ray and an extraordinary ray by a half-wave plate and an optical crystal having a birefringence such as a calcite (calcite) crystal and superimposes them on an irradiation surface. In the system, a light flux flattening optical system characterized in that a condenser lens or a reduction / enlargement optical system for reducing or expanding the incident light beam is provided in front of the optical crystal. 2. The light beam flattening optical system according to claim 1, wherein a plurality of sets of the half-wave plate and the birefringent optical crystal are provided along the optical axis. 3. A light beam flattening optical system according to claim 1, wherein the condenser lens is a cylindrical lens. 4. The incident light flux according to claim 2,
Is divided into two light fluxes by the ½ wavelength plate and the first birefringent optical crystal, rotated by 45 ° by the second ½ wavelength plate, and arranged in line by the second birefringent optical crystal. A light beam flattening optical system characterized in that the light beam is split into four light beams. 5. The optical system according to claim 2, wherein the second birefringent optical crystal is rotated by 90 ° with respect to the first birefringent optical crystal, and the incident light flux is arranged in a square shape. A light beam flattening optical system characterized by being divided into two light beams. 6. A flow cytometer device characterized in that an incident light beam is applied to cells through the light beam flattening optical system according to any one of claims 1 to 5.