Spot light generating device, optical information detecting device and microscope

Abstract

The spot light generation device pertaining to the present invention comprises an optical modulator having a modulation surface configured so as to be capable of amplitude modulation of incident laser light, and a condensing element for condensing laser light emitted from the optical modulator. In the modulation surface, as regions for transmitting or reflecting the incident laser light, there are formed a pair of arcuate regions divided by a region in a prescribed angle range based on positions mutually symmetrical about the center of the modulation surface in an annular region having a prescribed width and a prescribed radius from the center.

Description

[Technical Field]

[0001] The present invention relates to a light spot generating device, an optical information detecting device, and a microscope. [Background technology]

[0002] In devices such as scanning laser microscopes, image recording devices, and processing devices, at least incident light is irradiated onto an object to be irradiated, and if necessary, emitted light from the object to be irradiated is detected. Information about the optical properties of the object to be irradiated is obtained from the detected emitted light. The laser light (incident light) irradiated onto the object to be irradiated may be a needle spot light, which is wider in a direction parallel to the optical axis than in a direction intersecting the optical axis. For example, in a scanning laser microscope disclosed in Patent Document 1, a needle spot light is irradiated onto the object to be irradiated as laser light. For each irradiation, response light emitted from the object to be irradiated is converted into an Airy beam that propagates while shifting at least one-dimensionally on a detection plane intersecting the optical axis. This allows optical properties of the object to be detected at different positions along the longitudinal direction of the needle spot light as images converted into an Airy beam.

[0003] In devices such as scanning laser microscopes, side lobes that can occur around the peak of the needle spot light where the light intensity is highest at the intersection with the optical axis can cause the laser light irradiation area on the target object to extend beyond the specified area, or the response light from the side lobes can also be superimposed on the detection surface, resulting in reduced performance of the device as a whole. For this reason, for example, Patent Document 2 discloses an image recording device equipped with a filter with nonlinear optical properties that transmits the peak of the needle spot light and absorbs the side lobes. Patent Document 3 discloses a laser beam shaping device equipped with an axicon lens that converts incident laser light into needle spot light and an annular phase element positioned on the incident side of the axicon lens. Patent Document 4 discloses a beam shaping module equipped with a lens that focuses light of multiple wavelengths and an aperture positioned on the focal plane of the lens and having a specific aperture structure. Patent Document 5 discloses an optical device equipped with a multiple beam generating means that generates a multiple beam with reduced side lobes by overlapping multiple Bessel beams so that their side lobes cancel each other out. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2017 / 213171 [Patent Document 2] Japanese Patent Application Publication No. 2002-120396 [Patent Document 3] Japanese Patent Application Publication No. 2017-142402 [Patent Document 4] Japan Special Publication No. 2018-501513 [Patent Document 5] Japanese Patent Publication No. 2011-170052 Summary of the Invention [Problem to be solved by the invention]

[0005] As mentioned above, the suppression of the side lobe portion of needle spot light has been studied in devices such as scanning laser microscopes. However, for example, in the image recording device disclosed in Patent Document 1, it is difficult to precisely control the nonlinear optical characteristics of the filter, resulting in a lack of flexibility in suppressing the side lobe portion. Furthermore, in the laser beam shaping device disclosed in Patent Document 2, the design and fabrication of an annular phase element requires a great deal of time and effort. The beam shaping module disclosed in Patent Document 3 includes a lens for collimating the laser light, a lens for focusing the light, and an aperture mask that forms an aperture structure, resulting in a large number of optical components for suppressing the side lobe portion, making it difficult to reduce the space required for the optical system. Furthermore, the beam generation means of the optical device disclosed in Patent Document 4 requires complex adjustments such as adjusting the intensity of multiple overlapping Bessel beams. Another method for suppressing side lobe portions that is different from the above-mentioned methods is the use of two-photon absorption. However, in the method of suppressing the side lobe portion of needle spot light using two-photon absorption, the handling of the light source emitting ultrashort pulsed laser light is somewhat difficult, and the wavelength range of the needle spot light determined by the light source is narrow. Furthermore, microscopes using two-photon excitation and ultrashort pulses are expensive due to their complex structure. For these reasons, there has been a demand for a spot light generating device that can use a laser light source that emits a continuous wave (CW) and that has a simple configuration and allows for highly flexible suppression of side lobe components. Such a spot light generating device can provide an inexpensive device.

[0006] The present invention provides a spot light generating device that can suppress the side lobe portion of needle spot light with a simple configuration and high degree of freedom in a specified direction, for example, in which multiple detectors are arranged, and an optical information detection device and microscope that are equipped with the spot light generating device. [Means for solving the problem]

[0007] A spot light generation device according to the present disclosure includes an optical modulator having a modulation surface configured to enable spatial amplitude modulation of incident laser light, a focusing element that focuses the laser light emitted from the optical modulator, and a relay lens that is disposed between the optical modulator and the focusing element on an optical axis of the laser light and image-transfers a pupil plane of the focusing element to the modulation surface. The modulation surface includes a pair of arc-shaped regions that transmit or reflect the incident laser light, the arc-shaped regions being separated by a region within a predetermined angle range from positions symmetrical to each other about the center within an annular region having a predetermined radius and a predetermined width from a center, and the laser light is amplitude-modulated and phase-modulated by the arc-shaped regions and the region within the predetermined angle range, and the transmittance or reflectance of the laser light in each of the arc-shaped regions and the region within the predetermined angle range continuously changes in the circumferential direction. In the spot light generating device according to the present disclosure, the modulation surface has a pair of arc-shaped regions separated by regions within a predetermined angle range based on positions symmetrical to each other about the center in an annular region having a predetermined radius and a predetermined width from the center as regions that transmit or reflect the incident laser light, and the laser light is amplitude-modulated and phase-modulated, and the transmittance or reflectance of the laser light in each of the arc-shaped regions and the region within the predetermined angle range varies discontinuously in the circumferential direction, and the predetermined angle is 20° to 60°.

[0008] A spot light generation device according to the present disclosure includes a radial polarization element that converts the polarization of incident laser light into radial polarization, an optical modulator having a modulation surface configured to be able to phase-modulate the laser light emitted from the radial polarization element, a focusing element that focuses the laser light emitted from the optical modulator, and a relay lens that is disposed between the optical modulator and the focusing element on the optical axis of the laser light and that transfers an image of a pupil plane of the focusing element to the modulation surface. The modulation surface forms an annular region having a predetermined radius and a predetermined width from the center as a region that transmits or reflects the incident laser light, and the phases on both sides of a boundary line that passes through the center and positions symmetrical to each other across the center in the annular region are inverted from each other.

[0009] The optical information detection device according to the present disclosure includes a light source that emits laser light, the above-described spot light generation device, a shift spot light conversion device that, when a needle spot light irradiation area formed by focusing the laser light with the focusing element of the spot light generation device and having a size in a direction parallel to the optical axis greater than a size in a direction intersecting the optical axis of the irradiation area when the sample is irradiated within the needle spot light irradiation area, separates the exit light emitted from multiple different positions in the direction parallel to the optical axis of the irradiation area into predetermined directions on a light receiving surface intersecting the optical axis of the exit light, and an optical information acquisition device that has a photodetector that receives the exit light separated in the predetermined direction on the light receiving surface by the shift spot light conversion device, and acquires optical information of the exit position of the exit light. The detection surface of the photodetector extends in a direction optically equivalent to a direction connecting the center of the modulation surface and positions symmetrical to each other across the center.

[0010] A microscope according to the present disclosure includes the optical information detection device described above, and an image information creation device that creates image information about the sample based on the optical information acquired from the emitted light by the optical information acquisition device. [Effects of the Invention]

[0011] According to the present invention, the side lobe portion of the needle spot light can be suppressed in a predetermined direction with a simple configuration and a high degree of freedom. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic diagram of a detection optical system including a spot light generating device according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a schematic diagram for explaining a modulation pattern in the light modulator of the spot light generating device shown in FIG. [Figure 3] FIG. 3 is a schematic diagram of a main part of a spot light generating device according to a second embodiment of the present invention. [Figure 4] FIG. 4 is a schematic diagram for explaining a modification of the modulation pattern of the light modulator of the spot light generating device shown in FIG. [Figure 5] FIG. 5 is a schematic diagram for explaining a modification of the modulation pattern of the light modulator of the spot light generating device shown in FIG. [Figure 6] FIG. 6 is a schematic diagram of a microscope according to a third embodiment of the present invention. [Figure 7] FIG. 7 is an image showing the results of measuring the relationship between the modulation pattern in the optical modulator and the light intensity distribution of the needle spot in the first embodiment. [Figure 8] FIG. 8 is an image showing the results of measuring the relationship between the modulation pattern in the optical modulator and the light intensity distribution of the needle spot in the first embodiment. [Figure 9] FIG. 9 is an image showing the results of measuring the relationship between the modulation pattern in the optical modulator and the light intensity distribution of the needle spot in the first embodiment. [Figure 10] FIG. 10 is an image showing the results of measuring the relationship between the modulation pattern in the optical modulator and the light intensity distribution of the needle spot in the first embodiment. [Figure 11] FIG. 11 is an image showing the results of measuring the relationship between the modulation pattern in the optical modulator and the light intensity distribution of the needle spot in the first embodiment. [Figure 12] FIG. 12 is a graph showing the results of measuring the relationship between the defect angle and the ratio of the peak intensity of the first side lobe to the peak intensity of the central lobe in the first example. [Figure 13] FIG. 13 is a graph showing the results of measuring the relationship between the defect angle and the half-width of the central lobe in the first example. [Figure 14] FIG. 14 is an image showing the results of measuring the relationship between amplitude modulation patterns with different defect angles and the emission distribution of fluorescence from the sample in the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, an embodiment of a spot light generating device, an optical information detecting device, and a microscope to which the present invention is applied will be described with reference to the drawings.

[0014] (First aspect) 1, a spot light generation device 10 according to an embodiment of the present invention includes at least an optical modulator 14, a lens 16, and lenses 15 and 18, and further includes a light source 12, a lens 11, and a control device 200. The light source 12 emits a CW laser beam L1. The lens 11 collimates the laser beam L1 emitted from the light source 12. The collimated laser beam L1 has a beam area larger than that of a modulation surface 114 of the optical modulator 14, which will be described next. Note that the lens 11 is omitted when collimated light having a predetermined beam area is directly emitted from the emission surface of the light source 12.

[0015] The optical modulator 14 has a modulation surface 114 that modulates at least the amplitude of the incident laser light L1. That is, the amplitude distribution (amplitude) of the laser light L1 incident on the modulation surface 114 of the optical modulator 14 is modulated by the modulation pattern of the modulation surface 114. The optical modulator 14 is, for example, a spatial light modulator (SLM) that can modulate the spatial amplitude and phase distribution of light. Examples of SLMs that can be used include a liquid crystal spatial light modulator (LCOS-SLM) that performs the above modulation using liquid crystals, and a digital micromirror device (DMD) equipped with a microelectromechanical system (MEMS) that performs the above modulation using micromirrors. In this embodiment, a reflective LCOS-SLM that can modulate the spatial phase distribution is used as the optical modulator 14, and an optical system is used in which an aperture 31 formed in a shielding plate 33 is combined between the lens 15 and the lens 18. Because a reflective LCOS-SLM is used, the laser light L1 incident on the modulation surface 114 and the laser light L1 emitted from the modulation surface 114 travel within an area on the same side of the modulation surface 114. Although not shown, a transmissive LCOS-SLM may also be used as the optical modulator 14. In that case, the laser light L1 collimated by the lens 11 enters the modulation surface 114 from the side opposite to the side from which the amplitude-modulated laser light L1 is emitted.

[0016] The modulation surface 114 of the optical modulator 14 is disposed parallel to a plane including the η-axis and the ξ-axis. The η-axis and the ξ-axis are perpendicular to each other, and the plane including the η-axis and the ξ-axis intersects with the optical axis A1 of the laser light L1 incident on the modulation surface 114 and the laser light L1 emitted from the modulation surface 114. The ξ-axis is perpendicular to the optical axis A1. The η-axis is perpendicular to the ξ-axis and parallel to the plane including the optical axis A1, and forms an angle with respect to the optical axis A1. A plurality of liquid crystal molecules (not shown) are arranged on the modulation surface 114 of the optical modulator 14. The modulation amount of each of the plurality of liquid crystal molecules arranged on the modulation surface 114 is controlled by a control device 200 connected to the optical modulator 14 by wire or wirelessly. The control device 200 is, for example, a computer. Specifically, by setting the desired modulation amount for each of the multiple liquid crystal molecules on the modulation surface 114 via dedicated software or the like on a computer connected to the LCOS-SLM, each of the multiple liquid crystal molecules is phase-modulated with the desired modulation value.

[0017] In the light spot generation device 10, a Bessel beam is formed as the needle light spot LN formed by the lens 16. Therefore, among the multiple liquid crystal molecules arranged on the modulation surface 114, as shown in FIG. 2, the liquid crystal molecules included in the arc regions AC, AC on the modulation surface 114 are modulated, while the liquid crystal molecules not included in the annular region C are not modulated. Because the modulation surface 114 is modulated as described above, the arc regions AC, AC are regions with high reflectance for the incident laser light L1. The total light reflectance (reflectance) of the laser light L1 on the arc regions AC, AC is at least 50% or more, preferably 60% or more, and more preferably 80% or more. On the other hand, the total light reflectance of the laser light L1 on the modulation surface 114 other than the arc regions AC, AC is at least 20% or less, and preferably 10% or less. In other words, the laser light L1 is almost entirely blocked by the regions on the modulation surface 114 other than the arc regions AC, AC. In this specification, the reflectance or transmittance at the modulation surface 114 includes both the reflectance or transmittance at the modulation surface 114 in the case where the optical modulator 14 is composed of a DMD or the like and the reflection amount of the laser light L1 is directly controlled at the modulation surface 114, and the ratio expressed as (amount of light of the laser light L1 reflected or transmitted through the modulated area on the modulation surface 114 and passed through the aperture 31) / (amount of light of the laser light L1 incident on the modulated area on the modulation surface 114) in the case where the optical modulator 14 is equipped with a modulator that performs only phase modulation, as described below, and forms a tilt wavefront on the modulation surface 114 to spatially separate the zeroth order light and first order light of the laser light L1 on the Fourier surface of the modulation surface 114, and allows only the first order light to pass through the aperture 31, thereby modulating the laser light L1 in amplitude; this corresponds to the latter case in the present embodiment.

[0018] When the modulation surface 114 is viewed from the front, the arc regions AC, AC are the remaining regions of the annular region C, which has a center AQ, an outer radius r1, and an inner radius r2, cut out at a predetermined angle on both sides in the circumferential direction from a position N where the annular region C intersects with the η axis, and are formed symmetrically about the η axis. Hereinafter, the angle twice the predetermined angle, i.e., the angle by which the annular region C is cut out in the circumferential direction, is referred to as the missing angle φ. The missing angle φ is, for example, in the range of 20° to 60°, and preferably 40° to 60°. Optimization of the missing angle φ will be described later.

[0019] In the first mode, the liquid crystal molecules included in the arcuate regions AC are phase-modulated in addition to amplitude-modulated. A phase modulation amount exp[ik x sin(θ ξ In the phase modulation amount, i represents an imaginary unit, k represents a wave number, x represents a position in a direction parallel to the ξ axis on the modulation surface 114, and θ ξ represents the predetermined angle mentioned above.

[0020] The laser light L1 irradiated onto the modulation surface 114 of the optical modulator 14 is amplitude-modulated by the liquid crystal molecules contained in the arc-shaped regions AC, AC of the modulation surface 114, and is reflected and diffracted as shown in FIG. 1 . Note that, unless otherwise specified, reflection refers to specular reflection in this specification. As described above, the laser light L1 emitted from the optical modulator 14 passes sequentially through the lens 15, the aperture 31, and the lens 18. The lenses 15 and 18 are disposed on the optical axis A1 of the laser light L1 between at least the optical modulator 14 and the lens 16. In this embodiment, the lenses 15 and 18 are disposed between the optical modulator 14 and the half mirror 123. They are a pair of relay lenses that transfer the image of the pupil plane of the lens 16 to the modulation surface 114 of the optical modulator 14. The lenses 15 and 18 are provided as relay lenses of a so-called 4f optical system. In other words, the distance between the modulation surface 114 of the optical modulator 14 and the center plane of the lens 15 on the optical axis A1 is approximately equal to the focal length of the lens 15. The distance between the center plane of lens 15 and the center plane of lens 18 on optical axis A1 is approximately equal to the sum of the focal lengths of lens 15 and lens 18. The distance between the center plane of lens 18 and the pupil plane of lens 16 on optical axis A1 is approximately equal to the focal length of lens 18. Furthermore, an aperture 31 such as a pinhole is disposed on the focal plane of lens 15 (i.e., the Fourier plane of modulation surface 114) on optical axis A1. That is, the aperture 31 formed in lens 15 and shielding plate 33 is provided between optical modulator 14 and half mirror 123 on optical axis A1. The first-order light of laser light L1 focused by lens 15 passes through aperture 31. On the other hand, the zero-order light of laser light L1 reflected by modulation surface 114 without being phase-modulated and focused by lens 15 is shielded by shielding plate 33 on which aperture 31 is formed. In the spot light generating device 10 shown in Figure 1, only phase modulation is performed so that a phase modulation amount that imparts a tilt to the wavefront of the laser light L1 is expressed in a predetermined area (i.e., a pair of arc areas AC, AC) of the modulation surface 114 of the reflective LCOS-SLM that constitutes the optical modulator 14, and the first-order light and the zeroth-order light are spatially separated, the zeroth-order light is blocked by the blocking plate 33, and only the first-order light passes through the aperture 31, thereby resulting in amplitude modulation of the laser light L1.In other words, when the optical modulator 14 includes an SLM or the like capable of only phase modulation on the modulation surface 114, the modulation surface 114 functions as a modulation surface configured to enable spatial amplitude modulation of the laser light L1 by combining a pair of lenses 15, 18, which are disposed forward of the optical modulator 14 in the traveling direction of the laser light L1 and rearward of the half mirror 123 in the traveling direction of the laser light L1, with an aperture 31 formed between the lenses 15, 18. The aperture 31 is disposed on the focal plane of the lenses 15, 18 on the optical axis A1. The primary light of the laser light L1 that passes through the aperture 31 is reflected by the reflecting surface 123a of the half mirror 123 and enters the lens 16. The lens 16 focuses the incident laser light L1. An objective lens is used as the lens 16.

[0021] The lens 16 forms a needle light spot LN from the incident laser light L1 within a focusing region including the focal plane of the lens 16. The dimension g of the needle light spot LN in a direction parallel to the optical axis A1 is greater than the dimension w in a direction intersecting the optical axis A1 (e.g., the H and V directions in FIG. 1). The Bessel beam formed as the needle light spot LN is a beam in which interference generates a central lobe E1 (i.e., a central spot) that has a higher optical intensity axially along the propagation axis than the surrounding area. The optical intensity distribution of the Bessel beam in the radial direction (the H and V directions in FIG. 1) is expressed as the square of the Bessel function, as the name suggests, and is described by a Bessel function of the first kind.

[0022] The intersecting plane BX, which intersects with the optical axis A1 of the laser beam L1 focused by the lens 16, is a plane that includes the H direction and the V direction. The H direction and the V direction are perpendicular to each other and to the optical axis A1 of the laser beam L1 focused by the lens 16. Of the V direction, the direction to one side with respect to the optical axis A1 is defined as the +V direction, and the other side, i.e., the direction parallel to and opposite the +V direction, is defined as the -V direction. Of the H direction, the direction to one side with respect to the optical axis A1 is defined as the +H direction, and the other side, i.e., the direction parallel to and opposite the +H direction, is defined as the -H direction. At the intersecting plane BX, a central lobe E1 appears at the center of the needle spot light LN, and side lobe portions E2 appear on the outer periphery of the central lobe E1. The side lobe portion E2 includes a plurality of side lobes that appear outside the central lobe E1 in the radial direction based on the center of the central lobe E1, and from the side closest to the central lobe E1 in the radial direction, a first side lobe SS1, a second side lobe SS2, ..., an m-th side lobe SSm are formed. Note that while Fig. 1 merely schematically shows the central lobe E1 and each side lobe SSm of the side lobe portion E2 as being formed at intervals from the center toward the outside in the radial direction, the light intensity distribution of the central lobe E1 and the side lobe portion E2 can be expressed by a continuous Bessel function of the first kind.

[0023] At the intersection plane BX, the position where the central lobe E1 has the highest peak value of light intensity is the position where the optical axis A1 passes. Hereinafter, the highest light intensity in each of the central lobe E1 and each side lobe SSm of the side lobe portion E2 may be referred to as the "peak intensity." The position where the peak intensity of the central lobe E1 appears is set as the origin. Moving from the origin in the ±V direction, the light intensity attenuates, repeatedly decreasing and increasing according to a Bessel function of the first kind. That is, the peak intensity of the central lobe E1 is the highest, and the peak intensities of each side lobe SSm of the side lobe portion E2 are all lower than the peak intensity of the central lobe E1. Furthermore, in the ±V direction, the peak intensity of the second side lobe SS2 is lower than the peak intensity of the first side lobe SS1. However, when m is a natural number greater than or equal to 2, the relationship in level between the peak intensity of the (m+1)th side lobe SS(m+1) and the peak intensity of the mth side lobe SSm varies depending on the defect angle φ of the modulation pattern on the modulation surface 114 of the optical modulator 14. In the ±V direction, the peak intensity of the first side lobe SS1 increases as the defect angle φ increases from 0° to 90°. When m is greater than or equal to 2, whether the peak intensity of the mth side lobe SSm increases or decreases as the defect angle φ increases from 0° to 90° depends on the values ​​of the defect angle φ and m.

[0024] In the H direction of the cross plane BX, as one moves from the origin toward the ±H direction, the light intensity attenuates, repeatedly decreasing and increasing according to a Bessel function of the first kind. That is, the peak intensity of the central lobe E1 is the highest, and the peak intensities of each side lobe SSm of the side lobe portion E2 are all lower than the peak intensity of the central lobe E1. However, in the ±H direction, if m is a natural number, the peak intensity of the (m+1)th side lobe SS(m+1) is lower than the peak intensity of the mth side lobe SSm. Furthermore, for the same missing angle φ, the peak intensity of the first side lobe in the ±H direction is lower than the peak intensity of the first side lobe in the ±V direction. In the ±H direction, as the missing angle φ increases from 0° to 90°, the peak intensity of the first side lobe SS1 decreases, and even if m is 2 or greater, the peak intensity of the mth side lobe SSm decreases. That is, in the ±H direction, as the defect angle φ increases from 0° to 90°, the peak intensity of the first side lobe SS1 as well as the peak intensity of the side lobes radially outward from the origin than the first side lobe SS1 decreases, and the overall light amount of the side lobe portion E2 is suppressed.

[0025] The ratio of the peak intensity of the first side lobe SS1 to the peak intensity of the central lobe E1 in the ±H directions is smaller than the ratio of the peak intensity of the first side lobe SS1 to the peak intensity of the central lobe E1 in the ±V directions. Also, the ratio of the total light intensity of the side lobe portion E2 to the light intensity of the central lobe E1 in the ±H directions is smaller than the ratio of the total light intensity of the side lobe portion E2 to the light intensity of the central lobe E1 in the ±V directions. In the spot light generation device 10 shown in FIG. 1 , the laser beam L1 emitted from the light source 12 and collected by the lens 16 propagates at a substantially constant position in the height direction parallel to the ξ axis of the modulation surface 114 of the optical modulator 14 and the V direction of the crossing plane BX. As described above, the reason why the side lobe portion E2 is suppressed more in the ±H directions than in the ±V directions is that the lens 16 is disposed after the optical modulator 14 on the optical axis A1 of the laser light L1 (i.e., ahead of the laser light L1 in the traveling direction), and therefore the η axis of the modulation surface 114 uniquely corresponds to the H direction of the crossing plane BX. In other words, the portion of the modulation surface 114 shown in FIG. 2 that is cut out from the annular region C by a defect angle φ with respect to the η axis contributes to suppressing the side lobe portion E2 in the ±H directions at the crossing plane BX due to the Fourier transform function of the lens 16. The direction to which the ±H directions, in which the side lobe portion E2 is effectively suppressed at the crossing plane BX, uniquely corresponds on the modulation surface 114 of the optical modulator 14 is determined by the traveling direction of the laser light L1 emitted from the optical modulator 14 and whether or not the optical axis A1 is bent and the number of times it is bent.

[0026] The control device 200 imparts predetermined amplitude and phase modulation values ​​to each of the plurality of liquid crystal molecules arranged on the modulation surface 114 of the optical modulator 14. The control device 200 performs amplitude modulation and phase modulation on the liquid crystal molecules included in the arc regions AC, AC of the modulation surface 114 based on the relationship between the above-mentioned defect angle φ and the degree of suppression (sometimes referred to as the suppression amount) of the side lobe portion E2 of the needle spot light LN.

[0027] For example, when the needle spot light LN is irradiated onto minute regions P1, P2, and P3 at different positions on the optical axis A1 within the irradiation region of the needle spot light LN, mainly the irradiation region of the central lobe E1, some kind of optical reaction occurs, and if there is a substance (not shown) that emits light L2 in a direction approximately parallel to and opposite to the incident direction of the laser light L1, the needle spot light LN is formed, causing light L2 to be emitted from each of the minute regions P1, P2, and P3. The light L2 passes through the reflecting surface 123a of the half mirror 123. For example, an optical modulator 32, a lens 25, and multiple photodetectors 42 are sequentially arranged ahead of the half mirror 123 in the traveling direction of the light L2. Note that if the wavelength bands of the laser light L1 and the light L2 are different from each other, a dichroic mirror is used instead of the half mirror 123.

[0028] The optical modulator 32 has a modulation surface 132 that modulates at least the amplitude of the incident light L2. A plurality of liquid crystal molecules (not shown) are arranged on the modulation surface 132. The modulation amount of each of the plurality of liquid crystal molecules arranged on the modulation surface 132 is controlled by a control device (not shown) connected to the optical modulator 32. The control device (not shown) is, for example, a computer, and may be dedicated to the optical modulator 32 or may be shared with the control device 200. A computer-generated hologram (CGH) 210 is formed on the modulation surface 132 of the optical modulator 32. The CGH 210 is a transmission-type holographic optical element that diffracts the incident light L2 and deflects the transmitted light via a lens 25, achieving wavefront reconstruction using diffraction. The light L2 emitted from each of the microscopic regions P1, P2, and P3 upon irradiation with the needle spot light LN is the object light of the CGH 210. The CGH 210 linearly converts displacement in the direction (z direction in FIG. 1 ) along the optical axis of the object light (i.e., the optical axis A2 of light L2), which is parallel to the optical axis A1, into displacement in the H direction of the image plane IP at an image formation distance lz from the modulation surface 132. The amplitude and phase distributions of the CGH 210 are not limited as long as they can realize the aforementioned function of the CGH 210. For example, they may be a phase distribution determined based on equation (6) disclosed in Japanese Patent Application Laid-Open No. 2019-117233. A CGH designed using equation (6) is a two-dimensional phase-type multiplexed CGH. Specifically, the CGH 210 can be displayed on the modulation surface 132 by matching the phase control pattern of multiple liquid crystal molecules included in the region forming the CGH 210 on the modulation surface 132 of the optical modulator 32 with the CGH pattern designed using equation (6).

[0029] The CGH 210 or a modulation pattern other than the CGH 210 formed on the modulation plane 132 does not affect the wavefront of the incident light L2, at least in the H direction. In other words, there is almost no irradiation of the side lobe portion E2 suppressed in the H direction in each of the minute regions P1, P2, and P3, and almost no optical effect due to this irradiation. At an intersecting plane (not shown) that intersects with the optical axis A2, the maximum light intensity and light amount of the light L2 in the H direction are lower than the maximum light intensity and light amount in the V direction.

[0030] Furthermore, a modulation pattern having an amplitude distribution or phase distribution may be formed on the modulation surface 132, which diffracts the light L2 from each of the infinitesimal regions P1, P2, and P3, and forms an Airy beam that curves so as to describe a parabola with respect to the optical axis A2 on the image plane IP via the lens 25. In this case, the Airy beams converted from the light L2 from each of the infinitesimal regions P1, P2, and P3 are focused at different positions on the image plane IP.

[0031] Light L2 incident on the CGH 210 is diffracted by the CGH 210 and focused on an image plane IP by the lens 25. In the focusing region where light L2 is focused on the image plane IP, detection surfaces 142 of multiple photodetectors 42 are arranged along the H direction. While details of the focusing region are not shown in FIG. 1 , it is an area including positions Q1, Q2, and Q3 where the microregions P1, P2, and P3 from which light L2 is emitted within the irradiation region of the optical needle spot light LN in the z direction are linearly transformed onto the detection surface 142. Light L2 emitted from each of the microregions P1, P2, and P3 is focused on different positions Q1, Q2, and Q3 on the image plane IP by the CGH 210 and detected by the photodetectors 42 arranged at the positions Q1, Q2, and Q3. That is, light L2 emitted from each of the microregions P1, P2, and P3 is detected by different photodetectors 42.

[0032] Mainly the central lobe E1 of the light L2 emitted from each of the minute regions P1, P2, and P3 is incident on the detection surfaces 142 of different predetermined photodetectors 42. At this time, because the side lobe portion E2 of the needle spot light LN in the H direction is suppressed as described above, the side lobe portion E2 of each of the light L2 emitted from each of the minute regions P1, P2, and P3 is hardly incident on the detection surfaces 142 of photodetectors 42 other than the predetermined photodetector 42, for example, the photodetector 42 adjacent to the predetermined photodetector 42. Even if a small amount of the side lobe portion E2 is incident on a photodetector 42 other than the predetermined photodetector 42, a high contrast or signal-to-noise (SN) ratio can be obtained when detecting the light L2 at the image plane IP using multiple photodetectors 42.

[0033] The CGH 210 is not limited to linearly converting displacement in the z direction parallel to the optical axis A2 into displacement in the H direction of the image plane IP, but may also linearly convert displacement into displacement in the V direction. In this case, the detection surfaces 142 of multiple photodetectors 42 are arranged along the V direction. Light L2 emitted from each of the minute regions P1, P2, and P3 is separated in the V direction into the detection surfaces 142 of the photodetectors 42 that are different from each other.

[0034] The control device 200 may calculate, as the evaluation parameters, at least one of the following: the FWHM of the central lobe E1 at the crossing plane BX; the FWHM of the first side lobe SS1; the ratio between the peak intensity of the central lobe E1 and the peak intensity of the first side lobe SS1; and the ratio between the light intensity of the central lobe E1 and the light intensity of the side lobe portion E2. In this case, the light receiving surface of a photodetector (not shown) may be disposed at the crossing plane BX of the irradiation area of ​​the needle spot light LN, and the control device 200 may be connected to the photodetector via wired or wireless communication to acquire electrical output information representing the light intensity received by the photodetector. The control device 200 may also be connected to multiple photodetectors 42 via wired or wireless communication to acquire electrical output information representing the light intensity received by each of the multiple photodetectors 42, and calculate, as the evaluation parameters, the detection accuracy, contrast, or SNR of the light L2 at the image plane IP. The control device 200 may set the defect angle φ on the modulation plane 114 of the optical modulator 14 so that the evaluation parameters satisfy predetermined criteria.

[0035] The spot light generation device 10 of the first embodiment described above includes a reflective optical modulator 14 having a modulation surface 114 configured to enable spatial amplitude modulation of the incident laser beam L1, a lens (light-collecting element) 16 that collects the laser beam L1 emitted from the optical modulator 14, and lenses (relay lenses) 15 and 18 that are arranged between the optical modulator 14 and the lens 16 on the optical axis A1 of the laser beam L1 and image-transfer the pupil plane of the lens 16 to the modulation surface 114. When viewed from the front, the modulation surface 114 has a pair of arc regions AC and AC formed as reflection regions (regions) that modulate the amplitude of the incident laser beam L1 and reflect the laser beam L1. As shown in FIG. 2, the arc-shaped regions AC and AC are the remaining regions of the annular region C, which has a predetermined radius r3 and a predetermined width t from the center AQ, separated by a separation region (region within a predetermined angle) NC within a range of a missing angle (predetermined angle) φ, with positions N and N symmetrical with respect to the center AQ. The positions N and N and the center AQ are located on a straight line forming a diameter. The radius r3 is expressed as (r1 + r2) / 2, where r1 is the outer radius and r2 is the inner radius, and is equal to or less than the radius of the region on the modulation surface 114 that corresponds to the pupil region of the lens 16. In the light spot generation device 10, the laser light L1 incident on the optical modulator 14 is modulated by the pair of arc-shaped regions AC and AC on the modulation surface 114, which are conjugate with the pupil plane of the lens 16. The laser light L1 emitted from the modulation surface 114 is then focused by the lens 16, forming a needle light spot LN having a dimension g greater than a dimension w. The dimensions w and g are determined by the radius r3 and the radial width t. In the light spot generation device 10, a Bessel beam is formed as the needle light spot LN. In the light spot generation device 10, as described above, the annular region C of the modulation surface 114 is cut into divided regions NC, NC that face each other in a direction parallel to the η axis, so that the side lobe portion E2 in the H direction at the crossing plane BX of the needle light spot LN is suppressed more than the central lobe E1. The light intensity distribution of the needle light spot LN on the axis parallel to the H direction at the crossing plane BX is a distribution that appears after the light intensity distribution of the η axis on the modulation surface 114 of the optical modulator 14 is transformed by the Fourier transform function of the lens 16.That is, according to the light spot generation device 10, by separating a pair of arc regions AC, AC on the modulation surface 114 of the optical modulator 14 by a dividing region NC of a defect angle φ in the circumferential direction at the position N of the η axis, it is possible to easily suppress the side lobe portion E2 of the needle light spot LN in the H direction (predetermined direction). Furthermore, even if there is a minute region outside the central lobe E1 in the direction intersecting the optical axis A1 that can emit light L2 when irradiated with the needle light spot LN, the suppression of the side lobe portion E2 makes it possible to prevent the light L2 (i.e., response light) from the minute region from being incident on the detection surface 142 of the photodetector 42 in the H direction of the image plane IP and being detected.

[0036] In the first embodiment, a reflective LCOS-SLM is used as the light modulator 14. However, depending on the required layout of the spot light generating device 10, a transmissive LCOS-SLM or a spatial light modulator other than a transmissive LCOS-SLM, such as a DMD, which can directly modulate the amplitude of the wavefront of the incident laser light L1 on the modulation surface 114, may be used as the light modulator 14. That is, when viewed from the front, the modulation surface 114 may be formed with a pair of arc-shaped regions AC, AC as transmission regions (regions) that directly modulate the amplitude of the incident laser light L1 and transmit the laser light L1. Even in this case, the total light transmittance (transmittance) of the laser light L1 through the arc-shaped regions AC, AC on the modulation surface 114 is at least 50% or more, preferably 60% or more, and more preferably 80% or more. On the other hand, the total light transmittance of the laser light L1 in regions other than the arc-shaped regions AC, AC on the modulation surface 114 is at least 20% or less, and preferably 10% or less. In this case as well, the laser light L1 is almost entirely blocked by the regions on the modulation surface 114 other than the arc regions AC and AC.

[0037] Furthermore, in the first aspect, an LCOS-SLM, which is an active element, is used as the optical modulator 14, but a passive plate element or the like in which a pair of arc regions AC, AC are formed as apertures in a shielding plate may also be used as the optical modulator 14. Note that when a modulator capable of directly modulating the amplitude of the wavefront of the laser light L1 on the modulation surface 114, such as a DMD or the above-mentioned plate element, is used as the optical modulator 14, it is not necessary to place the shielding plate 33 in which the aperture 31 is formed, between the lens 15 and the lens 18 on the optical axis A1.

[0038] In the spot light generation device 10 of the first aspect, the transmittance or reflectance of the laser light L1 in each of the arc regions AC and the divided regions NC varies discontinuously in the circumferential direction. Specifically, the total light transmittance of the laser light L1 in each of the arc regions AC and the divided regions NC is constant in the circumferential direction. The total light transmittance of the laser light L1 in the arc regions AC and the divided regions NC is different from the total light transmittance of the laser light L1 in the divided regions NC. According to the spot light generation device 10, the transmittance of the laser light L1 in each of the arc regions AC and the divided regions NC is approximately constant in the circumferential direction, which makes it easy to configure and prepare the optical modulator 14.

[0039] In the first embodiment, a plurality of photodetectors 42 are provided to detect light L2 generated from each of the microregions P1, P2, and P3 by irradiation with a needle light spot (light spot) LN formed from a laser beam L1 focused by a lens 16. The light L2 generated from the microregions P1, P2, and P3 is detected by different photodetectors 42. The spot light generation device 10 of the first embodiment can acquire information about the light intensity of the light L2 from the plurality of photodetectors 42 with high contrast and signal-to-noise ratio. Furthermore, the H direction (first direction) along which the detection surface 142 of the photodetector 42 extends is relative to a direction (second direction) parallel to the η axis connecting the center AQ of the modulation surface 114 of the optical modulator 14 and positions point-symmetrical (symmetrical) with respect to the center AQ. In other words, the H direction and the direction parallel to the η axis correspond one-to-one. The H direction and the direction parallel to the η axis are uniquely associated with each other by the Fourier transform function of the lens 16. In the light spot generation device 10 shown in FIG. 1, the incident direction of the laser beam L1 on the reflecting surface 123a of the half mirror 123 and the exit direction of the laser beam L1 from the reflecting surface 123a are both in a plane at the same height, so the H direction is perpendicular to the direction parallel to the ξ axis. However, if an optical system such as a relay lens is disposed between the optical modulator 14 and the lens 16 on the optical axis A1 of the laser beam L1, or if a mirror is disposed to vertically reflect the optical axis A1, the H direction may be parallel to the ξ axis while maintaining the relative relationship based on the Fourier transform, depending on the function of the optical system or mirror. Alternatively, the H direction may be tilted at an angle less than 90° with respect to the direction parallel to the ξ axis. According to the light spot generation device 10, the missing angle φ in the axial direction on the modulation surface 114 can be set according to the relative relationship based on the Fourier transform, corresponding to the desired direction for suppressing the side lobe portion E2 at the intersection plane BX of the needle light spot LN. In other words, the direction for suppressing the side lobe portion E2 of the needle light spot LN can be easily set.

[0040] The above-described plurality of photodetectors 42 may be provided in the spot light generation device 10 or in an optical device separate from the spot light generation device 10.

[0041] The light spot generation device 10 of the first embodiment further includes a control device 200 that controls the amplitude modulation amount of the modulation surface 114 of the active optical modulator 14. The control device 200 is configured to acquire, from the multiple optical modulators 14, information on the ratio of the peak intensity of a first side lobe SS1 (the side lobe closest to the central lobe among the side lobes) to the peak intensity of a central lobe E1 in the H direction of the light L2 generated by the needle light spot LN (hereinafter, sometimes referred to as the peak intensity ratio) and the FWHM (full width at half maximum) of the central lobe E1. The control device 200 sets the defect angle φ on the modulation surface 114 of the optical modulator 14 in accordance with at least the information on the peak intensity ratio and the FWHM. When the peak intensity ratio exceeds a predetermined value, the ratio of the total light intensity of the side lobe portion E2 to the light intensity of the central lobe E1 also increases, resulting in a decrease in the amount of light detected by a predetermined photodetector 42 and an increase in the amount of light detected by photodetectors 42 other than the predetermined photodetector 42, resulting in an increase in the signal-to-noise ratio. The predetermined value is appropriately set based on the signal-to-noise ratio (SN ratio), minimum detectable light intensity, dark current value, and other factors set for the photodetector 42. Furthermore, if the FWHM of the central lobe E1 exceeds a predetermined size, the light L2 incident on the detection surface 142 of the photodetector 42 may excessively extend beyond the detection surface 142, reducing the amount of light received by the photodetector 42 and potentially impinging on the detection surface 142 of another photodetector 42 adjacent in the H direction. The predetermined size is appropriately set based on the effective area of ​​the detection surface 142 of the photodetector 42. For example, the control device 200 may set the defect angle φ to increase the peak intensity ratio, with the minimum requirements being that the peak intensity ratio is equal to or less than a predetermined value and that the FWHM of the central lobe E1 is equal to or less than a predetermined size. The spot light generation device 10 optimizes the defect angle φ based on information related to the peak intensity ratio and the FWHM of the central lobe E1, as well as the degree of suppression of the side lobe portion E2, thereby enabling highly accurate detection of the light L2 resulting from the central lobe E1.

[0042] In addition, in the control device 200, in order to optimize the missing angle φ, other appropriate parameters may be considered as parameters for evaluating the degree of suppression of the side lobe portion E2, particularly the degree of suppression of the first side lobe SS1, in addition to the above-mentioned peak intensity ratio and FWHM of the central lobe E1.

[0043] Furthermore, the peak intensity ratio, the FWHM of the central lobe E1, and the parameter values ​​for the above-described evaluation are acquired by arranging a plurality of photodetectors or image capture devices (not shown) on a plane optically equivalent to the crossing plane BX and connecting the photodetectors or image capture devices by wire or wirelessly to the control device 200. The plane optically equivalent to the crossing plane BX is, for example, a focusing plane when the laser light L1 is branched on the optical axis A1 between the optical modulator 14 and the half mirror 123 in a direction different from the direction from the optical modulator 14 to the half mirror 123, and the branched laser light L1 is focused by a lens having specifications similar to those of the lens 16.

[0044] In the first aspect, the light L2 generated by the needle spot light LN generated by the light spot generation device 10 is detected by multiple photodetectors 42. However, the use of the needle spot light LN is not limited to generating the light L2 in minute areas P1, P2, and P3 within the irradiation area. For example, a workpiece placed in the irradiation area of ​​the needle spot light LN may be machined in the H direction, or optical information may be recorded in the H direction on a recording medium placed in the irradiation area of ​​the needle spot light LN. Note that, when the needle spot light LN is directly utilized as in the above example and it is not necessary to detect light emitted from minute areas within the irradiation area of ​​the needle spot light LN, the half mirror 123, the optical modulator 32, the lens 25, and the photodetector 42 can be omitted, and the lens 16 may be positioned so that the optical axis A1 from the modulation surface 114 of the optical modulator 14 to the lens 16 is a straight line without being folded.

[0045] (Second aspect) In the following description of the second and subsequent aspects, the description of the contents common to the configuration described in the first aspect will be omitted. Furthermore, in the description of the second and subsequent aspects, components that function similarly to the components described in the first aspect will be assigned the same reference numerals as those of the corresponding components described in the first aspect, and the description thereof will be omitted.

[0046] The spot light generating device of the second embodiment is similar to the spot light generating device 10 described with reference to Figures 1 and 2, except that the radial polarization element 140 and the modulation pattern of the modulation surface 114 of the optical modulator 14 are changed as described below.

[0047] In a second embodiment, a radial polarization element 140 is disposed between the lens 11 and the optical modulator 14 on the optical axis A1 of the laser beam L1 of the spot light generating device 10. The radial polarization element 140 has a known configuration and may be, for example, an element in which a birefringent nano-grating is formed inside a quartz substrate. The polarization state of the laser beam L1 collimated by the lens 11 is linearly polarized, but as shown in FIG. 3, the polarization state of the laser beam L1 incident on the radial polarization element 140 is radially polarized (also referred to as radial polarization). The light intensity distribution of the laser beam L1 converted into radial polarization is donut-shaped, centered on the optical axis A1, on a plane intersecting the optical axis A1. The polarization direction of the laser beam L1 converted into radial polarization is distributed radially along the radial direction, centered on the optical axis A1, within a plane intersecting the optical axis A1. If the complex amplitude of the laser light L1 incident on the modulation surface 114 of the optical modulator 14 is E0(ξ,η), the electric field vector E(ξ,η) of the laser light L1 converted into radially polarized light is expressed by the following equation (1): ψ represents the angle in the circumferential direction based on one side of the ξ axis on a plane that includes the ξ axis and the η axis and is parallel to the modulation surface 114. In equation (1), the first row represents the horizontally polarized component, and the second row represents the vertically polarized component.

[0048]

number

[0049] Although not shown, the second embodiment also uses a reflective LCOS-SLM capable of modulating the spatial phase distribution as the optical modulator 14, and an optical system combining an aperture 31 formed in a shielding plate 33 between the lens 15 and the lens 18 is used. In the second embodiment, the defective angle φ is 0° on the modulation surface 114 of the optical modulator 14, no dividing region NC is formed, and an annular region C is formed. The total optical reflectance (reflectance) of the laser light L1 is at least 50% or more, preferably 60% or more, and more preferably 80% or more. On the other hand, the total optical reflectance of the laser light L1 in the region of the modulation surface 114 other than the annular region C is at least 20% or less, preferably 10% or less. A phase of 0 is imparted to one side of the modulation surface 114, with a boundary LQ passing through the center AQ of the modulation surface 114 and parallel to the η axis, and a phase of π is imparted to the other side. That is, on the modulation surface 114, the light distribution direction of the liquid crystal molecules is controlled so that a phase inversion of 0-π occurs with the boundary LQ as a boundary. In addition, the light distribution direction of the multiple liquid crystal molecules contained in the annular region C is expressed as the phase modulation amount exp[ikx sin(θ ξ )] is regulated to express

[0050] The laser light L1 irradiated onto the modulation surface 114 of the optical modulator 14 is reflected as shown in FIG. 3 while being amplitude-modulated and phase-modulated by the modulation surface 114. Of the laser light L1 irradiated onto the modulation surface 114, the zero-order light is so-called background light and contains the vertically polarized component of equation (1) above. On the other hand, of the laser light L1 irradiated onto the modulation surface 114, only the horizontally polarized component is extracted as the first-order light, and the first-order light has an amplitude-modulated component of cos ψ in the first row of equation (1) above. When viewed on a plane intersecting the optical axis, the laser light L1 is composed of a pair of arc beams LA, LA that are line-symmetric with respect to the η axis and V direction. As described above, the laser light L1 is phase-modulated on the modulation surface 114 of the optical modulator 14 so that a phase inversion of 0-π occurs with the boundary line LQ as the boundary, and therefore the pair of arc beams LA, LA are in phase with each other. If the modulation surface 114 were not subjected to phase modulation by a 0-π population inversion, the polarization directions of the pair of arc-shaped beams LA, LA would be radially polarized, facing outward from the optical axis A1 along the ξ axis and H direction in a mutually inverted manner, and the pair of arc-shaped beams LA, LA would have different phases. Because the pair of arc-shaped beams LA, LA are in phase with each other, the first-order light of the laser beam L1 emitted from the modulation surface 114 is amplitude-modulated by |cosψ|, has an emission angle different from that of the zero-order light, and passes through the aperture 31 and travels toward the half mirror 123 and lens 16. The zero-order light of the laser beam L1 is blocked by the blocking plate 33. The pair of arc-shaped beams LA, LA are condensed by the lens 16, and a needle spot light LN is formed.

[0051] In the second aspect, a pair of arc beams LA, LA are in phase with each other and amplitude-modulated by |cosψ|, thereby forming a needle light spot LN in which the peak intensity of the central lobe E1 is higher than the peak intensity of each side lobe of the side lobe portion E2. Also in the second aspect, the side lobe portion E2 of the needle light spot LN in the H direction is suppressed. Furthermore, in the spot light generation device of the second aspect, the total light intensity of the side lobe portion E2 of the needle light spot LN is suppressed more strongly than the light intensity of the central lobe E1 in the spot light generation device 10 of the first aspect.

[0052] The spot light generation device of the second embodiment described above has a configuration similar to that of the spot light generation device 10 of the first embodiment, and thereby provides the same effects as those of the spot light generation device 10 of the first embodiment. The spot light generation device of the second embodiment also includes a radial polarization element 140 that converts the polarization of incident laser light L1 into radial polarization, an optical modulator 14 having a modulation surface 114 configured to be able to phase-modulate the laser light L1 emitted from the radial polarization element 140, a lens (light-collecting element) 16 that condenses the laser light L1 emitted from the optical modulator 14, and lenses 15 and 18 that are arranged between the optical modulator 14 and the lens 16 on the optical axis A1 of the laser light L1 and image-transfer the pupil plane of the lens 16 to the modulation surface 114, similar to the first embodiment. In the second embodiment, the modulation surface 114 is configured to enable spatial amplitude modulation of the incident laser light L1. In the second embodiment, an annular region C having a radius r3 and a width t from a center AQ is formed on a modulation surface 114 of the optical modulator 14, which is conjugate with the pupil plane of the lens 16, as a region for reflecting the incident laser beam L1. Furthermore, on the modulation surface 114, the phases on both sides are inverted with respect to each other across a boundary LQ that passes through the center AQ of the annular region C and positions N, N of the annular region C that are symmetrical with respect to the center AQ. That is, on the modulation surface 114, the laser beam L1 is phase-modulated so that a phase inversion of 0-π is imparted to the irradiated laser beam L1 across the boundary LQ. In the spot light generation device of the second embodiment, radially polarized laser beam L1 is irradiated onto the modulation surface 114 that has been amplitude-modulated and phase-modulated as described above, and a laser beam L1 composed of a pair of arc-shaped beams LA, LA is emitted from the modulation surface 114. The pair of arc-shaped beams LA, LA are in phase with each other and are amplitude-modulated by |cosψ|. As a result, when the laser beam L1 emitted from the modulation surface 114 is focused by the lens 16, the side lobe portion E2 is effectively suppressed relative to the central lobe E1 in the H direction of the crossing plane BX. According to the spot light generation device of the second aspect, the light amount of the side lobe portion E2 including multiple side lobes SSm in addition to the first side lobe SS1 can be suppressed as much as possible in the H direction.

[0053] As a modification of the light spot generation device of the second embodiment, as shown in FIG. 4, a mask may be used as the optical modulator 14. The mask changes the reflectivity of the irradiated laser beam L1 continuously on the ξ axis by |ξ| or |cosψ| within the pupil region 116 of the lens 16, as shown in FIG. 5, when the ξ axis and the η axis are taken with the center AQ at the origin on the modulation surface 114. In this case, as in the first embodiment, the phases of the laser beams L1 do not need to be inverted relative to each other across the boundary LQ on the modulation surface 114. Furthermore, the polarization of the laser beam L1 irradiated on the modulation surface 114 does not need to be radially polarized, but may be linearly polarized, and the radial polarization element 140 can be omitted. Even when such a mask is used as the optical modulator 14, the side lobe portion E2 of the needle light spot LN can be easily suppressed in the H direction, as in the first and second embodiments.

[0054] (Third aspect) 6, a microscope 300 of the third embodiment includes at least an optical information detection device 150, and further includes a light source 12 and an image information creation device 60. The optical information detection device 150 includes a spot light generation device 100, a shift spot light conversion device 30, and an optical information acquisition device 40. The light source 12 emits laser light L1 having an excitation wavelength of fluorescence L3 that is generated by excitation of a sample S when the sample S is irradiated with a needle spot light LN, which will be described later.

[0055] In the optical information detection device 150, a needle light spot LN, whose magnitude in a direction parallel to the optical axis A1 is greater than the magnitude of the laser light L1 in a direction intersecting the optical axis A1, is irradiated onto the sample S. The longitudinal direction of the needle light spot LN when irradiating the sample S is approximately parallel to the thickness direction of the sample S and approximately parallel to the z direction. In the optical information detection device 150, emitted light beams from each of a plurality of different detection regions included in the irradiation region R of the needle light spot LN on the sample S are converted into shifted light beams L4. The detection regions are positioned sequentially along the longitudinal direction of the needle light spot LN when irradiating the sample S. In the optical information detection device 150, the shifted light beams L4 emitted from each of the plurality of detection regions reach different positions on the light receiving surface M intersecting the optical axis A2. Optical information of each of the plurality of detection regions is detected from information such as the light intensity of the shifted light beam L4 received on the light receiving surface M.

[0056] The light spot generating device 100 includes at least an optical modulator 14 and a lens 16, and further includes a light source 12, mirrors 13, 19, 21, 162, and 170, lenses 15, 18, 166, 168, 20, and 22, and an aperture 31. The light source 12 emits a laser beam L1 having optical characteristics such as a predetermined wavelength, light intensity, and power. The optical characteristics of the laser beam L1 are appropriately selected according to the conditions under which, when a needle light spot LN generated by conversion of the laser beam L1 is irradiated onto an irradiation area of ​​a sample S (irradiation area R is omitted in FIG. 6 ) from direction D3, light L2 is emitted from the irradiation area along the optical axis A2 in a predetermined direction. In the third embodiment, a fluorescent substance is used as the sample S. The needle light spot LN formed from the laser beam L1 is excitation light for the sample S. That is, the wavelength of the laser beam L1 includes the excitation wavelength of the fluorescence of the sample S. Since the optical information detection device 150 is configured to detect fluorescence (emitted light) L3 as light L2 emitted from the sample S, the aforementioned predetermined direction means the incident direction of the needle spot light LN onto the sample S, i.e., a direction approximately parallel to and opposite to the z direction. In this embodiment, of the fluorescence emitted in almost all directions from the sample S excited by irradiation with the needle spot light LN, the fluorescence emitted in a direction approximately parallel to and opposite to the z direction (predetermined direction) can be detected.

[0057] In the spot light generation device 100, a mirror 13, an optical modulator 14, a lens 15, an aperture 31, a lens 18, a dichroic mirror 124, a mirror 162, lenses 166 and 168, mirrors 170 and 19, a lens 20, a mirror 21, lenses 22, and lenses 16 are sequentially arranged from rear to front in the light traveling direction along an optical axis A1 of the laser light L1 emitted from the light source 12 between the exit surface of the light source 12 and the incident surface of the sample S. The laser light L1 emitted from the light source 12 travels along the optical axis A1, is reflected by the mirror 13, and enters the optical modulator 14.

[0058] The laser light L1, which has been amplitude-modulated and phase-modulated by the optical modulator 14, is diffracted by the optical modulator 14 and emitted from the optical modulator 14, and travels along the optical axis A1 via the lens 15 and other optical elements. The lenses 15 and 18, the lenses 166 and 168, and the lenses 20 and 22 are each appropriately positioned on the optical axis A1 to relay the pupil plane of the lens 16 to the modulation plane 114 of the optical modulator 14. In other words, the modulation plane 114 is equivalent to the pupil plane of the lens 16. As described in the first embodiment, an aperture 31 is positioned on the focal plane of the lenses 15 and 18 on the optical axis A1. The primary light of the laser light L1 that passes through the aperture 31 is reflected by the reflecting surface 124a of the dichroic mirror 124 and enters the mirror 162.

[0059] The mirror 162 is provided for scanning in the y direction, which are parallel to the mounting surface of the stage T on which the sample S is mounted and perpendicular to each other. Specifically, the laser light L1 is scanned in the y direction by rotating a support member 164 supporting the mirror 162 in the α1 direction. The mirror 162 is disposed at a position where the pupil plane of the lens 16 is transferred. The laser light L1 reflected by the mirror 162 passes through lenses 166 and 168 that constitute a relay lens system and is incident on the mirror 170. The mirror 170 is disposed at a position where the image is transferred by the lenses 166 and 168 from a position optically equivalent to the pupil plane where the mirror 162 is disposed. The mirror 170 is provided for scanning in the x direction. Specifically, the laser light L1 is scanned in the x direction by rotating a support member 172 supporting the mirror 170 in the α2 direction. The laser light L 1 reflected by the mirror 170 is reflected by the mirror 19 , passes through the lens 20 , is reflected again by the mirror 21 , passes through the lens 22 , and enters the lens 16 .

[0060] The laser beam L1 emitted from the lens 22 along the optical axis A1 enters the lens 16, where it is focused by the lens 16 in directions intersecting the optical axis A1 (the x and y directions in FIG. 1 ) while extending in a direction parallel to the optical axis A1 (the z direction in FIG. 1 ), forming a needle spot beam LN that spreads over an irradiation region R (not shown) inside the sample S. The lens 16 is supported by a piezoelectric scanner 190. The z-direction position of the lens 16 can be adjusted with high precision by the piezoelectric scanner 190 to fine-tune the observation position of the sample S (i.e., the center position of the needle spot beam LN in the z direction). Because the needle spot beam LN is non-diffracting, strong light is reliably irradiated toward the irradiation region, and fluorescent samples S within the irradiation region are excited simultaneously in the z direction. The larger the dimension g of the needle spot beam LN relative to the dimension w, the greater the number of detection regions from which optical information can be simultaneously acquired in the thickness direction of the sample S, i.e., the z direction.

[0061] 6, the sample S is placed on the surface (mounting surface) of the stage T on the incident side of the laser light L1. The stage T is provided in the optical information detection device 150 by a support member or the like (not shown). The stage T may be provided in the microscope 300, or may be provided in a device that is formed separately from the optical information detection device 150 or the microscope 300 and that is accessible to the optical information detection device 150.

[0062] The fluorescence L3 emitted from different microscopic regions in the z direction of the sample S travels in the opposite direction along approximately the same path as the path that the laser light L1 took to enter the sample S, passes through lenses 16, 22, 20, 168, and 166 from the sample S, is reflected by mirrors 21, 19, 170, and 162, and enters the dichroic mirror 124. The fluorescence L3 passes through the reflecting surface 124a and the dichroic mirror 124, and enters the shifted spot light conversion device 30.

[0063] The shifted spot light conversion device 30 includes lenses 182, 184, and 25, a light modulator 32, and a mirror 28. The lenses 182 and 184, the light modulator 32, the mirror 28, and the lens 25 are sequentially arranged along the optical axis A2 of the fluorescence L3 from rear to front in the light propagation direction.

[0064] The shifted spot light conversion device 30 converts the fluorescence L3 emitted from multiple different positions on the optical axis A1 within the irradiation area of ​​the needle light spot LN on the sample S into a shifted light spot L4 that shifts as it moves along the optical axis A2 so that the focusing position on an image plane IP intersecting the optical axis A2 changes depending on the emission position of the fluorescence L3 on the sample S. Although the image plane IP is not shown in FIG. 6 , the detection planes 142 of multiple photodetectors 42 are arranged on the image plane IP. In the shifted spot light conversion device 30, the lenses 182 and 184 are appropriately positioned on the optical axis A2 to relay the pupil plane of the lens 16, image-transferred to the position where the mirror 162 is located, to the modulation plane 132 of the optical modulator 32. In other words, the modulation plane 132 is equivalent to the pupil plane of the lens 16. The modulation pattern of the CGH 210 described in the first embodiment is formed on the modulation plane 132. The optical information in the z direction of the fluorescence L3 emitted from each position in the z direction of the needle light spot LN is linearly converted in the H direction by the CGH 210. The shifted light spot L4 emitted from the modulation surface 132 of the optical modulator 32 is incident on the optical information acquisition device 40.

[0065] The optical information acquisition device 40 receives the shift light spot L4 incident from the shift spot light conversion device 30 and acquires optical information of the irradiation area of ​​the needle light spot LN on the sample S from information on the received shift light spot L4. The optical information acquisition device 40 includes a plurality of photodetectors 42 and an optical information acquisition device 48. As described in the first aspect, the detection surfaces 142 of the plurality of photodetectors 42 are arranged in the H direction of the image plane IP. The optical information acquisition device 48 is connected to the plurality of photodetectors 42 by wire or wirelessly, acquires information on the amount of received light of the shift light spot L4 for each of the plurality of photodetectors 42, and is, for example, a computer.

[0066] The image information creation device 60 creates image information, such as a three-dimensional image, from the information about the sample S acquired by the optical information acquisition device 40, and displays it on a monitor 62. The image information creation device 60 may be incorporated into a computer that constitutes the optical information acquisition device 48. In such a configuration, information about the shifted spot light L4 received by the optical information acquisition device 40 can be instantly displayed on a monitor or the like and visualized.

[0067] In the optical information detection device 150, to enable the needle light spot LN to scan the sample S in the x and y directions, lenses 15 and 18, lenses 166 and 168, lenses 20 and 22, a mirror 162 for scanning the laser light L1 in the y direction, a mirror 162 for scanning the laser light L1 in the x direction, a dichroic mirror 124 for bending the optical axis A1, and mirrors 19 and 21 are arranged on the optical axis A1 of the light spot generation device 10 between the optical modulator 14 and the lens 16. Because the pupil plane of the lens 16 is image-transferred by the lenses 20 and 22 and the optical axis A1 is appropriately bent by the mirrors 19 and 21, the reflective surface of the mirror 170 is optically equivalent to the pupil plane of the lens 16. Furthermore, because the reflective surface of the mirror 170 is image-transferred by the lenses 166 and 168, the reflective surface of the mirror 162 is optically equivalent to the pupil plane of the lens 16. Furthermore, since the reflection surface of mirror 170 is image-transferred by lenses 15 and 18, modulation surface 114 of optical modulator 14 is optically equivalent to the pupil plane of lens 16. In the configuration of optical information detection device 150 shown in Fig. 6, the modulation pattern of modulation surface 114 of optical modulator 14 is rotated by 90° in a front view from the modulation pattern of modulation surface 114 in the configuration shown in Fig. 1 described in the first embodiment. That is, in the configuration of optical information detection device 150 shown in Fig. 6, an imaginary line (not shown) connecting center AQ of modulation surface 114 of optical modulator 14 and positions N, N is parallel to the ξ axis, and dividing regions NC, NC that divide annular region C of modulation surface 114 in the circumferential direction face each other in a direction parallel to the ξ axis. In the configuration of the optical information detection device 150, the direction parallel to the ξ axis of the modulation surface 114 is optically equivalent to the y direction parallel to the surface on the stage T on which the sample S is placed, and is converted into the y direction by each optical component between the optical modulator 14 and the lens 16 on the optical axis A1. Similarly, in the configuration of the optical information detection device 150, the direction parallel to the η axis of the modulation surface 114 is optically equivalent to the x direction parallel to the surface on the stage T on which the sample S is placed, and is converted into the x direction by each optical component between the optical modulator 14 and the lens 16 on the optical axis A1.

[0068] In the optical information detection device 150, lenses 20 and 22, lenses 166 and 168, lenses 182 and 184, and mirrors 19, 21, 162, and 170 that reflect the optical axis A2 of the fluorescence L3 are arranged on an image plane (light-receiving plane) IP on which the lens 16 and the detection surface 142 of the photodetector 42 are arranged, along the optical axis A2 of the fluorescence L3 emitted from the sample S. The path of the fluorescence L3 that arrives at the dichroic mirror 124 from the lens 16 after being emitted from the sample S overlaps with the path of the laser light L1 that arrives at the lens 16 after being reflected by the dichroic mirror 124, but is opposite to the path of the laser light L1. Because the reflective surface of the mirror 170 is image-transferred by the lenses 182 and 184, the modulation plane 132 of the optical modulator 32 is optically equivalent to the pupil plane of the lens 16. Therefore, the y direction, which is approximately parallel to the mounting surface of the stage T, is converted to the +H direction of the image plane IP. Because the side lobe portion E2 of the needle spot light LN in the y direction is suppressed and the wavefront of the fluorescence L3 is not affected or modulated in any way along the path of the fluorescence L3 on the optical axis A2 from lens 16 to lens 25, the side lobe portion E2 of the fluorescence L3 in the H direction is suppressed more than the side lobe portion E2 in the V direction at the image plane IP. As shown in FIG. 6 , the detection surfaces 142 of multiple photodetectors 42 are arranged along the H direction, so that the central lobe E1 of the fluorescence L3 is mainly incident on the detection surface 142 of a specific photodetector 42 corresponding to the position in the z direction where the fluorescence L3 was generated in the irradiation area of ​​the needle spot light LN. Furthermore, the side lobe portion E2 is incident on photodetectors 42 other than the specific photodetector 42. As a result, the multiple photodetectors 42 detect the fluorescence L3 with high contrast and a low S / N ratio.

[0069] In the optical information detection device 150, the control device 200 may be connected to the optical information acquisition device 40 by wire or wirelessly. For example, when a predetermined photodetector 42 detects fluorescence L3, the control device 200 may obtain a ratio between an electrical output representing the intensity of received light at the predetermined photodetector 42 and an electrical output representing the intensity of received light at a photodetector 42 adjacent to the predetermined photodetector 42 in the H direction as an index of contrast when the fluorescence L3 is detected, and optimize the modulation pattern on the modulation surface 114 of the optical modulator 14.

[0070] The optical information detection device 150 of the third aspect described above includes a light source 12, a light spot generation device 10, a shifted light spot conversion device 30, and an optical information acquisition device 40. The light source 12 emits a laser light L1. In the optical information detection device 150, the laser light L1 is focused by a lens (focusing element) 16 in the light spot generation device 10 to form a needle light spot LN. The dimension (size) of the needle light spot LN in the z direction is larger than the dimension (size) in the x direction or y direction. In the optical information detection device 150, a sample S is placed in an irradiation range of the needle light spot LN that is elongated in the z direction, and the thickness direction of the sample S is approximately parallel to the z direction. The shifted spot light conversion device 30 separates the fluorescence (emitted light) L3 emitted from multiple different positions in the z direction (direction parallel to the optical axis) within the irradiation area of ​​the needle spot light LN in the H direction (predetermined direction) on an image plane (light-receiving surface) IP (see FIG. 1) that intersects with the optical axis A2 of the fluorescence L3. The optical information acquisition device 40 has multiple photodetectors 42 that receive the fluorescence L3 separated in the H direction on the image plane IP of the CGH 210 by the shifted spot light conversion device 30, and acquires optical information of the emission position (i.e., microscopic region) of the fluorescence L3 on the sample S. In the optical information detection device 150, the detection surface 142 of the photodetector 42 extends in the H direction, which is optically equivalent to the direction parallel to the ξ axis connecting the center AQ of the modulation surface 114 of the optical modulator 14 and positions N and N that are symmetrical to each other across the center AQ. "Optically equivalent" means that it is uniquely determined with respect to the modulation surface 114 of the optical modulator 14 according to image transfer by a relay lens system or the like or axial rotation by a mirror on a plane intersecting the optical axis. According to the optical information detection device 150, when fluorescence L3 is generated from at least one minute region in the z direction of the irradiation area of ​​the needle spot light LN, the central lobe E1 of the fluorescence L3 is made incident on the detection surface 142 of a predetermined photodetector 42 corresponding to the position of the minute region in the z direction, and side lobe portions E2 that may be incident on photodetectors 42 other than the predetermined photodetector 42 are minimized, making it possible to detect the optical information contained in the fluorescence L3 received by the photodetector 42 with high contrast and a low S / N ratio.Furthermore, even if there is a minute region outside the detection target that can be excited and emit fluorescence L3 when irradiated with the needle spot light LN outside the central lobe E1 in a direction intersecting the optical axis A1 of the needle spot light LN, the fluorescence L3 (i.e., response light) from the minute region outside the detection target can be prevented from being incident on and detected by the detection surface 142 of a predetermined photodetector 42 in the H direction of the image plane IP along which the detection surfaces 142 of the multiple photodetectors 42 extend, because the side lobe portion E2 is suppressed. In particular, when the needle spot light LN is scanned two-dimensionally along the H direction and the V direction (i.e., scanned in the y direction and the x direction on the surface on which the sample S is placed on the stage T) as in the configuration of the optical information detection device 150 of the third aspect, the above-mentioned effect is significantly exhibited. If an optical information detection device 150 equipped with a CGH 20 and a plurality of photodetectors 42 arranged one-dimensionally along the H direction can suppress the side lobe portion E2 in the H direction for two-dimensional scanning of the needle spot light LN, for example, it can reduce signals (so-called artifacts) not to be detected that are caused by the side lobe portion E2, which was a problem in conventional devices.

[0071] According to the optical information detection device 150, since the spot light generation device 10 is provided, by controlling the missing angle φ in a predetermined direction passing through the center AQ on the light modulation surface 114 of the optical modulator 14, it is possible to easily and flexibly suppress the side lobe portion E2 in a direction optically equivalent to the above-mentioned predetermined direction of the needle spot light. Note that the optical information detection device 150 may be provided with the spot light generation device of the second aspect instead of the spot light generation device 10 of the first aspect. Also, the modified examples described regarding the spot light generation device 10 of the first aspect and the spot light generation device of the second aspect may be applied to the optical information detection device 150.

[0072] The microscope 300 of the third aspect described above includes the optical information detection device 150 described above and an image information creation device 60 that creates image information about the sample S based on optical information acquired from the fluorescence L3 by the optical information detection device 150. According to the microscope 300, the side lobe portion E2 can be easily and flexibly suppressed in a predetermined direction of the needle spot light LN by controlling the defect angle φ on the modulation surface 114 of the optical modulator 14, or by converting the laser light L1 into radially polarized light and imparting a 0-π phase inversion with a boundary line LQ passing through the center AQ on the modulation surface 114, while reflecting the light from the annular region C. Furthermore, unlike conventional methods, it is not necessary to use an expensive light source based on the principle of two-photon absorption to suppress the side lobe portion E2.

[0073] Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments. Various modifications are possible within the scope of the gist of the present invention as set forth in the claims. Furthermore, the configurations of different embodiments may be appropriately combined.

[0074] For example, in the above-described optical information detection device 150 and microscope 300, the light L2 to be detected is the fluorescence L3 emitted from a minute region of the sample S excited by irradiation with the needle spot light LN, but the light L2 to be detected is not limited to the fluorescence L3. The light L2 to be detected may be, for example, reflected light reflected from at least one minute region within the irradiation region when the needle spot light LN is irradiated.

[0075] Hereinafter, embodiments of the spot light generating device, the optical information detecting device, and the microscope according to the present invention will be described. However, the present invention is not limited to the contents of the following embodiments.

[0076] In the first example, a spot light generating device 10 shown in FIG. 6 was constructed. The light source 12 was a laser light source (model number: DJ532-40, manufacturer: Thorlab, Inc.) that emitted laser light L1 having a peak wavelength of 532 nm. The optical modulator 14 was an LCOS-SLM (model number: SLM-100, manufacturer: Santec Corporation). The area of ​​the modulation surface 114 of the LCOS-SLM used was larger than the area of ​​the pupil plane of the lens 16. The focal lengths of the lenses 15 and 18 were each 150 mm. The focal lengths of the lenses 166, 168, and 20 were each 80 mm. The lens 22 was a tube lens with a focal length of 200 mm. The lens 16 was a water-immersion objective lens with a focal length of 5 mm and a numerical aperture of 1.15.

[0077] In the first example, the amplitude modulation pattern described in the first embodiment and with reference to Fig. 2 was formed on the modulation surface 114 of the optical modulator 14 of the spot light generation device 10. Specifically, an arc region AC having an outer radius r1 = 0.711r and an inner radius r2 = 0.684r, where r is the pupil radius of the lens 16, was set on the modulation surface 114 of the optical modulator 14.

[0078] The upper part of each of Figures 7 to 11 shows a two-dimensional distribution of the modulation pattern on the modulation plane 114 (i.e., the pupil plane of the lens 16). The middle part of each of Figures 7 to 11 shows a two-dimensional light intensity distribution of the needle spot light LN formed on the focal plane of the lens 16 in a plane including the x and y directions. The left part of the lower part of each of Figures 7 to 11 shows a two-dimensional light intensity distribution of the needle spot light LN formed on the focal plane of the lens 16 in a plane including the x and y directions. The center of the lower part of each of Figures 7 to 11 shows a two-dimensional light intensity distribution of the needle spot light LN formed on the focal plane of the lens 16 in a plane including the x and y directions. The upper right part of the lower part of each of Figures 7 to 11 shows a one-dimensional light intensity distribution in the x direction of the needle spot light LN formed on the focal plane of the lens 16. 7 to 11, the lower right corner of the lower row shows the one-dimensional light intensity distribution in the y direction of the needle spot light LN formed on the focal plane of the lens 16. Note that in each graph of the one-dimensional light intensity distribution, the maximum light intensity is normalized to 1.

[0079] Figure 7 shows the measurement results when the defect angle φ = 0°, that is, when the light distribution direction of the liquid crystal molecules contained in the annular region C, where the arc regions AC are connected in the circumferential direction, is controlled as described above. As shown in Figure 7, when the defect angle φ = 0°, a central lobe E1 formed along the optical axis A1 and side lobe portions E2 generated around the central lobe E1 on a plane including the x and y directions that intersect with the optical axis A1 appear. The peak intensity of the central lobe E1 is higher than the peak intensity of either of the side lobe portions E2.

[0080] FIG. 8 shows the measurement results when the defect angle φ is 20°. FIG. 9 shows the measurement results when the defect angle φ is 40°. FIG. 10 shows the measurement results when the defect angle φ is 60°. As shown in FIGS. 7 to 10, in the two-dimensional light intensity distribution on a plane including the x and y directions, as the defect angle φ increases, the total light intensity of the side lobe portion E2 relative to the light intensity of the central lobe E1 increases. Furthermore, as the defect angle φ increases, the peak intensity of the first side lobe SS1, which is closest to the central lobe E1 in a plane including the x and y directions that intersects with the optical axis A1, increases and approaches the maximum light intensity of the central lobe E1, among the multiple side lobes included in the side lobe portion E2. As shown in FIGS. 9 and 10, when the defect angle φ exceeds 40° and reaches 60°, in the side lobe portion E2, the peak intensity of the second side lobe SS2, which is the next closest to the central lobe E1 after the first side lobe SS1 in the plane including the x and y directions, increases, and the first side lobe S1 and the second side lobe SS2 become apparent.

[0081] Measurement results for an amplitude modulation mask of |cosψ| are shown in Fig. 11. As shown in Fig. 11, in the two-dimensional light intensity distribution on a plane including the x and y directions, when the amplitude modulation mask described in the second embodiment is used, the side lobe portion E2 is suppressed compared to the case where a pair of arc regions AC, AC described in the first embodiment is formed, regardless of the size of the defect angle φ.

[0082] FIG. 12 is a graph in which the horizontal axis represents the defect angle φ (defect angle) of the first embodiment and the vertical axis represents the ratio of the peak intensity of the first side lobe SS1 to the peak intensity of the central lobe E1 (i.e., the peak intensity ratio). FIG. 13 is a graph in which the horizontal axis represents the defect angle φ and the vertical axis represents the FWHM of the central lobe E1. The FWHM of the central lobe E1 on the vertical axis represents the ratio when the FWHM of the central lobe E1 when the defect angle φ is 0° is set to 1. In each of the graphs in FIGS. 12 and 13, for reference, the values ​​in the x direction for the amplitude modulation mask described in the second embodiment are shown by a dashed line, and the values ​​in the y direction for the amplitude modulation mask are shown by a dashed line. As shown in FIG. 12, on the x axis, the peak intensity ratio increases as the defect angle φ increases, and when the defect angle φ is approximately 40° or more, the peak intensity ratio for the amplitude modulation mask exceeds 0.52. On the other hand, on the y-axis, the peak intensity ratio decreased as the defect angle φ increased, approaching the peak intensity ratio of 0.048 for the amplitude modulation mask. However, even when the defect angle φ was less than 90° and close to 90°, it was still higher than the peak intensity ratio for the amplitude modulation mask. Also, as shown in FIG. 13 , on the x-axis, the FWHM of the central lobe E1 decreased as the defect angle φ increased, and at defect angles φ of approximately 50° or greater, it became smaller than the FWHM of the central lobe E1 of 0.89 for the amplitude modulation mask. On the other hand, on the y-axis, the FWHM of the central lobe E1 increased as the defect angle φ increased, and at defect angles φ of approximately 50° or greater, it became larger than the FWHM of the central lobe E1 of 1.20 for the amplitude modulation mask. It was found that the amplitude modulation mask of the second embodiment had a high side lobe suppression effect on the y-axis, but exhibited side lobes approximately three times larger on the x-axis than those obtained with a circular mask with a defect angle φ of 0° (a state in which a Bessel beam is formed). From the graphs shown in Figures 12 and 13, when focusing on two parameters, namely the peak intensity ratio of the first side lobe SS1 and the FWHM of the central lobe E1, it was confirmed that under the conditions of the first embodiment, the defect angle φ of the mask consisting of a pair of arc regions of the first mode corresponding to the amplitude modulation mask is preferably between 40° and 50°.

[0083] In the second example, a microscope 300 as shown in FIG. 6 was constructed. However, for the purpose of observing the intensity distribution of the fluorescence L3 when the side lobe portion E2 of the needle spot light LN in the H direction is suppressed, the detection position was not resolved in the z direction, and no shifted spot light was generated. That is, no modulation pattern was formed on the modulation surface 132 of the optical modulator 32, and the wavefront of the fluorescence L3 incident on the optical modulator 32 was not affected by the modulation surface 132, so the fluorescence L3 was mostly reflected by the optical modulator 32. Furthermore, the number of photodetectors 42 was one. The focal length of the lens 182 was 80 mm. The focal length of the lens 184 was 150 mm. An LCOS-SLM (model number: SLM-100, manufacturer: Santec Corporation) was used as the optical modulator 32. The focal length of the lens 25 was 300 mm. A commercially available photodetector (model number: R10467U-40, manufacturer: Hamamatsu Photonics KK) was used as the photodetector 42. Furthermore, fluorescent beads with an average particle size of 0.2 μm were used as the sample S.

[0084] The upper part of Figure 14 shows two-dimensional distributions of amplitude modulation patterns when the defect angle φ on the modulation surface 114 of the optical modulator 14 is, from the left, 0°, 36°, 52°, and 64°. The lower part of Figure 14 shows two-dimensional images detected by the photodetector 42 of the fluorescence emission distribution of the fluorescent beads when the amplitude modulation pattern shown in the upper part is formed on the modulation surface 114. As shown in Figure 14, when the defect angle φ is 36°, 52°, or 64°, compared to when the defect angle φ is 0°, i.e., when an annular mask is used for focusing (a state in which a Bessel beam is formed), the side lobe portion E2 of the needle spot light LN is suppressed in the vertical direction of the page, i.e., in the direction optically equivalent to the direction in which the division region NC dividing the annular region C on the modulation surface 114 is formed, and fluorescence L3 from the sample S can be detected with high contrast.

[0085] From the results of the examples described above, it was confirmed that the spot light generating device, optical information detection device, and microscope of each of the above-mentioned aspects can suppress the side lobe portion E2 of the needle spot light LN in a specified direction with a simple configuration and a high degree of freedom. [Explanation of symbols]

[0086] 10, 100 Spot light generating device 14 Optical Modulator 16 Lens (light-collecting element) 114 Modulation Surface 150 Optical information detection device 300 Microscope AQ-centered C annular region r3 radius (predetermined radius) t width (predetermined width)

Claims

1. an optical modulator having a modulation surface configured to enable spatial amplitude modulation of incident laser light; a focusing element that focuses the laser light emitted from the optical modulator; a relay lens disposed between the optical modulator and the condensing element on the optical axis of the laser light, for transferring an image of a pupil plane of the condensing element to the modulation plane; Equipped with On the modulation surface, a pair of arc-shaped regions, which are separated by regions within a range of a predetermined angle based on positions symmetrical to each other across the center, in an annular region having a predetermined radius and a predetermined width from the center as a region that transmits or reflects the incident laser light, amplitude-modulates and phase-modulates the laser light, the transmittance or reflectance of the laser light in each of the arcuate region and the region within the predetermined angle range varies continuously in the circumferential direction; Spot light generating device.

2. An optical modulator having a modulation surface configured to enable spatial amplitude modulation of incident laser light; a focusing element that focuses the laser light emitted from the optical modulator; a relay lens disposed between the optical modulator and the condensing element on the optical axis of the laser light, for transferring an image of a pupil plane of the condensing element to the modulation plane; Equipped with On the modulation surface, a pair of arc-shaped regions, which are separated by regions within a range of a predetermined angle based on positions symmetrical to each other across the center, in an annular region having a predetermined radius and a predetermined width from the center as a region that transmits or reflects the incident laser light, amplitude-modulates and phase-modulates the laser light, the transmittance or reflectance of the laser light in each of the arcuate region and the region within the predetermined angle range varies discontinuously in the circumferential direction, The predetermined angle is between 20° and 60°. Spot light generating device.

3. a radial polarization element that converts the polarization of the incident laser light into radial polarization; an optical modulator having a modulation surface configured to be able to phase-modulate the laser light emitted from the radial polarization element; a focusing element that focuses the laser light emitted from the optical modulator; a relay lens disposed between the optical modulator and the condensing element on the optical axis of the laser light, for transferring an image of a pupil plane of the condensing element to the modulation plane; Equipped with On the modulation surface, an annular region having a predetermined radius and a predetermined width from the center is formed as a region that transmits or reflects the incident laser light, and phases on both sides of a boundary line that passes through the center and positions of the annular region that are symmetrical to each other with respect to the center are inverted from each other. Spot light generating device.

4. a photodetector is provided to detect light generated by spot light formed by the laser light focused by the focusing element; a first direction in which the detection surface of the photodetector extends has a relative relationship with a second direction connecting the center of the modulation surface and positions symmetrical to each other across the center; The spot light generating device according to claim 1 .

5. a control device for controlling an amplitude modulation amount of the modulation surface, the control device acquires information on a ratio of a peak intensity of a first side lobe closest to the central lobe among side lobes to a peak intensity of a central lobe in a first direction relative to a second direction connecting the center of the modulation surface and positions symmetrical to each other across the center in the spot light formed by the laser light focused by the focusing element, and information on a half-value width of the central lobe, and sets a predetermined angle according to the information; The spot light generating device according to claim 1 .

6. a light source that emits laser light; The spot light generating device according to claim 1 ; a shift spot light conversion device that separates outgoing light emitted from a plurality of different positions in a direction parallel to the optical axis of the irradiation area into predetermined directions on a light receiving surface that intersects with the optical axis of the outgoing light when the needle spot light irradiation area is formed by focusing the laser light by the focusing element of the spot light generation device and has a size in a direction parallel to the optical axis larger than a size in a direction intersecting with the optical axis and is irradiated onto a sample; an optical information acquisition device having a photodetector that receives the emitted light that has been split in the predetermined direction on the light receiving surface by the shift spot light conversion device, and that acquires optical information about the emission position of the emitted light; Equipped with a detection surface of the photodetector extends in a direction optically equivalent to a direction connecting the center of the modulation surface and positions symmetrical to each other across the center; Optical information detection device.

7. The optical information detection device according to claim 6 ; an image information creation device that creates image information about the sample based on optical information acquired from the emitted light by the optical information acquisition device; Equipped with microscope.

8. a light source that emits laser light; an optical modulator having a modulation surface configured to enable spatial amplitude modulation of the incident laser light; a focusing element that focuses the laser light emitted from the optical modulator; a relay lens disposed between the optical modulator and the condensing element on the optical axis of the laser light, for transferring an image of a pupil plane of the condensing element to the modulation plane; Equipped with a spot light generating device in which, on the modulation surface, a pair of arc-shaped regions, each of which is an annular region having a predetermined radius and a predetermined width from a center and which is separated by a region within a predetermined angle range based on positions symmetrical to each other with respect to the center, as a region that transmits or reflects the incident laser light, amplitude-modulates and phase-modulates the laser light; a shift spot light conversion device that separates outgoing light emitted from a plurality of different positions in a direction parallel to the optical axis of the irradiation area into predetermined directions on a light receiving surface that intersects with the optical axis of the outgoing light when the needle spot light irradiation area is formed by focusing the laser light by the focusing element of the spot light generation device and has a size in a direction parallel to the optical axis larger than a size in a direction intersecting with the optical axis and is irradiated onto a sample; an optical information acquisition device having a photodetector that receives the emitted light that has been split in the predetermined direction on the light receiving surface by the shift spot light conversion device, and that acquires optical information about the emission position of the emitted light; Equipped with a detection surface of the photodetector extends in a direction optically equivalent to a direction connecting the center of the modulation surface and positions symmetrical to each other across the center; Optical information detection device.

Images