JP2010058128A - Laser beam irradiation apparatus and laser beam irradiation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser beam irradiation apparatus which can reduce extension of laser beam condensing range at each of a plurality of condensing points inside of an object. <P>SOLUTION: The laser beam irradiation apparatus 1 is an apparatus which condenses and irradiates laser beam to a plurality of condensing points inside of the object 9, and includes a laser beam source 10, a prism 20, a spatial optical modulator 30, a lens 41, a lens 42, a mirror 50 and an objective lens 60. The laser beam output from the laser beam source 10 is input to the spatial optical modulator 30, which displays hologram to modulate phase of laser beam for each of a plurality of pixels arranged two-dimensionally and outputs the laser beam in a modulated phase. The hologram displayed on the spatial optical modulator 30 is generated by overlapping a condensing hologram that condenses laser beam to each of a plurality of condensing points and a compensating hologram that compensates aberration of laser beam corresponding to each of a plurality of condensing points. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an apparatus and a method for condensing and irradiating laser light to a plurality of condensing positions inside an object.

  The processing object can be processed by condensing the laser light output from the laser light source with a condensing optical system and irradiating the processing object. If the laser beam is simply condensed using a lens, the object to be processed can be processed into a desired shape by scanning one condensing position of the laser beam. However, in this case, the time required for processing is long.

  The simplest method for shortening the processing time is to perform simultaneous multi-point processing by simultaneously condensing and irradiating a plurality of condensing positions with laser light. For example, if a plurality of laser light sources are used and laser light output from each laser light source is collected by a lens, multi-point simultaneous processing can be performed. However, in this case, since a plurality of laser light sources are used, the cost is high, and the installation area and the optical system become complicated.

  An invention intended to solve such a problem is disclosed in Patent Document 1. In the invention disclosed in Patent Document 1, a hologram is presented on a phase modulation type spatial light modulator, and laser light output from one laser light source is phase-modulated by the spatial light modulator, and the phase modulation is performed. The collected laser light is simultaneously condensed and irradiated to a plurality of condensing positions by a condensing optical system. The hologram presented in the spatial light modulator has a phase modulation distribution such that laser light is condensed at a plurality of condensing positions by the condensing optical system.

In addition, the technique of condensing and irradiating laser light to a plurality of condensing positions inside an object as disclosed in Patent Document 1, for example, irradiating laser light inside glass or the like to refract the irradiation unit An optical integrated circuit is formed by causing a rate change, laser light is irradiated inside glass or the like to form a crack in the irradiated portion and cut, or laser light is irradiated inside a silicon wafer or the like to perform irradiation. In addition to being used for processing such as forming and cutting a modified layer on the part, it is also used for applications such as scanning a laser beam condensing position inside an object in a laser microscope or a multiphoton absorption microscope. Used.
JP 2006-68762 A

  However, in the invention disclosed in Patent Document 1, for example, when condensing and irradiating laser light to a plurality of condensing positions inside an object, the condensing area of the laser light at each condensing position extends in the optical axis direction. In addition, the degree of expansion of the light collection region varies depending on the light collection position. In such a case, it becomes difficult to perform accurate processing or imaging in the above-described processing application or imaging application. Further, for example, considering a processing application, the extension of the condensing region not only causes deterioration of the processing shape but also increases the required power of the laser beam.

  The present invention has been made to solve the above problems, and provides a laser beam irradiation apparatus and a laser beam irradiation method capable of reducing aberrations of laser beams at each of a plurality of condensing positions inside an object. The purpose is to provide.

  A laser light irradiation apparatus according to the present invention is an apparatus that condenses and irradiates laser light to a plurality of condensing positions inside an object, and (1) a laser light source that outputs laser light; and (2) a laser light source. Phase modulation type spatial light modulation that inputs the laser beam output from the laser, presents a hologram that modulates the phase of the laser beam at each of the two-dimensionally arranged pixels, and outputs the laser beam after the phase modulation And (3) a condensing optical system for condensing the laser light output from the spatial light modulator at a plurality of condensing positions, and (4) for condensing the laser light at each of the plurality of condensing positions. A control unit for presenting a hologram on which the hologram for condensing and a hologram for correction for correcting aberrations of laser light corresponding to each of a plurality of condensing positions are superimposed on the spatial light modulator. And

  In the laser beam irradiation apparatus according to the present invention, the control unit has a condensing position inside the object with respect to the condensing position when the condensing position exists outside the object and is not corrected. In addition, it is preferable to set a correction hologram based on the change in the optical path length of the light collection position when correction is performed.

  A laser light irradiation method according to the present invention is a method of condensing and irradiating laser light to a plurality of condensing positions inside an object, and (1) a laser light source that outputs laser light, and (2) a laser light source Phase modulation type spatial light modulation that inputs the laser beam output from the laser, presents a hologram that modulates the phase of the laser beam at each of the two-dimensionally arranged pixels, and outputs the laser beam after the phase modulation And (3) a condensing optical system that condenses the laser light output from the spatial light modulator at a plurality of condensing positions. The laser beam irradiation method according to the present invention corrects the aberration of the laser beam corresponding to each of the plurality of condensing positions and the condensing hologram for condensing the laser beam at each of the plurality of condensing positions. The correction hologram is superimposed on the hologram and the spatial light modulator is presented.

  In the laser beam irradiation method according to the present invention, the condensing position exists inside the object and is corrected with respect to the condensing position when the condensing position exists outside the object and is not corrected. In this case, it is preferable to set the correction hologram based on the change in the optical path length of the condensing position.

  According to the present invention, it is possible to reduce the aberration of laser light at each of a plurality of condensing positions.

  The best mode for carrying out the present invention will be described below in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 1 is a configuration diagram of a laser beam irradiation apparatus 1 according to the present embodiment. The laser beam irradiation device 1 shown in this figure is a device that focuses and irradiates laser light to a plurality of condensing positions inside an object 9, and includes a laser light source 10, a prism 20, a spatial light modulator 30, and driving. Unit 31, control unit 32, lens 41, lens 42, mirror 50, and objective lens (condensing optical system) 60.

  The laser light source 10 outputs laser light to be focused and irradiated on a plurality of condensing positions inside the object 9, and preferably a pulse laser light source such as a femtosecond laser light source or an Nd: YAG laser light source. It is.

  The spatial light modulator 30 is of a phase modulation type, and receives laser light output from the laser light source 10 and reflected by the first reflecting surface 21 of the prism 20, and in each of a plurality of two-dimensionally arranged pixels. A hologram that modulates the phase of the laser beam is presented, and the phase-modulated laser beam is output. The phase hologram presented in the spatial light modulator 30 is preferably a hologram (CGH: Computer Generated Hologram) obtained by numerical calculation.

  The spatial light modulator 30 may be a reflection type or a transmission type. The reflective spatial light modulator 20 may be any of LCOS (Liquid Crystal on Silicon) type, MEMS (Micro Electro Mechanical Systems) type, and optical address type. The transmissive spatial light modulator 20 may be an LCD (Liquid Crystal Display) or the like. In FIG. 1, a reflective type is shown as the spatial light modulator 30. In the case of the transmission type, the prism 20 is not necessary.

  The drive unit 31 sets a phase modulation amount in each of a plurality of pixels arranged two-dimensionally in the spatial light modulator 30, and a signal for setting the phase modulation amount for each pixel is sent to the spatial light modulator 30. give. The drive unit 31 causes the spatial light modulator 30 to present a hologram by setting the amount of phase modulation in each of the plurality of pixels that are two-dimensionally arranged in the spatial light modulator 30.

  The lens 41 and the lens 42 constitute a 4f optical system, and the spatial light modulator 30 and the objective lens 60 are disposed so as to form an imaging relationship with each other. That is, the 4f optical system including the lens 41 and the lens 42 inputs the laser light output from the spatial light modulator 30 and reflected by the second reflecting surface 22 of the prism 20, and the laser light in the spatial light modulator 30 is input. An image is formed on the objective lens 60.

  The mirror 50 inputs laser light output from the 4f optical system including the lens 41 and the lens 42 and reflects the laser light to the objective lens 60. The objective lens 60 as a condensing optical system inputs the laser light reflected by the mirror 50 and condenses the laser light at a plurality of condensing positions inside the object 9.

  The control unit 32 is configured by a computer, for example, and controls the operation of the drive unit 31 to write a hologram from the drive unit 31 to the spatial light modulator 30. At this time, the control unit 32 presents the spatial light modulator 30 with a hologram for condensing the laser light output from the spatial light modulator 30 at a plurality of condensing positions inside the object 9 by the condensing optical system 60. Let

FIG. 2 is a diagram illustrating a state in which laser light is condensed at two condensing positions A and B inside the object 9. The hologram φ _result presented in the spatial light modulator 30 is a collection hologram for condensing the laser light at the condensing position B, where φ _A is a condensing hologram for condensing the laser light at the condensing position A. the light hologram as phi _B, obtained by extracting only the phase from the result of the following equation (1). Here, K _A and K _B are coefficients. This operation is referred to as a “phasing method” in this specification. Compared with the case where the spatial light modulator 30 is divided into a plurality of small regions and holograms are arranged in each of the regions, using this phasing method, a plurality of holograms are arranged in one large region. Ensuring and light resistance can be improved.

Further, the light converging hologram phi _A for focusing a laser beam on the focusing position A, a hologram for condensing a laser beam at a predetermined position on a plane perpendicular to the optical axis of the objective lens 60 phi _{a_target} The hologram for condensing the laser beam at a predetermined position in the optical axis direction of the objective lens 60 is obtained as the following formula (2a) as _{φA_FLP} . Similarly, a condensing hologram φ _B for condensing laser light at the condensing position B is obtained by converting a hologram for condensing the laser light at a predetermined position on a plane perpendicular to the optical axis of the objective lens 60 into φ. and _{b_target,} a hologram for condensing the laser beam to a predetermined position in the optical axis direction of the objective lens 60 as φ _{B_FLP,} obtained from the following (2b) equation.

Holograms φ _{A_FLP} and φ _{B_FLP} for condensing laser light at a predetermined position along the optical axis direction of the objective lens 60 represent a Fresnel lens pattern (FLP) and are expressed by the following equation (3). The Here, r is the distance from the center, λ is the wavelength, and f is the focal length. FIG. 3 is a diagram showing a phase modulation distribution in the Fresnel lens pattern. In this figure, the phase modulation amount is shown in gray scale.

  A Fresnel zone plate (FZP) may be used instead of the Fresnel lens pattern. The Fresnel zone plate has a value of 0 at a position where the remainder when the following equation (3) is divided by 2π is less than π, and a value π at a position where the remainder is π or more. It has been

  If the laser light output from the objective lens 60 is ideal convergent light, and the condensing position is a space between the objective lens 60 and the surface of the object 9, the laser light at the condensing position is The light collection area is narrow. However, even if the laser light output from the objective lens 60 is ideal convergent light, when the laser light is condensed inside the object 9, the condensing region of the laser light at the condensing position is Extends in the direction of the optical axis. This will be described in more detail below.

FIG. 4 is a diagram illustrating a state in which laser light is condensed inside the object 9. As shown in the figure, the refractive index of the space between the objective lens 60 and the surface of the object 9 and n _1, the refractive index of the object 9 and n _2. At this time, when the light passes through the boundary surface between the object 9 and the space having different refractive indexes, the light is refracted according to Snell's law expressed by the following equation (4). Here, θ ₁ is an incident angle, and θ ₂ is a refraction angle.

As shown in FIG. 5, due to refraction according to Snell's law, the condensing position of the light beam L ₁ having a large incident angle passing through the periphery of the objective lens 60 has a small incident angle passing near the center of the objective lens 60. It deviates greatly from condensing position by the paraxial ray L _2. As a result, the condensing region extends in the optical axis direction as shown in FIG. This deviation is called spherical aberration. When processing is performed in such an extended condensing region, compared to the case where there is no aberration, a strong light amount is required, or the processed portion extends in the optical axis direction.

  The amount of spherical aberration varies depending on the depth d of the internal focusing position. The spherical aberration Δs of a light beam that is separated from the optical axis by a distance h is expressed by the following equation (5). From this equation, it can be seen that the spherical aberration is proportional to the depth d, and that the amount of spherical aberration increases as the depth increases. Further, the wavefront aberration E (h) is expressed by the following equation (6) using the equation (5). Here, h is the height of the light beam in the objective lens 60 (distance from the optical axis).

  If the spherical aberration is increased, the amount of laser light must be increased for processing, or a condensing region is formed extending in the optical axis direction. In particular, it is not preferable for the optical integrated circuit to be formed that the condensing region is extended in the optical axis direction.

Therefore, in the present embodiment, the control unit 32 corrects the converging holograms φ _A and φ _B for condensing the laser light at each condensing position and the aberration of the laser light corresponding to each condensing position. For this purpose, a hologram on which correction holograms φ A — _SACP and φ _{B — SACP} are superimposed is presented to the spatial light modulator 30. The correction hologram φ _{A_SACP} corrects the wavefront aberration at the time of condensing the laser beam at the condensing position A inside the object 9 by the condensing hologram φ _A (the above formula (2a)). Further, the correction hologram φ _{B_SACP} corrects the wavefront aberration at the time of condensing the laser light at the condensing position B inside the object 9 by the condensing hologram φ _B (the above formula (2b)). is there.

In the optical system of the laser light irradiation apparatus 1 shown in FIG. 1, the focal length of the hologram component representing the Fresnel lens pattern in the hologram presented in the spatial light modulator 30 is f _FLP, and the focal length of the objective lens 60 is f Assuming that _object is M and the magnification of the 4f optical system including the lens 41 and the lens 42 is M, the total combined focal length f _result is expressed by the following equation (7). The magnification M of the 4f optical system is determined by the ratio of the focal lengths of the lens 41 and the lens 42.

As can be seen from this equation, if the focal length f _FLP by the hologram component representing the Fresnel lens pattern among the holograms presented to the spatial light modulator 30 is different, the total combined focal length f _result is also different. Therefore, the correction hologram phi _{A_SACP} according to the synthetic focal length of the converging hologram phi _A is created, The correction hologram phi _{B_SACP} according to the synthetic focal length of the converging hologram phi _B is created. The correction holograms φ _{A_SACP} and φ _{B_SACP} can be _created by _setting the wave front of the laser light before entering the objective lens 60 as a wave front opposite to the wave front aberration E (h) expressed by the above equation (6). . A more preferable method for creating correction holograms φ _{B_SACP} and φ _{B_SACP} will be described later.

The hologram φ _result to be presented to the spatial light modulator 30 is created according to the following equation (8). That is, a phased method (the above (1) is obtained by adding the condensing hologram φ _A and the correcting hologram φ _{A_SACP} and adding the condensing hologram φ _B and the correcting hologram φ _{B_SACP.} The hologram φ _result to be presented to the spatial light modulator 30 is created by being synthesized by (). Note that the spatial light modulator 30 may be presented by adding a distortion common to both (for example, the distortion of the spatial light modulator 30) to the hologram φ _result .

When the distance between the condensing position A and the condensing position B along the optical axis direction is relatively short, a correction hologram according to the average value of the combined focal length in each of the condensing positions A and B A _{φφ CPCP} and a hologram φ _result to be presented to the spatial light modulator 30 may be generated according to the following equation (9). That is, φ _temp in which the condensing hologram φ _A and the condensing hologram φ _B are synthesized by the phasing method (formula (1)) is created (formula (9a)), and the created _φtemp and By adding the correction hologram φ _SACP (equation (9b)), a hologram φ _result to be presented to the spatial light modulator 30 is created. In this case as well, the spatial light modulator 30 may be presented by adding distortion common to both to the hologram φ _result .

  When cutting the object 9 such as glass or a silicon wafer, if the modified layer is formed by condensing the laser beam inside the object 9, the modified layer is positioned at a deeper position. When the light is condensed, the modified layer is formed. Therefore, it is preferable to form the modified layer in order from a deep position. The same applies when converging and irradiating a plurality of condensing positions with laser light. Therefore, when condensing and irradiating laser light to a plurality of condensing positions, it is desirable to process the light as if it were one line extending in the depth direction by bringing the condensing positions closer to each other.

When a femtosecond laser light source is used as the laser light source 10, it is not possible to use a four optical system composed of convex lenses. In this case, the spatial light modulator 30 and the objective lens 60 are not in an imaging relationship with each other, and the combined focal length f _result is expressed by the following equation (10). Here, Δ is the optical path length between the spatial light modulator 30 and the objective lens 60. M is a magnification when a reduction optical system composed of a concave-convex lens is used. The actual condensing position is expressed by the following equation (11). A correction hologram is created from these formulas (1) and (11), and a hologram φ _result to be presented to the spatial light modulator 30 is created according to the formula (8) or (9).

Next, a more preferable method for creating correction holograms φ _{A_SACP} , φ _{B_SACP} , φ _SACP will be described. FIG. 6 is a diagram for explaining a method of creating a correction hologram. In the figure, the objective lens 60 and the object 9 are close to each other by a distance d with reference to the case where the laser beam is focused on the surface of the object 9 when no correction is made. Condensation position O ′ when the condensing position exists inside the object 9 and is corrected with respect to the condensing position O when the condensing position exists outside the object 9 and is not corrected. Differ by a distance Δ.

When a condensing position exists outside the object 9 and correction is not performed, the incident angle of a light beam separated from the optical axis by the distance h in the objective lens 60 is θ. Further, when the condensing position exists inside the object 9 and correction is performed, a light beam separated from the optical axis by the distance h in the objective lens 60 is incident on the surface of the object 9 at an incident angle θ ₂ . refracted at refraction angle theta ₁ at the object 9 surface. Distance from the optical axis when the light beam is incident on the object 9 surface is h _1.

There is a relationship of the following equation (12) between these parameters. From this equation (12), θ ₁ and θ ₂ are expressed by other parameters. In addition, the light collection position when the light collection position exists outside the object 9 and correction is not performed, and the light collection position O is corrected when the light collection position exists inside the object 9 and is corrected. The optical path length change OPD of O ′ is expressed by the following equation (13). Correction holograms φ _{A_SACP} , φ _{B_SACP} , φ _SACP are created based on the optical path length change OPD expressed by the equation (13).

FIG. 7 is a diagram showing a phase modulation amount distribution in a correction hologram created as a wavefront opposite to the wavefront aberration E (h) expressed by the equation (6). FIG. 8 is a diagram showing a phase modulation amount distribution in the correction hologram created based on the optical path length change OPD expressed by the equation (13). In any case, f _result is 4 mm, the refractive index n of the object 9 is 1.48, NA (= sin θ) is 0.8, and (d + Δ) is 1.34 mm. In FIG. 7, d is 0.9 mm and Δ is 0.44 mm. In FIG. 8, d is 0.81 mm and Δ is 0.53 mm.

  As shown in FIG. 7, the correction hologram created as a wavefront opposite to the wavefront aberration E (h) expressed by the equation (6) requires a large amount of phase modulation, resulting in spatial light modulation. The demand for the resolution of the vessel 30 is high. On the other hand, as shown in FIG. 8, the correction hologram created based on the optical path length change OPD expressed by the equation (13) requires a smaller amount of phase modulation, and thus more accurate. Aberration correction is possible.

  The distance Δ appearing in the above equations (12) and (13) is determined as follows. That is, the phase range in which the spatial light modulator can express the phase difference between the phase modulation amount at any pixel on the spatial light modulator corresponding to the incident portion of the condenser lens and the phase modulation amount at the pixel adjacent to the pixel. It needs to be as follows. Specifically, in the range of 0 <Δ <Δs, the phase modulation amount in an arbitrary pixel on the spatial light modulator 30 corresponding to the incident portion of the objective lens 60, and the phase modulation amount in a pixel adjacent to this pixel The moving amount d of the target object and the condensing point shift amount Δ are set so that the phase difference between the two becomes less than 2π. In this case, the calculation reference for d and Δ includes a PV (peak to valley) value, an RMS (Root Mean Square) value, and the like of the correction wavefront. Thereby, the amount of movement of the object 9 is such that the irradiation position is located within an aberration range (a range larger than n × d and smaller than n × d + Δs from the incident surface of the object) generated in the object 9. d and the condensing point shift amount Δ are set. Note that the following expression (14) must be satisfied. It is possible to reduce the effective laser incident size by limiting the diameter of the laser light incident on the objective lens 60.

  FIG. 9 is a flowchart showing the procedure of the laser beam irradiation method according to the present embodiment. First, the light collection position is set on the surface of the object 9 without wavefront correction, and this position is set as the origin. Next, a condensing position (distance (d + Δ) from the surface) inside the object 9 is set, and a condensing hologram is created. Further, d and Δ satisfying the above equation (14) are determined. At this time, as a reference for determining d and Δ, the PV value of the phase modulation amount distribution in the correction hologram or the amount of change in the phase difference from the phase modulation amount in the pixel adjacent to the pixel is used. That is, d and Δ are set such that the phase difference between adjacent pixels is less than or equal to the maximum phase modulation amount of the spatial light modulator in the range of 0 <Δ <Δs.

Then, a correction hologram is created based on the equation (13), and a hologram φ _result is created according to the equation (8) or (9). The hologram φ _result is presented to the spatial light modulator 30. The The object 9 is moved in the direction of the objective lens 60 by the distance d, the laser light output from the laser light source 10 is started, and the laser light is condensed and applied to a predetermined condensing position inside the object 9. When the required irradiation time ends, the laser light output from the laser light source 10 is stopped. When there is another condensing position, the same processing is repeated from the setting of the condensing position (distance (d + Δ) from the surface) inside the object 9. Note that the focal point can be moved by changing the relative position between the object and the objective lens, so the objective lens may be moved, or both the object and the objective lens may be moved.

  Next, a description will be given of results of an experiment performed for confirming a light collection state by the laser light irradiation apparatus and the laser light irradiation method according to the present embodiment. FIG. 10 is a configuration diagram of the laser beam irradiation apparatus 1A used in this confirmation experiment. The laser beam irradiation apparatus 1A shown in FIG. 10 further includes an objective lens 70 and an imaging unit 80 in addition to the configuration shown in FIG. The optical axis of the objective lens 70 is orthogonal to the optical axis of the objective lens 60. The imaging unit 80 images the state of light collection by the objective lens 60 via the objective lens 70. Here, an acrylic plate was used as the object 9, and the laser light was focused at two positions having different depths. The imaging results by the imaging unit 80 are shown in FIGS.

  FIG. 11 and FIG. 12 are diagrams showing a state of condensing when laser light is condensed at two positions different from each other by a depth of 50 μm. FIG. 11 shows how light is condensed when spherical aberration correction is not performed. FIG. 12 shows the state of light collection when spherical aberration correction is performed by the above equation (9). As can be seen by comparing the two figures, the spherical aberration correction is performed at each of the two condensing positions, thereby reducing the expansion of the condensing region in the optical axis direction.

  FIG. 13 to FIG. 15 are diagrams showing how light is condensed when the laser light is condensed at two different positions with a depth of 200 μm. FIG. 13 shows how light is condensed when spherical aberration correction is not performed. FIG. 14 shows how light is condensed when spherical aberration correction is performed according to the above equation (9). FIG. 15 shows how light is condensed when spherical aberration correction is performed according to the above equation (8). As can be seen by comparing these figures, the spherical aberration correction is performed at each of the two condensing positions, thereby reducing the extension of the condensing region in the optical axis direction. In particular, when the spherical aberration correction is performed by the above equation (8), the extension of the light collection region in the optical axis direction is sufficiently reduced.

In this way, a good condensing point shape is realized by using the correction holograms φ _{A_SACP} and φ _{B_SACP} (or φ _SACP ) for wavefront aberration correction in consideration of the combined focal length f _result. Has been. By performing processing using such a good condensing point shape, the problems of the light amount and the processing shape that have been problems are solved, and the processing time can be shortened by multi-point processing.

  Next, the result of another experiment performed for confirming the light collection state by the laser beam irradiation apparatus and the laser beam irradiation method according to the present embodiment will be described. FIG. 16 is a configuration diagram of the laser beam irradiation apparatus 2 used in this confirmation experiment. The laser beam irradiation apparatus 2 shown in this figure includes a laser light source 10, a spatial filter 110, a collimator lens 120, an aberration plate 130, a lens 141, a lens 142, a spatial light modulator 30, a lens 151, a lens 152, and a Fourier transform lens. 160 and an imaging unit 170. The aberration plate 130 can be freely inserted and removed from the optical path, the amount of aberration is known, and various aberrations such as spherical aberration, astigmatism, and coma are included.

  In this laser light irradiation device 2, the laser light output from the laser light source 10 passes through the spatial filter 110, then is collimated by the collimating lens 120, passes through the imaging optical system composed of the lens 141 and the lens 142, and passes through the spatial light. Input to the modulator 30. The laser light input to the spatial light modulator 30 is phase-modulated in each of the plurality of pixels of the spatial light modulator 30, passes through an imaging optical system including a lens 151 and a lens 152, and is collected by a Fourier transform lens 160. As a result, the imaging surface of the imaging unit 170 is reached. The imaging results by the imaging unit 170 are shown in FIGS.

As the condensing holograms φ _A and φ _B presented in the spatial light modulator 30, a hologram representing a character string “HPK” as a set of discrete condensing points was prepared. The condensing ranges of the laser beams by the condensing holograms φ _A and φ _B are different from each other. It is assumed that there is no aberration plate 130 on the optical path, and a hologram φ ₁ is created by synthesizing these converging holograms φ _A and φ _B by a phasing method according to the following equation (15), and this hologram φ ₁ is a space: Presented to the light modulator 30. FIG. 17 is a diagram illustrating a state of light collection imaged by the imaging unit at this time. As shown in this figure, in the state where there is no aberration plate 130 on the optical path, each condensing point representing the character string “HPK” by the condensing holograms φ _A and φ _B was clearly obtained. However, in the state where the aberration plate 130 is inserted on the optical path, each condensing point representing the character string “HPK” by the condensing holograms φ _A and φ _B is unclear.

Subsequently, the hologram phi ₂ is created by the following equation (16). That is, the correction hologram φ _{A_SACP} is superimposed only on the condensing hologram φ _A. This hologram φ ₂ was presented to the spatial light modulator 30. FIG. 18 shows a state of condensing captured by the imaging unit when the aberration plate 130 is on the optical path at this time. As shown in this figure, in a state where the optical path is aberration plate 130, each converging point representing a string of by "HPK" the converging hologram phi _A is obtained clearly, hologram condensed each focal point representing a string of by "HPK" to φ _B was unclear. On the other hand, FIG. 19 shows a state of condensing imaged by the imaging unit when there is no aberration plate 130 on the optical path. As shown in this figure, in the absence of aberration plate 130 on the optical path, each converging point representing a string of by "HPK" the converging hologram phi _B is obtained clearly, hologram condensed each focal point representing a string of "HPK" According to the φ _a was unclear.

  From the above results, it can be seen that the aberration correction holograms act independently in the laser beam irradiation apparatus and the laser beam irradiation method according to the present embodiment.

It is a block diagram of the laser beam irradiation apparatus 1 which concerns on this embodiment. It is a figure which shows a mode that a laser beam is condensed on two condensing positions A and B inside the target object. It is a figure which shows the phase modulation distribution in a Fresnel lens pattern. It is a figure which shows a mode that a laser beam is condensed inside the target object. It is a figure which shows a mode that a laser beam is condensed inside the target object. It is a figure explaining the preparation method of the hologram for correction | amendment. It is a figure which shows phase modulation amount distribution in the hologram for a correction produced as what has a wave front contrary to the wave aberration E (h) represented by (6) Formula. It is a figure which shows phase modulation amount distribution in the hologram for a correction produced based on optical path length change OPD represented by (13) Formula. It is a flowchart which shows the procedure of the laser beam irradiation method which concerns on this embodiment. It is a block diagram of laser beam irradiation apparatus 1A. It is a figure which shows the result of the confirmation experiment using 1 A of laser beam irradiation apparatuses. It is a figure which shows the result of the confirmation experiment using 1 A of laser beam irradiation apparatuses. It is a figure which shows the result of the confirmation experiment using 1 A of laser beam irradiation apparatuses. It is a figure which shows the result of the confirmation experiment using 1 A of laser beam irradiation apparatuses. It is a figure which shows the result of the confirmation experiment using 1 A of laser beam irradiation apparatuses. 1 is a configuration diagram of a laser light irradiation device 2. FIG. It is a figure which shows the result of the confirmation experiment using the laser beam irradiation apparatus. It is a figure which shows the result of the confirmation experiment using the laser beam irradiation apparatus. It is a figure which shows the result of the confirmation experiment using the laser beam irradiation apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,1A ... Laser beam irradiation apparatus, 9 ... Object, 10 ... Laser light source, 20 ... Prism, 30 ... Spatial light modulator, 31 ... Drive part, 32 ... Control part, 41, 42 ... Lens, 50 ... Mirror, 60 ... Objective lens (condensing optical system), 70 ... Objective lens, 80 ... Imaging unit.

Claims (4)

An apparatus for condensing and irradiating laser light to a plurality of condensing positions inside an object,
A laser light source for outputting laser light;
A phase modulation type that inputs laser light output from the laser light source, presents a hologram that modulates the phase of the laser light in each of a plurality of two-dimensionally arranged pixels, and outputs the laser light after the phase modulation A spatial light modulator of
A condensing optical system for condensing the laser light output from the spatial light modulator at the plurality of condensing positions;
A hologram in which a condensing hologram for condensing laser light at each of the plurality of condensing positions and a correction hologram for correcting aberration of the laser light corresponding to each of the plurality of condensing positions are superimposed A control unit for presenting the spatial light modulator,
A laser beam irradiation apparatus comprising: When the condensing position exists outside the object and the correction position is not corrected, the control section collects the focusing position when the focusing position exists inside the object and is corrected. Based on the change in the optical path length of the light position, the correction hologram is set.
The laser beam irradiation apparatus according to claim 1. A method of condensing and irradiating laser light to a plurality of condensing positions inside an object,
A laser light source for outputting laser light;
A phase modulation type that inputs laser light output from the laser light source, presents a hologram that modulates the phase of the laser light in each of a plurality of two-dimensionally arranged pixels, and outputs the laser light after the phase modulation A spatial light modulator of
A condensing optical system for condensing the laser light output from the spatial light modulator at the plurality of condensing positions;
Using,
A hologram in which a condensing hologram for condensing laser light at each of the plurality of condensing positions and a correction hologram for correcting aberration of the laser light corresponding to each of the plurality of condensing positions are superimposed To the spatial light modulator,
And a laser beam irradiation method. The optical path length of the condensing position when the condensing position exists inside the object and is corrected with respect to the condensing position when the condensing position exists outside the object and is not corrected. Based on the change, the correction hologram is set.
The laser beam irradiation method according to claim 3.