JP2007132761A - Confocal type signal light detection device and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To extract precisely signal light generated from a portion to be measured inside an object, and to measure relative signal light intensity. <P>SOLUTION: The portion A1 to be measured inside the measuring object A is irradiated with measuring light, and only information of the signal light generated from the portion A1 to be measured by the measuring light is detected. This device includes an optical fiber 51 for irradiating the portion A1 to be measured with the measuring light from one end and receiving reflected light including the signal light from one end, a lens 58 for condensing the measuring light and the reflected light, a holder 57 for keeping a confocal by fixing one end of the optical fiber 51 and a relative position with the lens 58, a vibration mechanism 59 for changing the focal position of the measuring light by the optical fiber 51 by moving the holder 57 as long as a prescribed distance in the light axis direction, and a measuring device 7 for measuring light intensity of the reflected light of the optical fiber 51. The device also includes a signal light extraction means 75 for extracting the relative light intensity of the signal light based on a light intensity change of the reflected light when moving the focal position of the measuring light in the light axis direction. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention provides a confocal signal light detection device that extracts only signal light information generated from a measurement site when the measurement site exists inside the object and the measurement beam is irradiated with the measurement light in a confocal state. And a confocal signal light detection method.

  2. Description of the Related Art Conventionally, confocal signal light detection devices have been used in scanning confocal microscopes and the like that measure the surface shape of an object in a non-contact manner (see, for example, Patent Document 1). The scanning confocal microscope described in Patent Document 1 includes an incident optical system for making light incident on an optical fiber, and condensing the light emitted from the end face of the optical fiber on the sample surface and at the same time reflecting it from the sample surface. A confocal optical system that collects light on the end face of the optical fiber and returns it to the optical fiber, a lens that focuses the emitted light and reflected light, a branching optical system that extracts the reflected light from the optical fiber, and the extraction An electric system that converts light into an electric signal by a photodetector and performs signal processing, and detects a deviation of the sample surface with respect to the focal position of the confocal optical system based on the amount of light extracted from the branch optical system. The focusing microscope includes actuator means for moving the end face of the optical fiber facing the confocal optical system in the optical axis direction, and only the optical fiber is moved in the optical axis direction by the actuator means. By performs focusing of the light emitted from the optical fiber end face, it has been made as to observe the surface shape or step or the like of the sample surface.

When a confocal signal light detector is used as a microscope in this way, the reflected light can be received most strongly by the photodetector when the emitted light is focused on the surface of the sample. It is excellent in that the surface shape can be measured with high resolution.
Japanese Patent Laid-Open No. 5-203445

  However, although the confocal microscope described in Patent Document 1 is excellent in observing the surface shape or the like of an object (sample), there is a problem that it is difficult to observe a state inside the object, such as a crack. there were. That is, in this confocal microscope, the emitted light from the optical fiber is greatly attenuated by scattering when entering the inside of the object, and the signal light to be observed is very small because the reflection coefficient at the measurement site is small. In addition, the emitted light diffuses inside the object, the diffused light appears on the object surface, and enters the end face of the optical fiber together with the signal light. Of the incident reflected light, the signal light becomes diffused light. There was a problem that the signal light could not be measured accurately after being buried.

  An object of the present invention is to provide a confocal signal light detection device and the like that can accurately extract signal light generated from the measurement site and measure relative signal light intensity.

  As a result of earnest research, the present inventor hardly changes the intensity of diffused light appearing on the object surface even if the irradiation position is moved in the optical axis direction with the relative position of the measurement light irradiation position and the lens fixed. It came to know this, and it came to complete this invention paying attention to this knowledge.

  That is, in order to solve the above-described problem, the confocal signal light detection device according to the present invention irradiates measurement light to a measurement site inside an object, and only information on signal light generated from the measurement site by the measurement light. A confocal signal light detecting device that detects the reflected light including the signal light from one end and irradiating the measurement site from one end with the measurement light, and the measurement A lens that focuses light and the reflected light, a holder that holds the confocal by fixing the relative position of one end of the optical fiber and the lens, and the holder is moved by a predetermined distance in the optical axis direction. A moving means for changing the focal position of the measurement light by the optical fiber; and a photodetector for measuring the light intensity of the reflected light of the optical fiber, wherein the focal position of the measurement light is determined in the optical axis direction. It is characterized in that the signal light extracting means for extracting the relative light intensity of the signal light is provided on the basis of a change in light intensity of the reflected light when moving to.

  According to the present invention, since the relative position of the one end of the optical fiber and the lens is fixed by the holder, a confocal state under substantially the same condition can be maintained even if the holder is moved in the optical axis direction. . In this way, when the confocal state under substantially the same conditions is maintained, the light intensity of the diffused light emitted from the object surface is considered to be substantially the same before and after the movement of the holder. Therefore, based on the change in the light intensity of the reflected light when the focal position of the measurement light is moved in the optical axis direction, that is, the difference in light intensity at two points shifted in the optical axis direction or the continuous light intensity. By calculating the rate of change, the light intensity component based on the diffused light can be removed from the light intensity of the reflected light received from one end of the optical fiber, and only the information related to the signal light can be extracted. .

  That is, when the signal light is not received by the optical fiber, the difference or change rate is 0 because the signal light component is not included in the reflected light. On the other hand, at the boundary where the signal light is received by the optical fiber, if the focal position is moved while the confocal state is maintained by the moving means, the light intensity of the diffused light is substantially constant, so the influence of only the signal light component is reflected. Appears in the light intensity. However, since this signal light component is very small, it is not possible to extract information on the signal light as it is buried in the diffused light component. Therefore, by calculating the difference or derivative (change rate) of the light intensity of the reflected light before and after the movement of the holder by the moving means, the diffused light component is removed (or ignored), and the change or change rate of the signal light is The relative light intensity of the signal light that has been calculated can be extracted.

  That is, according to the present invention, the relative light intensity of the signal light can be extracted also from the measurement site inside the object, and the state of the shape and the like inside the object can be accurately grasped.

  Specifically, for example, the signal light extraction unit determines the light intensity of the reflected light when the focus position of the measurement light is set to a predetermined position and the focus position of the measurement light from the predetermined position in the optical axis direction. Is configured to extract the relative light intensity of the signal light based on the difference from the light intensity of the reflected light when adjusted to a position deviated by the distance, or the signal light extraction means, It is preferable that the relative light intensity of the signal light is extracted by calculating the rate of change of the light intensity of the reflected light of the measurement light (claims 2 and 3).

  The signal light extraction means may extract the relative light intensity of the signal light as it is, but is preferably configured to amplify the relative light intensity of the extracted signal light. ).

  That is, even if the relative light intensity of the signal light can be extracted, since the relative light intensity is very small, accurate measurement may be difficult due to noise or the like. Here, in the present invention, since only the relative light intensity of the signal light is extracted, only this signal light component can be amplified. Therefore, by amplifying only this signal light component, only information relating to the light intensity of the signal light can be extracted more accurately.

  The moving distance of the holder by the moving means is not particularly limited, and may be, for example, a substantially half value half width in a point image response function when the measurement light is irradiated on the surface of the object to be measured. The moving distance of the holder by the moving means is preferably substantially full width at half maximum in the point image response function when the measurement light is irradiated onto the surface of the object to be measured (Claim 5).

  With this configuration, it is possible to suppress the influence of reflected light or the like based on the part inside the object other than the part to be measured, and to suppress the influence due to the attenuation in the object, and more accurate relative signal light. The light intensity can be detected.

  In this invention, the moving means vibrates the holder in a minute range along the optical axis direction, and changes the relative distance between the center of amplitude and the object to be measured beyond the minute range in the optical axis direction. It is preferable to be configured as described above (claim 6). The moving means may be configured integrally with the vibrating means for vibrating the holder and the sliding means for moving the holder beyond the minute range, or may be configured as a separate body. May be.

  With this configuration, it is possible to extract the relative light intensity of the signal light at each depth (length in the optical axis direction) inside the object while microvibrating, and the object surface of the measurement site that emits the signal light The depth from can be measured.

  The numerical aperture of the lens is not particularly limited, but the numerical aperture of the lens is preferably set to 0.5 or more (Claim 7).

  If comprised in this way, the full width at half maximum can be narrowed, and the relative light intensity of signal light as large as possible can be extracted while shortening the moving distance of the holder by the moving means.

  Further, the confocal signal light detection method according to the present invention irradiates the measurement site inside the object with the measurement light, and only the information of the signal light generated from the measurement site by the measurement light is obtained inside the object by the measurement light. A confocal signal light detection method for extracting from reflected light, the first reflected light measurement for measuring the light intensity of reflected light when the focus position of the measurement light in a confocal state is set to a predetermined position Step and the focus position of the measurement light while maintaining the confocal state in the first reflected light measurement step, the reflected light in the case where the focal position of the measurement light is adjusted to a position deviated from the predetermined position in the optical axis direction by a predetermined distance. A relative reflected light intensity of the signal light based on a second reflected light measurement step for measuring the light intensity and a change in the light intensity of the reflected light measured by the first and second reflected light measurement steps. It is characterized in that and a signal light extracting a (claim 8).

  Also according to these inventions, the relative light intensity of the signal light can be reliably extracted as in the confocal signal light detection device.

  Specifically, in the signal light extraction step, the signal is based on a difference between the light intensity measured by the first reflected light measurement step and the light intensity measured by the second reflected light measurement step. The relative light intensity of light is extracted (claim 9), or the reflected light is continuously measured while maintaining the confocal state between the first and second reflected light measurement steps. In the signal light extraction step, the relative light intensity of the signal light is extracted by calculating the light intensity change rate of the reflected light when the focus position of the measurement light is moved (claim) Item 10).

  According to the confocal type signal light detection apparatus and the like of the present invention, it is possible to maintain the confocal state under substantially the same condition before and after the movement of the focus position of the measurement light accompanying the movement of the holder by the moving means. The light intensity of light other than signal light such as diffused light before and after can be made substantially constant. Accordingly, there is an advantage that the light intensity component due to the diffused light or the like can be removed based on the change in the light intensity of the reflected light before and after the movement, and only the information related to the signal light can be extracted. For this reason, if this confocal signal light detection device is used as a confocal microscope, for example, a measurement site inside the object, such as an internal crack, can be observed based on the relative light intensity.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing a confocal signal light detection device.

  The confocal type signal light detection device 3 irradiates measurement light to the measurement site inside the object and reflects only the signal light information (relative light intensity) generated by the measurement light being reflected by the measurement site. Extracted from reflected light including diffused light. In the present embodiment, position detection for detecting the position of the measurement target portion A1 by irradiating the measurement target object A with the measurement light and detecting the signal light reflected by the measurement target portion A1 such as a crack. It is configured as a device.

  Specifically, the confocal signal light detection device 3 irradiates the measurement object A with measurement light on the pedestal 4 for placing and fixing the measurement object A, and in the confocal state A confocal optical system 5 that receives the reflected light from the measurement light, and a measurement that measures the reflected light detected by the confocal optical system 5 and extracts the relative intensity of the signal light based on the light intensity of the reflected light. Device 7.

  The pedestal portion 4 is supported by the moving device 9 and is configured to be movable back and forth and to the left and right, and is configured to be movable up and down. Accordingly, the pedestal portion 4 can be moved by driving the moving device 9, whereby the focus position of the measurement light is moved not only in the X and Y directions in FIG. 1 but also in the Z direction (optical axis direction). Can be made. That is, the moving device 9 changes the relative distance and position between the measurement target A and the holder 57 along each axis, and the moving distance is set to be larger than the depth of focus described later.

  The confocal optical system 5 is configured to irradiate the measurement object A with the measurement light and to receive reflected light from the measurement light at an irradiation position of the measurement light. The irradiation / light receiving unit will be described later. By being configured by one end face of the optical fiber 51, a confocal state is formed, and the amount of light received at the focal position of the measurement light is increased. Specifically, the confocal optical system 5 includes an optical fiber 51 branched by interposing a coupler 55, a head 52 disposed at one end 51a of the optical fiber 51, and the optical fiber 51. And a light source unit 53 connected to one of the branch end portions 51 b, and the measuring device 7 is connected to the other end 51 c of the branch end portion of the optical fiber 51. The confocal optical system 5 irradiates the measurement object A with the measurement light generated in the light source unit 53 through the optical fiber 51 from the end face of the one end 51a, and reflects the reflected light from the measurement light into the light. Light is received at the end face of the one end 51 a of the fiber 51, separated by the coupler 55, and guided to the measuring device 7.

  The optical fiber 51 is a known flexible fiber in which a cladding layer and a covering portion are provided around the core. Although not shown in FIG. 1, the optical fiber 51 is formed relatively long. Therefore, the head 52 provided at the one end 51 a of the optical fiber 51 is configured to be relatively free to move with respect to the light source unit 53 and the measuring device 7. One end 51a of the optical fiber 51 passes through an upper surface wall of a housing 56, which will be described later, of the head 52, and an end surface thereof is placed below a holder 57 (described later) of the head 52 below (to be measured). It is fixed in a state of being oriented in the direction of the object A).

  The head 52 holds one end 51a of the optical fiber 51 and holds an objective lens 58 for focusing the measurement light emitted from the optical fiber 51 and the reflected light from the measurement light. A vibration mechanism 59 is provided that vibrates both of the end faces of the one end portion 51a of the fiber 51 and the objective lens 58 in the vertical direction of the measurement light, that is, along the optical axis direction. .

  Specifically, the head 52 includes a bottomed cylindrical housing 56 opened on one side in the optical axis direction (downward in FIG. 1), a vibration mechanism 59 disposed on the upper surface wall of the housing 56, A holder 57 that is vibrated in the direction of the optical axis by the vibration mechanism 59 and an objective lens 58 held by the holder 57 are provided, and the end portion 51 a of the optical fiber 51 is fixed to the holder 57. The relative position with respect to the objective lens 58 is fixed and the confocal state is maintained, and the holder 57 is vibrated by a vibration mechanism 59 with a predetermined amplitude (between the position F1 and the position F2) to be described later. It is configured to vibrate while maintaining the focus state. In FIG. 1, this amplitude is shown to be relatively large for convenience of explanation, but in reality, it is set to a very small distance as will be described later.

  The holder 57 is formed in a substantially U-shaped cross section, and the one end portion 51a of the optical fiber 51 is inserted through and fixed to the upper portion of the holder 57, and is separated from the end surface of the one end portion 51a of the optical fiber 51. An objective lens 58 is held on the inner periphery. The holder 57 is supported on the upper surface wall of the housing 56 by a guide rail 60 protruding in the optical axis direction (downward in FIG. 1) so as to be vertically movable. The guide rail 60 can be omitted as appropriate, but the guide rail 60 is preferably provided in order to vibrate the holder 57 accurately along the optical axis direction.

  As described above, the objective lens 58 focuses the measurement light emitted from the end surface of the one end portion 51 a of the optical fiber 51, and focuses the reflected light from the measurement light to the end surface of the one end portion 51 a of the optical fiber 51. It is intended to receive light. The numerical aperture of the objective lens 58 is not particularly limited, but is set to 0.5 or more in order to reduce the full width at half maximum of the point image response function of the signal light by the measurement light focused by the lens 58. On the other hand, if the numerical aperture is too large, the depth of focus becomes shallow, so it is preferably set within a range of 0.5 to 1.0, for example. When the full width at half maximum of the signal light is thus narrowed, the amplitude of the vibration mechanism 59 described below can also be reduced, and the vibration mechanism 59 can be formed in a compact manner.

  The vibration mechanism 59 is configured to vibrate a probe (not shown) up and down (in the optical axis direction) using a piezoelectric element, and when the probe is connected to the holder 57, the holder 57 is moved to the guide rail 60. Are made to vibrate along the optical axis direction at a constant cycle. When the holder 57 vibrates, the focus position F of the measurement light also vibrates as shown in FIG. The amplitude center Zp of the focal position F is moved along the optical axis when the pedestal 4 is moved in the vertical direction by the moving device 9. That is, the focus position F of the measurement light moves with the movement of the amplitude center Zp, and the holder 57 vibrates between the uppermost point F1 and the lowermost point F2 that move with the movement of the amplitude center Zp. It has been made.

  The vibration period of the holder 57 by the vibration mechanism 59 is not particularly limited, but is set to an appropriate range in order to use a lock-in amplifier as the amplifier 72 described later. The amplitude a by the vibration mechanism 59 is appropriately set in consideration of the focal depth df (see FIG. 2). That is, as will be described later, the measuring device 7 calculates the relative light intensity of the signal light based on the difference in the light intensity of the reflected light at the uppermost point F1 and the lowermost point F2 (see FIG. 2) at the amplitude a. It is configured to extract. Therefore, if the amplitude a is increased and the difference in light intensity between the point where the reflected light includes the signal light and the point where the reflected light does not include the signal light at all is calculated, this difference appears remarkably. However, if the amplitude of the vibration mechanism 59 is increased too much in order to increase this difference, the measurement light may be reflected to a portion other than the portion A1 inside the measurement target A, and signal light may be generated. There is a risk of being easily affected by the attenuation of the measurement light. Therefore, the amplitude a is preferably set to a value slightly larger than the focal depth af of the measurement light.

  Although not illustrated, the head 52 is configured to be grounded and fixed in a relative position with respect to the ground when measuring reflected light. By fixing the head 52 in this way, the relative position between the object A to be measured and the holder 57 can be changed as accurately as possible, and thus the reflected light can be accurately measured.

  The light source unit 53 is a known light source unit configured to allow measurement light generated by the light source to enter the optical fiber 51. For example, the light source unit 53 generates measurement light from a light source configured by a light emitting diode, various lasers, and the like, passes through an interference filter and the like, and enters one of the branch end portions 51b of the optical fiber 51 with a condenser lens It is configured to let you. The light source unit 53 is configured to be irradiated with, for example, He—Ne laser light. The light source unit 53 may be configured to be capable of adjusting the wavelength of the measurement light to be output. In this case, the wavelength of the measurement light is set according to the material of the measurement target A or the like. It can be changed as appropriate.

  On the other hand, the measuring device 7 includes a photodetector (light detector) 71 that converts an optical signal into an electrical signal, an amplifier 72 that amplifies the electrical signal, and a signal light that extracts only information related to the signal light from the amplified signal. An extraction device 75 is provided, and reflected light that has entered from the other end 51 c of the branch end of the optical fiber 51 is converted into an electrical signal by the photodetector 71, and this electrical signal is amplified by the amplifier 72. The amplifier 72 has a so-called lock-in amplifier function, and is configured to pick up a weak signal and amplify the signal.

  As described above, the amplifier 72 is connected to the signal light extraction device 75 that extracts only information related to the signal light from the amplified electrical signal. Although not shown, the signal light extraction device 75 has a CPU, a memory, an interface, and a bus for connecting these units. Various data, programs, and the like are stored in the memory of the signal light extraction device 75, and the CPU 4 executes the data, programs, and the like, thereby controlling the moving device 9 to move the pedestal unit 4. At the same time, the vibration mechanism 59 is operated to store the light intensity of the reflected light in different phases (in this embodiment, the uppermost point and the lowermost point) in the memory, and the difference between the two is calculated, thereby calculating the relative signal light. It is configured to extract an appropriate light intensity. That is, the signal light extraction device 75 functionally includes a control unit of the moving device 9, a control unit of the vibration mechanism 59, and a calculation unit for calculating the relative light intensity of the signal light. .

  The signal light extraction device 75 is connected to various sensors necessary for performing these functions. The signal light extraction device 75 is provided with input means (not shown) such as a keyboard for inputting various settings and data, and a display for displaying information on the relative light intensity of the signal light. Means 76 (eg, liquid crystal display, CRT, etc.) is provided.

  Specifically, the signal light extraction device 75 vibrates the holder 57 by the vibration mechanism 59, reads the light intensity of the reflected light at the highest point and the lowest point of this amplitude from the measurement device 7, and stores each light intensity in the memory. Remember me. The signal light extraction device 75 is configured to call each light intensity stored in the memory and calculate the difference between the two, and this amplitude when the amplitude center is at a predetermined position (depth). The relative light intensity of the signal light at the center is extracted.

  The signal light extraction device 75 is configured to control the operations of the moving device 9 and the vibration mechanism 59, and synchronizes the movement of the base portion 4 by the moving device 9 and the vibration of the holder 57 by the vibration mechanism 59. It is configured to let you. That is, the signal light extraction device 75 is configured to operate the vibration mechanism 59 and drive the moving device 9 in accordance with the operation of the vibration mechanism 59 to move the pedestal portion 4 in the optical axis direction. .

  The pedestal 4 is moved in the Z-axis direction by the moving device 9 so that the relative intensity distribution of the signal light is measured over the depth direction (optical axis direction) of the measurement target A. Yes. The specific operation of the signal light extraction device 75 will be described below together with the signal light extraction method.

  Next, a signal light detection method for detecting the relative light intensity of the signal light using the confocal signal light detection device 3 having the above configuration will be described with reference to FIGS. FIG. 3 is a graph showing a point image response function of measurement light. FIG. 4A is a graph showing the reflectance in the measurement object together with the point image response function of the measurement light, and FIG. 4B is the light intensity detected by the measurement device, When the light intensity of the reflected light when the focus position of the measurement light is set to a predetermined position (position F1) and the focus position of the measurement light are set to a position (position F2) deviating from the predetermined position in the optical axis direction FIG. 4C is a graph showing the difference between the light intensities of the reflected lights.

  By the way, when the measurement light is irradiated into the object A to be measured as described above, most of the measurement light is scattered in the object A to generate stray light as scattered light, and the straight light is to be measured A1. Is reflected to produce signal light. This signal light appears on the surface of the object A to be measured together with the scattered light, and enters the end surface of the one end 51a of the optical fiber 51 together with the scattered light. Since this signal light is extremely smaller than the stray light, it is difficult to extract the signal light as it is. Therefore, the relative light intensity of the signal light is extracted using the confocal signal light detection device 3.

  Specifically, first, the object A to be measured is arranged and fixed on the pedestal portion 4. Then, the moving device 9 is driven to move the pedestal 4 within the XY plane so that the portion A1 to be measured is disposed on the optical axis of the optical fiber 51. Next, the moving device 9 is driven to move the pedestal 4 in the Z-axis direction, and the amplitude center Zp by the vibration mechanism 59 of the focal position F of the measurement light is arranged at a predetermined depth z0 of the object A to be measured. These series of operations are performed by visual observation or by displaying information necessary for these operations on the display means 76.

  When the above preparation is completed and a measurement start switch (not shown) of the signal light detection device 3 is pressed, measurement light as laser light is irradiated from the light source unit 53 to the optical fiber 51, and this measurement light is emitted from the optical fiber 51. The object A to be measured is irradiated from the end face of the one end 51a. At the same time, the holder 57 holding the one end 51a of the optical fiber 51 and the objective lens 58 is vibrated by the vibration mechanism 59 and starts reciprocating. By the reciprocating motion of the vibration mechanism 59, as shown in FIG. 2, the focus position F of the measuring light also reciprocates between the position F1 and the position F2 with the amplitude a around the predetermined position Zp, as shown in FIG. In addition, the point image response function by the measurement light also slides back and forth along the optical axis direction between the function h1 and the function h2. Here, the point image response function h1 is the point image response function of the measurement light when the holder 57 is at the uppermost point F1, and the point image response function h2 is the measurement light when the holder 57 is at the lowermost point F2. Is a point image response function. In FIG. 3A, the vertical axis of the point image response function is not the light intensity but the detection efficiency indicating the light intensity including the attenuation factor.

  The measurement light incident on the measurement target A is reflected with a predetermined reflectance as shown in FIG. This reflectance is large between the position z2 and the position z4 where the portion to be measured A1 exists. That is, when the focus position F is in the measured portion A1, the measurement light is partially reflected as signal light and most of the measurement light is diffused by entering the measurement target A, while When the focal position F is deviated from the measured portion A1, it is diffused by entering the measured object A. These signal light and diffused light appear as reflected light on the surface of the object A to be measured, the reflected light enters the end face of the optical fiber 51, and the light intensity is detected by the measuring device 7.

  More specifically, when the vibration by the vibration mechanism 59 is started, the light intensity of the reflected light is continuously measured by the measuring device 7 and the light of the reflected light when the focus position of the measurement light is at the uppermost point F1. The signal light extraction device 75 reads the intensity from the measurement device 7 and stores the light intensity in the memory of the signal light extraction device 75 (first reflected light measurement step). For example, when the amplitude center Zp of the focus position F of the measurement light is at the position z2 shown in FIG. 4A, the light intensity of the reflected light becomes a value indicated by P1, as shown in FIG. 4B. This value P1 is stored in the memory of the signal light extraction device 75.

  Subsequently, the signal light extraction device 75 reads the light intensity of the reflected light when the focus position of the measurement light is at the lowest point F <b> 2 from the measurement device 7 and stores the light intensity in the memory of the signal light extraction device 75. (Second reflected light measurement step). For example, when the amplitude center Zp of the focus position F of the measurement light is at the position z2 shown in FIG. 4A, the light intensity of the reflected light becomes a value indicated by P2, as shown in FIG. 4B. This value P2 is stored in the memory of the signal light extraction device 75. Needless to say, the first reflected light measurement step and the second reflected light measurement step may be reversed in time series.

  In the signal light extraction device 75, the difference between the light intensity P1 of the reflected light at the uppermost point F1 and the light intensity P2 of the reflected light at the lowest point F2 is calculated, and the relative light intensity of the signal light is calculated. Extraction (signal light extraction step). In the above example, as shown in FIG. 4C, the signal light extraction device 75 calculates the difference value (P2-P1) and stores this value (P2-P1) in the memory of the signal light extraction device 75. .

  On the other hand, when the vibration of the holder 57 by the vibration mechanism 59 is started, the signal light detection device 3 is simultaneously driven by the moving device 9 to raise the pedestal portion 4, whereby the focus position F of the measurement light is changed in the Z-axis direction. Configured to move to. Therefore, by driving the moving device 9, the amplitude center Zp of the focus position F of the measurement light moves from the position z0 to the z6 direction, and the amplitude center Zp is a point (z0 to z0) in the depth direction of the measurement target A. In z6), the light intensity of the reflected light at the uppermost point F1 and the light intensity of the reflected light at the lowermost point F2 are measured, and a difference value between them is calculated. The change in light intensity of the reflected light is shown in FIG. In FIG. 4B, the change in light intensity when the focal position F is at the uppermost point F1 is indicated by a solid line, and the change in light intensity when the focal position F is at the lowest point F2 is indicated by a two-dot chain line. ing.

  In FIG. 4B, the light intensity change is clearly shown for convenience of explanation. However, the change is actually very small, and the change due to the signal light is buried in the diffused light, and the measurement is very difficult. Here, in the signal light extraction device 75, since the holder 57 is vibrated while maintaining the confocal state, the diffused light component included in the light intensity of the reflected light is substantially constant at any point in the vibration path. Conceivable. Therefore, the light intensity component due to the diffused light can be removed by vibrating the holder 57 while maintaining the confocal state and calculating the difference in the light intensity of each reflected light as shown in FIG. 4C. It is possible to extract only the light intensity change of the signal light, that is, the relative light intensity of the signal light. If only this relative light intensity is amplified, only the relative light intensity of this signal light can be clearly measured.

  That is, according to the confocal signal light detection device 3 and the signal light detection method, since the relative position of the one end of the optical fiber 51 and the objective lens 58 is fixed by the holder 57, the holder 57 is moved in the optical axis direction. Even if it is moved, the confocal state under substantially the same condition can be maintained. In this way, when the confocal state under substantially the same conditions is maintained, the light intensity of the diffused light emitted from the surface of the measurement object A is considered to be substantially the same before and after the movement of the holder 57. Therefore, based on the light intensity change when the focus position F of the measurement light is vibrated in the optical axis direction, that is, the light intensity of the reflected light when the focus position F of the measurement light is at the position F1, the measurement light By calculating the difference from the light intensity of the reflected light when the focal position F is at the position F2, the light intensity component based on the diffused light is removed from the light intensity of the reflected light received from one end of the optical fiber 51. It is possible to extract only information relating to signal light.

  That is, when the signal light is not received by the optical fiber 51, the signal light component is not included in the reflected light, so the difference is 0 as shown in FIG. On the other hand, when the focal position F is moved by the vibration mechanism 59 at the boundary where the signal light is received by the optical fiber 51, the confocal state is maintained, so that the influence of only the signal light component appears in the light intensity of the reflected light. . However, since this signal light component is very small, it is not possible to extract information on the signal light as it is buried in the diffused light component. Therefore, by calculating the difference in the light intensity of the reflected light before and after the movement of the holder 57, the diffused light component is removed, the change amount of the signal light is calculated, and the relative light intensity of the signal light can be extracted. it can.

  That is, according to the apparatus 3 and the method, the relative light intensity of the signal light can be extracted also from the measurement target part A1 inside the object, thereby accurately grasping the crack or the like in the measurement target A. be able to.

  In addition, since the head 52 is connected to the measuring device 7 and the light source unit 53 via the optical fiber 51, the head 52 can be easily moved even when it is moved greatly.

  The confocal signal light detection device 3 described above is an embodiment of the device according to the present invention, and the specific configuration of the device can be changed as appropriate without departing from the spirit of the present invention. A modification will be described below.

  (1) In the above embodiment, the holder 57 is vibrated by the vibration mechanism 59, and the light intensity of the reflected light when the focus position F of the measurement light is at the position F1 and the position F2 is measured and extracted. The relative light intensity of the signal light is calculated based on the difference in light intensity. For example, by calculating the differential value of one of the light intensity changes, the signal light The relative light intensity can be calculated. In this case, the light intensity of the reflected light can be measured by a lock-in amplifier method by omitting the vibration mechanism 59 and repeatedly moving the pedestal portion 4 with a predetermined amplitude by the moving device 9.

  (2) In the above embodiment, the relative position between the head 52 and the object A to be measured A is changed by moving the pedestal portion 4 by the moving device 9. , Y and Z axes may be used for movement.

  (3) In the above embodiment, the reflected light reflected by the measurement target portion A1 by irradiating the measurement light is used as the signal light. However, depending on the measurement target A, the excitation light is irradiated as the measurement light, and the measurement target. Fluorescence generated by the portion may be signal light. In this case, as shown in FIG. 5, in the middle of one of the branch ends 51b of the optical fiber 51, the excitation light that extracts only the excitation light having a specific wavelength as the measurement light between the light source unit and the coupler 55 is extracted. A filter 65 is provided, and an absorption filter 66 that transmits only fluorescence is provided between the measuring device and the coupler 55 in the middle of the other branching end 51 c of the optical fiber 51.

It is the schematic which shows the confocal type | mold signal light detection apparatus which concerns on this embodiment. It is explanatory drawing which shows the focus position change of the measurement light by a vibration mechanism. It is explanatory drawing which shows the point image response function of measurement light. It is a figure which shows the relationship between the coordinate of an optical axis direction, the reflectance in a to-be-measured object, the light intensity of reflected light, etc. It is the schematic which shows the modification of a confocal type | mold signal light detection apparatus.

Explanation of symbols

A object to be measured A1 part to be measured 3 confocal signal light detector 5 confocal optical system 7 measuring device 9 moving device (corresponding to an example of moving means)
51 Optical fiber 52 Head 53 Light source 57 Holder 58 Objective lens 59 Vibration mechanism (corresponding to an example of moving means)
71 Photodetector 72 Amplifier 75 Signal Light Extraction Device

Claims (10)

A confocal signal light detection device that irradiates a measurement site inside an object with measurement light and detects only the information of the signal light generated from the measurement site by this measurement light,
An optical fiber that irradiates the measurement light from one end to the measurement site and receives reflected light including the signal light from the one end;
A lens that focuses the measurement light and the reflected light;
A holder for holding a confocal by fixing a relative position between one end of the optical fiber and the lens;
Moving means for changing the focal position of the measurement light by the optical fiber by moving the holder a predetermined distance in the optical axis direction;
A photodetector for measuring the light intensity of the reflected light of the optical fiber,
Signal light extraction means for extracting the relative light intensity of the signal light based on the light intensity change of the reflected light when the focal position of the measurement light is moved in the optical axis direction is provided. A confocal signal light detection device.   In the case where the signal light extraction unit matches the light intensity of the reflected light when the focus position of the measurement light is adjusted to a predetermined position and the focus position of the measurement light is adjusted to a position deviating from the predetermined position in the optical axis direction. The confocal signal light detection device according to claim 1, wherein a relative light intensity of the signal light is extracted based on a difference from the light intensity of the reflected light in the light source.   The signal light extraction unit is configured to extract a relative light intensity of the signal light by calculating a light intensity change rate of the reflected light when the focal position of the measurement light is moved. The confocal signal light detection device according to claim 1.   The confocal signal according to any one of claims 1 to 3, wherein the signal light extraction means is configured to amplify a relative light intensity of the extracted signal light. Photodetector.   5. The moving distance of the holder by the moving means is a substantially full width at half maximum in a point image response function when the measurement light is irradiated onto the surface of the object to be measured. The confocal signal light detection device according to any one of the preceding claims.   The moving means is configured to vibrate the holder in a minute range along the optical axis direction and to change the relative distance between the center of amplitude and the object to be measured beyond the minute range in the optical axis direction. 6. The confocal signal light detection device according to claim 1, wherein the confocal signal light detection device is provided.   The confocal signal light detection device according to claim 1, wherein the numerical aperture of the lens is set to 0.5 or more. A confocal signal light detection method that irradiates the measurement site inside the object with measurement light and extracts only the information of the signal light generated from the measurement site by the measurement light from the reflected light inside the object by the measurement light. There,
A first reflected light measurement step for measuring the light intensity of the reflected light when the focus position of the measurement light in the confocal state is set to a predetermined position, and maintaining the confocal state in the first reflected light measurement step. However, a second reflected light measurement step for measuring the light intensity of the reflected light when the focus position of the measurement light is adjusted to a position deviated from the predetermined position by a predetermined distance in the optical axis direction; A confocal type including a signal light extraction step of extracting a relative light intensity of the signal light based on a light intensity change of the light intensity of the reflected light measured by the second reflected light measurement step. Signal light detection method.   In the signal light extraction step, based on the difference between the light intensity measured by the first reflected light measurement step and the light intensity measured by the second reflected light measurement step, 9. The confocal signal light detection method according to claim 8, wherein the light intensity is extracted.   The reflected light is continuously measured while maintaining the confocal state between the first and second reflected light measurement steps, and the focal position of the measurement light is moved in the signal light extraction step. 9. The confocal signal light detection method according to claim 8, wherein a relative light intensity of the signal light is extracted by calculating a light intensity change rate of the reflected light in the case of the incident light.

Images