JP6547472B2 - Shape measuring device - Google Patents

Description

  The present invention relates to a shape measuring device and a shape measuring method.

  A shape measurement technique for imaging the linear light being irradiated to the surface of the object to be measured and measuring the surface shape of the object based on the so-called light cutting method is not only in the steel industry but also in various fields It is widely used. For example, Patent Document 1 below discloses a shape measurement apparatus by a light cutting method using a linear laser beam and a delay integration type camera, and the following Patent Document 2 discloses a linear laser beam Discloses a shape measurement apparatus by a light cutting method using an image sensor and an area camera.

  When applying the shape measurement technique by such a light cutting method to a red-heated object such as a steel semi-finished product such as a slab, the self-emission mainly distributed in the red wavelength band has a signal noise ratio It becomes a problem in terms of (Signal-Noise ratio). Moreover, when using the shape measurement technique by the above light cutting methods outside, sunlight becomes a problem in the point of SN ratio. In such a case, as a measure against disturbance light, select a light source whose wavelength band does not overlap with disturbance light like a blue light source for a glowing object, or use an interference filter using a narrow band light source such as a laser. It is performed to selectively transmit only the wavelength of the light source.

  When selecting the wavelength of the light source, there is a problem that the camera sensitivity generally decreases with blue light sources, and when the spectrum of disturbance light is wide like sunlight, the wavelength band does not overlap with disturbance light There is a problem that the light source can not be found. Therefore, it is simpler to use an optical band pass filter (so-called interference filter) as measures against disturbance light that can be applied regardless of the wavelength of disturbance light.

  Here, when an interference filter is used, a narrow band interference filter is often used to enhance the wavelength selectivity of the light cutting line, but when light obliquely enters the interference filter, a shift occurs in the transmission band of the light. There is a problem that the light cutting line can not be seen around the visual field. In this case, the SN ratio of the light-cut image obtained is lowered, which in turn leads to a decrease in the accuracy of the shape measurement result. The problem of visual field caused by such oblique incidence is limited in the place where the shape measuring apparatus can be installed, such as various lines in the steel industry, for example, and the distance to the object to be measured is as short as possible (ie This is remarkable in a situation where it is necessary to use a wide-angle lens in order to miniaturize the shape measuring device.

  In order to cope with the problem of shift of the transmission band due to oblique incidence as described above, Patent Document 3 below proposes a method using a spherical interference filter, and Patent Document 4 below differs depending on the location. A method has been proposed that uses an interference filter having transmission characteristics.

JP 2004-3930 A Unexamined-Japanese-Patent No. 2010-71722 JP 2012-173277 A JP 2012-242134 A

  However, the interference filters as disclosed in Patent Document 3 and Patent Document 4 are not versatile, and there is a problem that it is difficult and expensive to manufacture such an interference filter. Therefore, there is a need for an easy-to-implement and inexpensive technique that can generate a light-cut image having a good signal-to-noise ratio even under a situation where disturbance light becomes a problem.

  Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to provide a light cutting having a good signal-to-noise ratio even under a situation where disturbance light becomes a problem. An object of the present invention is to provide a shape measurement apparatus and a shape measurement method which can generate an image easily and inexpensively.

In order to solve the above problems, according to one aspect of the present invention, a laser light source that emits a linear laser beam to the surface of an object that is reflecting or emitting light, and the object to be measured An imaging device for imaging a light cutting line by the laser light on the surface of the surface to generate a light cutting image; and performing image processing on the light cutting image generated by the measuring device And an arithmetic processing unit for calculating the shape of the object to be measured, the imaging device comprising: an imaging element; and an image side telecentric lens for forming an image of the light cutting line on the imaging element. have a, an optical bandpass filter having disposed the predetermined bandwidth between said image-side telecentric lens the imaging device, the laser power density of the linear laser beam, and the optical band Pass filter The width is based on the illuminance on the imaging surface required to image the light cutting line, and the signal-to-noise ratio required for disturbance light that is the light reflected or emitted by the object to be measured. A shape measurement device is provided , wherein the numerical aperture according to the bandwidth of the optical band pass filter is set smaller than the numerical aperture determined by the F value of the imaging device .
In order to solve the above problems, according to another aspect of the present invention, there is provided a laser light source for irradiating a linear laser beam to a surface of an object to be measured which is reflecting or emitting light. A measuring device having an imaging device for imaging a light cutting line by the laser light on the surface of the object to generate a light cutting image; and an image with respect to the light cutting image generated by the measuring device An arithmetic processing unit that performs processing to calculate the shape of the object to be measured; and the imaging device includes an imaging element, and an image-side telecentric that forms an image of the light cutting line on the imaging element. A laser, and a laser power density of the linear laser light, comprising: a lens; and an optical band pass filter having a predetermined bandwidth, which is disposed between the image side telecentric lens and the imaging device. Said optical band pass filter The bandwidth of the light source is the illuminance on the imaging surface required for imaging the light cutting line, and the signal-to-noise ratio required for disturbance light which is the light reflected or emitted by the object to be measured. The laser power density at the surface of the object to be measured is a plane in which the laser power density of the linear laser light is taken on the vertical axis and the bandwidth of the optical band pass filter is taken on the horizontal axis. In the coordinate system, a curve representing the relationship between the laser power density and the bandwidth at which the signal-to-noise ratio to disturbance light is constant, and the laser power density and band at which the brightness of the image of the light cutting line at the image plane is constant. a curve representing the relationship between the width is set to the laser power density above the value corresponding to the intersection of shape measurement apparatus is provided.

  The curve representing the relationship between the laser power density and the bandwidth in which the signal-to-noise ratio to disturbance light is constant may be a straight line.

  As described above, according to the present invention, it is possible to use an easy-to-implement and inexpensive image-side telecentric lens and an optical band-pass filter of a predetermined bandwidth provided at the rear stage of the image-side telecentric lens. Even under conditions where disturbance light is a problem, it is possible to generate a light cut image having a good signal-to-noise ratio.

It is a block diagram showing an example of composition of a shape measuring device concerning an embodiment of the present invention. It is an explanatory view showing typically an example of composition of a measuring device concerning the embodiment. It is an explanatory view for explaining an optical band pass filter. It is an explanatory view for explaining an optical band pass filter. It is an explanatory view showing typically an example of composition of an imaging device concerning the embodiment. It is the graph which showed the relationship between the spread angle of a light ray, and the amount of wavelength shifts. It is explanatory drawing which showed typically the relationship between laser power density and a bandwidth. It is explanatory drawing which showed typically the relationship between laser power density and a bandwidth. It is explanatory drawing which showed typically the relationship between laser power density and a bandwidth. FIG. 6 is a block diagram showing an example of the configuration of an image processing unit included in the arithmetic processing unit according to the embodiment. It is the flowchart which showed an example of the flow of the determination method of the laser power density and bandwidth which concern on the embodiment. It is the flowchart which showed an example of the flow of the shape measurement method which concerns on the embodiment. It is the block diagram which showed an example of the hardware constitutions of the arithmetic processing unit concerning the embodiment. FIG. 5 is an explanatory diagram for describing a first embodiment. FIG. 10 is an explanatory diagram for describing a second embodiment. FIG. 10 is an explanatory diagram for describing a second embodiment. FIG. 10 is an explanatory diagram for describing a second embodiment. FIG. 10 is an explanatory diagram for describing a second embodiment. FIG. 10 is an explanatory diagram for describing a second embodiment.

  The present invention will now be described more fully with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. In the present specification and the drawings, components having substantially the same functional configuration will be assigned the same reference numerals and redundant description will be omitted.

(About the shape measuring device)
Hereinafter, the shape measuring device according to the first embodiment of the present invention will be described in detail with reference to FIGS. 1 to 8.
FIG. 1 is a block diagram showing an example of the configuration of the shape measuring device according to the present embodiment. FIG. 2 is an explanatory view schematically showing an example of the configuration of the measuring apparatus according to the present embodiment. FIG. 3A and FIG. 3B are explanatory diagrams for explaining an optical band pass filter. FIG. 4 is an explanatory view schematically showing an example of the configuration of the imaging device according to the present embodiment. FIG. 5 is a graph showing the relationship between the light spread angle and the wavelength shift amount. 6A and 6B are explanatory diagrams schematically showing the relationship between the laser power density and the bandwidth. FIG. 7 is an explanatory view schematically showing the relationship between the laser power density and the bandwidth. FIG. 8 is a block diagram showing an example of the configuration of an image processing unit provided in the arithmetic processing unit according to the present embodiment.

<About the whole configuration of the shape measuring device>
The shape measuring device according to the present embodiment is a device that measures the shape of the surface of an object to be measured that reflects or emits light using a so-called light cutting method.
Here, the object to be measured that reflects or emits light, which is the object to be measured by the shape measuring apparatus according to the present embodiment, is not particularly limited, and, for example, various metals such as red heat As such, it may be one emitting light of a predetermined wavelength, or it may be, for example, a metal or the like installed outdoors and reflecting sunlight on its own surface.

  Such a shape measuring device 1 mainly includes a measuring device 10 and an arithmetic processing unit 20, as schematically shown in FIG.

  The measuring apparatus 10 emits a linear laser beam to the measurement object S, and images a light cutting line by the linear laser beam on the surface of the measurement object S, thereby the measurement object S is related. It is an apparatus for generating a light section image. In the shape measuring device 1 according to the present embodiment, an object that reflects or emits light of a predetermined wavelength is the measurement object S. Not only the image but also the light reflected or emitted by the measurement object S is incident as disturbance light.

  As schematically shown in FIG. 2, this measuring apparatus 10 picks up a laser light source 11 for irradiating a linear laser beam to the measurement object S, and picks up a light cutting line on the surface of the measurement object S And an imaging device 13.

  The laser light source 11 includes, for example, a light source unit for emitting a laser beam of a predetermined wavelength such as a visible light band, and a laser beam emitted from the light source unit is condensed in a line width direction while expanding it in the length direction. And a lens (for example, a cylindrical lens, a rod lens, a Powell lens, etc.) for forming an annular light.

  In addition, the imaging device 13 includes a lens having a specific optical system as described later, and a CCD (Charge Coupled Device) or a CMOS (Complementary) on which an image of a light cutting line of the measurement object S is formed by the lens. It has an imaging device such as Metal Oxide Semiconductor) and an optical system band pass filter as described later.

  The positional relationship between the laser light source 11 and the imaging device 13 is not particularly limited, but as schematically shown in FIG. 2, the optical axis of the imaging device 13 and the measurement object S It is preferable that the imaging device 13 be provided so as to be substantially parallel to the normal direction of the surface. The laser light source 11 is preferably provided obliquely to the surface of the measurement object S such that the optical axis of the laser light source 11 and the optical axis of the imaging device 13 form a predetermined angle.

  The detailed configuration of the imaging device 13 will be described again below.

  The measurement apparatus 10 performs a plurality of light-cut images by performing irradiation processing of linear laser light, imaging processing of light cutting lines, and the like at predetermined time intervals under the control of the arithmetic processing unit 20 described later. Is generated, and the obtained light section image is output to the arithmetic processing unit 20.

  The arithmetic processing unit 20 acquires the light-cut image generated by the measuring device 10, and performs known processing as disclosed in Patent Document 1 and Patent Document 2 on the acquired light-cut image. Thus, a luminance image and an asperity image are generated. Thereafter, the arithmetic processing unit 20 generates information representing the surface shape of the measurement target S by performing predetermined image processing on the generated luminance image and the concavo-convex image. The arithmetic processing unit 20 also functions as a control unit that controls an imaging process (in other words, a process of generating a light-cut image) in the measuring apparatus 10.

  The detailed configuration of the arithmetic processing unit 20 will be described again below.

Regarding Configuration of Imaging Device 13
Next, the configuration of the imaging device 13 provided in the measuring device 10 according to the present embodiment will be described in detail with reference to FIGS. 3A to 4.

  As mentioned earlier, in the shape measuring apparatus 1, in order to remove the influence of disturbance light, a narrow band interference filter is often used as an optical band pass filter. Such an interference filter is designed on the assumption that light is incident perpendicularly to the surface of the interference filter.

  As shown in FIG. 3A, when light is perpendicularly incident on the interference filter, the light reflected on the upper surface (reflected wave b) is in phase because the refractive index of the interference filter is n> 1. Is inverted, and the light reflected by the lower surface (reflected wave a) does not change in phase. Therefore, when the optical path length difference (2nd, where the thickness of the interference filter is d) is an integral multiple of the wavelength, the reflected light intensity is zero, and the amount of light transmitted through the filter is maximum. On the other hand, as shown to FIG. 3B, the case where light injects diagonally with respect to an interference filter is considered. In FIG. 3B, since the dotted lines are equiphase lines and the optical path lengths of AC and BD are equal, the optical path length difference is CED. The length of the CED is 2nd cos θ, where θ is an incident angle in the interference filter, and the optical path difference becomes smaller as θ becomes larger. Therefore, the transmission wavelength is shifted to the short wavelength. Such a short wavelength shift of the transmission wavelength accompanying oblique incidence becomes remarkable when using a wide-angle lens (short focus lens) in order to shorten the separation distance between the imaging device 13 and the measurement object S.

Now, let the condensing half angle of the interference filter as shown in FIGS. 3A and 3B (the same as the incident angle in the interference filter in FIG. 3B) be θ [degree], and the effective refractive index of the interference filter be n Assuming that the central wavelength of light at normal incidence is λ ₀ [nm] and the central wavelength of light when the incident angle is inclined by θ degrees is λ _θ [nm], these parameters can be expressed by the following equation 101 The relationship shown in FIG.

  In order to suppress such a short wavelength shift due to oblique incidence, in the imaging device 13 according to the present embodiment, as schematically shown in FIG. 4, as the lens 103 mounted on the camera body 101, an image side telecentric A lens is used. In the image-side telecentric lens, as schematically shown in FIG. 4, an aperture stop is provided on the front focal plane of the optical system (in other words, on the focal plane on the object plane side of the optical system). In such an image-side telecentric optical system, the exit pupil can be at infinity on the image side, and the chief ray of the image space is parallel to the optical axis. Such an image side telecentric lens is not particularly limited, and it is possible to use a known one according to the focal length f required for the lens 103.

  In the imaging device 13 according to the present embodiment, as shown in FIG. 4, light of a desired center wavelength is transmitted between the image-side telecentric lens and the imaging element 105 provided in the camera body 101. An optical band pass filter (interference filter) 107 of a predetermined bandwidth is disposed. The image-side telecentric lens makes the chief ray of light incident on the lens 103 be parallel to the optical axis, so that oblique incidence on the optical band pass filter 107 as shown in FIG. 3 is suppressed. Thus, even when a wide-angle lens is used as the lens 103, it is possible to prevent the occurrence of a non-transmissive portion in the image of the light cutting line due to the oblique incidence on the optical band pass filter 107.

  The arrangement position of the optical band pass filter 107 is not particularly limited as long as it is located between the optical system of the image side telecentric lens and the imaging device 105, and is provided inside the lens 103. It may be provided inside the camera body 101, or may be provided at the connection portion between the lens 103 and the camera body 101.

  The configuration of the imaging device 13 according to the present embodiment has been described above in detail.

<Constraint of bandwidth of optical band pass filter>
Next, the restriction on the bandwidth of the optical band pass filter 107 will be described with reference to FIG.

  In the imaging device 13 as shown in FIG. 4, when the spread angle θ of the light beam viewed from the image plane is small, the image of the subject on the image plane (that is, the image of the light cutting line) becomes dark. In the case of an optical band pass filter, light rays in a portion having a large spread angle are obliquely incident and not transmitted, which is substantially equivalent to limiting the spread angle (that is, narrowing the stop). Therefore, the numerical aperture NA = sin θ is determined by the bandwidth of the filter. For example, when light with a wavelength of 640 nm is incident on an optical band pass filter having an effective refractive index n = 1.5, the relationship between the wavelength shift amount and the incident angle is shown in FIG. It becomes like.

  For example, when the spread angle θ = 10 degrees shown in FIG. 4, the numerical aperture NA = sin θ = 0.1736 of the optical band pass filter provided in the air is obtained. On the other hand, since a relationship represented by F = 1 / (2 × NA) is established between the F number and the numerical aperture NA, the F value corresponding to the spread angle θ = 10 degrees is 1 / (2). × 0.1736) = 2.9. Now, in the graph shown in FIG. 5, it is understood that the wavelength shift amount corresponding to the spread angle θ = 10 degrees is 4 nm. Therefore, the optical band pass filter as exemplified in the present example has an action equivalent to the aperture of F2.9 when the bandwidth is 4 nm. When the equivalent F value of such an optical band pass filter is larger than the F value of the lens 103, the brightness of the obtained image is limited by the bandwidth of the optical band pass filter.

The brightness of the image is proportional to the square of the numerical aperture NA, since it is inversely proportional to the square of the F value. Optical bandpass filter 107 according to this embodiment, since the central wavelength lambda ₀ of the time of normal incidence, the light to be transmitted through the wavelength to the center wavelength lambda _theta upon oblique incidence in spread angle theta is determined, the band The width needs at least the wavelength shift amount Δλ = λ ₀ −λ _θ . Now, assuming that the bandwidth of the optical band pass filter 107 is Δλ, the bandwidth Δλ is expressed by the following Equation 103 using the above Equation 101.

  If Equation 103 above is solved for the numerical aperture NA, the following Equation 105 is obtained.

  Therefore, the relationship between the equivalent F-number of the optical band pass filter 107 and the bandwidth Δλ is expressed by the following equation 107 from F = 1 / (2 × NA).

  The restriction on the bandwidth of the optical band pass filter 107 according to the present embodiment has been described above in detail.

<Restrictions on laser power density>
Next, restrictions on the laser power density of the linear laser light emitted from the laser light source 11 in the measurement apparatus 10 according to the present embodiment will be described in detail with reference to FIGS. 6A to 7.

[On the restriction by the SN ratio]
In order to obtain a light cut image with a good signal-to-noise ratio, it is important to consider the constraints on the signal-to-noise ratio. Now, in the image plane of the imaging device 13 as shown in FIG. 4, the SN ratio represented by the intensity of the light source / the intensity of disturbance light is examined.

The spectrum distribution of disturbance light near the laser wavelength (the spectrum when the horizontal axis is wavelength [nm] and the vertical axis is power density per wavelength [mW / cm ² / nm]) If the distribution can be considered flat, the signal-to-noise ratio (SNR) is proportional to the product of the reciprocal of the bandwidth and the laser power density. That is, the relationship “SNR∝ (1 / bandwidth) × laser power density” is established. In this case, considering a plane coordinate system in which the laser power density is taken on the vertical axis and the bandwidth is taken on the horizontal axis, the relationship between the laser power density and the bandwidth at which the SN ratio becomes constant is represented by a straight line.

On the other hand, when the spectral distribution of disturbance light near the laser wavelength can not be regarded as flat, the intensity of disturbance light integrates the spectral distribution L _d (λ) of disturbance light from wavelength λ _θ to wavelength λ _0. The value is Now, assuming that the intensity of the light source is L _p , the SN ratio (SNR) at this time is a value represented by the following equation 111. In this case, considering a plane coordinate system in which the laser power density is taken along the vertical axis and the bandwidth is taken along the horizontal axis, the relationship between the laser power density and the bandwidth where the SN ratio becomes constant is a curve instead of a straight line. .

  In practice, since a narrow band optical band pass filter with a band width of about 5 to 10 nm is often used as the optical band pass filter 107, the spectrum distribution of disturbance light near the laser wavelength is flat. It can often be regarded as.

[On the brightness restriction on the image plane]
Even in the absence of disturbance light, it is important that the image of the light cutting line has a certain brightness or more at the image plane in order to perform imaging under a desired exposure time or lens aperture. In the following, conditions for obtaining constant brightness when there is no disturbance light will be examined.

Here, considering the restriction of brightness due to the equivalent aperture effect in the optical band pass filter 107, in the imaging device 13 as shown in FIG. 4, the brightness of the image on the image plane is the square of the numerical aperture. It is proportional to the product of the laser power density. That is, the relationship of "brightness of image at image plane 開口 (numerical aperture ² ) x laser power density" is established. In this case, when the numerical aperture is replaced with the bandwidth of the optical band pass filter 107 by Equation 105, the image is taken on a plane coordinate system in which the laser power density is on the vertical axis and the bandwidth is on the horizontal axis. The relationship between the laser power density and the bandwidth at which the brightness of the light is constant is represented by a curve.

  Therefore, the plane coordinate system with the laser power density on the vertical axis and the bandwidth on the horizontal axis that the SN ratio is above the predetermined value and the brightness of the image on the image plane is also above the predetermined value And the laser power density and the band width above the curve (or straight line) L1 representing the relationship between the laser power density and the band width such that the SN ratio to disturbance light is constant, and the brightness on the image plane becomes constant. The region represented by the upper side of the curve L2 representing the relationship of

  FIGS. 6A and 6B schematically show this relationship. FIG. 6A corresponds to the case where the relationship between the laser power density and the bandwidth at which the SN ratio for disturbance light is constant is represented by curve L1, and FIG. 6B shows the laser power density at which the SN ratio for disturbance light is constant. The relationship between and the bandwidth corresponds to the case where it can be expressed by the straight line L1.

  Referring to FIGS. 6A and 6B, the laser power of the linear laser light emitted from the laser light source 11 is set so that the SN ratio becomes equal to or more than a predetermined value and the brightness of the image on the image plane also becomes equal to or more than the predetermined value. It can be seen that the density has a lower limit. That is, the laser power density of the linear laser light irradiated from the laser light source 11 is a curve L1 and a curve so that the SN ratio becomes equal to or more than a predetermined value and the brightness of the image on the image plane also becomes equal to or more than the predetermined value. The laser power density needs to be equal to or higher than the point of intersection with L2.

  Further, as described above, the bandwidth of the optical band pass filter 107 needs to be equal to or less than the bandwidth corresponding to the F value of the lens 103. When the bandwidth of the optical band pass filter exceeds the bandwidth corresponding to the F value of the lens 103, the light cutting line does not become bright even when the bandwidth of the optical band pass filter 107 is expanded, Only disturbance light increases.

  Therefore, in consideration of these restrictions, the SN ratio becomes equal to or more than a predetermined value, and the brightness of the image on the image plane also becomes equal to or more than the predetermined value in the plane coordinate system shown in FIGS. 6A and 6B. It can be seen that the area is represented by diagonal lines.

  FIG. 7 is a schematic view showing how the required laser power density changes in accordance with the camera sensitivity of the imaging device 13. As is clear from FIG. 7, the laser power density corresponding to the intersection of the curve L2 and the straight line representing the bandwidth corresponding to the F value of the lens 103 enables imaging processing when there is no disturbance light. This is the minimum required brightness (laser power density). On the other hand, as described above, in order for the SN ratio to be a predetermined value or more and the brightness of the image on the image plane to be a predetermined value or more, the laser power density corresponding to the intersection of curve L1 and curve L2 is Laser power density is required.

  Therefore, when the camera sensitivity of the imaging device 13 is high, although the imaging processing when there is no disturbance light can be realized with a low laser power density, as shown in FIG. 7 when the disturbance light exists. The minimum required bulking amount will be large. On the other hand, when the camera sensitivity of the imaging device 13 is low, although the imaging processing when there is no disturbance light has a relatively high laser power density, the minimum necessary amount of bulk increase in the presence of the disturbance light is Relatively small.

  Further, as is clear from FIG. 7, if the laser power density is high, the bandwidth of the optical band pass filter 107 can be narrowed.

  In the measuring apparatus 10 according to the present embodiment, the laser power density of the linear laser light emitted from the laser light source 11 and the bandwidth of the optical band pass filter 107 are set based on the above-described restrictions. .

  In practice, the bandwidth of the optical band pass filter 107 provided in the imaging device 13 is the performance (for example, bandwidth = 5 nm or more and 10 nm or less) of the narrow band optical band pass filter available to the device. It is often set. Therefore, in the shape measuring apparatus 1 according to the present embodiment, the laser is provided so as to satisfy the above relationship according to the bandwidth of 5 nm or more and 10 nm or less which is the bandwidth of the optical band pass filter 107 used by the arithmetic processing unit 20 described later. The laser power density of the linear laser beam emitted from the light source 11 is controlled.

[About the identification method of the curve L1 and the curve L2]
Next, a method of specifying the curves L1 and L2 as described above will be briefly described.

First, a method of specifying the curve L1 representing the relationship between the laser power density and the bandwidth in which the SN ratio is constant will be described.
In this case, in order to specify the curve L1, first, the spectrum distribution of the disturbance light to be focused on and the power density of the disturbance light on the measurement object S are actually measured, and an object to be the measurement object S Identify the surface characteristics (eg, emissivity, reflectance, etc.) of Then, using the spectrum distribution of the disturbance light obtained, a curve or a line representing the power density of the disturbance light in consideration of the SN ratio to be determined for the light section image to be generated and the surface characteristics of the measurement object S It is sufficient to calculate L1.

  Alternatively, if the spectral distribution of the disturbance light to be considered can be regarded as constant, the band width of the band pass filter and the laser power density are fixed, and the experiment is performed in the presence of the disturbance light, and the planes shown in FIGS. The SN ratio of one point on the coordinates is obtained experimentally. Since the straight line passing through the origin and the point is a straight line with a constant SN ratio, the straight line whose inclination is adjusted to be a desired SN ratio may be set as L1 described above. For example, if the measured SN ratio is 3 and the required SN ratio is 12, then the slope may be quadrupled.

  Next, a method of specifying the curve L2 representing the relationship between the laser power density and the bandwidth in which the brightness on the image plane is constant will be described.

First, at an exposure time and an F value necessary for imaging, a laser power density that allows imaging of the light cutting line at a desired brightness when there is no disturbance light is determined by experiment or the like. Next, the bandwidth corresponding to the F value of the image-side telecentric lens to be used is calculated by using the equation 107. Subsequently, “(numerical aperture ² ) is passed so as to pass through the point represented by (the minimum power density at which imaging processing can be performed when disturbance light is not present, the bandwidth corresponding to the F value of the lens). The constant part of the curve represented by the expression x) laser power density = constant "is specified by a known method. Thereby, the curve L2 can be identified.

  The flow of the method of specifying such a curve will be described again below, and will be described in detail by giving specific examples in the following embodiments.

  In the above, the measuring apparatus 10 with which the shape measuring apparatus 1 which concerns on this embodiment is equipped was demonstrated in detail, referring FIGS. 2-7.

Regarding Configuration of Arithmetic Processing Device 20
Next, referring back to FIG. 1 again, the configuration of the arithmetic processing unit 20 will be described in detail.
The arithmetic processing unit 20 included in the shape measuring apparatus 1 according to the present embodiment controls the imaging process of the light section line (that is, the process of generating the light section image) in the measuring apparatus 10 in a centralized manner. It is an apparatus which implements image processing with respect to the light sectioned image which has been calculated, and calculates the shape of the object.

  The arithmetic processing unit 20 includes, for example, an imaging control unit 21, an image processing unit 23, a display control unit 25, and a storage unit 27 as schematically shown in FIG. 1.

  The imaging control unit 21 is realized by a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), a communication device, and the like. The imaging control unit 21 performs imaging control of the measurement object S by the measuring device 10. More specifically, when the measurement target S is placed at a predetermined position, the imaging control unit 21 has a laser power density that satisfies the conditions described above with respect to the laser light source 11 of the measuring device 10. While sending out the trigger signal for starting irradiation of the linear laser beam which is being carried out, the trigger for starting the imaging process of the captured image (namely, light section image) of a light section line to the imaging device 13 Send a signal.

  The image processing unit 23 is realized by, for example, a CPU, a ROM, a RAM, a communication device, and the like. The image processing unit 23 performs various types of image processing using the light section image acquired from the imaging device 13 of the measuring device 10.

  More specifically, the image processing unit 23 generates a concavo-convex image and a luminance image as disclosed in Patent Document 1 and Patent Document 2 using the light section image output from the measuring device 10 . Thereafter, the image processing unit 23 calculates the surface shape of the measurement object S using the generated concavo-convex image and the luminance image.

  When the shape measurement process of the surface of the measurement object S is completed, the image processing unit 23 transmits information on the obtained measurement result to the display control unit 25.

  The display control unit 25 is realized by, for example, a CPU, a ROM, a RAM, an output device, and the like. The display control unit 25 outputs the measurement result of the measurement object S transmitted from the image processing unit 23 to an output device such as a display provided in the arithmetic processing device 20 or an output device provided outside the arithmetic processing device 20. Control the display when displaying. Thereby, the user of the shape measuring apparatus 1 can grasp various measurement results regarding the surface shape of the measuring object S on the spot.

  The storage unit 27 is realized by, for example, a RAM, a storage device, or the like included in the arithmetic processing unit 20 according to the present embodiment. In the storage unit 27, various parameters that need to be stored when the arithmetic processing unit 20 according to the present embodiment performs some processing, progress of processing, etc., various databases, programs, etc. It is recorded. In the storage unit 27, the imaging control unit 21, the image processing unit 23, the display control unit 25, and the like can freely perform data read / write processing.

[About the configuration of the image processing unit 23]
Subsequently, the configuration of the image processing unit 23 provided in the arithmetic processing unit 20 according to the present embodiment will be briefly described with reference to FIG.

  The image processing unit 23 according to the present embodiment mainly includes a data acquisition unit 201, a shape calculation unit 203, and a result output unit 205, as shown in FIG.

  The data acquisition unit 201 is realized by, for example, a CPU, a ROM, a RAM, a communication device, and the like. The data acquisition unit 201 acquires, from the measurement apparatus 10, image data of the light section image generated by the measurement apparatus 10. The data acquisition unit 201 outputs the image data of the acquired light section image to a shape calculation unit 203 described later.

  The shape calculation unit 203 according to the present embodiment is realized by, for example, a CPU, a ROM, a RAM, and the like. The shape calculation unit 203 calculates the surface shape of the measurement object S using the light section image generated using the light section line.

  More specifically, the shape calculation unit 203 uses the light-cut image generated using the light-cut line to generate a concavo-convex image and a luminance image as disclosed in Patent Document 1 and Patent Document 2 described above. Generate Thereafter, the shape calculation unit 203 calculates the surface shape of the measurement object S using the generated concavo-convex image and the luminance image.

  Here, the method of calculating the surface shape of the measurement object S by the shape calculation unit 203 is not particularly limited, and it is possible to appropriately use a known method based on the light cutting method.

  Information representing the result of the shape calculation process performed by the shape calculation unit 203 is output to the result output unit 205.

  The result output unit 205 is realized by, for example, a CPU, a ROM, a RAM, and the like. The result output unit 205 outputs, to the display control unit 25, information on the shape calculation result output from the shape calculation unit 203. As a result, various information as described above is output to the display unit (not shown). Further, the result output unit 205 may output the obtained result to an external device such as a manufacturing control procon or the like, and may use the obtained result to create various forms. In addition, the result output unit 205 may store various information as described above in the storage unit 27 or the like as history information in association with time information on the date and time when the information is calculated.

  Heretofore, an example of the function of the arithmetic processing unit 20 according to the present embodiment has been shown. Each component described above may be configured using a general-purpose member or circuit, or may be configured by hardware specialized for the function of each component. Further, all functions of each component may be performed by a CPU or the like. Therefore, it is possible to change the configuration to be used as appropriate according to the technical level at which the present embodiment is implemented.

  In addition, it is possible to create a computer program for realizing each function of the arithmetic processing unit according to the present embodiment as described above, and to install it on a personal computer or the like. In addition, a computer readable recording medium in which such a computer program is stored can be provided. The recording medium is, for example, a magnetic disk, an optical disk, a magneto-optical disk, a flash memory or the like. In addition, the above computer program may be distributed via, for example, a network without using a recording medium.

(About setting method of laser power density and bandwidth)
Next, the flow of the method of setting the laser power density and the bandwidth in the shape measuring device 1 according to the present embodiment will be briefly described with reference to FIG.

  In the setting method of the laser power density and the bandwidth, first, the knowledge about the power density of the disturbance light obtained by measuring the spectrum distribution of the disturbance light and the power density of the disturbance light on the measuring object S is used, A curve (or a straight line) L1 related to the SN ratio is calculated in consideration of the surface characteristics such as the emissivity and the reflectance of the measurement object S and the SN ratio to be obtained in the light cut image (step S101).

  Alternatively, if the spectral distribution of the disturbance light to be considered can be regarded as constant, the band width of the band pass filter and the laser power density are fixed, and the experiment is performed in the presence of the disturbance light, and the planes shown in FIGS. The SN ratio of one point on the coordinates is obtained experimentally, and a straight line connecting the origin and the point is drawn to obtain a straight line with a constant SN ratio. Next, the ratio K between the measured SN ratio and the required SN ratio is determined, and the slope of the straight line with the constant SN ratio is multiplied by K to calculate the straight line L1. (Step S101).

  Next, a laser power density that allows the light cutting line to be imaged at a desired brightness when there is no disturbance light is specified by an experiment or the like. (Step S103)

  Subsequently, based on the F value of the image-side telecentric lens used as the imaging device 13, the magnitude of the bandwidth corresponding to the F value has a relationship of F = 1 / (2 × NA), and It calculates based on (step S105).

  Subsequently, in the plane coordinate system as shown in FIG. 6A to FIG. 7, the point having the value of the power density necessary for the imaging processing obtained in step S103 is passed at the position of the bandwidth corresponding to the F value of the lens. A curve L2 to be calculated is calculated (step S107).

  Then, the laser power density and the bandwidth of the region defined by the curves L1 and L2 and the bandwidth corresponding to the F value of the lens (the region represented by hatching in FIGS. 6A and 6B) A combination is selected (step S109).

  By performing the process in the above flow, it is possible to set the laser power density and the bandwidth in the shape measuring device 1 according to the present embodiment. The setting method will be specifically described below by way of an example.

(About shape measurement method)
Subsequently, the flow of the shape measuring method implemented by the shape measuring device 1 according to the present embodiment will be briefly described with reference to FIG.

  In the shape measuring method according to the present embodiment, first, a laser is used for the measuring device 10 using the imaging device 13 having the image side telecentric lens and the optical band pass filter provided between the lens and the imaging device. The laser power density of the light source 11 and the bandwidth of the optical band pass filter are set (step S151). The method of setting the laser power density and the bandwidth is as described with reference to FIG.

  Next, the imaging control unit 21 of the arithmetic processing unit 20 using the imaging device 13 having the image-side telecentric lens as described above and provided with an optical band pass filter with a bandwidth set at the subsequent stage thereof. Under control of the light cutting line of a predetermined laser power density is imaged (step S153). Thereby, a light section image of the measurement object S is generated. The generated light section image is output from the imaging device 13 to the arithmetic processing unit 20.

  The image processing unit 23 of the arithmetic processing unit 20 performs image processing on the generated light-cut image to generate an uneven image and a luminance image as a shape calculation image (step S155). Thereafter, the image processing unit 23 calculates the surface shape of the measurement object S based on the generated images for shape calculation (step S157). Subsequently, the image processing unit 23 of the arithmetic processing unit 20 outputs the obtained result (step S159).

  Thereby, the user of the shape measuring device 1 according to the present embodiment can grasp the measurement result on the surface shape of the measuring object S on the spot.

  Heretofore, an example of the flow of the shape measuring method according to the present embodiment has been briefly described with reference to FIG.

(About hardware configuration)
Next, the hardware configuration of the arithmetic processing unit 20 according to the embodiment of the present invention will be described in detail with reference to FIG. FIG. 11 is a block diagram for explaining the hardware configuration of the arithmetic processing unit 20 according to the embodiment of the present invention.

  The arithmetic processing unit 20 mainly includes a CPU 901, a ROM 903 and a RAM 905. The arithmetic processing unit 20 further includes a bus 907, an input device 909, an output device 911, a storage device 913, a drive 915, a connection port 917, and a communication device 919.

  The CPU 901 functions as an arithmetic processing unit and a control unit, and controls all or part of the operation in the arithmetic processing unit 20 in accordance with various programs recorded in the ROM 903, the RAM 905, the storage unit 913, or the removable recording medium 921. The ROM 903 stores programs used by the CPU 901, calculation parameters, and the like. The RAM 905 primarily stores programs used by the CPU 901, parameters that appropriately change in the execution of the programs, and the like. These are mutually connected by a bus 907 constituted by an internal bus such as a CPU bus.

  The bus 907 is connected to an external bus such as a peripheral component interconnect / interface (PCI) bus via a bridge.

  The input device 909 is an operation unit operated by the user, such as a mouse, a keyboard, a touch panel, a button, a switch, and a lever. The input device 909 may be, for example, a remote control unit (so-called remote control) using infrared rays or other radio waves, or an external connection device 923 such as a PDA corresponding to the operation of the arithmetic processing unit 20. May be Furthermore, the input device 909 is configured of, for example, an input control circuit that generates an input signal based on the information input by the user using the above-described operation means, and outputs the generated input signal to the CPU 901. By operating the input device 909, the user of the shape measuring device 1 can input various data to the arithmetic processing unit 20 and instruct processing operations.

  The output device 911 is configured of a device capable of visually or aurally notifying the user of the acquired information. Such devices include display devices such as CRT display devices, liquid crystal display devices, plasma display devices, EL display devices and lamps, audio output devices such as speakers and headphones, printer devices, mobile phones, facsimiles and the like. The output device 911 outputs, for example, results obtained by various processes performed by the arithmetic processing unit 20. Specifically, the display device displays the results obtained by the various processes performed by the arithmetic processing unit 20 as text or an image. On the other hand, the audio output device converts an audio signal composed of reproduced audio data, acoustic data and the like into an analog signal and outputs it.

  The storage device 913 is a device for data storage configured as an example of a storage unit of the arithmetic processing unit 20. The storage device 913 includes, for example, a magnetic storage unit device such as a hard disk drive (HDD), a semiconductor storage device, an optical storage device, or a magneto-optical storage device. The storage device 913 stores programs executed by the CPU 901, various data, various data acquired from the outside, and the like.

  The drive 915 is a reader / writer for a recording medium, and is built in or externally attached to the arithmetic processing unit 20. The drive 915 reads out information recorded in a removable recording medium 921 such as a mounted magnetic disk, an optical disk, a magneto-optical disk, or a semiconductor memory, and outputs the information to the RAM 905. The drive 915 can also write a record on a removable recording medium 921 such as a mounted magnetic disk, an optical disk, a magneto-optical disk, or a semiconductor memory. The removable recording medium 921 is, for example, a CD medium, a DVD medium, a Blu-ray (registered trademark) medium, or the like. Further, the removable recording medium 921 may be Compact Flash (registered trademark) (Compact Flash: CF), a flash memory, an SD memory card (Secure Digital memory card), or the like. Further, the removable recording medium 921 may be, for example, an IC card (Integrated Circuit card) equipped with a noncontact IC chip, an electronic device, or the like.

  The connection port 917 is a port for directly connecting a device to the arithmetic processing unit 20. Examples of the connection port 917 include a universal serial bus (USB) port, an IEEE 1394 port, a small computer system interface (SCSI) port, and an RS-232C port. By connecting the external connection device 923 to the connection port 917, the arithmetic processing unit 20 acquires various data directly from the external connection device 923 or provides various data to the external connection device 923.

  The communication device 919 is, for example, a communication interface configured of a communication device or the like for connecting to the communication network 925. The communication device 919 is, for example, a communication card for wired or wireless Local Area Network (LAN), Bluetooth (registered trademark), or WUSB (Wireless USB). In addition, the communication device 919 may be a router for optical communication, a router for asymmetric digital subscriber line (ADSL), a modem for various types of communication, or the like. The communication device 919 can transmit and receive signals and the like according to a predetermined protocol such as TCP / IP, for example, with the Internet or another communication device. The communication network 925 connected to the communication device 919 is configured by a network or the like connected by wire or wireless, and is, for example, the Internet, a home LAN, an in-house LAN, infrared communication, radio wave communication or satellite communication. May be

  Heretofore, an example of the hardware configuration that can realize the function of the arithmetic processing unit 20 according to the embodiment of the present invention has been shown. Each of the components described above may be configured using a general-purpose member, or may be configured by hardware specialized for the function of each component. Therefore, it is possible to change the hardware configuration to be used as appropriate according to the technical level of the time of carrying out the present embodiment.

  Below, the shape measuring apparatus and shape measuring method which concern on this invention are concretely demonstrated, showing an Example and a comparative example. The embodiments described below are merely examples of the shape measuring apparatus and the shape measuring method according to the present invention, and the shape measuring apparatus and the shape measuring method according to the present invention are not limited to the following examples. .

Example 1
First, a linear laser beam is generated using a laser light source that emits red light having a wavelength of 660 nm, and the linear laser beam is irradiated to a steel plate not provided with red heat indoors to cut the light. The image was captured by an imaging device provided with an image-side telecentric lens. Here, the focal length f of the lens is 7 mm, and imaging was performed at a field angle of 63 degrees. At this time, an optical band pass filter (multilayer interference filter, transmission center wavelength: 660 nm) with a bandwidth of 10 nm is installed on the front stage (object plane side) or rear stage (image plane side) of the image side telecentric lens. The obtained images were compared.

The results obtained are shown in FIG.
As apparent from FIG. 12, when an optical band pass filter is installed at the rear stage of the image side telecentric lens, linear laser light is reflected over the entire area in the width direction of the image, while the image side telecentric lens When an optical band pass filter is installed on the front surface, it can be seen that linear laser light appears only at the central portion in the width direction of the image.

  Thus, using the imaging device 13 according to the present invention is a situation where only a short focus lens (i.e., a wide-angle lens) can be used (i.e., a situation where the distance to the measurement object S can not be sufficiently obtained). However, it becomes possible to obtain an appropriate light section image.

(Example 2)
In the present embodiment, a red-hot steel plate having a temperature of 900 ° C. and an emissivity of 0.9 (in other words, a reflectance of 0.1) is used as the measurement object S. The wavelength of the laser light source 11 was 640 nm, and the SN ratio of the target light section image was 20 or more. In addition, a multilayer interference filter (transmission center wavelength: 640 nm) was used as an optical band pass filter provided downstream of the image side telecentric lens, and the equivalent refractive index n of the interference filter was 1.5. Furthermore, for the imaging device 13 used, the minimum necessary brightness for performing imaging processing with a predetermined exposure time in the absence of disturbance light is the F value of the imaging device 13 (more specifically, the lens) The laser power density was 0.8 mW / cm ² when the was 1.4.

  FIG. 13 illustrates the distribution of the black body radiation spectrum near a wavelength of 640 nm. In FIG. 13, the vertical axis is the black body radiation intensity (power density, logarithmic expression) per 1 nm of the bandwidth, and the horizontal axis is the wavelength.

From FIG. 13, it can be seen that the black body radiation intensity at a wavelength of 640 nm is about 1.6 × 10 ⁻³ mW / cm ² per 1 nm of bandwidth. Therefore, since the emissivity is 0.9, the self-emission intensity (mW / cm ² ) of the steel plate is represented by “0.9 × bandwidth (nm) × 1.6 × 10 ⁻³ ”.

On the other hand, from the requirement that the SN ratio is 20 or more, the laser power density required for the light cutting line is 20 times the intensity of the disturbance light, “20 × 0.9 × bandwidth (nm) × 1.6 X 10 ^-3 ". Here, since the steel plate in question has a reflectance of 0.1, the incident power to the lens is required to be 10 times, so “10 × 20 × 0.9 × bandwidth (nm) × 1. From the SN ratio, 6 × 10 ⁻³ = 0.29 bandwidth (nm) becomes the necessary laser power density (mW / cm ² ). The relationship “laser power density = 0.29 × bandwidth” is the above straight line L1.

  Further, when the relationship between the F value and the bandwidth is calculated from the relationship of F = 1 / (2 × NA) and the above equation 105, the result is as shown in FIG. From this FIG. 14, it is clear that F1.4 corresponds to a bandwidth of 18 nm when the bandwidth corresponding to the F value of the lens = 1.4 is obtained.

Therefore, when a curve L2 passing through a position of 0.8 mW / cm ² at a position of a bandwidth of 18 nm is obtained, it is as shown in FIG. Note that FIG. 15 also illustrates the straight line L1. It became clear from FIG. 15 that the position of the intersection of the straight line L1 and the curve L2 is (bandwidth, laser power density) = (7 nm, ² mW / cm ² ). As apparent from FIG. 15, under the above-described imaging conditions, the laser power density of the laser light source 11 needs to be ² mW / cm ² or more, and the upper limit value of the bandwidth of the optical band pass filter 107 Is found to be 18 nm.

Therefore, light cutting is performed for each of the condition A in which the laser power density of the laser light source 11 is fixed at 5 mW / cm ² and the bandwidth of the optical bandpass filter 107 is 7 nm and the condition B in which the bandwidth is 30 nm. The image was taken. As apparent from FIG. 15, the condition A is a condition included in the region as shown in FIG. 6B, and the condition B is a condition not included in the region.

  The obtained light-cut image is shown in FIG. 16, and an example of the cross-sectional brightness profile of the light-cut line in the thickness direction of the light-cut image is collectively shown in FIG. In FIG. 17, the vertical axis represents the luminance value of the light sectioned image, and the horizontal axis corresponds to the position in the thickness direction of the light sectioning line (the position in the vertical direction of the light sectioned image in FIG. 16). .

  As is clear from FIGS. 16 and 17, under the condition A, the contrast of the light sectioned image shown in FIG. 16 is good, and even in the cross-sectional luminance profile shown in FIG. You can see that you are concentrating. As for the condition A, when the SN ratio of the light sectioned image was calculated, 50 was exceeded.

  On the other hand, under the condition B, the contrast of the light sectioned image shown in FIG. 16 is not good, and even in the cross-sectional luminance profile shown in FIG. 17, the luminance values are widely distributed over the thickness direction of the light section line. Recognize. As for the condition B, when the SN ratio of the light sectioned image was calculated, it was about 3.5.

  In the light cutting method generally used, when generating a concavo-convex image or a luminance image from a light cutting image, in order to obtain the position of the light cutting line, the barycenter calculation of the bright line position is often performed. Therefore, under the condition B as shown in FIG. 17, even the background component is mixed in the barycenter calculation, so that an error is superimposed on the position of the light cutting line. On the other hand, under condition A, the luminance value is concentrated at the central portion, and the background component has almost no luminance value. Therefore, under the condition A, the position of the light cutting line can be accurately calculated, and the calculation accuracy of the shape calculation process can be further improved.

  Although the preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings, the present invention is not limited to such examples. It is obvious that those skilled in the art to which the present invention belongs can conceive of various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also fall within the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 1 shape measuring device 10 measuring device 11 laser light source 13 imaging device 20 arithmetic processing device 21 imaging control unit 23 image processing unit 25 display control unit 27 storage unit 101 camera body 103 lens 105 imaging element 107 optical band pass filter 201 data acquisition unit 203 Shape calculation unit 205 Result output unit

Claims (3)

A laser light source for irradiating a linear laser beam to the surface of an object that is reflecting or emitting light, and an image of a light cutting line by the laser beam on the surface of the object, A measuring device having an imaging device for generating a cut image;
An arithmetic processing unit that performs image processing on the light section image generated by the measuring device to calculate the shape of the object to be measured;
Equipped with
The imaging device is
An imaging device,
And image-side telecentric lens for forming an image of the light section lines and to the image sensing device,
An optical band pass filter having a predetermined bandwidth, disposed between the image side telecentric lens and the imaging device;
I have a,
The laser power density of the linear laser light and the bandwidth of the optical band pass filter are determined by the illuminance on the imaging surface required to image the light cutting line and the reflection or emission of the object to be measured. Determined based on the signal-to-noise ratio required for the ambient light,
The shape measurement device according to claim 1, wherein a numerical aperture according to the bandwidth of the optical band pass filter is set smaller than a numerical aperture determined by an F value of the imaging device. A laser light source for irradiating a linear laser beam to the surface of an object that is reflecting or emitting light, and an image of a light cutting line by the laser beam on the surface of the object, A measuring device having an imaging device for generating a cut image;
An arithmetic processing unit that performs image processing on the light section image generated by the measuring device to calculate the shape of the object to be measured;
Equipped with
The imaging device is
An imaging device,
An image side telecentric lens for forming an image of the light cutting line on the imaging device;
An optical band pass filter having a predetermined bandwidth, disposed between the image side telecentric lens and the imaging device;
Have
The laser power density of the linear laser light and the bandwidth of the optical band pass filter are determined by the illuminance on the imaging surface required to image the light cutting line and the reflection or emission of the object to be measured. Determined based on the signal-to-noise ratio required for the ambient light ,
The laser power density at the surface of the object to be measured is
In a plane coordinate system in which the laser power density of the linear laser light is taken on the vertical axis, and the bandwidth of the optical bandpass filter is taken on the horizontal axis,
A curve representing the relationship between the laser power density and the bandwidth at which the signal-to-noise ratio to disturbance light is constant, and the relationship between the laser power density and the bandwidth at which the brightness of the image of the light cutting line at the image plane is constant. and the curve representing the is set to the laser power density above the value corresponding to the intersection of shape measurement apparatus. The shape measuring apparatus according to claim 1 or 2 , wherein the curve representing the relationship between the laser power density and the bandwidth in which the signal-to-noise ratio to disturbance light is constant is a straight line.

Images