JP2019190889A - Calibration method - Google Patents

Abstract

To provide a calibration method that enables calibration of a high-speed camera even in a laser induced fluorescence method.SOLUTION: A calibration method is the calibration method of a high-speed camera to be used in quantifying a location and area of an inner-cylinder wet adhered to an inner wall of a transparent engine cylinder by a laser induce fluorescence method. The method is configured to: insert a columnar jig having a fluorescent paint coated in a grid shape inside the engine cylinder; irradiate the jig with laser light; measure luminance of the jig using the high-speed camera; and conduct calibration of calculating a size of a plurality of pixels including any of a fluorescent jig part having the first luminance in the luminance, and a non-fluorescent jig part having the second luminance lower than the first luminance respectively on the basis of design values about the fluorescent jig part, the non-fluorescent jig part and the grid.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a calibration method.

  In a non-combustion engine with a transparent engine cylinder, light is applied to engine lubricating oil mixed with a fluorescent substance, and the fluorescence intensity excited from the fluorescent substance is photographed with a high-speed camera, so that the thickness of the oil film Techniques for measuring are known. In particular, a technique for measuring the thickness of an oil film by a laser induced fluorescence method (LIF method) using laser light as a light source is known (see Patent Document 1 above).

JP 2017-194416 A JP 2012-002612 A

  By the way, when quantifying the position and area of fuel (so-called in-cylinder wet) adhering to the inner wall of a transparent engine cylinder using laser-induced fluorescence, in order to quantify the position and area with high accuracy, In addition, it is desirable to calibrate a high-speed camera used in the laser-induced fluorescence method. However, in the laser induced fluorescence method, it is difficult to perform calibration using a checker pattern for the reasons described below.

  First, since the checker pattern does not contain a fluorescent material, it does not fluoresce even when irradiated with laser light. For this reason, even if a checker pattern is photographed with a high-speed camera, the measurement accuracy of the checker pattern is low, and in order to improve the measurement accuracy, it is necessary to increase the voltage of the high-speed camera to amplify the light intensity. However, when the voltage of the high-speed camera is increased, noise is amplified together with the light intensity amplification. As a result, the checker pattern image obtained from the high-speed camera has many noise components, and the checker pattern cannot be measured with high accuracy. As long as the checker pattern cannot be measured accurately, calibration cannot be performed.

  Next, if the checker pattern is irradiated with laser light having a high energy intensity, there is a risk that the high-speed camera that captures the checker pattern will break down. As described above, when the measurement accuracy of the checker pattern is improved by increasing the voltage of the high-speed camera, the elements inside the high-speed camera become very sensitive. In this state, when the reflected light of the laser light enters the high-speed camera, the elements inside the high-speed camera are burned out by the reflected light, and as a result, the high-speed camera may break down.

  For these reasons, the laser-induced fluorescence method has a problem that it is difficult to calibrate a high-speed camera using a checker pattern.

  Accordingly, an object of the present invention is to provide a calibration method capable of calibrating a high-speed camera even in the laser-induced fluorescence method.

  A calibration method according to the present invention is a calibration method for a high-speed camera used when quantifying the position and area of in-cylinder wet attached to the inner wall of a transparent engine cylinder by a laser-induced fluorescence method. A cylindrical jig with paint applied in the shape of a lattice is inserted into the engine cylinder, irradiated with laser light toward the jig, and the brightness of the jig is measured using the high-speed camera. The fluorescent jig based on the fluorescent jig part having the first luminance among the luminances, the non-fluorescent jig part having the second luminance lower than the first luminance, and the design value related to the lattice. Calibration is performed to calculate the size of each of a plurality of pixels including any of the portion and the non-fluorescent jig portion.

  According to the present invention, the high-speed camera can be calibrated even in the laser-induced fluorescence method.

FIG. 1 is a flowchart showing the work process of the calibration method. FIG. 2 is a perspective view of the lattice jig and the glass cylinder. FIG. 3 is a diagram for explaining the lattice requirements. FIG. 4 is a diagram for explaining the measurement of luminance of the lattice jig. FIG. 5 is an example of a captured image of the lattice jig. FIG. 6 is a view for explaining in-cylinder wet. FIG. 7 is an example of a picked-up image of in-cylinder wet.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings with reference to FIGS.

  First, as shown in FIGS. 1 and 2, the operator who performs calibration inserts the lattice jig 10 into the glass cylinder 20 (step S101). More specifically, the operator inserts a cylindrical lattice jig 10 having a diameter D into a cylindrical glass cylinder 20 having a cylinder bore (inner diameter) D.

  The lattice jig 10 is a cylindrical jig in which the fluorescent paint 11 is applied in the shape of a lattice. As shown in FIG. 2, a fluorescent paint 11 is applied to the surface of the lattice jig 10 in the shape of a lattice. The fluorescent paint 11 is a paint that emits fluorescence by absorbing light energy of laser light. The fluorescent paint 11 may be applied to the entire surface of the lattice jig 10, or may be applied to a part of the surface of the lattice jig 10. In the present embodiment, the fluorescent paint 11 is applied to the outer peripheral surface 13 excluding the two bottom surfaces 12 from the surface of the lattice jig 10.

  As shown in the upper part of FIG. 3, the fluorescent paint 11 is applied such that the distance between the lattices is a width x (millimeter) and a height y (millimeter). Both width x and height y are design values. The design values of the width x and the height y may be the same or different. On the other hand, the line width of the fluorescent paint 11 is small with respect to both the width x and the height y. The line width of the fluorescent paint 11 may be determined by design. Although details will be described later, if the line width of the fluorescent paint 11 is an extremely small design value with respect to both the width x and the height y, there is a possibility that the measurement accuracy of the brightness is lowered and calibration cannot be performed. Therefore, it is desirable that the line width of the fluorescent paint 11 is about a fraction to a tenth of both the width x and the height y.

  Moreover, the fluorescent paint 11 is applied in the shape of a lattice so that a predetermined lattice requirement is satisfied. This predetermined lattice requirement is shown in the lower part of FIG. Absorption energy E1 is energy that fluorescent paint 11 can absorb light energy of laser light. The fluorescent energy E2 is energy that the fluorescent paint 11 has after absorbing the light energy of the laser light. In this way, the fluorescent paint 11 is applied in the shape of a lattice so that the lattice requirement that the wavelength at which the energy intensity of the fluorescent energy E2 is maximum is longer than the wavelength at which the energy intensity of the absorbed energy E1 is maximum. Is done.

  On the other hand, as shown in FIG. 2, the glass cylinder 20 has a cylindrical shape having a cylinder bore D. The height of the glass cylinder 20 may be the same as or different from the height of the lattice jig 10. The glass cylinder 20 is a transparent glass engine cylinder. In the present embodiment, the glass cylinder 20 will be described as an example. However, the material of the engine cylinder is not limited to glass as long as it is a transparent engine cylinder, and materials other than glass may be used. As shown in FIG. 2, since the lattice jig 10 has a diameter D and the glass cylinder 20 has a cylinder bore D, an operator can insert the lattice jig 10 into the glass cylinder 20.

  When the step S101 is completed, as shown in FIGS. 1 and 4, the operator irradiates the grating jig 10 with the laser beam LSR using the laser irradiation device 100 (step S102). The laser irradiation apparatus 100 is an apparatus that irradiates a laser beam LSR of a diffusion laser (specifically, a fourth harmonic diffusion laser that is deep ultraviolet). The laser irradiation apparatus 100 is installed at a position away from the glass cylinder 20 in a state where the optical axis is perpendicular to the glass cylinder 20. Since the lattice jig 10 is stored in the glass cylinder 20 by the process of step S101, the operator moves the lattice jig toward the lattice jig 10 stored in the glass cylinder 20 as shown in FIG. The laser beam LSR is irradiated toward the tool 10. Since the glass cylinder 20 is transparent, the laser light LSR passes through the glass cylinder 20 and enters the grating jig 10. Thereby, the fluorescent paint 11 is excited and emits fluorescence.

  A cylinder head 30 including an intake valve 31, an exhaust valve 32, an injector 33, a spark plug 34, an intake pipe 35, and an exhaust pipe 36 is installed above the glass cylinder 20, but at the stage of step S102. The cylinder head 30 may not be installed.

  When the process of step S102 is completed, as shown in FIGS. 1 and 4, the operator measures the luminance of the lattice jig 10 using the high-speed camera 200 (step S103). The high-speed camera 200 is preferably a high-sensitivity high-speed camera that can amplify the light intensity. The high-speed camera 200 is installed at a position away from the glass cylinder 20 with the optical axis perpendicular to the glass cylinder 20. When the high-speed camera 200 measures the luminance of the lattice jig 10, two types of luminance are measured. One of the two luminances is the luminance of the portion where the fluorescent paint 11 is applied, and the other of the two luminances is the luminance of the portion where the fluorescent paint 11 is not applied. The luminance of the portion where the fluorescent paint 11 is not applied is lower than the luminance of the portion where the fluorescent paint 11 is applied because it does not emit fluorescence. In other words, a portion where the fluorescent paint 11 is not applied is dark, and a portion where the fluorescent paint 11 is applied is bright. Thereby, as shown in FIG. 5, in the captured image IM based on the brightness measured by the high-speed camera 200, the fluorescent jig portion IM1 in which the fluorescent paint 11 is fluorescent and the non-fluorescent jig in which the fluorescent paint 11 is not fluorescent. The part IM2 appears. The captured image IM is displayed on a terminal device 300 such as a PC (Personal Computer).

  When the step S103 is completed, as shown in FIGS. 1 and 5, the operator calculates the size of the pixel using the terminal device 300 (step S104). As shown in FIG. 5, both the fluorescent jig part IM1 and the non-fluorescent jig part IM2 are constituted by a plurality of pixels PXL. Here, as described above, since the numerical values of both the width x and the height y are determined by design, the size of one pixel PXL can be calculated.

  For example, the size in the width direction of one pixel PXL is ½ of the width x in this embodiment. Similarly, the size in the height direction of one pixel PXL is one third of the height y in this embodiment. Thus, based on the design values of the width x and the height y that define the distance between the non-fluorescent jig part IM2 and the lattice, the actual measurement value of one pixel PXL constituting the non-fluorescent jig part IM2 Can be calculated. By using the same method, the actual measurement value of the pixel PXL of the fluorescent jig portion IM1 can also be calculated based on the design value that defines the grid width corresponding to the line width of the fluorescent jig portion IM1 and the fluorescent paint 11.

  Since the grating jig 10 has a cylindrical shape, the captured image IM is more distorted due to aberration toward the end in the width direction, and the width of the non-fluorescent jig portion IM2 appearing in the captured image IM becomes narrower. . For the same reason, the width of the fluorescent jig part IM1 is also narrowed. Therefore, not only the size of one pixel PXL is calculated, but the sizes of all the pixels PXL constituting either the non-fluorescent jig part IM2 or the fluorescent jig part IM1 appearing in the captured image IM. Are calculated respectively. Thereby, it is possible to perform calibration with high accuracy in consideration of distortion due to aberration.

  When the step S104 is completed, as shown in FIGS. 1 and 6, the operator operates the non-combustion engine 400 using the terminal device 300 and images the in-cylinder wet 40 using the high-speed camera 200. (Step S105). More specifically, when the step S104 is completed, the operator takes out the lattice jig 10 from the glass cylinder 20, places the cylinder head 30 on the glass cylinder 20, and creates the non-combustion engine 400.

  When the creation of the non-combustion engine 400 is completed, the operator uses the terminal device 300 to start the operation of the non-combustion engine 400. As a result, the non-combustion engine 400 performs the same movement as the combustion engine without combustion. Therefore, for example, the intake valve 31 is opened, and the fuel F is injected from the injector 33 into the glass cylinder 20. This fuel F contains a fluorescent substance. More specifically, the fuel F contains a fluorescent material. On the other hand, since the non-combustion engine 400 does not burn the fuel F, the fuel F does not have to include a combusting component.

  The fuel F injected from the injector 33 adheres to the inner wall of the glass cylinder 20 and becomes the in-cylinder wet 40. Since the fluorescent substance is mixed in the fuel F, when the laser beam LSR is irradiated from the laser irradiation device 100, the in-cylinder wet 40 absorbs the light energy of the laser beam LSR and emits fluorescence. In this way, the operator images the in-cylinder wet 40 that emits fluorescence using the high-speed camera 200. Thereby, as illustrated in FIG. 6, the captured image IMw captured by the high-speed camera 200 is displayed on the terminal device 300. In particular, a wet region ARw corresponding to the in-cylinder wet 40 appears in the captured image IMw.

  When the step S105 is completed, as shown in FIGS. 1 and 7, the operator uses the terminal device 300 to derive the position and area of the in-cylinder wet 40 from the captured image IMw (step S106). As shown in FIG. 7, the captured image IMw includes a wet area ARw corresponding to the in-cylinder wet 40. Further, a reference position serving as a reference for quantifying the position and area of the in-cylinder wet 40 on the captured image IMw by the bore center that is the center of the cylinder bore of the glass cylinder 20 and the lower surface of the head that is the lower surface of the cylinder head 30. Po (0, 0) is determined in advance.

  In this way, if the reference position Po (0, 0) is determined, the size of one pixel PXL is calculated, and therefore, the position P (Px, 0) away from the reference position Po (0, 0). Py) can be derived from measured values. Further, by using the actual measurement value of the position P (Px, Py), the area A of the rectangular area ARz determined by the reference position Po and the position P (Px, Py) is also derived as an actual measurement value by Px × Py. Can do. In particular, if the rectangular area ARz is used a plurality of times, and the area is derived and added each time, the area of the wet area ARw can be derived with an actual measurement value. Thus, the position and area of the in-cylinder wet 40 can be quantified.

  As described above, according to the present embodiment, in the calibration method of the high-speed camera 200 used when quantifying the position and area of the in-cylinder wet 40 attached to the inner wall of the transparent glass cylinder 20 by the laser-induced fluorescence method, First, a cylindrical lattice jig 10 in which the fluorescent paint 11 is applied in the shape of a lattice is inserted into the glass cylinder 20. Next, laser light is irradiated toward the grating jig 10, and the luminance of the grating jig 10 is measured using the high-speed camera 200. Based on the fluorescent jig portion IM1 having the first luminance, the non-fluorescent jig portion IM2 having the second luminance lower than the first luminance, and the design value relating to the lattice, the fluorescent jig portion Calibration is performed to calculate the size of each of the plurality of pixels PXL including either IM1 or the non-fluorescent jig portion IM2. Thereby, the high speed camera 200 can be calibrated also in the laser induced fluorescence method. In particular, according to the present embodiment, the high-speed camera 200 can be calibrated without using a checker pattern, so that the risk of the high-speed camera 200 being broken is also avoided.

  Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. It can be changed. For example, in the above-described embodiment, the distance between lattices and the width of the lattice are used as design values related to the lattice. However, the design values are not limited to the distance between the lattices and the width of the lattice, and other various design values are used. May be.

DESCRIPTION OF SYMBOLS 10 Lattice jig 11 Fluorescent paint 20 Glass cylinder 30 Cylinder head 40 In-cylinder wet 100 Laser irradiation device 200 High speed camera 300 Terminal device 400 Non-combustion engine

Claims (1)

A calibration method for a high-speed camera used when quantifying the position and area of the in-cylinder wet attached to the inner wall of a transparent engine cylinder by a laser-induced fluorescence method,
A cylindrical jig coated with a fluorescent paint in the shape of a lattice is inserted into the engine cylinder,
Irradiate laser light toward the jig,
Measure the brightness of the jig using the high-speed camera,
The fluorescent jig part based on the fluorescent jig part having the first luminance among the luminances, the non-fluorescent jig part having the second luminance lower than the first luminance, and the design value relating to the lattice. And performing calibration to calculate the size of each of the plurality of pixels including any of the non-fluorescent jig parts,
A calibration method characterized by that.

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