JP6947112B2 - Calibration method - Google Patents

Description

The present invention relates to a calibration method.

In a non-combustion engine with a transparent engine cylinder, the thickness of the oil film is obtained by irradiating the engine lubricating oil mixed with the fluorescent substance with light and photographing the fluorescence intensity excited by the fluorescent substance with a high-speed camera. The technology to measure is known. In particular, a technique for measuring the thickness of an oil film by a laser-induced fluorescence method (LIF method) using a laser beam as a light source is known (see Patent Document 1 above).

JP-A-2017-194416 Japanese Unexamined Patent Publication No. 2012-002612

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 by using laser-induced fluorescence, in order to quantify the position and area accurately, it is necessary in advance. In addition, it is desirable to calibrate the high-speed camera used in the laser-induced fluorescence method. However, in the laser-induced fluorescence method, it is difficult to perform calibration using the checker pattern for the reasons described below.

First, since the checker pattern does not contain a fluorescent substance, it does not fluoresce even when irradiated with laser light. Therefore, even if the checker pattern is photographed by the 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, the noise is amplified along with the amplification of the light intensity. As a result, the checkered pattern image obtained from the high-speed camera has a large amount of noise components, and the checkered pattern cannot be measured accurately. As long as the checkered pattern cannot be measured accurately, calibration cannot be performed.

Next, if the checker pattern is irradiated with a laser beam 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 voltage of the high-speed camera is increased to improve the measurement accuracy of the checker pattern, the elements inside the high-speed camera become very sensitive. If the reflected light of the laser beam enters the high-speed camera in such a state, the elements inside the high-speed camera are burnt out by the reflected light, and as a result, the high-speed camera may be damaged.

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

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

The calibration method according to the present invention is a calibration method for a high-speed camera used when quantifying the position and area of the in-cylinder wet adhering to the inner wall of a transparent engine cylinder by a laser-induced fluorescence method. A cylindrical jig in which the paint is applied in a lattice shape is inserted into the engine cylinder, laser light is irradiated toward the jig, and the brightness of the jig is measured using the high-speed camera. Based on the fluorescent jig portion having the first brightness among the brightness, the non-fluorescent jig portion having the second brightness lower than the first brightness, and the design value for the lattice, the fluorescent jig It is characterized in that calibration is performed to calculate the sizes 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 also in the laser-induced fluorescence method.

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

Hereinafter, embodiments for carrying out the present invention will be described with reference to FIGS. 1 to 7 with reference to the drawings.

First, as shown in FIGS. 1 and 2, the calibrating operator inserts the grid jig 10 into the glass cylinder 20 (step S101). More specifically, the operator inserts the cylindrical lattice jig 10 having a diameter D into the 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, the fluorescent paint 11 is applied to the surface of the lattice jig 10 in the shape of a lattice. The fluorescent coating material 11 is a coating material that absorbs the light energy of laser light to emit fluorescence. 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 so that the distances between the grids are width x (millimeters) and height y (millimeters). Both the width x and the 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 also be determined by design. Although the details will be described later, if the line width of the fluorescent paint 11 becomes an extremely small design value for both the width x and the height y, the brightness measurement accuracy may decrease and calibration may not be possible. Therefore, it is desirable that the line width of the fluorescent coating material 11 is about one-fifth to one-tenth of the width x and the height y.

Further, the fluorescent coating material 11 is applied to the shape of a grid so that a predetermined grid requirement is satisfied. This predetermined grid requirement is shown in the lower part of FIG. The absorption energy E1 is energy that the fluorescent coating material 11 can absorb the light energy of the laser beam. The fluorescence energy E2 is the energy possessed by the fluorescent coating material 11 after absorbing the light energy of the laser beam. In this way, the fluorescent coating material 11 is applied to the shape of the lattice so that the lattice requirement that the wavelength at which the energy intensity of the fluorescence energy E2 is maximized is longer than the wavelength at which the energy intensity of the absorbed energy E1 is maximized is satisfied. Will be 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 grid 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, but the material of the engine cylinder is not limited to glass as long as it is a transparent engine cylinder, and a material other than glass may be used. As shown in FIG. 2, since the grid jig 10 has a diameter D and the glass cylinder 20 has a cylinder bore D, the operator can insert the grid jig 10 into the glass cylinder 20.

When the step S101 is completed, as shown in FIGS. 1 and 4, the operator uses the laser irradiation device 100 to irradiate the lattice jig 10 with the laser beam LSR (step S102). The laser irradiation device 100 is a device that irradiates the laser light LSR of a diffusion laser (specifically, a diffusion laser of the fourth harmonic that is deep ultraviolet). The laser irradiation device 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 step of step S101, as shown in FIG. 4, the operator moves the lattice jig 10 toward the lattice jig 10 in the state of being stored in the glass cylinder 20. The laser beam LSR is irradiated toward the tool 10. Since the glass cylinder 20 is transparent, the laser beam LSR passes through the glass cylinder 20 and is incident on the grid jig 10. As a result, the fluorescent coating material 11 is excited to emit 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 is installed. , The cylinder head 30 may not be installed.

When the step S102 is completed, as shown in FIGS. 1 and 4, the operator measures the brightness of the grid jig 10 using the high-speed camera 200 (step S103). It is preferable to use a high-sensitivity high-speed camera capable of amplifying the light intensity for the high-speed camera 200. The high-speed camera 200 is installed at a position away from the glass cylinder 20 so that the optical axis is perpendicular to the glass cylinder 20. When the high-speed camera 200 measures the brightness of the grid jig 10, it roughly divides the brightness into two. One of the two luminances is the brightness of the portion to which the fluorescent paint 11 is applied, and the other of the two luminances is the brightness of the portion to which the fluorescent paint 11 is not applied. The brightness of the portion to which the fluorescent paint 11 is not applied is lower than the brightness of the portion to which the fluorescent paint 11 is applied because it does not emit fluorescence. In other words, the portion to which the fluorescent paint 11 is not applied is dark, and the portion to which the fluorescent paint 11 is applied is bright. As a result, as shown in FIG. 5, the captured image IM based on the brightness measured by the high-speed camera 200 includes 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. Partial IM2 appears. The captured image IM is displayed on a terminal device 300 such as a PC (Personal Computer).

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

For example, the size of one pixel PXL in the width direction is half of the width x in the present embodiment. Similarly, the size of one pixel PXL in the height direction is one-third of the height y in this embodiment. In this way, based on the design values of the width x and the height y that define the distance between the non-fluorescent jig portion IM2 and the lattice, the measured values of one pixel PXL constituting the non-fluorescent jig portion IM2. Can be calculated. By the same method, the measured value of the pixel PXL of the fluorescent jig portion IM1 can be calculated based on the design value in which the width of the grid corresponding to the line width of the fluorescent jig portion IM1 and the fluorescent paint 11 is determined.

Since the grid jig 10 has a cylindrical shape, the captured image IM is 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 portion IM1 is also narrowed. Therefore, not only the size of one pixel PXL is calculated, but the sizes of all the plurality of pixels PXL constituting either the non-fluorescent jig portion IM2 or the fluorescent jig portion IM1 appearing in the captured image IM. Are calculated respectively. As a result, highly accurate calibration can be performed 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 and places the cylinder head 30 on the glass cylinder 20 to create the non-combustion engine 400.

After creating the non-combustion engine 400, the operator starts the operation of the non-combustion engine 400 using the terminal device 300. As a result, the non-combustion engine 400 operates in the same manner as the combustion engine without combustion. Therefore, for example, the intake valve 31 is opened, and the fuel F is injected into the glass cylinder 20 from the injector 33. This fuel F contains a fluorescent substance. More specifically, the fuel F contains a fluorescent substance. On the other hand, since the non-combustion engine 400 does not burn the fuel F, the fuel F does not have to contain a combustible component.

The fuel F injected from the injector 33 adheres to the inner wall of the glass cylinder 20 and becomes an in-cylinder wet 40. Since a fluorescent substance is mixed in the fuel F, when the laser light LSR is irradiated from the laser irradiation device 100, the in-cylinder wet 40 absorbs the light energy of the laser light LSR and emits fluorescence. In this way, the operator uses the high-speed camera 200 to image the fluorescent in-cylinder wet 40. As a result, as shown 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 this 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 region ARw corresponding to the in-cylinder wet 40. Further, the bore center, which is the center of the cylinder bore of the glass cylinder 20, and the lower surface of the head, which is the lower surface of the cylinder head 30, provide a reference position as a reference when quantifying the position and area of the in-cylinder wet 40 on the captured image IMw. Po (0,0) is set in advance.

If the reference position Po (0,0) is determined in this way, the size of one pixel PXL is calculated, so the position P (Px, Py) can be derived as an actually measured value. Further, by using the measured value of the position P (Px, Py), the area A of the rectangular region ARz determined by the reference position Po and the position P (Px, Py) can also be derived by the measured value by Px × Py. Can be done. In particular, if the rectangular region ARz is used a plurality of times and the area is derived and added each time, the area of the wet region ARw can be derived by the measured value. In this way, 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 adhering to the inner wall of the transparent glass cylinder 20 by the laser-induced fluorescence method. First, a cylindrical lattice jig 10 coated with the fluorescent paint 11 in a lattice shape is inserted into the glass cylinder 20. Next, the laser beam is irradiated toward the grid jig 10, and the brightness of the grid jig 10 is measured using the high-speed camera 200. Then, based on the fluorescent jig portion IM1 having the first brightness among the brightness, the non-fluorescent jig portion IM2 having the second brightness lower than the first brightness, and the design value regarding the lattice, the fluorescent jig portion Calibration is performed to calculate the sizes of a plurality of pixels PXL including either IM1 and the non-fluorescent jig portion IM2. As a result, the high-speed camera 200 can be calibrated even in the laser-induced fluorescence method. In particular, according to the present embodiment, since the high-speed camera 200 can be calibrated without using the checker pattern, the risk of the high-speed camera 200 breaking down can be 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 modifications are 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 grids and the width of the grid are used as design values for the grid, but the design values are not limited to the distance between grids and the width of the grid, and various other design values are used. You may.

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)

This is a calibration method for high-speed cameras used to quantify the position and area of in-cylinder wet that adheres to the inner wall of a transparent engine cylinder by laser-induced fluorescence.
A cylindrical jig coated with fluorescent paint in the shape of a grid is inserted into the engine cylinder.
Irradiate the jig with a laser beam and
The brightness of the jig is measured using the high-speed camera.
The fluorescent jig portion based on the fluorescent jig portion having the first brightness among the brightness, the non-fluorescent jig portion having the second brightness lower than the first brightness, and the design value for the lattice. And calibrate to calculate the size of each of the plurality of pixels including any of the non-fluorescent jig portions.
A calibration method characterized by that.

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