JPS6126937Y2 - - Google Patents

Description

[Detailed description of the invention] This invention is a speedometer measurement method using a trail.
This invention relates to the improvement of a device for photographing the trajectory of fine particles.

When observing a flow field in a model experiment, etc., fine particles (e.g. mica, body warmer ash, baby powder) are suspended and illuminated with light from a light source (incandescent bulb, mercury lamp, laser, etc.), and the exposure time (T) is
is determined appropriately, the trajectory of the particles is photographed, and the velocity of each particle is determined from the trajectory length (L) of each particle, V = (L/
A method is used to measure T).

FIG. 1 shows the arrangement of a measuring device that uses a laser as illumination light among the devices for carrying out this measuring method.

That is, illumination light 02 is emitted from a laser light source 01, the light is expanded into a planar shape by a lens 03, the flow field 04 of the measurement cross section is irradiated with the laser light, and the trajectory of the particles is photographed by a camera 05.

In this device, the light intensity of the illumination light is almost constant within the exposure time for photographing, so it is impossible to distinguish between the starting point and the ending point of the photographed particle trajectory. Therefore, although the velocity can be measured, it is not possible to determine whether the flow direction is positive or negative.

In particular, in a turbulent flow field, changes in the flow direction are irregular, making it difficult to estimate by theory or experience.

The present invention eliminates these drawbacks, and uses a light source and a camera to suspend particles in a fluid flow field, illuminate them with light, and take photographs to measure the velocity of the trail. A trajectory velocity measuring device that performs measurement includes a rotary optical chopper having a window disposed in front of the light source, a filter that reduces the amount of light transmitted through the window of the chopper, and a filter that reduces the amount of light transmitted through the window of the chopper. It is characterized by consisting of a photoelectric converter that extracts a portion of the light that hits it, and a pulse generator that is activated by the output of the converter to drive the shutter of the camera, and its purpose is to convert the light that hits the particles. To provide a trail velocity measuring device that changes the amount of particles within the time the shutter is open, distinguishes the starting point and ending point of photographed particles, and measures not only the velocity but also the direction of the flow. be.

In other words, in this invention, a rotating optical chipper is placed in front of the light source, and the amount of light is changed by a filter attached to the window of the chipper, so that fine particles
The amount of light hitting the shutter changes while the shutter is open, and the particles photographed also vary in density.

Therefore, the start and end points of the particle can be distinguished.

In addition, in this invention, due to the light hitting the filter,
Since the shutter of the camera is driven through a photoelectric converter and a pulse generator, the shutter and light are synchronized and it is possible to prevent missing a photograph.

The present invention will now be described with reference to an embodiment of the apparatus shown in FIGS. 2 and 3.

Reference numeral 11 is a light source, for example, an argon laser that emits light with a wavelength of 4880 Å, which passes through a window 27 opened in an optical chopper 16 (described later), passes through a plate glass 17, and is magnified into a planar shape by a lens 13. The flow field 14 to be measured is illuminated.

The chopper 16 is made of a disk-like member and is rotated by a motor 32, the rotational speed of which is set by a dial 19 of a rotational speed regulator 18.

Further, half of the window 27 of the optical chopper 16 is transparent, and a gray filter 29 with a light transmittance of about 50% is installed in the other half.

Reference numeral 20 denotes a photoelectric converter that operates by receiving a portion (approximately 5%) of the light that has passed through the optical chopper 16 and is reflected by the plate glass 17, and the photoelectrically converted electric signal 21 is sent to the pulse generator 22. to go into.

The pulse generator 22 receives the electrical signal 21 and generates a pulse signal 23 for operating a pulse drive shutter 24 placed in front of the camera 15.

Note that 25 is a knob for adjusting the shutter speed, which is adjusted according to the rotation speed of the optical chopper 16, and an interference filter 26 is a knob for adjusting the shutter speed.
This is to remove light from sources other than 1, and uses an interference filter with a center wavelength of 4880 Å.

Further, 31 is a reset button, and unless it is reset, the pulse generator 22 will not generate the pulse signal 23 even if the electric signal 21 is input.

First, light is generated from the light source 11, and the dial 1
9 and the optical chopper 16 via the rotation speed adjuster 18.
Rotate at the appropriate speed. If the rotation direction at this time is the direction of the arrow 30 shown in FIG.
The light applied to 4 becomes as shown in FIG. 4 for each rotation.

Next, when the shutter of the camera 15 is opened and the reset button 31 is pressed, a portion of the light that passes through the window 27 of the optical chopper 16 immediately after that is reflected by the plate glass 17, and the photoelectronic converter 20 and the pulse generator 2
2, the pulse drive shutter 24 opens for a certain period of time and then closes.

Finally, when the shutter of the camera 15 is closed, one shooting session is completed.

FIG. 5 shows a photograph of the wake of a cylindrical body using the apparatus of this embodiment. The direction of the flow can be confirmed by the trajectory of the particles 41 during the time they were illuminated by the light chopper 16 and their brightness.

As described above, in this embodiment, a window 27 is provided on the rotating optical chopper 16, half of which passes through the window 27, and a filter 29 that transmits 50% is attached to the remaining part, so that the intensity of light increases by 3 during one rotation of the optical chopper 16. Since the shutter of the camera 15 is turned off between the steps, the starting point of the trail of the particles is photographed brightly and the ending point is darkly photographed, making it possible to measure not only the speed but also the direction of the flow.

Further, since a plate glass 17 is provided and a part of the light hitting the flow field 14 is extracted and the shutter is opened and closed, the shutter is perfectly synchronized and no photograph is missed.

Furthermore, a pulse-driven shutter 25 independent of the camera 15 is provided, and a reset button 31 is attached to the pulse generator 21 so that light enters the camera 15 only once when necessary, so unless you are careless, double exposure is not possible. can be prevented.

[Brief explanation of the drawing]

Fig. 1 is a schematic explanatory diagram of a conventional measuring device, Fig. 2 is a schematic explanatory diagram of a measuring device showing an embodiment of the present invention, Fig. 3 is a cross-sectional view of Fig. 2, and Fig. 4 is a flow field diagram. Figure 5 is a diagram showing the relationship between the amount of light hitting the cylinder and the time, and is a photograph of the field behind the cylinder. 11: Light source, 14: Flow field, 15: Camera, 1
6: Optical chopper, 17: Plate glass, 20: Photoelectric converter, 22: Pulse generator, 24: Pulse drive shutter, 27: Window, 29: Filter, 41: Fine particles. 〓〓〓〓〓

Claims (1)

[Scope of utility model registration request] In a trail velocity measurement device that has a light source and a camera, and measures the velocity of a trail by suspending particles in a fluid flow field and photographing them by shining light on them, there is a light source in front of the light source. a rotary optical chopper having a window; a filter that reduces the amount of light transmitted through the window of the chopper;
A trail velocity measuring device comprising: a photoelectric converter that extracts a portion of the light that hits the filter; and a pulse generator that is activated by the output of the converter to drive the shutter of the camera.