JPH0492999A - Travelling object discriminating device - Google Patents

Abstract

PURPOSE:To discriminate a distant travelling object by reflecting an incident light to the same direction as well as optically scanning a reflecting means composed of a bar code symbol peculiar to the travelling object, and photodetecting, signal-processing and identifying the detected light. CONSTITUTION:When a light beam from an optical scanning means 2 is made incident to a reflecting means 1 provided with the specific position of the travelling object, it is reflected to the same direction. A reflected light is photoelectric- converted in a photodetecting means 4 after removing a background light in a filter 3. The means 4 and 2 are placed at an optical conjugate position with a light source and made as the reflected light of the same route as a scanning light. A electric signal converted from an optical signal turns to the bar code signal of the means 1, is processed at a signal processing identifying means 5, and identifies a code symbol peculiar to each travelling object provided with the means 1. Thus, even when the reflecting means 1 is at the far distance, it is possible to read out the code symbol of each travelling object and process it without the influence of the background.

Description

[Detailed Description of the Invention] [Summary] Regarding a device for identifying the identity of a moving object such as a car, the object is to be able to easily identify a moving object from a distance regardless of the background. A reflecting means installed at a predetermined position on a moving object and reflecting incident light in the same direction and onto the moving object as a patented barcode symbol; and an optical scanning device that scans the reflecting means with a light beam having a predetermined beam diameter. means, a light detection means arranged on an optically conjugate plane with the light source of the light scanning means and converting the signal light from the reflection means (1) into an electrical signal, and processing and identifying the output signal of the light detection means. It consists of signal processing and identification means.

[Industrial application field]

The present invention relates to a mobile object identification device, and particularly to a device for identifying the identity of a mobile object such as an automobile.

Today, there is a great need for identification devices that serve as the basis for consistently managing the history of automobiles and the like from manufacture and sale to scrapping in production lines.

[Conventional technology]

Conventionally, the following two types of identification devices have been considered as this type of identification device.

■One method is to use a television camera to read the serial number stamped on the vehicle body for identification. In this method, after performing a series of preprocessing such as noise removal, background and number segmentation, binarization, and thinning from the grayscale original image, the features of each number are extracted and recognized. It is something.

■The other type is a device that uses black and white barcodes (see Figure 5), which are currently widely distributed for managing food products, miscellaneous goods, etc. The symbol on this barcode is
C1 is given the name EAN in Europe and JAN in Japan, but both are made of the same and compatible code system.

[Problem to be solved by the invention] In the above conventional example (■), the processing is complicated and the equipment is large-scale.In addition, the background is complicated and the serial number is blurred by dust etc. or is cut off. The problem is that the recognition rate decreases.

Further, in conventional example (2), although a high recognition rate can be ensured relatively easily, the desired recognition rate cannot be obtained even if a black and white barcode is used as is for identifying a moving object.

This is because the scanning distance for a barcode installed on a moving object is much longer than the scanning distance for a barcode on a product in a store's POS system, and therefore the reflected signal strength of the former is extremely weak compared to the latter. However, there is a drawback that a signal-to-noise ratio (S/N) suitable for a certain identification rate cannot be secured.

Therefore, regardless of the background, it is an object of the present invention to realize a device that can identify moving objects in containers even from a remote location.

[tJ, means to solve the problem]

In order to achieve the above object, a moving object identification device according to the present invention is installed at a predetermined position of a moving object and directs incident light in the same direction and in a manner specific to the moving object, as shown in principle in FIG. reflective means 1 for reflecting as a barcode symbol;
A light scanning means 2 for scanning the reflecting means 1 with a light beam having a predetermined beam diameter; It is provided with a photodetection means 4 for converting and a signal processing/identification means 5 for processing and identifying the output signal of the photodetection means (4).

[For production]

In the present invention shown in FIG. 1, when a light beam having a predetermined beam diameter is incident on the reflection means 1 installed at a predetermined position of a moving body from the optical scanning means 2, the reflection means 1 reflect in the direction.

Incidentally, the reflected light from the reflecting means 1 can be filtered by a filter 3 to remove background light other than the signal light.

Then, the reflected light from the reflection means 1 is given to the photodetection means 4 and photoelectrically converted.

Since the light detection means 4 is placed at an optically conjugate position with the light source of the light scanning means 2, it receives the reflected light along the same path as the scanning light, so that the electrical signal converted from the optical signal is transmitted to the bar of the reflection means 1. The signal becomes a code signal, and is subjected to signal processing in the signal processing/identification means 5 to identify a code/symbol unique to each moving object provided on the reflecting means 1.

In this way, even if the reflecting means 1 is located far away, the light beam can accurately read and process the code symbols of each moving object without being affected by the background.

〔Example〕

FIG. 2 shows an embodiment of the reflecting means 1 shown in FIG. 1, and FIG. 2(a) shows the overall appearance of one barcode symbol. A barcode equivalent to the barcode shown in FIG. 5 is formed by aggregating a plurality of barcodes.

In addition, FIG. 5B is an enlarged view of the corner cube 10 forming one barcode shown in FIG.
, and surfaces 10-3 are made to form an angle of 90'' with each other, so that the light incident on this corner cube 10 is reflected at the same angle, resulting in "retro reflection".
(meaning that light is reflected parallel to the direction of incident light). In this case, if there is an error in the mutual surface angles with respect to 90°, the effective light will decrease by that amount, but if we assume that the surface angles are approximately ideal, then the normal Compared to the case where a barcode is used, the S/N is 30 dB, which is expected to be an improvement effect of about 30 times in terms of distance.

This "retro-reflective" barcode eliminates the need to process each reflector element from glass material, as shown in Figure 2 (C
) As shown in (+) in the same figure, if you prepare three cutting tools 11 with cutting edges of 90° and cut the metal surfaces so as to draw an equilateral triangle at an angle of 60° to each other, the three surfaces shown in (+)) in the same figure will be obtained. 10-1
, surface 10-2, and surface 10-3 can form a reflector group in which the surfaces 10-2 and 10-3 form an angle of 90 degrees with each other. Incidentally, the black dots shown in FIG. 2C indicate the vertices of each corner cube 10 after cutting.

A retro reflector can be obtained easily and inexpensively by molding the thus-produced product into a plastic mold, and then adding a reflective coating and a protective plate to prevent staining.

This is then processed into a predetermined barcode and placed at an appropriate position on the moving object. In this case, the barcode shown in Figure 5 is coded according to the width of each bar, so
Depending on the required width, one barcode consisting of many corner cube groups as shown in FIG. 2(a) can be created.

FIG. 3 shows an optical system for incident light and reflected light with respect to the barcode 1. The optical scanning means 2 in FIG. lens 22 and collimator lens 22
It is composed of a scanning mirror (polygon mirror or galvano mirror) 23 that scans the output light of the scanning mirror 25, and a scanning lens 24 that makes the scanning by the scanning mirror 25 linear.

Note that 25 is a beam that transmits the scanning light from the scanning mirror 23 and reflects the reflected light from the reflector 1 to the photodetector 4.
It's a sprinter.

In such an optical system, a predetermined beam smaller than the minimum width of the barcode 1 is scanned from the laser 21 via the collimator lens 22 by the scanning mirror 23 and is incident on the retroreflective barcode l from the scanning lens 2. A light beam with a diameter is coded according to the symbol of the barcode and reflected, but this reflected light (signal light)
follows the same path as the scanning path and forms an image on the scanning mirror 23 at the same position as the transmitted light beam.

That is, since the light emitted from the scanning mirror 23 is reflected by the barcode 1 and converged on the scanning mirror 23 again, the scanning mirror 2
3 and the barcode 1 are in an optically conjugate position, therefore, even though the scanning mirror 23 rotates, the imaging position does not change.

However, since it is not possible to actually receive light with this, barcode 1
If the reflected light from the mirror 23 is reflected by the beam splinter 25 and guided through the filter (for example, a spatial filter) 3 to the photodetector 4 arranged at the same optically conjugate position, the light will be transmitted despite the rotation of the mirror 23. The amount of light received by detector 4 does not change and S/
Good light reception of N becomes possible.

In addition, the filter 3 is a circular opening with a suitable hole diameter, and is used to block unnecessary stray light other than the reflected light from the barcode 1, and is also set at a substantially conjugate plane in front of the photodetector 4. As a result, fluctuations are small and S
/N is possible. Note that even without using the filter 3, for example, the optical signal is modulated by a predetermined signal (phase modulation, frequency modulation, etc.), demodulated by a photodetector, and the demodulated signal is used as a detection output to eliminate the influence of unnecessary stray light. can be eliminated.

Note that the scanning speed V on the barcode 1 is usually v=d (
f-tanωt)/dt (where f is the focal length of the scanning lens 24, ω is the angular velocity of the scanning mirror 23, and L is time), and is dependent on the angle of the chief ray and is a constant velocity independent of the angle. isn't it. Therefore, if a constant scanning speed is required, the so-called f.
This can be achieved by using a θ lens as the scanning lens 24.

The signal photoelectrically converted by the photodetector 4 is amplified by the processing section of the signal processing/identification section 5, then waveform-shaped, and after normalizing the pulse width, the identification section converts the signal into a pre-stored code table. The matching code is sent as identification data.

When the present invention is applied to an automobile, the posture of the object and the scanning plane of the identification device can be set on approximately the same plane, so one-dimensional scanning in a fixed direction is sufficient, and the device configuration is simplified. Furthermore, if it is limited to such one-dimensional scanning, the scanning beam does not necessarily have to be a spot; for example, it can be a fan-shaped beam that spreads in the longitudinal direction of the barcode using a cylindrical lens, as shown in Figure 4. You can also do it. If this fan-shaped beam is used, the beam direction control accuracy in the longitudinal direction can be made much looser than that of a spot beam.

〔Effect of the invention〕

According to the mobile object identification device according to the present invention described above, the reflecting means 1 that reflects incident light in the same direction and constitutes a barcode symbol unique to the mobile object is optically scanned, and this is optically detected. Since it is configured for signal processing and identification,
It becomes possible to identify moving objects that are far away.

[Brief explanation of the drawing]

FIG. 1 is a diagram conceptually showing a moving object identification device according to the present invention, FIG. 2 is a diagram showing an embodiment of a reflecting means used in the present invention, and FIG. 3 is a diagram conceptually showing a moving object identification device according to the present invention. FIG. 4 is a diagram showing an example of an optical system of a moving object identification device; FIG. 4 is a diagram showing a modified example of the light beam used in the present invention; FIG. 5 is a diagram showing a bar code for boat fishing. , is. In FIG. 1, 1... Reflection means, 2... Light scanning means, 3... Filter, 4... Light detection means, 5... Signal processing/identification means. In the figures, the same reference numerals indicate the same or corresponding parts. Figure 1

Claims (5)

[Claims] (1) A reflecting means (1) installed at a predetermined position on a moving object to reflect incident light in the same direction as a barcode symbol unique to the moving object; an optical scanning means (2) that scans with a light beam having a light beam; and a light that is arranged on an optically conjugate plane with the light source of the optical scanning means (2) and that converts the signal light from the reflecting means (1) into an electrical signal. A moving object identification device comprising: a detection means (4); and a signal processing/identification means (5) for processing and identifying an output signal of the light detection means (4). (2) The mobile object identification device according to claim 1, wherein the reflecting means (1) comprises a plurality of corner cubes provided corresponding to the width of the bar code symbol. (3) A filter (3) is provided to remove background light other than the signal light from the reflected light from the reflecting means (1) and to provide the filter to the light detecting means (4). The mobile object identification device described. (4) The mobile object identification device according to claim 3, wherein the filter (3) is a spatial filter. (5) The light scanning means (2) modulates the light beam with a predetermined signal, and the light detection means (4) demodulates the modulated light beam. Mobile object identification device.