JPH0618440A - Image processing device - Google Patents

Abstract

PURPOSE:To provide an image processing device capable of reducing an input image noise without sacrificing the visual field of a sensor. CONSTITUTION:This image processing device is equipped with a sensor head section having a laser projector 12 for irradiating an object 30 with a laser slit beam, and a camera 11 for photographing the reflected light SF of a laser beam from the object 30, and an image processing section having a frame memory and performing an image data process while reading image signals sent from the camera 11 after the temporary storage thereof in the frame memory. In addition, the camera 11 receives the reflected light SF through an optical interference filter 11B, and this filter 11B is such type as having wavelength slightly dephased from the center wavelength of the laser slit beam S, as a transmission band center.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus for inputting laser reflected light from an object and sending out a video signal, and processing the data by inputting the video signal, particularly Regarding the sensor head.

[0002]

2. Description of the Related Art FIG. 4 shows an outline of an optical distance sensor module used as an external sensor for a mobile robot. This module is roughly divided into a sensor head section 10 and a controller / image processing section 20. 30 is an object. The sensor head unit 10 is a CCD as shown in FIG.
A camera 11, a laser slit projector 12 for projecting the laser slit light S, and a laser driver 13 are provided. The laser projector 12 is, for example, GaALAs, rated output 30.
It has a mW and an oscillation frequency of 830 nm, and a cylindrical lens is used to generate slit light. Also,
The CCD camera 11 uses, for example, a wide-angle lens with a focal length of 8.5 mm (each field of view is about 50 degrees), and the laser reflected light S
_In order to eliminate the influence of disturbance on _F , the optical filter 11A is attached to the lens. Image processing unit 2
0 has a built-in frame memory, takes in the video signal sent from the CCD camera 11 as image data, stores it in the frame memory once, then reads it out to calculate distance data, and writes the distance information in the shared memory. Perform data processing, repeat this series of data processing,
The latest distance data is constantly updated in the shared memory DPM.

In this optical distance sensor module, a CCD
Since the camera 11 is above the laser slit projector 12, the environment surrounding the person standing in the corridor (FIGS. 6 and 7)
For example, the floor surface can be considered as the plane of the laser slit light, and the height of one's eyes can be considered as the lens position of the CCD camera 11. The farther the distance from the camera is, the higher the floor surface is located in the field of view. On the contrary, the closer it is, the lower it is seen in the field of view, and conversely, the distance to the object in the depth direction can be measured depending on which height of the input image the reflected light looks like.

Further, the more the angle deviates from the frontal direction (direction of the optical axis of the camera), the more the image is seen toward the right end or the left end in the field of view. It is possible to measure the azimuth of how much the angle is in the direction, and from this azimuth and the distance in the depth direction, the point on the two-dimensional plane for a certain reflected light point is uniquely determined.

[0005]

In a normal environment, since the laser reflected light S _F is brighter than other light sources, the reflection point can be easily known by obtaining the point of maximum brightness of each line of the image. However, when the environment is bright, the background light may be brighter than the laser reflected light S _{F. In} such a case, in order to easily identify the laser reflected light S _F with respect to the background light. The optical filter 11A is used.

The optical filter 11A includes a visible light cut filter and an interference filter.
It was confirmed by experiments that a narrow band interference filter is effective for reducing background light noise.

FIGS. 8 and 9 show laser slit light S directed to a flat wall and reflected light S _F thereof taken through a visible light cut filter and an interference filter, respectively. FIGS. 8A and 8B show profiles of the input image and the laser reflected light position in the horizontal direction when a visible light cut filter that transmits infrared rays is used, and FIGS. Shows the profile in the horizontal direction of the input image and the laser reflected light position when an interference filter is used. The interference filter used here has a central wavelength of 830 nm with a wavelength bandwidth of 20 nm.
Is an interference filter.

From both figures, whichever filter is used,
Although the amount of the laser reflected light S _F detected at the peripheral portion is small, it is understood that the interference filter is particularly remarkable. That is, although it can be said that the interference filter has a greater noise removing effect than the visible light cut filter, there is a problem that the effective visual field of the sensor is narrowed.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an image processing apparatus capable of reducing noise in an input image without sacrificing the field of view of the sensor.

[0010]

In order to achieve the above object, the present invention provides, in claim 1, a laser projector for irradiating an object with laser slit light and a reflected light of the laser light reflected from the object. An image processing apparatus comprising: a sensor head unit including a camera for capturing an image; and an image processing unit having a frame memory for temporarily storing a video signal transmitted from the camera in the frame memory, and then reading the image signal to process image data. The camera receives the reflected light through an optical interference filter, and the optical interference filter is a filter having a wavelength slightly deviated from the central wavelength of the laser slit light as a center of a transmission band.

According to a second aspect of the present invention, the camera of the sensor head is disposed above the laser slit projector and is inclined downward, and the image processing section calculates the distance to the object based on the image data of the input image. And

[0012]

In the present invention, as the optical interference filter, a filter having a wavelength slightly deviated from the central wavelength of the laser slit light as the center of the transmission band is used. Therefore, although the amount of transmitted light in the central portion of the sensor visual field is reduced, The amount of transmitted light at both ends increases.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, the central wavelength of the laser slit light S oscillated by the laser projector 12 is, for example, 830 nm.
The center wavelength of the transmission band of the used interference filter 11B is 842.5 nm.

As a result of experiments, the inventors of the present invention have found that the reason why the light amount is greatly attenuated in the peripheral portion of the input image when the interference filter is used is that the incident angle θ _{i of the} light beam incident on the filter and the pass band characteristic of the filter. I knew that there was a relationship. Figure 1
0 indicates the result of this experiment, where the incident angle θ _i is 0
830nm for rays of 10 degrees, 20 degrees, 30 degrees
Shows the wavelength pass characteristics of the interference filter for use in this figure. From this figure, it can be seen that laser light having a wavelength of 830 nm can pass about 80% at an incident angle of 0 degrees and about 15% at an incident angle of 20 degrees. That is, as the incident angle θ _i increases, the amount of light passing through the interference filter sharply decreases. It is understood that the narrow field of view in FIG. 8 is caused mainly by the slit light source and the shading of the camera, but is mainly caused by the directional characteristics of the interference filter.

From the above, the present inventors have found that the interference filter does not originally have a low transmittance for obliquely incident light, but as shown in FIG. 9, the center of the transmission band is vertically incident. Since there is a shift from the case, the inventor has devised an interference filter in which the transmission region for obliquely incident laser light matches the wavelength of the laser light.

FIG. 2 shows the 842.5n in the above embodiment.
The wavelength characteristic of the interference filter 11B for m is 8
Laser light with a wavelength of 30 nm is 80 when the incident angle is 20 degrees.
% Of light, 60% at an incident angle of 10 degrees, and 10% at an incident angle of 0 degree. FIG. 3 shows laser reflected light when the 842.5 nm interference filter 11B is used in the same experimental environment as in FIGS. 3A shows the laser reflected light, and FIG. 3B shows the horizontal brightness profile of the laser reflected light position.

As is apparent from FIG. 3, by using an interference filter in which the wavelength of the laser is at the center of the band with respect to the incident angles at both ends of the viewing angle, the background angle can be maintained without sacrificing the viewing angle. Optical noise can be removed.

When the interference filter of the above embodiment is used,
Although the transmittance for vertically incident light is 10%, the reflected light that has passed through the filter is sufficiently bright at the vertically incident portion (the central portion in FIG. 2), and in the laser wavelength band, it is rather a laser slit light source. And the shading characteristics of the camera are compensated, and the directional characteristics of the entire system are flattened.

[0020]

As described above, according to the present invention, by shifting the center of the transmission band of the interference filter from the center wavelength of the laser slit light, the amount of transmitted light at the center of the sensor field of view is reduced, but at both ends of the sensor field of view. Because the amount of transmitted light of
Noise in the input image can be reduced without sacrificing the field of view of the sensor.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a main part of an embodiment of the present invention.

FIG. 2 is a light incident angle-light transmittance characteristic diagram of the interference filter used in the above embodiment.

FIG. 3A is a diagram showing an image of laser reflected light that has passed through the interference filter in the above embodiment.

FIG. 3B is a horizontal brightness profile of the laser reflected light that has passed through the interference filter.

FIG. 4 is a block diagram of a conventional optical distance sensor module.

FIG. 5 is a block diagram of a sensor head unit in the optical distance sensor module.

FIG. 6 is a diagram for explaining the principle of the optical distance sensor module.

FIG. 7 is a view of FIG. 6 seen from above.

FIG. 8A is a diagram showing an image of laser reflected light that has passed through a visible light cut filter.

FIG. 8B is a horizontal brightness profile of the laser reflected light that has passed through the visible light cut filter.

FIG. 9A is a diagram showing an image of laser reflected light that has passed through a conventional interference filter.

FIG. 9B is a horizontal brightness profile of the laser reflected light that has passed through the conventional interference filter.

FIG. 10 is a light incident angle-light transmittance characteristic diagram of the conventional interference filter.

[Explanation of symbols]

10 Sensor Head Section 11 CCD Camera 11B Interference Filter 12 Laser Projector 13 Laser Driver 20 Image Processing Section 30 Object S Laser Slit Light S _F Laser Reflected Light

Claims (2)

[Claims] 1. A camera head having a frame head and a sensor head unit including a laser projector for irradiating an object with laser slit light and a camera for capturing reflected light of the laser light reflected from the object. In an image processing apparatus including an image processing unit that temporarily stores a video signal transmitted by the frame memory and then reads the image signal and processes the image data, the camera receives the reflected light through an optical interference filter, and the optical interference filter, An image processing apparatus comprising a filter having a wavelength slightly deviated from a center wavelength of the laser slit light as a center of a transmission band. 2. The camera of the sensor head is arranged above the laser projector so as to be inclined downward, and the image processing section calculates the distance to the object based on the image data of the input image. The image processing apparatus according to claim 1.