JPH0417364B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automobile distance measuring device that uses substantially two image sensors and measures distance by processing the image signals.

First, the principle of distance measurement according to the present invention will be explained with reference to FIG.
A and 1B form an image of the target 3 on image sensors 2A and 2B. here,
When approaching target 3, image sensor 2
Assuming that the images on A and 2B are shifted by A and B, respectively, from the image positions at infinity, the distance R from the target 3 to each optical system 1A and 1B is equal to the distance f from the optical system 1A and 1B to the image. optical system 1
Calculated from the optical axis distance L of A and 1B, R=
It is expressed as f・L/A+B.

The conventional rangefinder has a mirror 6A as shown in Figure 2.
By rotating the optical axis, the optical axis is moved, and the distance is measured by detecting each rotation in which the two left and right images formed by each optical system 1A, 1B overlap through the half mirror 6B. However, devices that move mirrors in this way tend to malfunction and deteriorate over time, making them unsuitable when used in environments with large vibrations, such as in automobiles.
In addition, in automobiles, it is necessary to measure distance in an extremely short period of time, so the left and right image sensors 2
Comparing the output signals from A and 2B in real time is fastest, but if you try to increase the resolution, the scale of the circuit will increase.

The present invention has been made in consideration of the above, and the distance is determined by electrically extracting the image signal using an image sensor and performing signal processing, thereby eliminating the need for moving parts. An object of the present invention is to provide a distance measuring device for a vehicle that can be mounted on a vehicle without any trouble, and can measure distance at high speed with high resolution and with a simple configuration.

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 3, images by optical systems 1A and 1B are respectively formed on image sensors 2A and 2B,
Electrical signals of the image corresponding to the shading of the image are outputted serially from each pixel in time. As the image sensors 2A and 2B, CCD type, MOS type, etc. are used. The serially outputted image signals are sent to A/D converters 7A and 7 via amplifiers 4A and 4B.
B is converted into a digital quantity. Two A/D converters may be provided in this way to perform A/D conversion on the left and right sides simultaneously, or only one A/D converter may be provided and A/D conversions may be performed serially on the left and right sides. The image signals of each pixel converted into digital quantities are sequentially stored in storage devices 9A and 9B. computer 1
1 is a storage device 9A, 9B for controlling the exposure time of the image sensors 2A, 2B by controlling the image sensor drive circuit 10 and for storing A/D converted signals.
It controls writing to and reading from. The signals stored in the storage devices 9A and 9B are read out one pixel at a time while shifting the readout time on the left and right sides according to instructions from the computer 11, and after being converted into analog quantities via the D/A converters 12A and 12B, they are read out on the left and right sides. It is added to an absolute value calculation circuit 14 and an integrator 15 that calculate the absolute value of the difference between signals. As a result, the sum of the absolute values of the differences between the signals of the left and right pixels is calculated. The result of the operation is sent to A/D converter 1.
6 into a digital quantity and read into the computer 11. Next, the same calculation as above is performed by shifting one more pixel. In this way, by increasing the number of pixels to be shifted until a certain appropriate number is reached, a large number of calculation results are read into the computer 11.

For example, if the number of pixels of the image sensors 2A and 2B is now 256, and if the pixel shift is set to zero, then the difference between the signals of 256 pixels on each side is calculated. Next, if you shift one pixel, you will get the difference between the signals of 255 pixels. Additionally, for example 100
When the pixels are shifted, the difference between the signals of 156 pixels is calculated. The number of calculation results at this time is 101,
All of these are read into the computer 11.

Furthermore, in the computer 11, for example, the calculation result is divided by the number of compared pixels, and correction is made to obtain the signal difference per pixel signal, and the pixel shift when the signal difference is the smallest among the 101 pieces of data is calculated. Search for. Then, the distance is calculated from the pixel shift at this time. The results are displayed numerically or graphically on the display device 17. Note that the sum of the absolute values of the differences between image signals can be calculated using the calculation circuit of the computer 11, but the amount of calculation is large and it takes time, and this is not suitable for use in automobiles.

Also, if the signal contrast is low or the target 3 is dark and the signal level is low,
Since there is almost no difference between the minimum value and the maximum value among the signal difference calculation results, the computer 11 displays this on the display device 17 as an error.

Thus, since the above device has no moving parts,
It is suitable for use in automobiles because it is less likely to cause failures due to vibrations, and can be processed at high speed with high resolution using a computer or the like.

FIG. 4 shows the case where the distance measuring device 13 described above is loaded on a car. The output of the vehicle speed sensor 18 is input to the computer 11, and the computer 11 calculates the distance to the target 3 and the rate of change of the distance, that is, the relative speed. calculate. When driving a car, the safe range of distance between the vehicle and the vehicle in front is determined by the speed of the car, the distance between the cars, and the relative speed. Therefore, the value of this safety area is calculated based on the inter-vehicle distance measured by the computer 11 of the distance measuring device 13 and the output of the vehicle speed sensor 18. If an obstacle is detected in a region other than the safe region, that is, in a dangerous region, the alarm device 19 is activated by a command from the computer 11 to give a warning to the driver. Furthermore, by operating the brake 20 and accelerator 21 in response to commands from the computer 11, the vehicle can be driven while maintaining a constant inter-vehicle distance.

As described above, since the automotive distance measuring device according to the present invention has no moving parts, it is unlikely to be damaged due to vibration even when loaded in a vehicle. In addition, since the image sensor electrically extracts the signal of the image of the object and calculates the distance to the object based on the sum of the absolute values of the differences between these signals, it has fewer errors and is highly accurate. Distance can be measured at high speed, with high resolution, and with a simple configuration.

In addition, since the analog signal of the image sensor is converted into a digital signal and stored, and the signals are compared using this stored signal, there is no need to take an image each time the comparison is made, and the signal is converted back to the analog signal when the comparison is made. Since comparison is performed, the calculation time is short and
Speeding up is possible by shortening the time for imaging and calculation.

[Brief explanation of drawings]

Fig. 1 is a diagram explaining the measurement principle of the device of the present invention, Fig. 2 is a block diagram of a conventional device, Fig. 3 is a block diagram of the device of the present invention, and Fig. 4 is a block diagram of the device of the present invention installed in a car. It is. 1A, 1B...Optical system, 2A, 2B...Image sensor, 9A, 9B...Storage device, 11...Computer, 13...Automotive distance measuring device, 1
4... Absolute value calculation circuit. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] 1 A pair of optical systems arranged in parallel with a predetermined distance between optical axes, a pair of image sensors arranged in parallel that each optical system forms an image of the object, and the output signal of each image sensor is digitalized. a storage means for converting into a signal and storing it; and an output signal of each image sensor stored in the storage means is inputted after being converted into an analog signal with shifted timing,
A distance measuring device for an automobile, comprising: a calculating means for calculating the sum of the absolute values of the differences; and a distance calculating means for determining and calculating the result of this calculation to calculate a distance to an object.