JP3072675B2 - Moving distance measuring device using spatial filter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a moving distance measuring apparatus using a spatial filter for measuring a moving distance of a moving object.

[0002]

2. Description of the Related Art A moving distance measuring apparatus using a phase orthogonal spatial filter (hereinafter, simply referred to as "spatial filter") shown in FIG. 1 operates as follows.

Light reflected from a road surface is detected by a camera 3 attached to the lower surface of a moving object (not shown) and comprising an optical lens 1 and a CCD (charge coupled device) line sensor 2, and is sampled at a predetermined period. The data is read by the read circuit 4 and A / D converted (5) to obtain a data signal Di corresponding to the brightness of the road surface. Here, the CCD line sensor 2
It has a field of view L (L = 1 pixel length × number of pixels n) composed of n pixels arranged along the moving direction of the moving object.

[0004] Each data (D1, D2,
.. Dn) and the cosine load function Ci (C1, C2, C3,... Cn) from the load function generation circuit 6 and the sine load function S
A spatial frequency component is extracted by a product-sum operation with i (S1, S2, S3,..., Sn), and the phase operation unit 7 calculates the spatial frequency component from the previous sampling product-sum operation value and the current sampling product-sum operation value in FIG. Is detected, a phase shift angle .DELTA..phi. Proportional to the shift distance, which is the phase difference between the vectors Z1 and Z2, is obtained, and the actual shift distance is calculated and measured according to the following equation. X (m) = (L (m) / f) × (1 / 2π) × Δφ L: field of view (m) (number of CCD pixels n × length of 1 pixel) f: spatial frequency (wave number in field of view L) ) Δφ: phase shift angle (rad)

[0005]

In such a moving distance measuring apparatus using a CCD camera as a line sensor camera, when the moving object is moving at a high speed, the C
Since the CD has an accumulation time, as shown in FIG.
While D accumulates the charge based on (a) of the road surface pattern (bright and dark pattern) with respect to the visual field of the line sensor 2,
The light / dark pattern moves from (a) to (b), and a signal corresponding to the light / dark pattern on the road surface cannot be completely stored, and the spatial frequency component to be extracted decreases. This is because the pattern of the field of view moves during the accumulation of electric charge (that is, the subject blurs). Therefore, in the spatial filter that integrates the time output of the CCD and extracts the spatial frequency component, the moving distance is equal to the spatial frequency. This is because as the wavelength approaches, the integrated output approaches zero. When the CCD line sensor is used as described above, if the moving speed is high, it is difficult to detect and measure the moving distance by the spatial filter, and there is a disadvantage that the accuracy is reduced.

The present invention has been made in view of the above points, and is intended to provide a moving distance measuring apparatus using a spatial filter with high accuracy, which can cope with high accuracy even when a moving object is moving at high speed. Things.

[0007]

In order to suppress a decrease in the detection output of the CCD line sensor 2 during high-speed movement, a shutter or the like is attached to the CCD line sensor camera 3, and an instantaneous (short time) )
Although it is conceivable to detect only these, it is not only expensive but also the number of mechanical elements increases. Therefore, in the present invention, the illumination of the road surface (moving surface) is made to blink in a strobe-like manner, so that the pattern input at the time of lighting is minimized with respect to the pattern input at the time of lighting. Is moved close to the wavelength of the spatial frequency, the integrated output does not become zero, and as a result, a decrease in the extracted spatial frequency component is suppressed.

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a spatial filter operation device in a moving distance measuring device using a spatial filter according to the present invention. Reference numeral 3 denotes an optical system (lens) 1 and a field of view L (field of view L = 1) composed of n pixels arranged along the movement direction.
This is a CCD line sensor camera composed of a CCD line sensor having a pixel length × the number of pixels n), and detects reflected light according to a light-dark pattern on a road surface. The detected reflected light signal is sampled at a predetermined cycle, read out by the readout circuit 4, A / D-converted by the A / D converter 5, and subjected to a data signal Di (D1, D2,...) Corresponding to the light / dark pattern of the road surface. Dn). Then, from the load function generating circuit 6, a spatial load function (C
i: a cosine load function, Si: a sine load function), and performs a product-sum operation of the space load function and the data signal Di. (FIG. 2). The phase difference angle Δφ between the previous detection vector Z1 at the previous sampling position of the moving object (not shown) and the current detection vector Z2 at the current sampling position is the phase movement angle in the phase space based on the distance the moving object has moved. is there. Therefore, the moving distance of the moving object can be obtained from the phase moving angle Δφ (rad).

The moving distance X (m) is as follows: X (m) = (L (m) / f) × (1 / 2π) × Δφ L: Field of view (m) (length of CCD pixel n × 1 pixel) f) Spatial frequency (wave number in visual field L) Δφ: phase shift angle (rad).

In such a moving distance measuring device, the moving speed of a moving object is slower than the charge accumulating time of the CCD line sensor 2, and the electric charge proportional to the detection output corresponding to the brightness of the road surface can be sufficiently accumulated. Can accurately measure the moving distance, but when moving at a higher speed than the accumulation time of the CCD line sensor, the CCD line sensor 2 changes the light-dark pattern of the road surface due to the movement within the accumulation time. As a result, the reflected light is detected, so that it is not possible to detect the light and dark pattern determined by the road surface position, so that it is impossible to accurately measure the moving distance. That is, as shown in FIG. 3, assuming that the spatial frequency component pattern of the light and dark pattern on the road surface has a waveform (a), if the moving speed of the moving object is slower than the accumulation time of the CCD,
The n pixels in the field of view (L) accumulate charges corresponding to the spatial frequency component pattern waveform (a), and after moving by the phase angle Δφ, accumulate charges corresponding to the spatial frequency component pattern waveform (b). The spatial frequency component pattern of the light and dark pattern on the road can be accurately extracted by the spatial filter operation device (FIG. 1)
If it is faster than the accumulation time, the n pixels in the field of view (L) are shifted from the spatial frequency component pattern waveform (a) within the accumulation time to the spatial frequency component pattern waveform (b) at a position that moves within the accumulation time. Since a charge corresponding to the changing spatial frequency component pattern waveform is accumulated, the spatial frequency component of the light and dark pattern determined by the road surface position cannot be accurately extracted by the spatial filter operation device (FIG. 1). The reason that the extraction of the spatial frequency component pattern when the moving speed is high cannot be performed accurately is as follows.
Since the illumination light source 8 is constant light, the spatial frequency component pattern waveform (b) moved during the CCD accumulation time has the same magnitude as the same waveform (a). If the spatial frequency component pattern moved during the accumulation time is reduced, the electric charge accumulated during the CCD accumulation time becomes
The waveform corresponds to the spatial frequency component waveform (a) determined by the road surface position, and the spatial frequency component is accurately extracted by the spatial filter operation device (FIG. 1).

In view of this, the present invention provides a lighting device for a road surface in a spatial filter operation device (FIG. 1) by blinking a strobe-like light source, that is, a light source having a lighting time shorter than the CCD accumulation time. The charge corresponding to the waveform (a) during the lighting time and the waveform (b) during the extinguishing time are accumulated. In this case, the detection output of the CCD is reduced because the CCD detects the reflected light in a short time. However, in order to suppress the detection output, measures such as increasing the luminous intensity of the light source may be taken.

[0013]

As described above, according to the present invention, the illumination light source for the road surface (moving surface) is stored in the CCD line sensor storage time.
Light source that has a shorter lighting time than
By blinking , even when the moving object moves at high speed, the spatial frequency component pattern of the light and dark pattern determined by the road surface position can be detected stably and accurately by the CCD line sensor. It can be measured accurately.

Further, the light source for illuminating the road surface (moving surface) is turned on only for a time necessary for detection even when the moving body moves at a low speed, so that power consumption can be reduced.

[Brief description of the drawings]

FIG. 1 is a spatial frequency calculation device of the present invention.

FIG. 2 is a vector diagram illustrating movement of a spatial frequency component vector.

FIG. 3 is a pattern waveform illustrating movement of a spatial frequency component pattern.

[Explanation of symbols]

 1: Optical lens 2: CCD line sensor 3: CCD camera 4: Readout circuit 5: A / D converter 6: Load function generation circuit 7: Phase calculation unit of spatial filter calculation device 8: Light source for road surface (moving surface) illumination

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01B 11/00-11/30

Claims (1)

(57) [Claims] A CCD line sensor attached to a lower surface of a moving object and arranged along a moving direction; and a light-dark pattern detection output of the moving surface detected by the CCD line sensor is sampled at a predetermined cycle. A readout circuit for reading, a space load function circuit for generating a space load function arranged within a phase angle corresponding to a field of view of the CCD line sensor, and a data value of a sampled light and dark pattern output output from the readout circuit And a product-sum operation circuit for performing a product-sum operation on the space load function value output from the space load function generation circuit; and detecting a spatial frequency component vector on a phase space by an output of the product-sum operation circuit. A phase calculation unit that calculates the phase difference between the two detection vectors from the detection vector by sampling and the detection vector by current sampling A spatial filter operation circuit comprising a moving distance calculation circuit for calculating a moving distance of the moving object from the phase difference, the lighting for a short time as compared with the CCD line sensor accumulation time
Lighting for one moving plane lighting which blinks a light source having time
Lighting device, and in the lighting time, on the road surface
The voltage corresponding to the spatial frequency component pattern waveform of the light and dark pattern
The load is stored in the CCD line sensor,
Is the spatial frequency moved during the accumulation time of the CCD line sensor.
CCD line sensor converts charge corresponding to component pattern waveform
Travel distance measuring apparatus using a spatial filter which is characterized in that so as to accumulate.