JPH06201379A - Range finder - Google Patents

Abstract

PURPOSE:To divide an image signal for distance measurement into image signals by every time band, dissolve distance measurement when the correlation between the signals is judged low, and improve the reliability of distance measurement. CONSTITUTION:Image signals within a monitoring area taken by first and second video cameras and A/D converted 6, 7 are stored 8, 9 for one frame. A CPU 10A resolves the image signals to first and second field image signals and takes them, determines the difference in image signal every picture element of the fist and second field images within the monitoring area by a determined expression, and calculates the sum (comparative value (c)) of the differences. When the correlation between the field images is good, the value (c) is close to O. This comparative operation is conducted every frame image of each taken image, and when each image has a value (c) lower than a determined value, the image is judged effective, and the distance between cars to a preceding vehicle 5 is determined. When the second field image is influenced by a wiper brush, the image signal becomes O and the value (c) becomes the determined value or more. Thus, the correlation is low, the image is judged invalid, and the distance measurement is dissolved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distance measuring device,
In particular, the present invention relates to a distance measuring device for tracking a preceding vehicle while displaying an image and processing an image signal of the preceding vehicle to measure an inter-vehicle distance.

[0002]

2. Description of the Related Art FIG. 10 shows, for example, JP-A-59-19781.
It is a block diagram which shows the whole structure of the conventional distance measuring device using the image sensor disclosed by the 6th publication. In the figure, reference numerals 1 and 2 denote a pair of lenses which are symmetrically arranged with a distance of a base line length L, and an image sensor 3 or 4 which is located behind a focal distance f to form an image of a preceding vehicle 5 located ahead of the distance R. Image on. Reference numerals 6 and 7 are A / D for converting the sensor signals output from the image sensors 3 and 4 into digital signals.
The converters 8 and 9 are memories that store the digital signals output from the A / D converters 6 and 7 as image signals of the preceding vehicle 5. The memories 8 and 8A alternately store the image signals to store the image signal before the image currently displayed as an image in the memory 8A as the reference image signal.

Reference numeral 10 denotes a CPU, which processes the image signals read from the memories 8 and 9 to generate an image display signal, displays an image of an object in front of the vehicle including the preceding vehicle 5 on the display device 11, and The distance to the vehicle 5 is calculated.
Reference numeral 12 denotes a tracking window setting device, which sets the tracking window to the preceding vehicle 5 on the display screen by the window setting switch 13 which is operated when the preceding vehicle 5 as the distance measurement object is recognized on the screen of the display device 11. CPU to do
Give instructions to 10.

Next, the operation of the conventional distance measuring device will be described. First, the driver of the host vehicle, while looking at the screen of the display device 14, finds the preceding vehicle 5 as the distance measurement target on the screen and operates the window setting switch 13 to operate the window forming device 12. As a result, the CPU 10 generates a window image signal and sets the window for the preceding vehicle on the screen. Further, when setting the window, the CPU 10 measures the distance to the preceding vehicle 5.

As the distance measuring method, the CPU 10 reads the image signals a1 and b1 from the pixels arranged at the upper left ends of the image sensors 3 and 4 through the memories 8 and 9, respectively, and the absolute value c11 = the difference between the image signals. | A1-b
1 | Furthermore, 1 from the left end of the image sensors 3 and 4
The image signals a2 and b2 are read from the pixels arranged on the right side of the two, and the absolute value of the difference between the image signals is c12 = |
a2-b2 | This operation is performed for all pixels of the image sensors 11 and 12, and

When the sum s1 of absolute values is obtained as described above, the CPU 10 next reads the image signal a1 from the pixel arranged at the upper left end of the image sensor 3 from the memory 8 and the image sensor from the memory 9. The image signal b2 is read from the pixel arranged on the right side from the upper left end of 4, and the absolute value of the difference between the image signals c21 = | a1-b2
Ask for |. Further, the image signal a2 is read out from the pixel arranged one right from the upper left end of the image sensor 3, and the image signal b3 is read out from each pixel arranged two right from the upper left end of the image sensor 4, respectively. The absolute value of the difference c22 = | a2-b3 |
This operation is performed for each image sensor 3, 4.

As described above, the CPU 10 causes the pixels of the image sensors 3 and 4 to be n (n = 1.
2.3. ． ) The image signals are read while being shifted by one, and the sum of the absolute values of the differences between the image signals is obtained. Then, when the sum total level of the absolute values of the differences becomes the highest by such a pattern matching method, it is determined that the image signals in both image sensors are the most in agreement, and the lens 1 and 2 are moved together with the shift number n of the image sensor at that time. Baseline length L between,
Substituting the focal length f of the lenses 1 and 2 and the pitch width p between the pixels forming the image sensors 3 and 4 into the following equation (1), the distance from the lenses 1 and 2 to the preceding vehicle 5 by the principle of triangulation, that is, Find the inter-vehicle distance R.

R = (f * L) / (n * p) (1)

In the prior art, the window setting switch 13 is operated every time the preceding vehicle to be the distance measurement target is specified on the screen to set the window on the preceding vehicle on the screen. However, like the distance measuring device disclosed in Japanese Patent Laid-Open No. 2-232511, the window setting is continuously performed as long as the preceding vehicle having the window set once is within the visual field of the image pickup means such as the video camera. , There was a device that calculates the inter-vehicle distance based on the image of the preceding vehicle in Widow.

FIG. 11 is a block diagram showing the overall construction of another conventional distance measuring device. In the figure, the same parts as those in FIG. 10 indicate the same or corresponding parts. In the figure, 8
A is a memory that stores the image signal of the preceding vehicle for which the window is set as a reference image signal. The reference image signal of the memory 8A is updated to the preceding vehicle image stored in the memory 8 every predetermined time. The window setting method by the CPU 10 is as follows. First, the driver of the host vehicle searches for the preceding vehicle 5 to be tracked while looking at the display screen of the display device 14, and when setting a window for this preceding vehicle 5, the window setting switch 13 is operated to operate the window forming device 12. The CPU 10 is instructed to set the window through. The CPU 10 stores the image signal in which the window is set in the preceding vehicle image in the memory 8A as the reference image signal.

After that, when the CPU 10 fetches the image signal from the memory 8 or 9, the image signal is shifted from each of the memories 8 and 8A by the pattern matching method used in the distance measuring method and stored in the memory 8 by a known algorithm. The window is set to the image having the best correlation with the reference image signal stored in the memory 8A of the image signals. Then, the image in which the window is set is stored in the memory 8A as the reference image, and the reference image signal is updated.

As a method of measuring the inter-vehicle distance to the preceding vehicle for which the window is set, the image signal stored in the memory 9 is used as a reference image, and the pattern matching is performed while sequentially shifting the image signals of both memories 9 and 8A. Method 2
The two images are overlaid and the shift number n at that time is described in (1) above.
To obtain the distance to the preceding vehicle 5.

[0013]

Since the conventional distance measuring device performs tracking and distance measurement of the preceding vehicle based on the display image signal of the preceding vehicle picked up by a video camera mounted on the vehicle, If it vibrates violently or if a wiper brush or the like is in the field of view of the video camera, the correlation between the first field image and the second field image forming the display image is significantly impaired, and the reliability of tracking or distance measurement decreases. There was a problem.

The present invention has been made in order to solve the above problems, and the tracking operation or the distance measurement is performed according to the result without checking the correlation between the first field image and the second field image. An object of the present invention is to obtain a distance measuring device that can be used.

[0015]

According to a first aspect of the present invention, there is provided a distance measuring device according to the triangulation principle based on image signals of an object to be measured which are respectively output from a pair of image pickup means mounted on a vehicle. Distance measuring means for measuring the distance to the measurement object and image signals for each time zone of the measurement object outputted from at least one of the pair of image pickup means are compared, and between these image signals It is provided with signal processing means for canceling the distance measurement when it is determined that the correlation is low.

According to a second aspect of the present invention, there is provided a distance measuring device based on the image signals of the measuring object output from a pair of image pickup means mounted on the vehicle, and the distance to the measuring object is determined by the triangulation principle. The distance measuring means for measuring and the image signal for each time zone of the current image signal used for updating the reference image of the preset measurement object are compared, and it is determined that the correlation between these image signals is low. In this case, an image updating means for stopping the updating of the reference image by the current image signal is provided.

According to a third aspect of the present invention, in the distance measuring apparatus, the distance to the object to be measured is based on the triangulation principle based on the image signals of the object to be measured which are respectively output from the pair of image pickup means mounted on the vehicle. And the image signal for each time zone of the measurement object output from at least one of the pair of image pickup means is compared, and it is determined that the correlation between these image signals is low. Sometimes an effective image signal is obtained, an interpolated image signal is obtained based on this effective image signal,
This interpolation image signal is replaced with an invalid image signal, and an image signal generating means for generating an image signal of the measurement object having a high correlation is provided.

[0018]

In the distance measuring device according to the first aspect of the present invention, the distance measuring image signal is divided into image signals for each time zone, and if the correlation between these image signals is examined and it is determined that the correlation is low. However, some noise is mixed into the image signal for distance measurement, and this image signal is unreliable as the image signal for distance measurement, and the distance measurement is canceled.

The distance measuring device according to the invention of claim 2 is
If the current image signal used to update the preset reference image of the measurement object is divided into the image signal for each time period, and the correlation between these image signals is examined and it is determined that the correlation is low. For example, some noise is mixed in the current image and it is judged that the current image is not suitable for use as an image signal for updating the reference image, and the updating of the reference image is stopped.

The distance measuring device according to the invention of claim 3 is
The image signal for distance measurement is divided into image signals for each time zone, the correlation between these image signals is examined, and if it is determined that the correlation is low, the invalid image signal affected by noise is validated. Replace with an effective image signal based on the image signal,
An image for distance measurement having good correlation is generated and used for distance measurement.

[0021]

【Example】

Example 1. An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the overall configuration of the distance device according to this embodiment. In the figure, the same reference numerals as those in FIG. 10 indicate the same or corresponding parts. In the figure, 10A is a CPU in this embodiment, and in addition to the conventional function, 10A is an image signal for each time period in the image signals for one frame stored in the memories 8 and 9, that is, a first field image signal. Check the correlation of the second field image signal. The image sensor 1 and the lens 3 constitute an image pickup means, and the CPU 10A constitutes a distance measuring stage and a signal processing means.

Next, the operation of this embodiment will be described. In this operation description, the distance measurement (distance measurement) execution determination processing based on the correlation check between field image signals will be focused on and described. First, if the driver of the own vehicle recognizes the image of the preceding vehicle 5 to be tracked in the monitoring area 21 set on the display screen of the display device 11 as shown in FIG. 3, the tracking window 21 is set to the image. Window forming device 12
Through the CPU 10A. As a result, CPU 10
A stores the image signal of the image 20 in which the tracking window 21 is set in the memories 8 and 9.

However, if the wiper brush is applied in front of the video camera through the windshield of the vehicle,
As shown in FIG. 4, the wiper brush image 23 is applied to the window 22 in the image 20. As a result, a part of the preceding vehicle image is blocked by the wiper brush image 23, and the image 20 is stored in the memories 8 and 9 in that state. When the image 20 shown in FIG. 4 is used as an image for one frame and the image 20 is decomposed into a first field image and a second field image, as shown in FIG. 5, the first field image has a wiper brush image 23a. However, it is recognized that the wiper brush image 23b is included in the second field image.

Further, the image 20 shown in FIG. 5 is a first image shown in FIG.
When decomposed into a field image (b in the same figure) and a second field image (c in the same figure), the preceding vehicle image is shielded by the wiper brush image in different regions as compared with the normal image (a in the figure). . Next, FIG. 7 shows a part of the image for one frame shown in FIG. 5 in pixel units. Here, Ai, j to Ai + 1, j + 2 are pixel groups in the first field image, and Bi, j to Bi + 1,
j + 2 is a pixel group in the second field image. Then, when the image signals output from the pixel group in the second field image are digitally converted by the A / D converters 6 and 7,
The image signal becomes 0 due to the influence of the wiper brush.

The operation of this embodiment will be described below with reference to the flowchart of FIG. First, the lens 1 is used for the memories 8 and 9.
And a first video camera including the image sensor 3,
One frame of the image signal in the monitoring area 21 that has been captured and digitally converted by the lens 2 and the second video camera including the image sensor 4 is stored. C
The PU 10A decomposes the 1-frame image signal stored in the memories 8 and 9 into the first and second field image signals and takes them in (step S1). Then, the first field image signal and the second field image signal of the image in the monitoring area 21 are compared according to the equation (2) (step S2).

[0026]

As this comparison calculation process, that is, the pixels Ai, j to Ai + 1, j of the first field image shown in FIG.
+2 image signal and pixel Bi, j of the second field image
The difference between the image signals of Bi + 1 and j + 2 is obtained by the equation (2), and if the difference is obtained for each pixel, the sum of the differences, which is the comparison value c, is obtained. Here, if the correlation between the field images is good, the sum is close to zero.

When the above-mentioned comparison calculation processing is performed on one frame image picked up by each video camera and it is determined that the comparison value of each image is less than a predetermined value (step S3), both video cameras pick up the image. The image is determined to be valid, and the inter-vehicle distance to the preceding vehicle 5 is obtained by the triangulation principle using both image signals.

However, as shown in FIG. 7, when the second field image is affected by the wiper brush, the image signal of each pixel becomes 0. Therefore, these image signals are substituted into the equation (2) to obtain the first field image. When the sum of the differences from the image signal is obtained, the sum has a predetermined level. As a result, the correlation between the field images is determined to be low, the captured image becomes invalid, and the inter-vehicle distance measurement is not performed.

Example 2. In the first embodiment, the image signal for one frame obtained by imaging the preceding vehicle is divided into the first field image signal and the second field image signal, and the captured image signal is an image signal for distance measurement based on the correlation between these field image signals. It was judged as effective. However, it is also possible to determine whether the captured image signal is valid as the window update image signal based on the validity determination result. FIG. 2 is a block diagram showing the overall configuration of the distance measuring device according to the second embodiment. In the figure, the same reference numerals as those in FIG. 11 denote the same or corresponding parts. In the figure, 10B is a distance measuring means, an image updating means,
And a CPU constituting image signal generating means.

The operation of this embodiment will be described below with reference to the flowchart of FIG. As shown in FIG. 5, the CPU 10B reads the image signal of the reference image 20 from the memory 8, for example, and the reference image signal is read as in the first embodiment with the first field image signal (FIG. 6b) and the second field image signal (FIG. 6c). ), Each field image signal is compared on a pixel-by-pixel basis, and it is determined whether the comparison value is less than or equal to a predetermined value (step S11,
12). At this time, if the comparison value is equal to or less than the predetermined value, it is determined that the correlation between the field image signals is good as described in the first embodiment, and the reference image for window setting stored in the memory 8A is stored in the memory 8A. It is updated with the reference image stored in (step S13). The update process is as described in the related art.

However, if it is determined in step S12 that the correlation between the field image signals is low, the reference image stored in the memory 8 is regarded as a low reliability image for updating, and this time, the reference image is stored in the memory 8A. The stored standard image is not updated, and the reference image used for measuring the distance to the preceding vehicle 5 is also examined for correlation. In this case, using the image stored in the memory 9 as the reference image, the reference image signal is divided into the first field image signal and the second field image signal in the same manner as the standard image signal, and the respective field image signals are compared in pixel units for comparison. It is determined whether the value is less than or equal to a predetermined value (step S1
4, 15). At this time, if the comparison value is equal to or less than the predetermined value, it is determined that the correlation between the field image signals is good, and the conventional method is performed using the standard image stored in the memory 8 and the reference image stored in the memory 9. The inter-vehicle distance is measured with (step S16).

However, if it is determined in step S14 that the correlation between the field image signals is low, the reference image signal and each field image signal in the standard image signal stored in the memory 8 are compared to obtain a good correlation. An effective field image signal, that is, a first field image signal (corresponding to Ai, j to Ai + 1, j + 2) that is not affected by the wiper brush as shown in FIG. 7 is obtained.

Next, an invalid field image signal (Bi, j ...
In order to convert (corresponding to Bi + 1, j + 2) into an effective field image signal and obtain a reference image signal having good correlation, for example, the invalid pixel Bi, j is replaced with an effective pixel (step S14). As an example of the interpolation process, regarding the invalid pixel Bi, j, the image signal value is simply changed to the valid pixel Ai, j.
Alternatively, it may be replaced with an image signal of Ai + 1. Alternatively, the image signal value of the invalid pixel Bi, j is converted into the effective pixel Ai, j by using the averaging filter algorithm shown in the following equation (3).
And Ai + 1, j may be replaced by the average value of the image signals.

Bi, j = (Ai, j + Ai + 1, j) / 2 (3)

In this embodiment, each field image signal of the standard image signal is used in order to obtain the effective field image signal, but another memory 9A is added to the memory 9 for storing the reference image so that the standard image Similarly, the reference image may be stored alternately every predetermined time, the previous reference image and the current reference image may be compared, and a field image signal having a good correlation may be selected from the current reference images and subjected to interpolation processing. .

Further, in each of the embodiments, the window setting for the preceding vehicle is performed manually while looking at the display screen of the display device 14. However, as disclosed in JP-A-3-45898, the image signal is transmitted to the vehicle. A window may be set to the image signal corresponding to the vehicle when the vehicle is extracted by applying the extraction filter. Furthermore, IPSJ vol27 no. 7 19
As described in 86, when attention is paid to the left-right symmetry of the vehicle, if the captured image as a result of the image signal processing has left-right symmetry, the window may be set for the image.

[0038]

According to the invention of claim 1, the distance to the object to be measured is determined by the triangulation principle based on the image signals of the object to be measured which are respectively output from the pair of image pickup means mounted on the vehicle. The distance measuring means for measurement and the image signal of the measuring object output from at least one of the pair of image pickup means are divided into image signals for each time zone, and the correlation is obtained. Since the signal processing means for canceling the distance measurement when it is determined that is low is provided, there is an effect that the reliability of the distance measurement processing is improved.

According to a second aspect of the present invention, there is provided a distance measuring device based on the image signals of the object to be measured which are respectively output from a pair of image pickup means mounted on the vehicle, and the distance to the object to be measured according to the triangulation principle. And the current image signal used to update the reference image of the preset measurement object are compared separately with the image signal for each time zone, and the correlation between these image signals is Since the image update means for stopping the update of the reference image by the current image signal is provided when it is determined to be low, there is an effect that the reliability of the operation of specifying the measurement target is improved.

According to a third aspect of the present invention, the distance measuring device measures the distance to the measuring object based on the triangulation principle based on the image signals of the measuring object output from the pair of image pickup means mounted on the vehicle. The distance measuring means for measurement and the image signal of the measuring object output from at least one of the pair of image pickup means are compared with the image signal for each time zone, and the correlation between these image signals is obtained. Image signal of a distance measurement target having a high correlation is generated by replacing the interpolated image signal with an invalid image signal to obtain an effective image signal when it is determined that Since the image signal generating means is provided, the distance measuring function can be made more stable.

[Brief description of drawings]

FIG. 1 is a block diagram showing an overall configuration of a distance measuring device according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing an overall configuration of a distance measuring device according to a second embodiment of the present invention.

FIG. 3 is a diagram showing an image display example of a display device 14 in each of the embodiments.

FIG. 4 is a diagram showing an image display example when a display image is affected by a wind wiper.

FIG. 5 is a diagram showing a display image by combining a first field image and a second field image.

6 is a diagram showing the image 20 shown in FIG. 5 separately for a first field image (b) and a second field image (c).

FIG. 7 is a diagram showing a one-frame image signal for each pixel array.

FIG. 8 is a flowchart illustrating the operation of the first embodiment.

FIG. 9 is a flowchart illustrating the operation of the second embodiment.

FIG. 10 is a block diagram showing an overall configuration of a conventional distance measuring device.

FIG. 11 is a block diagram showing an overall configuration of another conventional distance measuring device.

[Explanation of symbols]

 1 and 2 lens 3 and 4 image sensor 5 preceding vehicle 8, 8A, 9 memory 10A, 10B CPU 14 display device 23 window

[Procedure amendment]

[Submission date] October 22, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Claims

[Correction method] Change

[Correction content]

[Claims]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0015

[Correction method] Change

[Correction content]

[0015]

According to a first aspect of the present invention, there is provided a distance measuring device according to the triangulation principle based on image signals of an object to be measured which are respectively output from a pair of image pickup means mounted on a vehicle. The distance measuring means for measuring the distance to the object to be measured and the image signal for each field of the object to be measured output from at least one of the pair of imaging means are compared, and the correlation between these image signals is compared. It is provided with a signal processing means for canceling the distance measurement when it is determined that the property is low.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0016

[Correction method] Change

[Correction content]

According to a second aspect of the present invention, there is provided a distance measuring device based on the image signals of the measuring object output from a pair of image pickup means mounted on the vehicle, and the distance to the measuring object is determined by the triangulation principle. And the image signal for each field of the current image signal used for updating the reference image of the preset measurement object are compared, and it is determined that the correlation between these image signals is low. An image updating means for stopping the updating of the reference image by the current image signal is provided.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0017

[Correction method] Change

[Correction content]

According to a third aspect of the present invention, in the distance measuring apparatus, the distance to the object to be measured is based on the triangulation principle based on the image signals of the object to be measured which are respectively output from the pair of image pickup means mounted on the vehicle. The distance measuring means for measuring the image and one of the pair of image pickup means are used as a reference camera.
The reference image storage means for storing the image and the reference image after a predetermined time.
Compare the image of the camera and the image signal of each field,
When it is determined that the correlation between image signals is low, the reference image
The field image of the image in the image storage means and the image after the predetermined time.
Obtaining the correlation between each field image signal,
Image signal generation that regards the higher field image as valid , obtains an interpolated image signal based on this valid image signal, replaces this interpolated image signal with an invalid image signal, and generates a highly correlated image signal of the measurement object It is equipped with means.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0038

[Correction method] Change

[Correction content]

[0038]

According to the invention of claim 1, the distance to the object to be measured is determined by the triangulation principle based on the image signals of the object to be measured which are respectively output from the pair of image pickup means mounted on the vehicle. Distance measuring means to measure, the image signal of the measurement object output from at least one of the imaging means of the pair of imaging means is divided into image signals for each field and compared,
Since the signal processing means for canceling the distance measurement is provided when it is determined that the correlation between these image signals is low, the reliability of the distance measurement processing is improved.

[Procedure correction 6]

[Document name to be amended] Statement

[Correction target item name] 0039

[Correction method] Change

[Correction content]

According to a second aspect of the present invention, there is provided a distance measuring device based on the image signals of the object to be measured which are respectively output from a pair of image pickup means mounted on the vehicle, and the distance to the object to be measured according to the triangulation principle. And the current image signal used to update the reference image of the preset measurement object are compared separately with the image signal for each field, and the correlation between these image signals is low. Since the image updating means for stopping the updating of the reference image by the current image signal is provided when it is determined that the reliability of the operation of specifying the measuring object is improved.

[Procedure Amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0040

[Correction method] Change

[Correction content]

According to a third aspect of the present invention, the distance measuring device measures the distance to the measuring object based on the triangulation principle based on the image signals of the measuring object output from the pair of image pickup means mounted on the vehicle. The distance measuring means for measurement and the image pickup means of either one of the pair of image pickup means are used as the reference camera for the image.
And a reference image storage means for storing the reference image after a predetermined time.
Image of each field and the image signal of each field are compared and these images are
The reference image when it is determined that the correlation between the image signals is low
Field image of the image of the storage means and each after the predetermined time
The correlation between field image signals is calculated to obtain a higher correlation.
An image signal that determines which field image is valid , obtains an interpolated image signal based on this valid image signal, replaces this interpolated image signal with an invalid image signal, and generates a highly correlated image signal of the distance measurement object. Since it has a generation means,
This has the effect of making the distance measurement function more stable.

Claims (3)

[Claims] 1. A distance measuring means for measuring a distance to the object to be measured based on a triangulation principle based on image signals of the object to be measured respectively output from a pair of image pickup means mounted on a vehicle, and the pair. Signal processing for comparing the image signals of the measuring object output from at least one of the image pickup means for each time zone, and canceling the distance measurement when it is determined that the correlation between these image signals is low. A distance measuring device comprising means. 2. Distance measuring means for measuring the distance to the measurement object based on the triangulation principle based on the image signals of the measurement object output from a pair of image pickup means mounted on the vehicle, and preset. Compared image signals for each time zone of the current image signal used to update the reference image of the measured object, when the correlation between these image signals is determined to be low of the reference image by the current image signal A distance measuring device comprising image updating means for stopping updating. 3. A distance measuring means for measuring a distance to the object to be measured based on a triangulation principle based on image signals of the object to be measured respectively output from a pair of image pickup means mounted on a vehicle, and the pair. The image signals of the measurement object output from at least one of the image pickup means are compared for each time zone, and an effective image signal is obtained when it is determined that the correlation between these image signals is low. Distance measuring device including an image signal generating means for obtaining an interpolated image signal based on a simple image signal and replacing the interpolated image signal with an invalid image signal to generate an image signal of a measuring object having a high correlation. .