JPS6316688B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a distance measuring device using an image sensor. A triangulation distance meter has been known for a long time as a device for measuring the distance to a target, and it has a configuration as shown in FIG. In the figure, 1 and 2 are lenses, 3 is a reflecting mirror provided corresponding to lens 2 and set to be rotatable, 4 is a translucent mirror provided corresponding to lens 1, and 5 is a reflecting mirror provided corresponding to lens 1. It is a target.

In the above configuration, one of the images obtained through the lenses 1 and 2 is reflected by the reflecting mirror 3, and the reflecting mirror 3 is adjusted so that the reflected image at that time coincides with the other image seen through the translucent mirror 4. The object 5 is rotated, and the distance to the target object 5 is determined from the rotation angle at that time.

By the way, if you want to measure a distance and use that distance to control various electromechanical devices, it is necessary to convert the distance into an electrical signal and output it. To achieve this, a MOS (metal oxide semiconductor) is used in the part that focuses the image.
It is sufficient to provide a CCD (charge-coupled device) type image sensor and electrically process the output from this image sensor.

However, if we try to apply it to an automobile inter-vehicle distance measuring device, for example, the reflector 3 shown in FIG.
A configuration having a movable part like this is disadvantageous in terms of vibration resistance and unfavorable in terms of reliability. Therefore, as shown in FIG. 2's science system 22
Correspondingly, it is conceivable to use separate image sensors 6 and 7 and to electrically process the shift between the left and right images in the signal processing circuit 8 to determine the distance to the target object 5. However, because automobile inter-vehicle distance measuring devices are used in environments with a very wide range of brightness, from nighttime brightness illuminated by headlights to midday brightness in summer, the image sensors 6 and 7 This range cannot be covered simply by changing the charge accumulation time. Furthermore, there is a limit to how short the storage time can be shortened in terms of the scanning speed of the image sensor, and even if it could be shortened, it would be difficult to shorten the image processing time. Furthermore, if the accumulation time is too long, the S/N ratio will deteriorate and the accuracy will deteriorate.

This invention was made in view of the above circumstances,
The amount of light reaching the image sensor is adjusted using a photosensitive filter whose transmittance changes depending on the intensity of incident light, and the average value or peak value of the output signal from the image sensor is adjusted. By controlling the accumulation time while comparing the value with a set value, we provide a distance measuring device that not only has vibration resistance but also can measure the distance to a target with high precision without being affected by changes in external light. It is intended to.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 3 shows an example of a distance measuring device according to the present invention, and the same parts as in FIGS. 1 and 2 are given the same reference numerals, and the explanation thereof will be omitted.

In the figure, reference numerals 9 and 10 denote photosensitive filters whose transmittance changes depending on the brightness of external light, and are disposed in front of each lens 1 and 2, respectively. 11,
12 is a detection circuit that detects the average value or peak value of the output signals of the image sensors 6 and 7, respectively;
Reference numerals 13 and 14 indicate drive circuits that compare the outputs from the detection circuits 11 and 12 with a set value to control the charge accumulation time in the image sensors 6 and 7, respectively.

Next, the operation of the above configuration will be explained.

The light from the target object 5 first passes through each photosensitive filter 9, 10, and then passes through the left and right lenses 1, 2, respectively.
to go into. Images are formed on image sensors 6 and 7 by these lenses 1 and 2, respectively. At this time,
When the outside world is bright, the light transmittance of the photosensitive filters 9 and 10 decreases due to ultraviolet rays in the outside light. In other words, for example, when the silver particles of the photosensitizer are precipitated by ultraviolet rays, the transmittance of the entire photosensitive filters 9 and 10 decreases, and conversely, when the external light becomes dark, the silver particles re-react and the transmittance increases. rises. Since the transmittance of the photosensitive filters 9 and 10 changes in accordance with the brightness of external light, the brightness of the images formed on the image sensors 6 and 7 is always kept almost constant, and therefore the electric charge The accumulation time can be set to an optimal value in terms of the S/N ratio and signal processing time.

By doing this, most of the range of brightness can be covered, but if the outside light is too bright or dark, the charge accumulation time can be changed as follows. That is, when the respective average values or peak values of the output signals from the image sensors 6, 7 are detected by the detection circuits 11, 12, the drive circuits 13, 14 compare the respective average values or peak values of the output signals from the image sensors 6, 7 with the set values. 7, the charge accumulation time is adjusted. For example, if the average value of the output signals from the image sensors 6, 7 is greater than a certain threshold value, this indicates that the image is too bright, so the drive circuits 13, 14 shorten the storage time. Conversely, if it is smaller than a certain threshold, it indicates that the image is too dark.
The drive circuits 13 and 1
4 applies a signal to the image sensors 6 and 7.

In this way, the obtained image sensor 6,
The output signal from 7 is processed by a signal processing device 8,
As a result, the distance to the target object 5 is calculated.

Note that the photosensitive filters 9 and 10 may be integrated into the corresponding lenses 1 and 2.

As described above, according to the present invention, by providing a control system for the storage time of the photosensitive filter and image sensor, there are no moving parts, excellent vibration resistance, and the brightness of the image is automatically adjusted. Since it is adjustable, it can be suitably used as a distance meter for automobiles, etc., where the environment changes rapidly in brightness and darkness.

[Brief explanation of the drawing]

Fig. 1 is a principle diagram of a distance meter using a conventional triangulation method, Fig. 2 is a schematic diagram of a distance measuring device using an image sensor, and Fig. 3 is an example of a distance measuring device according to the present invention. FIG. 5... Target object, 6, 7... Image sensor, 8
... Signal processing circuit, 9, 10 ... Photosensitive filter, 11, 12 ... Average value or peak value detection circuit, 13, 14 ... Drive circuit, 21, 22 ...
Optical system. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1 A pair of optical systems arranged based on the triangulation method, an image sensor provided corresponding to each optical system and combining the images of the target, and a difference in detection power signals from both image sensors. a signal processing circuit that calculates the distance from the image sensor to the target; a photosensitive filter that is placed on the optical path of each of the above systems and whose transmittance changes depending on the brightness of external light; and a signal processing circuit that calculates the distance from the image sensor to the target object. Distance measurement equipped with a detection circuit that detects the average value or peak value of each output signal, and a drive circuit that compares the output from each detection circuit with a set value and controls the charge accumulation time in the corresponding image sensor. Device.