JP3559638B2 - Distance measuring device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a distance measuring device used in a camera or the like for optically measuring a distance to a distance measurement target.
[0002]
[Prior art]
Conventional distance measuring devices include an active method in which spot projection is performed on a distance measurement target and a passive method in which spot projection is not performed. In recent years, some cameras and the like have a hybrid type distance measuring device that combines an active type and a passive type and uses them as needed. An apparatus using a skim CCD sensor as such a hybrid-type distance measuring apparatus has been proposed by the present applicant in Japanese Patent Application No. 7-263183.
[0003]
Next, a part of the distance measuring apparatus based on the hybrid system proposed above will be described with reference to FIGS.
In FIG. 6, reference numeral 1 denotes a distance measurement target, 2 denotes an IRED as a light emitting element for performing spot projection, 3 denotes a light projection lens which projects light from the IRED 2 to the distance measurement target 1, and 4 and 5 denote distance measurement targets 1. The light receiving lenses 6 and 7 are first and second sensor arrays for receiving the reflected light passing through the light receiving lenses 4 and 5, respectively. Although not shown, the first and second sensor arrays 6 and 7 each have a charge accumulating section for temporarily accumulating the electric charges of the sensor arrays 6 and 7, a charge transfer section such as a CCD, and a charge rejection section for performing a skim operation. The sensor arrays 6 and 7 together with these components constitute a skim CCD sensor.
[0004]
FIG. 7 is a flowchart showing the operation in the case of performing the active distance measurement by the distance measuring apparatus having the above configuration.
First, in step S701, the IRED 2 is turned on and off to perform spot projection. Next, in step S702, a difference output between the light receiving signals of the skim CCD sensors when the light is turned on and when the light is turned off is obtained. In step S703, each charge of the sensor arrays 6 and 7 is integrated by adding while circulating in synchronization with turning on and off of the light projection, and the integration is performed to eliminate external light components other than the light projection component while performing this integration. Perform the operation.
[0005]
Next, the signal output is monitored, and when each differential output exceeds a certain amount, light emission is stopped in step S704. Then, in step S705, a correlation calculation of the spot projection signal is performed from the difference output. That is, the distance to the object to be measured is determined by the principle of triangulation based on the relative value of the position of each difference output on the two sensor arrays.
[0006]
FIG. 8 is a flowchart showing an operation when passive distance measurement is performed by the distance measurement device of FIG.
First, in step S801, the IRED 2 is turned off to enter a normal output mode for outputting a light receiving signal, and then in step S802, charge rejection (skim operation) is prohibited. Next, in step S803, a light receiving signal corresponding to the time of one light emission is obtained from each of the sensor arrays 6 and 7. Next, in step S804, correlation calculation of the light receiving signal obtained in step S803 is performed. That is, the distance to the object to be measured is determined based on the principle of triangulation based on the correlation value of the positions of the light receiving signals from the two sensor arrays on these sensor arrays.
[0007]
FIG. 9 is a flowchart for explaining the distance measuring operation in the hybrid distance measuring apparatus using the skim CCD sensor.
First, when distance measurement starts, it is determined in step S901 whether skimming is possible. If skim is possible, the process proceeds to step S902. On the other hand, if skimming is not possible, the process proceeds to step S904.
Next, in step S902, active distance measurement using projection ON / OFF is performed. The operation of the active distance measurement is as shown in FIG. In step S903, it is determined whether or not the distance measurement value has been obtained in step S902. If the spotlight signal cannot be obtained because the object to be measured is at a long distance or the reflectance of the object to be measured is low, the distance measurement is disabled and the process proceeds to step S704. If the distance measurement is possible, the distance measurement ends. Next, in step S904, spot projection is prohibited, and passive distance measurement is performed. The passive distance measurement operation is as shown in FIG. Here, after the distance measurement value is obtained, the distance measurement operation ends.
[0008]
By the way, in general, the passive ranging method can obtain a good ranging result without erroneous ranging when measuring a distant view through a window glass with a camera or the like, whereas the active ranging method does not always have a good ranging result. Distance results are not always obtained. This is because in the active distance measurement method, the distance is measured by receiving the reflected light of the projected light.When measuring a distant view through the window glass, the reflected light of the slight projection light reflected on the window glass is measured. This is because the distance result is adversely affected.
In response to the adverse effects of the active distance measurement method, the present applicant detects the reflected light on the window glass surface using a dedicated light receiving sensor, so that the distance can be appropriately measured even when measuring a distant view through the window glass. We propose a technique to get the result.
[0009]
[Problems to be solved by the invention]
However, in the above technique, since light is received by a dedicated sensor, a dedicated sensor is required in addition to a sensor for normal distance measurement. Further, for example, when the distance between the window glass and the distance measuring device is slightly apart (for example, about 0.4 m), there is almost no reflected light due to light projection between the window glass and the camera body (or the distance measuring device). The reflected light is not received by the dedicated sensor, so that not only the window glass cannot be detected correctly, but also the distance of the window glass is measured by the regular reflected light from the window glass. If the result of the distance measurement (for example, 0.4 m) is out of the shooting interlocking range (for example, close to) of the camera, a normal camera displays a close warning or prohibits shooting. For this reason, it becomes impossible to take a distant view photograph through the window glass, and it becomes very difficult to handle.
Furthermore, in the above-described techniques, since the distance measurement result (or photographing lens) is merely set to a predetermined distance suitable for distant view shooting, there is a problem that the distance measurement result cannot be said to be accurate. Was.
[0010]
SUMMARY OF THE INVENTION It is an object of the present invention to provide a distance measuring device capable of performing high-accuracy distance measurement without using a dedicated sensor when measuring distance through a window glass.
[0011]
[Means for Solving the Problems]
A distance measuring device according to the present invention includes: a light projecting unit for projecting a spot on a distance measuring object; a first light receiving unit and a second light receiving unit; and a light receiving unit for receiving reflected light of the distance measuring object; First calculating means for calculating a distance to the object to be measured based on an output signal of the light receiving means by the spot light of the light emitting means, and a distance calculated by the first calculating means and a predetermined distance And a first comparing unit that compares the calculated distance with the first comparing unit when the calculated distance is smaller than the predetermined distance. A second comparing means for comparing the amount of received light with a predetermined amount of light; and a second comparing means for comparing the amount of received light with the second amount of light when the amount of received light is smaller than the predetermined amount of light. Based on the output signal obtained at a given time from the light receiving means It is provided second calculating means for calculating a distance to the distance measuring object again.
[0013]
[Action]
According to the present invention, when the distance measured by the active distance measurement is smaller than the predetermined distance and the received light amount at that time is smaller than the predetermined amount, it is determined that the distance measurement is through the window glass, and the mode is switched to the passive distance measurement. To perform highly accurate ranging.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
First, before describing embodiments of the present invention, the present invention will be described in principle. For example, when trying to measure the distance of a distant view over a window glass at a distance of 0.4 m by an active distance measuring device, even if the distance of the window glass is erroneously measured by the light reflected by the projection glass, The reflected light is a fairly weak light unless it is specularly reflected from the window glass surface. Further, for example, when the distance of a normal object to be measured at a distance of 0.4 m is measured, the reflected light from the projection light reflected on the object to be measured is a very strong light amount.
[0016]
Focusing on these, in the present invention,
(1) When the distance measurement result of the active distance measurement is shorter than a predetermined distance (for example, 0.6 m) and the amount of received light signal is smaller than a predetermined value, it is determined that a distant view through a window glass is measured. By setting the distance measurement result to a long distance (infinity), an appropriate distance measurement result can be obtained even in a distant view through a window glass.
(2) In a hybrid ranging apparatus capable of performing ranging by both the active ranging scheme and the passive ranging scheme, the ranging result of the active ranging is shorter than a predetermined distance (for example, 0.6 m), and a light receiving signal is obtained. When the amount is smaller than the predetermined value, it is assumed that the distance is measured over the window glass, and the distance measurement result of the passive distance measurement is adopted so that the distance can be accurately measured over the window glass. ing.
[0017]
FIG. 1 is a block diagram showing a first embodiment of a distance measuring apparatus according to the present invention based on the above principle.
In FIG. 1, 1 to 7 correspond to the same reference numerals in FIG. Reference numeral 8 denotes a CPU that controls the entire system and performs calculations for distance measurement. Reference numeral 9 denotes a light receiving signal processing unit including a charge storage unit, a charge transfer unit, a charge rejection unit, and the like described above with reference to FIG.
[0018]
Reference numeral 10 denotes a signal amount determination unit that determines whether the light reception signal amount is larger or smaller than a predetermined amount, and 11 denotes an IRED drive unit that drives the IRED 2 on and off. Reference numeral 12 denotes a window glass, which is located at a position slightly distant from the distance measuring device (for example, 0.4 m). The object to be measured is not illustrated because it is present at a considerable distance from the distance measuring apparatus. At this time, most of the light projected from the IRED 2 passes through the window glass 12, but part of the light is reflected by the window glass and received by the sensor arrays 6 and 7.
[0019]
FIG. 2 is a flowchart showing a distance measuring method of the distance measuring device according to the above (1).
First, when distance measurement starts, it is determined in step S101 whether skim is possible. If skim is possible, the process proceeds to step S102. If skimming is impossible, the process proceeds to step S108.
Next, in step S102, active distance measurement using light emission on / off is performed. The operation of the active distance measurement is as shown in FIG. In step S103, it is determined whether or not the distance measurement value has been obtained in step S102. If the spotlight signal cannot be obtained because the object to be measured is at a long distance or the reflectance of the object to be measured is low, it is determined that the distance cannot be measured, and the process proceeds to step S108. If the distance measurement is possible, it is determined in step S104 whether the distance measurement result is farther or shorter than a predetermined distance (for example, 0.6 m). If the distance measurement result is shorter than the predetermined distance, the process proceeds to step S105. If the distance measurement result is farther, the process proceeds to step S107. .
[0020]
In step S105, it is determined from the output of the signal amount determination unit 10 whether the number of light reception signals of the signal is larger or smaller than a predetermined amount. If the received light signal amount is larger than the predetermined value, the process proceeds to step S107, and the distance measurement result (AFDT) is terminated as the result of the active distance measurement obtained in step S102. If the received light signal amount is smaller than the predetermined value, the process proceeds to step S106, assuming that the distance is measured by the reflected light from the window glass, the distance measurement result (AFDT) is set to a long distance (infinity), and the distance measurement operation ends. .
[0021]
In step S108, since active distance measurement is impossible or impossible, spot distance projection is prohibited and passive distance measurement is performed. The passive distance measuring operation is as shown in FIG. Thereafter, in step S109, the distance measurement operation (AFDT) is completed as a result of the passive distance measurement obtained in step S108, and the distance measurement operation ends.
[0022]
Here, if the distance is measured by the reflected light from the window glass in the situation as shown in FIG. 1, the distance measurement result in step S102 is 0.4 m, the distance can be measured in step S103, and the process proceeds to step S104. Since the distance is shorter than 6 m, the process proceeds to step S105. Further, since the signal light reflected from the window glass is small, the process proceeds to step S106, and the distance measurement result (AFDT) is set to a long distance (infinity) which is an appropriate distance in this situation.
If the object to be measured at a distance of 0.4 m is measured, the amount of received signal light is very large (strong). Therefore, the process proceeds to step S107 in step S105, so that a correct distance measurement result is obtained. Can be.
[0023]
FIG. 3 is a flowchart illustrating the operation of the distance measuring method (2).
First, when distance measurement starts, it is determined in step S201 whether skim is possible. If skim is possible, the process proceeds to step S202. On the other hand, if skimming is not possible, the flow advances to step S206 to perform passive distance measurement. Next, in step S202, active distance measurement using light emission on / off is performed. The operation of the active distance measurement is as shown in FIG. In step S203, it is determined whether or not the distance measurement value has been obtained in step S202. If the spot light signal cannot be obtained because the object to be measured is at a long distance or the reflectivity of the object to be measured is low, it is determined that the distance cannot be measured, and the process proceeds to step S206 to perform passive distance measurement. I do. If the distance measurement is possible, it is determined in step S204 whether the distance measurement result is farther or shorter than a predetermined distance (for example, 0.6 m). If the distance measurement result is shorter than the predetermined distance, the process proceeds to step S205. If the distance measurement result is farther, the process proceeds to step S208. The distance measurement result (AFDT) is terminated as an active distance measurement result obtained in step S202.
[0024]
In step S205, it is determined from the output of the signal amount determination unit 10 whether the number of received light signals is larger or smaller than a predetermined amount. Here, if the light receiving signal amount is larger than the predetermined value, the process proceeds to step S208, and the distance measurement operation is ended by using the distance measurement result (AFDT) as a result of the active distance measurement obtained in step S202. If the received light signal amount is smaller than the predetermined value, the process proceeds to step S206, and a passive distance measurement is performed assuming that the distance is measured by the reflected light from the window glass.
In step S206, since active distance measurement is impossible, impossible, or distance measurement through a window glass, spot distance projection is prohibited and passive distance measurement is performed. The passive distance measurement operation is as shown in FIG. Thereafter, in step S207, the distance measurement operation (AFDT) is completed as a result of the passive distance measurement obtained in step S206, and the distance measurement operation ends.
[0025]
Here, assuming that the distance is measured by the reflected light from the window glass in the situation as shown in FIG. 1, the distance measurement result in step S202 is 0.4 m, the distance can be measured in step S203, and the process proceeds to step S204. Since the distance is shorter than 6 m, the process proceeds to step S205. Further, since the amount of signal light reflected from the window glass is small, the process proceeds to step S206, and passive distance measurement that is strong in distance measurement through the window glass is performed. For this reason, it is possible to perform shooting through glass with higher precision than in the first method.
[0026]
In this embodiment, a hybrid type distance measuring device using a skim CCD sensor is used. However, the present invention is not limited to this type of distance measuring device. The same control may be performed by using a hybrid type distance measuring device having a distance measuring device independently.
[0027]
FIG. 4 shows an active distance measuring apparatus according to a second embodiment of the present invention.
4, a CPU 8, an IRED driving unit 11, an IRED 2, a light projecting lens 3, a window glass 12, a signal amount determining unit 10, and a light receiving lens 4 are provided as in FIG. 1, and a PSD (semiconductor position) as a light receiving sensor is provided. (Detection element) 13 is provided. The output of the PSD 13 is input to the distance calculator 14.
[0028]
The distance calculation unit 14 includes an I / V converter, an amplifier, a known double integration circuit, and the like, and also includes a charge accumulation unit, a charge transfer unit, and a charge rejection unit, and measures a distance from a signal current photoelectrically converted by the PSD 13. The distance to the target is calculated.
[0029]
The object to be measured is not illustrated because it is present at a considerable distance from the distance measuring apparatus. At this time, most of the light projected from the IRED 2 passes through the window glass 12, but part of the light is reflected by the window glass 12 and received by the PSD 13.
[0030]
FIG. 5 is a flowchart illustrating the operation of the distance measuring apparatus.
First, when distance measurement starts, in step S301, the IRED 2 is caused to emit light and the spot light is projected toward the distance measurement target, and active distance measurement is performed by a known double integration operation. In step S302, it is determined whether or not the distance measurement value has been obtained in step S301. If the spot light signal cannot be obtained because the object to be measured is at a long distance or the reflectivity of the object to be measured is low, it is determined that the distance cannot be measured and the process proceeds to step S307, and the distance measurement result (AFDT) ) Is set to long distance (infinity). If the distance measurement is possible, it is determined in step S303 whether the distance measurement result is farther or closer than a predetermined distance (for example, 0.6 m). If the distance measurement result is shorter than the predetermined distance, the process proceeds to step S304. If the distance measurement result is farther, the process proceeds to step S306.
[0031]
In step S304, it is determined from the output of the signal amount determination unit 10 whether the number of light reception signals of the signal light is larger or smaller than a predetermined amount. Here, if the amount of received light signal is larger than the predetermined value, the process proceeds to step S306, and the distance measurement operation is ended by using the distance measurement result (AFDT) as a result of the active distance measurement obtained in step S301. If the received light signal amount is smaller than the predetermined value, the process proceeds to step S305, assuming that the distance is measured by the reflected light from the window glass, the distance measurement result (AFDT) is set to a long distance (infinity), and the distance measurement operation ends. .
[0032]
Although the distance measurement result (AFDT) is set to infinity in both step S305 and step S307, this distance may be the same distance, or may be a different long-distance value.
When YES is determined in step S302 and small is determined in step S304, passive distance measurement may be performed to obtain a more accurate AFDT.
[0033]
【The invention's effect】
As described above, according to the present invention, in hybrid ranging in which distance measurement can be performed by both the active distance measurement method and the passive distance measurement method, the distance measurement result of the active distance measurement is shorter than a predetermined distance, and When the amount of received light signal is less than the predetermined value, it is assumed that the distance is measured through the window glass, and the result of passive distance measurement can be obtained even with distance measurement through the window glass. By using, it is possible to accurately measure a distant view through a window glass.
Further, according to the present invention, a dedicated sensor for receiving reflected light from the window glass is not required.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing a first embodiment of the present invention.
FIG. 2 is a flowchart illustrating a first distance measuring method.
FIG. 3 is a flowchart showing a second distance measuring method.
FIG. 4 is a configuration diagram showing a second embodiment of the present invention.
FIG. 5 is a flowchart illustrating a distance measuring method.
FIG. 6 is a configuration diagram showing a conventional distance measuring device.
FIG. 7 is a flowchart showing a conventional active distance measuring operation.
FIG. 8 is a flowchart illustrating a passive ranging operation.
FIG. 9 is a flowchart illustrating an operation when performing active distance measurement and passive distance measurement.
[Explanation of symbols]
1 Target object 2 Light emitting element (IRED)
6 First sensor array 7 Second sensor array 8 CPU
9 Light reception signal processing unit 10 Signal amount judgment unit 13 PSD
14 Distance calculator

Claims (2)

A light projecting means for projecting a spot on a distance measuring object,
A light receiving means comprising a first light receiving means and a second light receiving means, for receiving the reflected light of the distance measuring object;
First calculating means for calculating a distance to the object to be measured based on an output signal of the light receiving means by the spot light of the light emitting means;
First comparing means for comparing the distance calculated by the first calculating means with a predetermined distance;
A second comparing step of comparing a light receiving amount of the light receiving unit by the spot light projection of the light projecting unit with a predetermined light amount according to a comparison result of the first comparing unit when the calculated distance is smaller than the predetermined distance. Means of comparison,
According to the comparison result of the second comparing means when the light receiving amount is smaller than the predetermined light amount, the distance measurement is performed based on an output signal obtained at a predetermined time from the light receiving means with the light emitting means turned off. A distance calculating device comprising: a second calculating means for calculating the distance to the object again. 2. The distance measuring apparatus according to claim 1, wherein said first and second light receiving means are skim CCD sensors.

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