JP3083977B2 - Distance measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a camera distance measuring apparatus for automatically measuring a distance to a subject.

[0002]

2. Description of the Related Art As such a distance measuring device for a camera,
An active method of a triangulation type that has a distance measuring light source such as an LED and measures a distance to a subject in combination with a light receiving element is known.

Further, as another type of distance measuring device, there is no distance measuring light source, natural light reflected by a subject is received by two optical systems, and two optical images obtained by each optical system are obtained. There is known a triangulation-type passive method for measuring a distance to a subject based on the phase difference of the object.

[0004]

In a passive type distance measuring device, a substantially uniform distance measuring accuracy can be obtained from a short distance to a long distance to a subject. However, there is a disadvantage that distance measurement cannot be performed for a subject having uniform luminance.

On the other hand, in an active distance measuring device, there is a limit to the irradiation distance of the emitted light. If the distance to the subject is long, the reflected light cannot be obtained sufficiently, and the distance measurement may not be possible. Also, when trying to extend the irradiation distance of the emitted light,
A light emitting element having a large light amount is required, and accordingly, a large optical system for forming an image is required. In addition, when the reflectance of the subject is not uniform, or when only a part of the light emitted for distance measurement is applied to the subject, that is, when a so-called light beam is missing, the spot of the reflected light received by the light receiving unit is not sufficient. This caused the center of gravity to shift, causing erroneous ranging.

The present invention has been made to solve such a problem, and an object of the present invention is to provide a distance measuring apparatus capable of obtaining a more reliable distance measuring result.

[0007]

Accordingly, a distance measuring apparatus according to the present invention projects distance measuring light toward a subject and measures the distance to the subject based on the condensing position of the reflected light. Active type first distance measuring means, and passive light for receiving natural light reflected by a subject by two optical systems and measuring a distance to the subject based on two optical images obtained by the respective optical systems. A second distance measuring means, and a distance measuring value selecting means for selecting and outputting any one of the distance measuring results obtained from the first distance measuring means and the second distance measuring means. The distance measuring value selecting means comprises a first distance measuring means and a second distance measuring means.
When the difference between the distance measurement values and the distance measurement means is smaller than a predetermined allowable value, the distance measurement value of the first distance measurement means is selected, and when the difference is larger than the predetermined allowable value, the distance measurement value of the second distance measurement means is selected. And a first means for selecting

Further, the distance measuring apparatus according to claim 2 further comprises a luminance detecting means for detecting the luminance of the external world, and the distance measuring value selecting means further comprises an external luminance obtained by the luminance detecting means. Is provided with a second means for determining whether or not the value is within a predetermined intermediate level. When the second means determines that the external luminance is a value within the intermediate level, the first means performs the selection processing.

Further, in the distance measuring apparatus according to claim 3,
The distance measurement value selection means further includes third means for determining whether or not the distance measurement value obtained by the first distance measurement means is a value within a predetermined short distance. The second means determines that the external luminance is a value within the intermediate level, and
When the third means determines that the distance measurement value is within a predetermined short distance, the first means performs the selection processing. In this case, the first means selects the distance measurement value of the first distance measurement means when the difference between the distance measurement values of the first distance measurement means and the second distance measurement means is smaller than a predetermined allowable value. If the distance is large, the distance measurement value of the second distance measurement means is selected.

[0010]

Each distance measuring apparatus according to the present invention includes two types of distance measuring means, namely, an active type first distance measuring means and a passive type second distance measuring means, and performs distance measurement with both of them. .

In the distance measuring apparatus according to the first aspect, the first means compares the difference between the distance measurement values of the first distance measurement means and the second distance measurement means, and the difference value is larger than a predetermined allowable value. Is larger, it is determined that "light beam loss" in the active mode has occurred. In this case, the distance measurement value of the second distance measurement means using the passive method is selected. If the difference between the distance measurement values is small, the distance measurement value of the first distance measurement means using the active method is selected.

Further, in the distance measuring apparatus of the present invention, the second means determines that the external luminance is a value within a predetermined intermediate level. By this, at least the external luminance is not low luminance. It is determined whether or not the passive distance measurement can be normally performed. As a result, the comparison performed later by the first means becomes more reliable, and even when the distance measurement value of the second distance measurement means using the passive method is selected, the selected distance measurement value is not changed. Increases reliability.

Further, in the distance measuring apparatus according to the third aspect,
The third means determines whether or not the distance to the subject is a predetermined short distance based on the distance measurement result of the first distance measuring means. This is because in the active method of distance measurement, the distance measurement accuracy decreases as the distance to the subject increases, and when the distance measurement result by this method is farther than a predetermined distance, the first means uses this method. The selection of the distance measurement value is prevented. Therefore, only when it is determined that the distance to the subject is within the predetermined short distance, the distance measurement result of the active method can be selected by the first means.

[0014]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows a schematic configuration of a distance measuring apparatus according to the present embodiment. The distance measuring device includes an active distance measuring unit A that performs a triangulation type active distance measuring, and
Similarly, a passive distance measuring section P for performing a triangulation-type passive distance measurement is provided, and a luminance detecting section L for detecting external luminance and a distance measurement value selection circuit 40 are also provided.

The active distance measuring section A includes a light projecting section 11 composed of an LED or the like for projecting distance measuring light toward a subject, and a light receiving section 12 composed of a PSD or the like for receiving the reflected light. It has a distance measuring circuit 13 for calculating the distance to the subject based on the result of light projection and light reception (see FIG. 2).

The passive distance measuring section P includes a right light receiving section 21 and a left light receiving section 22 for receiving reflected light of natural light from a subject by two optical systems (see FIG. 2). (Optical position detecting device: not shown) for receiving two optical images obtained by the above-mentioned operation, and a distance measuring circuit 23 for calculating the distance to the subject based on the results.

The luminance detecting section L uses the configuration of the AE section (automatic exposure section) in FIG. 3, and is based on a light receiving section 31 composed of a light receiving element for exposure control, for example, CdS, etc. It is composed of a photometric calculation circuit 32 for calculating the external luminance.

The distance measurement value selection circuit 40 includes a luminance detection section L
Is a circuit that selects and outputs one of the distance measurement values measured by each of the distance measurement units A and P based on the external luminance obtained in step S1. FIG. 2 shows an external view of a camera provided with the distance measuring apparatus according to the present embodiment, and FIG. 3 shows an outline of an internal mechanism thereof. The distance measurement operation circuits 13 and 23, the photometry operation circuit 32, and the distance measurement value selection circuit 40 shown in FIG.
Configured in the PU.

Here, the operation of the distance measuring apparatus will be described with reference to FIG.

First, when the camera is pointed at the subject and a release switch (not shown) is turned on (# 100), the power supply voltage is read and the voltage value is checked (# 100).
102, # 104). Here, if the read voltage value is less than the threshold value ("NO" in # 104), the photographing process becomes impossible, so that the user is notified by a display, a warning sound, or the like. Shifts to a predetermined NG treatment (# 1
06).

If the read voltage value has cleared the threshold value ("Yes" in # 104), the luminance detecting section L performs photometric processing for detecting the external luminance (#).
108). In addition, the active ranging unit A performs the active ranging, and the passive ranging unit P performs the passive ranging (# 110, # 11).
2). Note that the distance measurement results in the respective distance measurement units A and P are given to the distance measurement value selection circuit 40 via the distance measurement calculation circuits 13 and 23.

Next, in the distance measurement value selection circuit 40, it is determined whether or not the external luminance obtained by the luminance detector L is a high luminance level equal to or higher than Lv14 (# 114). In the case where the external luminance is high, in the active method, the light receiving unit 12 cannot receive the reflected light of the distance measurement light satisfactorily, and the distance measurement accuracy may be reduced. On the other hand, in the passive method, since the amount of natural light reflected by the subject increases, the reliability of the distance measurement value is high. Therefore, when the external luminance obtained by the luminance detection unit L is equal to or higher than Lv14 (“No” in # 114), the distance measurement value selection circuit 40 selects the distance measurement value (passive data) of the passive distance measurement unit P. And output as distance measurement data (# 11
6). Then, for example, a photographing lens is set based on the set distance measurement data (# 118), the subsequent photographing processing is executed based on the distance measurement value output from the distance measurement value selection circuit 40. (# 120).

On the other hand, when the external luminance is lower than Lv14 ("NO" in # 114), it is further determined whether or not the external luminance is lower than Lv3 (# 122). In the case where the external luminance is low, the passive method has a small amount of reflected light of natural light and lacks reliability, but the active method has high reliability of the distance measurement value because the reflected light of the distance measurement light is well detected by the light receiving unit 12. For this reason, when the external luminance obtained by the luminance detecting unit L is equal to or lower than Lv3 (“No” in # 122),
The ranging value selection circuit 40 selects a ranging value of the active ranging unit A.

As described above, when it is decided to select the distance measurement value of the active distance measurement unit A as the distance measurement data,
Under the control of the PU, the distance measurement is further performed twice in the active distance measurement unit A (# 124, # 126), and the distance measurement values for the total three times including the distance measurement values in # 108 are averaged (# 124). # 128). This averaging increases the accuracy of the distance measurement value. The distance measurement in # 124 and # 126 may be performed three or more times, and the accuracy can be improved accordingly. The ranging value selection circuit 40 sets and outputs the ranging value (active data) obtained as described above as ranging data (# 13).
0).

When the external luminance is a high luminance level equal to or higher than Lv14 or a low luminance level equal to or lower than Lv3, the distance measurement value selection circuit 40 immediately selects one of the distance measurement values as described above. Select, but the brightness level is 3 <Lv
In the case of the intermediate luminance level of <14, the determination is further made based on the following values.

First, the distance measurement value selection circuit 40 determines whether or not the distance to the subject is shorter than 3 m as a result of the distance measurement by the active distance measurement unit A (# 132). Since the active method is a method of projecting distance measuring light toward a subject and receiving the reflected light, there is a limit to the distance of the distance measuring light.
If the distance to the subject is long, the reflected light cannot be obtained sufficiently, and the distance measurement accuracy may decrease or the distance measurement may not be possible. Therefore, when the distance measurement result of the active distance measurement unit A is 3 m or more, the distance measurement value selection circuit 40 (“N” in # 132)
o "), a distance measurement value (passive data) of the distance measurement value of the passive distance measurement unit P is selected and output as distance measurement data (# 11)
6).

On the other hand, if the distance to the subject is shorter than 3 m by the distance measurement by the active distance measurement unit A (# 13)
2 "Yes"), the distance measurement value selection circuit 40 calculates the distance measurement result a of the active distance measurement unit A and the distance measurement result p of the passive distance measurement unit P.
And the absolute value | ap | is compared with the allowable value D (# 134). This is a flow for judging whether or not the aforementioned “light beam loss” occurs.

In this case, the luminance level is an intermediate luminance level of 3 <Lv <14, and both types are in a state where the distance can be measured normally. However, in the distance measuring condition where the distance to the subject is less than 3 m, the active method is used. Since the result of the distance measurement is more reliable, I would like to select this distance measurement value. However, depending on the actual shooting situation, a situation may occur in which only a part of the light emitted from the light projecting unit 11 hits the subject, and the projected beam is missing. In this case, the spot of the reflected light applied to the light receiving unit 12 may shift the center of gravity, and an accurate distance measurement value may not be obtained.

Then, the distance measurement result a of the active distance measurement unit A
Is compared with the distance measurement result p of the passive distance measurement unit P, and when the values are substantially the same, it can be determined that the distance is accurately measured even in the active method. Therefore, # 134
Then, it is determined that “| ap |> D”, and if the difference between the two distance measurement values is larger than the allowable value (“Yes” in # 134), the value of the distance measurement result a of the active distance measurement unit A Is determined to be incorrect, and in this case, the distance measurement result p of the passive distance measurement unit P is selected as distance measurement data (# 116). If the difference between the two distance measurement values is small (“No” in # 134), it is determined that both the distances have been measured normally, and in this case,
A more reliable active-type distance measurement result is selected, and the above-described flow after # 124 is executed.

As described above, in the distance measurement value selection circuit 40, the result of distance measurement by one of the distance measurement units is finally selected.
The subsequent photographing processing is executed based on the distance measurement value selected here.

The value of the allowable value D is set to, for example, "100 (stage)". Usually, a reciprocal of the distance or a value equivalent to the reciprocal of the distance is often used (because the output value of the PSD is proportional to the reciprocal of the distance). The values used are used. For example, 1m → 1000 steps, 10m → 1
00 stage, ∞ → 0 stage. Therefore, when the back calculation is performed at 1 m, 1000 steps become 1 (m), and 100
Steps, that is, 1100 steps → 0.909 (m), 900
Step → 1.111 (m), and this range is the range of the distance indicated by the tolerance D.

As described above, the distance measuring apparatus according to the present embodiment
Among the distance measurement values obtained by the active distance measurement unit A and the passive distance measurement unit P, a more reliable distance measurement value is selected as an appropriate distance measurement value.

In the above-described embodiment, an example in which the external luminance is detected by the luminance detecting unit L has been described. In addition to this, a luminance detecting light receiving unit and a photometric calculation unit are separately provided as a luminance determining unit separately from the AE unit. A circuit may be provided, or as shown in FIG. 5, the external luminance may be obtained by a photometric / ranging arithmetic circuit 24 based on the light receiving results of the respective light receiving sections 21 and 22 of the passive distance measuring section P. is there.

[0034]

As described above, in the distance measuring apparatus according to the first aspect, the first means includes the first distance measuring means and the second distance measuring means.
Since the difference between the distance measurement value and the distance measurement means is compared, it is possible to judge the situation where “light beam loss” occurs during active distance measurement, and more reliable distance measurement The result can be obtained.

In the distance measuring apparatus according to the second aspect, the second means determines at least whether or not it is possible to perform the distance measurement by the passive method. Value comparisons are more reliable. Also, as a result of the comparison, even when the distance measurement value of the second distance measurement unit using the passive method is selected, the reliability of the selected distance measurement value can be improved.

In the distance measuring apparatus according to the third aspect, the distance measuring apparatus further comprises:
Since it is determined by the third means whether the measured distance value of the first distance measuring means is a value within a predetermined short distance, if the distance to the subject is within the predetermined short distance, this condition is satisfied. In this case, it is possible to select a more reliable first distance measuring means ranging result, so that higher ranging accuracy can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram schematically illustrating a configuration of a distance measuring apparatus according to an embodiment.

FIG. 2 is a front view showing a camera provided with the distance measuring device according to the embodiment.

FIG. 3 is a block diagram schematically showing a configuration inside a camera.

FIG. 4 is a flowchart illustrating an operation of the distance measuring apparatus according to the embodiment.

FIG. 5 is a block diagram showing another embodiment of the distance measuring apparatus.

[Explanation of symbols]

A: active distance measuring section (first distance measuring means), P: passive distance measuring section (second distance measuring means), L: luminance detecting section, 40: distance measuring value selection circuit.

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01C 3/00-3/32 G02B ⁷ /28-7/32 G03B 13/36

Claims (3)

(57) [Claims] An active type first distance measuring means for projecting distance measuring light toward a subject and measuring a distance to the subject based on a condensing position of the reflected light; Passive type second distance measuring means for receiving natural light with two optical systems and measuring the distance to the subject based on two optical images obtained by the respective optical systems; Means for selecting and outputting any one of the distance measurement results from the distance measurement results obtained from the first and second distance measurement means. The distance measurement value selection means comprises: When the difference between the distance measurement values of the distance measurement means and the second distance measurement means is smaller than a predetermined allowable value, the distance measurement value of the first distance measurement means is selected. (2) A distance measuring device including first means for selecting a distance measurement value of the distance measuring means. 2. The distance measuring apparatus further comprises a luminance detecting means for detecting the luminance of the external world, and the distance measuring value selecting means further comprises: a luminance value of the external field obtained by the luminance detecting means within a predetermined intermediate level. A second means for judging whether the value is a value or not, wherein when the second means determines that the external luminance is a value within the intermediate level, the first means performs a selection process. 2. The distance measuring device according to 1. 3. The method according to claim 1, wherein the distance measurement value selection unit further includes
A third means for judging whether or not the distance value obtained by the distance measuring means is within a predetermined short distance; and wherein the second field means has an external luminance within the intermediate level. Is determined, and when the distance measurement value is determined to be a value within a predetermined short distance by the third means,
3. The distance measuring apparatus according to claim 2, wherein the selection processing is performed by the first means.