JP3080863B2 - 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 the passive type distance measuring device, when the external luminance is low, the amount of natural light reflected by the subject naturally becomes small, and therefore, it becomes difficult to detect the phase difference, and the distance measuring accuracy is reduced. May be reduced or distance measurement may not be possible.

On the other hand, an active type distance measuring device causes a light emitting element to emit light and receives distance measuring light returning from the object to measure the distance to the object. When the external luminance is high, the light receiving element measures the distance to the object. In some cases, the reflected light of the distance light cannot be satisfactorily received, so that the distance measurement accuracy is reduced or the distance measurement cannot be performed depending on the external luminance. Also, in order to measure a distance to a distant subject with high accuracy, it is desirable that the amount of emitted light be large. For this purpose, it is necessary to constantly supply a large current to the light emitting element. Since the capacity of the battery serving as a current supply source is reduced by use, the battery voltage drops when the battery is used to some extent, and a necessary current cannot be supplied to the light emitting element. However, since shooting is possible even in such a state, if active distance measurement is performed on a subject at a long distance, a distance measurement error increases, and a so-called out-of-focus photograph occurs.

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 which can always obtain a highly 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. First distance measuring means of an active type, and natural light reflected by a subject are received by two optical systems, and the distance to the subject is measured based on two optical images obtained by each optical system. A passive second distance measuring means, a distance measuring result selecting means for selecting and outputting one of the distance measuring results from the first distance measuring means and the second distance measuring means, Power supply means for supplying power to the means; and detection means for detecting an output voltage of the power supply means. The distance measuring value selecting means sets a distance measuring range in which the distance measuring by the first distance measuring means can be appropriately performed based on the output voltage of the power supply means detected by the detecting means; When the distance measurement result of the first distance measurement means is a value outside the distance measurement range set by the setting means, a first determination means for selecting the distance measurement result of the second distance measurement means is provided.

In the distance measuring apparatus according to the present invention, in addition to the distance measuring value selecting means, the distance measuring result of the first distance measuring means is a value within the distance measuring range set by the setting means. And a second determining means for selecting a distance measurement result of the first distance measuring means.

According to a third aspect of the present invention, 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 an external luminance obtained by the luminance detecting means within a predetermined intermediate level. And a third determination unit for determining whether the value is equal to or not. Then, when the third determining means determines that the external luminance is a value within the intermediate level, the first or second level
The selection process in the determination means is performed.

[0010]

According to the present invention, there are provided two types of distance measuring means, a first distance measuring means of an active method and a second distance measuring means of a passive method, and one of the distance measuring results is selected by a distance measuring value selecting means.

When performing active distance measurement, the amount of light emitted from the light emitting element depends on the output voltage of the power supply means supplied.
That is, since the power supply voltage gradually decreases in accordance with use, the output voltage is detected by the detecting means, and based on this value, the distance measurement by the first distance measuring means by the active method can be appropriately performed. The range is set by the setting means. In the distance measuring device according to the first aspect, the first determining means includes:
If the distance value of the first distance measuring means is outside the set distance measuring range, the distance value of the passive second distance measuring means is selected.
In the distance measuring apparatus according to the second aspect, in the first and second determining means, if the distance value of the first distance measuring means of the active method is within the aforementioned distance measuring range, the first and second judging means may be used. The distance measurement value of one distance measuring means is selected.

In the distance measuring apparatus according to the third aspect, whether the external luminance is a value within a predetermined intermediate level is judged by the third judging means. With this, both types of distance measuring can be properly performed. It is determined whether or not the situation.

[0013]

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). An optical position detecting device (not shown) such as a CCD or a photo sensor array for receiving two optical images obtained by the above-mentioned operation, and a distance measuring circuit 23 for calculating a distance to a subject based on the result. ing.

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

The distance measuring value selection circuit 40 is provided with the luminance detecting 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 calculation circuits 13 and 23, the light measurement calculation circuit 32, the distance measurement value selection circuit 40, and the like illustrated in FIG. 1 are configured in the CPU illustrated in FIG.

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 into the CPU and the voltage value is checked (# 102, # 104). ). For example, in the case of a camera equipped with two lithium batteries as a power supply, the nominal power supply voltage is set to 6
Assuming that V is V, if the read power supply voltage is 3.8 V or more, it is determined that shooting is possible. Therefore, when the read power supply voltage value is less than 3.8 V (# 1
04 ("NO"), the photographing process becomes impossible, and the user is notified of the fact by display or warning sound, etc.
The procedure proceeds to the treatment (# 106).

The read power supply voltage value is 3.8 V
If this is the case ("Yes" in # 104), the photometric processing for detecting the external luminance is performed by the luminance detecting unit L (# 108).

Next, in # 110, based on the value of the power supply voltage read in # 102, a distance measurement range in which the active distance measurement can be properly performed is set. In the active method, the light emitting element of the light projecting unit 11 emits light toward a subject, but a large current needs to be supplied from a power supply to obtain a large amount of emitted light. However, since the power supply voltage is reduced by use, the light emitting element of the light projecting unit 11 may not be able to emit light with an appropriate amount of emitted light. So, # 1
In step 04, based on the value of the power supply voltage read in # 102, a distance measurement range in which the active distance measurement can be properly performed is set. In this case, a correspondence table as shown in Table 1 below is stored in advance in a memory in the CPU, and a corresponding distance measurement range (switching distance) is determined from the correspondence table based on the power supply voltage read in # 102. l) Search. Then, the retrieved value is set as the value of 1 in a decision block # 128 described below (# 110).

[0022]

[Table 1]

From Table 1, when the power supply voltage is 4.6 V, for example, the switching distance 1 is 3.33 m, and this value is # 1.
It is set as the value of l at 28.

After the switching distance 1 is set in this way, the active distance measuring unit performs the active distance measurement, and the passive distance measuring unit P performs the passive distance measurement (# 112, # 114). And
The results of distance measurement in each of the distance measurement units A and P are supplied to the distance measurement value selection circuit 40 via the distance measurement calculation circuits 13 and 23.

When the power supply voltage is, for example, 3.9 V, the photographing is carried out because the condition of 3.8 V or more for photographing is satisfied, but in this case, a sufficient amount of emitted light cannot be obtained. Therefore, the active distance measurement is not performed, and only the passive distance measurement is performed.

Next, the distance measurement value selection circuit 40 determines whether or not the external luminance obtained by the luminance detecting section L is a high luminance level equal to or higher than Lv14 (# 116). 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 detecting unit L is equal to or higher than Lv14 (“No” in # 116), 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
8). Then, for example, a photographing lens is set based on the set distance measurement data (# 120), the subsequent photographing processing is executed based on the distance measurement value output from the distance measurement value selection circuit 40. (# 122).

On the other hand, if the external luminance is lower than Lv14 ("Yes" in # 116), it is further determined whether or not the external luminance is lower than Lv3 (# 124). When the external luminance is low, the passive system has a small amount of reflected natural light and lacks reliability.
In this case, the reflected light of the distance measurement light is detected favorably, so that the reliability of the distance measurement value is high. Therefore, when the external luminance obtained by the luminance detecting unit L is equal to or lower than Lv3 (“N” in # 124).
o "), the distance measurement value selection circuit 40 selects the distance measurement value (active data) of the active distance measurement unit A and outputs it as distance measurement data (# 126). Subsequent photographing processing is executed based on the distance measurement value output from the distance measurement value selection circuit 40 (# 120, # 122).

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.

When the luminance level is an intermediate luminance level of 3 <Lv <14 ("Yes" in # 124), the determination is made based on the following values.

The distance measurement value selection circuit 40 determines that the distance measurement value obtained by the active distance measurement unit A is equal to the switching distance l set at # 110.
It is determined whether the distance is less than m (# 128). Under the condition of "Yes" in # 124, both the active method and the passive method can effectively measure the distance, but the distance measurement result of the active distance measuring unit A is longer than the set switching distance lm. When the distance is close, it is within the range in which the active distance measurement can be performed properly, and when the distance to the subject is such a short distance, the distance measurement result by the active method is better than that of the passive method. Reliability is high. For this reason, when the distance measurement result of the active distance measurement unit A is shorter than the switching distance lm (“Yes” in # 128), the distance measurement value selection circuit 40
Selects a more reliable distance measurement value (active data) of the active distance measurement unit A and outputs it as distance measurement data (# 126). Then, the subsequent photographing process is executed based on the distance measurement value output from the distance measurement value selection circuit 40 (# 120, # 122).

On the other hand, if the distance measurement result of the active distance measuring section A is larger than the switching distance 1m ("No" in # 128),
The distance measurement value selection circuit 40 selects the distance measurement value (passive data) of the distance measurement value of the passive distance measurement unit P and outputs it as distance measurement data (# 118). Subsequent photographing processing is executed based on this distance measurement value (# 120, # 122).

As described above, the distance measuring apparatus according to the present embodiment
In accordance with the power supply voltage value at the time of photographing, a distance measurement range in which active distance measurement can be performed is set in advance, and the distance measurement is performed for both the active distance measurement unit A and the passive distance measurement unit P. Since a more reliable distance measurement value among the distance measurement values is selected as an appropriate distance measurement value, the distance measurement can always be performed with high accuracy.

It should be noted that in the above-described flowchart, # 1
At 28, the case where the distance measurement result of the active distance measuring unit A is shorter than the switching distance lm and the processing proceeds to # 126 and the distance measurement value of the active distance measuring unit A is selected has been exemplified. As an example in the case where it is determined, the following processing may be performed. That is, in such a situation, it is difficult to determine which method of the distance measurement result is more accurate. Therefore, in such a case, a distance measurement result obtained by averaging the distance measurement value of the active distance measurement unit A and the distance measurement value of the passive distance measurement unit P is used. As described above, by averaging the distance measurement results obtained by both methods to obtain a distance measurement value, high distance measurement accuracy can be obtained. Then, when an averaged distance measurement value is obtained, the result is output from the distance measurement value selection circuit 40, and subsequent photographing processing may be executed based on the distance measurement value (# 120, # 122).

In the flowchart described above,
In the case of searching the correspondence table in Table 1 for the switching distance l in # 110, the switching distance l is calculated based on the read power supply voltage V by the following arithmetic expression or the like.
Can also be calculated. l = 1 /
(0.8−0.1 × V) l: distance (m), V: read power supply voltage (V) Also, regardless of whether the active distance measuring unit A and the passive distance measuring unit P are before or after the distance measuring process. , Can be performed simultaneously.

Further, in the above-described embodiment, the power supply voltage value that can be photographed and the value of the switching distance lm are not limited to the above-described values, but may be changed according to the light emitting performance of the light projecting unit 11 or the like. Just set it.

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, as shown in FIG. 5, each light receiving unit 2 of the passive distance measuring unit P may be used.
It is also possible to determine the external luminance by the photometry / ranging operation circuit 24 based on the light receiving results of the first and second light receiving units.

[0037]

As described above, in the distance measuring apparatus according to the first and second aspects, the distance is measured by both the passive and active type distance measuring means, and the reliability is further increased by the distance value selecting means. Higher distance measurement can be selected. Further, the provision of the setting means makes it possible to set a range in which the first distance measuring means of the active system can appropriately carry out the measurement in accordance with the output voltage of the power supply means. Therefore, active distance measurement can be performed in a state where a sufficient current can always be supplied to the active distance light emitting element, and occurrence of erroneous distance measurement can be sufficiently reduced.

Further, in the distance measuring apparatus according to the third aspect, since the third determining means determines whether the external luminance is a value within a predetermined intermediate level, both types of distance measuring can be properly performed. It is possible to determine that the situation is present, and thereby a more reliable distance measurement result 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.

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 one of the distance measurement results from the distance measurement results obtained from the means and the second distance measurement means; power supply means for supplying power to the respective means; and the power supply means Detecting means for detecting the output voltage of the power supply means. The distance measuring value selecting means, based on the output voltage of the power supply means detected by the detecting means, the distance measurement by the first distance measuring means properly Setting means for setting a distance measurement range that can be implemented; and the first distance measurement Stage ranging results when the value of the outside distance measuring range set by the setting means, distance measuring device and a first determination means for selecting a distance measurement result of the second ranging means. 2. The method according to claim 1, wherein the distance measurement value selecting means is configured to determine whether the distance measurement result obtained by the first distance measuring means is within a range set by the setting means. 2. The distance measuring apparatus according to claim 1, further comprising a second determining means for selecting a distance result. 3. 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: an external luminance obtained by the luminance detecting means within a predetermined intermediate level. A third determining means for determining whether the external luminance is a value within the intermediate level, if the third determining means determines that the external luminance is a value within the intermediate level.
3. The method according to claim 1, further comprising the step of:
The distance measuring device as described.