JP3045561B2 - Camera ranging 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, and more particularly to an active triangular distance measuring apparatus capable of switching between multi-point distance measurement and central one-point distance measurement.

[0002]

2. Description of the Related Art A recent camera measures a distance at a plurality of points on a screen and focuses on an object at the shortest distance among the distance measurement results. Even if there is a subject, a failure called "missing" does not occur. However, when it is desired to focus on the center subject reliably, it is more effective to measure the distance using only the center distance measuring point.
Some cameras switch between two ranging modes.

However, the active AF has the following characteristics regardless of whether it is a multipoint or a single point.

FIG. 5 is a diagram showing the principle of an active AF device. The light reflected from light emitted from a light source 21 to a subject 22 is reflected by a light receiving lens 23 to a semiconductor position detecting element 25.
The image is formed on the upper side, and the distance measurement circuit 27 is configured to calculate the distance from the image formation position to the subject. A PSD is popular as the semiconductor position detecting element 25, and (I ₁ −I ₂ ) / (I ₁ + I ₂ ) is obtained in the distance measuring circuit 27 from the signal light current components I ₁ and I _{2 of the} two electrode terminals.
Alternatively, the subject distance is obtained by calculating I ₁ / (I ₁ + I ₂ ).

[0005]

As can be seen from FIG. 6 in which the relationship between 1 / (subject distance) and (I ₁ −I ₂ ) / (I ₁ + I ₂ ) is plotted, from ∞ to a certain distance range Are 1 / (subject distance) and (I ₁ −I ₂ ) / (I ₁
+ I ₂ ), there is a proportional relationship. However, when the distance is short, the angle of incidence of the reflected beam increases, so that the image is formed out of the light receiving surface of the semiconductor position detecting element 25, and (I
_{The 1-} I ₂ ) / (I ₁ + I ₂ ) output will output the same value as a long distance.

For this reason, when the subject is too close, there is a problem in that an erroneous distance measurement output at a long distance is generated, and an out-of-focus photograph is taken.

On the other hand, in the multi-point distance measuring apparatus, as is apparent from FIG. 6, the short distance measuring limit at the center L2 is shorter than the distance measuring limit at L1. Therefore, there is a problem that the distance measurement limit is longer in the central one-point distance measurement mode than in the multi-point distance measurement mode. The camera distance measuring apparatus of the present invention has been made in view of such a problem, and its purpose is to exceed the distance measuring limit on the short distance side of the central distance measuring point in the central single point distance measuring mode. In this case, by using the output of a ranging point that can measure the distance to a shorter distance, it is possible to accurately determine the closest possible distance without increasing the size of the semiconductor position detection element. It is to provide a device.

[0008]

In order to achieve the above object, a distance measuring apparatus for a camera according to the present invention measures a distance between a central point of a photographing screen and at least one adjacent point adjacent to the central point, and measures at least the distance between the central point and at least one adjacent point. A multipoint ranging mode that has a distance measuring device in which the closest distance measurement limit A of one adjacent point is closer than the closest distance measurement limit B of the center point, and measures the distance between the two points; In a camera capable of switching between a single point ranging mode and a single point ranging mode, the distance measuring operation of both the central point and the at least one adjacent point is performed even in the single point ranging mode, and the distance measurement at the adjacent point is performed. The result is the first based on the close range limit B
Only when the distance is shorter than the predetermined value and the distance is longer than the second predetermined value based on the closest distance measurement limit A, the photographing lens is driven based on the distance measurement result at the adjacent point. It is.

[0009]

That is, according to the present invention, in a camera having a single-point ranging mode and a multi-point ranging mode, the ranging result at an adjacent point adjacent to the center point is determined based on the closest ranging limit B of the center point. 1 based on the closest distance limit A of the adjacent point on the short distance side from the predetermined value of 1
When the distance is farther than the predetermined value, the result of the distance measurement at the adjacent point is adopted, so that the close distance that can be photographed is accurately determined.

[0010]

FIG. 1 is a block diagram showing one embodiment of the present invention, and FIG. 2 is an IRED L as each light emitting element.
1, L2, L3, PSD output I1,
This shows the relationship between I2 and the subject distance.
The (subject distance) is represented by (I ₁ −I ₂ ) / (I ₁ + I) on the vertical axis.
It is the figure which plotted ₂ ).

In FIG. 1, light is projected in time series at three places of a subject 5 within a shooting angle of view by IREDs L1 to L3, and the reflected light is condensed on a PSD 9 by a light receiving lens 7, and the reflected light is reflected. By detecting the reflected light currents I ₁ and I ₂ indicating the positions of the spots by the distance measuring circuit 11, three distances within the shooting angle of view are measured.

A distance measurement value at each point is given from the distance measurement circuit 11 to the CPU 13, and based on the distance measurement value, the photographic lens 17 is driven via the photographic lens drive circuit 15 to arbitrate at the in-focus position.

The mode switch connected to the CPU 13 selects one of a center one-point distance measurement mode and a three-point distance measurement mode.
It is. Further, the CPU 13 determines that the distance measurement value is
Close warning LE if the shooting distance exceeds 7
D19 blinks to draw the photographer's attention.

FIG. 2 (a) shows the vertical axis of the output of the distance measuring circuit (I
₁₋ I ₂ ) / (I ₁ + I ₂ ), and the distance measurement circuit output of each IRED showing 1 / l on the horizontal axis. FIG. 2 (b) shows the actual result of the combination of the IRED and the distance measurement output. Of the subject distance, and the vertical axis represents the subject distance calculated value,
It is plotted as 1 / l on the horizontal axis.

As can be seen from the figure, it can be seen that the distance can be accurately measured to a short distance in the order of L1, L2, L3.

The operation of FIG. 1 will be described below with reference to the flowchart of FIG.

First, in step S1, the release S
It is determined whether or not W is ON, and if it is ON, it is determined whether or not the mode SW is ON (step S2). If it is ON, it is determined to be the central one-point ranging, and the central one-point ranging flow from step S3 is started, and if it is OFF, multipoint ranging is started from S10.

That is, in step S3, the IRED L2 corresponding to one central point is caused to emit light, and a subject distance calculation value F (L2) based on L2 is obtained. Next, in step S4, the IRED L1 emits light to obtain a subject distance calculation value F (L1) based on L1.

In step S5, F (L1) becomes L1
If it is shorter than the photographable close distance CP0 of step S7, step S7
Then, the close warning LED 19 flashes, and the process returns to step S1. If F (L1) is farther than CP0, step S6 is executed.

In step S6, it is determined whether or not F (L2) is shorter than the distance measurable closest distance CP1 of L1, and if it is, the photographing lens 17 is driven based on F (L1) in step S8 to move away. For example, in step S9, the photographic lens 17 is driven based on F (L2).

In the close range, the size of the subject is considered to be very large with respect to the photographing screen. Therefore, even if a slightly shifted distance measuring point value in the photographing screen is used as shown in FIG. There is no.

When the light projection spot L3 deviates, there is no problem because the distance measurement value of L3 is not used.

Further, steps S10, S11, S12
In step S13, ranging of the ranging points corresponding to the IREDs L1, L2, and L3 is performed, and it is determined whether or not F (L1) is closest in the next step S13. .

In step S16, step S5
Similarly to the above, F (L1) is a close distance CP0 at which L1 can be photographed.
It is determined whether they are closer than each other.
Then, the close warning LED 19 flashes, and the process returns to step S1. If F (L1) is farther than CP0, the photographing lens 17 is driven based on F (L1) in step S8.

Further, in step S13, F (L
If 1) is not the closest, step S14 is executed. In step S14, it is determined whether or not F (L2) is closest.
The photographing lens 17 is driven based on 2). If it is not the closest distance, the flow jumps to step S15 to drive the photographing lens 17 based on F (L3).

Thereafter, an exposure operation (not shown) is performed, and after winding up of one frame is completed, the next photographing standby operation is started.

[0027]

As described in detail above, according to the present invention,
It is possible to accurately determine the close distance at which the image can be captured without increasing the size of the semiconductor position detecting element chip, and it is possible to contribute to a reduction in the space and cost of the camera. Also, by adopting the above-mentioned distance measurement value only when the distance measurement value of the smaller distance measurement point at which the distance can be measured is smaller, the conventional distance measurement at the central point can be performed. On the other hand, it is possible to take a picture closer.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one embodiment of the present invention.

FIGS. 2A and 2B are diagrams showing a relationship between a subject distance, a PSD output, and a subject distance calculation value.

FIG. 3 is a flowchart for explaining the operation of FIG. 1;

FIG. 4 is a view showing different distance measurement points in a shooting screen.

FIG. 5 is a configuration diagram of a conventional active AF device.

FIG. 6: 1 / (subject distance) and (I ₁ −I ₂ ) / (I ₁ )
+ I ₂ ).

[Explanation of symbols]

L1 to L3: IRED, 5: subject, 7: light receiving lens,
9 PSD, 11 distance measuring circuit, 13 CPU, 15 photographing lens driving circuit, 17 photographing lens, 19 near warning LED.

Claims (1)

(57) [Claims] 1. A distance measurement is performed between a center point of a photographing screen and at least one adjacent point adjacent thereto, and a close distance measurement limit A of the at least one adjacent point is larger than a close distance measurement limit B of the center point. A single-point ranging mode for a camera that has a ranging device that is on the short distance side and can switch between a multi-point ranging mode that measures the distance between both points and a single-point ranging mode that measures only the center point Sometimes, the distance measurement operation of both the center point and the at least one adjacent point is performed, and the distance measurement result at the adjacent point is closer to the first distance than the first predetermined value based on the closest distance measurement limit B. And a camera for driving the taking lens based on the result of distance measurement at the adjacent point only when the distance is longer than a second predetermined value based on the closest distance measurement limit A. Distance measuring device.