JP3048744B2 - Camera ranging device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention automatically measures the distances to a plurality of objects existing in an object scene, selects the most appropriate object from the plurality of measurement data, and focuses on the objects. The present invention relates to a distance measuring device for a camera having a multi-auto focus function for automatically driving a lens so as to match.

[0002]

2. Description of the Related Art A conventional multi-auto focus camera using an infrared active system uses a plurality of light emitting LEDs or moves one light emitting LED to the left and right for a plurality of objects (Japanese Patent Application Laid-Open No. Sho 59-146032). The distance to each subject is detected by using a large or a plurality of light receiving PSDs (Japanese Patent Laid-Open No. 3-60505). Then, the subject that has obtained the closest distance information from the plurality of pieces of distance information is set as the main subject, and the lens is driven to focus on the main subject.

[0003] The multi-auto focus function by the infrared active method is widely used in compact cameras. Compact cameras are often used by general users different from professional photographers, and are mainly used for snap shots of people and long-distance shots of landscapes and the like. . In snap photography of a person or the like, for example, when three persons are photographed between 1 m and 4 m, a camera having a multi-autofocus function has a plurality of distance measurement targets. Since there is a high possibility that at least one distance measuring target can measure one of the three targets, it is possible to prevent the hollow phenomenon. FIG. 4A shows a case where the leftmost distance measurement target matches the position of the leftmost person. Even if the center and rightmost distance measurement targets are hollow, the closest distance measurement target is closest to the leftmost distance measurement target. Distance information can be obtained. FIG. 5A shows the relationship between the subject distance in the distance measurement result and the distance information from the optical axis of the light receiving lens in each distance measurement target.

[0004]

However, the projected image of the light-emitting LED is as large as ten to several centimeters in the range of 1 m to 4 m, and since there are a large number of distance measurement targets, the projected image is illuminated as shown in FIG. (If the center is illuminated correctly and the left and right objects are illuminated incorrectly, but the object distances of objects c2 and a2 are output as well as object b2), the center of gravity of the reflected light shifts Sometimes. For example, as shown in FIG. 5B, when the subject c2 is closest, c2 is selected as the closest distance measurement information, resulting in erroneous distance measurement. As a countermeasure against this, in the prior art proposed above, a configuration in which the number of light emitting and receiving elements is increased can be considered, but such a configuration complicates the mechanism. In addition, there is a disadvantage that a large space must be secured and the price rises. SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned drawbacks, and to provide a camera distance measuring apparatus having a multi-auto focus function which enables accurate focusing on a subject by easy photographing while reducing the size and cost of the mechanism. To provide.

[0005]

In order to achieve the above object, a distance measuring apparatus for a camera according to the present invention is an external distance measuring apparatus for a camera which measures a plurality of positions on a screen. A distance measuring unit that receives reflected light from a plurality of subjects with one PSD and outputs a plurality of subject distances on the light receiving side by sequentially emitting the plurality of LEDs; The distance measurement range by the LED is set between the first distance and the second distance, and the LED at the center is
Is set between a third distance smaller than the first distance and a fourth distance larger than the second distance, and the object distance of the distance measurement target by the LEDs arranged on both sides is set to When the distance is out of the range from the first distance to the second distance, the object distance of the distance measurement target by the LED arranged at the center is selected, and the object distance of the distance measurement target by the LEDs arranged on both sides is selected. Is within the range from the first distance to the second distance, the object distances of the distance measurement targets by the plurality of LEDs are compared, the closest object distance is set as the temporary main object distance, and the temporary main object is Calculating the difference between the distance and the object distance of the distance measurement target by the LED disposed at the center, and when the difference is smaller than a predetermined value, the distance of the distance measurement target by the LED disposed at the center; Select body distance, when said difference is greater than a predetermined value are constituted from a control unit for selecting a subject distance of the closest.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail with reference to the drawings. FIG. 1 is a schematic diagram showing an embodiment of a camera distance measuring apparatus according to the present invention. This figure shows in detail a basic optical system portion using three beams as a multi-autofocus function. The three-point integrated infrared-emitting LED 1 emits light in the order of the elements 1b, 1a, and 1c, and the objects 5a, 5 separated by L from the light projecting lens 3 via the light projecting lens 3.
b and 5c, respectively. The reflected light from the subject is detected at the respective positions of 2b, 2a and 2c of the position detecting element (PSD) 2 using a silicon photodiode via a light receiving lens 4 separated from the light projecting lens 3 by a base length A.

Based on the optical axis of the light receiving lens 4, the distances to 2a, 2b and 2c on the PSD 2 are x, y and z, the focal length of the light projecting lens 3 is f, the focal length of the light receiving lens 4 is fp, Assuming that the interval between 1a, 1b and 1c of the light emitting LED 1 is p, x, y and z are Can be represented by

The information obtained in 2a, 2b and 2c on the PSD 2 is converted into a signal by the AF-IC circuit 6,
7 is calculated. Here, the distances x, y and z on the PSD 2 can be obtained from the information at 2a, 2b and 2c, and x, y and z are obtained from the light projecting lens 3 according to the equations (1), (2) and (3). Since the distance is proportional to the reciprocal 1 / L of the distance to the subject, the subject distance L from the light projecting lens 3 can be obtained.

FIG. 2 is a diagram showing the proportional relationship between the distances x, y and z from the light receiving lens optical axis obtained from the PSD and the reciprocal 1 / L of the object distance. As the subject distance becomes shorter, the distances x, y, and z from the optical axis of the light receiving lens to the irradiation light positions 2a, 2b, and 2c on the PSD become longer, and conversely, as the subject distance approaches infinity, the PSD is irradiated. Irradiating light approaches parallel to the optical axis of the light receiving lens, so that the distance x, y
And z become shorter. Also, the PS by the light emitting LED 1c
As the distance information z on D becomes closer to the closest distance, the proportional relationship with the subject distance reciprocal 1 / L is broken. Floodlight LED1a
At a distance x by 1 / L
Is broken. This is due to the relationship between the size of the PSD element, the focal length of the light receiving lens, the pitch of the LED elements, and the like.

FIG. 3 is a flow chart for explaining the operation of the camera distance measuring apparatus according to the present invention. By pressing the release button 8, a light emission command is issued to the light emitting LED. The floodlight LED emits light in the order of center, left and right,
The light receiving PSD receives light corresponding to each light emission, and distance information of each subject is obtained. The CPU 7 receives the information and performs control as indicated by a dotted line. Left L as shown in FIG.
Since there is no proportional relationship on the closest side in the proportional line z between the distance information by the ED and the subject distance, accurate measurement cannot be performed.

In addition, the distance information from the right LED and the proportional line x between the object distance are not proportional to the infinity side, so that distance measurement becomes impossible. As a countermeasure, the slope of the proportional line must be reduced. Specifically, the focal length of the light receiving lens 4 may be shortened, but the resolution of the distance information deteriorates. When a large PSD is used, it is disadvantageous in terms of space and cost. Therefore, in the present invention, a distance measurement area limited to the distance information by the left and right LEDs is provided, thereby improving the resolution of the distance information, saving space, and reducing cost. The respective distance information obtained by the PSD is calculated by the CPU 7, and the respective object distances can be obtained. Here, it is assumed that the subject distance obtained by calculating the distance information obtained by the left LED 1a is a, the subject distance obtained by the center LED 1b is b, and the subject distance obtained by the right LED 1c is c.

A procedure for selecting an optimum subject distance (that is, a main subject) using the three subject distances will be described with reference to FIGS. The object distances A (first distance) and B (second distance) shown in FIG. 2 are arbitrary object distances (A = 0.7 m, B = 4 m). There is a high possibility that out-of-focus or other out-of-focus occurs frequently. First, the CPU 7 compares the subject distances a and c of the left and right LEDs with arbitrary subject distances A and B by comparing a <A and c<A or a<A and c> B or a> B and c> B or If a> B and c <A, the main subject is determined to be the center (subject distance b). In other words, the hollowing-out phenomenon is unlikely to occur except between arbitrary subject distances AB. Conversely, if distance measurement is performed at three locations, erroneous distance measurement may occur. Therefore, erroneous distance measurement is prevented by such determination.

On the other hand, if the result of comparison between the object distances a and c by the left and right LEDs and the arbitrary object distances A and B is A ≦ a ≦ B or A ≦ c ≦ B, then the object distances a, b and c And select the closest subject distance. This subject distance is set as a temporary main subject distance d. In other words, since it is considered that the hollow phenomenon easily occurs between arbitrary object distances AB, a large number of areas (here, the center, right and left three places) other than the center are measured to prevent the hollow.

When the temporary main subject distance d is obtained, it is compared with the subject distance b by the center LED. If | db | ≦ ΔD, the main subject is set to the center (subject distance b).
Here, ΔD is an arbitrary value in the vicinity of the depth of field determined by the present camera, and as shown in FIG. 5B, the maximum value of erroneous data obtained by the displacement of the center of gravity of the signal light (from the original value). This is performed in order to prevent the temporary main subject distance d from becoming close due to the displacement of the center of gravity of the signal light, and to prevent the subject distance from becoming the main subject distance. That is,
Defocusing is slightly prevented from being out of focus due to a shift in the center of gravity of the signal light even when the distance to the main subject is measured, by preventing hollowing out.

If the comparison result between the provisional main subject distance d and the subject distance b by the center LED is | d−b |> ΔD, the main subject is located closest to the three locations (provisional main subject distance d). Shall be In other words, it is here that for the first time the hollowing out is prevented. By performing such control, the CPU 7 determines the main subject and sets the lens drive circuit 9.
To drive the lens to a position corresponding to the main subject distance.

[0016]

As described above, according to the present invention,
It is possible to prevent out-of-focus caused by hollowing out which is likely to occur when taking a commemorative photograph or a snapshot of a person or the like with easy photographing. In addition, it is possible to prevent erroneous distance measurement due to multi-auto focus, which occurs when shooting an infinite landscape or the like. Furthermore, since the distance measuring unit sequentially emits the light-emitting LEDs, it can be configured with a single light receiving PSD element, and by providing a distance measuring range to each distance measuring target, a small element can be used without lowering the resolution. it can. Therefore, space saving and cost reduction can be realized with a simple mechanism. Further, by providing the distance measurement range to each distance measurement target as described above, the drive power of the left and right LEDs can be made lower than the drive power of the center LED, so that the mounting circuit can be reduced in size and power consumption can be reduced. You can also.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an embodiment of a camera distance measuring apparatus according to the present invention.

FIG. 2 is a diagram for explaining a relationship between distance information obtained from a silicon photodiode and a distance to a subject.

FIG. 3 is a flowchart illustrating the operation of the camera distance measuring apparatus according to the present invention.

FIG. 4 is a diagram for explaining an example of a projection position of a multi-projection beam displayed on a finder.

5 is a diagram illustrating a relationship between a subject distance indicating a distance measurement result in FIG. 4 and distance information from an optical axis of a light receiving lens in each distance measurement target.

[Explanation of symbols]

 Reference Signs List 1 infrared emitting LED 2 position detecting element (silicon photodiode) 3 light emitting lens 4 light receiving lens 5a, 5b, 5c subject 6 AF control circuit (AF-IC) 7 CPU 8 release button 9 lens drive circuit

Claims (1)

(57) [Claims] 1. An external distance measuring device for a camera for measuring a distance at a plurality of positions in a screen, wherein a plurality of LEDs are provided on a light projecting side, and the plurality of LEDs emit light in order, so that a plurality of LEDs are arranged on a light receiving side by one PSD. A distance measuring unit that receives reflected light from an object and outputs a plurality of object distances; and a distance measuring range of the LEDs on both sides of the plurality of LEDs is set between a first distance and a second distance. The distance measurement range by the LED of the unit is set between a third distance smaller than the first distance and a fourth distance larger than the second distance, When the object distance is out of the range from the first distance to the second distance, the object distance of the distance measurement target by the LED arranged at the center is selected, and the distance measurement target by the LEDs arranged on both sides is selected. Subject When the distance is within the range from the first distance to the second distance, the object distance of the distance measurement target by the plurality of LEDs is compared,
The closest subject distance is set as the temporary main subject distance, and the difference between the temporary main subject distance and the subject distance of the distance measurement target by the LED arranged at the center is calculated. And a control unit for selecting an object distance of a distance measurement target by an arranged LED and selecting the closest object distance when the difference is larger than a predetermined value.