JPH0517484B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a focus adjustment device that has a plurality of distance measurement fields and is equipped with a distance measurement circuit that performs distance measurement in each field of view.

Conventionally, in devices that perform distance measurement using a single distance measurement field of view, the distance measurement field of view is so narrow that the subject may fall out of the field of view.

Furthermore, when a wide field of view for distance measurement is used, erroneous distance measurement occurs due to the inclusion of objects at multiple distances, such as the background.

For this improvement, even if distance measurement results from multiple fields of view are used, if a simple selection such as closest distance is used, erroneous distance measurement may occur due to results such as the foreground.

The present invention has been made in view of the above-mentioned matters, and includes a light projecting means that projects a light beam onto a plurality of optical axes, and a light projector that receives reflected light from a measurement target of the projected light beam on each optical axis. It has a plurality of light receiving means, and is equipped with a distance measuring circuit that obtains an object distance signal for the measurement target for each optical axis according to the output of each light receiving means, and calculates the object distance in each ranging field corresponding to each optical axis. In a focus adjustment device that detects and adjusts focus, an object is detected in a distance measurement field of view at a center portion according to an output of a light receiving means for receiving reflected light from a measurement target of a projected light beam on a central optical axis among the optical axes. a first detection circuit that detects a distance value; and a second detection circuit that detects an average value of each object distance value in a plurality of distance measuring fields according to outputs from at least two light receiving means among the plurality of light receiving means. a detection circuit; and a selection circuit for selecting a detection result representing a short distance from among the object distance value detected by the first detection circuit and the average value detected by the second detection circuit; By adjusting the focus based on the detection results, sufficient consideration is given to the subject located close to the center, and the focus is adjusted to take into consideration subjects such as the foreground located outside the center, allowing for various types of shooting. It is an object of the present invention to provide a focus adjustment device that allows suitable focus adjustment to be made on a screen as well.

Figure 1 shows an example of the operation of the main unit, with an example of the subject on the right, its context and distance measurement results on the left with the arrow on the left, an example of conventional average distance measurement with A on the right, and M with the closest result. , C shows an example of distance measurement only at the center.

That is, as shown in 1-1, the same result is obtained for all flat object surfaces. However, as shown in 1-2, if there is a distant view (background) in the distance measuring section near the center, the subject will be brought into focus by the background in average distance measurement.

Also, as shown in 1-3, if there is a subject in the center, the average distance measurement will still focus on the front.

On the other hand, if you include the foreground for arrangement, it will be 1-4.
As shown in Figure 2, when distance measurement prioritizes the closest object, the object is drawn to the foreground and becomes the rear focus.

Furthermore, when photographing two people, as shown in 1-5, the background was measured in the central distance measurement, and even in the average distance measurement, the subject was brought into focus due to the background.

On the other hand, according to the present invention, center-weighted ranging is adopted in addition to average multi-point ranging, so 1-
In the cases shown in 1 to 1-3, select the main subject and adjust the focus, and in the cases shown in 1-4, prevent the foreground from being in focus, and further as shown in 1-5. This can prevent the background from being brought into focus in various situations.

For the above purpose, the present invention adopts the following configuration.

Figure 2 shows an embodiment of the present invention, in which 11 light emitting elements and 12 optical members have a slight angle difference.
Three beams 3, 14, and 15 are projected toward the object with a slight vertical difference, and the light is projected onto the object surface as shown in FIG. 3.

In this case, for distance measurement, this beam is scanned from the closest side to the infinity side in the direction shown in Figure 2, and at the same time, a photographic lens (not shown) is focused on the corresponding distance.
Automatic focusing is performed by stopping this scanning action based on the distance measurement signal when focusing is achieved.

The reflected light from this scanning on the object surface is projected onto 18 light-receiving photoelectric conversion elements by 17 light-receiving lenses, and the light-receiving system uses 19, 20, 21 in FIG.
Corresponding to the movement of each light point (distance measuring part) to the right, 19
The light point changes from 22 to 23 in Figure 4, the light point 20 changes from 24 to 25 in Figure 4, and the light point 21 changes from 26 to 27. This causes the light spot to move to the light receiving section.

As each light point moves, the light intensity of the light receiving section changes, that is, the photocurrent of each phototransistor changes, that is, 22→2.
As the wire 3 moves, the current in the 28 wires, which increases at first, eventually changes to increase in the current in the 29 wires.

Each of these photocurrents undergoes current inversion by a current mirror circuit constituted by 30 to 35 diodes and 36 to 41 transistors.

As a result, the light intensity change from 22 to 23 is 28 to 29
This is converted into a current increase of 42→43.

As a result, the 44th wire has a current corresponding to the amount of light received at 22, 24, and 26, and the 45th wire has a current of 23, 25, and 27.
A current flows in accordance with the amount of light received, and it becomes possible to immediately measure the average distance of each light spot. This current is 4
It is converted into a voltage by resistors 6 and 47, and as the scanning progresses, the current changes from 44 to 45 due to the change in light intensity from 22 to 23, that is, the voltage on line 44 increases and the voltage on line 45 decreases.

48 comparators output a signal that becomes High when the light spot is centered on average.

Similarly, the 49th comparator compares the light intensity of (22+24) and (23+25), the 50th comparator compares the light intensity of (22+26) and (23+27), and the 51st comparator compares the light intensity of (24+26) and (25+2).
7) Compare the amount of light.

A comparator 52 compares the light amounts of the central distance measuring sections 24 and 25.

As a result, the distance measurement output of the average of three points is obtained by the comparison of 48, the distance measurement output of two out of three points is obtained by the comparison of 49 to 51, and the distance measurement output of the central part is obtained by the comparison of 52.

Then, by taking the logical sum of each of the above outputs with the OR gate of 53, the faster one, that is, the closer one, is focused by the above distance measurement scanning, and a high is output to the 54 terminal, and the known automatic distance measurement is stopped in the middle of scanning. At least adjust the focus.

In the embodiment described above, a plurality of two fields of view are provided in three distance measurement fields, but it is also possible to extend the field of view to three or more fields, for example, to three out of five fields.

Although external light removal is also omitted in this case, it goes without saying that it is practically necessary to consider it as similar inventions by the same inventors.

Although a phototransistor is used in this case, a similar photoelectric conversion section may also be used.

Also, in actual circuits, it is not limited to current,
It goes without saying that similar decision logic is possible using structures such as MOS and CCD.

As explained above, in this case, easy-to-use automatic distance measurement can be realized using multiple distance measurement results based on multiple distance measurement fields of view.

In addition, multiple processing can be easily configured in parallel using a highly sensitive photo transistor and a current mirror circuit that easily achieves high accuracy, and can be realized using easy bipolar technology in combination with a simple comparator.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the present case and the conventional example, Fig. 2 is an optical diagram of an implementation of automatic distance measurement of the present case, Fig. 3 is a diagram of the light projection pattern of the present case, and Fig. 4 is a circuit diagram of an example of the processing circuit of the present case. . 17... Light receiving lens, 18... Photoelectric conversion element.

Claims (1)

[Scope of Claims] 1. A light projecting means for projecting light beams onto a plurality of optical axes, and a plurality of light receiving means for respectively receiving reflected light from a measurement target of the projected light beams on each optical axis,
Equipped with a distance measuring circuit that obtains an object distance signal for the measurement target for each optical axis according to the output of each light receiving means,
In a focusing device that detects the object distance in each distance measurement field of view corresponding to each optical axis and adjusts the focus, the device receives reflected light from the measurement target of the projected light flux on the central optical axis among the optical axes. a first detection circuit that detects an object distance value in a central range-measuring field of view according to an output of the light-receiving means; and a plurality of distance-measuring fields of view according to outputs from at least two light-receiving means among the plurality of light-receiving means. a second detection circuit that detects the average value of each object distance value at , and a short distance between the object distance value detected by the first detection circuit and the average value detected by the second detection circuit; 1. A focus adjustment device comprising: a selection circuit that selects a detection result representing a focus adjustment circuit; and focusing is performed based on the selected detection result.