JPH0738048B2 - Camera rangefinder - Google Patents

Description

TECHNICAL FIELD The present invention relates to an active-type camera distance measuring device.

(Prior Art) Various methods are used for auto-focusing (automatic focus adjustment) of a camera, one of which is a distance to a subject (hereinafter referred to as “subject distance”) by using an active distance measuring device. Is measured, and the photographing lens is moved according to the distance to bring the subject into focus.

FIG. 5 is an explanatory view of the principle of the active distance measuring system,
In the figure, 1 is a projection lens for distance measurement, 2 is a light receiving lens for distance measurement, 3 is an infrared emitting LED, 4 is a subject, and 5 is a PSD (Position Sensitive Device) as a light receiving element.

The PSD 5 is a light receiving element that can obtain _two current outputs I ₁ and I ₂ from the element when the spot image P is received on the element surface as shown in FIG. When the distance from the center of the element surface to the spot image P is x, the following relationship exists between the distance x and the current outputs I ₁ and I ₂ .

x = Kl _n (I ₁ / I ₂ ) K: constant Then, the image of the object at the point of infinity is formed in the center of PSD5,
At this time, assuming that the taking lens (not shown) is set to focus on the point at infinity, when the subject 4 at a finite distance is measured next, reflection of the projected spot image is reflected from the center on the PSD 5. It will be imaged at x.

Then, the following relationship is established between the distance R to the subject 4 and the distance x.

R = B · f ₂ / x where B is the distance between the optical axes of the light projecting lens 1 and the light receiving lens 2 (base line length), and f ₂ is the focal length of the light receiving lens 2 (see FIG. 5).

On the other hand, when the origin on the optical axis when the taking lens is in focus at the point at infinity and the position on the optical axis of the taking lens in focus with respect to the subject distance R is y, y is out of focus. It represents the quantity, 1 / R + 1 / (f + y) = 1
It has a relationship of R = f + f ₂ / from / f. However, f is the focal length of the taking lens.

Therefore, the relation between x and y is Bf ₂ / x = f + f ₂ / y,
The currents I ₁ and I ₂ of the distance measuring element can be calculated to obtain x, and the focus shift amount y can also be obtained.

By the way, in recent years, various attempts have been made to widen the image-capturing area of the autofocus camera as well, and there are particularly many demands for close-up photography. However, in the conventional active method, as the subject 4 approaches, the spot image P moving on the PSD 5 moves to the left in FIG. 6, and as the amount of movement approaches half L / 2 of the length L of PSD 5, There was a problem that it began to protrude from the top of PSD5 and finally it protruded, making it impossible to measure distance accurately. Therefore, it is possible to increase the length L of the PSD 5 in the longitudinal direction, but the length L of the PSD 5 is also limited due to the installation space in the camera and the cost.

Even if the reflected light from the subject 4 in the vicinity can be received by the PSD 5 light, the reflected light becomes strong as the subject 4 approaches because the light emission amount of the LED 3 is constant.
There was a problem that the output of D5 increased and became saturated in the full dynamic range, and accurate distance measurement could not be performed. In this case, if the output of LED3 is increased in order to improve the distance measuring ability in the long distance, it becomes more and more impossible to measure the distance in the short distance.

(Object and Structure of the Invention) The present invention has been made in view of the above points, and an object thereof is to enable accurate distance measurement in an active type distance measuring device. Multiple light-emitting elements arranged at different positions, a light-receiving element that receives the light reflected from the light-emitting element and outputs an electric signal according to the distance to the object, and selectively emits light from the light-emitting element. , Of the light emitting element at least on the light receiving element side of the light emitting element, and the light emitted by the light emitting element which is less intense than the light for long distance measuring and which is not the light receiving element side of the light emitting element A light emitting circuit capable of selectively outputting light for short distance measurement, an arithmetic circuit for calculating the distance to a subject based on an electric signal from the light receiving element, and an arithmetic circuit for calculating the distance Distance
The light-emitting element selected by the light-emitting circuit corrects the correction time according to the selected light-emitting element, and the light-emitting element selected by the light-emitting circuit emits light. If not, the distance measuring device of the camera is configured with the control circuit that controls the operation of the light emitting circuit so that the other different light emitting elements sequentially emit light.

(Example) The present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of a distance measuring device for a camera according to the present invention, in which the same reference numerals as in FIG. 6 indicate the same components.

In FIG, 6 is a infrared LED as a light emitting element, two light emitting portions L ₁ is for long range distance measuring at different positions in the base A direction as shown in FIG. 2 to LED 6, the light emitting portion L ₂ PSD5 is for short-range distance measurement, therefore, the emission intensity of the light-emitting unit L ₁ is Yes and greater than the light emitting portion L _2, also the light emitting portion L ₂ is
It is installed in a position not on the side.

Reference numeral 7 is a light emitting circuit for selectively emitting light from the light emitting portions L ₁ and L ₂ of the light emitting element 6, 8 is an arithmetic processing circuit for calculating the subject distance R based on the output current from the PSD 5, and 9 is the calculated subject distance R. An A / D conversion circuit for A / D conversion, a correction value circuit 10 for presetting a correction value for correcting the calculated subject distance R,
Reference numeral 11 is an A / D conversion circuit that A / Ds the correction value, 12 is a lens actuator that moves a photographing lens (not shown), and 13 is a microcomputer that controls each circuit.

It should be noted that S ₁ and S ₂ are switches that are turned on by operating the release button. S ₁ is turned on when the release button is lightly pressed down by one step, and S ₂ is the release button that is pushed deeper.
Turns on when the button is pressed down.

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

First, when the photographer depresses the release button lightly by one step, the switch S ₁ is turned on (F-1), a light emission command is output from the microcomputer 13 to the light emitting circuit 7, and the light emitting circuit 7 measures the distance from the light emitting portion L _{1 of the} LED 6. An infrared light pulse for distance is emitted (F-2). The infrared light pulse is projected forward through the light projecting lens 1, is reflected by the subject 4, and passes through the light receiving lens 2.
Received on PSD5. Currents I ₁ and I ₂ are output from the PSD 5 to the arithmetic processing circuit 8.

Next, the arithmetic processing circuit 8 judges whether or not the output currents I ₁ and I ₂ are equal to or higher than the minimum level required for the arithmetic (F-3). If it exceeds the minimum level, it is next determined whether the output exceeds the dynamic range of PSD5, that is, whether the output of PSD5 is in a saturated state (F-4). In steps (F-3) and (F-4), it is determined whether the output of PSD5 is within its dynamic range. If the output of PSD5 is within this dynamic range, the subject distance R is calculated using the above-described predetermined calculation formula, A / D converted by the A / D conversion circuit 9, and read into the microcomputer 13 (F- 5) The distance measurement ends.

When the output of PSD5 is not sufficient or when it is in a saturated state, the arithmetic processing circuit 8 outputs a re-emission signal to the microcomputer 13, and in response to this, a re-emission command is output from the microcomputer 13 to the light emission circuit 7 This time, the infrared light pulse for short-distance measurement is emitted from the light emitting unit L ₂ (F-
6).

By the way, there are two cases where PSD5 is not sufficient, one is when subject 4 is at a long distance and PSD5 cannot provide sufficient output, and the other is when subject 4
Is too close and the light-receiving LED image is in a position off PSD5. For the former reason, even if the light emitting part L ₂ emits PS
Although a sufficient output of the D signal cannot be obtained, if the latter is the reason, if the light emitting portion L ₂ emits light, the light-receiving LED image can be detected further inside because it can be detected. This is because the position of the light emitting portion L ₂ is above the light emitting portion L _{1 in} FIG. 2 (a position not on the PSD5 side), and thus the spot image P on the PSD 5 is received at a position closer to the center of the PSD 5. .

The output of the PSD 5 is saturated because the subject 4 is too close and the reflected light thereof becomes strong. At this time, if the light emitting portion L _{2 having a} light emission intensity lower than that of the light emitting portion L ₁ emits light, the subject 4 emits light. The reflected light from will also be weak, and the output of PSD5 will be a value that can be calculated.

Now, the next arithmetic processing circuit 8 in the light-emitting unit L ₂ emission during PSD5
If the output of PSD5 is sufficient, it is judged whether the output of PSD5 is saturated (F-8).
If it is not in the saturated state, the subject distance R is calculated by the output current and read into the microcomputer 13 (F-9).

At this time, the calculated value is based on the calculation formula when light is emitted from the light emitting unit L _1, and therefore needs to be corrected. Therefore, a correction value is set in advance in the correction value circuit 10, and the correction value is set.
It is read into the microcomputer 13 through the A / D conversion circuit 11 and the subject distance R previously obtained is corrected (F-10). This correction may be performed by a known method used in conventional photometry or focus detection.

By the way, if the output of PSD5 is not enough (F-7), or if the output is saturated (F-8), the farthest according to the output of PSD5 within the preset focusing range of the camera. Distance (eg infinity) or closest distance (eg 50c)
Set the subject distance R to (m) (F-11). For example, if the outputs of the PSDs 5 at the time of light emission of the light emitting units L ₁ and L ₂ are not sufficient, the subject distance R is set to the farthest distance because the subject 4 is at a long distance, while the outputs of the PSD 5 are both saturated. At this time, since the subject is at the closest distance, the subject distance R is set to the closest distance.

When the distance measuring operation is completed as described above, the switch S ₂ is pressed when the release button is further pressed down.
Is turned on (F-12), the photographing lens is moved by the lens actuator 12 according to the previously determined subject distance R (F-13), exposure control is performed (F-14), and photographing is finished. To do.

In the above embodiment, the shape of the light emitting portions L ₁ and L ₂ of the LED 6 is the same rectangular shape as shown in FIG. ₂ , but the shape is not limited to this, and as shown in FIGS. 4 (a) to 4 (c), for example. Any shape may be used. In that case, it is desirable that the shape of the light emitting unit is short in the direction of the base line A and long in the direction perpendicular to the base line A in order to reduce the distance measurement error.

Although the light emitting unit L ₁ is used for long distance measurement in the above-described embodiment, both the light emitting units L ₁ and L ₂ emit light for long distance measurement, and then the light emission unit L for short distance measurement. ₂ may be made to emit light. In that case, since the light from the light emitting unit L ₂ is also added as the light for long-distance measurement, the position of the center of gravity of the spot image on the PSD 5 is displaced, so that it is necessary to correct the subject distance.

In the above embodiment, the light emitting element is provided with two light emitting portions, but the present invention is not limited to this, and more light emitting portions or light receiving elements are used within the range allowed by the space of the camera and the design of the optical system. May be. As a result, it becomes possible to measure a closer distance. Further, in the embodiment, the light emitting circuit is controlled so that the light for long-distance distance measurement is output first and then the light for short-distance distance measurement is output, but the order may be reversed if necessary. .

(Effects of the Invention) As described above, in the present invention, a plurality of light emitting elements are provided at different positions in the base line direction, and the light emitting circuit selectively emits the light emitting elements to measure a long distance and a short distance. It is possible to output light for distance measurement, it is arranged at a position other than the light receiving element side for short distance measurement, and it is configured to use a light emitting element with a smaller emission intensity than that for long distance measurement. Since it is possible to appropriately compensate for the reflected light from the subject at, there is an effect that it is possible to perform distance measurement accurately at a short distance.

Further, according to the present invention, since the light for the short distance measurement is output by the light emitting element other than the light receiving element side, the incident angle of the finder of the reflected light from the subject can be made small, so that the parameter of the finder distance measurement frame can be reduced. The effect that the Lux can be reduced can also be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of a distance measuring device for a camera according to the present invention, FIG. 2 is a front view of an infrared emitting LED, and FIG. 3 is for explaining a distance measuring operation of the device of FIG. FIG. 4, FIG. 4 is another configuration example of the light emitting portion of the infrared LED, FIG. 5 is an explanatory view of the principle of the active distance measuring system, and FIG. 6 is a schematic diagram of PSD. 1 ... Emitter lens, 2 ... Light receiving lens, 3, 6 ... Infrared emitting LED,
5 ... PSD, L ₁ , L ₂ ... Light emitting unit

Claims (1)

[Claims] 1. A plurality of light emitting elements arranged at different positions in a base line direction, and a light receiving element which receives light reflected from the light emitting element and which outputs an electric signal according to a distance to the object. The light-emitting element is selectively caused to emit light, and light for long-distance measurement by light emission of at least the light-emitting element on the light-receiving element side of the light-emitting elements and light having a lower intensity than the light for long-distance measurement and Among the light emitting elements, the light emitting circuit capable of selectively outputting the light for short-distance measurement by the light emission of the light emitting element which is not the light receiving element side, and the distance to the subject based on the electric signal from the light receiving element. An arithmetic circuit for performing an arithmetic operation, a correction circuit for correcting the distance calculated by the arithmetic circuit according to the light emitting element selected by the light emitting circuit, and a light emitting element emitting light selected by the light emitting circuit. When the light-receiving element does not output a predetermined electric signal required for distance measurement, the control circuit controls the operation of the light-emitting circuit so that other different light-emitting elements sequentially emit light. Ranging device.