JP3344191B2 - 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 distance measuring device for a camera having a photographing lens having a variable focal length and a finder optical system having a variable field magnification in conjunction with the focal length of the photographing lens. More particularly, the present invention relates to a camera distance measuring apparatus suitable for a passive triangulation method in which a finder optical system and an autofocus optical system have different optical axes.

[0002]

2. Description of the Related Art Conventionally, as a distance measuring device for a camera, a device using a passive triangular distance measuring method using external light is known. This type of distance measuring apparatus has an auto-focus optical system, receives a captured subject image with a pair of line sensors, and performs a correlation operation on pixel data obtained by each of them to obtain distance measuring data. This autofocus optical system is generally provided on an optical axis different from the photographing optical system and the finder optical system. In such a camera, when the focal length of the photographing lens is changed, the distance measuring frame in the viewfinder and the actual distance measuring area are shifted, and a subject not intended by the photographer is focused. was there.

In view of the above, a camera has been proposed in which a distance measurement operation is performed using only pixel data corresponding to a distance measurement frame in an actual distance measurement area in accordance with a change in a focal length (Japanese Patent Laid-Open No. 2-293833). ). Further, there is disclosed a distance measuring device which calculates a distance to a subject by quantizing a subject image received by a line sensor by a time difference from the accumulation time using a charge accumulation time of the brightest pixel as a quantization reference and calculating the distance to the subject. This is proposed by Japanese Patent Application Laid-Open No. Sho 59-204704.

[0004]

However, when such a distance measuring device is used in the above-described camera and distance measurement is performed on the telephoto side, as shown in FIG. For a person), if there is a very high-luminance light source (light) outside the ranging frame, quantization is performed based on the accumulation time of the pixels in the light source unit, so that the main subject portion in the ranging frame is quantized. There is a problem in that sufficient contrast cannot be obtained from the pixel data, so that the distance to the main subject in the distance measurement frame cannot be calculated.

An object of the present invention is to provide a main subject (person) in a distance measurement frame as described above even when a very bright light source (light) is present outside the distance measurement frame. To provide a camera distance measuring device capable of calculating a distance to the camera.

[0006]

In order to achieve the above object, a distance measuring apparatus for a camera according to the present invention selects a pixel range which can be used as a quantization reference in accordance with a change in the focal length of a photographing lens, and performs a quantization. Pixel range and distance measurement
It is characterized in that the range of pixels used is different . According to the configuration of the present invention, a pixel range that can serve as a quantization reference is selected in accordance with a change in the focal length of the photographing lens, so that a high-luminance object such as a point light source is located in the ranging area outside the ranging frame. Even if it exists, it is possible to obtain pixel data having a sufficient contrast in the main subject portion in the ranging frame as shown in FIG.

[0007]

FIG. 1 is a diagram showing an optical system of a camera to which a distance measuring apparatus according to the present invention is applied. A camera body 1 has a variable focal length shooting lens 2 and a viewfinder 3.
A distance measuring unit 4 for performing distance measurement is provided. The focal length of the photographing lens 2 is 35 mm and 70 m
m and 105 mm. The finder 3 is a real image type zoom finder, and forms an object image on an image plane 8 by an objective lens 9 and observes the image by an eyepiece 7. The objective lens 9 is linked to the photographing lens 2, and the focal length is changed according to the focal length of the photographing lens 2. On the image plane 8, a distance measurement frame (fixed) is drawn. The distance measuring unit 4 includes a pair of line sensors 5 and an AF lens 6 for forming a subject image on the line sensors 5. The focal length of the AF lens 6 is constant regardless of the focal length of the photographing lens.

When the focal length of the photographing lens 2 is changed, the size of the subject image is changed by the objective lens 9 of the finder, but the focal length of the focusing frame and the AF lens 6 is not changed. A shift (parallax due to a change in focal length) occurs between the distance frame and the area actually measured. The camera according to the present embodiment is configured so that the distance measurement frame and the distance measurement area coincide with each other when the focal length of the photographing lens is 35 mm. Therefore, if the focal length of the taking lens is changed to 70 mm or 105 mm, the distance measurement area becomes wider than the distance measurement frame. Further, since the viewfinder 2 and the distance measuring unit 3 are arranged with a distance in the left-right direction of the camera, even when the subject distance is short, the distance between the distance measuring frame and the actual distance measuring area (subject distance change). Parallax).

FIG. 2 is a block diagram of a distance measuring apparatus according to the present invention. The line sensor 11 is composed of 100 pixels. Each pixel includes a light receiving unit and a storage unit. Here, for simplicity, only one of the pair of line sensors is shown.

FIG. 3 shows the configuration of the light receiving section and the storage section. The current generated by the light hitting the light receiving section 21 is stored in the capacitor 22. Then, when the voltage of the capacitor 22 reaches a predetermined voltage VREF, a latch signal is output. The capacitor 22 is reset by reset means (not shown) before the start of charge accumulation for distance measurement, and charge accumulation starts from 0V.

The latch detector 13 is provided for each pixel, and receives the latch signal output from each pixel.
If the quantization reference is selected by the microcomputer 12, a latch detection signal is output. The counter 14 is connected to the latch detection unit 13 and starts accumulating charges for distance measurement.
The counting is started by the latch detection signal generated first. The counter 14 is set to 0 at the start of charge accumulation. The counting is performed by counting up the pulse output from the clock generator 15. The latch unit 16 is provided for each pixel, and when a latch signal from each pixel is input, the count value of the counter 14 is input and latched. The microcomputer 12 receives the focal length data of the photographing lens from the focal length detector 17 and performs quantization reference selection based on the input focal length data. The detection of the focal length of the photographing lens is performed by an encoder provided in a lens barrel or the like of the lens.

Next, the operation of the distance measuring device will be briefly described. When the microcomputer 12 instructs the start of charge accumulation for distance measurement by a signal (not shown), the line sensor 1
Each of the pixels 1 (S0 to S99) simultaneously starts charge accumulation. When the voltage of the capacitor of the pixel SX to which the strongest light (the brightest pixel) SX reaches the predetermined voltage VREF,
A latch signal is output. At this time, if the quantization reference is selected by the microcomputer 12 for the pixel SX,
The latch detector X corresponding to the pixel SX outputs a latch detection signal. Then, the counter 14 starts counting. When the latch unit X receives the latch signal, it inputs and latches the count value of the counter 14. Therefore, the data of the latch unit corresponding to the brightest pixel becomes 0.

Then, after a lapse of time corresponding to the intensity of the light received by each of the other pixels, a latch signal is input. The latch section corresponding to each pixel latches the value of the counter 14 at the time of input of the latch signal. Therefore, data corresponding to the time until each pixel outputs the latch signal is latched in the latch unit corresponding to each pixel with reference to the time when the brightest pixel outputs the latch signal. The microcomputer 12 sets the latch units 0 to 99 after the end of the charge accumulation.
By reading the latch data, the data of each pixel can be obtained.

The latch detectors 13 are connected to the microcomputer 12, respectively. When the quantization reference selection signal is not input, the latch detection signal is not output even if the latch signal is input. Therefore, the data of a pixel whose quantization reference is not selected, which is brighter than the brightest pixel among the quantization reference, is counted by the counter 1 before the counter 14 starts counting.
Since the data of No. 4 is latched, all become "0".

FIG. 4 is a flowchart showing the operation of the camera distance measuring apparatus according to the present invention at the time of distance measurement. At the start of ranging,
First, the focal length of the taking lens is input (# 100). Then, a pixel for quantization reference selection is selected according to the focal length of the photographing lens (# 110 to # 150), and charge is accumulated (# 160). Then, the sensor data of all the pixels is read (# 170), and A is obtained by the read data.
The F calculation is performed (# 180), and the distance measurement operation ends.

FIG. 5 is a diagram showing the relationship between the focal length of the photographing lens of the camera distance measuring apparatus according to the present invention and the pixel of the line sensor selected as the quantization reference. When the focal length of the taking lens is 35 mm (shortest),
The width of the ranging frame and the range of the subject projected on the line sensor are configured to match. When the focal length of the taking lens is changed as described above, the range of the subject projected on the line sensor becomes wider than that of the distance measurement frame. Focal length 35mm, 70mm, 10
The pixel range of the line sensor corresponding to the distance measurement frame at the time of 5 mm is the range indicated by the arrow in the figure, and the pixels in the range are selected when the quantization reference is selected.

FIG. 6 is a flowchart of a modified example of the operation at the time of distance measurement by the camera distance measurement apparatus according to the present invention. First, similarly to the above-described operation, the focal length of the photographing lens is input (# 20).
0), quantization reference pixel selection (# 210), and (pre) distance measurement (# 220). Then, the pixel range for selecting the quantization reference is shifted according to the distance measurement result (# 230), and the (main) distance measurement is performed again. This enables accurate distance measurement for a subject in the distance measurement frame.

FIG. 7 shows the relationship between the distance measurement result based on the pre-range measurement result and the shift of the pixel range for selecting the quantization reference. For simplicity, the description will be made only when the focal length of the taking lens is 35 mm. As described above, in the camera according to the present embodiment, even when the subject distance is short, a deviation occurs between the ranging frame and the ranging area. In the camera distance measuring apparatus according to the present embodiment, the shift amount is about 10 pixels when the object distance is 3 m and about 20 pixels when the object distance is 1 m. The distance measuring device previously stores the relationship between the subject distance and the shift amount, and shifts the pixel range for selecting the quantization reference according to the result of the pre-ranging. Other focal lengths (70
mm, 105 mm).

In this embodiment, the quantization reference selection control can be performed for each pixel unit of the line sensor. However, the quantization reference selection can be performed for a plurality of pixels as one unit. Is also good. This makes it possible to reduce the number of signal lines for the quantization reference selection signal.

In this embodiment, the description has been given of the case where the focal length of the photographing lens can be switched between three types. However, it is needless to say that the present invention is applicable to a zoom lens whose focal length changes continuously. .

[0021]

As described above, the present invention changes the pixel range for quantization reference selection according to the distance measurement frame during charge accumulation for distance measurement, thereby enabling high-luminance objects outside the distance measurement frame. It is possible to solve the above-mentioned problem.

[Brief description of the drawings]

FIG. 1 is a diagram showing an optical system of a camera to which a distance measuring apparatus according to the present invention is applied.

FIG. 2 is a block diagram of a distance measuring apparatus according to the present invention.

FIG. 3 is a diagram showing a configuration of a light receiving unit and a storage unit of the distance measuring apparatus of the present invention.

FIG. 4 is a flowchart showing an operation of the distance measuring device of the present invention at the time of distance measurement.

FIG. 5 is a diagram showing a relationship between a focal length of a photographing lens of a camera to which the distance measuring apparatus of the present invention is applied and a pixel of a line sensor selected as a quantization reference.

FIG. 6 is a flowchart of a modified example of the operation at the time of distance measurement of the distance measuring apparatus of the present invention.

FIG. 7 is a diagram showing a relationship between a distance measurement result based on a pre-range measurement result of the distance measurement apparatus of the present invention and a shift amount of a pixel range for selecting a quantization reference.

FIG. 8 is a diagram showing a relationship between a finder image of a camera to which the distance measuring apparatus of the present invention is applied and a sensor output.

FIG. 9 is a diagram showing a relationship between a finder image of a camera to which a conventional distance measuring device is applied and a sensor output.

[Explanation of symbols]

 2 photographing lens 3 finder 4 distance measuring unit 5 line sensor 12 microcomputer 13 latch detection unit 16 latch unit S0 to S99 pixels

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G02B ^7/ 28-7/40 G03B 13/36 G03B 17/20

Claims (1)

(57) [Claims] 1. A distance measuring device using a pair of line sensors for generating a video signal based on a charge accumulation completion time of a brightest pixel as a quantization reference, wherein the distance is measured by the line sensor according to a focal length of a photographing lens. In a camera ranging apparatus in which the relationship between a possible ranging area and a ranging frame in a viewfinder changes, each pixel of the line sensor can be used as a quantization reference.
Selecting means for selecting whether to be included in the range or not, and performing selection control for selecting a pixel range that can be the quantization reference according to the focal length of the photographing lens, and using the pixel range that can be the quantization reference and distance measurement Pixel
A camera ranging device having a different range.