JPH07119880B2 - Autofocus camera - Google Patents

Description

TECHNICAL FIELD The present invention relates to an autofocus camera.

(Prior Art) A still camera with a built-in automatic focus adjustment device executes a focusing operation when the release button is pressed to the first stage, and when the photographer determines the composition of the viewfinder and further presses it, the shutter mechanism is activated. A so-called focus lock that operates to perform an exposure operation is possible, but since it takes some time from the end of the focusing operation to the exposure operation, it is moved particularly in the optical axis direction. When photographing a subject, there is a problem that the focal point of the photographing lens deviates.

(Object) The present invention has been made in view of such a problem, and an object of the present invention is to provide an automatic focusing camera capable of maintaining a focused state regardless of the motion of a subject. Is.

(Summary of the Invention) That is, a feature of the present invention is that a first switch that operates by a first depression of a release button and a second switch that operates after the first depression of the release button operate. And a distance measuring means for outputting at least two or more distance data at a desired time interval when the first switch operates, and the distance measuring means when the second switch operates. Focus control means for controlling the focus of the photographing lens based on the output of the distance measuring means and the time from the start of the operation of the distance measuring means to the operation of the second switch, and the time when the focus control of the photographing lens is completed And an exposing means for starting the exposing operation from the above.

(Example) Therefore, the details of the present invention will be described below based on an illustrated example.

FIG. 1 shows an embodiment of the present invention, in which reference numeral 1 is a distance measuring optical system, which is a light emitting element driving circuit 2 which intermittently emits light and a reflection from a subject S. A light receiving element 1b for receiving light is provided, and one of them is configured to relatively scan in the optical axis direction in synchronization with the photographing lens driving mechanism 11 and output a scanning position signal. 3 is a distance measuring mechanism drive circuit, which is used when the release button is pushed to the first stage,
With the sampling period ΔT defined in the timer circuit 5,
The distance measuring mechanism 1 is configured to perform the distance measuring operation at least three times. Reference numeral 4 is a distance calculation circuit, and the distance measuring mechanism 1
The scanning position signal and the signal from the light receiving element 1b are received, and the distance to the subject S is calculated based on the scanning position when the in-focus state is reached. 5 is the aforementioned timer circuit,
A clock CK1 for intermittently driving the light emitting element 1a, a sampling clock CK for determining the distance data sampling period ΔT
2, and outputs a time clock CK3 for measuring the time t from the end of distance measurement to the time of exposure. Reference numeral 6 denotes a distance data storage circuit for sequentially storing the data output from the distance calculation circuit 4 and outputting the data in response to a read signal from a function calculation circuit 7 described later. Reference numeral 7 denotes the above-described function operation circuit, which is a stage where at least three distance data are stored in the distance data storage circuit 6, and a change tendency, that is, a first-order change or a second-order change, from the deviation between the time interval ΔT and each distance data. And a quadratic function deciding circuit 7c for calculating a function on which the distance data 1, 2, 3 ... Are multiplied based on the decision result. There is. The order determination circuit 7a determines a method using Chebyshev's orthogonal polynomial or a method of determining a difference in distance change, and a method of determining a linear expression if this is constant, or a quadratic expression if it changes, etc. You can The linear function determining circuit 7b uses the least squares method, the central point method, or the series method, and the quadratic function determining circuit 7c uses the least squares method, the geometric series method, or the like. Reference numeral 8 denotes a distance prediction calculation circuit, which is the time t from the time when the final distance measurement operation is performed to the start of the exposure process, and the distance function F determined by the function calculation circuit 7.
The distance value t is output based on (T). 9
Is a control circuit that controls the operation of the entire device.
The signals from the switches SW1 and SW2 that operate when the 10 is pushed to the 1st and 2nd steps are input, and the distance measurement operation command is given by the signal from the switch SW1 and the distance is given by the signal from the switch SW2. The predictive calculation circuit 8 is operated to obtain the distance value t, the photographing lens drive mechanism 11 is operated so as to match the distance value t, and the shutter mechanism 13 is operated corresponding to the data from the photometry circuit 12 at the time of focusing. Is configured to operate. In the figure, reference numeral 14 denotes a light receiving element for detecting subject brightness, and 15 denotes a strobe circuit. The switch SW1 constitutes the first switch,
The switch SW2 constitutes a second switch, the distance measuring mechanism 1 and the distance calculating circuit 4 constitute a distance measuring means, the distance predicting calculating circuit 8 constitutes a focus controlling means, and the shutter mechanism 13 constitutes an exposing means. To do.

Next, the operation of the apparatus thus configured will be described based on the flow chart shown in FIG.

Point the camera at a moving subject such as a car and release the button.
When 10 is pushed down to the first stage, light is emitted from the light emitting element 1a to the subject S, and at the same time, the scanning position of the light receiving element 1b is changed in conjunction with the taking lens driving mechanism 11. When the focus state is achieved in this way, the distance calculation circuit 4 calculates the distance 1 to the subject S based on the scanning position (note that the elapsed time t is the calculation time or the lens drive time). More accurate focusing can be done by adding such items.). The distance data 1 is stored in the distance data storage circuit 6. When the first distance measurement is completed, the distance measurement operation is performed again to detect the distance 2 after the time ΔT has elapsed, and the distance data 2 is stored in the distance data storage circuit 6.

A constant time interval ΔT so as to follow the movement of the subject S
At the stage where at least three distance data are stored in the distance data storage circuit 6, the order determination circuit 7a of the function operation circuit 7 receives the distance data 1, 2, 3 ... 3 ... and the time difference ΔT, the order suitable for expressing the motion of the subject S, that is, a linear function or 2
Determine if it is the next function. If the determination result is a linear expression, the distance data is sent to the linear function determining circuit 7b, and if it is a quadratic expression, the distance data is sent to the quadratic function determining circuit 7c.
Is output, and the distance function F (T) on which these distance data are accurately applied is calculated (FIG. 3, a, b).

When the release button 10 is pressed to the second stage when the composition is determined, the distance prediction calculation circuit 8 detects the elapsed time from the distance measurement start time based on the time clock from the timer circuit 5, and uses this as the distance function. The distance value t to the subject S is calculated by substituting it into F (T). The control circuit 9 uses this distance value t
In response to this, the photographing lens drive mechanism 11 is operated to adjust the photographing lens so as to focus on the distance value t, and then exposure is performed in accordance with the distance measurement data. As a result, shooting is performed in a state in which the distance correction is performed by following the distance traveled by the subject during the time t from distance measurement to exposure.

Further, when flash photography is required, the flashmatic operation is executed by determining the light emission timing based on the distance value t from the distance prediction calculation circuit 8 to obtain the optimum exposure regardless of the movement of the subject S. If possible.

Needless to say, when shooting a still subject, the shooting operation may be started without performing the distance prediction operation.

In this embodiment, the distance measuring mechanism is driven in conjunction with the photographing lens driving mechanism 11, but even if each of them is driven independently, a distance measuring mechanism using an optical position sensor is further used. Even if you do not drive
It is clear that the same effect is achieved.

Further, in this embodiment, the distance data is temporarily stored, but if the calculation is executed every time the distance data is obtained, the data storage circuit can be eliminated.

In addition, in this embodiment, the active system using the principle of triangulation has been described as an example, but a passive system electronic auto that detects a change in spatial frequency by detecting a reflected light image from a subject image. If applied to focus, the distance measurement time can be extremely shortened.

Further, in this embodiment, the distance function is determined by a linear expression and a quadratic expression, but a higher-order expression of a third order or higher can be used, and the distance function can be approximated by a linear expression. In some cases, it is clear that the focus processing can be adjusted when the two distance data are collected.

Further, in the above-described embodiment, the distance function is calculated from the distance data and the subject distance at the time of exposure is predicted based on the distance function. However, the distance change amount for each distance measurement time interval ΔT is kept until the time of exposure. By adding, the subject distance at the time of exposure can be obtained without calculating the distance function.

(Effect) As described above, according to the present invention, an unspecified length from the first depression to the second depression of the release button, that is, the photographer determines the composition in the focus lock state. It is possible to focus on a subject that is moving within the time, and it is possible to obtain a high-quality image and enlarge the shooting target. Then, since the photographing lens is not driven from the end of the distance measurement to the start of the shutter operation, power saving can be achieved.

[Brief description of drawings]

FIG. 1 is a block diagram of an apparatus showing an embodiment of the present invention, FIG. 2 is a flow chart showing the operation of the same apparatus, and FIG. 3 is an explanatory diagram showing a movement tendency of a subject. Switch SW1 ... first switch, 8 ... focus control means Switch SW2 ... second switch, 13 ... exposure means 1, 4 ... distance measuring means

Claims (1)

[Claims] 1. A first switch operated by a first depression of a release button, a second switch operated by a second depression of the release button after the first depression, and the first switch. Distance measuring means for outputting at least two or more distance data at a desired time interval when the switch is operated, and output of the distance measuring means and operation of the distance measuring means when the second switch is operated. A focus control unit that controls the focus of the photographing lens based on the time from the start to the actuation of the second switch, and an exposure unit that starts the exposure operation when the focus control of the photographing lens is completed. An autofocus camera that is characterized by that.