JPH0356948A - Exposure controller for camera - Google Patents

Abstract

PURPOSE:To always photograph in a focal position even if an object moves by taking into consideration a time lag after which exposure actually starts and controlling release signal on-time so that exposure starts when the object reaches the focal position. CONSTITUTION:The focal point of a photographing lens is set at a desired distance, a switch SWO for catch in focus photography is turned on, and a release SWR is turned on; then, a CPU 15 starts range-finding and metering operations. The CPU 15 determines release signal output time to actually start exposure when the object reaches the focal position, through prescribed arithmetic processing based on the amount of defocus obtained by the range-finding operation, and sets a timer counter 23 to the time. Then, a timer 21 is started; when the time to which the timer counter 23 is set comes '0', a release control part 19 is started to carry out exposure. Thus, photographing (exposure) can be performed in the focal position even if the object moves.

Description

[Detailed description of the invention] “Technical field J The present invention relates to an exposure control device for a camera.

``Prior art and its problems'' In recent years, cameras equipped with automatic focusing devices have become mainstream. This type of automatic focusing device usually includes a distance measuring device and a focusing lens drive device that moves the focusing lens to a focusing position. The distance measuring device measures the desired subject distance, and the focusing lens drive device moves the focusing lens to a position where the subject at that subject distance is in focus based on the measured distance data. In addition, there are so-called focus-priority autofocus devices that do not release the camera until the camera is in focus, and are capable of shooting with a stand-alone bottle. Focus shooting is when the focusing lens is focused on the desired subject distance, the focusing lens drive device is not activated, and the distance measuring device is activated to measure the distance to the subject. Exposure is performed when it is detected from distance measurement data that the subject is in focus.

However, in conventional bin photography, the exposure operation begins only after detecting that the distance measurement data of the distance measuring device matches the focusing distance of the focusing lens. It will be exposed after it passes. In other words, there is a problem in that a subject approaching the camera is placed in the rear bin, and a subject moving away from the camera is placed in the front bin.

For example, as shown in Figure 2, when time is plotted on the horizontal axis and distance measurement data (defocus amount) from a rangefinder is plotted on the vertical axis, the movement of a subject approaching the camera is measured along the defocus line. Suppose it is along D. The distance measuring device of this embodiment has a configuration in which an aerial image of a subject is divided into two parts and the images are formed on a CCD line sensor, and the amount of defocus is determined by detecting the distance between the pair of images to perform focus detection. . Strictly speaking, the object distance is not determined; however, in this specification, such a focus detection device is collectively referred to as a distance measuring device.

The distance measuring device repeatedly measures distance at predetermined time intervals. In this distance measurement, for example, when distance measurement is started at time al, the defocus amount di at time al is the time required for integration and l-calculation (hereinafter this time will be referred to as "distance measurement time lag x, J"). Similarly, defocus!d2 at time a2 is obtained after distance measurement time lag x1 time has elapsed.In other words, from the start of distance measurement until distance measurement data is obtained, the distance measurement time lag has passed.

Therefore, the defocus amount of the subject is 0, that is,
Assuming that the defocus amount becomes O during distance measurement at time C when the subject reaches the in-focus position, this will be detected after distance measurement time lag x1 hours have elapsed from time C.

Moreover, if the release signal is output after detecting that the defocus amount has become O, the mirror will be raised after the release signal is output, and the front curtain of the shutter will start running after this mirror-up is completed. Therefore, a predetermined time (hereinafter referred to as "release time lag x.J") is required before exposure actually starts. In other words,
In conventional bottle photography, the actual exposure starts after X (x + + Xi) time has elapsed from the time the subject came to the in-focus position. Therefore, with conventional bottle photography, a moving subject is photographed after passing the in-focus position, resulting in an out-of-focus photograph.

``Object of the Invention'' The present invention has been made in view of the above-mentioned problems of conventional cameras capable of photographing a bottle.
It is an object of the present invention to provide an exposure control device that allows photographing (exposure) to be performed at a focused position even for a moving subject.

"Summary of the Invention" The present invention achieves the above object by providing a distance measuring means for continuously measuring the distance to a subject, a photographic lens capable of setting the focus to an arbitrary subject distance, and a distance measuring means obtained by the distance measuring means. a focusing time prediction means for predicting the focusing time when the subject reaches the focus position set by the photographing lens based on the data; and a shutter release device for the exposure device so that the exposure is performed at the time predicted by the focusing time prediction means. The present invention is characterized in that it includes a control means for outputting a signal.

According to the exposure device having this configuration, in so-called stand-alone photography, the distance to the subject is repeatedly measured, the time when the subject will reach the in-focus position is predicted from changes in the distance measurement data, and the time when the subject will actually reach the in-focus position is predicted. A release signal is output to start the exposure, so even if the subject is moving,
Exposure can be performed at the in-focus position.

“Embodiments of the invention” The present invention will be explained below based on illustrated embodiments.

FIG. 1 is a block diagram showing the configuration of a control system of a single-lens reflex camera to which the exposure control device of the present invention is applied. The distance measurement sensor 11 is a known so-called phase difference detection type distance measurement sensor, and includes a CCD image sensor (not shown) consisting of a large number of photoelectric conversion elements arranged in a row. On the CCD image sensor of this distance measurement sensor 11, an aerial image of the subject within the distance measurement zone that has passed through the photographing lens is divided into two and formed. The amount of defocus is determined by determining the phase difference, that is, the interval between these two divided images.

Control of the integration time of the distance measurement sensor 11, reading of the integral signal (pixel data), etc. are controlled by the distance measurement sensor control section 13. From the distance measurement sensor l1 to the distance measurement sensor control unit 1
The integral signal read out by CPU15 is outputted to CPU15.

The CPU 15 executes a predetermined predictor 1 calculation based on the integral signal input from the ranging sensor control unit 13 to obtain the defocus amount. And in normal AF shooting,
Based on this defocus amount, the focusing lens is moved to the focusing position via a focusing lens driving device (not shown).

Note that the above distance measuring sensor 11. The distance measuring sensor control section 13 and the CPLl 15 constitute a distance measuring means.

The CPU15 includes a photometric circuit 17. Release control unit l9,
A timer 21 and a timer counter 23 are connected,
Further, a switch SWO is input to start photographing the placed bottle.

The photometric circuit 17 receives the output of the light receiving element 25 manually, and the light receiving element 25 outputs a photometric signal corresponding to the subject brightness to the photometric circuit 17. The photometric circuit 17 logarithmically compresses and A/D converts this photometric signal, and outputs the CP as a luminance signal.
Output to U15.

The CPLI 5 executes photometric calculations based on the brightness signal and exposure information such as film sensitivity Sv information, and calculates the shutter speed Tv and aperture value AV. Then, when the release switch SWR is ONL, a release signal is sent to the release control unit l9, and the release magnet RMg
the above shutter speed TV and aperture value Av.
Exposure action is performed based on. The above is the same as normal camera operation. Next, the configuration of the exposure control circuit, which is a feature of the present invention, will be explained.

Connected to the CPtJ L 5 are a timer 2l that provides a reference time during the bottle exposure operation, and a timer counter 23 that counts the time of the timer 2l and outputs a release signal at the predicted time.

When the focus of the photographic lens is set to a desired distance, the bin switch SWO is turned on, and the release SWR is turned on, the CPU 15 starts distance measurement and photometry operations. This distance measurement and photometry operation is performed when the release switch SWR is ON.
It will be executed repeatedly while it is running.

Based on the amount of defocus obtained from this distance measurement operation, the CPU
15 uses predetermined arithmetic processing to determine the release signal output time for actually starting exposure when the subject reaches the in-focus position, and sets this time in the timer counter 23. Then, the timer 2l is started and the timer 21 waits for the time set in the timer counter 23 to reach 0.

When the time set in the timer counter 23 reaches 0, a release signal is output from the timer counter 23 to the CPU INTI 5, and the CPtJ 15, which receives this REI nose signal, controls the release control unit 19 as described above.
Start up and perform exposure.

Next, the bottle photographing operation, which is a feature of the present invention, will be explained with reference to the flowcharts of the bottle photographing operation shown in FIGS. 3A and 3B.

First, the photographer sets the camera to a predetermined composition, focuses on a predetermined distance, and turns the bin switch SWO to O.
n, then turn on the release switch SWR. This flowchart is entered by turning on the release switch SWR.

First, it is checked whether the bin switch SWO is ON or not (S51). If it is Kano F, it is not a bottle shooting, so proceed to the normal mode flowchart and press O.
If it is N, it is a set bottle photograph, so the process advances to S53.

In S53, the release time lag X, which is unique to this camera, is set to X. Furthermore, this release time lag refers to the time after the release signal is output, when the front curtain of the shutter actually starts running and the exposure begins. This is the time until. Release time lag

Next, the distance measuring operation is started. In other words, the range sensor 1l starts integration, and the integrated data is transferred to the range sensor controller 13.
The amount of defocus is determined based on the integral data. Then, this defocus amount is d. The time at which the defocus amount was obtained, that is, the reference time at the start of distance measurement, is read from the timer 2l and set to ai+ (S55).

Check again whether the storage bin switch SWO is ON. If it is OFF, proceed to the flowchart for normal shooting mode, and if it is ON, it is shooting in a storage bin, so S
Proceed to step 59.

In S59, the contents of the previously determined defocus amount d8 and reference time all are set to dk-1 and a5, respectively.
Move to -1. Then, the distance measurement operation is performed again to obtain a new defocus amount and reference time, and the day focus amount is determined by d. 1) Enter the reference time into ak (S61). The above two sets of data (ak--1-+ and a1l,d
Based on m), the time required for focusing (C-a-) is
It is calculated using the following formula (S63). Note that C is the predicted in-focus time at which the defocus amount becomes 0 (see FIG. 2).

Once we know the time C when the defocus amount becomes 0, next,
The time t at which the release signal is issued is determined by the following formula (S
65).

t = c − a 1l− X − =−
(2) Note that X is a time lag unique to this camera, and is the sum of the photometry time X+ and the release time lag x.

When the time t at which the release signal is turned ON is determined, this time t is set in the timer counter 23, and an interrupt by the input port INTI is enabled, and the process returns to S57 (S57).
67).

Then, repeat the loop processing of S57 to S67,
The time t at which the release signal is output is updated each time.

On the other hand, the timer counter 23 counts the output time of the timer 2l and waits for the release signal output time t set in S67 to arrive. Then, when time t comes,
Outputs an interrupt signal to the incubator port INTI of CPLI I5.

When an interrupt signal is input to the interrupt port INTI, the CPU 15 interrupts the process currently being executed, turns the release signal ONL, performs the exposure process, and when the exposure process is completed, returns to the interrupted process (S71 , S72)
.

Through the above operations, at time C when the subject reaches the in-focus position,
Actual exposure is performed, and you can obtain a photo with the main subject in focus.

As described above, according to this embodiment, distance measurement is repeatedly performed to determine the defocus amount d and the time a. is calculated, and the predicted focus time C and the release signal output time t corresponding to this predicted focus time C are updated for each distance measurement, so even if the speed of the subject changes, the subject will arrive at the focus position. Sometimes exposure is guaranteed.

In addition, in the explanation of this embodiment, the case where the defocus amount moves from the plus side to the minus side, that is, the subject moves in the direction closer to the camera, but the subject may also move in the direction away from the camera. be. Therefore, by transforming the formula (2) as shown in the following formula (2), both cases can be handled.

Although the present invention has been described above based on the embodiment shown in the accompanying drawings, the present invention is not limited to this embodiment.

In addition, since this embodiment can detect the amount of change in the amount of defocus, taking this amount of change into consideration, for example, for a subject that moves quickly and has a large amount of change, a fast shutter speed is selected to prevent image blurring. It is also possible to obtain a configuration in which fewer photographs are obtained.

"Effects of the Invention" As is clear from the above explanation, the camera exposure device of the present invention can predict the time when the in-focus position will be reached from changes in measured subject distance data, and Taking into account the time lag from when the release signal that starts the operation is turned ON until the actual exposure starts, the time to turn the release signal ON so that the actual exposure starts when the subject reaches the in-focus position. , so even if the subject is moving, it can always be photographed at the in-focus position.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the circuit configuration of an embodiment of a single-lens reflex camera to which the exposure device of the present invention is applied, and FIG. 2 is a block diagram showing the exposure operation in the exposure control device of the present invention when shooting with a fixed bottle. The graph and FIGS. 3A and 3B are operation flowcharts showing one embodiment of the sequential operation of placing bottle photography according to the present invention. 11... Distance sensor, 13... Distance sensor control unit,
l5...CPLI, 19...Release control section. 21
...Quima, 23...Timer counter.

Claims (2)

[Claims] (1) A distance measuring device that continuously measures the distance to a subject, a photographic lens that can set the focus to an arbitrary subject distance, and a photographic lens that sets the subject using the distance measurement data obtained by the distance measuring device. a focus time predicting means for predicting a time when the focus will reach the set focus position; and a control means for outputting a release signal to the exposure device so that exposure is performed at the time predicted by the focus time predicting means. A camera exposure control device characterized by: (2) In claim 1, the distance measuring means includes a focus detection device that calculates a defocus amount from a phase difference between a pair of subject images that are split into two and formed by passing through a photographic lens, and predicting a focus time. An exposure control device for a camera, characterized in that the means determines a focusing time from the amount of change in a plurality of defocus amounts obtained by the focus detection device.