JP2007027830A - Electronic camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To shorten focusing time. <P>SOLUTION: An electronic camera comprises a first photometry means for performing photometry to an object based on a signal output from a first image pickup means; and a second photometry means for performing photometry to the object based on a signal output from a second image pickup means provided apart from the first one. In AF activation, the image pickup conditions of a first photometry in the first photometry means are determined based on the photometry results of the second photometry means. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electronic camera equipped with a hybrid AF (Auto-Forcus) device.

  “Mountain climbing method” where a subject image is picked up by an image sensor while moving the photographic lens, a focus evaluation value is calculated from the contrast of the image signal output from the image sensor, and a focus position where the focus evaluation value is maximized is detected. A focus detection device, and a distance measuring device that detects the shooting distance to the subject by the principle of triangulation using a distance measuring sensor that is different from the imaging sensor, and the focus detection result by the focus detection device and the distance measurement by the distance measuring device. An electronic camera equipped with a hybrid AF device that adjusts the focus of a photographic lens based on the result is known (see, for example, Patent Document 1).

Prior art documents related to the invention of this application include the following.
JP 2004-247773 A

  However, in the conventional hybrid AF type electronic camera described above, the focus position of the imaging lens is detected by detecting the in-focus position where the contrast of the imaging signal output from the imaging sensor is maximized. Unless a stable convergence state is obtained, accurate contrast cannot be obtained, and focus adjustment cannot be started. Therefore, there is a problem that it takes time to focus when turning on the power, returning from the power saving mode, or switching from the playback mode to the shooting mode.

(1) The invention of claim 1 is provided with a first imaging unit that captures an image of a subject that has passed through the photographing optical system, and a second imaging unit that is provided separately from the first imaging unit and that captures an image of the subject. First detection means for detecting a focused state with respect to the subject based on a signal output from the first imaging means, and second detection means for detecting a focused state with respect to the subject based on a signal output from the second imaging means And a focus adjusting unit for adjusting the focus of the photographing optical system based on the detection result by the first detecting unit and the detection result by the second detecting unit, and subject photometry based on the signal output from the first imaging unit. First photometry means to be performed, second photometry means for photometry of a subject based on a signal output from the second imaging means, and second photometry means as a start-up process of the focus adjustment means. Photometric results of 2 photometric means And control means for determining the imaging conditions for the first photometry in the first photometry means.
(2) In the electronic camera according to the second aspect, the initialization of the second imaging unit is started by the control unit prior to the initialization of the first imaging unit.
(3) The electronic camera according to claim 3 further includes a second optical system different from the photographing optical system, and an image of the subject that has passed through the second optical system is captured by the second imaging unit. is there. (4) The focus adjustment means of the electronic camera according to claim 4 is activated in response to power-on of the electronic camera.
(5) The electronic camera of the electronic camera according to claim 5 has a photographing mode for photographing an image and a power saving mode for suppressing power consumption in the electronic camera, and the focus adjustment unit starts the photographing from the power saving mode. Start in response to transition to mode.
(6) The electronic camera according to claim 6 has a photographing mode for photographing an image and a non-photographing mode for performing an operation other than photographing, and the focus adjusting unit is adapted to change from the non-photographing mode to the photographing mode. to start.
(7) The electronic camera according to claim 7 is an image sensor that outputs the subject image captured by the first imaging unit as an image signal, and detects the subject distance based on the subject image captured by the second imaging unit. It is an element.

  According to the present invention, it is possible to shorten the focusing time at the time of AF activation.

  FIG. 1 is a diagram showing a configuration of an embodiment. An electronic camera according to an embodiment includes an imaging lens 2, an aperture 3, an imaging sensor 4, a sensor control circuit 5, an AD conversion circuit 6, a first distance measuring circuit 7, a second distance measuring sensor 8, and a second distance measuring circuit 9. , An AF control circuit 10, an AF motor 11, a focus control mechanism 12, a first photometry circuit 13, a second photometry circuit 14, an AE control circuit 15, an image recording circuit 16, and the like.

  The photographing lens 2 is driven by an AF motor 11 and a focus control mechanism 12 to perform focus adjustment. The imaging lens 2 is not limited to a lens having a fixed focal length, and may be a zoom lens having a variable focal length. The photographing lens 2 guides the light from the subject 1 to the light receiving surface of the image sensor 4 through the diaphragm 3 and forms an image of the subject 1.

  The image sensor 4 is an image sensor such as a CCD, CMOS, or CID in which a large number of pixels are two-dimensionally arranged. The image sensor 4 converts each pixel into a signal charge corresponding to the amount of incident light of the subject image and outputs it as an image signal. The imaging sensor 4 has a so-called electronic shutter function that controls the charge accumulation time (shutter speed) of each pixel by a shutter gate pulse. The imaging signal of the imaging sensor 4 is converted into a digital signal by the AD conversion circuit 6 and recorded in the image recording circuit 16.

  The electronic camera according to one embodiment includes two systems of distance measurement circuits, that is, a first distance measurement circuit 7 and a second distance measurement circuit 9, and two systems of distance measurement circuits, that is, a first photometry circuit 13 and a second photometry circuit 14. ing. The first ranging circuit 7 and the first photometry circuit 13 of the first system perform ranging and photometry using the imaging signal of the imaging sensor 4. On the other hand, the second distance measurement circuit 9 and the second light measurement circuit 14 of the second system perform distance measurement and photometry using the output signal of the second distance measurement sensor 8 provided separately from the imaging sensor 4.

  The first distance measuring circuit 7 calculates a focus evaluation value based on the contrast of the imaging signal output from the imaging sensor 4. As shown in FIG. 2, the focus evaluation value is maximized at the focusing lens position. The first photometry circuit 13 performs photometry based on the imaging signal output from the imaging sensor 4 and calculates subject luminance.

  As shown in FIG. 3, the second distance measuring sensor 8 divides the light from the subject 1 by a pair of lenses L1 and L2 and guides the light to the photoelectric line sensors S1 and S2, and the subject image is formed on each of the sensors S1 and S2. The subject image signal is output from each of the sensors S1 and S2. The second distance measuring circuit 9 detects the shooting distance to the subject 1 based on the principle of triangulation based on the subject image signal output from the second distance sensor 8. The second photometry circuit 14 performs photometry based on the subject image signal output from the second distance measuring sensor 8 and calculates subject luminance.

  Based on the focus evaluation value detected by the first distance measuring circuit 7 and the object distance detected by the second distance measuring circuit 9, the AF control circuit 10 moves the photographic lens 2 to the object distance by the AF motor 11 and the focus control mechanism 12. After moving to a position corresponding to (shooting distance), it moves to a focus position where the focus evaluation value is maximized.

  As shown in FIG. 4, according to the “mountain climbing method” focus adjustment method that drives the photographing lens to the in-focus position where the focus evaluation value detected based on the image pickup signal of the image sensor becomes the maximum, the focus adjustment is performed. First, the photographic lens is driven from close to infinity to search for the maximum focus evaluation value, that is, the in-focus position, and then the photographic lens is driven to the in-focus position. However, since this hill-climbing focus adjustment method requires focusing time, in one embodiment, the focus of the photographic lens is adjusted by hybrid AF. That is, after the photographic lens is driven to a position corresponding to the photographic distance detected by the triangulation method, the photographic lens is driven to the in-focus position by the hill-climbing method.

  The AE control circuit 15 controls the aperture 3 and the sensor control circuit 5 based on the subject brightness detected by the first photometry circuit 13 and the second photometry circuit 14, and the aperture and the imaging are performed so that the subject image has an optimum brightness. The charge accumulation time of the sensor 4 is adjusted.

  FIG. 5 is a timing chart showing the operation of each part when the electronic camera according to the embodiment is activated. In FIG. 5, the initialization operation of the recording circuit which is not directly related to the present invention is omitted. FIG. 5 shows the operation when the power is turned on, but the same operation is performed when returning from the power saving mode and when switching from the playback mode (non-shooting mode) to the shooting mode.

  In FIG. 5, when the power switch of the camera is turned on at time t0, initialization of the taking lens 2 is started. In the initialization of the photographing lens 2, the zoom lens is moved from the retracted position to a predetermined position, and the focusing lens is moved from the origin position to the predetermined position. Generally, it takes 1 to several seconds to initialize the photographic lens.

  Prior to initialization of the imaging sensor 4, initialization of the second distance measuring sensor 8 (S1, S2) is started at time t1 after a predetermined time from turning on the power switch. As described above, the second distance measuring sensor 8 includes two line sensors S1 and S2. Generally, it takes several hundreds of milliseconds to initialize this type of line sensor S1 and S2. In addition, initialization of the image sensor 4 is started at time t2 after a predetermined time from turning on the power switch. As described above, the imaging sensor 4 is a two-dimensional sensor, and it generally takes several hundreds of milliseconds to initialize this type of sensor.

  At the time t3, the initialization of the second distance measuring sensor 8 is completed, and immediately the photometry by the second distance measuring sensor 8 (indicated by symbols E1, E2, E3,...) And distance measurement (F1 in the figure). , F2, F3,... In this embodiment, an example is shown in which photometry and distance measurement are alternately performed by the second distance measuring sensor 8, but only the first photometry is performed twice (E1 and E2). This is because the first photometry E1 has no history so far, so photometry is performed using a preset value for the control amount such as the charge accumulation time, and the second photometry E2 based on the result of the first photometry E1. This is for determining the control amount. Thus, accurate subject brightness can be obtained in the second photometry E2.

  At time t4, the initialization of the taking lens 2 is completed, and the initialization of the shutter and the diaphragm 3 is started immediately. Since the initialization of the image sensor 4 has already been completed at time t5 before the initialization of the shutter and the aperture stop 3 at time t6, photometry using the image signal of the image sensor 4 is possible at time t6. It is. Further, at this time t6, the second photometry E2 by the second distance measuring sensor 8 and the second photometry circuit 14 has already been completed, and an accurate subject brightness is detected.

  Therefore, in the electronic camera of this embodiment, the aperture value and the shutter are based on the second photometric value detected by the second distance measuring sensor 8 and the second photometric circuit 14 at the first photometry by the image sensor 4. Control amounts for photometry of the imaging sensor 4 and the first photometry circuit 13 such as speed (charge accumulation time) and SV value are determined, and the first photometry is performed by the imaging sensor 4 and the first photometry circuit 13.

  Since the control amount for the first photometry of the imaging sensor 4 and the first photometry circuit 13 is determined based on the photometric values detected by the second distance measuring sensor 8 and the second photometry circuit 14, the first photometry by the imaging sensor 4 is performed. Almost accurate photometric values can be obtained. In the second and subsequent metering, a stable metering value is obtained, and the steady state is obtained from the second metering.

  At time t7 when the first photometry by the image sensor 4 and the first photometry circuit 13 ends, distance measurement by the image sensor 4 and the first distance measurement circuit 7 is started.

  FIG. 6 is a timing chart showing the operation of each part when the conventional electronic camera is activated. It should be noted that the difference from the operation at the time of starting the electronic camera of the embodiment shown in FIG. 5 will be mainly described, and the same devices as those used in the electronic camera of the embodiment shown in FIG. The same reference numerals are used for explanation.

  In FIG. 6, during the first photometry (time t <b> 16) by the imaging sensor 4, the second measurement is performed on the control amounts of the imaging sensor 4 and the first photometry circuit 13 such as the aperture value, shutter speed (charge accumulation time), and SV value. The photometry is performed using a preset value without using the photometry results obtained by the distance sensor 8 and the second photometry circuit 14. Therefore, the correct photometric value cannot be obtained by the first photometry of the imaging sensor 4 and the first photometry circuit 13, and a steady state is achieved by the second photometry or the subsequent photometry at the earliest.

  If the photometry by the image sensor 4 and the first photometry circuit 13 does not reach a steady state, an accurate contrast, that is, a focus evaluation value cannot be obtained. Therefore, focus detection by the image sensor 4 and the first distance measurement circuit 7 can be started. Can not.

  That is, the conventional electronic camera does not determine the first photometric control amounts of the image sensor 4 and the first photometric circuit 13 based on the photometric values detected by the second distance measuring sensor 8 and the second photometric circuit 14. , It takes time until the photometry by the image sensor 4 and the first photometry circuit 13 becomes a steady state, when turning on the power, returning from the power saving mode, or switching from the playback mode (non-shooting mode) to the shooting mode. The focusing time becomes longer.

  As described above, according to the embodiment, the imaging sensor 4 that receives the subject light that has passed through the imaging lens 2 and captures the subject image, and the imaging lens 2 based on the imaging signal that is output from the imaging sensor 4. A first distance measurement circuit 7 that performs focus detection; and a second distance measurement circuit 9 that performs distance measurement by receiving subject light that has passed through a pair of lenses L1 and L2 different from the photographing lens 2 by distance measurement sensors S1 and S2. The AF control circuit 10, the AF motor 11 and the focus control mechanism 13 for adjusting the focus of the photographing lens 2 based on the focus detection result by the first distance measurement circuit 7 and the distance measurement result by the second distance measurement circuit 9, and imaging A first photometric circuit 13 that performs photometry based on an imaging signal output from the sensor 4 and a second photometric circuit 14 that performs photometry based on signals output from the distance measuring sensors S1 and S2 are provided. Focus detection by the first distance measuring circuit 7 is started when the photometric result of the path 13 becomes stable, and distance measurement by the second distance measuring circuit 9 is started when the photometric result of the second photometric circuit 13 becomes stable. In the electronic camera that starts the camera, on the basis of the photometry result of the second photometry circuit 14 when the AF is activated, that is, when the camera is turned on, when returning from the power saving mode, or when switching from the non-shooting mode to the shooting mode. The sensor control circuit 5 for determining the control amount (imaging condition) of the first photometry by the image sensor 4 and the first photometry circuit 13 is provided, so that the image is taken when the power is turned on, when returning from the power saving mode, or in the reproduction mode. At the time of switching to the mode, the photometry by the first photometry circuit 13 quickly reaches a steady state, and the focusing time can be shortened.

  Further, according to the embodiment, the initialization of the second distance measuring sensor 8 (S1, S2) is started before the initialization of the imaging sensor 4, so that the second distance measuring sensor is accordingly increased. 8 (S1, S2) and the photometry result by the second photometry circuit 14 can be obtained quickly, and using the photometry result, the photometry of the image sensor 4 and the first photometry circuit 13 will be in a steady state sooner, reducing the focusing time. can do.

It is a figure which shows the structure of one embodiment. It is a figure which shows the change of the focus evaluation value with respect to a lens position. It is a figure explaining external light passive AF. It is a figure explaining the focus adjustment method of a mountain climbing system. It is a timing chart which shows operation of each part of one embodiment. It is a timing chart which shows each part operation | movement of the conventional electronic camera.

Explanation of symbols

2 photographing lens 4 imaging sensor 5 sensor control circuit 7 first distance measuring circuit 8 second distance measuring sensor 9 second distance measuring circuit 10 AF control circuit 11 AF motor 12 focus control mechanism 13 first light measuring circuit 14 second light measuring circuit 15 AE control circuit

Claims (7)

First imaging means for capturing an image of a subject that has passed through the imaging optical system;
A second imaging means provided separately from the first imaging means for capturing an image of the subject;
First detection means for detecting an in-focus state with respect to the subject based on a signal output from the first imaging means;
Second detection means for detecting an in-focus state with respect to the subject based on a signal output from the second imaging means;
Focus adjusting means for adjusting the focus of the photographing optical system based on the detection result by the first detection means and the detection result by the second detection means;
First photometry means for measuring the subject based on a signal output from the first imaging means;
Second photometric means for measuring the subject based on a signal output from the second imaging means;
Control processing for performing photometry by the second photometry means and determining imaging conditions for initial photometry by the first photometry means based on the photometry result of the second photometry means is provided as startup processing of the focus adjustment means. An electronic camera characterized by that. The electronic camera according to claim 1,
The electronic camera according to claim 1, wherein the control unit starts initialization of the second imaging unit prior to initialization of the first imaging unit. The electronic camera according to claim 1,
A second optical system different from the photographing optical system;
The electronic camera characterized in that the second imaging means captures an image of the subject that has passed through the second optical system. The electronic camera according to claim 1,
The electronic camera according to claim 1, wherein the focus adjustment unit is activated in response to power-on of the electronic camera. The electronic camera according to claim 1,
The electronic camera has a photographing mode for photographing the image, and a power saving mode for suppressing power consumption in the electronic camera,
The electronic camera according to claim 1, wherein the focus adjustment unit is activated in response to a shift from the power saving mode to the photographing mode. The electronic camera according to claim 1,
The electronic camera has a shooting mode for shooting the image and a non-shooting mode for performing operations other than shooting,
The electronic camera according to claim 1, wherein the focus adjustment unit is activated in response to a shift from the non-shooting mode to the shooting mode. The electronic camera according to any one of claims 1 to 6,
The first imaging means is an imaging element that outputs a captured subject image as an image signal, and the second imaging means is a distance measuring element that detects a subject distance based on the captured subject image. camera.

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