JP2000250090A - Camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a camera capable of executing photometry while keeping a ratio of an angle of visibility constant even in the case the focal distance of a taking lens is changed. SOLUTION: The camera is provided with a focal distance variable photographic lens, a focal distance detecting means 15 for detecting the focal distance of the photographic lens, a focusing sensor 12 constituted of plural pixels for outputting an object image signal in accordance with the object distance in order to shift the photographic lens to a focusing position, and a photometry means 13 for measuring the luminance value of the object by using a prescribed pixel area of the focusing sensor 12, and as to the photometry means 13, the luminance value of the object is measured by switching the using pixel area of the focusing sensor 12 in accordance with focal distance information detected by the focal distance detecting means 15.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a camera capable of performing partial photometry, generally referred to as spot photometry, and more particularly, to a method for performing partial photometry using a focusing (AF) sensor. It relates to the improvement of the camera to be performed.

[0002]

2. Description of the Related Art A camera having a photometric sensor divided concentrically and switching the effective area of the photometric sensor according to the focal length of a zoom lens has been proposed.

[0003] Apart from this, a number of techniques have been proposed which also serve as an AF sensor and a photometric sensor.

[0004] Actually, a single-lens reflex camera that performs spot photometry using an AF line sensor has also been commercialized.

By the way, the recent miniaturization of the passive AF sensor unit and the high-magnification zoom and miniaturization of the compact camera have made the photometric technology described above more and more important.

[0006]

However, in the photometric sensor divided into concentric circles as described above, there is a limit in increasing the number of concentric circles or the like in accordance with an increase in zoom magnification. As a result, a significant discontinuity occurs in the photometric value near the switching point of the effective area.

Further, when photometry is performed by a passive AF sensor having an optical system independent of the taking lens, the ratio of the viewing angle of the passive AF sensor to the angle of view of the photographing depends on the focal length of the taking lens. As a result, the photometric area with respect to the angle of view also changes. As a result, a photometric area that is contrary to the user's will is measured.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a camera capable of performing photometry with a constant viewing angle ratio even when the focal length of a taking lens changes. And

[0009]

Means for Solving the Problems (1) According to the present invention,
In order to solve the above problems, a variable focal length photographing lens, a focal length detecting means for detecting the focal length of the photographing lens, and to displace the photographing lens to a focal position,
A focusing sensor comprising a plurality of pixels for outputting a subject image signal corresponding to the subject distance; and a photometric unit for measuring a brightness value of the subject using a predetermined pixel area in the focusing sensor. A camera, wherein the photometric unit measures a luminance value of the subject by switching a pixel area used by the focusing sensor in accordance with the focal length information detected by the focal length detecting unit. You.

(2) According to the present invention, in order to solve the above-mentioned problems, a photographic lens having a variable focal length, a focal length detecting means for detecting the focal length of the photographic lens, and focusing the photographic lens. A photometric sensor that measures a luminance value of a subject using a focusing sensor including a plurality of pixels that outputs a subject image signal corresponding to a subject distance and a predetermined pixel area in the focusing sensor in order to displace the subject. Means, a photometry area display mark fixed to display the photometry area of the photometry means in the viewfinder field, and the focal length information detected by the focal length detection means. By switching the use pixel area of the focus sensor, the photometry area indicated by the photometry area display mark always coincides with the use pixel area of the focusing sensor by the photometry means. Camera characterized by comprising a control means for, is provided.

(3) According to the present invention, in order to solve the above-mentioned problem, the photometric means uses a predetermined pixel area in the focusing sensor to display a finder visual field indicated by the photometric area display mark. The first photometric unit for measuring the spot photometric region, which is a partial region of the subject inside, and a photometric sensor provided separately from the focusing sensor, make the first photometric unit more than the spot photometric region by the first photometric unit. (2) The camera according to (2), further comprising: a second photometer that measures luminance in a wide area.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a schematic configuration of a camera according to an embodiment of the present invention.

That is, as shown in FIG. 1, the camera includes a control circuit 11 for controlling the entire camera, an AF unit 12 connected to the control circuit 11, and a photometric unit 1
3, lens drive circuit 14, focal length detection circuit 15, EE
It comprises a PROM 16, a zoom up (ZU) switch 17, a zoom down (ZD) switch 18, and a zoom lens unit 19 connected to the lens drive circuit 14 and the focal length detection circuit 15.

Here, the control circuit 11 is a microprocessor, and includes a ROM, a RAM, a timer, a counter, and the like, so that an exposure operation (AF, photometry, It controls the entire camera such as shutter drive, zoom lens control, film feeding, and input of various switches.

The zoom lens unit 19 comprises a mechanism for switching the focal length of a taking lens (taking lens) system including a zoom lens (not shown) as a variable focal length taking lens, a motor, and the like. The movement of the lens is also linked with the display of a finder (not shown).

The zoom lens driving circuit 14 drives the motor in the zoom lens unit 19 in accordance with a control signal from the control circuit 11 to drive the zoom lens, that is, perform zooming.

The focal length detecting circuit 15 detects the amount of extension of a lens frame that supports the photographing lens (not shown) so as to be variable in focal length, as a focal length detecting means for detecting the focal length of the photographing lens. The focal length is detected based on the extension amount of the lens frame, and the focal length information is output to the control circuit 11.

In the control circuit 11, the focal length information from the focal length detecting circuit 15 is stored in the RAM in the control circuit 11.

The ZU switch 17 and the ZD switch 1
Reference numeral 8 denotes a switch operated by the user, and instructs a driving direction of the zoom lens in the zoom lens unit 19 via the control circuit 11 by operating the switches.

The zoom lens is driven to the telephoto side by operating the ZU switch 17 and to the wide-angle side by operating the ZD switch 18.

The AF unit 12 is for focusing (AF) comprising a plurality of pixels for outputting a subject image signal corresponding to the subject distance in order to displace the taking lens to a focusing position.
The sensor includes a pair of imaging lenses and a pair of sensor rows corresponding to the pair of imaging lenses.

Then, according to an instruction from the control circuit 11,
All the sensors of the AF unit 12 simultaneously start integration of the photocurrent corresponding to the subject image formed via the imaging lens, and similarly stop the integration according to an instruction from the control circuit 11.

The integration result of each sensor of the AF unit 12 is output to the control circuit 11 as an analog voltage in synchronization with a clock signal from the control circuit 11.

In the control circuit 11, the AF unit 12
A / D conversion is performed on the analog voltage from the control circuit 11 and the digital data is stored in the RAM in the control circuit 11.

At the same time, the control circuit 11
The time data of the integration of each sensor of the F unit 12 is also stored in the RAM in the control circuit 11.

Then, the control circuit 11 calculates the distance to the subject and the luminance using these stored data.

The photometric unit 13 includes an imaging lens (not shown) provided on an optical path different from the optical path of the photographing lens, and a photometric sensor, for example, concentrically divided, which receives light via the imaging lens. And measures the average luminance of the object scene.

The photometric result from the photometric unit 13 is
The control circuit 1 compresses the photocurrent logarithmically and converts it into an analog voltage.
1 is output.

In the control circuit 11, the photometric unit 13
A / D conversion of the photometric output from
Store in AM.

The EEPROM 16 is an electrically rewritable nonvolatile memory in which adjustment values specific to the camera and the like are stored in advance.

The EEPROM 16 is connected to the control circuit 11 via a communication line, and supplies these adjustment values and the like to the control circuit 11 in response to access from the control circuit 11.

The EEPROM 18 (or the ROM in the control circuit 11) has information corresponding to the focal length information of the photographing lens for photometric calculation using a focusing (AF) sensor of the AF unit 12, which will be described later. It is assumed that the values of the used pixel areas of the AF sensor are stored in a table format in association with each other.

As described above, the present invention is provided with the photometric means for measuring the luminance value of the object using the predetermined pixel area in the focusing sensor.

Further, according to the present invention, the control circuit 11 switches the pixel area of the focusing sensor by the photometric means in accordance with the focal length information detected by the focal length detecting circuit 15, whereby Control is performed such that the photometry area indicated by the photometry area display mark always coincides with the use pixel area of the focusing sensor by the photometry means.

In the present invention, the photometric means uses a predetermined pixel area of the focusing sensor of the AF unit 12 to cover a partial area of the subject within the viewfinder field indicated by the photometric area display mark. The luminance of an area wider than the spot light measuring area by the first light measuring means is determined by the first light measuring means for measuring light of a certain spot light measuring area and the light measuring sensor of the light measuring unit 13 provided separately from the focusing sensor. Is provided.

The photometric sensor of the photometric unit 13 serves as first light receiving means for generating a subject brightness signal corresponding to the light intensity distribution of the subject image to be photographed. The subject image is projected through an optical path different from the optical path of the first light receiving unit, and serves as a second light receiving unit that generates a subject luminance signal corresponding to the light intensity distribution of the subject image.

Next, in the camera of the present invention configured as described above, even if the focal length of the taking lens (taking lens) changes, accurate photometry with a constant viewing angle ratio becomes possible. This will be described.

FIGS. 2A, 2B, and 2C show the relationship between the field of view of the AF sensor and the angle of view for each focal length at wide angle, standard, and telephoto, respectively.

In each of these figures, the outer frame is the angle of view for photographing,
The center circle indicates the spot metering target mark, and the ladder-shaped portion indicates the field of view of the pixel row of the AF sensor.

The angle of view changes with zooming, but the field of view of the AF sensor does not change. Therefore, when viewed relatively, only the vicinity of the center is widened at wide angle, and the entire screen is telescoped at telephoto.

As is apparent from FIG. 2, in order to make the photometric target mark coincide with the photometric area, that is, even if the focal length of the taking lens (taking lens) changes, the ratio of the viewing angle is kept constant. In order to enable accurate photometry, the pixel area of the AF sensor used for photometry should be switched according to a change in the focal length of the photographing lens.

FIG. 3 shows the relationship between the integration time of the AF sensor and the output voltage.

The output voltage of this AF sensor is proportional to the above-described integration time of the photocurrent, and the slope depends on the magnitude of the photocurrent, that is, the brightness of the subject, as shown in FIG. .

FIG. 4 shows the relationship between the pixel region output voltages at the end of the integration of the AF sensor.

That is, the integration of the photocurrent by the AF sensor is terminated when the output of the pixel area of the sensor corresponding to the brightest part of the subject reaches a predetermined level. Each pixel area output of the sensor at the time is as shown in FIG.

Next, a description will be given of a method in which the control circuit 11 calculates the luminance value of the subject from the integration result.

The output voltage (V) when the photocurrent (i) of the AF sensor is accumulated in the capacitor (C) for a time (T) at a certain luminance is represented by the following equation.

[0049] Here, i, for example, the reference luminance as BV0, because the a i = I · 2 ^.DELTA.BV Expressed relative to the photocurrent I when, can be expressed by ² ΔBV = CV / IT.

By the way, Since it is _{BV = log 2 C + log 2} V-log 2 I-log 2 T.

Of these, C and I are constants unique to the AF sensor, and if the terms of C and I are set as constants Cnst, then BV = log ₂ V−log ₂ T + Cnst.

By the way, if C and I are considered to be equal in each pixel area of the AF sensor, since the integration time is equal, the difference between the n pixel areas is only the V term.

Therefore, the average BV of each pixel area of all n sensors is Can be represented by That is, this is It is.

Similarly, considering each of the j-th to N-th pixel regions, Becomes

Here, j indicates the start position of the pixel area of the AF sensor effective for photometry, and N indicates the number of pixels of the AF sensor effective for photometry.

For such a photometric calculation, as described above, the values of the pixel areas j and N of the AF sensor are set to EE in advance corresponding to the focal length information of the photographing lens.
The data is stored in a table format in the PROM 18 (or the ROM in the control circuit 11).

Therefore, as described above, the control circuit 11 pre-stores the data in the EEPROM 1 in accordance with the focal length information of the photographing lens stored in the RAM in the control circuit 11 at that time.
8 (or ROM in the control circuit 11), the values of j and N in the above equation are used so as to use the values of the use pixel areas j and N of the AF sensor stored in a table format corresponding to the focal length information of the photographing lens. By appropriately switching N and calculating the BV, a photometric value with an appropriate angle of view can be obtained.

As described above, according to the camera of the present invention, it is possible to always perform photometry in an optimum area regardless of the focal length of the zoom lens.

The present invention described in the above-described embodiments includes the following additional inventions.

(Supplementary Note 1) In a camera that performs photometry using an auto-focus sensor composed of a plurality of photometric pixel rows, a zoom lens having a variable focal length and a focal length detecting means for detecting focal length information of the zoom lens are provided. Wherein the photometric pixel area used for photometry is switched according to the output of the focal length detecting means.

(Supplementary Note 2) A photographing lens having a variable focal length,
Focal length detecting means for detecting the focal length of the taking lens,
In order to displace the photographing lens to the in-focus position, the luminance value of the subject is measured using a focusing sensor composed of a plurality of pixels that outputs a subject image signal corresponding to the subject distance, and the pixels of the focusing sensor. Photometric means, a photometric area display mark fixed to display the photometric area of the photometric means in the viewfinder field, and the focal length sensor of the focusing sensor according to the focal length information detected by the focal length detecting means. A camera, comprising: control means for switching a use area of a plurality of pixels so that an area indicated by the photometry area display mark always coincides with the use area of the photometry means.

(Supplementary Note 3) In the above (Supplementary Note 2), the first photometering means for photometering a part of the spot area of the subject in the finder field, which is the area indicated by the photometering area display mark, A second photometric unit that is provided with a photometric sensor separately from the focus sensor, and measures luminance of a wide area wider than the spot area of the subject in the finder visual field by the photometric sensor. Camera.

(Supplementary Note 4) The camera according to (Supplementary Note 2), wherein the focus sensor is a sensor in which a plurality of pixels are arranged in parallel.

(Supplementary Note 5) The camera according to (Supplementary Note 2), wherein the focusing sensor is composed of a pair of a plurality of pixel rows.

(Supplementary Note 6) In the above (Supplementary Note 2), the photometric means may include a first light receiving means for generating a subject luminance signal corresponding to a light intensity distribution of a photographed subject image, and the first light receiving means. A second light receiving means for projecting the subject image through an optical path different from the optical path of the subject and generating a subject luminance signal corresponding to the light intensity distribution of the subject image. .

(Supplementary Note 7) A photographing lens having a variable focal length,
Focal length detecting means for detecting the focal length of the taking lens,
In order to displace the taking lens to the in-focus position, the brightness value of the subject is measured using a focusing sensor composed of a plurality of pixels that outputs a subject image signal corresponding to the subject distance, and the pixels of the focusing sensor. A photometric device that changes the number of pixels used by the focusing sensor according to the focal length information detected by the focal length detecting device.

[0067]

Therefore, as described above, according to the present invention, it is possible to provide a camera capable of performing photometry with a constant viewing angle ratio even if the focal length of the taking lens changes. Can be.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration of a camera according to an embodiment of the present invention.

FIGS. 2A, 2B, and 2C are diagrams showing the relationship between an AF sensor field of view and a shooting angle of view for each focal length at wide angle, standard, and telephoto, respectively.

FIG. 3 is a diagram illustrating a relationship between an integration time of an AF sensor and an output voltage.

FIG. 4 is a diagram illustrating a relationship between pixel region output voltages at the time when integration of an AF sensor is completed.

[Explanation of symbols]

 11: control circuit, 12: AF unit, 13: photometric unit, 14: lens drive circuit, 15: focal length detection circuit, 16: EEPROM, 17: zoom up (ZU) switch, 18: zoom down (ZD) switch, 19 ... Zoom lens unit 19

Claims (3)

[Claims] 1. A photographing lens having a variable focal length, a focal length detecting means for detecting a focal length of the photographing lens, and outputting a subject image signal according to a subject distance to displace the photographing lens to a focusing position. Using a focusing sensor consisting of a plurality of pixels to be focused on, and a predetermined pixel area in the focusing sensor,
Photometric means for measuring the luminance value of the subject, wherein the photometric means switches the pixel area used by the focusing sensor according to the focal length information detected by the focal length detecting means, and A camera for measuring a value. 2. A photographing lens having a variable focal length, a focal length detecting means for detecting a focal length of the photographing lens, and outputting a subject image signal according to a subject distance to displace the photographing lens to a focusing position. Using a focusing sensor composed of a plurality of pixels, and a predetermined pixel area in the focusing sensor,
A photometric unit for measuring a luminance value of a subject; a photometric region display mark fixed to display a photometric region of the photometric unit in a finder field; and a focal length information detected by the focal length detecting unit. By switching the used pixel area of the focusing sensor by the photometric means, the photometric area indicated by the photometric area display mark always matches the used pixel area of the focusing sensor by the photometric means. And a control means for controlling the camera. 3. A spot metering area, which is a partial area of a subject within a viewfinder field indicated by the metering area display mark, using a predetermined pixel area of the focusing sensor by the metering means. And a second photometric unit configured to measure a luminance of an area wider than the spot photometric area by the first photometric unit by a photometric sensor provided separately from the focusing sensor. The camera according to claim 2, wherein: