JP2001128056A - Camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect an optimal focusing state always even when a subject is dark. SOLUTION: Among the area of a subject to which auxiliary light is irradiated, an area having brightness at a level equal to or higher than a prescribed level (desirably at a maximum level) is detected and set to be an AF area to always detect an optimal focusing state. Among the divided areas of a CCD image pickup element, an area except the AF area is swept out speedily to realize speedy AF processing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a camera for capturing a subject image and obtaining a video signal, and more particularly to an electronic camera having a function of irradiating auxiliary light to detect a focus state.

[0002]

2. Description of the Related Art Conventionally, in an electronic camera which obtains a video signal by capturing a subject image by a CCD image pickup device or the like, a video signal is used for performing exposure control and focus adjustment.
For example, for focus adjustment, a focusing operation can be performed by measuring a high-frequency component of a video signal and driving a focus lens so that the high-frequency component is maximized.

When the subject is dark and the level of the video signal is low, if the video signal is used as it is, the luminance is insufficient and the focus adjustment of the photographing lens cannot be performed accurately. Therefore, in order to sufficiently increase the level of the video signal even when the subject is dark, a method of irradiating the subject with auxiliary light has been adopted. However, conventionally, an AF area for detecting a focus state is set at a predetermined position in an area irradiated with the auxiliary light. For this reason, the position where the AF (Auto Focus) area is set is not always an area having sufficient brightness to detect the focus state, and it is difficult to always accurately detect the focus state. there were.

[0004]

As described above, conventionally, when a subject is dark, auxiliary light is applied to the subject in order to increase the level of a video signal. Since the area is set, there is no guarantee that sufficient brightness is obtained for performing the AF processing. As a result, the AF process could not be performed, and a shutter chance was missed.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide sufficient brightness for performing AF processing when an object is dark and cannot receive its reflected light and is irradiated with auxiliary light. An object of the present invention is to provide a camera capable of easily detecting a holding position.

[0006]

In order to achieve the above object, an invention according to claim 1 is an object luminance detecting unit for detecting the luminance of a predetermined area of an object, and the luminance detected by the object luminance detecting unit. When the subject brightness is lower than a predetermined reference value, an auxiliary light irradiating unit that irradiates the subject with auxiliary light, and among the areas where the brightness is detected by the subject brightness detecting unit, Determining means for determining an area in which the signal level of reflected light obtained by irradiation is equal to or more than a predetermined value as an autofocus detection area; and determining a focus state based on an output from the autofocus detection area determined by the determination means. Calculating means for calculating, and driving means for driving the photographing lens based on an output from the calculating means, That.

According to the present invention, of the subject area irradiated with the auxiliary light, an area where the video signal is equal to or higher than a predetermined level is determined as an AF area, and the focus state is detected based on the video signal in the AF area. You. Also, only the video signal corresponding to the determined AF area is read, and the other signals are swept out at high speed.

According to the present invention, the auxiliary light irradiating means is provided below the photographing lens to irradiate the auxiliary light from the vicinity of the center of the photographing screen to the object area corresponding to the lower side of the photographing screen, and to emit light of a predetermined level or more. An area with brightness is detected, and this is set as an AF area. Further, a CCD driving method is set. Thus, even if the auxiliary light irradiation position is slightly shifted due to the distance to the subject, the auxiliary light can always be applied to the subject. Thus, even when the subject is dark, an accurate focus state of the subject from a long distance to a short distance can be detected with a simple configuration.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the illustrated embodiments.

(First Embodiment) FIG. 1 shows a first embodiment of the present invention.
FIG. 3 is a block diagram illustrating a basic configuration of an electronic camera according to the embodiment.

Referring to FIG. 1, an electronic camera includes a zoom lens 11 and a focus lens 12, an aperture 13, a CCD image pickup device 14, an image pickup circuit 15 for converting a CCD output into a video signal, and a digital video image signal. An A / D converter 16 for converting the signal into a signal and a buffer memory 17 for temporarily storing the A / D conversion output are provided. The electronic camera further includes a D / A converter 21 for converting a digital video signal into an analog video signal, a liquid crystal display element (LCD) 22 for displaying a D / A conversion output, and compression of the digital video signal. It has a compression / decompression circuit 23 for decompression and a recording memory 24 such as CompactFlash (registered trademark) or smart media.

[0012] Further, C for controlling each part in an integrated manner.
PU 30, AE (Auto Exposure) processing circuit 31, AF (Au
to Focus) processing circuit 32, timing generator (T
G) A circuit 33 and a CCD driver 34 are provided. further,
It has motor drivers 41-43 and motors 44-46, the first motor driver 41 and the first motor 44 control the aperture 13, the second motor driver 42 and the second motor 45 control the focus lens 12, The zoom lens 1 is driven by the third motor driver 43 and the third motor 46.
1 is driven. Further, an operation switch 51 such as a menu button and a release switch, and an EEP for storing the relationship between the set distance and the lens position in a table.
A ROM 52, a battery 53, and an auxiliary light source 54 for irradiating the subject with auxiliary light for various adjustments and the like in addition to shooting are provided.

As shown in FIG. 2, the auxiliary light source 54
Camera body 5 provided with CD image sensor 14 and lens
0 is provided below the lens. Then, the light from the auxiliary light source 54 is emitted in a direction deflected with respect to the optical axis of the photographing lens so that the light irradiation optical axis of the auxiliary light source 54 and the optical axis of the photographing lens intersect on the front side of the photographing lens. It is configured as follows. Specifically, the light irradiation optical axis of the auxiliary light source 54 and the optical axis of the photographing lens are set so as to substantially coincide with each other in the vicinity of the maximum reach distance of the light of the auxiliary light source 54. For this reason, the auxiliary light source 54 is positioned below the photographic lens so that the optical axis of the auxiliary light source 54 and the optical axis of the photographic lens intersect at a predetermined angle on the front side of the photographic lens. It is arranged in a direction deflected with respect to this. The position where the light irradiation optical axis of the auxiliary light source 54 and the optical axis of the imaging lens intersect at a predetermined angle on the front side of the imaging lens is set near the maximum reach of the auxiliary light emitted from the auxiliary light source. Have been. Accordingly, in a subject located at a position shorter than the maximum arrival distance, the irradiation area of the auxiliary light is below the optical axis. In the drawing, reference numeral 61 denotes a shooting area, 62 denotes a subject, 63 denotes an auxiliary light irradiation area at the maximum reaching distance, 64
Indicates an auxiliary light irradiation area at a distance shorter than the maximum arrival distance.

The basic operation of the present apparatus is as follows. That is, a subject image is formed on the image sensor 14 via the lenses 11 and 12 and the aperture 13,
The CD output is converted to a video signal. This signal is A / D
After being converted from an analog signal to a digital signal by the converter 16, it is temporarily stored in the image memory 17. Then, the video signal stored in the image memory 17 is
2 is displayed. The video signal stored in the image memory 17 is compressed by the compression / expansion circuit 23 and recorded in the recording memory 24. Conversely, the recording memory 24
Is expanded in the image memory 17 and stored in the LCD 2.
2 can be displayed.

The exposure is automatically adjusted by the AE processing circuit 31 based on the output signal of the A / D converter 16. Specifically, the A / D conversion output is integrated by the AE processing circuit 31, the integrated value (the integrated value of the Y signal of the video signal) is supplied to the CPU 30, and the accumulation time of the image sensor 14 is calculated by the CCD driver 34. , Which automatically adjusts the exposure. Further, the focus is automatically adjusted by the AF processing circuit 32 based on the output signal of the A / D converter 16. More specifically, A / A
A contrast value is obtained by integrating the D-converted output through a high-pass filter, the motor 45 is driven to move the focus lens 12, and the focus is automatically set by setting the contrast value to the maximum position. Can be.

Next, the focus control operation in the present embodiment will be described with reference to the flowchart of FIG. The release switch has two stages, one when the switch is pressed lightly and the other when the switch is pressed all the way.
The st release and the case where the button is pushed to the end are referred to as the 2nd release.

When the release switch is pressed for photographing in step S1 of FIG. 3 (first release), processing for automatically setting (AE) the exposure is performed in step S3. Next, in step S5, the brightness of the subject is measured to determine whether to use the auxiliary light. If it is determined in step S5 that the brightness is sufficient to detect the focus state, the process proceeds to step S11, where an AF area is set. In this case, in any area of the subject area, A
Since the brightness is sufficient to perform the F process, the AF area is set at a predetermined position.

On the other hand, if it is determined in step S5 that the brightness is such that the focus state cannot be detected,
In step S7, the auxiliary light source 54 is turned on and the auxiliary light is used. Then, in step S9, an area having brightness equal to or higher than a predetermined level is detected in the subject area. That is, as shown in FIG. 4, the CCD image sensor 14 is divided into, for example, 49 areas, and an area having a brightness equal to or higher than a predetermined level is detected. Then, in step S11, an AF area is set for an area having brightness equal to or higher than a predetermined level. That is, the auxiliary light from the auxiliary light source 54 is applied to the subject, and an area where the signal reflected from the subject is equal to or larger than a predetermined value is set in the AF area 7.
Set as 1. In this case, it is desirable to set the AF area for the area having the maximum brightness, but it is not always necessary to set the AF area to the area having the maximum brightness.
Any area having a sufficient level of brightness for performing the F process may be used.

Next, in step S13, the position where the maximum contrast is obtained is detected based on the video signal corresponding to the set AF area by, for example, the contrast method. Specifically, the focus lens 1
2 is driven little by little back and forth, and the respective contrasts are measured. The position where the highest contrast is obtained is defined as the focus position. Then, in step S15, the second release is awaited, and when the second release is performed, shooting is performed in step S17.

As described above, according to this embodiment, when the brightness is such that the focus state cannot be detected with respect to the subject, the auxiliary light source 54 is made to emit light, and the subject area irradiated with the auxiliary light is Of these, since an area having brightness equal to or higher than a predetermined level is set as an AF area, a video signal for focus state detection is used even for a dark subject, that is, a subject having a brightness that makes it impossible to detect the focus state. Level can be increased, and accurate focus detection can be performed.

(Second Embodiment) FIG. 5 shows a second embodiment of the present invention.
9 is a flowchart showing a focus control operation of the electronic camera according to the embodiment.

The configuration of the apparatus is the same as that of the first embodiment. In this embodiment, an area having a brightness equal to or higher than a predetermined level is detected, and an AF area is set in that area, as in the first embodiment. The CCD driving method is set.

In the flowchart shown in FIG. 5, steps S21 to S29 are the same as steps S1 to S9 in FIG. 3, and a description thereof will be omitted.

In step S31 of FIG. 5, an AF area 71 is set for an area having a brightness equal to or higher than a predetermined level among the divided areas of the CCD image sensor 14 shown in FIG. Then, the data reading speed from the CCD image sensor 14 is variably controlled depending on whether or not the line includes the AF area 71. That is, in FIG. 4, the data including the line including the AF area 71 is necessary, so that the reading is performed at a normal speed. However, since the data is unnecessary for the line that does not include the AF area 71, high-speed sweeping is performed. Specifically, the CPU 30 controls the TG circuit 33 to generate a clock signal faster than a clock signal used for normal reading, and
To supply. As a result, the charge of the CCD is transferred at a higher speed than in a normal case. Thereby, the AF process can be performed at higher speed.

Then, in steps S33 to S37, the same processing as described in steps S13 to S17 of FIG. 3 is performed.

The present invention is not limited to the above embodiments. In the embodiment, the high frequency component of the video signal is set to be the maximum for focusing in the AF processing circuit. However, the present invention is not limited to this. . Further, the imaging device is not necessarily limited to a CCD, but may be a CMOS.
It is also possible to use sensors. In the above-described embodiment, the case where the present invention is applied to an electronic camera has been described. However, the present invention can be applied to a camera using a silver halide film. In addition, various modifications can be made without departing from the scope of the present invention.

[0027]

According to the present invention, even if the subject is dark and illuminated with the auxiliary light, the AF process can be easily performed if there is reflected light of a predetermined level or more, so that a photo opportunity is missed. There is no. In addition, among the divided areas of the CCD image sensor, the other areas except for the area in which the AF area is set are subjected to high-speed sweeping so that the AF area is increased.
Processing can be performed at high speed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a basic configuration of an electronic camera according to a first embodiment.

FIG. 2 is a diagram illustrating an installation position of an auxiliary light source according to the first embodiment.

FIG. 3 is a flowchart illustrating a focus control operation according to the first embodiment.

FIG. 4 is a view showing setting of an AF area in the first embodiment.

FIG. 5 is a flowchart illustrating a focus control operation according to the second embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... Zoom lens 12 ... Focus lens 13 ... Aperture 14 ... CCD imaging device 15 ... Imaging circuit 16 ... A / D converter 17 ... Buffer memory 21 ... D / A converter 22 ・ ・ ・ Liquid crystal display device (LCD) 23 ・ ・ ・ Compression / expansion circuit 24 ・ ・ ・ Recording memory 30 ・ ・ ・ CPU 31 ・ ・ ・ AE processing circuit 32 ・ ・ ・ AF processing circuit 33 ・..Timing generator (TG) circuit 34 ... CCD driver 41 to 43 ... Motor driver 44 to 46 ... Motor 51 ... Operation SW 52 ... EEPROM 53 ... Battery 54 ... Auxiliary Light source

Claims (16)

[Claims] A subject brightness detection unit for detecting brightness of a predetermined region of the subject; and illuminating the subject with auxiliary light when the subject brightness detected by the subject brightness detection unit is lower than a predetermined reference value. An auxiliary light irradiating unit, and an area in which the signal level of the reflected light obtained by irradiating the object by the auxiliary light irradiating unit is equal to or more than a predetermined value in the area where the luminance is detected by the object luminance detecting unit, Determining means for determining a detection area; calculating means for calculating a focus state based on the output from the auto-focusing detection area determined by the determining means; driving the photographing lens based on the output from the calculating means And a driving unit. 2. The light emitted from the auxiliary light irradiating unit emits light of the photographing lens such that the light irradiating optical axis of the auxiliary light irradiating unit and the optical axis of the photographing lens intersect on the front side of the photographing lens. The camera according to claim 1, wherein the light is emitted in a direction deflected with respect to the axis. 3. The camera according to claim 1, wherein the auxiliary light irradiation unit is disposed below the photographing lens. 4. The photographing lens below the photographing lens such that a light irradiation optical axis of the supplementary light irradiation unit and an optical axis of the photographing lens intersect on the front side of the photographing lens. 2. The camera according to claim 1, wherein the camera is arranged in a direction deflected with respect to the optical axis. 5. A position where the light irradiation optical axis of the auxiliary light irradiation unit and the optical axis of the photographing lens intersect on the front side of the photographing lens is the maximum distance of the auxiliary light emitted from the auxiliary light irradiation unit. 5. The camera according to claim 2, wherein the camera is located near the camera. 6. The object brightness detection unit includes an image sensor for converting a subject image into a video signal, and a calculation circuit for calculating the subject brightness based on a video signal from a predetermined area of the image sensor. 2. The camera according to claim 1, wherein 7. The video signal corresponding to the auto-focus detection area among the video signals read from the image sensor when the determination circuit determines the auto-focus detection area by the determination means. 7. The camera according to claim 6, wherein the subject brightness is calculated based only on the subject. 8. An image sensor for converting a subject image into a video signal; a subject brightness calculation circuit for calculating a subject brightness from a video signal in a first area in the image sensor; The second video signal is higher than a predetermined value
Deciding means for deciding the region of interest as an AF detection region, computing means for computing a focus state based on the output from the AF detection region decided by the deciding device, and photographing based on the output from the computing device A camera comprising: driving means for driving a lens. 9. When the subject brightness value calculated by the subject brightness calculation circuit is lower than a predetermined value and the focus state cannot be detected, light is emitted from a direction deflected with respect to the optical axis of the taking lens. The camera according to claim 8, further comprising an auxiliary light irradiation unit. 10. A light irradiation direction of the auxiliary light irradiation unit is near a maximum reach distance of the auxiliary light emitted from the auxiliary light irradiation unit, and a light irradiation optical axis of the auxiliary light irradiation unit and a light of the photographing lens. 9. The camera according to claim 8, wherein the axis intersects at a predetermined angle on the front side of the taking lens. 11. The apparatus according to claim 1, wherein the auxiliary light irradiation unit is disposed below the photographing lens.
The camera according to 0. 12. An image signal corresponding to the AF detection area among the video signals read from the image sensor when the subject brightness calculation circuit determines the AF detection area by the determination means. 9. The camera according to claim 8, wherein subject brightness is calculated based only on the subject. 13. When the subject brightness calculation circuit calculates subject brightness based only on a video signal corresponding to the AF detection area, a video signal not corresponding to the AF detection area is regarded as an unnecessary signal as an unnecessary signal for the AF. 13. The camera according to claim 12, wherein the image is read out faster than a video signal corresponding to the detection area. 14. An imaging device capable of converting a subject image into a video signal and detecting a subject brightness using a part of the video signal, wherein the subject brightness detected by the imaging device is equal to or greater than a predetermined value. Determining means for determining an area as an AF detection area; calculating means for calculating a focus state based on an output from the AF detection area determined by the determining means; and calculating based on an output from the calculating means. And a driving means for driving the taking lens. 15. A determining means for determining whether the detected brightness of the subject is low and the focus state cannot be detected, and if the detected brightness of the subject is not equal to or more than a predetermined value, light is applied to the subject. An auxiliary light irradiating unit that irradiates the object, and wherein the determining unit determines an area in which the subject reflected light emitted by the auxiliary light irradiating unit is equal to or greater than a predetermined value as an AF detection area. The camera according to claim 14, wherein 16. The photographing lens below the photographing lens so that the light irradiation optical axis of the supplementary light irradiation unit and the optical axis of the photographing lens intersect on the front side of the photographing lens. The camera according to claim 15, wherein the camera is arranged in a direction deflected with respect to the optical axis.