JP3565833B2 - Imaging device and imaging method - Google Patents

Description

[0001]
【Technical field】
The present invention relates to an imaging device and an imaging method including a solid-state electronic imaging device provided with a micro lens corresponding to a pixel.
[0002]
[Background Art]
2. Description of the Related Art In an imaging device represented by a still video camera, a subject is photographed using a solid-state electronic imaging device such as a CCD. Some solid-state electronic imaging devices have a micro lens provided on the light receiving surface corresponding to a pixel in order to increase the amount of light incident on the light receiving unit.
[0003]
2 and 3 show a part of a cross-sectional view of a CCD in which a micro lens is provided on a light receiving surface. 2 shows the state of the incident light beam P1 when the aperture value of the stop provided in front of the CCD is large, and FIG. 3 shows the state of the incident light beam P2 when the aperture value of the stop provided in front of the CCD is small. I have.
[0004]
The CCD includes a light receiving unit 32 that receives an incident light beam and accumulates it as a signal charge, and a vertical transfer path 33 that vertically transfers the signal charge accumulated in the light receiving unit 32. The vertical transfer path 33 is provided with a light shielding film 31 and is not irradiated with light. A micro lens 30 is provided on the front surface of the light receiving section 32.
[0005]
In such a CCD, when the aperture value of the aperture is large as shown in FIG. 2, the light beam P1 entering the micro lens 30 is a parallel light beam, and almost all the light beams enter the light receiving unit 32. However, as shown in FIG. 3, when the aperture value of the aperture is reduced, the light beam P2 incident on the micro lens 30 is oblique, and the refraction angle increases depending on the incident angle. As a result, the light does not enter the light receiving section 32.
[0006]
In a still video camera, subject brightness is generally measured using an external photometric element having an optical axis different from the optical axis of the imaging optical system, and exposure conditions are determined according to the subject brightness value. In the case of a CCD provided with, when the aperture value of the aperture is reduced, the incident light of the CCD may be shaken by the light shielding film 31, so that the output of the CCD decreases as shown in FIG. For this reason, when the subject is photographed with the exposure condition determined based on the subject luminance value measured by the photometric element, the exposure amount may be insufficient.
[0007]
Also, when the distance from the CCD to the position of the exit pupil is short, it is considered the same as when the aperture value of the aperture is large, and the output signal of the CCD may decrease as shown in FIG. Also in this case, if the exposure condition is determined based on the subject luminance value measured by the external photometric element and the subject is photographed, the exposure amount may be insufficient. In a still video camera having a zoom function, as shown in FIG. 6, the closer to the wide position, the shorter the distance from the CCD to the exit pupil, and the lower the CCD output.
[0008]
DISCLOSURE OF THE INVENTION
SUMMARY OF THE INVENTION It is an object of the present invention to enable an image pickup apparatus that determines an exposure condition using an external photometric element to always obtain an image of appropriate brightness.
[0009]
The present invention provides an image pickup apparatus having an external photometric element for measuring the luminance of a subject, and exposure control means for performing exposure control based on the luminance value of the subject obtained from the external photometric element. A light receiving element provided with a micro lens, an imaging means including a solid-state electronic imaging element for outputting a video signal representing a subject image, a shutter means for controlling an exposure time of the solid-state electronic imaging element, and an exposure control by the exposure control means. An aperture value is determined based on the aperture value. The aperture value restricts light incident on the solid-state electronic image pickup device. The smaller the aperture value of the aperture value is, the smaller the aperture value is determined from the subject brightness and the aperture value obtained by the external photometric element. Storage means for storing in advance shutter speed control data having a shutter speed lower than the shutter speed of the means in accordance with the aperture value. And shutter control means for reading shutter speed control data corresponding to the aperture value of the aperture from the storage means and controlling the shutter speed of the shutter means in accordance with the shutter speed control data. .
[0010]
The present invention also provides the above imaging method.
[0011]
According to the imaging apparatus of the present invention, as the aperture value of the aperture is smaller, shutter speed control data in which the shutter speed is lower than the shutter speed determined from the subject luminance and the aperture value is stored in advance in correspondence with the aperture value. . Exposure is controlled by the exposure control means to determine an aperture value, shutter speed control data corresponding to the aperture value is read from the storage means, and the shutter speed is determined according to the shutter speed data.
[0012]
According to the present invention, since the shutter speed becomes slower as the aperture value becomes smaller, the amount of light incident on the CCD increases, and even if the incident light is shaded by the light-shielding film of the CCD, it is determined based on the subject luminance value obtained by the photometric element. An image with an appropriate brightness is captured by capturing an image with an appropriate exposure amount.
[0013]
In the above, the photometric element is other than the photometric means for measuring the luminance value of the subject based on the video signal output from the CCD. The photometric element has an optical axis different from the optical axis of the imaging optical system. It may be divided into two parts by a splitter, one of which is used for CCD and the other is used for photometry.
[0014]
【Example】
FIG. 1 shows an embodiment of the present invention and is a block diagram showing an electric configuration of a still video camera.
[0015]
The overall operation of the still video camera is controlled by the CPU 18.
[0016]
A subject image is formed on a CCD 12 via an aperture 11 by an imaging lens 10 having a zoom function.
[0017]
The still video camera includes a tele / wide switch 19 for setting the zoom position. When the operator operates the tele / wide switch 19, a signal indicating the setting is given to the CPU 18. The zoom motor 13 is controlled by the CPU 18 and the imaging lens 10 is positioned by the zoom motor 13.
[0018]
The still video camera has an optical axis different from the optical axis of the imaging lens 10 and is provided with a photometric sensor 20 for measuring the luminance of the subject.
[0019]
The photometric detection signal output from the photometric sensor 20 is given to the CPU 18. The aperture motor 14 is controlled by the CPU 18 according to the photometric detection signal, and the aperture motor 14 determines the size of the aperture of the aperture 11.
[0020]
The CCD 12 has a micro lens 30 disposed in front of the pixel as shown in FIGS. 2 and 3, and performs a so-called electronic shutter operation. The still video camera includes a CCD drive timing pulse generation circuit 21 and is controlled by the CPU 18. The electronic shutter operation of the CCD 12 is controlled by the CCD drive timing / pulse generation circuit 21.
[0021]
Since the micro lens 30 is provided on the front surface of the CCD 12 corresponding to the light receiving unit 32, the smaller the aperture value of the aperture 11 or the closer the position of the exit pupil from the CCD 12, the more the incident light is cut by the light shielding film of the CCD 12. The amount of light increases, and the output signal of the CCD 12 may decrease. For this reason, in the still video camera shown in FIG. 1, as the aperture value of the aperture 11 is smaller, or as the distance from the CCD 12 to the exit pupil is shorter, a shutter speed lower than the shutter speed determined from the subject luminance luminance and the aperture value. The control is performed by the CPU 18 so that the gain of the automatic gain adjustment circuit 15 described later becomes higher than the normal gain. Since the exit pupil is an image in the image space of the aperture stop, in the still video camera shown in FIG. 1, an exit pupil is formed at a position Ep shown in the figure. Since the position of the exit pupil Ep is determined by the zoom position of the imaging lens 10, the distance from the CCD 12 to the exit pupil Ep can be recognized by the driving amount of the zoom motor 13.
[0022]
A memory 22 is attached to the CPU 18 and stores shutter speed control data corresponding to the aperture value such that the smaller the aperture value of the aperture 11, the slower the shutter speed determined by the exposure conditions. Further, the memory 22 stores gain control data for setting the gain of the automatic gain adjustment circuit 15 such that the smaller the aperture value of the aperture 11 is, the higher the gain of the automatic gain adjustment circuit 15 becomes. Correspondingly stored. These shutter speed control data and gain control data are stored in the memory 22 in the form of a table.
[0023]
The memory 22 stores shutter speed control data corresponding to the distance from the CCD 12 to the position of the exit pupil such that the closer the distance from the CCD 12 to the position of the exit pupil, the slower the shutter speed determined by the exposure conditions. It is remembered. The memory 22 has gain control data for setting the gain of the automatic gain adjustment circuit 15 such that the gain from the automatic gain adjustment circuit 15 becomes relatively higher as the distance from the CCD 12 to the position of the exit pupil becomes shorter. Is stored in correspondence with the aperture value. These shutter speed control data and gain control data are also stored in the memory 22 in the form of a table.
[0024]
The video signal output from the CCD 12 is supplied to the automatic gain adjustment circuit 15. The automatic gain adjustment circuit 15 amplifies the input video signal under the control of the CPU 18 and supplies the amplified video signal to the imaging system signal processing circuit 16.
[0025]
In the imaging system signal processing circuit 16, white balance adjustment, generation processing of a luminance signal Y, and color difference signals RY and BY are performed.
[0026]
The signal output from the imaging system signal processing circuit 16 is provided to a recording signal processing circuit 17.
[0027]
The recording signal processing circuit 17 includes a line-sequencing circuit, a pre-emphasis circuit, an FM modulation circuit, a synthesizing circuit, and the like. An FM-modulated synthesized video signal is output from the circuit 17 and applied to a recording medium such as a magnetic disk. Be recorded.
[0028]
Next, a processing procedure at the time of shooting using the still video camera shown in FIG. 1 will be described.
[0029]
First, the photographer operates the tele / wide switch 19, and the photographing lens 10 is positioned at a predetermined position by the zoom motor 13. The aperture value of the aperture 11 is determined based on the photometric detection signal output from the photometric sensor 20. The aperture 11 is controlled by the aperture motor 14 so that the aperture value becomes a determined aperture value.
[0030]
The shutter speed control data stored in the memory 22 is read out in consideration of the incident light emitted by the micro lens provided on the front surface of the CCD 12, and shooting at the shutter speed represented by the shutter speed control data is performed. Thus, the CCD 12 is controlled by the CCD drive timing / pulse generation circuit 21.
[0031]
Further, gain control data that determines the amplification factor of the automatic gain adjustment circuit 15 in accordance with the distance between the CCD 12 and the exit pupil Ep, which is known from the drive amount of the zoom motor 13, is read from the memory 22, and is represented by the gain control data. The automatic gain adjustment circuit 15 is controlled so as to obtain the amplification factor.
[0032]
A subject image is formed on the CCD 12 by the imaging lens 10 via the aperture 11, and the subject is photographed at a predetermined shutter speed in accordance with the depression of a shutter release button (not shown).
[0033]
A video signal representing a subject image is output from the CCD 12, and is amplified in the automatic gain adjustment circuit 15 by an amplification factor represented by the gain control data read from the memory 22. The video signal amplified by the automatic gain adjustment circuit 15 is given to a recording medium such as a magnetic disk (not shown) via the imaging system signal processing circuit 16 and the recording signal processing circuit 17 and recorded there, as described above.
[0034]
Since the shutter speed and the gain in the automatic gain adjustment circuit 15 are determined in accordance with the aperture value of the aperture 11 and the distance from the CCD 12 to the exit pupil, respectively, the aperture of the aperture 11 is large or the distance from the CCD 12 to the exit pupil. When the distance is close, an image having an appropriate brightness can be obtained even if the incident light of the CCD 12 is shaded.
[0035]
In the above embodiment, the exposure condition is determined by the photometric sensor 20, and the aperture value of the aperture 11 is determined so as to satisfy the exposure condition. The CCD 12 is controlled so that the shutter speed stored in the memory 22 corresponds to the aperture value. Further, the amplification factor of the automatic gain adjustment circuit 15 is controlled such that the amplification factor of the automatic gain adjustment circuit 15 increases as the distance from the CCD 12 to the exit pupil decreases.
[0036]
However, the smaller the aperture value of the aperture 11, the higher the gain of the automatic gain adjustment circuit 15 and the lower the shutter speed. The shorter the distance from the CCD 12 to the exit pupil, the higher the gain of the automatic gain adjustment circuit 15. It is also possible to increase the shutter speed and decrease the shutter speed. In addition, any one of increasing the amplification factor according to the size of the aperture value, decreasing the shutter speed, increasing the amplification factor of the automatic gain adjustment circuit 15 according to the distance from the CCD 12 to the exit pupil, and decreasing the shutter speed is optional. May be used to obtain an image with appropriate brightness. In any case, the shutter speed and the amplification factor of the automatic gain adjustment circuit 15 may be determined so that an image with appropriate brightness is obtained according to the aperture value of the aperture 11 and the distance from the CCD 12 to the exit pupil.
[0037]
Further, the memory 22 stores shutter speed data at which the shutter speed is lower than the shutter speed determined from the subject brightness and the aperture value, and performs shutter control. The memory 22 stores the shutter speed determined from the subject brightness and the aperture value. It is also possible to store shutter speed correction data such that the shutter speed is lower than the speed, and correct the shutter speed determined based on the photometric value obtained by the photometric element 20 using the correction data. In any case, the larger the aperture value and the shorter the distance from the CCD 12 to the exit pupil, the slower the shutter speed than the shutter speed determined from the subject brightness and the aperture value.
[Brief description of the drawings]
FIG. 1, showing an embodiment of the present invention, is a block diagram illustrating an electrical configuration of a still video camera.
FIG. 2 shows how parallel light is incident on a CCD having a micro lens.
FIG. 3 shows a state of light obliquely incident on a CCD having a micro lens.
FIG. 4 shows a relationship between an aperture value and a CCD output.
FIG. 5 shows the relationship between the distance from the CCD to the exit pupil and the CCD output.
FIG. 6 shows a relationship between a zoom position and a distance from a CCD to an exit pupil.
[Explanation of symbols]
11 Aperture 12 CCD
15 Automatic gain adjustment circuit 18 CPU
20 Photometric element

Claims (2)

An image pickup apparatus comprising: an external photometric element for measuring a subject luminance; and an exposure control unit for performing exposure control based on a subject luminance value obtained from the external photometric element.
An imaging means including a solid-state electronic imaging device having a plurality of light receiving elements, each of the light receiving elements being provided with a micro lens, and outputting a video signal representing a subject image;
Shutter means for controlling the exposure time of the solid-state electronic imaging device;
An aperture value is determined based on the exposure control by the exposure control means, and an aperture for limiting incident light to the solid-state electronic imaging device is provided.
As the aperture value of the aperture is smaller, the shutter speed control data, which is a shutter speed lower than the shutter speed of the shutter means determined from the subject brightness and the aperture value obtained by the external photometric element, corresponds to the aperture value. Storage means for storing in advance the shutter speed control data corresponding to the aperture value of the aperture from the storage means, and shutter control means for controlling the shutter speed of the shutter means in accordance with the shutter speed control data;
An imaging device comprising: An image pickup apparatus comprising: an external photometric element for measuring a subject luminance; and an exposure control unit for performing exposure control based on a subject luminance value obtained from the external photometric element.
Shutter speed control in which the smaller the aperture value of the aperture determined based on the exposure control by the exposure control means, the lower the shutter speed determined from the subject brightness and the aperture value obtained by the external photometric element. Data is stored in advance corresponding to the aperture value,
A plurality of light-receiving elements, each of which is provided with a micro lens, and a solid-state image pickup device for outputting a video signal representing the subject image, photographing the subject and obtaining a video signal representing the subject image;
Reading shutter speed control data corresponding to the aperture value, and photographing an object at a shutter speed corresponding to the read shutter speed control data;
Imaging method.

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