JPH02170781A - Image pickup device - Google Patents

Abstract

PURPOSE:To execute a photographing to be diverse in image expressions by providing a gamma correction switching circuit and selecting and setting an arbitrary gamma correction curve. CONSTITUTION:A gamma correction switching circuit 41 is composed so as to execute the automatic selection and standard selection of the gamma correction curve by the operation of a knob 42 and, further, the arbitrary selection of the gamma correction curve by a manual operation. A control signal Ve to execute each selection in accordance with the position setting of the knob 42 is generated, and the control signal Ve is supplied to a camera control part 31. Consequently, a photographing situation is discriminated, for example, the setting and selection of the gamma correction curve are manually executed, and the photographed image can be made into a necessary exposure. Thus, the diverse photographing can be executed corresponding to the sense of a photographing person.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an imaging device such as an electronic camera or a VTR camera. The present invention relates to an imaging device capable of performing.

[Background Art] In recent years, video equipment including imaging devices has become more widespread, and the general public has come to take pictures using electronic cameras and VTR cameras.

However, except for some enthusiasts, general users do not have any special photographic techniques, and the photographing conditions vary widely. Considering this background, it is desirable that the photographing device be devised so that -acid users can always take good photographs. For example, when photographing a person as the main subject, if the sun is in the background, the person will be photographed darkly due to backlight.

On the other hand, in situations where the main subject is exposed to strong light, such as a person in the spotlight on a stage, a phenomenon known to those skilled in the art as highlight occurs, and the back of the main subject becomes dark. I end up being photographed. Therefore, in the past, an exposure compensation circuit was installed in the photographic device to compensate for the exposure and correct the main subject even under abnormal light as mentioned above.
That is, exposure compensation is applied to the positive side when backlighting and to the negative side when highlighting, so that photography can be performed at an appropriate exposure value.

[Problems to be Solved by the Invention] However, although conventional photographing devices are equipped with an exposure compensation circuit, the amount of exposure compensation is fixed.

Therefore, when there is a scene with a large brightness difference, in other words, there is a large difference between the brightness of the main subject and the brightness of the background, or when the main subject is uneven in the brightness distribution, for example, the main subject is in a dark or bright area. In some cases, when the main subject is set to the appropriate exposure value using exposure compensation, the entire screen becomes brighter, resulting in a phenomenon in which the bright areas become entirely white, a so-called broken state, and a phenomenon in which the entire dark areas become dark, a so-called crushed state. Become.

Furthermore, since the imaging device cannot automatically determine the photographing situation and change the exposure correction amount, the above-mentioned photographing error may be made at a good photo opportunity.

Therefore, the inventor studied automatic selection of exposure compensation and made automatic selection possible.

However, since photographing situations are not uniform and there are individual differences in perception regarding photographed images, automatic selection is not always optimal.

Further, there are cases where it is desired to intentionally shift the exposure value to take a photograph with a different impression without necessarily setting the exposure to the appropriate value, but if the amount of exposure compensation is fixed, such a variety of photographing cannot be performed.

In other words, by simply automatically selecting an exposure compensation curve, it is difficult to perform various types of photography in accordance with the photographer's preferences and the object to be photographed, and it has been desired to improve the added value.

The present invention has been made in view of the above-mentioned circumstances, and its purpose is to provide an imaging device that allows a photographer to perform a variety of shooting by determining the shooting situation and performing desired gamma correction. There is a particular thing.

[Means for Solving the Problems] In order to achieve such an object, the present invention is configured such that gamma correction curves can be set, selected, etc. arbitrarily.

[Function] In the present invention having such a configuration, it is possible to determine the shooting situation and, for example, manually set or select a gamma correction curve. The image can be exposed as desired.

Therefore, it is possible to perform various types of photography in accordance with the senses of the photographer, and it is possible to increase the functionality of the imaging device and increase its added value.

[Example] An embodiment of the present invention will be described below with reference to the drawings.

Note that FIG. 1 is a circuit diagram showing an example of an electronic still camera to which the present invention is applied, FIG. 2 is an explanatory diagram showing a photographing situation of a subject, and FIG. 3 is an explanatory diagram showing multi-division of a subject. Fourth
The figure shows a gamma correction curve and a gamma correction characteristic diagram during reproduction.

The feature of this embodiment is that it is provided with a gamma correction circuit and a gamma correction switching circuit that can select a gamma correction curve, but for convenience of explanation, the structure and operation of the entire imaging device will be explained first, and then the gamma correction The selection effect of is explained.

The imaging optical system 1 shown in FIG. 1 includes an autofocus lens 2, an aperture mechanism 3, and a condenser lens 4.
, a half mirror 5, and an optical low-pass filter 6,
The optical system 1 optically forms a subject image on an image sensor 7 such as a solid-state image sensor.

Incidentally, an optical color filter (not shown) is provided in front of the image sensor 7, that is, on the imaging plane of the subject image.

The photometric optical system 11 includes lenses 12, 13, and a half mirror 14, and monitors the image being photographed and forms a subject image on the light receiving element 15 as photometric data.

Next, the signal processing system will be explained. The image sensor 7 generates a color video signal Va corresponding to the brightness and color of the subject image by photoelectric conversion. The video signal Va
is a minute voltage level, and is amplified to a desired voltage level by the preamplifier 21.

The color separation circuit 22 obtains R (red), G (green), and B (blue) color signals. The color signals R, G, and B are supplied to the gamma correction circuit 23 and subjected to gamma correction, and this gamma correction operation will be described in detail later with reference to FIG. 2 and the subsequent figures.

The matrix circuit 24 receives gamma-corrected color signals R, G.
, B are subjected to predetermined signal processing to obtain a luminance signal Y and color difference signals RY and BY.

The color encoder 25 converts a total color video signal (NTS
C system color video signal), and further y+s.

Various signals such as R-Y and B-Y are obtained, and these are supplied to a display device (not shown) or a recording circuit, etc., and used for a desired purpose.

Next, to explain the photometry system, the subject image reflected by the half mirror 5 is projected onto the half mirror 14 via the lens 12, and this subject image is reflected by the finder F.
The image can be visually viewed as a monitor image through the lens 13.

In addition, the brightness of the subject image transmitted through the half mirror 14 is
It is detected by the light receiving element 15. The light receiving element 15 is constituted by a photoelectric conversion element, for example, an element with excellent photoelectric conversion efficiency such as a silicon photocell.

The present embodiment is configured not only to obtain a photometric signal corresponding to the brightness of the subject image, but also to divide the subject image into multiple parts and perform photoelectric conversion.

That is, one frame of the subject is divided into a plurality of areas, and a photometric signal corresponding to the luminance of each divided area is obtained individually.

Here, to explain an example of a subject in abnormal light with reference to Fig. 2, the sun B is located behind the main subject, person A, so not only the face of person A but the entire person becomes dark and dark. This is a typical backlit situation.

On the other hand, if the light-receiving element 15 is divided into four areas P1, P2, P3, and P4 as shown in FIG. 3, for example, when photographing the subject shown in FIG. A person, the main subject, is located in area P1, and bright background parts are located in areas P2, P3, and P4.

Under such backlight conditions, in other words, under abnormal light conditions,
The brightness of area P1 corresponding to the position of person A, who is the main subject, is at a low level, and the brightness of areas P2 to P4, which are divided and formed around the area P1, is high level. Therefore, from each of the areas P1 to P4 of the light receiving element 15, a photometric signal vb having a level difference corresponding to the difference in brightness of each area is obtained.

The photometric signal vb obtained in this way is
The AE photometry unit 16 performs the following noteworthy functions.

That is, the photometric signals vb obtained from the areas P1 to P4 are respectively Pbl, Pb2, Pb3, and Pb4. For example, from the value of P b4 /P bl, backlighting,
and a reference value k for determining highlights. The calculation for setting the reference value k is based on the photometric signal Pbl of each area.
~ Pb4 is performed automatically by manual input.

k is obtained by the above calculation, and following this calculation, for example, Pb
1-Pb4<k is calculated, and when k becomes 18V or more, it is determined that there is backlight, and a control signal Vc for controlling the gamma correction amount is supplied to the camera control circuit 31. Note that the photometry circuit 16 may be configured to perform various types of calculations other than those described above, and examples of other calculations will be described later.

On the other hand, as a result of calculating the discriminant value k, if it is determined that it is a highlight, then following this calculation, for example, Pb1-Pb4>k
When k becomes 28 V or more, it is determined that it is a highlight, and a control signal Vc for controlling the amount of gamma correction is supplied to the camera control circuit 3N.

Therefore, the control signal Vc has information for determining backlight and highlight by the series of calculations and for controlling the gamma correction amount. The camera control circuit 31 is composed of a microprocessor, and controls the gamma correction circuit 23 in response to the control signal Vc. A correction curve is formed.

That is, in a normal gamma correction circuit, r=0, denoted as C.
．． It is configured to perform gamma correction using a No. 45 gamma correction curve.

However, the gamma correction circuit 16 in this embodiment has a, b
A large number of gamma correction curves are formed as shown as Sd and e, and these gamma correction curves are configured to be automatically selected by the camera control section 31.

Assume now that the AE photometry section 16 determines that there is backlighting through the calculation, and supplies the camera control section 31 with a control signal Vc corresponding to the degree of backlighting.

The camera control unit 31 drives the gamma correction circuit 23 based on the control signal Vc, and selects a gamma correction curve dSe corresponding to the degree of backlighting. As a result, the gamma correction circuit 23
R, G with gamma correction from.

A B color signal is obtained and supplied to the matrix circuit 24 at the next stage.

Further, suppose that the AE photometry section 16 determines that it is a highlight by the calculation, and the control signal V corresponding to the degree of highlight is
Suppose that c is supplied to the camera control section 31. The camera control unit 31 drives the gamma correction circuit 23 based on the control signal Vc, and generates a gamma correction curve a corresponding to the degree of highlight.
, b. As a result, gamma-corrected R, G, and B color signals are obtained from the gamma correction circuit 23 and supplied to the matrix circuit 24 at the next stage.

By performing the above-mentioned gamma correction, the brightness of parts that were dark due to backlighting is corrected to become brighter, and, using FIG. 2 as an example, the brightness of person A is increased, resulting in a very easy-to-see image. Further, contrary to the case illustrated in FIG. 2, if person A is a highlight, the brightness of that part will be corrected to be darker.

Next, the gamma correction switching circuit 41 will be explained.

The gamma correction switching circuit 41 is configured to be capable of automatically selecting a gamma correction curve, standard selection (selection of gamma correction curve C), and further manually selecting an arbitrary gamma correction curve by operating a knob 42.

A control signal Ve for making each of the above selections is generated in accordance with the position setting of the knob 42, and the control signal Ve is supplied to the camera control section 31.

That is, when the knob 42 is set to Auto, the gamma correction switching circuit 41 supplies the control signal Ve to the camera control section 31 to make the automatic selection.

As a result, the camera control section 31 and the gamma correction circuit 23 perform the gamma correction as described above, in other words, automatically select a gamma correction curve, based on the control signal Vc supplied from the AE photometry section 16.

On the other hand, when the knob 42 is set to the standard gamma correction position (r=0.45) illustrated as "fixed", the automatic selection operation is stopped by the control signal Ve. Then, the camera control section 31 controls the gamma correction circuit 23 based on the control signal Ve, and selects the gamma correction curve C.

In this case, regardless of the control signal Vc obtained from the AE photometry section 16, gamma correction corresponding to the gamma correction curve C is performed.

By the way, if the photographer wants to strongly express the impression of clouds floating in the sky, for example, there is a limit to the expression if the gamma correction curve is automatically selected. Furthermore, even if the gamma correction is fixed at 0.45, there is a limit to the expression.

Therefore, in this embodiment, a desired gamma correction curve can be manually selected by operating the knob 42.

In other words, if you want to give a strong impression of clouds as described above, one method is to use the gamma correction curve a, which is easy to express the high brightness side.
, b.

In this case, gamma correction curves a and b are not necessarily selected by automatic selection, so operate the knob 42 to the position indicated as "large" and manually select gamma correction curves a and b. . The control signal Ve is based on the gamma correction curve a or b.
is supplied to the camera control unit 31 as a signal for selecting the gamma correction curve a or b, and the camera control unit 31 controls the gamma correction circuit 23 to select the gamma correction curve a or b.

When a gamma correction curve is manually selected as described above, gamma correction is performed based on the selected gamma correction curve regardless of the control signal Vc, and the desired photographing can be performed.

With respect to the above-mentioned photographing example, for example, there may be a case where it is desired to perform photographing that emphasizes a shaded part while not skipping a highlighted part. One method for performing such imaging is to set the gamma correction curve to γ=0.45 or less.

Since gamma correction curves c and d are not necessarily selected in automatic selection, the knob 42 is operated to the position shown as "small" and gamma correction curves c and d are arbitrarily selected.

The control signal Ve is supplied to the camera control section 31 as a signal for selecting the gamma correction curve C or d.
1 controls the gamma correction circuit 23 to create a gamma correction curve C1.
Or select d.

When a gamma correction curve is manually selected as described above, gamma correction is performed based on the selected gamma correction curve regardless of the control signal Vc, and the desired photographing can be performed.

Note that when the exposure correction is performed as described above, the gamma characteristic diagram during reproduction is as shown in FIG. 4(B). That is,
When gamma correction curve C is selected, the input-to-output relationship is approximately 1:1 as shown in C'. Furthermore, when the gamma correction curve dSe is selected corresponding to backlight, the input-to-output relationship is as shown in d' and e', and when the gamma correction curve aSb is selected corresponding to the highlight, The relationship between human power and output changes as shown in a' and b'.

When the entire characteristic is shifted by exposure correction, the entire characteristic is shifted up as shown by C'.

Next, other control systems related to the camera control section 31 will be explained.

The camera control section 31 has a central function of the camera, and is configured to perform various types of control in addition to the gamma correction control described above.

The lens 32, the light receiving element 33, and the AF distance measuring section 34 obtain distance data for autofocus, and supply data Vd measuring the distance to the main subject to the camera control section 31. The camera control unit 31 uses distance data Vd
A control signal for focusing is supplied to the lens driving section 35 based on the following.

The lens drive unit 35 drives a lens drive mechanism 36 composed of a pinion, a rack, etc. in response to the control signal, moves the lens 2 in the left and right direction in FIG. 1, and performs automatic focus adjustment.

Furthermore, the camera control section 31 drives the aperture drive section 37 to control the aperture mechanism 3 and perform optimal exposure control.

Further, the camera control section 31 performs various operations such as driving the CCD drive section 38 to control the image sensor 7 and performing a predetermined photographing operation.

Although one embodiment of the present invention has been described above, the present invention is not limited to the above, and various modifications are possible.

For example, in addition to the above calculations, the AE photometry section 16 calculates Pbl+Pb2-Pb4, Pbl+Pb2
+ P b3- P b4, further Pb2-Pb4, Pb
It may be configured to perform a comparison calculation between 3-Pb4 and the above to obtain the control signal Vc for performing gamma correction as described above.

Further, in the embodiment described above, the light receiving element 15 is provided to obtain the photometric signal vb, but the light receiving element 15 is deleted,
It is also possible to obtain the photometric signal vb based on the video signal obtained from the image sensor 7.

According to this configuration, since the light receiving element 15 is not required, there is an advantage that not only the circuit configuration becomes simple but also the mechanical structure can be simplified.

Furthermore, the following modifications regarding gamma correction are possible. That is, when changing the gamma correction curve as described above, it is necessary to adjust the white balance in accordance with the gamma curve. Therefore, when a camera is provided with a large number of gamma correction curves, the circuit load of the camera increases, but it may be desirable to reduce the circuit load even if the number of gamma correction curves is reduced.

Since gamma correction is often required in backlight situations and rarely in highlight situations, the control signal Vc may be obtained from the AE photometry section 16 during backlighting, and the gamma correction may be performed. Even with this configuration, even if the main subject is on the high-brightness side, that is, in a position corresponding to area P4 according to the embodiment, it will fall within the latitude and can be photographed and reproduced well.

In the above embodiment, a plurality of gamma correction curves are provided and selected automatically or manually.
It is not limited to this configuration.

For example, the gamma correction curve C may be normally formed, and the characteristics may be changed to other gamma correction curves in response to the control signals Vc and Ve.

It should be noted that although the above-described embodiment shows an example of application to an analog electronic still camera, the present invention can be used in a wide range of applications.

That is, it can be used for gamma correction of digital electronic still cameras. Digital electronic still cameras have
There is a device configured to perform gamma correction or the like on a video signal obtained from an image sensor in a preprocessing circuit, and is suitable for this preprocessing circuit.

Furthermore, it goes without saying that the present invention can be used in a gamma correction circuit for a VTR camera known as a video movie.

[Effects of the Invention] As explained above, according to the imaging device of the present invention, by providing the gamma correction switching circuit, it is possible to select and set an arbitrary gamma correction curve based on the shooting data of the subject or the intention of the photographer. It was configured so that it could be done.

Therefore, the photographer can arbitrarily select the gamma correction curve according to the subject or the photographed portion to be particularly emphasized, and can perform photographing with a variety of image expressions.

Also, even if you shoot under abnormal light such as backlight or highlights,
Shooting errors such as the main subject becoming too dark or too bright are reduced, and good shooting can always be performed.

Therefore, compared to the case where the selection of the gamma correction curve is automatic or fixed, the imaging device becomes multi-functional, and the usability of the imaging device becomes better and the added value is further improved.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of an electronic still camera showing an embodiment of the present invention, Fig. 2 is an explanatory diagram showing the photographing situation of a subject, Fig. 3 is an explanatory diagram showing multi-division of the subject, and Fig. 4 is an explanatory diagram showing the subject shooting situation. FIG. 4 is a gamma correction curve and a gamma correction characteristic diagram during reproduction. Reference numeral 1 in the figure: Photographing optical system 7: Image sensor 15: Light receiving element 16: AE photometry section 22: Color separation circuit 23: Gamma correction circuit 24: Matrix circuit 25: Encoder 31: Camera control section 41: Gamma correction switching Circuit 42; Knob Va: Color video signal b: Photometric signal Vc, Ve: Control signal A: Main subject Fig. 2

Claims (1)

[Scope of Claims] A gamma correction circuit configured to be able to arbitrarily set or select a desired gamma correction curve; An imaging device comprising a gamma correction switching circuit configured to perform gamma correction.