JPH02170782A - Image pickup device - Google Patents

Abstract

PURPOSE:To execute the multifunction of an image pickup device and the improvement of a usability by permitting a photographing person to discriminate a photographing situation, executing a necessary gamma correction, and simulta neously, displaying the situation of the gamma correction. CONSTITUTION:Based on the image pick-up data of a subject, a gamma correc tion curve is automatically selected, simultaneously, and by providing a gamma correction switching circuit 41 the switching from an automatic selection to a standard gamma correction is executed, and by a manual operation, the selec tion of the arbitrary gamma correction curve is executed. By providing a gam ma display part 43, the switching of the selective mode of the gamma correction curve is executed, and the selected gamma correction curve is displayed. Thus, the image pickup device can be made multifunctional, and simultaneously, the usability of the image pickup device can be made satisfactory.

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, and more particularly to an imaging device capable of displaying the selection status of a gamma correction curve. Regarding.

[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, ordinary users usually do not have special photographing techniques, and the photographing conditions vary widely.

Considering this background, it is desirable that the imaging device be designed so that general users can always take good pictures.

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 imaging device, and the exposure was compensated according to the main subject even under abnormal light as mentioned above. , it was possible to take pictures at appropriate exposure values.

[Problems to be Solved by the Invention] However, although conventional imaging devices include 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 amount of gamma correction, the above-mentioned photographing mistake may be made at a good photo opportunity.

Therefore, the present inventor investigated automatic selection of gamma correction 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.

Furthermore, there are times when you want to take a photo with a different impression by intentionally changing the exposure value without necessarily setting the exposure to the correct value. It is not possible to perform such diverse shooting.

In other words, by simply automatically selecting a gamma correction curve, it is difficult to perform various types of photography that match the photographer's preferences and the subject to be photographed.

Further, if the gamma correction curve is configured to be arbitrarily selected automatically or manually, if there are many types of gamma correction curves, there is a risk that the photographer may misidentify and confuse the current gamma correction curve.

Therefore, it is desired that the imaging device having the above configuration be improved in usability, such as being able to select gamma correction and displaying the selection status.

The present invention has been made in view of the above-mentioned circumstances, and its purpose is to allow the photographer to determine the shooting situation and perform the desired gamma correction, and also to display the gamma correction situation.
The objective is to improve the usability of an imaging device.

[Means for Solving the Problem] In order to achieve such an object, the present invention provides a gamma correction circuit with a plurality of selectable gamma correction curves, and automatically or manually selects a desired gamma correction curve. A gamma correction switching circuit for arbitrarily selecting a gamma correction curve is provided, and the gamma correction curve selection status by the gamma correction circuit is displayed.

[Function] In the present invention having such a configuration, the shooting situation is determined and the gamma correction curve is switched between automatic selection and manual selection, and when manual selection is made, the shooting situation, image expression, etc. In addition to being able to arbitrarily select a desired gamma correction curve in consideration of the above, it is also possible to display the selection status of the gamma correction curve.

Therefore, the photographer can perform various types of photography while checking the gamma correction curve during photography, and it is possible to increase the functionality of the imaging device and increase its added value.

[Example code] 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.
, half mirror 5, optical low-pass filter,
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 visually through the finder F, and forms a subject image on the light receiving element 15 to serve 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 by the preamplifier 21 to a desired voltage level.

The color separation circuit 22 obtains R (red), G (green), and B (blue) color signals. The color signals RSG 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 IJx circuit 24 receives the gamma-corrected color signal R.
, G, B, and performs predetermined signal processing based on the luminance signal Y.
1. Obtain color difference signals R-Y and B-Y.

Further, the color encoder 25 outputs a total color video signal (N
(TSC color video signal), further Y+5SR-Y,
Various signals such as B-Y are obtained, and these are supplied to a display device, a recording circuit, etc. (not shown), 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 PiSP2, P3, and P4 as shown in FIG. 3, when photographing the subject shown in FIG. In such a backlit situation, in which person A, the main subject, is located in areas P1 and bright background parts are located in areas P2, P3, and P4, in other words, under abnormal light conditions, the main subject, person A, is located in areas P2, P3, and P4. Area Pl corresponding to the position A has low brightness, and areas P2 to P4 that are divided and formed around the outside thereof have high brightness.

Therefore, from each area Pi-P4 of the light receiving element 15, a photometric signal vb with a level difference corresponding to the difference in brightness of each area is obtained. Photometric signal v obtained in this way
b is supplied to the AE photometry section 16, and the AE photometry section 16 performs the following noteworthy actions.

Here, for convenience of explanation, the photometric signals vb obtained from each area P1 to P4 are expressed as Pbl, Pb2, Pb3, respectively.
, Pb4.

Then, for example, a reference value k for determining backlight and highlight is determined from the calculated value of Pb4/Pbl. The calculation for setting the reference value k is based on the photometric signals Pbl to p of each area.
b4 is performed automatically by manual input.

Find k by the above calculation, and following this calculation, for example, tP
bl −Pb4< k (7) Calculate, k is IEV
When this occurs, it is determined that there is backlight, and a control signal Vc for controlling the amount of gamma correction 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
is calculated, and when k becomes 211'V or more, it is determined that it is a highlight, and a control signal V is used to control the gamma correction amount.
c is supplied to the camera control circuit 31.

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.The gamma correction circuit 16 has a large number of gamma correction curves as shown in FIG. It is formed.

That is, in a normal gamma correction circuit, γ=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 is aSb
, d, and e, a large number of gamma correction curves are formed, and these gamma correction curves are configured to be automatically and individually selected by the camera control section 31.

Assume now that the AE photometry section 16 determines that there is backlighting through the above 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 gamma correction curves d and e in accordance with the degree of backlighting. As a result, the gamma correction circuit 23
From this, gamma-corrected R, G, and B color signals are obtained and supplied to the matrix circuit 24 at the next stage.

Assume also that the AE photometry section 16 determines that the image is a highlight based on the calculation, and supplies the camera control section 31 with a control signal Vc corresponding to the degree of highlight.

The camera control unit 31 drives the gamma correction circuit 23 based on the control signal Vc, and selects the gamma correction curves a and b in accordance with the degree of highlight. As a result, gamma-corrected RSG 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 Aut◯, the gamma correction switching circuit 41 supplies the control signal Ve to the camera control unit 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 (γ=0.45) illustrated as "fixed", the automatic selection operation is stopped by the control signal Ve. and,
The camera control unit 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, the gamma correction is fixed at 0.45. However, there are limits to the above 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 that easily expresses the high brightness side.
, b.

In this case, since the gamma correction curve aSb is not necessarily selected by automatic selection, the knob 42 is operated to the position indicated as "large" and the gamma correction curve a1b is arbitrarily selected manually. The control signal Ve is supplied to the camera control section 31 as a signal for selecting the gamma correction curve a or b, and the camera control section 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 r=o, 45 or less.

In this case, gamma correction curves c and d are not necessarily selected by automatic selection, so the knob 42 is operated to the position indicated as "small" and gamma correction curve c1d is arbitrarily selected manually. The control signal Ve is supplied to the camera control section 31 as a signal for selecting the gamma correction curve C or d, and the camera control section 31 controls the gamma correction circuit 23 to select the gamma correction curve C or 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 becomes approximately 1:1 as shown by C'. Also, gamma correction curve d corresponds to backlighting.

When e is selected, the input-to-output relationship is d'.

When gamma correction curves a and b are selected corresponding to the highlight, the input-to-output relationship changes as shown in a/ and b/, as shown in e'.

Then, if the entire structure is shifted by exposure compensation, C'
As shown, the entire characteristic is shifted up.

Next, the gamma display section 43 will be explained.

When the gamma correction switching circuit 41 selects the gamma correction curve as described above, the gamma display section 43 displays the following information:
This displays the selection status.

The display content may be configured to display the above-mentioned Out◯, fixed, and manual switching, and to further improve the display content, for example, the gamma correction curve selected in manual mode may be displayed.

As the display means of the gamma display section 43, a light emitting element such as an LED may be used, and the display position is provided so as to be visible from the finder F, for example.

To explain the display position with reference to FIG. 2, suppose that the object shown in FIG. 2 can be seen through the finder (corresponding to F in FIG. 1). An LED is provided as a gamma display section 43 at the lower right corner of the subject, and is configured to light up when, for example, the standard gamma correction is switched to another gamma correction.

In FIG. 2, one LED is shown as the gamma display section 43, but in order to display the selection contents in more detail, two
More than one LED may be used.

Further, the selection contents of the gamma correction curve may be displayed by different colors emitted from the LEDs, and various types of display may be performed by combining colors.

Further, the display position of the gamma display section 43 is not limited to the finder F, and the display means is not limited to the LED.

For example, some camera bodies are provided with a liquid crystal panel for a camera operation section, and gamma display can be performed using the liquid crystal panel.

In this case, the gamma correction curve can be selectively displayed in more detail than the display using the LED.

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

The camera control B31 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 8 to control the image sensor 7 and perform 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 +
Pb3-Pb4, further Pb2-Pb4, Pb3-P
It may be configured to perform a comparison operation between b4 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 are advantages such as not only the circuit configuration being simplified but also the mechanical structure being 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, etc. according to the embodiment, it will be within the latitude and good photography can be performed.

Further, in the embodiment described above, the gamma display is performed using the output signal of the camera control section 31, but the display may be performed using the control signal Ve obtained from the gamma switching circuit 41.

Further, when displaying using a liquid crystal panel, the display method can be performed using characters, symbols, or a combination thereof.

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.

Some digital electronic still cameras are configured to perform gamma correction or the like on a video signal obtained from an image sensor in a preprocessing circuit, and are 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, a gamma correction curve is automatically selected based on the imaging data of the subject, and a gamma correction switching circuit is provided to switch from automatic selection to standard gamma correction. In addition to manually selecting an arbitrary gamma correction curve, a display means is provided to switch the gamma correction curve selection mode and display the selected gamma correction curve.

Therefore, the photographer can arbitrarily select a gamma correction curve according to the subject or the photographed part that he or she particularly wants to emphasize, and can take photographs with a variety of image expressions.

Furthermore, since the selection of the gamma correction curve is displayed, the photographer can accurately and easily understand the gamma correction during shooting, and it is possible to reduce shooting errors due to misidentification and confusion.

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 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 Two gamma correction circuits 24: Matrix circuit 25: Encoder 31: Camera control section 41: Gamma correction switching Circuit 42 Nip 43: Gamma display section Va: Color video signal Vb: Photometric signal Vc, Ve: Control signal A: Main subject F: Finder Fig. 2 Fig. 3

Claims (1)

[Scope of Claims] A gamma correction circuit configured to automatically select any one of a plurality of gamma correction curves and to arbitrarily select a desired gamma correction curve; a gamma correction switching circuit that acts on the correction circuit to switch the selection of a plurality of gamma correction curves provided in the gamma correction circuit between an automatic selection mode and a manual selection mode, and selects a desired gamma correction curve in the manual selection mode; An imaging device comprising: a display means for displaying a selection status of a gamma correction curve in the gamma correction circuit.