JP2003143486A - Image pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image pickup device for which efficient countermeasure are taken against smear. SOLUTION: The device has an image pickup element 105, a photographing surface illuminance adjusting means 103 for adjusting the illuminance of an object image with respect to the photographing surface of the element 105, exposure control means 112, 117, and a smear detecting means 112a for detecting the generation of smears concerning to photographing signals on the basis of output of the element 105. The means 112, 117 are constituted so as to lower the illuminance of the object image by the means 113 when the means 112a detects the generation of smears in a moving image state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup apparatus, and more particularly to a smear countermeasure for the image pickup apparatus.

[0002]

2. Description of the Related Art In an image pickup device using a solid-state image pickup device such as a CCD, various measures have been devised in order to prevent pseudo signals such as smear and blooming due to a high-brightness subject (generally referred to as smear). Has been put into practical use. For example, for still image shooting, pixel unit (photoelectric conversion storage unit)
After the charge is transferred from the vertical transfer path to the vertical transfer path, it is possible to prevent the pseudo signal from being transferred in the vertical direction by shielding the light using a mechanical shutter or the like and then starting the vertical transfer. It is possible to prevent vertical stripes from being displayed on the screen, and it is possible to avoid smear almost completely.

On the other hand, in the moving image state such as the electronic viewfinder function of the still image camera, it is extremely difficult to shield the light as described above. This is because continuous mechanical shutter driving is difficult, and even if mechanical shutter driving can be performed, exposure is not possible during the light-shielding period and only intermittent output can be obtained. Therefore, reducing the illuminance on the board by narrowing down
In fact, it is the only countermeasure that can be taken.

In the case of a movie camera dedicated to shooting moving images, it is common sense that the aperture is always driven. Therefore, the exposure control program tends to be narrowed down (a diaphragm that gives the same exposure amount). The one with a smaller aperture can be selected from the combination of the value and the exposure time. However, the movie state (electronic state) in a still camera (digital still camera, etc.) mainly configured for still image shooting. The situation is different regarding the video state that is used as an auxiliary because of the viewfinder function and the like.

That is, in a still camera, it is desirable to use an exposure control mechanism optimized for still image photography, so that, for example, "power consumption during driving (when changing aperture value) is relatively large". In many cases, a property that is unsuitable for continuous driving at all times occurs as a constraint, such as "only a stepwise aperture value is available and continuous value control is not possible". Therefore, in a moving image state of a still image camera, the aperture is generally fixed at the open position, which causes a problem that smear often occurs in high-luminance shooting. Although this problem was allowed for the time being because the moving image function of the still image camera is an auxiliary specification, it is still unsightly and harmful,
Improvement was desired.

[0006]

As described above, in the conventional image pickup apparatus, the countermeasure against smear such as the occurrence of smear in the moving image state is insufficient.

The present invention has been made to solve the above-mentioned conventional problems, and an object thereof is to provide an image pickup apparatus in which an effective countermeasure against smear is taken.

[0008]

An image pickup apparatus according to the present invention includes an image pickup element, an image pickup surface illuminance adjusting means for adjusting the illuminance of a subject image with respect to the image pickup surface of the image pickup element, an exposure control means, and the image pickup element. And a smear detecting means for detecting the occurrence of smear with respect to an image pickup signal based on the output of the exposure control means, and the exposure control means adjusts the illuminance of the imaging surface when the smear detecting means detects the occurrence of smear in a moving image state. It is configured to reduce the illuminance of the subject image by means.

A preferred mode of the image pickup device is as follows.

The exposure control means is configured to perform the exposure control by adjusting the charge storage time when the charge storage time of the image pickup device has not reached the end of the predetermined adjustment range.

The smear detection by the smear detecting means is performed by recognizing a smear pattern in the image pickup signal.

The smear detection by the smear detecting means is performed based on the special image pickup signal obtained by temporarily switching the driving state of the image pickup device to the special drive state for smear detection.

In the special driving state, the output of the charge transfer pulse for transferring the charge from the pixel portion of the image pickup device to the vertical transfer path is stopped.

In the special drive state, the charge storage time of the image pickup device is made different from that in the normal drive state.

A buffer memory means for storing the image pickup signal, and for the period when the special image pickup signal is outputted from the image pickup device, the image pickup signal outputted in the immediately preceding period is outputted from the buffer memory means. Configured for alternate output.

Further, in the image pickup apparatus according to the present invention, the image pickup element, the smear detecting means for detecting the occurrence of smear with respect to the image pickup signal based on the output of the image pickup element, and the smear detecting means for detecting the occurrence of smear. And a warning means for giving a warning in some cases.

[0017]

DETAILED DESCRIPTION OF THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

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

Reference numeral 101 is a photographing lens system including various lenses, 102 is a lens driving mechanism for driving the lens system 101, 103 is an exposure control mechanism including an aperture and a shutter, 104 is a filter system such as an optical low-pass filter, and 105. Is a CCD color image pickup device, 106 is a CCD driver for driving the image pickup device 105, and 107 is a CD
A pre-process circuit including S, A / D conversion and the like, 108 a digital process circuit for performing various digital processes (including a buffer memory for storing imaging signals, etc.), 109 a card interface, 110 a memory card, 11
Reference numeral 1 is an LCD image display system having a moving image display function.

Reference numeral 112 denotes a system controller (mainly a CPU) for integrally controlling each section, 113 an operation switch system including various switches such as a release switch, and 114 an operation display for displaying an operation state, a mode state and the like. Reference numeral 115 is a strobe, 116 is a lens driver for driving the lens driving mechanism 102, 117 is an exposure control driver for controlling the exposure control mechanism 103 and the strobe 116, and 118 is an EEPROM (various control information and the like) stored therein. Non-volatile memory).

As described above, the basic configuration and function of the digital still camera of this embodiment are the same as those of a general digital still camera, but this digital still camera has a smear detection function for detecting the occurrence of smear ( Mainly system controller 112 and digital process circuit 1
The function realized by the image pickup control and data analysis in 08: etc .: In the drawing, the system controller 112 has a smear detecting means 112a). When the smear is detected, the system controller 11
In response to an instruction from 2, the aperture of the exposure control mechanism 103 (image pickup surface illuminance adjusting means) is controlled via the exposure control driver 117 to adjust the illuminance of the image pickup surface of the CCD image pickup device 105, and the warning unit 119 controls the smear. It is possible to warn of the occurrence.

FIG. 2 is a flowchart showing the exposure control operation in the moving picture state of the digital still camera of this embodiment, that is, the operation when the moving picture is displayed by the LCD image display system 111 or the like.

First, it is determined whether or not smear is detected by the smear detection method described later, that is, whether or not the smear flag is "1" (SmF = 1) (S).
1). When the smear is detected, it is judged whether or not the diaphragm is in the minimum diaphragm state (S2), and when it is not in the minimum diaphragm state, the diaphragm value is increased by one stage (a further narrowed state). That is, by increasing the aperture value, the illuminance on the image pickup surface of the image pickup device 105 is reduced so that smear does not occur (or the smear is weakened) (S3).

If smear is not detected in step S1 (SmF = 0), whether the exposure amount (Exp: the average photometric value based on the output of the image sensor 105) exceeds a predetermined threshold value (Ethh). It is determined whether or not (whether it is overexposed) (S4). If Exp> Ethh, it is determined whether or not the shutter (element shutter) is set to the maximum speed. That is, the charge storage time of the image sensor 105 can be adjusted (scheduled adjustment range).
It is determined whether or not the minimum time is set in (S5). If the shutter speed is set to the maximum speed, the process proceeds to step S2. If the shutter speed is not set to the maximum speed, the shutter speed is increased by one stage (a faster speed) to reduce the exposure. (S
6).

If Exp> Ethh is not satisfied in step S4, it is determined whether Exp is lower than a predetermined threshold value (Ethl: where Ethl <Ethh) (whether underexposure or not) (S7). ). If Expp <Ethl, it is determined whether or not the shutter (element shutter) is set to the lowest speed. That is, the image sensor 105
It is determined whether the charge storage time of is set to the maximum time in the adjustable range (scheduled adjustment range) (S
8). If the shutter is not set to the lowest speed,
The exposure is increased by reducing the shutter speed by one step (a state in which the shutter speed is further delayed) (S9). When the shutter is set to the lowest speed, it is determined whether or not the aperture is in the open aperture state (S10), and when it is not in the open aperture state, the aperture value is lowered by one step (more open state). (S11).

By repeatedly passing through the control loop of FIG. 2 explained above, the exposure control state of proper exposure in which the occurrence of smear is suppressed is finally reached and stabilized.

As described above, according to this embodiment, when the smear is detected, the diaphragm is driven to reduce the illuminance on the image pickup surface of the image pickup device (the illuminance of the subject image). In the above, deterioration of display quality due to smear can be suppressed. And then, even if the smear disappears (if the exposure is proper), the aperture is opened (increased illuminance).
Since there is no movement, diaphragm drive is minimized. Further, during the exposure adjustment, the exposure control by the shutter is prioritized over the aperture, so that the drive of the aperture can be minimized.

FIG. 3 is a flow chart showing the basic operation in smear detection (how to set the smear flag (SmF)).

When the smear is not detected, the smear flag is "0" (SmF = 0) (S2).
1). The smear detection operation (smear calculation operation) is performed for each frame (S22), and it is determined whether the calculated value (Sm) is larger than a predetermined threshold value (Sth) (S22).
23) If it is larger (Sm> Sth), the smear flag is set to "1" (SmF = 1) (S24).

In the above, the operation timing of smear detection is set for each frame, but the timing may be limited to this depending on the detection method. Further, in consideration of a typical aperture driving time and the like, in many cases, smear detection timing may be significantly thinned out from the above. Needless to say, including such cases, the smear detection operation timing is appropriately set as necessary, and individual correspondence description in each of the following examples will be omitted.

Hereinafter, some specific methods of smear detection (smear calculation) will be described with reference to FIGS. 4 to 6.

First, referring to FIG. 4, the first smear detection is performed.
The method will be described. This method performs smear detection by recognizing a smear pattern obtained based on an image pickup signal.

FIG. 4A schematically shows a state in the image pickup plane of the image pickup device. The spot area indicated by the black circle in the figure (here, the horizontal width of the spot area is W
h, the width in the vertical direction is Wv) indicates a region where the light intensity is high and the photoelectric conversion signal is saturated. In the vertical direction including this spot region, smear is generated due to vertical transfer of excess charges. , It is recognized as a bright vertical stripe on the display screen.

The recognition of the smear pattern starts by detecting the spot area. That is, the saturated pixel area is extracted from the pixel data of the entire screen. Of these, pixel data that are adjacent to each other are all handled as one area. Any one or a plurality of regions (including isolated pixels) obtained by such processing can be regarded as a spot region. However, in order to simplify the processing, the area (the number of constituent pixels) is the maximum in this embodiment. One area is selected, and this is detected as a spot area. As described above, when smear occurs, vertical stripes are generated in the pixel regions above and below this spot region by being superimposed on the original image data.

Therefore, smear detection can be performed by comparing the signal levels of the area having the width Wh and the area horizontally adjacent to the area having the width Wh. However,
Since not only the spot area itself but also the area other than the smear component such as blooming may be included in the area near the spot area, the area (here, horizontal 2Wr vertical 2Wv, which is twice the width of the spot area) is used. The area) is a non-detection target area of the smear component, and the other upper and lower areas (areas A and B shown by hatching in the figure) are the smear component detection symmetrical areas.

FIG. 4B shows the signal level in this detection symmetrical region, and there is a difference in signal level between the region A and the region B. In this example, the average value Av {A} of the signal levels in the region A and the average value Av {B} of the signal levels in the region B
Sm is calculated as the smear calculated value Sm (Sm = Av {A} -Av
{B}), smear detection is performed depending on whether the calculated value Sm is larger than a predetermined threshold value Sth.

According to the first smear detecting method, it is not necessary to use special driving of the image pickup device as in the other methods described later, and therefore, the obtained moving image is not adversely affected.

Next, referring to FIG. 5, the second smear detection is performed.
The method will be described. The basic concept of this method is to temporarily switch the drive state of the image sensor to a special drive state for smear detection and perform smear detection based on the special image pickup signal obtained by this method. The output of the charge transfer pulse is stopped in the driving state.

In FIG. 5, TG represents a charge transfer pulse, and the charge transfer pulse causes charge transfer from the pixel portion of the image sensor to the vertical transfer path. Therefore,
This charge transfer pulse substantially ends the exposure period. VSUB is a charge sweep pulse for discarding charges from the pixel portion to the semiconductor substrate, and the time when the last charge sweep pulse occurs is substantially the start time of the exposure period. φVH is a comprehensive representation of the drive pulses of the vertical and horizontal transfer paths, and the charge transfer pulse TG
Shows a read period for one frame of the charges transferred to the vertical transfer path.

In this example, the charge transfer pulse TG is not output in the special driving state, and smear detection is performed based on the special image pickup signal (special output) obtained at that time. That is, in the normal driving state in which the charge transfer pulse TG is output, the charges accumulated in the pixel portion are read out through the vertical transfer path and the smear component is also superimposed at that time, but in the special driving state, Since the accumulated charges are not transferred to the vertical transfer path, the signal read out from the vertical transfer path (special imaging signal) shows only the smear component. Therefore, in this example, the value C of the special image pickup signal obtained in the special drive state (the average value or the maximum value of the special image pickup signal) is set as the smear calculated value Sm (Sm = C), and the calculated value S
Smear detection is performed depending on whether or not m is larger than a predetermined threshold value Sth.

According to the second smear detecting method, only the smear component can be detected without being affected by the electric charge accumulated in the pixel portion, that is, the subject image component, and therefore, there is no risk of erroneous detection.

Next, referring to FIG. 6, the third smear detection is performed.
The method will be described. Similar to the second method described above, the basic concept of this method is to temporarily switch the drive state of the image sensor to the special drive state for smear detection, and perform smear detection based on the special image pickup signal obtained at that time. However, in this example, the charge storage period in the special drive state is made different from the charge storage period in the normal drive state.

In the example shown in FIG. 6, in the special drive state,
By delaying the end time of the charge sweep-out pulse VSUB, the exposure period (charge accumulation period) is reduced to 1 / n of the normal exposure period.
2 Therefore, at that time, the value of the special image pickup signal read from the vertical transfer path is D (the average value or the maximum value of the special image pickup signal), the signal value in the normal state is E, and the smear component equally included therein is Sm. Then, since E = Ss + Sm D = Ss / 2 + Sm, the smear component Sm is calculated as Sm = 2D−E. The calculated value Sm is a predetermined threshold S
Smear detection can be performed depending on whether it is larger than th.

According to the third smear detecting method, it is possible to detect only the smear component by removing the influence of the electric charge accumulated in the pixel portion, that is, the subject image component by calculation, and therefore the risk of erroneous detection is small.

When the second and third smear detection methods shown in FIGS. 5 and 6 are applied, by performing special driving, a frame in which the special imaging signal is output instead of the normal imaging signal is output. Occurs. Therefore, in such a frame, the image pickup signal output in the immediately preceding frame is used. Specifically, the image pickup signal of the immediately preceding frame stored in the buffer memory in the digital process circuit 108 shown in FIG. 1 is used instead of the special image pickup signal. By taking such measures, it is possible to secure a natural moving image even if special driving for smear detection is performed.

Further, particularly in the case of the third smear detection method,
Since the image signal is obtained even for a frame of 1/2 of the normal exposure period, the buffer memory is used by setting the gain to double for the image signal of this frame in the circuit in the subsequent stage, for example. Therefore, it is possible to secure a natural moving image without any loss of image information.

In the embodiment described above, the diaphragm is automatically adjusted when smear is detected.
The aperture may be fixed, for example, when the camera is set to manual mode. Therefore, in such a case, a warning indicating that the smear has been detected may be issued. Specifically, in the flowchart shown in FIG. 3, a warning may be given when the smear flag SmF becomes “1”. In this way, by issuing a warning when smear is detected, when the camera is set to manual mode, the user himself adjusts the aperture to prevent the deterioration of display quality due to smear. You can

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the invention. Furthermore, the embodiments include inventions at various stages, and various inventions can be extracted by appropriately combining the disclosed constituent features. For example, even if some constituents are deleted from the disclosed constituents, any invention can be extracted as an invention as long as a predetermined effect can be obtained.

[0049]

According to the present invention, when the smear is detected, a predetermined process is performed to prevent the display quality from being deteriorated due to the smear.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration example of an image pickup apparatus according to an embodiment of the present invention.

FIG. 2 is a flowchart showing an operation example of the image pickup apparatus according to the embodiment of the present invention.

FIG. 3 is a flowchart showing an operation example of smear detection in the image pickup apparatus according to the embodiment of the present invention.

FIG. 4 is an explanatory diagram showing an example of a smear detection method in the image pickup apparatus according to the embodiment of the present invention.

FIG. 5 is a timing chart showing another example of the smear detection method in the image pickup apparatus according to the embodiment of the present invention.

FIG. 6 is a timing chart showing still another example of the smear detection method in the image pickup apparatus according to the embodiment of the present invention.

[Explanation of symbols]

101 ... Photographic lens system 102 ... Lens drive mechanism 103 ... Exposure control mechanism 104 ... Filter system 105 ... CCD image sensor 106 ... CCD driver 107 ... Preprocess circuit 108 ... Digital process circuit 109 ... Card interface 110 ... Memory card 111 ... LCD image display system 112 ... System controller 113 ... Operation switch system 114 ... Operation display system 115 ... Strobe 116 ... Lens driver 117 ... Exposure control driver 118 ... EEPROM 119 ... Warning part

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 5C022 AA13 AB12 AB17 AB52 AC18                       AC42 AC69                 5C024 BX01 CX12 CX13 CX51 DX04                       GY01 GY25 HX57

Claims (8)

[Claims] 1. An image pickup element, an image pickup surface illuminance adjusting means for adjusting the illuminance of a subject image on the image pickup surface of the image pickup element, an exposure control means, and a smear generation for an image pickup signal based on an output of the image pickup element. And a smear detecting means for detecting, wherein the exposure control means, when the smear detecting means detects the occurrence of smear in a moving image state, to reduce the illuminance of the subject image by the imaging surface illuminance adjusting means. An image pickup device characterized by being configured. 2. The exposure control means, when the charge storage time of the image pickup device has not reached the end of a predetermined adjustment range,
The image pickup apparatus according to claim 1, wherein exposure control is performed by adjusting the charge storage time. 3. The image pickup apparatus according to claim 1, wherein the smear detection by the smear detection means is performed by recognizing a smear pattern in the image pickup signal. 4. The smear detection in the smear detecting means is performed based on a special image pickup signal obtained by temporarily switching the drive state of the image pickup device to a special drive state for smear detection. The image pickup apparatus according to claim 1, wherein the image pickup apparatus is an image pickup apparatus. 5. The image pickup according to claim 4, wherein in the special drive state, output of a charge transfer pulse for transferring charges from a pixel portion of the image pickup device to a vertical transfer path is stopped. apparatus. 6. The image pickup apparatus according to claim 4, wherein in the special drive state, the charge storage time of the image pickup element is different from that in the normal drive state. 7. A buffer memory means for storing an image pickup signal, wherein the image pickup signal outputted in a period immediately before said special image pickup signal is outputted from said image pickup element, said buffer memory means. 7. The image pickup apparatus according to claim 5, wherein the image pickup apparatus is configured so as to substitute the output. 8. An image pickup element, a smear detecting means for detecting the occurrence of smear with respect to an image pickup signal based on the output of the image pickup element, and a warning means for giving a warning when the smear detecting means detects the occurrence of smear. An image pickup apparatus comprising: