JP2005341074A - Imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a blur prevention preference mode and an image quality preference mode at the time of flashing inhibition. <P>SOLUTION: In a camera comprising a CCD 12 performing photoelectric conversion of an object image, a shutter drive circuit 18 for controlling the storage time of charges being stored therein, an AGC 14 for controlling the gain of a signal converted by the CCD 12, and a signal processing circuit 15 outputting an imaging signal 17 and the luminance detection value 19 of the object, a blur prevention preference mode, e.g. "blur reduction flashing inhibition (up to 1/30 sec)", for controlling exposure through gain control is set at the flash mode set key of an external operating section 20 as a mode when the luminance detection value 19 lowers below a predetermined level in addition to a conventional flash mode. When the luminance detection value lowers below the predetermined level, exposure is controlled appropriately through gain control of the AGC 14 while keeping shutter speed at 1/30 sec and an appropriate blur-free image is obtained. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an imaging apparatus having a camera shake reduction unit.

  In a camera, camera shake may occur when shooting at a shutter speed slower than the shutter speed (shutter opening period) roughly determined by the reciprocal of the focal length of the taking lens. When the flash automatically emits light to prevent camera shake, the shutter speed, which is roughly determined by the reciprocal of the focal length of the photographing lens, is a standard for low-brightness automatic emission of flash emission. For example, when the focal length converted to 35 mm on the wide-angle side is 30 mm, the flash fires automatically when the shutter speed is 1/30 seconds, and when the focal length converted to 35 mm on the telephoto side is 90 mm, the flash automatically becomes 1/90 seconds. Many cameras are set to emit light.

When shooting a dark subject without flash emission, the shutter speed for obtaining appropriate exposure is often slower than the shutter speed roughly determined by the reciprocal of the focal length of the taking lens. An apparatus is disclosed in which the minimum shutter speed exposure value is increased from the reference when the film sensitivity (ISO sensitivity) is higher than the reference (see, for example, Patent Document 1).
Japanese Patent No. 2868270.

A digital still camera or the like can reduce camera shake if the ISO sensitivity is raised, but a beginner such as a digital still camera often does not know that camera shake can be reduced if the ISO sensitivity is increased. In many cases, the ISO sensitivity is not even known.
Cameras that perform camera shake correction using camera shake sensors have also been released, but the camera shake correction mechanism is complex, large in scale, high in cost, and unsuitable for camera miniaturization.

  The present invention has been made in view of such a problem, and in a shooting situation in which camera shake may occur, the setting of the device can be easily changed to reduce camera shake, and there is little camera shake without missing a photo opportunity. An object of the present invention is to provide an imaging apparatus that can capture an image.

  According to the first aspect of the present invention, there is provided a conversion means for photoelectrically converting an image of a subject, an accumulation time control means for controlling an accumulation time of charges accumulated in the conversion means, and a gain of a signal converted by the conversion means. In an imaging apparatus comprising a gain control means for controlling and a means for detecting the brightness of the subject, a mode in which exposure control is performed by the gain control as a mode when the brightness detection value of the brightness detection means falls below a predetermined value (Hereinafter referred to as a camera shake prevention priority mode) and a mode for performing exposure control by the accumulation time control (hereinafter referred to as an image quality priority mode).

  When the camera shake prevention priority mode is set, the gain level is controlled in preference to the accumulation time control, so that the signal level is appropriately maintained even when the shutter opening time is fixed to the minimum value for preventing camera shake. In addition, when the image quality priority mode is set, the signal level is appropriately maintained because the accumulation time is controlled in preference to the gain control.

  The invention according to claim 2 is characterized in that the camera shake prevention priority mode and the image quality priority mode can be selected when the flash emission is prohibited in claim 1.

  According to the present invention, the camera-shake prevention priority mode and the image quality priority mode can be selected when the flash emission is prohibited, so that it is easy to shoot even in a shooting situation where the device cannot be fixed with a tripod or the like and camera shake may occur. The device setting can be changed to the camera shake prevention priority mode, and an image with less camera shake can be taken without missing a photo opportunity. If the camera is fixed to a tripod and there is no risk of camera shake, an image with less noise can be taken by selecting the image quality priority mode.

Further, in a place where flash emission is prohibited in a room such as a museum, shooting with less camera shake is possible if shooting is performed with the camera shake prevention priority mode selected.
When shooting with a flash in a room under fluorescent light, the white balance of the subject to which the flash is lit is normal, but the white balance is not normal and the image is reddish, for example, on a wall beyond the distance that the flash can reach It may become. In that case, if the flash emission is prohibited and the camera shake prevention priority mode is set, an image with a normal white balance of the entire screen can be taken.

  In addition, when shooting a moving subject, if the camera shake prevention priority mode is set, the shutter speed is increased, so that a good image can be taken with not only camera shake but also motion without stopping the subject itself.

  In an imaging apparatus such as a digital camera, the shutter speed is roughly determined by the reciprocal of the focal length of the taking lens when the flash emission is prohibited at low brightness, etc. (shutter opening period, for example, 1/30 second on the wide angle side) ) Is the lowest speed, and in order to reduce camera shake at further low brightness, as shown in FIG. 2A, only the AGC sensitivity (ISO sensitivity) is controlled (hereinafter referred to as camera shake prevention priority mode), and the ISO sensitivity is A mode for controlling the shutter speed as shown in FIG. 3B (hereinafter referred to as image quality priority mode) up to the lowest shutter speed (for example, 2 seconds) determined by the device specifications is provided.

  The ISO sensitivity control is to control the gain of a signal obtained by photoelectrically converting the subject image, and the shutter speed control is to control the charge accumulation time when the subject image is photoelectrically converted. .

  For switching between the camera shake prevention priority mode and the image quality priority mode, a method of switching using a menu or the like or a method of switching using a shooting mode is used. Further, for example, it is possible to determine the camera shake prevention priority mode in the auto shooting mode and the image quality priority mode in the program shooting mode.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram illustrating a configuration of an imaging apparatus according to the present invention. The imaging apparatus 1 performs sampling and holding of a signal obtained by photoelectric conversion, a lens unit 11 that images a subject, a photoelectric conversion element (hereinafter, CCD) 12 that photoelectrically converts incident light from the lens unit, and the like. A sampling / hold circuit (hereinafter referred to as S / H circuit) 13, a variable gain amplifier (hereinafter referred to as AGC circuit) 14 for adjusting the gain of the signal, and a signal processing circuit 15 for obtaining a video signal are provided. These units and circuits are controlled in an integrated manner by the control unit 16. The imaging apparatus 1 further includes a shutter drive circuit 18 that is controlled by the control unit 16 and adjusts the charge accumulation time of the CCD 12. In FIG. 1, solid lines a, b, and c indicate incident light from an object and photoelectrically converted incident light signals, and broken lines d, e, f, and g indicate control signals. A broken line h from the external operation unit 20 to the control unit 16 indicates a setting signal.

  Incident light from the subject is electrically accumulated in the CCD 12 via the lens 11. A signal indicating a subject image photoelectrically converted by the CCD 12 is subjected to a double interlayer correlation sampling process in the S / H circuit 13 to reduce noise in the accumulated charge of the CCD 12. The signal subjected to the sampling process is sent to the AGC circuit 14 to adjust the signal level. The signal indicating the image of the subject whose level has been adjusted is subjected to camera signal processing in the signal processing circuit 15 and becomes a video signal 17 of the subject. Further, the signal processing circuit 15 has a function as a luminance detecting means for detecting the luminance of the subject.

  The control unit 16 obtains a luminance detection value 19 detected by the signal processing circuit 15, and performs shutter driving to adjust the gain control of the signal in the AGC circuit 14 and the accumulation time in the CCD 12 in accordance with the detection value (luminance value). The exposure is appropriately controlled by controlling the circuit 18. Here, the exposure control by adjusting the charge accumulation time in the CCD 12 can be considered as control of the shutter opening time. Control of the AGC circuit 14 and the shutter drive circuit 18 is performed based on the mode set by the external operation unit 20.

  The external operation unit 20 is provided with a flash mode setting key (not shown). As shown in FIG. 4, in addition to the conventional flash mode (see FIG. 5), the flash mode setting key is used to set the minimum shutter speed in the flash prohibition mode called “camera shake reduction flash prohibit mode (˜30 seconds)”. Set the anti-shake priority mode to limit to 1/30 seconds. FIG. 4 shows the toggle operation of the flash mode setting key in the present invention, and FIG. 5 shows the toggle operation of the conventional flash mode setting key. As a different setting method from the above, the minimum shutter speed when the strobe light emission is prohibited may be selected from a menu or the like. Note that the image quality priority mode is set when the flash mode setting key “prohibit light emission (˜2 seconds)” (see FIG. 4) is set.

  Hereinafter, control examples of the camera shake prevention priority mode and the image quality priority mode of the imaging apparatus 1 will be described.

  FIG. 2 shows exposure control and accumulation time control by gain control according to brightness in the camera shake prevention priority mode in which the flash mode setting key of the external operation unit 20 is set to “camera shake reduction light emission prohibition (˜1 / 30 second)”. In other words, the relationship between the exposure control by the above, that is, the exposure control in the AGC circuit 14 and the exposure control by the shutter opening time is shown.

  When the “handshake reduction light emission prohibition (˜1 / 30 second)” mode is set in the external operation unit 20, the control unit 16 detects that the luminance of the subject detected by the signal processing circuit is equal to or lower than a predetermined luminance level (A). The shutter drive circuit 18 outputs a control signal for setting the shutter open time to a minimum of 1/30 second without camera shake, and the AGC circuit 14 increases the gain in accordance with the decrease from the luminance level (A) to achieve proper exposure. The camera shake prevention priority mode that outputs the control signal is controlled. When the luminance is below a predetermined luminance level (A) by the control in the camera shake prevention priority mode, exposure is performed by gain control (ISO sensitivity control) of the AGC circuit 14 with the shutter opening time 1/30 seconds as shown in FIG. Is properly controlled. At a predetermined luminance level (A) or higher, the control unit 16 controls the shutter drive circuit 18 according to the luminance. As a result, as shown in FIG. 2B, exposure control is performed according to the shutter opening time by adjusting the accumulation time in the CCD 12.

  FIG. 3 shows exposure control by gain control according to brightness and exposure control by accumulation time control in the image quality priority mode in which the flash mode setting key of the external operation unit 20 is set to “emission prohibition (˜2 seconds)”. The relationship between the exposure control in the AGC circuit 14 and the exposure control by the shutter opening time is shown.

  When the mode of “prohibit light emission (˜2 seconds)” is set in the external operation unit 20, the control unit 16 performs control in an image quality priority mode that controls the shutter drive circuit 18 according to the luminance of the subject detected by the signal processing circuit. To do. In this image quality priority mode, as shown in FIG. 3B, exposure control is performed at a predetermined luminance level (A) or lower based on the shutter opening time, and gain control in the AGC circuit 14 is performed as shown in FIG. Not.

  In the above-described embodiments, the case where the minimum shutter speed in the camera shake prevention priority mode is set to the shutter speed that is roughly determined by the reciprocal of the focal length of the photographing lens is described. However, the present invention is not limited to this. If the lowest shutter speed in the prevention priority mode is set to 1/2, 1/3, etc. of the shutter speed roughly determined by the reciprocal of the focal length of the photographing lens, camera shake can be further prevented.

  Furthermore, in the above-described embodiment, the case where the minimum shutter speed in the camera shake prevention priority mode is set to be a shutter speed that is roughly determined by the reciprocal of the focal length of the photographing lens is described, but the present invention is not limited thereto. For example, the user can select the shutter speed, which is roughly determined by the reciprocal of the focal length of the photographing lens, 1/2, 1/3, etc., from the menu etc. Also good.

  Furthermore, in the above-described embodiments, the case has been described in which the minimum shutter speed in the camera shake prevention priority mode is set to the shutter speed that is roughly determined by the reciprocal of the focal length of the photographing lens. When shooting a subject having a blur, since the subject itself is moving as well as camera shake, there is a possibility that a blurred image may be shot, and there is a case where it is desired to increase the shutter speed. In order to increase the shutter speed, the user can select the shutter speed, which is roughly determined by the reciprocal of the focal length of the photographing lens, and 1/2, 1/3, etc., from the menu etc. You may do it.

  Furthermore, in the above-described embodiments, the case where the minimum shutter speed in the camera shake prevention priority mode is set to the shutter speed that is roughly determined by the reciprocal of the focal length of the photographing lens has been described. When shooting with the aperture stopped in the priority mode or the like, the shutter speed becomes slow and camera shake may occur. Therefore, when shooting in the aperture priority mode or the like, the camera shake prevention priority mode and the image quality priority mode may be provided.

1 is a block diagram illustrating a configuration of an imaging apparatus according to an embodiment of the present invention. (A) is a diagram showing the relationship between the luminance level and AGC in the camera shake prevention priority mode, and (b) is a diagram showing the relationship between the luminance level and the shutter opening time (shutter speed). (A) is a diagram showing the relationship between the luminance level and AGC in the image quality prevention priority mode, and (b) is a diagram showing the relationship between the luminance level and the shutter opening time (shutter speed). Explanatory drawing of toggle operation of the flash mode setting key in this invention. Explanatory drawing of toggle operation of the conventional flash mode setting key.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Imaging device 11 ... Lens part 12 ... Photoelectric conversion element (CCD), 13 Sampler / hold circuit, 14 ... Gain variable amplifier (AGC circuit), 15 ... Signal processing circuit, 16 ... Control part, 18 ... Shutter drive Circuit, 19 ... detection value of luminance, 20 ... external operation unit.

Claims (2)

Conversion means for photoelectrically converting an object image;
Accumulation time control means for controlling the accumulation time of charges accumulated in the conversion means;
Gain control means for controlling the gain of the signal converted by the conversion means;
In the imaging apparatus provided with the means for detecting the luminance of the subject,
As a mode when the luminance detection value of the luminance detection means is lower than a predetermined value,
A mode for controlling exposure by the gain control;
An imaging apparatus comprising: a mode for controlling exposure by the accumulation time control. 2. The imaging apparatus according to claim 1, wherein when flash emission is prohibited, a mode for controlling exposure by the gain control and a mode for controlling exposure by the accumulation time control can be selected.

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