JP2008258983A - Imaging apparatus, control method therefor and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To properly protect an imaging device even when excessive high luminance light over saturated light intensity is made incident on the imaging device during a live view operation. <P>SOLUTION: The imaging apparatus is provided with: the imaging device 6; a display part 11 which displays an image signal generated by the imaging device; a display control part which causes the display part 11 to performs live view display of the image signal; a light shielding device 3 which shields the light made incident on the imaging device; a luminance detection part 9 which detects luminance in the image signal generated by the imaging device; and a control part which causes the imaging device to accumulate electric charges in second accumulation time shorter than first accumulation time, causes the luminance detection part to detect intensity of the light made incident on the imaging device for an image signal generated by accumulation in the second accumulation time when the luminance detection part detects that light with intensity by which the imaging device is saturated is made incident and causes the light shielding part to shield incidence of the light on the imaging device when the detected light intensity is the specified value or more. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a technique for preventing burning of an image sensor during live view display in a digital camera.

  Conventionally, in a so-called compact type digital camera, an image generated by sequential photoelectric conversion by an image sensor is displayed on a liquid crystal display disposed on the back of the camera body instead of an optical viewfinder, and the liquid crystal display is electronically displayed. Many things function as a viewfinder. The operation of causing the liquid crystal display unit to function as an electronic viewfinder in this manner is generally called live view.

  On the other hand, in a single-lens reflex type digital camera (hereinafter referred to as DSLR) instead of a compact type, a quick return mirror and a focal plane shutter are present in front of the image sensor. It becomes.

  That is, first, the quick return mirror and the shutter curtain are retracted from the optical path. In this state, the subject image formed on the image sensor by the lens is converted into an electrical signal by the image sensor and output. The electrical signal output from the image sensor is processed in the analog signal processing circuit, then converted into a digital signal in the A / D converter, and supplied to the digital signal processing circuit. In the digital signal processing circuit, digital image data is further processed to generate display image data, which is displayed on a liquid crystal display unit disposed on the back of the camera.

  The photographer determines the framing of the photographed image, whether or not the camera can be focused by observing the displayed image, operates the camera body as necessary, and further operates the shutter button to take a picture.

In the DSLR as described above, when the live view is displayed, exposure conditions suitable for the above-described determination of framing, focusability, etc., regardless of the exposure conditions such as the image sensor sensitivity, aperture value, and shutter speed used during actual shooting. Display image data is generated. Therefore, the photographer can take an image while making an appropriate determination while viewing the live view image.
JP 2004-109831 A

  However, in the digital camera, extremely high-intensity light may enter the image sensor during the above live view operation, for example, when sunlight is reflected by a mirror surface. In such a case, a compact type digital camera normally uses a lens shutter, so that a shutter that also serves as a diaphragm is narrowed down in real time in accordance with the amount of incident light. Therefore, there is little possibility that high-intensity light directly enters the image sensor. On the other hand, in the live view operation of DSLR, it is assumed that real-time control of the aperture is not performed and exposure control is controlled using the electronic shutter function of the image sensor. In exposure control using an electronic shutter, the amount of light reaching the image sensor does not decrease even when the shutter speed is controlled to the high speed side. Even if the sensitivity of the image sensor is controlled to be low, the signal amplitude output from the image sensor only decreases, and the amount of light incident on the image sensor does not decrease. For this reason, the conventional DSLR has a problem that the image pickup device may be burned if extremely high brightness light is incident during the live view operation.

  In addition, the image sensor can only determine that the amount of light is greater than or equal to the saturation light amount when the amount of light that exceeds the saturation light amount is incident, so whether the intensity of the incident light is dangerous enough to burn the image sensor. Could not be determined. Therefore, there has been no effective solution for the problem of burning of the image sensor due to the incidence of extremely high brightness light.

  Therefore, the present invention has been made in view of the above-described problems, and an object of the present invention is to appropriately protect the image sensor even when extremely high-intensity light exceeding the saturation light amount is incident during the live view operation. Is to do so.

  In order to solve the above-described problems and achieve the object, an imaging apparatus according to the present invention is generated by an imaging unit including an imaging element that photoelectrically converts a subject image formed by an imaging optical system, and the imaging unit. Display means for displaying the image signal, display control means for causing the display means to function as an electronic viewfinder by causing the display means to sequentially display the image signals sequentially generated by the imaging means, and the imaging element. A light shielding means for blocking light incident on the image sensor, a luminance detecting means for detecting the luminance in the image signal generated by the imaging means, and the image sensor while sequentially accumulating charges in a first accumulation time. In a state where the display means functions as an electronic viewfinder, the luminance detection means causes light having an intensity at which the image sensor is saturated to the image sensor. An image generated by causing the image sensor to perform charge accumulation in a second accumulation time shorter than the first accumulation time when detecting that it is shooting, and charge accumulation in the second accumulation time For the signal, when the intensity detection unit detects the intensity of light incident on the image sensor, and the detected light intensity is a specified value or more, the light is incident on the image sensor on the light shielding unit. And a control means for controlling so as to shut off.

  According to another aspect of the present invention, there is provided a control method for an image pickup apparatus including an image pickup unit including an image pickup device that photoelectrically converts a subject image formed by an image pickup optical system, and a display unit that displays an image signal generated by the image pickup unit. Display control means for causing the display means to function as an electronic viewfinder by sequentially displaying the image signals sequentially generated by the imaging means on the display means, and light shielding means for blocking light incident on the imaging element And a luminance detecting means for detecting the luminance in the image signal generated by the imaging means, wherein the imaging device sequentially accumulates charges in a first accumulation time. However, in the state where the display means is functioning as an electronic viewfinder, the luminance detection means emits light having an intensity at which the image sensor is saturated When it is detected that the light is incident on the image element, the image pickup element is caused to accumulate charges in a second accumulation time shorter than the first accumulation time, and is generated by charge accumulation in the second accumulation time. When the intensity of the light incident on the image sensor is detected by the luminance detection unit with respect to the image signal that has been detected, and the detected light intensity is equal to or greater than a specified value, It is characterized by comprising a step of controlling so as to block the incidence of light.

  A program according to the present invention causes a computer to execute the above control method.

  According to the present invention, it is possible to appropriately protect the image sensor even when extremely high-intensity light exceeding the saturation light quantity is incident during the live view operation.

  Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a block diagram showing a configuration of a single-lens reflex digital camera which is an embodiment of an imaging apparatus of the present invention.

  In FIG. 1, 1 is a lens as an imaging optical system, 2 is a quick return mirror, 3 is a focal plane shutter, 4 is a focusing plate, 5 is a finder optical system, and 6 is an imaging device such as a CCD or CMOS sensor. Reference numeral 7 is a signal processing circuit, 8 is a control circuit, 9 is a high brightness detection circuit, 10 is a removable memory card, 11 is a liquid crystal monitor, 12 is a shutter button, and 13 is a live view start button.

  The operation of the digital camera of this embodiment will be described with reference to FIG.

  In the normal mode in which the live view operation is not performed, the subject image formed by the lens 1 is reflected by the quick return mirror 2 and projected onto the focus plate 4 until the shutter button 12 is depressed. The photographer can observe the subject image projected on the focus plate 4 through the viewfinder optical system 5.

  When the shutter button 12 is further pressed down, the quick return mirror 2 is flipped up in the direction of the focus plate 4 and the aperture built in the lens 1 is set to a predetermined aperture value. Further, the focal plane shutter 3 is opened for a predetermined time after the charge accumulation of the image sensor 6 is started, and the subject image formed by the lens 1 is projected onto the image sensor 6 and converted into an electrical signal.

  An image signal read from the image sensor 6 after the determined exposure time has elapsed and the focal plane shutter 3 is closed is processed by the signal processing circuit 7 in accordance with a control signal from the control circuit 8. Further, the image data is converted into an image file through compression processing and recorded on the memory card 10.

  On the other hand, the operation when the live view function is used is as follows.

  When the live view start button 13 is pushed down, the quick return mirror 2 is flipped up in the direction of the focus plate 4 and the aperture built in the lens 1 is set to a predetermined aperture value. Further, the focal plane shutter 3 is opened, and the subject image formed by the lens 1 is projected onto the image sensor 6 and converted into an electrical signal. The image sensor 6 is driven so that an image signal for one frame is read at every predetermined accumulation time (first accumulation time), and the read image signal for one frame is processed by the signal processing circuit 7. Then, it is converted into a video signal and further displayed on the liquid crystal monitor 11. As described above, since the image signal is sequentially read from the image sensor 6 at regular intervals (image signals are sequentially generated), the processing in the signal processing circuit 7 and the display on the liquid crystal monitor 11 are also sequentially performed at regular intervals. As a result, the live view function is realized. In other words, display control is performed so that the liquid crystal monitor 11 functions as an electronic viewfinder.

  At this time, there are a case where the signals of all the pixels are read out from the image sensor 6 and a case where only the signals of some pixels are read out in order to shorten the readout time and shorten the frame interval. Further, when reading out only the signals of some pixels, there are a case where reading is performed by thinning out pixels of the entire screen, and a case where enlarged display is performed by reading only a specific area. How the pixel signal is read out is selected depending on the type of the image sensor used and the required display mode.

  As described above, the live view operation is performed, and the photographic image is framed and the focus is confirmed by the liquid crystal monitor 11. During the live view operation, the high luminance detection circuit 9 connected to the signal processing circuit 7 detects the high luminance. Is done. The high luminance signal detected by the high luminance detection circuit 9 is input to the control circuit 8. When the high luminance signal is higher than the specified value, the control circuit 8 sets the accumulation time of the image sensor 6 to a shorter accumulation time (second accumulation time) during the next one frame. The accumulation time for this short-time accumulation is determined in consideration of the set value of the aperture of the lens 1 so that even a light quantity that may damage the image sensor 6 can be captured without being saturated.

  An image signal is read out from the image sensor 6 after one frame is accumulated in a short time accumulation. Since the image signal for one frame read out here is set to have a short accumulation time as described above, the image signal is not saturated to an extremely high luminance that may damage the image sensor 6. Therefore, the maximum value of the luminance of the light incident on the image sensor 6 can be detected. When the high luminance signal (maximum luminance value) obtained by such an operation is higher than the specified value, ultra high luminance light that may damage the image sensor 6 is incident during the normal accumulation time. Therefore, the image sensor is protected.

  When the protection operation of the image sensor is started, the control circuit 9 displays a warning on the liquid crystal monitor 11. Further, the focal plane shutter 3 is closed and the quick return mirror 2 is lowered from the direction of the focus plate 4 to block the subject light reaching the shutter curtain and the image sensor 6 to protect the image sensor 6 and at the same time the shutter curtain burns out. It also prevents that.

  If the high luminance part detected in the short-time accumulation has a luminance value at a level that does not damage the image sensor 6, the accumulation time is returned to the normal value and the live view operation is continued. When the shutter button 12 is further depressed, the focal plane shutter 3 is once closed and the aperture built in the lens 1 is set to a predetermined aperture value. Further, after the accumulation of the image sensor 6 is started, the focal plane shutter 3 is opened for a predetermined time, and the subject image formed by the lens 1 is projected onto the image sensor 6 and converted into an electric signal.

  After a predetermined time has passed and the shutter 3 is closed, the image signal read from the image sensor 6 is processed in the signal processing circuit 7 in accordance with a control signal from the control circuit 8. Further, it is converted into an image file through compression processing and recorded on the memory card 10.

  FIG. 2 is a block diagram showing a configuration of the high luminance detection circuit in the present embodiment.

  In FIG. 2, 101 is a peak detection circuit, 102 is a gate circuit, and 103 is a reset circuit.

  The operation of the high luminance detection circuit 9 will be described with reference to FIG.

  The image signal input from the signal processing circuit 7 is input to the peak detection circuit 101 through the gate circuit 102. The gate circuit 102 supplies an image signal to the peak detection circuit 101 only during a period when a valid image signal is supplied from the signal processing circuit 7 in accordance with the gate signal from the control circuit 8. The peak detection circuit 101 operates to hold the maximum value of the input image signal and output the held signal. Therefore, when an image signal for one frame is input, the maximum luminance value of the input one frame is output.

  In response to the reset signal from the control circuit 8, the reset circuit 103 resets the maximum luminance value held by the peak detection circuit 101 before the peak detection operation is started.

  FIG. 3 is a flowchart showing an operation flow of the imaging apparatus of the present embodiment.

  First, in step S301, the live view operation is started when the live view start button 13 is pressed. Then, in step S302, the quick return mirror 2 is retracted in the direction of the focus plate 4, and in step S303, the aperture built in the lens 1 is set to a predetermined aperture value for live view. Further, the focal plane shutter 3 is opened in step S304.

  Next, the accumulation time of the image sensor 6 is set to the initial value for live view in step S305, and accumulation of the image sensor 6 is started in step S306.

  After the wait period in step S307, it is determined in step S308 whether a predetermined accumulation time has elapsed. If the predetermined accumulation time has not been reached (No), the process returns to step S307. On the other hand, if the predetermined accumulation time has been reached in step S307 (Yes), an image signal is read from the image sensor 6 in step S309.

  When an image signal is read from the image sensor 6, high luminance detection is performed in the high luminance detection circuit 9. As a result, when a high-luminance part with a signal level equal to or higher than the specified signal level is detected in step S310 (Yes), the set value of the accumulation time of the image sensor 6 at that time is normal accumulation or short-term accumulation in step S313. Is judged.

  If the normal accumulation is set in step S313 (No), the accumulation time is set to a time shorter than the normal accumulation time (short-time accumulation) in step 314. The accumulation time for this short-time accumulation is determined in consideration of the set value of the aperture of the lens 1 so that even a light quantity that may damage the image sensor 6 can be captured without being saturated. This short-time accumulation is realized by setting the time interval from the start of accumulation of the image sensor 6 to the start of reading of the image signal shorter than that in the case of normal accumulation.

  In step S314, after the accumulation time of the image sensor 6 is set to short-time accumulation, the process returns to step S306 to accumulate the next one frame.

  On the other hand, if it is determined in step S313 that the short-time accumulation is performed, the output level of the high luminance detection circuit 9 is further determined in step S315. If it is determined that the luminance is at a level at which there is no risk of damaging the image sensor 6 (No), the process returns to step S305, the accumulation time is set to the initial value for normal accumulation, and the steps after step S306. Repeat the operation. If it is determined in step S315 that the brightness is high enough to cause damage to the image sensor 6 (Yes), the image sensor protection operation is started from step S316.

  In step S310, if a high-luminance portion that is equal to or higher than the specified signal level (not less than the specified value) is not detected (No), it is determined whether the shutter button 12 is pressed in step S311. If the shutter button 12 is not depressed (No), the process returns to step S306, and accumulation of the next one frame is started. On the other hand, if the shutter button 12 is depressed (Yes), the photographing operation is started in step S312.

  When the photographing operation is started, the focal plane shutter 3 is once closed and the aperture built in the lens 1 is set to a predetermined aperture value. Further, after the accumulation of the image sensor 6 is started, the shutter 3 is opened for a predetermined time, and the subject image formed by the lens 1 is projected onto the image sensor 6 and converted into an electric signal. After the predetermined time has elapsed and the focal plane shutter 3 is closed, the image signal read from the image sensor 6 is processed in the signal processing circuit 7 in accordance with a control signal from the control circuit 8. Further, it is converted into an image file through compression processing and recorded on the memory card 10.

  FIG. 4 is a flowchart showing an operation procedure of the image sensor protection operation starting from step S316 in FIG.

  In FIG. 4, when the image sensor protection operation is started in step S401, the accumulation operation of the image sensor 6 is stopped in step S402, and the shutter 3 is closed (step S403). Next, the quick return mirror 2 is lowered from the direction of the focus plate 4 to a position that blocks the optical path to the image sensor 6 (step S404), and the diaphragm built in the lens 1 is closed (step S405). This completes the image sensor protection operation (step S406).

  As described above, in the present embodiment, when an ultra-high luminance is detected during the live view operation, the accumulation time of the image sensor 6 is shortened by one frame so as to be higher than the saturated luminance during the normal live view operation. It can detect even high brightness. When an extremely high luminance that may damage the image sensor 6 is detected in one frame having a short accumulation time, the image sensor is protected. This protection operation is performed by blocking (blocking) light incident on the image sensor 6 using the focal plane shutter 3, the quick return mirror 2, a diaphragm built in the lens 1, and the like. Such an operation makes it possible to effectively protect the image sensor 6. .

(Other embodiments)
The object of each embodiment is also achieved by the following method. That is, a storage medium (or recording medium) in which a program code of software that realizes the functions of the above-described embodiments is recorded is supplied to the system or apparatus. Then, the computer (or CPU or MPU) of the system or apparatus reads and executes the program code stored in the storage medium. In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the storage medium storing the program code constitutes the present invention. Further, by executing the program code read by the computer, not only the functions of the above-described embodiments are realized, but the present invention includes the following cases. That is, based on the instruction of the program code, an operating system (OS) or the like running on the computer performs part or all of the actual processing, and the functions of the above-described embodiments are realized by the processing.

  Furthermore, the following cases are also included in the present invention. That is, the program code read from the storage medium is written in a memory provided in a function expansion card inserted into the computer or a function expansion unit connected to the computer. Thereafter, based on the instruction of the program code, a CPU or the like provided in the function expansion card or function expansion unit performs part or all of the actual processing, and the functions of the above-described embodiments are realized by the processing.

  When the present invention is applied to the above storage medium, the storage medium stores program codes corresponding to the procedure described above.

1 is a block diagram illustrating a configuration of a single-lens reflex digital camera that is an embodiment of an imaging apparatus of the present invention. FIG. It is a block diagram which shows the structure of the high-intensity detection circuit in one Embodiment of this invention. It is a flowchart which shows the flow of operation | movement of the imaging device of one Embodiment of this invention. It is a flowchart which shows the flow of the image pick-up element protection operation in one Embodiment of this invention.

Explanation of symbols

1 Lens 2 Quick Return Mirror 3 Focal Plane Shutter 4 Focus Plate 5 Viewfinder Optical System 6 Image Sensor 7 Signal Processing Circuit 8 Control Circuit 9 High Brightness Detection Circuit 10 Memory Card 11 LCD Monitor 12 Shutter Button 13 Live View Start Button 101 Peak Detection Circuit 102 Gate circuit 103 Reset circuit

Claims (5)

An image pickup means including an image pickup device for photoelectrically converting a subject image formed by the image pickup optical system;
Display means for displaying an image signal generated by the imaging means;
Display control means for causing the display means to function as an electronic viewfinder by sequentially displaying the image signals sequentially generated by the imaging means on the display means;
Light blocking means for blocking light incident on the image sensor;
Luminance detection means for detecting the luminance in the image signal generated by the imaging means;
In a state where the display unit functions as an electronic viewfinder while causing the image sensor to sequentially accumulate charges in a first accumulation time, the luminance detection unit emits light having an intensity at which the image sensor is saturated. When it is detected that the light is incident on the image sensor, the image sensor is caused to perform charge accumulation with a second accumulation time shorter than the first accumulation time, and is generated by charge accumulation for the second accumulation time. When the intensity of the light incident on the image sensor is detected by the luminance detection unit with respect to the image signal that has been detected, and the detected light intensity is equal to or greater than a specified value, the light shielding unit applies the light to the image sensor. Control means for controlling to block the incidence of light;
An imaging apparatus comprising:   The imaging apparatus according to claim 1, wherein the light shielding unit includes a focal plane shutter disposed in front of the imaging element.   The imaging apparatus according to claim 2, wherein the light shielding unit further includes a quick return mirror that guides light incident from the imaging optical system to an optical viewfinder of the imaging apparatus. An image pickup unit including an image pickup device that photoelectrically converts a subject image formed by the image pickup optical system, a display unit that displays an image signal generated by the image pickup unit, and an image signal generated sequentially by the image pickup unit Display control means for causing the display means to function as an electronic viewfinder by causing the display means to display, a light shielding means for blocking light incident on the imaging device, and a luminance in an image signal generated by the imaging means A method of controlling an imaging apparatus comprising:
In a state where the display unit functions as an electronic viewfinder while causing the image sensor to sequentially accumulate charges in a first accumulation time, the luminance detection unit emits light having an intensity at which the image sensor is saturated. When it is detected that the light is incident on the image sensor, the image sensor is caused to perform charge accumulation with a second accumulation time shorter than the first accumulation time, and is generated by charge accumulation for the second accumulation time. When the intensity of the light incident on the image sensor is detected by the luminance detection unit with respect to the image signal that has been detected, and the detected light intensity is equal to or greater than a specified value, the light shielding unit applies the light to the image sensor. A method for controlling an image pickup apparatus, comprising a step of controlling light to be blocked.   A program for causing a computer to execute the control method according to claim 4.

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