JP5196768B2 - Imaging device - Google Patents

Description

  The present invention relates to an imaging apparatus having display means for displaying a degree of focus.

  2. Description of the Related Art Conventionally, an electronic still camera, a video camera, and the like have used a manual focus function that can focus on a subject by moving a focus lens by a photographer's own operation. At this time, the photographer moves the focus lens to a position that seems to be most focused while observing the degree of blur of the image displayed on the electronic viewfinder.

  However, since the electronic viewfinder has a small screen and low resolution, it is difficult for the photographer to focus accurately while viewing the image displayed on the electronic viewfinder.

  Therefore, Patent Document 1 proposes a method for displaying the degree of focus on the electronic viewfinder. According to Patent Document 1, a focus evaluation value (focus signal) that is in-focus degree data is generated by performing predetermined signal processing on an output of an image sensor, and a bar display (bar graph) or the like is used on an electronic viewfinder. The in-focus degree is displayed.

  The focus evaluation value often integrates the output of the bandpass filter in order to improve the S / N. In this way, the level of the focus evaluation value changes greatly for different subjects even in the just-focus state. This is because the focus evaluation value varies greatly depending on the contrast of the subject. Even if the subject has the same contrast, the level of the focus evaluation value changes greatly if the luminance of the subject is different.

  Similarly, the level of the focus evaluation value changes depending on the contrast and brightness of the subject even when the subject is out of focus.

Furthermore, in the case of a subject with high contrast and high brightness, the focus evaluation value changes greatly depending on whether the subject is in focus or not. On the other hand, for a subject with low contrast and low brightness, the amount of change in the focus evaluation value is small between the focused state and the unfocused state.
JP 2002-341236 A

  If the focus evaluation value whose level changes greatly depending on the subject condition as described above is displayed on the electronic viewfinder with a single bar, the change amount of the focus evaluation value with respect to the focus degree is low for a low-contrast and low-brightness subject. small. For this reason, the change in the bar on the electronic viewfinder becomes small, and it is difficult to know which position is just focused and focusing becomes difficult.

  Hereinafter, this will be described with reference to FIGS. FIG. 8 shows a bar display when a low-contrast and low-brightness subject is focused, and FIG. 9 shows a bar display when the same subject is out of focus.

  In these figures, the black part on the lower side of the bar extends upward as the focus is adjusted. As is clear from the comparison of the bar displays in FIGS. The change of the bar with respect to the degree of focus is very small. Therefore, it is difficult to distinguish between in-focus and out-of-focus from this bar display, and it is very difficult to focus.

  In view of this, it is conceivable to display a bar so that the amount of change in the bar is large even when the change in the focus evaluation value is small, corresponding to a low-contrast and low-brightness subject. However, when the subject has high contrast and high brightness, the amount of change in the focus evaluation value is large, so the amount of change in the bar on the electronic viewfinder becomes very large, exceeding the limit of the display range in the electronic viewfinder. , It will not be able to display.

  This will be described with reference to FIGS. FIG. 10 shows a bar display when a high-contrast and high-brightness subject is focused, and FIG. 11 shows a bar display when the same subject is out of focus.

  In FIG. 10 and FIG. 11, the bar protrudes from the screen for the sake of explanation, but since it actually protrudes and cannot be displayed, it is difficult to understand the state where the bar is extended most. Therefore, it becomes impossible to know where the focus lens is focused, and focusing becomes very difficult.

(Object of invention)
An object of the present invention is to provide an imaging apparatus that can easily focus on a subject by a manual operation while viewing a display indicating the degree of focus, regardless of the brightness and contrast of the subject.

In order to achieve the above object, the present invention provides an extraction means for extracting a focus signal corresponding to the contrast of an image from an output signal of an imaging means, and a storage means for storing the data as normalized data for normalizing the focus signal. Regardless of the driving of the focus lens, the change of the shooting situation is determined based on a signal other than the focus signal extracted from the extraction means , and the focus extracted when it is determined that the shooting situation has changed. An update means for updating the signal as normalized data and storing it in the storage means, a display means for displaying the captured image, and a focus degree of the subject, and a focus signal extracted by the extraction means are normalized. When the normalization data is stored in the storage means, the focus signal is normalized using the stored normalization data, and the storage means When normalization data is not stored, the storage means stores the focus signal as normalization data and is a display control means for normalizing the focus signal using the normalization data. Displaying means for generating a display signal of the in-focus degree based on the value and displaying the in-focus degree on the display means is provided.

  According to the present invention, it is possible to provide an imaging apparatus that can easily focus on a subject by a manual operation while viewing a display indicating the degree of focus, regardless of the luminance and contrast of the subject.

  The best mode for carrying out the present invention is as shown in the following examples.

  FIG. 1 is a block diagram showing a circuit configuration of an imaging apparatus according to an embodiment of the present invention. In FIG. 1, reference numeral 101 denotes a focus lens for focusing on an image sensor described later, and reference numeral 102 denotes a photo interrupter that detects an initial position of the focus lens 101. Reference numeral 103 denotes a motor that drives the focus lens 101, and reference numeral 104 denotes a focus lens drive circuit that inputs a drive signal to the focus lens drive motor 103 and moves the focus lens 101. Reference numeral 105 denotes a light amount adjusting member such as an aperture or a shutter; 106, a light amount adjusting member driving motor for driving the light amount adjusting member 105; 107, a light amount adjusting member for moving the light amount adjusting member 105 by inputting a drive signal to the light amount adjusting member driving motor 106 It is a drive circuit.

  Reference numeral 108 denotes a zoom lens that changes the focal length of the photographic lens, and reference numeral 109 denotes a photo interrupter that detects the initial position of the zoom lens 108. Reference numeral 110 denotes a motor for driving the zoom lens 108, and reference numeral 111 denotes a zoom lens drive circuit that inputs a drive signal to the zoom lens drive motor 110 to move the zoom lens 108. An image sensor 112 converts reflected light from the subject into an electrical signal, and an A / D converter 113 converts an analog signal output from the image sensor 112 into a digital signal. Reference numeral 114 denotes a timing signal generation circuit (hereinafter referred to as TG) that generates timing signals necessary for operating the image sensor 112 and the A / D converter 113.

  Reference numeral 115 denotes an image processor that performs predetermined processing on the image data input from the A / D converter 113, and 116 denotes a buffer memory that temporarily stores the image data processed by the image processor 115. Reference numeral 117 denotes an interface for connection to a recording medium described later, and 118 denotes a recording medium such as a memory card or a hard disk. Reference numeral 119 denotes a microcontroller (hereinafter referred to as CPU) for controlling the system such as a photographing sequence.

  Reference numeral 120 denotes a zoom switch (switch) for inputting a signal for instructing the start and stop of the zoom operation to the CPU 119. 121 is a switch (hereinafter referred to as SW1) for instructing preparation for photographing such as AF (autofocus) and AE (auto exposure), and 122 is for instructing photographing processing such as main exposure and recording operation after the operation of the switch SW1. The photographing process instruction switch (hereinafter referred to as SW2). Reference numeral 123 denotes a main switch for powering on the system, and reference numeral 124 denotes a mode switch for setting an operation mode of the camera.

  A program memory 125 stores a program executed by the CPU 119, and a work memory 126 writes and reads various data necessary for the CPU 119 to perform processing according to the program stored in the program memory 125. Reference numeral 127 denotes an operation display unit that displays an operation state of the camera and various warnings, 128 denotes an electronic viewfinder (hereinafter referred to as EVF) that displays an image, and 129 denotes a setting switch that performs various settings. A cross switch 130 is used to select a menu item displayed on the operation display unit 127 or the EVF 128, to drive the focus lens 101, or the like. Reference numeral 131 denotes a focus mode switch for switching between auto focus and manual focus. Reference numeral 132 denotes a vertical / horizontal position detection sensor for detecting whether the direction of the camera is a vertical shooting position or a horizontal shooting position. Reference numeral 133 denotes a shake correction device that detects camera shake of the photographer and corrects image shake caused by the shake.

  Next, the basic operation of the imaging apparatus having the above configuration will be described with reference to the flowchart of FIG.

  First, in step S201, the state of the switch SW1 that instructs to prepare for photographing is determined. If the switch SW1 is ON, the process proceeds to step S206, and if not, the process proceeds to step S202.

  If the switch SW1 is not turned on and the process proceeds to step S202, the aperture and shutter speed included in the light amount adjusting member 105 are controlled, and the AE operation is performed so that the brightness of the image displayed on the EVF 128 is appropriate. In the next step S203, an auto white balance (AWB) operation is performed so that the image displayed on the EVF 128 has an appropriate color balance regardless of the color temperature of the light source. In a subsequent step S204, the image signal read from the image sensor 112 is subjected to a predetermined process and displayed on the EVF 128. In the next step S205, manual focus (hereinafter referred to as MF) processing, which will be described later with reference to FIG. 3, is performed.

  If it is determined that the switch SW1 is ON and the process proceeds to step S206, a photographing process described later with reference to FIG. 7 is performed here.

  Next, the MF process executed in step S205 of FIG. 2 will be described using the flowchart of FIG.

  First, in step S301, the state of the focus mode switch 131 is determined. If the focus mode switch 131 is set to MF, the process proceeds to step S302. If not, the process ends.

  When the process proceeds from step S301 to step S302 assuming that MF is set, data used for normalization of the focus evaluation value (focus signal) is cleared. This focus evaluation value normalization data is stored in the work memory 126 in a focus evaluation value normalization data storage determination process described later. In the next step S303, a focus evaluation value acquisition area is set. This focus evaluation value acquisition area is set at the center of the shooting screen. In subsequent step S304, when the image processor 115 generates a focus evaluation value, a cut-off frequency of a band pass filter (hereinafter referred to as BPF) for extracting a component in a certain frequency band from the luminance signal is set.

In the next step S305, the analog video signal read from the image sensor 112 is converted into a digital signal using the A / D converter 113. Further, the image processor 115 extracts a certain frequency band by passing the luminance signal of the digital signal through the BPF set in step S304. Further, integration is performed in the focus evaluation value acquisition area set in step S303, and this is stored in the work memory 126 as a focus evaluation value. In the next step S306, the normalized evaluation data storage determination process of the focus evaluation value is performed according to the procedure described later with reference to FIG. In subsequent step S307, the focus evaluation value acquired in step S305 is normalized. The normalization method at this time is calculated using the formula: normalized focus evaluation value = focus evaluation value acquired this time / normalization data stored in step S306.

  In the next step S308, a display signal indicating the degree of focus is generated based on the focus evaluation value normalized in step S307, and the degree of focus is displayed on the EVF 128.

  The display at this time is a bar display on the EVF 128 as shown in FIG. Here, when the focus state approaches the in-focus state and the focus evaluation value acquired in step S305 increases, the lower black portion of the bar in FIG. 4 extends upward. On the other hand, if the focus evaluation value acquired in step S305 decreases as the distance from the in-focus state decreases, the lower black portion of the bar in FIG. 4 decreases downward. Note that the dotted square in the center of FIG. 4 indicates the focus evaluation value acquisition area set in step S303.

  In the next step S309, drive determination processing of the focus lens 101 is performed according to a procedure described later with reference to FIG. In the subsequent step S310, the state of the focus mode switch 131 is determined. If it is set to MF, the process returns to step S305. If it is not set to MF, the process proceeds to step S311 to shift to the AF mode and exit from this process.

  Next, the focus evaluation value normalized data storage determination process executed in step S306 of FIG. 3 will be described with reference to the flowchart of FIG.

  First, in step S501, it is determined whether focus evaluation value normalization data is currently stored. If stored, the process proceeds to step S502. If not stored, the process proceeds to step S510 described later.

  If it is determined that the focus evaluation value normalization data is stored and the process proceeds to step S502, it is determined whether or not the luminance change of the subject is larger than the specified value. If the change is larger than the specified value, the process proceeds to step S510 described later. If the change in luminance of the subject is not greater than the specified value, the process proceeds to step S503, where it is determined whether the position of the zoom lens 108 has been changed, and if it has been changed, the process proceeds to step S510 described later. If the position of the zoom lens 108 has not been changed, the process proceeds to step S504 to determine whether or not the enlargement magnification in the electronic zoom has been changed. If the enlargement magnification has been changed, the process proceeds to step S510 described later. If the enlargement magnification has not been changed, the process proceeds to step S505, where it is determined whether the specified time has elapsed since the previous focus evaluation value was stored. If it has elapsed, the process proceeds to step S510, which will be described later. If so, the process proceeds to step S506.

  If it is determined that the specified time has not elapsed since the previous focus evaluation value has been stored and the process proceeds to step S506, it is determined whether or not the aperture change amount is larger than the specified value. If the change amount of the aperture is not larger than the specified value, the process proceeds to step S507, the output of the vertical / horizontal position detection sensor 132 of the camera is determined, and if the position has changed, the process proceeds to step S510 described later. If the vertical / horizontal position of the camera has not changed, the process proceeds to step S508, where it is determined whether or not the camera shake amount is larger than the specified value using the camera shake correction device 133. If larger, the process proceeds to step S510 described later. If the camera shake amount is not larger than the specified value, the process proceeds to step S509. Here, when a conversion lens such as a teleconverter or a wide converter is mounted, it is determined whether or not the setting of the conversion lens has been switched when the correction characteristic of the shake correction device 133 is switched in accordance with the optical characteristic. . As a result, if it has been switched, the process proceeds to step S510 to be described later, and if it has not been switched, this process is terminated.

  When the process proceeds to step S510 assuming that the setting of the conversion lens has been switched, the focus evaluation value acquired in step S305 of FIG. 3 is stored in the work memory 126 as normalization data. In the next step S511, data used in the processing from step S502 to step S509 is stored in the work memory 126 based on the current setting and state. Then, this process ends.

  With the configuration described with reference to the flowcharts of FIGS. 3 and 5, the focus evaluation value normalization data is stored / updated as follows.

  If it is determined in step S301 in FIG. 3 that the focus mode switch 131 is MF, the focus evaluation value normalization data is cleared in the next step S302. Thereafter, in step S501 of FIG. 5, it is determined whether or not the focus evaluation value normalization data is stored. Here, since the focus evaluation value normalization data is cleared in step S302 of FIG. 3, the process proceeds to step S510, and the current focus evaluation value is stored as normalization data.

  Thereafter, the processing is performed up to step S309 in FIG. 3. When it is determined in step S310 that the focus mode switch 131 is MF, focus evaluation value normalization data is stored again in step S501 in FIG. Determine whether or not. This time, since normalization data is stored in step S510, the process proceeds to step S502. Thereafter, according to the flowchart of FIG. 5, the current setting and state are compared with the setting and conditions stored in step S511. If there is a change, the current focus evaluation value is stored as normalization data again in step S510.

  In this way, a change in the photographing state such as the setting of the imaging device and the subject condition is repeatedly determined, and the focus evaluation value normalization data is updated whenever there is a change.

  A focus evaluation value normalization data storage switch may be provided separately, and focus evaluation value normalization data may be stored in response to pressing of this switch. By doing so, the photographer can update the focus evaluation value normalization data at any time at a desired timing.

  Further, the focus evaluation value normalization data may be stored when driving of the focus lens 101 is stopped. By doing so, the focus evaluation value normalization data can be updated without the photographer performing an operation for storage. Further, when the focus lens 101 is manually moved by rotating the focus ring without using a motor, the movement of the focus ring is detected, and the focus evaluation value normalization data is stored when the focus ring is stopped. Anyway. Also in this case, the focus evaluation value normalization data can be updated without the photographer performing an operation for storage.

  The reason for normalizing the focus evaluation value as described above will be described below. The focus evaluation value increases when the subject is in focus and decreases when the subject is not in focus. However, the amount of change in the focus evaluation value with respect to the degree of focus differs greatly between a low-contrast subject and a high-contrast subject. Similarly, the amount of change in the focus evaluation value with respect to the degree of focus differs greatly between a subject with low brightness and a subject with high brightness.

  Therefore, if this is displayed as a bar on the EVF 128 as it is, the change amount of the focus evaluation value is very small with respect to the in-focus degree, as described with reference to FIGS. Become. On the other hand, as described with reference to FIGS. 10 and 11, the change amount of the focus evaluation value is very large with respect to the in-focus degree in the high contrast / high luminance object. However, it is easier for the photographer to focus when the bar on the EVF 128 changes in the same way according to the degree of focus, regardless of the contrast and brightness of the subject.

  Therefore, in this embodiment, by normalizing the focus evaluation value, the contrast of the subject and the brightness level are canceled out, and only the in-focus level is reflected in the bar display. Specifically, as described in step S307 in FIG. 3, the acquired focus evaluation value is stored, and then the acquired focus evaluation value is normalized by dividing by the stored focus evaluation value. Further, by re-storing the focus evaluation value in accordance with the camera state or the scene change of the subject, normalization is performed with the focus evaluation value suitable for the scene.

  By normalizing the focus evaluation value in this way, the bar on the EVF 128 changes in the same manner according to the degree of focus regardless of the contrast and brightness of the subject. Therefore, the photographer can easily focus while checking the bar display on the EVF 128.

  Next, the focus lens 101 drive determination process executed in step S309 in FIG. 3 will be described with reference to the flowchart in FIG.

  First, in step S601, it is determined whether the right key of the cross switch 130 is ON. If it is ON, the process proceeds to S602, and the focus lens 101 is driven in an infinite direction. If the right key of the cross switch 130 is not ON, the process proceeds to step S603, where it is determined whether the left key of the cross switch 130 is ON. If it is ON, the process proceeds to S604, and the focus lens 101 is driven in the closest direction. To do. If the left key of the cross switch 130 is not ON, the process proceeds to step S605, where the drive of the focus lens 101 is stopped.

  Next, the photographing process executed in step S206 of FIG. 2 will be described using the flowchart of FIG.

  First, in step S701, a main exposure AE operation is performed. In the next step S702, an AF operation for main exposure is performed. In the subsequent step S703, main exposure and recording are performed.

  According to the above-described embodiment, the focus signal corresponding to the specific frequency band of the brightness of the subject, that is, the contrast of the image, that is, the focus evaluation value, is extracted from the output signal of the image sensor 112 and normalized data for normalization. Remember as. This normalized data is repeatedly determined for changes in imaging device settings, subject conditions, etc., and is updated whenever there is a change. Then, the newly extracted focus evaluation value is normalized using the normalized data that has been updated and stored in this manner. Based on this normalized value, the focus degree of the subject image is displayed as a bar on the EVF 128, for example, as shown in FIG.

  The case of updating the normalized data will be described in detail as follows.

  It is updated when it shifts to the manual focus mode, it is updated when it is determined that the change in luminance of the subject is larger than a predetermined amount, or it is updated when the focal length is changed by the zoom lens. Furthermore, the aperture value is updated when the magnification of the captured image is changed, updated when a predetermined time has elapsed since the last storage of the normalized data, or the aperture value changes according to the change in incident light from the subject. It is updated when you do. Further, it is updated when it is determined that the attitude of the imaging apparatus has changed, or is updated when it is determined that the relative shake amount between the subject and the image sensor 112 is greater than a predetermined value. Furthermore, it is updated when the correction characteristic in the shake correction apparatus 133 is changed in accordance with the optical characteristic of the conversion lens attached to the imaging apparatus.

  Therefore, when focusing with manual focus while displaying a bar indicating the degree of focus, it is possible to easily focus on subjects having any contrast and brightness.

  Also, the change in the focus evaluation value from the out-of-focus state to the in-focus state can be confirmed well regardless of the subject.

1 is a block diagram illustrating a circuit configuration of an imaging apparatus according to an embodiment of the present invention. 3 is a flowchart showing a basic operation of the imaging apparatus according to the embodiment of the present invention. It is a flowchart which shows the MF process in FIG. It is a figure which shows an example of the bar display of the focus evaluation value concerning one implementation of this invention. It is a flowchart which shows the focus evaluation value normalization data storage determination process in FIG. It is a flowchart which shows the focus lens drive determination process in FIG. It is a flowchart which shows the imaging | photography process in FIG. It is a figure which shows the focus evaluation value at the time of focusing of a low contrast / low-intensity subject with the bar display in the conventional imaging device. It is a figure which shows the focus evaluation value at the time of the out-of-focus of a low contrast / low-intensity subject by the bar display in the conventional imaging device. It is a figure which shows the focus evaluation value at the time of the focusing of a high contrast / high-intensity subject with the bar display in the conventional imaging device. It is a figure which shows the focus evaluation value at the time of the out-of-focus of a high contrast / high-intensity subject with the bar display in the conventional imaging device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Focus lens 105 Light quantity adjustment member 108 Zoom lens 112 Image pick-up element 115 Image processing processor 116 Buffer memory 118 Recording medium 119 CPU
128 Electronic viewfinder (EVF)
130 Cross switch 131 Focus mode switch 132 Vertical / horizontal position detection sensor 133 Shake correction device

Claims (10)

Extraction means for extracting a focus signal corresponding to the contrast of the image from the output signal of the imaging means;
Storage means for storing as normalization data for normalizing the focus signal;
Regardless of the driving of the focus lens, a change in the shooting situation is determined based on a signal other than the focus signal extracted from the extraction unit, and a focus signal extracted when it is determined that the shooting situation has changed. Updating means for updating as normalized data and storing it in the storage means;
Display means for displaying the captured image and displaying the degree of focus of the subject;
When normalizing the focus signal extracted by the extraction means, if normalization data is stored in the storage means, the focus signal is normalized using the stored normalization data, and the storage means is stored in the storage means. When normalization data is not stored, the storage means stores the focus signal as normalization data and is a display control means for normalizing the focus signal using the normalization data. An image pickup apparatus, comprising: a display control unit that generates a display signal of the in-focus level based on a value and displays the in-focus level on the display unit.   The imaging apparatus according to claim 1, wherein the update unit updates the normalized data when a focus mode is shifted to a manual focus mode.   The imaging apparatus according to claim 1, wherein the update unit updates the normalized data when it is determined that a change in luminance of the subject is greater than a specified amount.   The imaging apparatus according to claim 1, wherein the update unit updates the normalized data when a focal length is changed by a zoom lens.   The imaging apparatus according to claim 1, wherein the update unit updates the normalized data when a magnification of the captured image is changed.   The imaging apparatus according to claim 1, wherein the update unit updates the normalized data when a specified time has elapsed since the last storage of the normalized data.   The imaging apparatus according to claim 1, wherein the update unit updates the normalized data when it is determined that a change in the aperture value of the aperture unit is larger than a specified value.   The imaging apparatus according to claim 1, wherein the update unit updates the normalized data when it is determined that the attitude of the imaging apparatus has changed.   The imaging apparatus according to claim 1, wherein the updating unit updates the normalized data when it is determined that a relative blur amount between the subject and the imaging unit is larger than a specified amount. A blur correction unit that corrects image blur due to shake applied to the imaging apparatus;
The update means updates the normalized data when a correction characteristic of the blur correction means is changed in accordance with an optical characteristic of a conversion lens attached to the imaging apparatus. The imaging apparatus according to 1.

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