JP2008026801A - Optical device and control method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical device capable of performing a zooming operation while preventing out-of-focus of an object before and after the zooming operation and to provide a control method therefor. <P>SOLUTION: The optical device includes: an object detecting means, which detects an object from an image; a storage means, which stores data corresponding to the position of a focus lens according to the position of a zoom lens; and a control means, which exerts a focus correction control accompanying the movement of the zoom lens, by moving the focus lens based on the data of the storage means. The control means exerts the focus correction control according to the size of the object obtained by the object detecting means. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical apparatus having an automatic focus adjustment function and a control method thereof.

  In the imaging apparatus, if the subject (object) is in focus on the wide side (tele side), the subject is in focus even after zooming in (zoom out) to the telele side (wide side). Is desired. In addition, in an imaging apparatus having a subject detection function, subject detection can be quickly performed because the subject is in focus even after the zoom operation.

For the above reason, conventionally, so-called zoom tracking control is performed in which the focus lens is moved in accordance with the zoom operation in order to prevent the image from being defocused during zooming and the collision between the zoom lens and the focus lens. For example, see Patent Document 1). FIG. 1 is a zoom tracking locus (cam locus) representing the positional relationship between the zoom lens and the focus lens, and the positional relationship is determined for each subject distance. When performing the zoom operation, information corresponding to the subject distance is calculated from the zoom lens position and the focus lens position. The zoom operation is performed following the corresponding zoom tracking locus. For example, in the zoom-in operation, if it is determined that the subject distance is infinite from the focus lens position on the subject wide side, the zoom-in operation is performed following the trajectory 101. By doing this, it is possible to perform a zoom-in operation while focusing at infinity.
JP-A-1-321416

  In the above conventional example, depending on the depth of field, the subject distance cannot be accurately calculated from the positional relationship between the focus lens and the zoom lens. For example, even if the distance to the subject is 5 m, if the subject distance is determined to be infinite, the zoom tracking locus at infinity is followed based on the positional relationship between the zoom lens and the focus lens in FIG. .

  Therefore, the subject may be blurred.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to perform a zoom operation so that the subject is not blurred.

  In order to achieve the above object, an optical apparatus according to the present application includes an object detection unit that detects an object from an image, a storage unit that stores data relating to a position of a focus lens according to the position of the zoom lens, and a zoom lens. Control means for performing focus correction control associated with the movement of the focus lens by moving the focus lens based on the data of the storage means, and the control means has a size of the object obtained by the object detection means. Accordingly, the focus correction control is performed.

  Further, the control method of the optical device according to the present invention includes the step of obtaining data relating to the position of the focus lens according to the position of the zoom lens, and the focus correction control accompanying the movement of the zoom lens based on the data of the storage means. A focus correction step for moving the focus lens, and the correction step performs the focus correction according to the size of the object.

  According to the present invention, it is possible to perform a zoom operation in which blurring of an object is epoch-making compared to the conventional art.

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

(Configuration of imaging device)
FIG. 2 is a block diagram of the imaging apparatus (optical apparatus) of the present embodiment. An optical system 201 includes a zoom lens, a focus lens, and a stop. 202 is a mechanical shutter (shown as a mechanical shutter), 203 is an image sensor that converts light from a subject into an image signal, 204 is a CDS circuit that performs analog signal processing, and 205 is an A / D conversion that converts an analog signal into a digital signal. It is a vessel. Reference numeral 206 denotes a timing signal generation circuit that generates signals for operating the image sensor 203, the CDS circuit 204, and the A / D converter 205. Reference numeral 207 denotes a drive circuit for the optical system 201, the mechanical shutter 202, and the image sensor 203. Reference numeral 208 denotes a signal processing circuit that performs signal processing necessary for captured image data. Further, the signal processing circuit includes a face detection circuit 222. Reference numeral 209 denotes an image memory for storing signal-processed image data and face detection results. Reference numeral 210 denotes an image recording medium that can be removed from the imaging apparatus, and reference numeral 211 denotes a recording circuit that performs processing for recording signal-processed image data on the image recording medium 210. Reference numeral 212 denotes an image display device that displays image data subjected to signal processing, and 213 denotes a display circuit that performs processing for displaying an image on the image display device 212. Reference numeral 214 denotes a system control unit that controls the entire imaging apparatus. Reference numeral 215 denotes a non-volatile memory (ROM) for storing a program describing a control method executed by the system control unit 214 and control data such as parameters and tables used when executing the program. . The nonvolatile memory 215 further stores zoom tracking locus data and correction data such as a scratch address. The zoom tracking locus data here is data relating to the position of the zoom lens and the position of the focus lens according to the subject distance. If the focus lens is moved according to the movement of the zoom lens according to the zoom tracking locus data, focus correction control can be performed. Reference numeral 216 denotes a volatile memory (RAM) used when the system control unit 214 controls the imaging apparatus by transferring and storing a program, control data, and correction data stored in the nonvolatile memory 215. It is. Reference numeral 217 denotes a strobe.

  Further, the system control unit 214 includes a face detection operation control unit 223 that controls the operation of face detection, and the optical system 201 includes an IS (Image Stabilizer) lens that performs camera shake correction. In addition, the shake detection unit 224 can detect the shake of the image pickup apparatus using a vibration gyro and the like, and camera shake correction is performed based on this information.

  Reference numeral 218 denotes an operation unit of the imaging apparatus, which sets shooting conditions and selects a shooting mode. A main switch (main SW) 221 is a switch for turning on the system according to an instruction from the operator. A switch 219 is turned on when the shutter button is half-pressed by the operator. Standby operation is performed. Reference numeral 220 denotes a switch that is turned on when the shutter button is pressed by an operator. When the switch is turned on, an image is taken. Reference numeral 225 denotes a zoom key for receiving an instruction for a zoom operation by the operator.

  Hereinafter, an imaging operation using the imaging apparatus configured as described above will be described. Note that the mechanical shutter 202 is used in the following imaging operation. Prior to the imaging operation, necessary programs, control data, and correction data are transferred from the nonvolatile memory 215 to the volatile memory 216 and stored when the operation of the system control unit 214 is started, such as when the imaging apparatus is turned on. Shall. These programs and data are used when the system control unit 214 controls the imaging apparatus. Further, if necessary, additional programs and data are appropriately transferred from the nonvolatile memory 215 to the volatile memory 216, or the system control unit 214 directly reads the data in the nonvolatile memory 215 and uses them. Shall.

  First, the optical system 201 drives a diaphragm and a lens according to a control signal from the system control unit 214 to form a subject image set to an appropriate brightness on the image sensor 203. Next, the mechanical shutter 202 is driven by the control signal from the system control unit 214 so as to shield the image sensor 203 in accordance with the operation of the image sensor 203 so that a necessary exposure time is reached. At this time, when the image pickup element 203 has an electronic shutter function, it may be used together with the mechanical shutter 202 to secure a necessary exposure time. The image sensor 203 is driven by a drive pulse based on the operation pulse generated by the timing signal generation circuit 206 controlled by the system control unit 214, and converts the subject image into an electrical signal by photoelectric conversion as an analog image signal. Output. The analog image signal output from the image sensor 203 is subjected to an operation pulse generated by the timing signal generation circuit 206 controlled by the system control unit 214, and the clock synchronization noise is removed by the CDS circuit 204. The A / D converter In 205, it is converted into a digital image signal. Next, in the signal processing circuit 208 controlled by the system control unit 214, image processing such as color conversion, white balance, and gamma correction, resolution conversion processing, image compression processing, and the like are performed on the digital image signal. The image memory 209 is used to temporarily store a digital image signal during signal processing, store image data that is a digital image signal subjected to signal processing, or temporarily store a face detection result. It is done. The image data signal-processed by the signal processing circuit 208 and the image data stored in the image memory 209 are converted into data suitable for the image recording medium 210 by the recording circuit and recorded on the image recording medium 210. The data suitable for the image recording medium 210 here is, for example, file system data having a hierarchical structure. Further, the image data processed by the signal processing circuit 208 and the image data stored in the image memory 209 are subjected to resolution conversion processing by the signal processing circuit 208. Thereafter, the signal is converted into a signal suitable for the image display device 212 (for example, an NTSC analog signal or the like) in the display circuit. Then, it is displayed on the image display device 212.

  Here, the signal processing circuit 208 may output the digital image signal as it is as image data to the image memory 209 or the recording circuit without performing signal processing by the control signal from the system control unit 214. In addition, when requested by the system control unit 214, the signal processing circuit 208 sends the digital image signal and image data information generated in the signal processing process or information extracted from them to the system control unit 214. Output. The digital image signal and image data information generated in the signal processing here is, for example, information such as the spatial frequency of the image, the average value of the designated area, the data amount of the compressed image, and the like. Further, the recording circuit outputs information such as the type and free capacity of the image recording medium 210 to the system control unit 214 when requested by the system control unit 214.

  Further, a reproduction operation when image data is recorded on the image recording medium 210 will be described. The recording circuit reads image data from the image recording medium 210 in accordance with a control signal from the system control unit 214. In addition, when the image data is a compressed image, the signal processing circuit 208 performs an image expansion process according to a control signal from the system control unit 214 and stores it in the image memory 209. The image data stored in the image memory 209 is subjected to resolution conversion processing by the signal processing circuit 208, converted to a signal suitable for the image display device 212 in the display circuit, and displayed on the image display device 212.

(Operation of the embodiment)
Hereinafter, the operation of the embodiment will be described in detail with reference to FIGS.

<Overall Operation of Imaging Device>
FIG. 3 is a flowchart illustrating the overall operation of the imaging apparatus according to the present embodiment. This processing is performed in the system control unit 214 when the setting is to perform face detection.

  First, in step S301, face detection processing is performed by the face detection circuit 222 (subject detection unit), and the detection result is temporarily stored in the image memory 209 regardless of detection / non-detection. Thereafter, the process proceeds to step S302. In step S302, the system control unit 214 detects the state of the zoom key 225. If the zoom key 225 has been operated, the process proceeds to step S303; otherwise, the process proceeds to step S306. In step S303, it is determined whether the operated zoom operation is a zoom-in operation or a zoom-out operation. If it is a zoom-out operation, a zoom-out operation is performed according to the flowchart of FIG. 4 described later (step S304), and if it is a zoom-in operation, a zoom-in operation is performed according to the flowchart of FIG. 5 described later (step S305). . Thereafter, the process proceeds to step S306.

  In step S306, the state of the switch SW1 is checked. If it is ON, the process proceeds to step S307, and if not, the process returns to step S301. In step S307, subject brightness is calculated from the output signal of the image sensor 203, and the signal processing circuit 208 performs AE processing. In the AE processing, a part of the area for one screen is extracted from the output signal of the image sensor 203, and arithmetic processing such as cumulative addition is performed on the luminance value of the signal in this area. Thereby, the AE evaluation value corresponding to the brightness of the subject is calculated. Thereafter, AF processing is performed in the signal processing circuit 208. In the AF process, a part of the area for one screen is extracted from the output signal of the image sensor 203, the high-frequency component of the signal in this area is extracted through a high-pass filter (HPF) or the like, and calculation such as cumulative addition is performed. Processing is performed. Thereby, an AF evaluation value corresponding to the contour component amount on the high frequency side is calculated. The AF is performed by obtaining the position (focus position) of the focus lens that maximizes the AF evaluation value.

  When the face detection process described above is performed, AE and AF processes are performed based on the result of face detection. Specifically, the above-described AE processing and AF processing are performed on the signal of the area corresponding to the face detected by the face detection circuit 222.

  In step S308, the state of the switch SW2 is checked by the system control unit 214. If the switch SW2 is ON, the process proceeds to step S309 to perform an imaging operation. Otherwise, the process proceeds to step S310. In step S310, the state of the switch SW1 is checked. If the switch SW1 is ON, the process returns to step S308; otherwise, the process returns to S301. After imaging in step S309, the process proceeds to step S310.

<Zoom-out operation>
The zoom-out operation in step S304 in FIG. 3 will be described with reference to FIG.

  This process is performed by the system control unit 214. If the sequence of FIG. 4 is a zoom-out operation, the zoom-out is performed following the zoom tracking locus of the subject distance calculated from the positional relationship between the focus lens and the zoom lens. This is because in the zoom-out operation, the depth of field becomes deeper as the zoom-out progresses (as the focal length becomes shorter), so that the subject is not blurred before and after the zoom-out operation.

  First, in step S401, the system control unit 214 reads the zoom tracking locus from the ROM 215, and the subject distance L1 is calculated from the focus lens position F1 and the zoom lens position Z5 (a in FIG. 6). Next, in step S402, a zoom-out operation is performed following the zoom tracking locus of the subject distance: L1 obtained in the above process, and the process proceeds to step S403.

  In step S403, the system control unit 214 detects whether the zoom key 225 is being operated. If the zoom key 225 is being operated, the process returns to step S402. If not, the process proceeds to step S404, and the zoom-out operation is stopped.

  FIG. 6A shows a driving locus when zooming out from the zoom lens position: Z5 to the zoom lens position: Z1.

<Zoom in action>
The zoom-in operation in step S305 in FIG. 3 will be described with reference to FIG.

  This processing is performed by the signal processing circuit 208 and the system control unit 214. The sequence of FIG. 5 is zoomed in so as to follow the zoom tracking locus of the subject distance obtained from the detection result of the face detection when the face detection setting is performed.

  First, in step S501, the zoom tracking locus is read from the ROM 215 by the system control unit 214, and the subject distance: L2 is calculated from the focus lens position: F2 and the zoom lens position: Z1 (b in FIG. 6). Next, in step S502, the result of face detection performed in step 301 is acquired from the image memory 209, and the process proceeds to step S503. In step S503, the subject distance: A1 is calculated from the face size of the face detection result acquired in the above process. As the calculation method, if the face size is large, the distance is close, and if the face size is small, it can be determined that the distance is long. Therefore, the calculation is performed with a proportional relationship between the face size as the subject and the subject distance. Here, if no face is detected, A1 = 0.

  Here, the face detection circuit 222 executes pattern recognition processing to detect face information from the image data. In addition to the pattern recognition method, the face image data detection method includes a method using learning using a neural network or the like, and a method of extracting a characteristic part of a physical shape from an image region. In addition, there are many other methods such as a method of statistically analyzing image feature quantities such as detected skin color and eye shape. Furthermore, methods that have been studied for practical use include a method that uses wavelet transform and image feature amounts.

  The system control unit 214 (including the face size determination unit) counts the number of pixels in the face area (face coordinates) from the face information detected by the face detection circuit 222, and determines the face size based on the number of pixels.

  The system control unit 214 calculates the eye interval based on the face information (eye position information) detected by the face detection circuit 222, and calculates the eye interval and face size (number of pixels) obtained in advance. It is also possible to make a table using the statistical relationship and to determine the face size. Further, the face size may be determined by counting the number of pixels in the face area from the coordinate values of the four corners (predetermined positions) of the face.

  The system control unit 214 obtains the subject distance with reference to the conversion table at the lens focal length of 38 mm (wide angle) created based on the data indicating the relationship between the face size (number of pixels) and the subject distance. As described above, there is a proportional relationship between the face size and the subject distance.

  If the lens focal length during zooming is not 38 mm, the conversion table is referred to using the integrated value of (38 / lens focal length during zooming (mm)) and (determined face size).

  Thereby, the subject distance can be obtained.

  In the next step S504, it is determined whether A1 = 0. In other words, if no face is detected, the zoom-in operation is performed following the zoom tracking locus of L2. Otherwise, the process proceeds to step S505. In the next step S505, the subject distance: L2 calculated from the focus lens position and the zoom lens position is compared with the subject distance: A1 calculated from the face size of the face detection result. If A1≈L2, the process proceeds to step S507, and the zoom-in operation is performed following the zoom tracking locus of L2. Otherwise, the process proceeds to step S506 to perform a zoom-in operation following the zoom tracking locus of A1. In step S506, the following locus is corrected. The correction content is, for example, following the zoom tracking locus: A1 while performing a zoom-in operation as shown in FIG. 6b (point 601 → point 604 → point 603). Thus, after zooming in, it is possible to focus on the subject distance A1.

  In step S507, the zoom-in operation is performed following the zoom tracking locus of L2 or the locus corrected in step S506.

  In the next step S508, it is determined whether or not the zoom key 225 is operated. If not, the process proceeds to step S511, and the zoom-in operation is stopped. If it has been operated, the process proceeds to step S509. In step S509, the control circuit 214 determines whether or not the zoom-in operation has been performed more than a predetermined amount. If not, the process proceeds to step S507 and the zoom-in operation is continued. Here, whether or not the zoom-in operation is performed by a predetermined amount or more is determined by a predetermined time interval: ΔT (including an elapsed time from the start of the zoom operation) or a zoom lens position interval: ΔZ (the movement of the zoom lens from the start of the zoom operation) (Including the amount).

  In step S510, the face detection circuit 222 acquires an image during the zoom-in operation to perform face detection, and the process proceeds to step S504. In this processing, face detection is performed in parallel with the zoom-in operation as shown in FIG. By doing this, even if it takes time to detect a face, the zoom-in operation can be performed without time loss. In addition, by repeating face detection at predetermined intervals in this manner, even when the face of the subject is small and cannot be detected before the zoom-in operation, the subject can be focused after the zoom-in operation.

  As described above, the face detection result is reflected in the zoom tracking control, so that the subject (face) is not blurred before and after the zoom-in operation.

  In the above-described embodiment, the correction contents of the zoom tracking locus in step S506 are locus such as point 601 → point 604 → point 603, but are not limited thereto. For example, the zoom tracking locus A1 may be followed after only the focus lens is moved once, such as point 601 → point 602 → point 603.

  In the above-described embodiment, the process is performed when the face detection setting has been made. However, the present invention is not limited to this. For example, there are cases where face detection is not set even when a scene mode in which a person is a subject, such as a portrait mode, is selected. In this case, as shown in FIG. 8, the initial zoom operation may be performed as before, and the locus may be corrected based on the result after performing face detection.

  Further, in the above embodiment, the determination in step S509 in FIG. 5 is made based on a predetermined time interval: ΔT or zoom lens position interval: ΔZ. However, for example, if the reliability or success level of the face detection result calculated by the face detection function is low, the interval may be shortened, and if high, the interval may be increased.

  In the above embodiment, the face detection process is performed by the face detection circuit 222, and the detection result is temporarily stored in the image memory 209 regardless of detection / non-detection. As long as it detects, it does not have to be a face. For example, it may be possible to cut out and detect a subject image from the background. At this time, the subject may be any subject other than a person whose size is known in advance.

  In the above embodiment, the focus correction during the zoom operation by the operation of the zoom key before SW1 is turned on has been described, but the present invention is not limited to this. For example, the present invention can be applied to focus correction by moving the focus lens when a zoom key is operated during moving image shooting.

  Further, in a state before the zoom operation is performed, it is assumed that the focus lens is moved to a position where the subject is focused by the focus detection method or the phase difference AF method for obtaining the AF evaluation value described above. In the phase difference AF method here, the light fluxes A and B from the subject pass through the optical system and form an image on the planned imaging plane, and a pair of secondary imaging lenses installed behind the planned imaging plane. Re-image is formed on the AF sensors a and b. Then, focus detection is performed by minimizing the phase difference between the subject images re-imaged on the AF sensors a and b.

  In the above embodiment, the locus correction is performed using the subject distance information calculated from the lens position at the time of zooming out. However, the locus correction is performed from the face detection result as the subject as in the case of zooming in. May be. This is because, depending on the depth of field, it may be more appropriate to correct the locus using the size of the subject.

  In the above-described embodiments, the imaging apparatus in which the lens barrel is integrally provided has been described. However, the present invention can also be applied to an interchangeable lens imaging apparatus (such as a single-lens reflex digital camera). Furthermore, the present invention can also be applied to an interchangeable lens as an optical device that acquires an image signal from an imaging apparatus and performs scan AF processing.

  In the present embodiment, the imaging apparatus having an optical system such as a zoom lens and a focus lens has been described as an example. However, the present invention is not limited to this. For example, a telescope or a microscope may be used.

It is a graph which shows a typical zoom tracking locus. It is a block diagram which shows the structure of the imaging device to which this invention is applied. It is a flowchart which shows the process of the imaging device to which this invention is applied. 4 is a flowchart of zoom-out operation processing in FIG. 3. It is a flowchart of the zoom-in operation process in FIG. It is a graph which shows the zoom tracking operation | movement of this invention. It is a graph which shows the processing relationship of zoom tracking operation and face detection. 6 is a graph showing a processing relationship between zoom tracking operation and face detection when face detection is not performed.

Explanation of symbols

201 Optical System 202 Mechanical Shutter 203 Image Sensor 204 CDS
205 A / D converter 206 Timing signal generator 207 Drive circuit 208 Signal processing circuit 209 Image memory 210 Recording medium 211 Recording circuit 212 Image display device 213 Display circuit 214 System control circuit 215 Non-volatile memory 216 Volatile memory 217 Strobe 218 Imaging Device Operation Unit 219 Switch (SW1)
220 switch (SW2)
221 Main switch 222 Face detection circuit 223 Face detection operation control unit 224 Shake detection unit 225 Zoom key

Claims (8)

Object detection means for detecting the object from the image;
Storage means for storing data relating to the position of the focus lens according to the position of the zoom lens;
Control means for performing focus correction control accompanying movement of the zoom lens by moving the focus lens based on the data of the storage means;
The optical device according to claim 1, wherein the control unit performs the focus correction control according to a size of the object obtained by the object detection unit.   The optical apparatus according to claim 1, wherein the focus correction control changes according to a focal length when the object is detected.   3. The control unit according to claim 1, wherein the control unit performs the correction control based on a size of the object with respect to an angle of view acquired when a zoom operation of a predetermined amount or more is performed. An optical device according to 1.   4. The optical apparatus according to claim 3, wherein the predetermined amount includes at least one of an elapsed time from the start of the zoom operation and a movement amount of the zoom lens. A detecting means for detecting information corresponding to the distance of the object from the position of the zoom lens and the position of the focus lens;
The control means performs focus correction control for moving the focus lens based on information corresponding to the distance of the object obtained by the detection means and data stored in the storage means, and then performs the object correction. 5. The optical apparatus according to claim 1, wherein focus correction control is performed in accordance with a size of an object obtained by the detection unit. A detecting means for detecting information corresponding to the distance of the object from the position of the zoom lens and the position of the focus lens;
When the object is not detected by the object detection means, the control means is based on the information corresponding to the distance of the object obtained by the detection means and the data stored in the storage means. The optical apparatus according to claim 1, wherein focus correction control for moving the focus lens is performed.   The control means controls according to the size of the object obtained by the object detection means in the case of a zoom-out operation, and the detection result of the object detection means when the zoom-in operation is performed. The optical apparatus according to any one of claims 1 to 4, wherein the optical apparatus is not used. Obtaining data relating to the position of the focus lens according to the position of the zoom lens;
A focus correction step of moving the focus lens based on the data of the storage means for focus correction control accompanying the movement of the zoom lens,
In the correction step, the focus correction is performed according to the size of an object obtained from an image.

Images