JP2013156603A - Imaging apparatus including automatic focus lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an imaging apparatus capable of performing proper focus correction, even under such a condition that AF tracking is extremely difficult, that is, an object is moved at high speed with respect to a camera and the change of a subject distance is large.SOLUTION: A lens including range-finding means and calculation means, calculating a focus position, based on the information of the range-finding means by the calculation means, and driving a focus movement group includes pan/tilt detection means and adds a predetermined focus correction amount based on a pan/tilt detection value to the calculated focus position, to drive the focus movement group.

Description

  The present invention relates to an imaging device having a lens having an autofocus function, and is suitable for a broadcast television camera, a video camera, a digital still camera, a silver salt photography camera, and the like.

  In a lens having an autofocus (hereinafter referred to as AF) function, a processing time delay occurs when distance information or focus information is detected. Therefore, when a subject moving at a high speed is photographed, the image becomes out of focus. Therefore, as shown in FIG. 5, a technique for compensating for a delay in processing time by calculating a subject speed from changes to subject distances A to B in unit time t and predicting a subject distance C after time t ′, so-called Predictive AF technology is widely known (for example, Patent Document 1).

  Further, when the speed of the subject changes greatly in a short time, as shown in FIG. 6, it is used for prediction when the speed change is small as A1 to B2 and when the speed change is large as A2 to B2. A technique has been proposed in which the time is variable and the focus position prediction accuracy is improved (Patent Document 2).

JP 63-118133 A JP-A-6-130284

  However, as shown in FIG. 9, when the subject moves at a high speed with respect to the camera and the change in the subject distance is large as in the case where the car race is shot while panning (tilting) on the side of the course, Patent Document 1, It was difficult to focus with the technique of Patent Document 2. Not only is the subject speed high, but as shown in FIG. 7 (graph relating to subject distance change in FIG. 9), the relative speed with respect to the camera once becomes zero at the point β, and after passing through the point β Is due to the relative speed in the reverse direction. FIG. 8 shows the focus correction amount under the shooting conditions of FIG. In general, the change in the amount of extension of the focus lens group becomes larger as the subject is closer, so the focus correction amount increases from the point α toward the point β and becomes maximum immediately before the point β. Then, immediately after passing through the point β, the focus correction amount in the minus direction becomes maximum, and thereafter, the focus correction amount gradually decreases toward the point γ. Therefore, the fluctuation of the focus correction amount is particularly large before and after the point β, and it is very difficult to predict the movement of the subject.

  However, in the case of car race shooting as described above, since the course and the camera installation location are determined in advance, there is a correlation between the camera pan (tilt) angle and the relative speed of the subject, as shown in FIG. It is possible to associate the focus correction amount with the pan (tilt) angle.

  The present invention enables appropriate focus correction even when the subject moves at a high speed with respect to the camera and the subject distance changes greatly and the AF is extremely difficult to follow, as in the car race shooting described above. An object of the present invention is to provide an imaging apparatus.

  The imaging apparatus of the present invention includes a distance measuring means and a computing means, calculates a focus position by the computing means based on information of the distance measuring means, and has a pan / tilt detection means in a lens that drives the focus movement group, A predetermined focus correction amount based on a pan / tilt detection value is added to the calculated focus position, and the focus movement group is driven.

  According to the present invention, an imaging apparatus capable of performing appropriate focus correction even under a condition in which AF is extremely difficult to follow, such as a subject moving at a high speed with respect to the camera and a large change in subject distance. Is obtained.

1 is a diagram illustrating a configuration of an image pickup apparatus having a zoom lens according to Embodiment 1. FIG. Flow chart of the first embodiment FIG. 5 is a diagram illustrating a configuration of an imaging apparatus having a zoom lens according to a second embodiment. Flow chart of embodiment 2 Explanatory drawing of patent document 1 Explanatory drawing of patent document 2 Figure showing the relationship between subject distance and time for car race shooting The figure which shows the relationship between the focus correction amount of the car race photography and the pan (tilt) of the camera Illustration of car race shooting

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

Example 1
FIG. 1 shows a configuration of an imaging apparatus according to the first embodiment of the present invention. In FIG. 1, 100 is a zoom lens, 200 is a camera, and 300 is a tripod. The zoom lens 100 is attached to the camera 200, and the camera 200 is attached to a tripod 300 in an exchangeable manner.

  Reference numeral 10 denotes an AF detection unit which detects a defocus (focus shift) amount on a predetermined detection surface. The arithmetic circuit 20 of the zoom lens 100 mainly includes an AF evaluation value calculation unit 30, a focus drive amount calculation unit 40, a tripod information reception unit 50, and a focus correction control unit 60. 120 is a focus position detector, and 130 is a zoom position detector. Reference numeral 140 denotes a focus drive amount memory in which the correspondence between the focus drive amount and the defocus change amount at each focus / zoom position is recorded.

  On the other hand, pan / tilt information that is a shooting angle is acquired by the pan / tilt information acquisition unit 310 and sent from the tripod information transmission unit 320 to the zoom lens 100. The zoom lens 100 receives the pan / tilt information, adds a correction value to the focus drive amount in the arithmetic circuit 20, issues a command to the focus drive unit 70, and drives the focus movement group.

  In FIG. 1, so-called phase difference AF for calculating the focus drive amount from the TTL defocus amount is assumed, but the same effect can be obtained by using other distance measuring means.

  FIG. 2 is a flowchart showing a flow in which the imaging apparatus having the zoom lens shown in FIG. 1 performs an AF operation.

  First, the zoom lens 100 is powered on and initialized (step S10). Then, the AF evaluation value calculation unit 30 calculates the defocus amount from the value detected by the AF detection unit 10, sets it as a focus correction amount target value, and transmits it to the focus drive amount calculation unit 40 (step S20).

  On the other hand, communication between the zoom lens 100 and the tripod 300 is established, and if communication is established, the process proceeds to step S40. If communication is not established, the process proceeds to step S80 (step S30). When communication is established, the pan / tilt information acquisition unit 310 at the contact point of the tripod 300 and the camera 200 acquires pan / tilt information that is the shooting angle of the zoom lens 100, and the tripod information transmission unit 320 sends it to the tripod information reception unit 50. (Step S40). The pan / tilt information of the zoom lens 100 is sent to the focus correction control unit 60, and whether the subject is facing or away from the zoom lens 100 (is not exceeding β in FIGS. 7 to 9) (Step S50). Based on the result of determination in step S50, the focus drive amount calculation unit 40 sets the target value calculated in step S20 when the subject is directed from the point α shown in FIGS. On the other hand, the target value is shifted to the minus side (closest side) (step S60). When the subject is moving away from the point β shown in FIGS. 7 to 9 in the γ direction, the target value is shifted to the plus side (infinite side) as opposed to step S60 (step S70).

  On the other hand, the focus drive amount calculator 40 reads the focus / zoom position from the focus position detector 120 and the zoom position detector 130 (step S80). Then, the amount of focus deviation with respect to the minute change of the predetermined focus at the focus / zoom position in step S80 is read from the focus drive amount memory 140 (step S90). Here, in order to correct the focus to the target value shifted in step S60 or S70 (or the target value in step S20 if communication is not established in S30), the amount of focus deviation with respect to the minute focus change read in step S90 is set. The focus driving amount is used and calculated (step S100). Finally, the focus drive amount in step S100 is sent to the focus drive unit 70 to drive the focus lens group (step S110).

  By adopting the above configuration, it is possible to perform appropriate focus correction even under conditions where the subject moves at a high speed with respect to the camera, the subject distance changes greatly, and AF is extremely difficult to follow. An imaging device can be obtained.

(Example 2)
FIG. 3 shows a configuration of an image pickup apparatus having a zoom lens according to the second embodiment of the present invention. In FIG. 3, 100 is a zoom lens, 200 is a camera, and 300 is a tripod. The zoom lens 100 is attached to the camera 200, and the camera 200 is attached to a tripod 300 in an exchangeable manner.

  Reference numeral 10 denotes an AF detection unit that detects a defocus amount on a predetermined detection surface. The arithmetic circuit 20 of the zoom lens 100 mainly includes an AF evaluation value calculation unit 30, a focus drive amount calculation unit 40, a tripod information reception unit 50, and a focus drive amount correction value calculation unit 90. 120 is a focus position detector, and 130 is a zoom position detector. Reference numeral 140 denotes a focus drive amount memory in which the correspondence between the focus drive amount and the defocus change amount at each focus / zoom position is recorded.

  On the other hand, pan / tilt information, which is a shooting angle, is acquired by the pan / tilt information acquisition unit 310 and sent from the tripod information transmission unit 320 to the zoom lens.

  The mode switching unit 80 switches between the shooting mode and the focus correction amount acquisition mode, calculates the focus correction amount from the AF evaluation value in each pan / tilt state in the focus correction amount acquisition mode, and stores it in the focus drive amount correction value memory 110. Write. In the photographing mode, the arithmetic circuit 20 of the zoom lens reads the focus correction amount from the focus drive amount correction value memory 110, issues a command to the focus drive unit 70, and drives the focus movement group.

  In FIG. 3, so-called phase difference AF for calculating the focus drive amount from the TTL defocus amount is assumed, but the same effect can be obtained by using other distance measuring means.

  FIG. 4 is a flowchart illustrating a flow in which the imaging apparatus having the zoom lens illustrated in FIG. 3 performs an AF operation.

  First, the zoom lens 100 is powered on and initialized (step S10). Then, the AF evaluation value calculation unit 30 calculates the defocus amount from the value detected by the AF detection unit 10, sets it as a focus correction amount target value, and transmits it to the focus drive amount calculation unit 40 (step S20). The focus drive amount calculation unit 40 reads the focus / zoom position from the focus position detection unit 120 and the zoom position detection unit 130 (step S30). Then, the amount of focus deviation with respect to the minute change of the predetermined focus at the focus / zoom position in step S80 is read from the focus drive amount memory 140 (step S40).

  On the other hand, communication between the zoom lens 100 and the tripod 300 is established, and if communication is established, the process proceeds to step S60. If communication is not established, the process proceeds to step S140 (step S50). When communication is established, the pan / tilt information acquisition unit 310 at the contact point of the tripod 300 and the camera 200 acquires pan / tilt information that is the shooting angle of the zoom lens 100, and the tripod information transmission unit 320 sends it to the tripod information reception unit 50. (Step S60). Then, according to the mode information of the mode switching unit 80, each processing of the focus correction amount acquisition mode and the photographing mode (focus correction amount acquisition mode OFF) is performed (step S70). In the focus correction amount acquisition mode, first, the focus drive amount calculation unit calculates the focus drive amount for the correction amount target value set in step S20 (step S80). Then, the focus drive amount in step S80 is sent to the focus drive unit 70 to drive the focus lens group (step S90). Then, the AF evaluation value calculation unit 30 calculates the defocus amount from the value detected by the AF detection unit 10 again. The focus correction amount calculation unit inverts the sign of the defocus amount (focus shift amount) at this time to obtain a focus correction amount (step S100). The focus correction amount calculated in step S100 is written into the focus correction amount memory 110 together with the pan / tilt information acquired in step S60 (step S110).

  In the shooting mode (focus correction amount acquisition mode OFF), the focus drive amount calculation unit 40 reads the focus correction amount corresponding to the pan / tilt amount acquired in step S60 from the focus correction amount memory 110 (step S120). Subsequently, the focus correction amount read in step S120 is added to the target value set in step S20, and the value is reset as a new target value (step S130). Then, in order to correct the focus to the target value reset in step S130 (or the target value in step S20 if communication is not established in S50), the defocus amount for the predetermined small focus change read in step S40 is set. The focus driving amount is used and calculated (step S140). Finally, the focus drive amount in step S140 is sent to the focus drive unit 70 to drive the focus lens group (step S150).

  By adopting the configuration as described above, not only the correction processing in the vicinity of the point β in FIGS. 7 to 9 as in the first embodiment, but also the AF function capable of appropriately performing correction processing in a wider range. An imaging device having a lens provided with can be obtained.

10 ... AF detector
20: Arithmetic circuit
30 ... AF evaluation value calculation unit
40: Focus drive amount calculator
50 ... Tripod information receiver
60: Focus correction controller
70 ・ ・ ・ Focus drive unit
80 ・ ・ ・ Mode switching part
90 ・ ・ ・ Focus correction amount calculator
100 ... zoom lens
110: Focus correction amount memory
120 ... Focus position detector
130 ... Zoom position detector
140: Focus drive amount memory
200 ... Camera
300 ... tripod
310: Pan / tilt information acquisition unit
320 ... Tripod information transmitter

Claims (3)

A lens that includes a distance measuring means and a computing means, calculates a focus position by the computing means based on information of the distance measuring means, and has a pan / tilt detection means in a lens that drives the focus movement group. An image pickup apparatus that drives a focus movement group by adding a predetermined focus correction amount based on a pan / tilt detection value.
  A recording unit that records the pan / tilt detection value and a focus correction amount in association with each other, and adds a focus correction amount recorded in the recording unit to the calculated focus position according to the pan / tilt detection value; The imaging apparatus according to claim 1, wherein the moving group is driven. 3. The focus correction amount acquisition mode is provided, and when shooting is performed in the focus correction amount acquisition mode, the pan / tilt detection value and the focus correction amount can be recorded in association with each other. Imaging device.