JP4593702B2 - Optical apparatus and recording medium - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a memory medium storing a control program to be subjected to an optical apparatus and a control having an automatic focusing function.
[0002]
[Prior art]
Examples of optical devices having an autofocus (hereinafter also referred to as AF) function include a video camera, a silver salt camera, and an electronic still camera. The AF control method is described in, for example, Japanese Patent Laid-Open No. 62-103616.
[0003]
[Problems to be solved by the invention]
In recent years, higher image quality of captured images and higher magnification of lenses have been advanced, and higher performance of an AF function for expanding the range of subjects that can be photographed has been demanded.
[0004]
However, with the conventional AF function, there are subjects that are easy to focus and subjects that are difficult to focus, and there is variation in AF performance depending on the subject.
[0005]
For example, when shooting a low-brightness subject with a setting suitable for a high-brightness subject, the AF operation starts slowly from a state where the amount of blurring is large (a state where the focus shift is large). It may not be found. On the other hand, when shooting a high-brightness subject with a setting suitable for a low-brightness subject, there is a problem that the AF operation stops when the focus near the focused state is slightly sweet.
[0006]
Therefore, conventionally, an eclectic setting has been made to deal with both high-luminance subjects and low-luminance subjects. In other words, conventionally, AF signals are processed under certain conditions regardless of the luminance of the subject.
[0007]
However, since the above eclectic setting is not an optimal setting according to the subject condition, there is a limit to improving the AF performance, and it is necessary to cope with higher image quality of a captured image, higher lens magnification, and the like. It is disadvantageous.
[0008]
The present invention has been made in view of the above-described background, and an object of the present invention is to realize an autofocus function that is not easily affected by subject conditions, for example.
[0009]
[Means to solve the problem]
An optical apparatus according to a first aspect of the present invention is an optical apparatus having an autofocus function, and includes a video signal generating unit that generates a video signal of an image formed through the optical system, and luminance information of a subject. Brightness information acquisition means for acquiring amplifying characteristics based on the brightness information, amplifying means for amplifying the video signal according to the amplification characteristics, and driving the optical system based on the output of the amplification means Focus adjustment means for adjusting the focus, and the amplification means has a low frequency component amplification factor and a high frequency component amplification factor of the video signal when the luminance of the subject is the first luminance. When the first ratio of the amplification factor of the high-frequency component of the video signal to the sum of the first and second luminances is a second luminance lower than the first luminance, the amplification factor of the low-frequency component of the video signal and the video signal With the amplification factor of the high frequency component Wherein said amplification characteristic determined to be larger than the second ratio of the amplification factor of the high frequency component of the video signal to said amplifying means, when the luminance of the subject is a high brightness, of the video signal When the luminance of the subject is low so that the amplification factor of the high frequency component is larger than the amplification factor of the low frequency component of the video signal, the amplification factor of the low frequency component of the video signal is The amplification characteristic is determined so as to be larger than the amplification factor of the high-frequency component.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described. The present invention can be suitably applied to optical equipment such as a video camera, a silver salt camera, and an electronic still camera.
[0027]
[First Embodiment]
FIG. 1 is a diagram in which a part of an optical apparatus according to a preferred first embodiment of the present invention is extracted. The optical system 1 is a rear focus zoom lens having a four-group configuration including four lens groups. The optical system 1 includes a first lens group (front lens) 101 that is a fixed lens group, a second lens group (variator) 102 that has a zooming function that is a moving lens group, and a third lens group that is a fixed lens group. (Afocal) 103 and a fourth lens group 104 which is a moving lens group having both a focus function and a function as a compensator for correcting fluctuations in the image plane due to zooming. In general, each lens group is composed of a plurality of lenses, but the number of lenses in each lens group can be freely determined according to specifications. Note that the configuration of the optical system 1 does not limit the present invention, and other configurations may be employed.
[0028]
The imaging element 2 includes a photoelectric conversion element such as a CCD, for example, and converts an image formed through the optical system 1 into an electrical signal. For example, when the present invention is applied to an electronic camera such as a video camera or an electronic still camera, the image sensor 2 can also be used as an image sensor for photographing. For example, when the present invention is applied to a silver halide camera, a subject image is guided to the image sensor 2 via, for example, a mirror disposed between the optical system 1 and a film.
[0029]
The driver 4 drives the diaphragm member 3 to adjust the amount of light incident on the image sensor 2. For example, when the present invention is applied to an electronic camera, the driver 11 controls the diaphragm member 3 so that, for example, the amount of light incident on the image sensor 2 is within a predetermined range. For example, when the present invention is applied to a silver halide camera, the driver 11 controls the diaphragm member 3 according to, for example, a set or calculated diaphragm value.
[0030]
The drivers 10 and 11 drive the driving units 8 and 9 to move the moving lens groups 102 and 104, respectively, and adjust the magnification and focus. The drive parts 8 and 9 are comprised by a step motor etc., for example.
[0031]
The amplifier 12 amplifies the output signal of the image sensor 2 and supplies it to the process circuit 13. The process circuit 13 converts the signal supplied from the amplifier 12 into a signal such as an NTSC video signal, and further generates an AF video signal (AF signal) based on the signal, and the amplifier 12. And a luminance signal generation unit 17 that generates a luminance signal (for example, a signal indicating the average luminance in the screen) based on the signal supplied from. The AF signal and the luminance signal are supplied to the control unit 7.
[0032]
The control unit 7 includes an amplification unit 15 that amplifies the AF signal, an amplification characteristic determination unit 18 that determines amplification characteristics in the amplification unit 15, and the moving lens group 104 via the driver 11 according to the AF signal amplified by the amplification unit 15. And an AF unit 14 that adjusts the focus by moving the lens.
[0033]
The amplification characteristic determination unit 18 determines the amplification characteristic (for example, frequency characteristic) of the amplification unit 15 according to the luminance signal supplied from the luminance signal generation unit 17, and controls the amplification unit 15 to operate with the amplification characteristic. To do. The amplification unit 15 amplifies the AF signal supplied from the AF signal generation unit 16 according to the amplification characteristic determined by the amplification characteristic determination unit 18 and supplies the amplified AF signal to the AF unit 14.
[0034]
More specifically, in this embodiment, the amplification characteristic determination unit 18 determines the amplification factors for the low frequency component and the high frequency component of the AF signal supplied from the AF signal generation unit 16 according to the luminance signal. The amplifying unit 15 amplifies the low frequency component and the high frequency component according to each amplification factor according to the determination. As a result, variations in AF performance due to the brightness of the subject can be reduced.
[0035]
Here, when the amount of blur is large (when the amount of defocus is large), it is effective to use a low-frequency video signal to determine the direction of driving the optical system for focus adjustment. When the amount of blur is small (when the amount of defocus is small), it is effective to use a high-frequency video signal in order to find the true in-focus position. In this embodiment, since the mixed signal including both the low-frequency component and the high-frequency component is supplied as the AF signal from the amplification unit 15 to the AF unit 14, it is only necessary to reduce the variation in AF performance due to the luminance of the subject. Therefore, the probability and accuracy of focusing can be increased.
[0036]
The luminance signal generated by the luminance signal generation unit 17 is used as a signal for changing the amplification characteristic of the amplification unit 15 according to the subject condition (that is, a subject condition signal indicating the subject condition). Instead of or in addition to this luminance signal, another signal (for example, a signal indicating the contrast of the subject) may be used as the subject condition signal.
[0037]
As an AF method in the AF unit 14, for example, the sharpness of the subject image is detected based on the AF signal, and then the moving lens 104 for focus adjustment is driven to again determine the sharpness of the subject image based on the AF signal. Based on the change of the sharpness at this time, the driving direction (moving direction) of the moving lens 104 is determined and the moving lens 104 is driven. Hereinafter, the moving lens 104 is moved to a position where the sharpness of the subject image is maximized. There is a method of driving.
[0038]
FIG. 2 is a diagram for explaining the ratio between the amplification factor of the low frequency component and the amplification factor of the high frequency component when the amplification unit 15 amplifies the AF signal when the subject has low luminance. 2A, 2B, and 2E are examples when the ratio is not appropriate, and FIGS. 2C, 2D, and 2F are amplification characteristic setting units 18 based on this embodiment. This is an example in the case where the ratio is appropriately set.
[0039]
FIG. 2E shows that the amplification factor of the low frequency component: the amplification factor of the high frequency component is 50%: 50%. FIG. 2A shows an in-focus level (for example, amplified) when an AF operation is executed based on an AF signal in which the low frequency component and the high frequency component are amplified with the amplification factor of the ratio shown in FIG. It is an example showing the relationship between the sharpness of the subject image calculated based on the AF signal and the focus position (or the position of the moving lens 104). FIG.2 (b) is the figure which expanded the (circle) part of Fig.2 (a). This circled portion indicates a state where the amount of blur is large. If the subject has low brightness and the low frequency component is small, the focus level curve is flat when the amount of blur is large, so even if the focus adjustment moving lens 104 is driven to the close side, the infinity side Since the in-focus level does not change even when the lens is driven, the driving direction of the moving lens 104 cannot be determined.
[0040]
Therefore, in this embodiment, when the subject has a low luminance, as shown in FIG. 2 (f), the amplification factor of the low frequency component and the high frequency component so that the ratio of the amplification factor of the low frequency component becomes high. The ratio with the amplification factor is set to 70%: 30%, for example. FIG. 2C shows the relationship between the focus level and the focus position when the AF operation is executed based on the AF signal in which the low frequency component and the high frequency component are amplified with the amplification factor of the ratio shown in FIG. It is an example which shows. FIG.2 (d) is the figure which expanded the (circle) part of FIG.2 (c). This circled portion indicates a state where the amount of blur is large. In this way, when the subject has low luminance, as shown in FIG. 2F, the ratio of the amplification factor of the low frequency component is increased so that the moving lens for focus adjustment even in a state where the amount of blur is large. Since the focus level is changed by driving 104, the subject image can be correctly focused.
[0041]
FIG. 3 is a diagram for explaining the ratio between the amplification factor of the low frequency component and the amplification factor of the high frequency component when the amplification unit 15 amplifies the AF signal when the subject has high brightness. 3A, 3B, and 3E are examples in which the ratio is not appropriate, and FIGS. 3C, 3D, and 3F are amplification characteristic setting units 18 based on this embodiment. This is an example in the case where the ratio is appropriately set.
[0042]
FIG. 3E shows that the amplification factor of the low frequency component: the amplification factor of the high frequency component is 50%: 50%. FIG. 3A shows the relationship between the focus level and the focus position when the AF operation is executed based on the AF signal in which the low frequency component and the high frequency component are amplified with the amplification factor of the ratio shown in FIG. It is an example which shows. FIG.3 (b) is the figure which expanded the (circle) part of Fig.3 (a). The circles indicate the vicinity of the in-focus state. If the high-frequency component is small when the subject has high brightness, the focus level curve is flat in the vicinity of the in-focus state, so even if the focus adjustment moving lens 104 is driven to the closest side, it will move to the infinity side. Since the focus level does not change even when driven, the true focus position cannot be determined. When the subject has high brightness, the driving direction of the optical system can be determined even when the amount of blur is large.
[0043]
Therefore, in this embodiment, when the subject has high luminance, as shown in FIG. 3 (f), the amplification factor of the low frequency component and the high frequency component are increased so that the ratio of the amplification factor of the high frequency component becomes high. The ratio with the amplification factor is set to 30% and 70%, for example. FIG. 3C shows the relationship between the focus level and the focus position when the AF operation is executed based on the AF signal in which the low frequency component and the high frequency component are amplified with the amplification factor of the ratio shown in FIG. It is an example which shows. FIG. 3D is an enlarged view of the circled portion in FIG. The circles indicate the vicinity of the in-focus state. As described above, when the subject has high luminance, as shown in FIG. 3F, the true in-focus position can be determined by increasing the ratio of the amplification factor of the high-frequency component.
[0044]
FIG. 4 is a diagram conceptually showing processing in the amplification characteristic determination unit 18 and the amplification unit 15. (C), (a), and (b) in FIG. 4 are respectively an AF signal generated by the AF signal generation unit 16 of the process circuit 13, a low frequency component of the AF signal, and a high frequency component of the AF signal. is there.
[0045]
In the example illustrated in FIG. 4, the amplification characteristic determination unit 18 determines the amplification factor for the low frequency component as 6 dB and the amplification factor for the high frequency component as 4 dB based on the luminance signal supplied from the luminance signal generation unit 17.
[0046]
(D) in FIG. 4 is a signal obtained by amplifying the low frequency component shown in (a) with the amplification factor (6 dB) for the low frequency component in the amplifying unit 15, and (e) is shown in (b). This is a signal obtained by amplifying a high frequency component at a high frequency component amplification factor (4 dB). Further, (f) is a signal obtained by mixing the signals shown in (d) and (e) in the amplification unit 15 and is an AF signal finally supplied to the AF unit 14.
[0047]
The amplification factor for the low frequency component and the amplification factor for the high frequency component may be determined based on, for example, a table stored in a memory (not shown), or a function (brightness is a variable) incorporated in the control program. It may be determined by executing an operation based on a function) or by another method.
[0048]
Further, the amplification factor for the low frequency component and the amplification factor for the high frequency component are determined in consideration of other information in addition to the luminance information of the subject (that is, the luminance signal supplied from the luminance signal generation unit 17). Alternatively, it may be determined based on information other than luminance information.
[0049]
FIG. 5 is a diagram illustrating a setting example of the amplification factor for the low frequency component and the amplification factor for the high frequency component. In this example, as the subject becomes brighter, the ratio of the high frequency component amplification factor ([high frequency component amplification factor] / ([high frequency component amplification factor] + [low frequency component amplification factor])) is increased. .
[0050]
FIG. 6 is a flowchart showing an operation flow of the control unit 7. In step S11, the amplification characteristic determination unit 18 reads the luminance signal from the luminance signal generation unit 17, and in step S12, the amplification characteristic determination unit 18 sets the amplification factors of the low frequency component and the high frequency component based on the luminance signal. It is determined (as a result, the ratio of the two amplification factors is determined), and each amplification factor related to the determination is set in the amplification unit 15.
[0051]
In step S13, the amplification unit 15 amplifies the low-frequency component and the high-frequency component of the AF signal supplied from the AF signal generation unit 16 at a set amplification factor, and mixes the amplified components for amplification. The generated AF signal is generated.
[0052]
In step S14, it is determined whether or not the AF function is set to ON by referring to the state of a setting unit (not shown). If the AF function is set to ON, the process proceeds to step S15 and OFF. If the status is set, the process ends.
[0053]
In step S15, the AF unit 14 is caused to perform calculation for AF control based on the amplified AF signal. In step S16, it is determined based on the calculation result in step S15 whether or not it is in focus. If it is in focus, the process ends. If it is not in focus, the process proceeds to step S17.
[0054]
In step S17, the AF unit 14 controls the driver 11 according to the calculation result of step S15. Thereby, the moving lens 104 for focus adjustment is driven.
[0055]
[Second Embodiment]
FIG. 7 is a diagram in which a part of an optical apparatus according to the preferred second embodiment of the present invention is extracted. The optical device according to this embodiment relates to an interchangeable lens type camera and is used in a state where the lens unit 100 and the camera unit 200 are coupled. In addition, the same code | symbol is attached | subjected to the component which has a function substantially the same as the component of the optical apparatus which concerns on 1st Embodiment shown in FIG.
[0056]
The lens unit 100 includes an optical system 1, driving units 8 and 9, drivers 4, 10 and 11, and a control unit 7. The camera unit 200 includes an image sensor 2, an amplifier 12, a process circuit 13, and a lens control unit 20. The control unit 7 of the lens unit 100 and the lens control unit 20 of the camera unit 200 are connected by a lens side contact 21 and a camera side contact 22 and can communicate with each other.
[0057]
The lens control unit 20 of the camera unit 200 outputs signals from the process circuit 13 and the like (an AF signal, a luminance signal, a signal for controlling the diaphragm member 3, a signal for controlling the moving lens 102 for zooming, the camera unit 200). (Including information indicating the type of the lens unit 100) is transmitted to the control unit 7 of the lens unit 100, and information on the lens unit 100 (for example, information indicating the type of the lens unit 100) is received from the control unit 7.
[0058]
In addition to the functions described in the first embodiment, the amplification characteristic determination unit 18 according to this embodiment has, for example, an amplification characteristic (for example, a low level) to be set in the amplification unit 15 according to the type of the camera unit 200. It is preferable to have a function of changing a rule (for example, a table) for determining the frequency component and the amplification factor of the high frequency component. Thereby, optimal AF control according to each specification of the lens unit 100 and the camera unit 200 can be realized.
[0059]
FIG. 6 is a flowchart showing an operation flow of the control unit 7 of the lens unit 100. The operation of the control unit 7 according to this embodiment is that the luminance signal is acquired from the luminance signal generation unit 17 of the process circuit 13 via the contacts 21 and 22 and the lens control unit 20 in step S11, and step S13. 3 except that the AF signal is acquired from the AF signal generation unit 16 of the process circuit 13 via the contacts 21 and 22 and the lens control unit 20, substantially the same as the operation of the control unit 7 according to the first embodiment. Are the same.
[0060]
[Third Embodiment]
FIG. 8 is a diagram in which a part of an optical apparatus according to the preferred third embodiment of the present invention is extracted. This embodiment is different from the optical apparatus according to the second embodiment in that the amplification unit 15 and the amplification characteristic determination unit 18 are provided on the camera unit 200 side. With this change, the amplification unit 15 and the amplification characteristic determination unit 18 in the control unit 7 ′ of the lens unit 100 are deleted, and the amplification unit 15 and the amplification characteristic determination unit 18 are provided in the lens control unit 20 ′ of the camera unit 200. It has been.
[0061]
The control unit 7 ′ of the lens unit 100 and the lens control unit 20 ′ of the camera unit 200 are connected by a lens side contact 21 and a camera side contact 22 and can communicate with each other.
[0062]
The lens control unit 20 ′ of the camera unit 200 includes an AF signal obtained by amplifying the AF signal generated by the AF signal generation unit 16 of the process circuit 13 by the amplification unit 15, a signal for controlling the diaphragm member 3, and movement for zooming. Signals for controlling the lens 102, information indicating the type of the camera unit 200, and the like are transmitted to the control unit 7 ′ of the lens unit 100, and information on the lens unit 100 (for example, information indicating the type of the lens unit 100). Is received from the control unit 7 ′.
[0063]
In addition to the functions described in the first embodiment, the amplification characteristic determination unit 18 according to this embodiment has, for example, an amplification characteristic (for example, a low level) to be set in the amplification unit 15 according to the type of the lens unit 100. It is preferable to have a function of changing a rule (for example, a table) for determining the frequency component and the amplification factor of the high frequency component. Thereby, optimal AF control according to each specification of the lens unit 100 and the camera unit 200 can be realized.
[0064]
FIG. 6 is a flowchart showing a flow of operations controlled in cooperation by the control unit 7 ′ of the lens unit 100 and the lens control unit 20 ′ of the camera unit 200. Steps S11 to S13 are executed by the lens control unit 20 ′, steps S15 to S17 are executed by the control unit 7 ′ under the control of the lens control unit 20 ′, and step S14 is executed by the lens control unit 20 ′ and / or Alternatively, it is executed by the control unit 7 ′.
[Other embodiments]
An object of the present invention is to supply a storage medium (or recording medium) in which a program code of software that realizes the functions of the above-described embodiments is recorded to a system or apparatus, and a computer (or CPU or MPU) of the system or apparatus. Needless to say, this can also be achieved by reading and executing 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 also an operating system (OS) running on the computer based on the instruction of the program code. It goes without saying that a case where the function of the above-described embodiment is realized by performing part or all of the actual processing and the processing is included.
[0065]
Furthermore, after the program code read from the storage medium is written into a memory provided in a function expansion card inserted into the computer or a function expansion unit connected to the computer, the function is based on the instruction of the program code. It goes without saying that the CPU or the like provided in the expansion card or the function expansion unit performs part or all of the actual processing, and the functions of the above-described embodiments are realized by the processing.
[0066]
【The invention's effect】
According to the present invention, for example, it is possible to realize an autofocus function that is not easily affected by subject conditions.
[Brief description of the drawings]
FIG. 1 is a diagram in which a part of an optical apparatus according to a preferred first embodiment of the present invention is extracted.
FIG. 2 is a diagram for explaining a ratio between a low-frequency component amplification factor and a high-frequency component amplification factor when an amplification unit amplifies an AF signal when a subject has low luminance.
FIG. 3 is a diagram for explaining a ratio between an amplification factor of a low frequency component and an amplification factor of a high frequency component when an amplification unit amplifies an AF signal when a subject has high brightness.
FIG. 4 is a diagram conceptually illustrating processing in an amplification characteristic determination unit and an amplification unit.
FIG. 5 is a diagram illustrating a setting example of an amplification factor for a low frequency component and an amplification factor for a high frequency component.
FIG. 6 is a flowchart showing a flow of AF control.
FIG. 7 is a diagram obtained by extracting a part of an optical apparatus according to a preferred second embodiment of the present invention.
FIG. 8 is a diagram obtained by extracting a part of an optical apparatus according to a preferred third embodiment of the present invention.

Claims (2)

An optical instrument having an autofocus function,
Video signal generating means for generating a video signal of an image formed through the optical system;
Luminance information acquisition means for acquiring luminance information of the subject;
Amplifying means for determining an amplification characteristic based on the luminance information, and amplifying the video signal according to the amplification characteristic;
Focus adjusting means for adjusting the focus by driving the optical system based on the output of the amplifying means;
With
The amplification means amplifies the high frequency component of the video signal with respect to the sum of the amplification factor of the low frequency component of the video signal and the amplification factor of the high frequency component of the video signal when the luminance of the subject is the first luminance. The video signal with respect to the sum of the low-frequency component amplification factor and the high-frequency component amplification factor of the video signal when the first ratio is a second luminance lower than the first luminance. Determining the amplification characteristic to be larger than the second ratio of the amplification factor of the high-frequency component of
When the luminance of the subject is high , the amplifying unit adjusts the luminance of the subject so that the amplification factor of the high frequency component of the video signal is larger than the amplification factor of the low frequency component of the video signal. An optical apparatus characterized in that, when the luminance is low , the amplification characteristic is determined so that an amplification factor of a low frequency component of the video signal is larger than an amplification factor of a high frequency component of the video signal. A video signal generating means for generating a video signal of an image formed through the optical system, an amplifying means for amplifying the video signal, and adjusting the focus by driving the optical system based on the output of the amplifying means. A computer-readable recording medium that records a control program for an optical apparatus that includes a focus adjustment unit that
The control program is stored in the computer.
A luminance information acquisition step for acquiring luminance information of the subject;
An amplification characteristic determining step for determining an amplification characteristic of the amplification means based on the luminance information;
And execute
In the amplification characteristic determining step, the high-frequency component of the video signal with respect to the sum of the amplification factor of the low-frequency component of the video signal and the amplification factor of the high-frequency component of the video signal when the luminance of the subject is the first luminance The gain of the low-frequency component of the video signal and the gain of the high-frequency component of the video signal when the first ratio of the gain is a second brightness lower than the first brightness. Determining the amplification characteristic to be larger than the second ratio of the amplification factor of the high-frequency component of the video signal;
In the amplification characteristic determination step, when the luminance of the subject is high , the amplification of the high-frequency component of the video signal is larger than the amplification factor of the low-frequency component of the video signal. When the luminance is low , the amplification characteristic is determined so that an amplification factor of a low frequency component of the video signal is larger than an amplification factor of a high frequency component of the video signal. .

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