JP4088943B2 - Zoom lens iris control method and zoom lens - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a zoom lens iris control method and a zoom lens, and more particularly, to a ramping correction technique applied to iris electric motor control of a zoom lens used in a broadcast television camera.
[0002]
[Prior art]
In general, a zoom lens used in a television camera has a characteristic that when the zoom magnification becomes larger than a certain magnification value (threshold value), the open F number of the lens increases (the lens becomes dark) according to the zoom magnification. . This is because the effective aperture (incidence pupil diameter) of the lens increases as you zoom to the telephoto side, but it cannot exceed the diameter of the front lens, and the incident light is limited by the front lens diameter from a certain focal length. by. This phenomenon is called ramping or F-drop. At this time, when the indicated value of the iris is smaller than the F-number, the optical performance is improved by narrowing down to a value that does not affect the actual brightness ( What performs ramping correction) is known.
[0003]
For example, the lens shown in FIG. 3 has an open FNo. 2.0 of 1 ×, the lens gradually becomes darker in a region of a certain magnification value m or more, and FNo. 4.0 when the zoom magnification is 50 ×. It becomes. FIG. 4 shows that the aperture instruction value is FNo. 2.0 and FNo. The actual aperture movement at 2.8 is shown. When the ramping correction is not performed, as shown by the dotted lines (1) and (2) in FIG. 2.0 or FNo. Maintained at 2.8. On the other hand, when the ramping correction function is activated, as shown by the solid line (3) or the alternate long and short dash line (4) in FIG. 4, in accordance with the change in the open F number of the lens in the high magnification region above the threshold (m). The aperture is narrowed down.
[0004]
That is, a television lens having a ramping correction function, as shown in FIG. 5, in the case of an aperture instruction value (a hatched range in the figure) smaller than a graph line (ramping line) indicating a change in the open F number of the lens, A ramping correction is applied to restrict the iris from moving in the opening direction from the ramping line.
By the way, there are generally two modes for the iris electric operation mode of the TV camera lens: auto (automatic) and remote (remote manual), and the auto mode sets the gain of the iris amplifier in the lens smaller than the remote mode. There are many. This is because a general auto iris system employs a circuit configuration as shown in FIG. That is, when the changeover switch 12 of the camera 10 is set to the auto-side terminal 12A, the video signal level indicating the brightness of the screen is from the terminal (brightness signal terminal) 14 via the signal processing unit 16 to the lens 20 side. Sent to. In such an auto mode, it is necessary to amplify the signal in the process of performing the calculation or the like in the signal processing unit 16, and the signal processing unit 16 includes an amplification unit corresponding to the amplifier 26.
[0005]
On the other hand, when the changeover switch 12 is set to the remote terminal 12B, a command signal from the brightness adjustment knob 22 is sent to the lens 20 side. Note that the command signal from the brightness adjustment knob 22 is also input to the addition circuit 24 of the signal processing unit 16, and “brightness” or “ “Dark” can be finely adjusted.
[0006]
On the other hand, the lens 20 connected to the camera 10 includes an arithmetic circuit 30 and an iris amplifier 32, and a signal (iris position instruction value Id) input from the camera 10 and a detection signal (iris position Ip) from the aperture position detector 34. Are added by the arithmetic circuit 30 and output to the iris amplifier 32. The iris control signal amplified by the iris amplifier 32 is applied to the iris driving motor 36, and the driving force of the motor 36 is transmitted to the iris 38 via a transmission mechanism (not shown), so that the iris 38 is expanded or contracted. It has a structure.
[0007]
In the auto iris system configured as described above, in the remote mode, the gain of the iris amplifier 32 is set high in order to obtain high followability to manual operation, whereas in the auto mode, the operation of the amplifier 26 of the camera 10 is performed. Since the signal input to the lens 20 is amplified by the above, it is necessary to lower the gain of the iris amplifier 32 on the lens 20 side. Therefore, the gain β of the iris amplifier 32 is switched between a high level (H) and a low level (L) in conjunction with the changeover switch 12 that switches the connection contact in response to auto / remote mode selection. In the auto mode, the gain β of the iris amplifier 32 is set smaller than that in the remote mode.
[0008]
FIG. 7 shows the configuration of a ramping correction circuit mounted on a conventional television lens. The iris position indication value (Id) output from the camera 10 to the lens 20 via the auto-side contact 12A or the remote-side contact 12B of the changeover switch 12 of the camera 10 is input to the arithmetic circuit 40 of the lens 20. On the other hand, a detection signal indicating the zoom group position detected by the zoom group position detector 42 provided on the lens is applied to the arithmetic circuit 40 via the level shift circuit 44. The arithmetic circuit 40 obtains the open F number of the lens corresponding to the zoom group position Z based on the data of the ramping line, and compares the indicated value Id of the iris position input from the camera 10 with the open F number. The presence / absence of the correction operation is determined, and the iris instruction value is output to the second arithmetic circuit 46.
[0009]
A detection signal (iris position Ip) from the iris position detector 48 is added to the second arithmetic circuit 46, where an error amount between the iris instruction value and the current iris position is calculated. Then, an iris control signal corresponding to the difference between the iris instruction value and the current iris position is output to the iris amplifier 32. The iris amplifier 32 can be switched between two levels, that is, a high level (H) or a low level (L) by the selection signal of the auto / remote selection switch 50. The gain β is set to a small value.
[0010]
[Problems to be solved by the invention]
However, when the ramping correction operation is performed with such a conventional auto iris system, the iris amplifier 32 has a small gain in the auto mode, so that the position of the iris cannot be accurately controlled, and the iris cannot be reduced to the actual brightness. This problem occurs. For this reason, the ramping correction becomes insufficient, and the optical performance cannot be sufficiently improved.
[0011]
The present invention has been made in view of such circumstances, and provides an iris control method for a zoom lens that can improve the accuracy of ramping correction in the auto mode and can also perform normal auto operation normally. In addition, an object of the present invention is to provide a zoom lens that embodies the iris control method.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 has an auto iris mode in which the aperture is automatically controlled to an optimum value appropriately based on a signal indicating the brightness of the screen, and the indication value indicating the iris position is a lens. In a zoom lens having a ramping correction function that reduces the aperture to a value substantially equal to the open F number when the aperture is smaller than the open F number of the zoom lens, the instruction value indicating the iris position is greater than the open F number of the lens during the auto iris mode. When the normal auto iris operation is performed, the gain of the iris amplifier that amplifies the iris control signal is set to the first gain value, while the indicated value is smaller than the open F number of the lens, When executing the correction operation, the gain of the iris amplifier is higher than the first gain value. It is characterized by setting the second gain value.
[0013]
According to the present invention, in the normal auto operation range, the iris amplifier gain is set to be small and the auto operation is normally performed. On the other hand, even in the auto iris mode, the iris amplifier gain is set to be high in the range of the ramping operation. Enables high-precision control of the aperture position. Thereby, the accuracy of the ramping correction can be improved.
In order to achieve the above object, the invention according to claim 2 is an auto iris mode in which the aperture is automatically controlled to an optimum value appropriately based on a signal indicating the brightness of the screen, and the aperture is operated according to manual operation of the operation unit. A zoom lens equipped with a ramping correction function capable of selecting the remote iris mode to be performed and narrowing the aperture to a value substantially equal to the open F-number when the indicated value indicating the iris position is smaller than the open F-number of the lens In the auto iris mode, if the indicated value indicating the iris position is larger than the open F number of the lens and the normal auto iris operation is executed, the gain of the iris amplifier that amplifies the iris control signal is set to the remote iris mode. While the first gain value is set lower than the time, the indicated value is the open F number of the lens. When performing a ramping correction operation, the gain of the iris amplifier is set to a second gain value that is higher than the first gain value as in the remote iris mode. .
[0014]
Conventionally, in a lens having two modes of the auto iris mode and the remote iris mode, the gain of the iris amplifier is set to be uniformly low at the time of auto iris. However, in the present invention, the ramping operation is performed even under the auto iris mode. In the range, the gain of the iris amplifier is set to a high value (second gain value) equivalent to that at the remote time. Accordingly, the position of the diaphragm can be accurately controlled during the ramping operation, and the accuracy of the ramping correction is improved.
[0015]
According to a third aspect of the present invention, in order to provide a zoom lens that embodies the above-described zoom lens iris control method, an auto iris mode that automatically controls the aperture to an optimal value appropriately based on a signal indicating the brightness of the screen is provided. And an instruction for instructing the iris position in a zoom lens having a ramping correction function for narrowing the iris to a value substantially equal to the open F number when the indicated value for instructing the iris position is smaller than the open F number of the lens. An instruction value input unit to which a signal corresponding to a value is input, an iris position detecting means for detecting an iris position indicating the current aperture value,
Control signal output means for outputting a control signal for controlling the iris driving means based on the instruction value input from the instruction value input section and the iris position detected by the iris position detection means, and issued from the control signal output means An iris amplifier that amplifies the received control signal and applies it to the iris driving means, a zoom position detecting means that detects a zoom position that indicates the current zoom magnification, and a ramping that indicates a change in the open F number of the lens with respect to a change in the zoom magnification A lens storage F-number at the zoom position detected by the zoom position detecting unit is obtained with reference to the data storage unit storing the line data and the data stored in the data storage unit, and input from the indicated value input unit Calculating means for comparing the indicated value and its open F number, and in the auto iris mode, the finger The instruction value input from the value input unit is larger than the open F number of the lens obtained by the calculation means, and when performing a normal auto iris operation, the gain of the iris amplifier is set to the first gain value. When the instruction value input from the instruction value input unit is smaller than the open F number of the lens obtained by the calculation means and a ramping correction operation is executed, the gain of the iris amplifier is set from the first gain value. And a gain control means for setting a higher second gain value.
[0016]
According to the present invention, the instruction value of the iris position is read from the instruction value input unit, and the current zoom position is read from the zoom position detecting means. The calculation means uses the ramping line data stored in the data storage unit to grasp the open F number of the lens at the current zoom position, and inputs the obtained open F number from the indicated value input unit. By comparing the indicated values, the magnitude relationship is determined. During the auto iris mode, when the indicated value is larger than the open F number of the lens, the gain control means sets the gain of the iris amplifier to the first gain value (small value), and executes the normal auto iris operation. When the instruction value is smaller than the open F number of the lens and the ramping correction operation is executed, the gain of the iris amplifier is set higher than the first gain value and set to the second gain value (large value).
[0017]
As described above, the accuracy of the ramping correction can be increased by setting the gain of the iris amplifier large in the range of the ramping operation even in the auto mode.
In the zoom lens according to the present invention, as described in claim 4, if the control signal output means, the calculation means, and the gain control means are configured by a one-chip CPU, the circuit configuration can be simplified. Can do.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
A preferred embodiment of an iris control method for a zoom lens and a zoom lens according to the present invention will be described below in detail with reference to the accompanying drawings.
FIG. 1 is a block circuit diagram showing an embodiment of the present invention. In the figure, parts that are the same as those in the conventional configuration described in FIG. 6 and FIG. In the zoom lens 60 according to the present embodiment, a ramping correction circuit is formed using a one-chip CPU (central processing unit) 62.
[0019]
The CPU 62 inputs an input terminal (Id terminal) for inputting an iris position instruction value (Id) output from the camera 10 via the changeover switch 12 and an input for inputting a selection signal (SI) from the auto / remote selection switch 50. A terminal (SI terminal), an input terminal (Z terminal) for inputting a zoom position detection signal (Z) output from the zoom group position detector 42, and a current iris position output from the iris position detector 48 are shown. An input terminal (Ip terminal) for inputting a signal (Ip), an output terminal (D / A terminal) for converting an iris control signal indicating an error between the indicated value Id and the current iris position Ip into an analog signal, and outputting the analog signal; And an output terminal (S0 terminal) for outputting a gain control signal (S0) for controlling the gain β of the iris amplifier 32.
[0020]
The memory of the CPU 62 stores the data of the ramping line (I = f (Z)) described in FIG. 5, and the CPU 62 detects the zoom position detected from the zoom group position detector 42 via the Z terminal. Based on the signal Z, the currently set focal length (zoom magnification) can be grasped, and the open F number of the lens corresponding to the zoom position (Z) can be obtained by referring to the data in the memory. Then, the iris position instruction value input from the camera 10 via the Id terminal of the CPU 62 is compared with the open F number to control the execution of the ramping correction operation.
[0021]
The auto / remote selection switch 50 provided in the camera 10 is interlocked with the changeover switch 12. When the auto / remote selection switch 50 is turned off, the changeover switch 12 is connected to the auto-side contact 12A, and the selection switch 50 is turned on. Then, the changeover switch 12 is connected to the remote-side contact 12B.
Next, an iris control method for the zoom lens configured as described above will be described.
[0022]
FIG. 2 shows a flow of iris control processing performed by the CPU 62 of FIG. First, the CPU 62 reads the iris position instruction value Id input from the camera 10 (step S110). Next, the zoom group position information Z from the zoom group position detector 42 is read, and an open aperture F number (I = f (Z)) at the zoom magnification indicated by the zoom group position Z is obtained from a function expression defining the ramping line. (Step S112).
[0023]
Subsequently, the CPU 62 reads the selection signal SI of the auto / remote selection switch 50 (step S114). Based on the selection signal SI, it is determined whether the auto mode or the remote mode is set (step S116). If NO is determined here, that is, if it is determined that the remote mode is set, the gain control signal S0 for increasing the gain β of the iris amplifier 32 is set in order to ensure high followability to the operation of the brightness adjustment knob 22. Output from the S0 pin. The gain β of the iris amplifier 32 is set to a higher value (H level) by the gain control signal S0 output from the S0 terminal (step S118).
[0024]
Thus, after setting the gain β of the iris amplifier 32, an iris control signal (Id + Ip) corresponding to the error between the iris position instruction value Id and the current iris position Ip is sent from the D / A output terminal of the CPU 62. It outputs to the iris amplifier 32 (step S128).
The control signal output from the D / A output terminal is amplified by the iris amplifier 32 and applied to the motor 36. The rotational driving force of the motor 36 is transmitted to the diaphragm 38 by power transmission means (not shown), so that the diaphragm 38 is driven to expand and contract. The diaphragm position of the diaphragm 38 is detected by a diaphragm position detector 48, and the detection result is notified to the CPU 62.
[0025]
On the other hand, if the determination in step S116 is YES, that is, if it is determined that the auto mode is set, then whether or not the iris position instruction value Id is larger than the open aperture I obtained in step S112 is determined. It discriminate | determines (step S120). When Id > I (NO determination), the gain control signal S0 for lowering the gain β of the iris amplifier 32 of the zoom lens 60 is output from the S0 terminal in consideration of the gain of the amplifier 26 in the camera 10. (Step S122). The gain β of the iris amplifier 32 is set to a lower value (L level) by the gain control signal S0 output from the S0 terminal.
[0026]
In the determination of step S120, when Id ≦ I (in the case of YES determination), the ramping correction is necessary during the auto mode. In this case, in order to improve the followability of the position control of the ramping correction operation, the iris is corrected. A gain control signal S0 for increasing the gain β of the amplifier 32 is output from the S0 terminal (step S124). The gain β of the iris amplifier 32 is set to a higher value (H level) by the gain control signal S0 output from the S0 terminal.
[0027]
Next, in order to restrict the diaphragm 38 from moving in the opening direction beyond the ramping line, the iris instruction value Id is set to the diaphragm value I equivalent to the opening F number obtained in step S112 (step S126). Then, the instruction value (in this case, the aperture value I set in step S126) and the error (Id + Ip) between the current position Ip are output from the D / A output terminal (step S128), and the process returns to step S110.
[0028]
As described above, when the ramping correction is performed in the auto iris mode, the gain β of the iris amplifier 32 is set high, so that accurate position control can be performed during the ramping operation, and the open aperture I = f (Z ) Can be narrowed down with high accuracy so as to match.
[0029]
【The invention's effect】
As described above, according to the iris control method and zoom lens of the zoom lens according to the present invention, during the auto iris mode, in the normal auto operation range, the gain of the iris amplifier is set to be small and the auto operation is normally performed. Even in the auto iris mode, the gain of the iris amplifier is set high in the range of the ramping correction operation, so it is possible to control the aperture position of the ramping correction operation with high accuracy and improve the accuracy of the ramping correction. Can be improved.
[Brief description of the drawings]
FIG. 1 is a block circuit diagram showing the configuration of a zoom lens for a television camera and a camera according to an embodiment of the present invention. FIG. 2 is a flowchart showing a flow of iris control processing performed by a CPU of the zoom lens shown in FIG. FIG. 3 is a graph showing an example of a change in the open F number of a lens with respect to a change in zoom magnification of a general zoom lens. FIG. 4 is a graph used for explaining a general ramping correction operation. FIG. 6 is a block circuit diagram showing a configuration of a general auto iris system. FIG. 7 is a block circuit diagram showing a configuration of a ramping correction circuit mounted on a conventional television lens. [Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Camera 12 ... Changeover switch 14 ... Brightness signal terminal 16 ... Signal processing part 22 ... Brightness adjustment knob (operation part)
32 ... Iris amplifier 36 ... Iris driving motor 38 ... Aperture 42 ... Zoom group position detector 48 ... Iris position detector 50 ... Auto / remote selection switch 60 ... Zoom lens 62 ... Central processing unit (CPU)

Claims (4)

It has an auto iris mode that automatically controls the aperture to an optimal value appropriately based on a signal indicating the brightness of the screen, and when the indicated value indicating the iris position is smaller than the open F number of the lens, the aperture is set to its open F number. In a zoom lens with a ramping correction function that narrows down to approximately the same value as
In the auto iris mode, when the instruction value indicating the iris position is larger than the open F number of the lens and the normal auto iris operation is executed, the gain of the iris amplifier that amplifies the iris control signal is set to the first gain value. On the other hand, when the indicated value is smaller than the open F number of the lens and a ramping correction operation is executed, the gain of the iris amplifier is set to a second gain value higher than the first gain value. An iris control method for a zoom lens. Auto iris mode that automatically controls the aperture to an optimal value based on a signal that indicates the brightness of the screen and remote iris mode that operates the iris according to manual operation of the operation unit are selectable, and the iris position is indicated In a zoom lens having a ramping correction function for narrowing the aperture to a value substantially equal to the open F number when the indicated value is smaller than the open F number of the lens,
In the auto iris mode, the indicated value that indicates the iris position is larger than the open F number of the lens, and when performing normal auto iris operation, the gain of the iris amplifier that amplifies the iris control signal is set higher than in the remote iris mode. In the case where the indicated value is smaller than the open F number of the lens and the ramping correction operation is executed, the gain of the iris amplifier is set to be equal to that in the remote iris mode. An iris control method for a zoom lens, wherein the second gain value is set higher than the first gain value. It has an auto iris mode that automatically controls the aperture to an optimal value appropriately based on a signal indicating the brightness of the screen, and when the indicated value indicating the iris position is smaller than the open F number of the lens, the aperture is set to its open F number. In a zoom lens with a ramping correction function that narrows down to approximately the same value as
An instruction value input unit to which a signal corresponding to an instruction value indicating an iris position is input;
An iris position detecting means for detecting an iris position indicating the current aperture value;
A control signal output unit that outputs a control signal for controlling the iris driving unit based on the instruction value input from the instruction value input unit and the iris position detected by the iris position detecting unit;
An iris amplifier that amplifies the control signal generated from the control signal output unit and adds the amplified signal to the iris driving means
Zoom position detecting means for detecting a zoom position indicating the current zoom magnification;
A data storage unit storing ramping line data indicating a change in the open F number of the lens with respect to a change in zoom magnification;
With reference to the data in the data storage unit, an open F number of the lens at the zoom position detected by the zoom position detecting unit is obtained, and the instruction value input from the instruction value input unit is compared with the open F number. Computing means;
During the auto iris mode, the instruction value input from the instruction value input unit is larger than the open F number of the lens obtained by the calculation means, and when performing a normal auto iris operation, the gain of the iris amplifier is set to the first value. When the instruction value input from the instruction value input unit is smaller than the open F number of the lens obtained by the calculation means and the ramping correction operation is executed, the gain of the iris amplifier is set to the gain value. A gain control means for setting a second gain value higher than the first gain value;
A zoom lens comprising: 4. The zoom lens according to claim 3, wherein the control signal output means, the calculation means, and the gain control means are constituted by a one-chip CPU.

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