JP3154334B2 - TV camera focus adjustment device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focus adjusting device for a television camera, and more particularly to a focus adjusting device for a television camera which focuses a photographing lens using a focus position demand of the television camera.

[0002]

2. Description of the Related Art When a focus is adjusted in a television camera of this type, a photographer rotates a focus knob of a focus position demand 1 while looking into a finder 2 as shown in FIG. That is, the focus position demand 1 outputs a voltage signal proportional to the amount of rotation of the focus knob to the focus mechanism, and the focus mechanism moves the front lens (focus lens) of the photographing lens of the television camera according to the input voltage signal.

Accordingly, as shown in FIG. 7, the front lens moves from the closest distance to the lens position corresponding to infinity in proportion to the rotation amount [%] of the focus knob. Incidentally, the rotation amount of the focus knob is often 1 to 3 rotations, and 2 rotations is a recent standard. In FIG. 6, reference numeral 3 denotes a zoom rate demand.

[0004]

By the way, if the rotation amount of the focus knob is small, the operation from the close distance to infinity can be performed quickly, but there is a problem that the sensitivity of focusing is high and it is difficult to use, and the rotation amount is large. Then, a problem opposite to the above case occurs. The present invention has been made in view of such circumstances, and it is possible to smoothly perform a focusing operation from a close distance to infinity, and to reduce a focusing sensitivity in a predetermined range where focusing is to be performed as necessary. It is an object of the present invention to provide a focus adjustment device for a television camera which can perform the following.

[0005]

In order to achieve the above object, the present invention provides a focus position demand for outputting an electric signal proportional to a rotation angle of a focus knob, and a focus lens at a lens position proportional to the electric signal. In a focus adjustment device of a television camera having a focus mechanism that moves electrically, an electric signal is input from the focus position demand, and a position of a focus lens corresponding to the electric signal at the time of switching from a normal mode to a fine adjustment mode is determined. Within the predetermined lens movement range, the gain of the subsequently inputted electric signal is made smaller than in the normal mode, and outside the predetermined lens movement range, the gain of the subsequently inputted electric signal is made larger than in the normal mode. Variable sensitivity means and switching to normal mode Sometimes an electric signal from the focus position demand to the focus mechanism,
A mode changeover switch for outputting an electric signal from the sensitivity varying means to the focus mechanism when switching to the fine adjustment mode. According to another aspect of the present invention, there is provided a focus adjustment device for a television camera having a focus mechanism for electrically moving a focus lens based on an electric signal output from a focus position demand according to an operation amount of a focus knob. A mode changeover switch for changing the sensitivity of the focus position demand from a normal mode to a fine adjustment mode; and an electric signal corresponding to an operation amount of the focus knob when the mode is changed over to the fine adjustment mode by the mode changeover switch. Means for varying the output sensitivity, wherein within a predetermined lens movement range including the position of the focus lens at the time of switching from the normal mode to the fine adjustment mode, an electric signal output in response to the operation of the focus knob thereafter Output sensitivity in normal mode A sensitivity variable means for making the output sensitivity of an electric signal output in response to the operation of the focus knob larger than the output sensitivity in the normal mode while the output sensitivity is smaller than the output sensitivity of the focus lens. , Is provided.

[0006]

According to the present invention, the normal mode and the fine adjustment mode can be appropriately switched by the mode switch. That is, when the mode is switched to the normal mode,
An electric signal from the focus position demand is directly output to the focus mechanism, and the focus lens is moved electrically, as in the case of normal focus adjustment. Thus, the focusing operation from a close distance to infinity can be smoothly performed.

On the other hand, when the mode is switched to the fine adjustment mode,
The electric signal from the focus position demand is output to the focus mechanism via the sensitivity changing means. The sensitivity varying means captures an electric signal at the time of switching to the fine adjustment mode, reduces the gain of the subsequently input electric signal within a predetermined lens movement range of the focus lens corresponding to the electric signal, and Outside the lens movement range, the gain of the electric signal input thereafter is increased. Therefore, after performing the approximate focusing in the normal mode, by switching to the fine adjustment mode, the sensitivity of the focusing becomes low in a predetermined lens moving range including the lens position of the focused focus lens, and the focusing is performed. It will be easier.

[0008]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing a preferred embodiment of a focus adjusting device for a television camera according to the present invention. First, the present invention will be described in principle with reference to the graphs of FIGS. The present invention has two types of focus adjustment modes, a normal mode and a fine adjustment mode, as described later.

That is, the normal mode is a mode in which an electric signal from the focus position demand is directly output to the focus mechanism. In this normal mode, if the input from the focus position demand is x and the output to the focus mechanism is y, the input / output relationship is y = x as shown in FIG.

On the other hand, in the fine adjustment mode, as shown in FIG. 4 (B), the input / output relationship according to the size of the input x is expressed as follows: y = ax (x <x ₁ ) (1) y = bx + p (x ₁ ≦ x ≦ x ₂ ) (2) y = ax + q (x ₂ <x) (3) (where b <1 <a, q <0 ≦ p).

That is, when the input x is within a predetermined range (x ₁ ≦ x ≦ x
₂ ), the gain becomes smaller and the sensitivity becomes lower than in the normal mode, and when the input x is outside the above range (x <x ₁ , x ₂ <x), the normal mode The gain is set to be larger than at the time. Here, the input x immediately before switching from the normal mode to the fine adjustment mode is x _m (= y _m ), and under the condition that the output y _m coincides with the center of the low sensitivity range as shown in FIG.
The case where the constants of the above equations are obtained will be described.

First, as shown in FIG.
Range x_Two-X₁X_wAnd Also, this x_wAnd expression
Variable or fixed b in (2) with a volume, switch, etc.
And set first. Therefore, b, x_w, Y_w,
x_max, Y_max(X_max= Y_max, Y _w= Bx_w) Is already
Is knowledge. Now, in order to satisfy the above condition, y_m= Y₁+ Y_w/ 2, y₁= Y_m-Y_w/ 2. Also, y_Two, X₁, X_TwoIs y_Two= Y₁+ Y_w x₁= Y₁/ Ax_Two= X₁+ X_w Becomes Also, a, p, and q are a = (y_max-Y_w) / (X_max-X_w) P = y₁-Bx₁ (∵y₁= Bx₁+ P) q = y_Two-Ax_Two (∵y_Two= Ax_Two+ Q).

As described above, the constants of the equations representing the three broken lines can be obtained. In addition, as described above, 3
When the constants of the linear expressions representing the polygonal lines are determined, the output y changes as shown in FIG. 4B at the time of mode switching. Next, a description will be given of a case where constants of respective linear expressions representing three broken lines are obtained under the condition that the output y does not change as shown in FIG. 5 when switching from the normal mode to the fine adjustment mode.

In order to satisfy the above condition, y = bx + p even when the mode is switched from the normal mode to the fine adjustment mode.
Must pass through (x _m , y _m ). Therefore, the _{y m = x m y m =} bx m + p, a p = x _m -bx _m. Also, since y = ax + q passes through the (x _w, y _w), a q = y _w -ax _w.

On the other hand, x ₁ and y ₁ are given by x ₁ = p / (ab) y ₁ = ap / (ab) from y ₁ = ax ₁ y ₁ = bx ₁ + p, and similarly x _2, y ₂ is, y from _{2 = bx 2 + p y 2} = ax 2 + q, the _{x 2 = (p-q)} / (a-b) y 2 = (ap-bq) / (a-b) .

FIG. 1 is a diagram showing one embodiment of a focus adjusting device for a television camera according to the present invention. This focus adjusting device includes a potentiometer 12 for a focus position demand, a sensitivity variable unit including operational amplifiers 21, 22, 23, 24 and 26, and a mode changeover switch 3.
0, a focus amplifier 34, a focus motor 35, and a front lens position detector 36.

The potentiometer 12 detects the rotation angle of the focus knob 11 of the focus position demand 10 as shown in FIG. 2, and outputs a voltage signal (x) proportional to the rotation angle via the buffer 14. Operational amplifier 2
An offset value (a value corresponding to q in equation (3)) is added to the positive input of 1, and the operational amplifier 21 inverts and amplifies the input voltage signal (x) with a gain a. An offset value (a value corresponding to p in equation (2)) is applied to the positive input of the operational amplifier 22 as described later, and the operational amplifier 22 inverts and amplifies the input voltage signal (x) with a gain b. 23 inverts and amplifies the input voltage signal (x) with a gain a.

On the other hand, the operational amplifier 24 receives a voltage signal from the potentiometer 12 in the normal mode (the movable contact 32C is connected to the contact 32A) and is switched to the fine adjustment mode (the movable contact 32C is switched from the contact 32A to 32B). A sample-and-hold circuit that holds the voltage signal when the voltage is increased, and amplifies the sample-and-hold circuit with an appropriate gain (a gain for obtaining a value corresponding to p in Expression (2)). As described above, p is a function of x _m (= y _m ).

The voltage signal corresponding to p from the operational amplifier 24 is passed through a limiter circuit 25 to the operational amplifier 2.
2 is applied to the positive input. Note that the limiter circuit 25 limits the upper and lower limits of the voltage signal corresponding to p. In the case of the calculation method in FIG. 5, the limiter circuit 25 is unnecessary. Then, one of the outputs of the operational amplifiers 21, 22, and 23 is applied to the operational amplifier 26 by the diodes D1 and D2, where the output is inverted and output.

The mode changeover switch 30 is disposed near the focus position demand 10 as shown in FIG. 2, and has a movable contact piece 31C,
32C is connected to the contacts 31A and 32A, and the movable contact pieces 31C and 32C are connected to the contacts 31B and 32B in the fine adjustment mode.
Connect to The voltage signal from potentiometer 12 or the voltage signal from operational amplifier 26 is applied to summing point 33. To the negative input of the addition point 33, a voltage signal indicating the front lens position is added from a front lens position detector 36 that detects the position of the front lens of the taking lens for performing the focus adjustment.
Reference numeral 3 outputs a difference signal between these signals to a focus motor 35 via a focus amplifier 34. Thus, the front lens of the photographing lens is moved to a position corresponding to the rotation angle of the focus knob 11, but is moved with different sensitivities in the normal mode and the fine adjustment mode.

In the above embodiment, the sensitivity variable section is constituted by the operational amplifier. However, the above-described calculation may be performed using a microcomputer. FIG. 3 is a flowchart showing a processing procedure when a microcomputer is used. First, the flag F is set to 1 (step 10).
0). This flag F is a flag for distinguishing whether or not to calculate a constant as described later.

Next, x, b, x_wEnter (Step 1
02) Then, it is determined whether or not the mode is the normal mode (step
104). In the case of the normal mode, set y = x
And set the flag F to 1 (steps 106 and 10).
8) Output y (step 110). Meanwhile, Norma
If the mode is not the mode (fine adjustment mode),
Proceeds to step 112, where it is determined whether the flag F is 1 or not.
You. When the flag F is 1, fine adjustment from normal mode
Immediately after switching to the adjustment mode,
Execute steps 14 to 118. That is, x is x_mRemembered as
And a, p, q, x₁, X _Two, Y₁, Y_TwoI calculated
The flag F is set to 0, and the routine proceeds to step 120. This
On the other hand, when the flag F is 0 in the fine adjustment mode,
Since the constant of each expression has already been calculated, step 1
The process proceeds from step 12 to step 120.

In steps 120 and 122, x input in step 102 is x <x ₁ , x ₁ ≦ x ≦
x ₂ determines whether or not the. That is, the process proceeds to step 124 in the case of x <x _1, Step 1 After calculating the y = ax
At step 10, the value y is output. If x ₁ ≦ x ≦ x ₂ , the process proceeds to step 126. After calculating y = bx + p, the value y is output at step 110. If x ₂ <x, the value 128 is output. After calculating y = ax + q, the value y is output at step 110.

[0024]

As described above, according to the focus adjusting device for a television camera of the present invention, the focusing operation from a close distance to an infinity can be smoothly performed.
If necessary, the sensitivity of focusing in a predetermined range to be focused can be reduced, thereby facilitating focusing.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of a focus adjustment device for a television camera according to the present invention.

FIG. 2 is a diagram showing an example of the arrangement of mode changeover switches in a focus position demand of a focus adjustment device for a television camera according to the present invention.

FIG. 3 is a flowchart illustrating a processing procedure when a microcomputer is used;

FIGS. 4A and 4B are graphs used to explain one calculation example applied to the present invention.

FIG. 5 is a graph used for explaining another calculation example applied to the present invention.

FIG. 6 is a schematic diagram of a television camera to which the present invention is applied.

FIG. 7 is a graph showing a relationship between a focus knob rotation amount and a front lens movement amount in a conventional focus adjustment device for a television camera.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Focus position demand 11 ... Focus knob 12 ... Potentiometer 21, 22, 23, 24, 26 ... Operational amplifier 25 ... Limiter circuit 30 ... Mode changeover switch 34 ... Focus amplifier 35 ... Focus motor 36 ... Front lens position detector

Claims (2)

(57) [Claims] 1. A focus adjustment device for a television camera, comprising: a focus position demand for outputting an electric signal proportional to a rotation angle of a focus knob; and a focus mechanism for electrically moving a focus lens to a lens position proportional to the electric signal. An electric signal is input from the focus position demand, and the position of the focus lens corresponding to the electric signal at the time of switching from the normal mode to the fine adjustment mode is determined.
As well as smaller than the normal mode the gain of the electrical signal to be input thereafter are within a predetermined lens movement range including, larger than the normal mode the gain of the electrical signal and in the predetermined lens movement range of input thereafter A mode in which an electric signal from the focus position demand is output to the focus mechanism when switching to the normal mode, and an electric signal from the sensitivity variable means is output to the focus mechanism when switching to the fine adjustment mode. A focus adjustment device for a television camera, comprising: a changeover switch. 2. A focus adjustment device for a television camera having a focus mechanism for electrically moving a focus lens based on an electric signal output from a focus position demand in accordance with an operation amount of a focus knob, the device comprising: A mode switch for switching the sensitivity of the position demand from the normal mode to the fine adjustment mode; and Therefore, within a predetermined lens movement range including the position of the focus lens at the time of switching from the normal mode to the fine adjustment mode,
Thereafter, the output sensitivity of the electric signal output in response to the operation of the focus knob is made smaller than the output sensitivity in the normal mode, while outside the predetermined lens movement range, the output is thereafter output in response to the operation of the focus knob. And a sensitivity varying means for increasing the output sensitivity of the electric signal to be higher than the output sensitivity in the normal mode.