JPH0572598A - Light quantity adjusting device - Google Patents

Abstract

PURPOSE:To provide a light quantity adjusting device which can obtain a proper light quantity based on data from a camera main body. CONSTITUTION:This camera is provided with a filter holding member 10 holding a filter 9 whose transmissivity is consecutively changed is rotatably provided in a lens barrel so that the filter 9 may be moved on an optical axis; and a driving source 12 which changes the transmissivity of the filter 9 on the optical axis by driving and rotating the filter holding member 10 so that the proper light quantity may be obtained according to information from the camera main body in which the lens barrel is assembled. In the case of attaining a photographing state by turning on the power source of the camera main body, the filter holding member 10 is driven and rotated so as to perform light quantity adjusting actions.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light amount adjusting device for automatically adjusting a light amount in a interchangeable lens for a video camera, for example, by moving a filter whose transmittance changes continuously on the optical axis by a driving source. It is a thing.

[0002]

2. Description of the Related Art FIG. 9 is a vertical sectional view showing a lens barrel of a conventional interchangeable lens for a video camera. In FIG. 8, 1 is a mount to be attached to the camera body (not shown), 2 is a fixing member to which the mount 1 is attached with screws 17,
Reference numeral 3 designates a lens barrel having a threaded portion 3a on the outer periphery of the front end and threaded portion 3b on the outer periphery of the rear end which is screwed with the screw portion 2a of the fixing member 2; A distance ring screwed together, 5 is a light member, 7 is a lens group held by the lens barrel 3, 8 is a lens group held by the fixing member 2, 14 is a substrate provided in the fixing member 2, and 14a and 14b are The control circuit is attached to the board 14 and communicates with the camera body.

By attaching the lens barrel having the above structure to the camera body, the lens barrel and the camera body are electrically connected to each other through the contacts 1a provided on the mount 1, and data communication can be performed between them. You can

As a result, the camera body discriminates the lens barrel based on the data from the attached lens barrel to operate correctly, and the lens barrel is driven from the camera body based on the data and is not shown in the drive source. It is possible to perform a focusing operation by rotating the distance ring 4 with.

In the lens barrel as described above, it is difficult to adjust the light quantity due to the change in area, and therefore, the light quantity adjusting filter as shown in FIG. 9 (usually called an ND filter).
The ring 30 holding 30a is screwed to the screw portion 4a on the inner peripheral surface of the front end of the distance ring 4 to adjust the light amount.

[0006]

However, in the above-described conventional example, it is very difficult in operation to selectively replace the filter 30a having an appropriate transmittance while the video camera is shooting, and therefore the replacement is not recommended. There is a risk that it will be taken and the shooting opportunity will be lost.

FIG. 10 is a vertical sectional view showing another conventional lens barrel. In FIG. 10, reference numeral 40 denotes a holding frame of the light quantity adjusting filter 40a. The holding frame 40 is inserted through the hole 2b formed in the upper surface of the fixing member 2 to remove the filter 40
a is located on the optical axis, and the filter 40a
Can be replaced easily and quickly. However, it is necessary to prepare a large number of filters, and it is very difficult to decide which filter to use.

Further, when the filters are exchanged during photographing, there is a problem that flicker and brightness change (flicker) occur on the screen, which is very unsightly.

It is an object of the present invention to provide a light quantity adjusting device capable of changing the transmittance of a filter on the basis of data from a camera body to obtain an appropriate light quantity.

[0010]

The present invention is a light quantity adjusting device characterized by the following configurations. (1) A filter holding member that holds a filter whose transmittance changes continuously is rotatably provided inside the lens barrel so that the filter moves on the optical axis, and information from the camera body with this lens barrel assembled. And a drive source for changing the transmittance of the filter on the optical axis so as to obtain an appropriate amount of light by rotationally driving the filter holding member, and when the camera body is powered on and is in a shooting state. By rotating the filter holding member to perform a light amount adjusting operation, an appropriate light amount can be obtained. (2) Since the filter whose transmittance changes logarithmically is provided, it can be applied to a camera of a system that logarithmically adjusts the light quantity, and the light quantity can be adjusted with good controllability.

[0011]

Embodiments of the present invention will now be described with reference to the drawings. 1 to 3 are drawings that best show the features of the present invention. FIG. 1 is a sectional view of the lens barrel of the present invention, and FIG.
FIG. 3 is a cross-sectional view taken along line AA of FIG. 3, and FIG. 3 is a schematic view showing a data communication system between the lens barrel 19 and the camera body 20.
1 to 3, 1 is a mount, 2 is a fixing member,
Reference numeral 3 is a lens barrel, 4 is a distance ring, 5 is a light member, 6 is a focusing lens, and 7 and 8 are lens groups, which are the same as the conventional lens barrel shown in FIG. The same reference numerals are given and duplicate description is omitted.

Reference numeral 10 denotes a ring-shaped filter holding member. This filter holding member 10 has a gear portion 10a on the outer periphery thereof and has a filter 9 (generally ND) whose transmittance changes continuously.
A filter) is held, and the filter 9 is rotatably attached to the fixed member 2 by a shaft 15 so that the rotation locus of the filter 9 coincides with the optical axis. Reference numeral 11 denotes the contact pieces 11 having the patterns 16a and 16b attached to the outer peripheral portion of the filter holding member 10.
Brushes detected by a and 11b, 12 is gears 12a and 13
It is a motor that drives the filter holding member 10 via.

Reference numeral 14 denotes a substrate attached to the fixing member 2 with a screw 27. The substrate 14 holds the brush 11 and the motor 12 on the back surface, and a signal from the camera body 20 and a signal from the brush 11 are provided on the front surface. Control circuits 14a and 14b for processing the pattern detection signal and controlling the drive of the motor 12
Is provided.

When the lens barrel 19 having the above-described structure is assembled to the camera body 20 by the mount 1, both are attached to the contact 1a on the lens barrel 19 side and the contact 20 on the camera body 20 side.
It is electrically connected by a. When the power switch 17 is operated in this connection state to enter the photographing state, the camera body 20 and the lens barrel 19 start mutual data communication.

The control circuit 28 on the camera body 20 side
Determines whether the exposure is proper according to the amount of light collected by the CCD 27 through the lens barrel 19, and sends a control command to the control circuit 14a in the lens barrel 19 when the exposure is inappropriate. For this reason,
The control circuit 14a determines in which direction the motor 12 should be rotated based on the input control command, supplies a drive signal to the motor 12, and at the same time, based on the detection signals of the patterns 16a and 16b, the filter position of the proper transmittance. Stop on the optical axis. As a result, an appropriate amount of light can be obtained on the camera body 20 side.

A specific method of producing the filter 9 whose transmittance changes continuously will be described below. FIG. 4 is a perspective view showing a processed state. In FIG. 4, reference numeral 21 denotes a jig whose end face 21a changes in thickness in the longitudinal direction L with the rotation angle θ, and the filter element 9a is attached to the end face 2 of the jig 21.
After adhering to 1a, the end surface of this filter element 9a is polished to be a flat surface.

FIG. 5 is a diagram showing the rotation angle θ on the horizontal axis and the thickness on the vertical axis. As shown in FIG. 4, the polished filter element 9a and the similar-processed completely transmissive glass element are shown. 9b is shown. By superposing and adhering the filter element 9a and the glass element 9b on each other as shown in FIG. 6, it is possible to form the filter 9 in which the transmittance continuously changes according to the rotation angle θ without changing the optical path length. it can.

FIG. 7 is an explanatory view of another method for producing a filter. In FIG. 7, 22 is a circular plate which rotates around an axis (not shown) passing through a central hole 23. In addition, a large number of large and small hole portions 22a and 22b are provided by sequentially changing the hole diameter in the rotation direction.

By replacing the disc 22 with the filter 9 shown in FIG. 1, continuous light quantity adjustment can be performed.
The number of holes may be changed without changing the hole diameter.

Further, in the adjustment of the light amount of the optical system in the video camera and the still camera, there are many controls such that the changing rate becomes a constant ratio, and it is generally called an equal-interval stop.
In such a system that performs logarithmic light amount adjustment, the above-described light amount adjusting mechanism using the filter 9 or the disk 22 has poor matching in terms of control.

However, by making the above-mentioned filter 9 so that the rotation direction and the change in transmittance change logarithmically,
The light amount of the mirror lens can be adjusted with good controllability.

Therefore, as the jig 21 shown in FIG.
By using a jig whose change amount t of the thickness of the end face 21a changes logarithmically with respect to the rotation angle θ, the filter element 9a-1 as shown in FIG. 8 and the thickness change antilogarithmically. The glass element 9b-1 is prepared, and the filter 9 is prepared by stacking and adhering the glass element 9b-1.

Further, it is easily conceivable to change the number or the diameter of the large and small holes 22a and 22b formed in the disk 22 shown in FIG. 7 logarithmically.

As the drive source of the filter holding member 10, a DC motor 12, a stepping motor, a motor using a vibration wave, or a plunger may be used.

Further, the position detecting means of the filter holding member 10 is a pattern and a brush in the above embodiment, but may be an optical type, a magnetic type, an electrostatic type or the like. In this case, it is easily conceivable to increase the number of bits for position detection to detect the absolute position of the filter holding member 10 or to generate a pulse signal according to the rotation of the filter holding member 10.

[0026]

As described above, according to the present invention,
A filter holding member that holds a filter whose transmittance changes continuously is provided rotatably in the lens barrel so that the filter is located on the optical axis, and based on information from the camera body with this lens barrel assembled. Rotation drive the filter holding member,
Since the filter position that provides an appropriate amount of light is located on the optical axis, it is easy to automatically set the appropriate exposure. Further, since a filter whose transmittance changes logarithmically is used, there is an effect that it can be applied to a camera of a system that logarithmically adjusts the light amount to perform the light amount adjustment with good controllability.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an embodiment of the present invention.

FIG. 2 is a cross-sectional view taken along the line AA of FIG.

FIG. 3 is a schematic diagram showing a data communication system between a lens barrel and a camera body.

FIG. 4 is a perspective view of a filter element and a jig for explaining a filter manufacturing method.

FIG. 5 is a cross-sectional view of the filter element and the glass element in the process of being formed.

FIG. 6 is a cross-sectional view of the filter after being created.

FIG. 7 is a front view of a disc for explaining another method for producing a filter.

FIG. 8 is a transverse cross-sectional view of a filter element and a glass element in the process of preparation for explaining another method of manufacturing a filter.

FIG. 9 is a vertical cross-sectional view of a lens barrel including a conventional light amount adjusting device.

FIG. 10 is a vertical cross-sectional view of a lens barrel including another conventional light amount adjusting device.

[Explanation of reference numerals] 3 lens barrel 9 filter 10 filter holding member 12 motor (driving source) 19 lens barrel 20 camera body

Claims (2)

[Claims] 1. A filter holding member, which holds a filter whose transmittance changes continuously, is rotatably provided in a lens barrel so that the filter moves on the optical axis, and from a camera body to which this lens barrel is assembled. Drive source for changing the transmittance of the filter on the optical axis so that an appropriate amount of light can be obtained by rotationally driving the filter holding member according to the information of 1. In this case, the filter holding member is rotationally driven to perform a light amount adjusting operation. 2. The light amount adjusting device according to claim 1, further comprising a filter whose transmittance changes logarithmically.