JPH05134286A - Variable apex angle prism device - Google Patents

Abstract

PURPOSE:To decrease the occurrence of flare and ghost, to correct image blur, and to maintain good optical performance by providing a reflection preventing film on at least one surface out of the surfaces contacting to air on two optical members. CONSTITUTION:Transparent liquid having a specified refractive index or a transparent substance having viscosity is sealed in a space formed by transparent glass boards 1 and 2 and an elastic member 3 such as rubber. At least one of the glass boards 1 and 2 can respectively turn by energizing force from outside. For example, the glass board 1 turns while making a point 1a or the point 1b a rotational shaft, so that the variable prism having an optional prism apex angle is formed by the glass boards 1 and 2. The reflection preventing film (coating film) having the refractive index in accordance with the refractive indexes of the glass boards 1 and 2 is provided on the surfaces 1F and 2F of the glass boards 1 and 2 on air side. Thus, reflectance on a boundary surface with the air is made to small.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable apex angle prism device, and more particularly, to an image forming apparatus that can change the traveling direction of a passing light beam used in a vibration proof optical system such as a video camera and a still camera, or other optical devices. The present invention relates to a variable apex angle prism device capable of correcting blur.

[0002]

2. Description of the Related Art In recent years, the automation of photographing by camera devices such as still cameras and video cameras has progressed, and various functions such as automatic exposure adjusting means and automatic focus adjusting means have been put to practical use.

As one of these automation functions, a blur correction means for reducing harmful blur of a screen (so-called image blur) caused by various causes has been devised and put into practical use.

Particularly in a camera device such as a video camera, it is general to use a zoom lens as a photographing lens used, and the zoom ratio thereof tends to increase year by year.

On the other hand, the miniaturization of camera devices is also remarkable,
Against the backdrop of the downsizing of the image pickup screen size, the development of high-density mounting technology, and the development of a small recorder / mechanical chassis, even small models capable of shooting with one hand have appeared.

However, when using a small video camera equipped with such a zoom lens, harmful blurring of the screen occurs due to camera shake of the photographer, and in order to eliminate this blurring and obtain a stable screen. In addition, various shake prevention means have been proposed. If you use these shake prevention measures,
Not only the harmful blurring of the screen due to such camera shake,
This has a great effect even in a situation where harmful camera shake cannot be eliminated even when a tripod is used when photographing from a ship or an automobile.

The shake prevention means has at least a shake detection means for detecting a shake and a shake correction means for making a correction so that the shake does not occur on the screen according to the detected shake information.

As the shake detecting means, for example, an angular accelerometer, an angular velocity meter, an angular displacement meter, etc. are known. As the blur correction means, a method using a variable apex angle prism or a video camera configured to cut out an area to be actually used as a screen from the obtained imaging screen information,
There is known a method of sequentially changing the cutout position to a position where blurring is corrected.

As the blur correction means, a method in which the blur is removed at the stage of the image formed on the image pickup device by using a variable apex angle prism or some other optical means as in the former is used here. The correction method is called, and the latter method of electronically processing the image information including the blur to remove the blur is called the electronic correction means.

Generally, the optical correction means is capable of correcting a blur within an angle defined as a camera blur angle regardless of the focal length of the taking lens. Therefore, even if the telephoto side focal length of the zoom lens is long, it is possible to have the blur removal performance that is practically no problem. However, it has a drawback that the entire device becomes large.

On the other hand, the electronic correction means has a constant correction rate for the vertical dimension of the screen, for example. Therefore, as the telephoto side focal length of the zoom lens becomes longer, the blur removal performance deteriorates.
In general, the electronic type is often advantageous for miniaturization.

Next, a blur prevention means using a variable apex angle prism will be described.

FIG. 4A is an explanatory view for explaining the relationship between the focal length of the photographing lens and the camera shake angle with the subject position on the screen. In the figure, 13 is the optical axis of the photographing lens when the camera CA is at the position shown by the solid line 12,
This means that the face of the person 11 who is the subject is almost centered. From this state, a degree, camera CA due to camera shake
Is rotated. The position of the camera CA at this time is the solid line 1
The position is indicated by 4, and its optical axis is indicated by 15.

4 (B) and 4 (C), position 12 and position 14 are shown.
6B shows the screen position of the camera, FIG. 7B shows the state of the zoom lens at the tele end, and FIG. 7C shows the state at the wide end. Reference numeral 16 denotes a subject within the screen, 17 and 19 denote the screen at the position 12, and 18 and 20 denote the screen at the position 14.

As is clear from FIG. 4, even if the camera shake is the same a degree, naturally, the longer the focal length of the taking lens, the greater the harm as the shake on the screen. Therefore, it can be said that the optical means using the variable apex angle prism is an effective blur correction means especially in the blur removing means combined with a photographing lens having a long focal length at the telephoto end.

FIG. 5 shows the structure of the variable apex angle prism. In the figure, 21 and 23 are transparent glass plates, and 27 is a bellows part made of a material such as polyethylene. A transparent liquid 22 made of, for example, silicon oil is enclosed in the inside surrounded by these glass plates and the bellows.

In FIG. 5B, two glass plates 21 and 23 are used.
Are parallel to each other, and in this case, the incident angle and the outgoing angle of the light ray 25 on the variable apex angle prism are equal.

On the other hand, when there is an angle as shown in FIGS. 5A and 5C, the rays are bent at a certain angle as shown by rays 24 and 26, respectively. Therefore, when the camera is tilted due to camera shake or the like, the angle (apex angle) of the variable apex angle prism provided in front of the taking lens is controlled so that the spectral line corresponding to that angle bends. Have been removed.

FIG. 6 shows this state, which is shown in FIG.
Assuming that the variable apex prism is in a parallel state and the optical axis captures the head of the subject, the variable apex prism is driven as shown in the figure for a degree of a blur as shown in FIG. By bending the light beam, the optical axis of the image remains the same and you can continue to capture the subject's head.

FIG. 7 is a schematic view showing an example of the actual construction of a variable vertical angle prism unit including the variable vertical angle prism, an actuator section for driving the variable vertical angle prism, and a vertical angle sensor for detecting an angular state. is there. Since actual blurring appears in all directions, the front glass surface and the rear glass surface of the variable apex angle prism are configured so as to be rotatable about the rotation axes in directions shifted by 90 degrees. Here, the subscripts a and b indicate the respective components in these two rotation directions, but those having the same number have exactly the same function. Further, some parts on the b side are not shown.

Reference numeral 41 denotes a main body of the variable apex angle prism, which is composed of glass plates 21 and 23, a bellows portion 27 and an internal liquid 22.
The glass plate is integrally attached to the holding frame 28 using an adhesive or the like. The holding frame 28 constitutes a rotary shaft 33 with a fixed component (not shown), and is rotatable around this shaft.

The rotating shaft 33a and the rotating shaft 33b are different in the direction of 90 degrees. A coil 35 is integrally provided on the holding frame 28, while a fixed portion (not shown) is
A magnet 36 and yokes 37 and 38 are provided.

Therefore, when a current is passed through the coil 35, the glass plate of the variable apex angle prism is rotated around the shaft 33. There is a slit 29 at the tip of the arm portion 30 that extends integrally from the holding frame 28, and the iRED provided at the fixed portion is provided.
An apex angle sensor is configured between the light emitting element 31 such as an element and the light receiving element 42 such as a PSD.

FIG. 8 is a block diagram showing the configuration of an image stabilizing lens system in which the shake preventing means having the variable apex angle prism as a correcting means is combined with a photographing lens.

In the drawing, 41 is a variable apex angle prism, 4
Reference numerals 3 and 44 denote a detection sensor for amplifying the output of the apex angle sensor, and reference numerals 53 and 54 denote an output of the apex angle sensor.
The reference numerals 46, 47 are shake detecting means. In the micro computer 45, the angle state detected by the apex angle sensors 43 and 44 and the optimum angle state for removing the blur according to the detection results of the blur detecting means 46 and 47 are set to the variable apex angle prism. To control the angular state, the current applied to the actuators 48, 49 is determined.

The main element is composed of two blocks because it is assumed that the glass plates are controlled independently of each other in two directions which are 90 degrees apart.

[0027]

In the conventional variable apex angle prism device, two transparent glass plates forming the variable apex angle prism may be substantially parallel to each other when the device is attached to the photographing system.

For this reason, the light passing through the variable apex angle prism is reflected by the surfaces of the two glass plates and causes ghost and flare depending on its intensity. Therefore, the glass plate needs a coating for antireflection. Met. However, when coating both surfaces of a glass plate, one of them faces a liquid having a high refractive index, so that there are problems such as selection of a film used for coating and reactivity between the internal liquid and the film.

According to the present invention, by appropriately setting the coating film to be applied to the glass plate, it is possible to effectively prevent ghost and flare which are reflected by the glass plate and occur, and to maintain good optical performance as well as correction of image blur. It is an object of the present invention to provide a variable apex angle prism device capable of

[0030]

In the variable apex angle prism device of the present invention, an optically transparent substance is enclosed in a space formed by sandwiching two transparent optical members, and is biased by an external force. In a variable apex angle prism device configured to rotate at least one of the two optical members to form an arbitrary prism apex angle and to have a prism action, in the variable optical apex prism device of the two optical members, contact is made with air. The present invention is characterized in that an antireflection film is provided on at least one of the existing surfaces.

[0031]

Embodiment 1 FIG. 1 is a sectional view of the essential portions of Embodiment 1 of the present invention.

In the figure, reference numerals 1 and 2 denote optical members, each of which is a glass plate (transparent plate) made of a transparent plane parallel plate. 3 is an elastic member such as a stretchable rubber, which is attached around the glass plates 1 and 2 to seal the internal space.

The glass plates 1 and 2 are arranged to face each other at an interval of several mm. Reference numeral 4 denotes a transparent liquid or viscous substance having a predetermined refractive index, which is enclosed in a space formed by the glass plates 1 and 2 and the elastic member 3.

Surfaces 1F and 2 of the glass plates 1 and 2 in contact with air
An antireflection film made of a substance described later is applied to F.

At least one of the glass plates 1 and 2 can be independently rotated by an urging force from the outside. For example, the glass plate 1 is rotatable about a point 1a or a point 1b as a rotation axis. As a result, the two glass plates 1 and 2 form a variable prism having an arbitrary prism apex angle.

In this embodiment, when the variable apex angle prism device having such a structure is attached to a part of the photographing system and an image is shaken, the prism apex angle is changed according to the amount of shake, and the passing light flux is given a predetermined amount. It is deflected to obtain the anti-vibration effect.

In general, when the variable apex angle prism device is provided in a part of the photographing system to perform the image stabilizing action, the rotation angle of the glass plate is small and the prism apex angle is often small. That is, the two glass plates 1 and 2 are often substantially parallel to each other.

Therefore, when a high-luminance object is imaged, the light flux reflected by the surfaces of the two glass plates 1 and 2 may reach the imaging surface and cause flare or ghost. It was Moreover, since the prism apex angle of the variable apex angle prism changes according to the blur of the image, flare and ghost also change accordingly, and the image may be very unsightly.

Therefore, in this embodiment, an antireflection film (coating film) having a refractive index according to the refractive index of the glass plates 1 and 2 is applied to the air side surfaces 1F and 2F of the glass plates 1 and 2 shown in FIG. ing. An antireflection film having an appropriate refractive index may be similarly applied to the surface on the liquid 4 side.

However, the difference between the refractive index of the liquid 4 and the refractive index of the glass plates 1 and 2 is generally small, and the reflectance of the interface is small as described later. Therefore, in this embodiment, the antireflection film is not provided on the surface of the glass plates 1 and 2 on the liquid 4 side.

Generally, as shown in FIG. 2, when the refractive index of the material of the glass plate 1 is n _g and the refractive index of air is n _o , the refractive index R _{o on} the surface of the glass plate 1 is

[0042]

[Equation 1] Becomes On the other hand, as shown in FIG. 3, the reflectance R when the antireflection film 31 having the refractive index n ₁ is applied to the glass plate 1 is

[0043]

[Equation 2] Becomes

In this embodiment, as shown in a numerical example described later, an antireflection film having an appropriate refractive index n ₁ with respect to the refractive index _ng of the material of the glass plate 1 is applied to form a boundary surface with air. The reflectance of and is reduced, and the occurrence of flare and ghost when attached to the shooting system is reduced.

Next, the configuration of the variable apex angle prism of this embodiment,
A numerical example of the antireflection film and the reflectance of the boundary surface when the antireflection film is used will be shown.

(Numerical Example 1)

[0047]

[Table 1]

[0048]

[Table 2] (Numerical example 2)

[0049]

[Table 3]

[0050]

[Table 4] The reflectance R _o of the glass plate when the antireflection film is not applied
Is about 4.2% to 3.9%. By providing the antireflection film Mgf ₂ as shown in Numerical Examples 1 and 2, the reflectance is 4.2% to 3.9% to 1.
It is greatly reduced to about 5% to 1.3%.

[0051]

According to the present invention, the anti-reflection film is formed on the surface of the optical member constituting the variable apex angle prism that comes into contact with air as described above. It is possible to achieve a variable apex angle prism device that can effectively reduce flare and ghosts and maintain good optical performance with image blur correction.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part of a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of the reflectance of the surface of the glass plate.

FIG. 3 is an explanatory diagram of reflectance when an antireflection film is applied to a glass plate.

FIG. 4 is an explanatory diagram showing a relationship between camera shake and image shake.

FIG. 5 is an explanatory diagram showing a relationship between a prism apex angle and a passing light beam.

FIG. 6 is a schematic view when a variable apex angle prism is arranged in front of the camera.

FIG. 7 is a schematic view of a main part of an actuator that drives a variable apex angle prism.

FIG. 8 is a block diagram of a vibration isolation system using a variable apex angle prism device.

[Explanation of symbols]

 1, 2 glass plate 3 elastic member 4 liquid 1a, 1b rotating shaft

Claims (1)

[Claims] 1. An optically transparent substance is enclosed in a space formed by sandwiching it between two transparent optical members, and at least one of the two optical members is rotated by a biasing force from the outside. A variable apex angle prism device configured to form an arbitrary prism apex angle to have a prism action,
A variable apex angle prism device, wherein an antireflection film is provided on at least one surface of the two optical members that is in contact with air.