JPH0815595A - Focus correcting mechanism - Google Patents

Abstract

PURPOSE:To provide a focus correcting mechanism whose structure is simple, whose cost is low and which is miniaturized as the focus correcting mechanism of an optical equipment, especially, the correction mechanism correcting out-of- focus caused by temperature change. CONSTITUTION:This mechanism is provided with a cylindrical lens barrel 10 constituted by attaching a photoreceiving body at one end, a cylindrical body 30 being a cylinder constituted by attaching a condensing lens 2 in a hollow hole and inserted to move and slide in an optical axis direction in the lens barrel 10, a bar 40 like a bar consisting of a material having the coefficient of thermal expansion larger than that of the lens barrel 10 and constituted by pivotally coupling its one end with one end of the lens barrel 10, and an arm 45 constituted by pivotally supporting and coupling one end with the other end of the bar 40, pivotally supporting and coupling other end with the cylindrical body 30, and pivotally supporting its specified middle spot so as to freely rock in the lens barrel 10. The bar 40 is expanded or contracted by the change of ambient temperature and the clindrical body 30 is moved in a direction where it comes close to the photoreceiving body or a direction where it goes away from the photoreceiving body by the lever action of the arm 45.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focus correction mechanism for an optical device, and more particularly to a correction mechanism for correcting a focus shift caused by a temperature change.

A lens system mounted on an optical device such as an infrared detector is constructed as shown in FIG. In the figure,
Reference numeral 1A denotes an infrared detection element formed by arranging one or more in parallel on the surface of a substrate made of sapphire or the like.

The infrared detection element 1A is Hg _1-X Cd _X Te
The crystal is formed on the surface of the substrate in a substantially rectangular shape, the central portion is the light receiving portion, metal films are formed on the surfaces on both sides of the light receiving portion as electrodes, and leads are led out from each electrode.

The infrared detector 1 has a cylindrical casing mounted on a base 4, an infrared detecting element 1A mounted in the casing so as to maintain a distance from the ceiling plate of the casing, and infrared detection. element
A cooling device (for example, a cooling device using a Peltier effect type cooling element) mounted on the back side of the substrate on which the infrared detection element 1A is formed so that 1A can be cooled to a predetermined low temperature (about 80K).
It consists of and.

Further, an infrared transmitting plate 3 made of Ge or the like is fitted into a hole provided directly above the infrared detecting element 1A on the ceiling plate of the housing, and infrared rays from the outside pass through the infrared transmitting plate 3. The light is advanced into the housing and focused on the light receiving surface of the infrared detection element 1A.

The heat on the outside of the housing is detected by the infrared detecting element 1A.
The inside of the housing is evacuated in order to prevent it from being transmitted to. In order to detect infrared rays emitted by an object on the infrared detection element 1A and detect the infrared rays with the infrared detector 1, the infrared detection element 1A has a cylindrical shape so as to coincide with the axis. The lens barrel 10 is attached to the base 4 of the infrared detector 1, the condenser lens 2 and the objective lens system (not shown) are mounted in the lens barrel 10, and infrared rays emitted from the object are collimated by the objective lens system. The parallel beam to the condenser lens 2
Therefore, the light is focused on the light receiving surface of the infrared detection element 1A.

The material of the condenser lens 2 and the objective lens system is, for example, Ge, which has a large transmittance for wavelengths in the infrared region, and is generally called an infrared lens. Now, when the temperature of the condenser lens 2 rises, the refractive index changes so as to increase and the focal length becomes shorter, and the focus shifts to point P ₁ shown in FIG. 4, for example.

Further, when the temperature decreases, the refractive index changes so as to decrease, and the focal length increases. On the other hand, the infrared detector described above is used in an environment where the ambient temperature changes in the range of −30 ° C. to + 60 ° C.

Therefore, when the ambient temperature changes, the focal length of the condenser lens 2 changes, and as a result, infrared rays do not converge on the light receiving surface of the infrared detecting element 1A. Therefore, a focus correction mechanism is required for the lens system used where the ambient temperature changes.

[0010]

2. Description of the Related Art FIG. 4 is a sectional view of a conventional example of an infrared detector having a focus correction mechanism. In the figure, 4A is a tube base with a flange mounted so as to intervene between the base 4 on which the infrared detector 1 is mounted and the lens barrel 10.

Reference numeral 5 denotes a cylindrical inner cylinder which is slidably inserted into the upper portion of the lens barrel 10 in the axial direction and has a large outer diameter cylindrical portion and a small outer diameter cylindrical portion. Reference numeral 6 denotes a flanged cylindrical rotation tube that is rotatably inserted into the lower portion of the lens barrel 10.

In the inner cylinder 5, the condenser lens 2 is inserted in the large outer diameter cylinder, and a male screw is threaded on the outer peripheral surface of the inner cylinder of the small outer diameter cylinder. The outer diameter dimension of the large outer diameter tube portion is slightly smaller than the inner diameter dimension of the lens barrel 10, and the pair of guide pins 7 projecting to the outer peripheral portion.
Is inserted into a guide hole 8 provided in the lens barrel 10 and long in the axial direction.

The rotary cylinder 6 has a disk-shaped flange at a substantially central position of the cylinder, and a gear 12 is screwed on the entire circumference of the flange, and the cylindrical portion above the flange is inside the lens barrel 10. A female screw to be screwed into the male screw of the inner cylinder 5 is threaded on the inner wall of the cylindrical portion.

The lower portion of the collar of the rotating cylinder 6 is a cylinder base.
A ball bearing is inserted between the inner wall of the barrel base 4A and the outer circumference of the barrel portion of the barrel base 4A so that the pivot barrel 6 is rotatable within the barrel base 4A and the lens barrel 10.

The end face of the flange provided on the lower opening side of the lens barrel 10 is a stepped end face having a step greater than the flange thickness of the rotating barrel 6. The lens barrel 10 is fixed to the barrel base 4A with bolts in a state where the outer end face of the barrel of the barrel 10 is in close contact with the end face of the collar of the barrel base 4A.

Reference numeral 15 denotes a gear 11 fixed to the tip of the drive shaft.
However, in the space formed by the step of the lens barrel 10, the gear 12 of the rotation barrel 6
It is a motor mounted on the side of the cylinder base 4A so as to mesh with.
When the motor 15 is driven, the rotary cylinder 6 rotates in the lens barrel 10 via the gears 11 and 12. When the rotary cylinder 6 rotates, a force acts to rotate the inner cylinder 5 connected to the rotary cylinder 6 via a female screw and a male screw. On the other hand, the inner cylinder 5 is constrained in the lens barrel 10 so as to be slidably movable in the axial direction.

Therefore, the rotary cylinder 6 slides in the axial direction without rotating. That is, the condenser lens 2 moves in the direction approaching the infrared detecting element 1A or in the direction separating from the infrared detecting element 1A.

Reference numeral 16 is, for example, a thermocouple type temperature sensor that measures the temperature of the condenser lens 2. Reference numeral 17 denotes a displacement detector mounted on the barrel 4A side so that the gear fixed to the tip of the drive shaft meshes with the gear 12 of the rotating barrel 6 in the space formed by the step of the lens barrel 10. .

The operation of the conventional focus correction mechanism having the above-mentioned structure will be described below. When the temperature sensor 16 detects the temperature of the condenser lens 2, the detected value is obtained by the controller (not shown). From the table that was previously input, the control unit
The displacement amount of the focal length of the condenser lens 2 corresponding to the temperature change is extracted, and the rotating cylinder 6 is rotated by the rotation angle corresponding to the displacement amount.
The motor 15 is rotated by a predetermined number of rotations such that the motor rotates.

The displacement detector 17 detects the rotation angle of the rotary cylinder 6, and the actual condenser lens 2 is detected from the rotation angle and the rotation direction.
The amount of movement and the direction of movement are detected, the detection information is converted into an electric signal and fed back to the control unit.

With such sequence control, when the ambient temperature changes and the temperature of the condenser lens 2 rises and the focal length becomes short, the condenser lens 2 is automatically moved to the infrared detecting element 1A side. , The focus of the condenser lens 2 is an infrared detection element
It is designed to almost match the light receiving surface of 1A.

When the temperature of the condenser lens 2 decreases and the focal length becomes longer, the condenser lens 2 is automatically moved in the direction away from the infrared detecting element 1A, and the focus of the condenser lens 2 is changed to the infrared detecting element 1A. The light-receiving surface of is almost aligned.

[0023]

By the way, the conventional focus correction mechanism includes a temperature sensor for detecting the temperature of the condenser lens, a motor for rotating the rotary cylinder, a displacement detector for detecting the movement amount of the condenser lens, and Since there is a control unit for controlling the driving of the motor, there are many costly components, which is expensive.

Further, there is a fear that the size may be increased due to the large number of parts. The present invention was created in view of the above points, and an object thereof is to provide a focus correction mechanism having a simple structure, low cost, and a small size.

[0025]

In order to achieve the above-mentioned object, the present invention, as illustrated in FIG. 1, includes a cylindrical lens barrel 10 having a light receiving body mounted on one end thereof, and a lens barrel 10. The optical lens 2 has a tubular shape inserted into the hollow hole, has a tubular body 30 that is slidably inserted in the optical axis direction into the lens barrel 10, and is generated with a change in ambient temperature. A focus correction mechanism for correcting defocus of the condenser lens 2 by moving the condenser lens 2, which is a rod shape made of a material having a thermal expansion coefficient larger than that of the lens barrel 10, and one end of which is the lens barrel. A bar 40 pivotally connected to one end of the.

Further, one end is pivotally connected to the other end of the bar 40, the other end is pivotally connected to the barrel 30, and a predetermined intermediate portion is swingingly moved to the lens barrel 10. And an arm 45 that is freely pivoted.

The bar 40 expands or contracts when the ambient temperature changes, and the lever 40 causes the cylinder 30 to move toward or away from the photoreceptor.

Alternatively, as illustrated in FIGS. 2 and 3, the lens barrel 10
A semicircular annulus inserted inside, one end of which is pivotally connected to the barrel 30 and each fulcrum 61 hung vertically on the shell of the lens barrel 10.
-A pair of arms 60-1 and 60-2, which are pivotally supported by the lens barrel 10 so as to swing freely while being in contact with the inner peripheral surface of the lens barrel 10 about the axes 1 and 61-2.
Is provided. Further, it is a rod-shaped member made of a material having a coefficient of thermal expansion larger than that of the lens barrel 10, one end of which is fixed to one end of the lens barrel 10, and the other end of which is the arms 60-1, 60-. A pair of bars 50-1, 50-2 pivotally connected to the other end of 2
Is provided.

Alternatively, it is assumed that the cylindrical body 30 is fitted and inserted into the outer side of the lens barrel 10, and the pair of arms 60-1 and 60-2 are pivotally supported so as to be in contact with the outer peripheral surface of the lens barrel 10 to perform a swinging motion. It has been done. Then, a pair of bars 50-1 and 50-2 is provided outside the lens barrel 10.

[0030]

The amount of change in the focal length of the condenser lens (the amount of defocus) is proportional to the change in ambient temperature. That is, when the ambient temperature changes and the temperature of the condenser lens rises, the focal length becomes short, and when the temperature of the condenser lens falls, the focal length becomes long.

The amount of bar length variation is also proportional to the change in ambient temperature. That is, if the ambient temperature changes and the temperature rises, the length of the bar becomes longer, and if the temperature drops, the length of the bar becomes shorter.

Therefore, by combining the arm whose length ratio between both ends and the fulcrum is selected and the bar whose thermal expansion coefficient is selected, a distance equal to the defocus amount of the condenser lens is collected. The cylindrical body that holds the optical lens can be moved in a direction that cancels the defocus.

That is, according to the present invention, the defocus of the condenser lens caused by the change in ambient temperature is automatically corrected. The present invention does not include a temperature sensor, a motor that rotates a rotating cylinder, a displacement detector that detects the amount of movement of a condenser lens, a control unit that controls the drive of the motor, etc. do not need. Therefore, the structure is simple and the cost is low.

According to the second and third aspects of the invention, the arm and the bar are close to the inside or outside of the lens barrel. Therefore, the optical device including the focus correction mechanism becomes compact.

[0035]

The present invention will be described in detail with reference to the drawings. The same reference numerals indicate the same objects throughout the drawings.

FIG. 1 is a sectional view of an embodiment of the present invention, FIG. 2 is a diagram of another embodiment of the present invention, (A) is an axial sectional view, and (B) is a sectional view.
FIG. 3 is a cross-sectional view of a portion of the chain line XX shown in (A), and FIG. 3 is a perspective view showing a main part of another embodiment of the present invention.

An example of the optical device according to the present invention is an infrared detector as shown in the figure. As shown in FIG.
The infrared detector 1 has a cylindrical casing mounted on a base 4,
The infrared detection element 1A is mounted in the housing so as to maintain a distance from the ceiling plate of the housing, and the infrared detection element 1A is formed so that the infrared detection element 1A can be cooled to a predetermined low temperature (about 80K). And a cooling device (for example, a cooling device using a Peltier effect type cooling element) mounted on the back surface side of the substrate.

An infrared transmitting plate 3 made of Ge or the like is fitted in a hole provided in a portion of the ceiling plate of the housing immediately above the infrared detecting element 1A. Infrared detector element 1A detects infrared rays emitted by an object
In order to detect the object by detecting the infrared rays with the infrared detector 1 by condensing the infrared rays, the cylindrical lens barrel 10 is mounted on the base of the infrared detector 1 so that the infrared detecting element 1A coincides with the axis. Stand 4
It is attached to.

The material of the lens barrel 10 may be aluminum: thermal expansion coefficient: 2.3 × 10 ^-5 stainless steel: thermal expansion coefficient: 1.1 × 10 ^-5 .

Aluminum is preferable from the viewpoint of making the lens barrel lighter. However, stainless steel is preferable from the viewpoint of increasing the difference from the coefficient of thermal expansion of the bar. Then, a condenser lens and an objective lens system (not shown) are attached to the lens barrel 10, the infrared rays emitted from the object are made into a parallel beam by the objective lens system, and the parallel beam is received by the infrared detection element 1A by the condenser lens. The light is focused on the surface.

The material of the condenser lens and the objective lens system is, for example, Ge, which has a large transmittance for wavelengths in the infrared region, and is generally called an infrared lens. 30 is
A cylindrical body made of the same material as that of the lens barrel 10 and having an outer diameter slightly smaller than the inner diameter of the lens barrel 10 and having the condenser lens 2 inserted in the hollow portion.

A guide pin 37 is vertically provided on the outer peripheral surface of the cylindrical body 30,
By inserting the guide pin 37 into the guide hole 38 provided in the lens barrel 10 that is long in the axial direction, the tubular body 30 is axially oriented inside the upper portion of the lens barrel 10 (the optical axis direction of the condenser lens 2). ) Is slidably inserted (within the length of the guide hole 38).

On the other hand, the lens barrel 10 is provided with a wide hole 35 facing the guide hole 38 and extending in the axial direction, and the axial center of the lens barrel 10 is protruded in the radial direction in the vicinity of the guide hole 38 in the outer peripheral portion of the lens barrel 10. A rectangular holder plate 49 that is parallel to is provided.

The cylindrical body 30 is provided with a projection plate 31 which projects into the hole 35 of the lens barrel 10. One end (lower end in the figure) of 40 is the outside of the lens barrel 10 on the infrared detector 1 side (holder plate).
It is a bar in the form of an elongated plate rod, which is pivotally connected to the root portion of 49) so as to be rotatable around the root side pin 41 as an axis.

The bar 40 is made of a material having a coefficient of thermal expansion larger than that of the lens barrel 10 (for example, an organic polymer material), and its length is smaller than the height of the lens barrel 10. As the material of the bar 40, polytetrafluoroethylene (trade name: Teflon) ··· coefficient of thermal expansion is 10 × 10 ^-5 volcanic carbonate ··· · coefficient of thermal expansion is 7 × 10 ⁻⁵ Can be considered.

Reference numeral 45 denotes an elongated thin plate, and a predetermined intermediate portion is mounted on the outside of the lens barrel 10 so as to be swingable about a pin-shaped fulcrum 46 which is hung vertically above the holder plate 49. It is the arm.

One end of the arm 45 is a projection plate of the tubular body 30.
The arm 32 is pivotally connected to the pin 32, and the other end of the arm 45 is pivotally connected to the tip pin 42 at the tip end (upper end in the figure) of the bar 40.

When the ambient temperature rises, for example, the refractive index of the condenser lens 2 increases and the focal length of the condenser lens 2 decreases. Therefore, the infrared rays incident through the objective lens system are not focused on the light receiving surface of the infrared detection element 1A.

However, since the present invention is constructed as described above, the bar 40 expands and extends in the tip direction (shown by the solid arrow), and the arm 45 swings about the fulcrum 46 and tilts ( (Upward to the right in the figure).

Therefore, by the lever action of the arm 45, the cylindrical body is
30 slides in the lens barrel 10 in a direction approaching the infrared detection element 1A (shown by a solid arrow). As a result, the condensing lens 2 causes the infrared detecting element to move by a predetermined amount (shortening the focal length).
Approach 1A.

That is, the defocus of the condenser lens 2 is automatically corrected, and the infrared rays are focused on the light receiving surface of the infrared detecting element 1A. When the ambient temperature drops, the focal length of the condenser lens 2 becomes longer. However, the bar 40 contracts and the lever 30 causes the cylindrical body 30 to move away from the infrared detection element 1A (indicated by a dotted arrow) by the lever action, and the defocus of the condenser lens 2 is automatically corrected.

If a mechanism combining the bar and the arm is provided opposite to the lens barrel, the movement of the lens barrel in the optical axis direction becomes smoother. 2-3, 50 is a lens barrel 10.
It is a ring-shaped bar base portion that is inserted into the lens barrel 10 and fixed to the base portion of the lens barrel 10 with a screw 51, and from the upper end surface of the bar base portion 50,
A pair of bars 50-1 and 50-2 are opposed to both ends of the diameter and extend upward.

The bar base portion integrally formed in this way, 5
The material of 0-1, 50-2 is, for example, an organic polymer material whose thermal expansion coefficient is larger than that of the lens barrel 10. 60-1,60-
Reference numeral 2 denotes a semi-circular ring-shaped arm made of a metal plate formed so that it can be properly inserted into the lens barrel 10.

A fixing piece 64-1 is provided at one end of the arm 60-1, and the fixing piece 64-1 is loosely inserted into the hole of the cylindrical body 30 at the upper portion of the fixing piece 64-1.
A pin 65-1 connected to the tubular body 30 is vertically provided. Similarly, the arm 60-2 is also provided with a fixing piece 64-2 at one end, and is provided on the upper side of the fixing piece 64-2 in another hole of the tubular body 30 (which is provided diametrically opposite to the above-mentioned hole). The pin 65-2 connected to the tubular body 30 is vertically installed by loosely inserting it into the hollow body).

On the other hand, pin-shaped supporting points 61-1 and 61-2 are vertically provided on the inner surface of the shell of the lens barrel 10 so as to face each other in the diametrical direction. The arm 60-1 has a predetermined intermediate portion around the fulcrum 61-1 as an axis,
The lens barrel (10) is mounted in the lens barrel (10) so that it can swing freely while contacting the inner wall surface of the lens barrel (10).

One end of the arm 60-1 is pivotally connected to the lens barrel 10 via the pin 65-1 as described above, and the other end thereof is
It is pivotally connected to the pin 52-1 at the tip of the bar 50-1. The other arm 60-2 has a fulcrum 61-2 at a predetermined intermediate position.
The arm 60-1 is mounted in the lens barrel 10 so as to swing freely in contact with the inner wall surface of the lens barrel 10 about the axis.

One end of the arm 60-2 is pivotally connected to the pin 65-2 as described above, and the other end is pivotally connected to the tip of the bar 50-2 via the pin 52-2. It is connected. With the configuration as described above, when the ambient temperature rises, for example, the refractive index of the condenser lens 2 increases and the focal length of the condenser lens 2 decreases.

However, the respective bars 50-1 and 50-2 uniformly expand and extend in the tip direction (shown by the solid arrow), and the respective arms 60-1 and 60-2 support the fulcrums 61-1, 61-2. It swings about -2 and tilts. As a result, by the lever action of the arms 60-1 and 60-2, the opposing portions of the tubular body 30 are pulled by the same force in the direction approaching the infrared detection element 1A,
That is, the condensing lens 2 approaches the infrared detecting element 1A by a predetermined amount (shortening amount of focal length).

That is, the defocus of the condenser lens 2 is automatically corrected, and the infrared rays are focused on the light receiving surface of the infrared detecting element 1A. Unlike FIGS. 2 and 3, the cylindrical body 30 is inserted into the lens barrel 10 and the pair of bars 50-1 and 50-2 are attached to the lens barrel 10.
And a pair of arms 60-1 and 60-2 on the outside of the lens barrel.
The same effect can be obtained by pivotally supporting the lens barrel 10 so that the lens barrel 10 swings in contact with the outer peripheral surface of the lens barrel 10.

[0060]

Since the present invention is constructed as described above, the present invention has the following effects.

By combining the arm whose length ratio between both ends and the fulcrum is selected and the bar whose thermal expansion coefficient is selected, the defocus of the condenser lens due to the change in ambient temperature can be reduced.
It can be corrected automatically.

The present invention does not require the temperature sensor, the motor, the displacement detector for detecting the amount of movement of the condenser lens, the control unit for controlling the drive of the motor, etc., which are required in the conventional focus correction mechanism. Has a simple structure and low cost.

According to the second and third aspects of the invention, the arm and the bar are close to the inside or outside of the lens barrel. Therefore, the optical device including the focus correction mechanism is small.

[Brief description of drawings]

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

FIG. 2 is a view of another embodiment of the present invention, (A) is a cross-sectional view in the axial direction, and (B) is a cross-sectional view taken along the chain line XX shown in (A).

FIG. 3 is a perspective view showing a main part of another embodiment of the present invention.

FIG. 4 is a sectional view of a conventional example.

[Explanation of symbols]

 1 Infrared detector 1A Infrared detector 2 Condenser lens 3 Infrared transmitting plate 5 Inner tube 7,37 Guide pin 8,38 Guide hole 10 Lens tube 30 Tube body 31 Projection plate 32,52-1,52-2,65- 1,65-2 pin 40,50-1,50-2 bar 50 bar base 45,60-1,60-2 arm

Claims (3)

[Claims] 1. A cylindrical lens barrel having a light-receiving body attached to one end thereof, and a cylindrical lens having a condenser lens inserted into a hollow hole, the lens barrel sliding in the optical axis direction. A focus correction mechanism that has a cylindrical body that is movably inserted, and that corrects a focus shift of the condenser lens that occurs with a change in ambient temperature by moving the condenser lens, A rod made of a material having a thermal expansion coefficient larger than that of the lens barrel,
One end is pivotally connected to one end of the barrel, one end is pivotally connected to the other end of the bar, and the other end is pivotally connected to the barrel. An arm having a predetermined intermediate portion pivotally supported by the lens barrel so as to be swingably movable, and the bar expands or contracts when the ambient temperature changes, and the bar is expanded by a lever action. A focus correction mechanism, characterized in that the cylindrical body is moved in a direction approaching or distant from the light receiving body. 2. The arm according to claim 1, wherein the arm is a semi-circular annular band inserted into a lens barrel, one end of which is pivotally connected to the barrel, and a predetermined intermediate portion is provided. An arm which is mounted in the lens barrel so as to be capable of swinging movement about a fulcrum vertically provided on a shell of the lens barrel, wherein the bar has a thermal expansion larger than that of the lens barrel. A bar made of a material having a coefficient, one end of which is fixed to one end of the lens barrel, and the other end of which is a bar pivotally connected to the other end of the arm, Focus correction mechanism. 3. The barrel according to claim 1 is inserted into the outer side of a lens barrel, and the arm according to claim 2 is attached to the outer peripheral surface of the barrel so as to be swingable. A focus correction mechanism, wherein the bar according to claim 2 is provided outside the lens barrel.