CN2745056Y - Laser bar device for measuring focal length of thermal lens - Google Patents

Abstract

The utility model discloses a laser bar device for measuring focal length of thermal lenses, comprising a He-Ne laser and an optoelectronic receiver. The utility model is characterized in that a beam expander telescope is equipped on an optical path which is behind the He-Ne laser. A convex glass provided with fixed focus is equipped between a laser bar needed to be measured and the optoelectronic receiver. There is a fixed distance between the convex glass and the back surface of the laser bar. The laser emitted by the He-Ne laser through the beam expander telescope passes through the laser bar with parallel light and then focuses on the optoelectronic receiver through the convex glass. The formula that f=(f 1 <2>/f) +(d/2n 0) +b-f can be used for conveniently and accurately measuring a larger thermal lens f-value, an f-laser bar thermal lens f-value, a f 1-convex glass f-value and the difference of a lens system focal distance and the convex glass focal distance on basis of a delta-pumping reaching the balance of heat. The lens system is composed of the laser bar and the convex glass. The formula can also measure the length of a d-laser bar, the index of refraction of an n-laser bar and the fixed distance of a b-convex glass and the back surface of the laser bar.

Description

A kind of laser bar thermal lens focometry device

Technical field

The utility model relates to a kind of thermal lensing effect of laser bar, especially relates to a kind of thermal focal length measurement mechanism of laser bar.

Background technology

The pump energy that solid state laser absorbs in operation process, except that fraction is exported with laser mode, most of energy change heat into and are deposited on makes it produce temperature rise in the working-laser material, constantly repeating under pumping and the conduction of heat, thermograde constantly increases in the operation material, takes away up to heating power and liquid coolant to reach thermal equilibrium when heat equates.In the operation material existence of thermograde make originally refractive index fully uniformly operation material become the class lens medium, light beam focuses on after by operation material, is called thermal self-focusing.Under the situation of symmetric pump, garden cylindricality laser bar becomes the class globe lens, is also referred to as thermal lensing effect.Thermal lensing effect increases sharply the laser-beam divergence angle, and can produce damage from laser at material internal in the inner real focus that produces of operation material.In order to alleviate the influence of thermal lensing effect to Laser Devices, people adopt several different methods that thermal lensing effect is compensated.But, in order to realize the compensation of thermal lensing effect effectively, at first needing ins all sorts of ways obtains the focal length value of thermal lens, and method wherein comparatively commonly used is the direct method of measurement, introduced a kind of measuring method of thermal focal length among the embodiment as No. 02266147.6 Chinese utility model patent instructions that bulletin is authorized on August 27th, 2003, by solid laser medium, can measure the thermal focal length value of solid laser medium under the different pump powers with helium-neon laser output He-Ne Lasers by being arranged on focometry device behind the solid laser medium.But the laser bar thermal lens focal length when long thermal focal, is difficult for determining the focal position when directly measuring with this device between tens centimetres to tens meters.

Summary of the invention

Technical problem to be solved in the utility model is to provide a kind of thermal focal length measurement mechanism that can measure accurately and easily than the laser bar of long-focus value at above-mentioned prior art present situation.

The utility model solves the problems of the technologies described above the technical scheme that is adopted: a kind of thermal focal length measurement mechanism of laser bar, comprise He-Ne laser instrument and photelectric receiver, light path behind the described He-Ne laser instrument is provided with beam expanding telescope, be provided with convex lens between testing laser rod and the described photelectric receiver with fixed focal length, the rear surface of described convex lens and described laser bar is at a distance of a fixed range, described He-Ne laser instrument emitted laser incides on the described laser bar with directional light by described beam expanding telescope, and pass described laser bar by described convex lens focus to described photelectric receiver, utilize formula $f=\frac{f_1^2}{\mathrm{\&delta;}}+\frac{d}{2n_0}+b-f_1,$ Obtain the thermal focal length value, in the formula, the thermal focal length value of f-testing laser rod, f ₁The fixed focal length value of-described convex lens, when δ-pumping reaches thermal equilibrium, the focal length of the lens combination that testing laser rod and described convex lens are formed and the focal length of described convex lens poor, the length of d-testing laser rod, n ₀The refractive index of-testing laser rod, the fixed range of described convex lens of b-and testing laser rod rear surface.

Fixed range between the center of described convex lens and the rear surface of described laser bar preferably equals the fixed focal length value of described convex lens.

Described photelectric receiver comprise a pin hole light hurdle that can move forward and backward and be arranged on behind the described pin hole light hurdle the silicon photocell that can move forward and backward with described pin hole light hurdle.

The aperture on described pin hole light hurdle is preferably less than 1 millimeter.

Compared with prior art, the focal length of the focal length of the system of testing laser rod and lens composition and lens was poor when advantage of the present utility model was to reach thermal equilibrium by the measurement pumping, utilized formula $f=\frac{f_1^2}{\mathrm{\&delta;}}+\frac{d}{2n_0}+b-f_1$ Can make things convenient for exactly and measure for longer thermal focal length value, in the formula, the thermal focal length value of f-testing laser rod, f ₁The focal length value of-convex lens, the focal length of the focal length of the lens combination of testing laser rod and convex lens composition and convex lens was poor when δ-pumping reached thermal equilibrium, the length of d-testing laser rod, n ₀The refractive index of-testing laser rod, the distance of b-convex lens and testing laser rod rear surface; When the distance that convex lens and testing laser rod rear surface is set when us equaled the focal length value of convex lens, promptly during b=f1, computing formula can be reduced to $f=\frac{f_1^2}{\mathrm{\&delta;}}+\frac{d}{2n_0}$ Photelectric receiver comprises a pin hole light hurdle that can move forward and backward and is arranged on the silicon photocell that can move forward and backward with pin hole light hurdle behind the pin hole light hurdle, can the convenient position of determining focus exactly, measure focal length value effectively.

Description of drawings

Fig. 1 is the structural representation of the utility model embodiment one;

Fig. 2 is the structural representation of the utility model embodiment two.

Embodiment

Embodiment describes in further detail the utility model below in conjunction with accompanying drawing.

Embodiment one: as shown in Figure 1, a kind of thermal focal length measurement mechanism of laser bar comprises He-Ne laser instrument 1, beam expanding telescope 2, and testing laser rod 3, laser bar 3 back are that known focal length is f ₁Lens 4, pin hole light hurdle 5 and be arranged on pin hole light hurdle 5 after silicon photocell 6, pin hole light hurdle 5 and silicon photocell 6 can move forward and backward together, the distance of the rear surface of the center of convex lens 4 and laser bar 3 is b, when the laser bar pumping reaches thermal equilibrium, mobile pin hole light hurdle 5 and silicon photocell 6, the light signal that makes its reception is for maximum, measure the focus of the lens combination of determining that laser bar 3 and convex lens 4 are formed this moment, the difference of the focal length value F of the lens combination that laser bar 3 and convex lens 4 are formed and the focal distance f 1 of convex lens 4 is δ, then utilizes formula $f=\frac{f_1^2}{\mathrm{\&delta;}}+\frac{d}{2n_0}+b-f_1$ Just can obtain the thermal focal length value of laser bar 3, in the formula, the thermal focal length value of f-laser bar 3, f ₁The fixed focal length value of-convex lens 4, when 3 pumpings of δ-laser bar reach thermal equilibrium, the focal length of the lens combination that laser bar 3 and convex lens 4 are formed and the focal length of convex lens 4 poor, the length of d-laser bar 3, n ₀The refractive index of-laser bar 3, the fixed range of the center of b-convex lens 4 and laser bar 3 rear surfaces.

Embodiment two: as shown in Figure 2, a kind of thermal focal length measurement mechanism of laser bar, its basic structure is identical with embodiment one, and difference is the focal length value that the fixed range of the center of convex lens 4 and laser bar 3 rear surfaces equals convex lens 4, i.e. b=f ₁, this moment, computing formula was reduced to $f=\frac{f_1^2}{\mathrm{\&delta;}}+\frac{d}{2n_0},$ The corresponding data value substitution formula that records just can be obtained the thermal focal length value of institute's survey laser bar.

In the foregoing description, the aperture on pin hole light hurdle 5 is preferably less than 1 millimeter.

Claims (4)

1, a kind of thermal focal length measurement mechanism of laser bar, comprise He-Ne laser instrument and photelectric receiver, it is characterized in that the light path behind the described He-Ne laser instrument is provided with beam expanding telescope, be provided with convex lens between testing laser rod and the described photelectric receiver with fixed focal length, the rear surface of described convex lens and described laser bar is at a distance of a fixed range, described He-Ne laser instrument emitted laser incides on the described laser bar with directional light by described beam expanding telescope, and pass described laser bar by described convex lens focus to described photelectric receiver, utilize formula $f=\frac{f_1^2}{\mathrm{\&delta;}}+\frac{d}{{2n}_0}+b-f_1,$ Obtain the thermal focal length value, in the formula, the thermal focal length value of the described laser bar of f-, f ₁The fixed focal length value of-described convex lens, δ-when described laser bar pumping reaches thermal equilibrium, the focal length of the lens combination that described laser bar and described convex lens are formed and the focal length of described convex lens poor, the length of the described laser bar of d-, n ₀The material refractive index of-described laser bar, the fixed range of described convex lens of b-and described laser bar rear surface.

2, the measurement mechanism of a kind of laser bar thermal lens focal length as claimed in claim 1 is characterized in that the fixed range between the rear surface of the center of described convex lens and described laser bar equals the fixed focal length value of described convex lens.

3, the measurement mechanism of a kind of laser bar thermal lens focal length as claimed in claim 1 or 2 is characterized in that described photelectric receiver comprises a pin hole light hurdle that can move forward and backward and is arranged on behind the described pin hole light hurdle silicon photocell that can move forward and backward with described pin hole light hurdle.

4, the measurement mechanism of a kind of laser bar thermal lens focal length as claimed in claim 3, the aperture that it is characterized in that described pin hole light hurdle is less than 1 millimeter.

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