JPH0593881A - Laser light source device - Google Patents

Abstract

PURPOSE:To restrain the change of an image-formation state caused by thermal change and to prevent image quality from being deteriorated. CONSTITUTION:A difference between the variation of a distance caused by the thermal change of a supporting member which supports a laser generation part 11 and a collimator lens 12 for collimating a laser beam 5 from the laser generation part 11 so that they may keep specified positional relation and the variation of the focal distance of the lens 12 associated with the change of the wavelength of the laser beam 5 caused by the thermal change is made within the allowable depth of focus of the lens 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser light source device having a laser generator, and a light beam scanning device used in, for example, a copying machine, a facsimile, a laser beam printer or the like for forming an image by electrophotography. In particular, the present invention relates to a laser light source device in which a laser generator and a collimator lens for collimating a laser from the laser generator are supported in a predetermined distance relationship.

[0002]

2. Description of the Related Art A laser emitted from a laser generator is modulated by an image signal, passes through an optical system such as a collimator lens, and is imaged on a photoreceptor or the like to form an image according to the image signal.

In order for this image formation to be achieved with high resolution and high accuracy, the positional relationship of each optical system must be accurately determined.

However, in the laser light source device, the temperature rise due to the emission of the laser and the temperature rise in the peripheral portion cause a large thermal expansion of the supporting member that supports the laser generating portion and the collimator lens in a predetermined distance relationship. Due to the expansion, the predetermined distance relationship between the laser generator and the collimator lens changes.

On the other hand, the laser light source device is miniaturized by collimating the laser from the laser generating portion with a collimator lens provided at a position very close to the laser generating portion.

For this reason, the collimator lens is an extremely short focus lens having a focal position at the laser emission position of the laser generator located at a very close position, and an image forming state due to the change in the distance relation. The impact on is particularly large.

Japanese Unexamined Patent Publication No. 55-43577 discloses a laser light source device that copes with the problem.

In this device, the total amount of thermal deformation of each supporting member supporting the laser generating portion and the collimator lens in a predetermined distance relationship is within the allowable depth of focus of the collimator lens.

[0009]

However, even with this one,
The image formation state of the laser changes as the temperature rises with time, which causes deterioration of image quality.

As a result of an experiment conducted by the present inventor on this point, it was found that the focal length of the collimator lens was changed due to the change in the wavelength of the laser itself due to the temperature rise, which had an influence on the image formation state. ..

According to the present invention, the change in the focal length of the collimator lens due to the temperature rise works so as to shift the focal position rearward with respect to the laser generating portion, and the thermal change in the supporting member causes the laser to generate the focal position. Based on a further finding that it works so as to shift the lens part forward, the heat change is offset within the allowable depth of focus of the collimator lens, so that there is no problem with the conventional laser light source device. It is intended to provide.

[0012]

In order to achieve the above object, a laser light source in which a laser generator and a collimator lens for collimating a laser from the laser generator are supported so as to maintain a predetermined distance relationship. In the apparatus, the difference between the amount of change in the distance due to the heat change of the supporting member that performs the support and the amount of change in the focal length of the collimator lens due to the change in the wavelength of the laser due to the heat change is the tolerance of the collimator lens. The main feature is that it is within the depth of focus.

A clearance portion is formed at a position adjacent to a support surface of the support member for fixing the collimator lens barrel, and a clearance portion is formed away from the collimator lens barrel, and one position in the optical axis direction of the collimator lens barrel is set as the support surface. It can be configured to be fixed by adhesion.

[0014]

According to the above-mentioned main structure of the present invention, the support member thermally expands as the temperature around the laser generating portion rises, and the distance between the laser generating portion and the collimator lens is increased, so that the focal position of the collimator lens is increased. While the laser works to shift it forward, the wavelength of the laser increases and the focal length of the collimator lens increases, causing the focus position of the collimator lens to shift backward with respect to the laser generator. Work like. The difference between the amount of change in heat of the support member and the amount of change in the focal length of the collimator lens is set to be within the allowable depth of focus of the collimator lens. And the focal position of the collimator lens are kept within the allowable depth of focus of the collimator lens, so that the image formation state of the laser can be made constant.

To fix one portion of the lens barrel of the collimator lens to the supporting surface of the supporting member by adhesion, an escape portion is formed in a portion adjacent to the supporting surface of the supporting member so as to separate from the collimating lens lens barrel. Even if adhesive with a low viscosity is poured between them to adhere, the adhesive will rotate to the contact part with the collimator lens barrel on the part other than the supporting surface and remove the excess part of the collimator lens barrel. Also, it is possible to prevent the position of the collimator lens from changing due to heat change of the lens barrel, and to fix the base point of the collimator lens.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A laser light source device as a first embodiment of the present invention shown in FIGS. 1 to 6 will be described.

As shown in FIGS. 1 to 4, the laser light source device of this embodiment emits a semiconductor laser 11, a collimator lens 12 for collimating the laser 5 from the semiconductor laser 11, a plano-convex lens 13, and a laser beam. Laser 5
And the aperture 14 for finally limiting the cross-sectional shape thereof to, for example, major axis: minor axis = about 10: 1.

In the present embodiment, a laser 5 having an elliptical cross section having a ratio of major axis to minor axis emitted from a semiconductor laser 11 is about 3: 1, and the ratio of major axis to minor axis is 10: Two prisms 15 and 16 which are flattened into an extremely flat ellipse close to 1 are provided on the way.

The two prisms 15 and 16 refract the laser 5 emitted from the semiconductor laser 11 in two steps so that the optical axis is not tilted.

Collimator lens 12, plano-convex lens 1
3, the aperture 14 and the prisms 15 and 16 are arranged and attached in the optical axis direction on the first support 21 having a shape close to a groove-shaped member.

Collimator lens 1 of first support 21
A second support 22 is applied to the rear end provided with 2 and is fixed by a screw 23.

A through hole 24 is provided in the center of the second support 22, a laser base 25 is press-fitted into the through hole 24 from the rear side, and a rear facing step 26 in the middle of the through hole 24 is applied.
Laser holding table 27 protruding forward from the laser base 25
The semiconductor laser 11 is held at the tip of the collimator lens 12 and is positioned on the optical axis of the collimator lens 12.

A semiconductor laser driving circuit board 28 is attached to the rear surface of the second support 22 by fitting.

The laser 5 emitted from the laser holding table 27 is collimated by the collimator lens 12 and then flattened by the prisms 15 and 16 into light having an elliptical cross section with an appropriate aspect ratio. Plano-convex lens 1
3. After passing through the aperture 14, it is emitted as band-shaped light having a required aspect ratio.

The emitted laser beam 5 is directed to a polygon mirror after passing through, for example, a cylindrical lens for correction of surface tilt, and is deflected by the polygon mirror to form an image on a photoconductor, which is then main-scanned. Then, since the photoconductor moves in the sub-scanning direction, an image according to the image signal obtained by modulating the laser 5 is formed on the photoconductor.

Here, in order for the collimator lens 12 to collimate the laser 5 from the semiconductor laser 11,
The focal position of the collimator lens 12 needs to match the laser 5 emission position of the semiconductor laser 11. Then, when the deviation occurs, the plano-convex lens 1
The state in which an image is formed on the photoconductor via 3 changes.

Therefore, in order to maintain the above-mentioned positional condition, the semiconductor laser 11 and the collimator lens 12 are set to have a predetermined distance relationship.

However, as the temperature of each part rises with time due to the emission of the laser 5, the members that maintain the predetermined distance relationship, that is, the first support 21, the second support 22, the laser holder 27, and The lens barrel 29 of the collimator lens 12 changes due to heat. That is, it thermally expands and changes the predetermined distance relationship.

The wavelength λ of the laser 5 emitted from the semiconductor laser 11 is increased as described above in consideration of the case where the laser 5 having a wavelength of about λ = 780 nm is used in view of the photosensitivity of the photoconductor used for electrophotographic image formation. Figure 5 against temperature
Shows the change in wavelength as shown in.

When the wavelength of the laser 5 changes, the focal length of the collimator lens 12 corresponding to it changes as shown in FIG. Therefore, even if the predetermined positional relationship is satisfied, the laser 5 emission position of the semiconductor laser 11 and the focal position of the collimator lens 12 are displaced due to the change in the focal length of the collimator lens 12.

Therefore, the image quality is affected and the image quality is degraded.

Therefore, in order to solve these problems, in this embodiment, the first position of the lens barrel 29 holding the collimator lens 12 at a position rearward of the collimator lens 12 is set to the first position. The support 21 is adhered and fixed to the support surface 21b on the inner surface of the peripheral wall of the support 21 with the adhesive 31.

The lens barrel 29 is pressed against the first support 21 by the leaf spring 32 in the vicinity of the fixing point by the adhesion, and does not affect the thermal deformation of the lens barrel 29 around the fixing point by the adhesion. The stabilization is aimed at. Reference numeral 33 is a mounting screw for the leaf spring 32.

Due to the above supporting structure, it is the stepped surface 2 as shown in FIG. 2 that changes the predetermined distance relationship between the semiconductor laser 11 and the collimator lens 12 during thermal deformation.
When 6 is considered as the mounting reference surface of the semiconductor laser 11, the stepped surface 26 of the second support 22 is used to measure the first support 2
The dimension L ₁ up to the joint surface with 1 and the fixing point between the first support 21 and the lens barrel 29 to the collimator lens 1 of the lens barrel 29.
The dimension L ₂ of the lens barrel 29 up to the second holding position and the first distance from the joint surface between the first support 21 and the second support 22 to the fixing point of the lens barrel 29 of the first support 21. ₂ is a heat change with the dimension L ₃ of the support 21 and the dimension L _{4 of} the laser holding base 27 from the step surface 26 to the support point of the laser holding base 27 supporting the semiconductor laser 11.

The amount of change in heat of these dimensions L _{1 to} L ₄ is determined by the material of each member and the actual dimensions.
The heat change of _{1 to} L ₃ increases the distance relationship between the semiconductor laser 11 and the collimator lens 12 to move the focus position of the collimator lens 12 to the front of the semiconductor laser 11, while the dimension L ₄ is By reducing the distance relationship between the semiconductor laser 11 and the collimator lens 12, the focal length of the collimator lens 12 is
It works to shift backwards.

Therefore, by setting the material of each of the support members, the dimension L ₁ + L ₂ + L ₃ and the dimension L ₄ , the thermal change of the dimension L ₁ + L ₂ + L ₃ and the thermal deformation of the dimension L ₄ are offset. Therefore, the distance relationship between the semiconductor laser 11 and the collimator lens 12 can be kept within a predetermined range.

The supporting surface 21b of the first supporting body 21
The adjacent portion adjacent to the escape portion 21a is away from the lens barrel 29.
Is formed in.

As a result, even if the adhesive 31 having a low viscosity is used and the adhesive 31 is poured between the support surface 21b and the lens barrel 29 to perform the adhesion, the adhesive 31 is not applied to the adhesive other than the support surface 21b. Turn the lens barrel 29 to the support surface 2
It is possible to avoid adhesion even with a portion other than 1a.

Therefore, the heat change of the lens barrel 29 is caused by the support surface 21.
It is configured to expand and contract on both sides with respect to the fixing point by adhesion to b, so that the direction and the amount of displacement of the collimator lens 12 due to the heat change of the lens barrel 29 can be uniquely defined.

On the other hand, even if the semiconductor laser 11 and the collimator lens 12 are kept in a predetermined distance relationship, the wavelength λ due to the temperature rise of the laser 5 emitted from the semiconductor laser 11 is increased.
Changes the focal length of the collimator lens 12 and shifts the focal position of the collimator lens 12 to the rear of the semiconductor laser 11.

In order to cancel this, the heat change on the support structure is set so that the focal position of the collimator lens 12 is shifted forward from the semiconductor laser 11, and the wavelength λ of the laser 5 is changed. This cancels out the fact that the focal position of the collimator lens 12 works so as to shift to the rear of the wavelength λ.

Therefore, the relationship of the change amount of the dimension L ₁ + L ₂ + L ₃ > the change amount of the dimension L ₄ is set, and the displacement amount δ ₁ of the focal position of the collimator lens 12 caused by the difference in the support structure and the laser 5 are obtained. The difference from the displacement amount δ ₂ of the focal position of the collimator lens 12 caused by the change of the wavelength λ is set within the range of the allowable depth of focus of the collimator lens 12.

The amount of change in heat of each of the dimensions L ₁ , L ₂ , L ₃ and L ₄ is determined by the dimensions and the materials of the first support 21, the second support 22, the laser holding base 27 and the lens barrel 29. And the coefficient of linear thermal expansion according to.

The first support 21 and the second support 22 are made of aluminum, and the laser holder 27 is made of copper, which may be the same or different in material, but the first support 21 and the second support 22 may be made of different materials. The linear thermal expansion coefficients of the support 22, laser holder 27, and lens barrel 29 of _{No. 2} are set as α ₁ , α ₂ , α ₃ , and α ₄ for convenience, and the distance between the semiconductor laser 11 and the collimator lens 12 on the support structure is set. The calculation formula of the heat change amount δ ₁ of is as follows.

[0045] _{δ 1 = (L 1 · α} 1 + L 2 · α 2 + L3 · α 3) - (L4 · α 4) ......... 1 then the wavelength variation gamma ₀ of the laser 5 relative to the temperature T _C, γ
₀ = λ / ° C., and the variation amount γ ₁ of the focal length f ₀ of the collimator lens 12 due to the wavelength variation is γ with respect to the wavelength λ.
₁ = f ₀ / λ.

Accordingly, the variation of the focal length of the collimator lens 12 due to the variation of the wavelength λ of the laser 5, that is, the displacement δ ₂ of the focal position is δ ₂ = γ ₀ γ ₁ = f ₀ / T _C ………………………………………………… given by 2.

Therefore, when the permissible depth of focus C of the collimator lens 12 is set, the amount of thermal change δ ₁ of the distance between the semiconductor laser 11 and the collimator lens 12 and the wavelength λ of the laser 5 change the collimator lens 12. The difference δ ₀ (= δ ₁ −δ ₂ ) from the amount of thermal change δ ₂ at the focal position is δ ₀ <C ……………………………………………………………… ... is set to 3.

When the focal length of the plano-convex lens 13 is f ₂ , the longitudinal magnification β is β = (f ₂ / f ₁ ) ²・ ・ ・ ………… because of the relationship with the focal length f ₁ of the collimator lens 12. …………………………………………………… 4.

Therefore, when the optical system of f ₂ >> f ₁ is adopted, the fluctuation amount of the focal length f ₁ of the collimator lens 12 fluctuates by β times at the image forming point, whereas the focal length f of the plano-convex lens 13 is f. The fluctuation amount of ₂ does not affect the image formation point.

In this embodiment, L ₁ = 2.5 × 10 ^-3 m L ₂ = 6.5 × 10 ^-3 m L ₃ = 6 × 10 ^-3 m L ₄ = 1.3 × 10 ^-3 m α ₁ = 21.5 × 10 ^-6 1 / ° C α ₂ = 11.5 × 10 ^-6 1 / ° C α ₃ = 21.5 × 10 ^-6 1 / ° C α ₄ = 16.5 × 10 ^-6 1 / ° C δ ₁ = 2.4 × 10 ^-7 m / ° C = 0.24 μm / ° C γ ₀ = 0.2 nm / ° C γ ₁ = 1 μm / nm δ ₂ = 0.2 μm / ° C δ = 0 0.04 μm / ° C. β = 10 ² = 100 C = 0.05 μm / ° C. In this embodiment, the collimator lens has a high refractive index and low dispersion in accordance with the variation amount γ ₁ of the focal length of the collimator lens with wavelength variation. The mold material is used.

The second embodiment of the present invention shown in FIGS. 7 and 8 is a block lens 41 in which the collimator lens 12, the plano-convex lens 13 and the prisms 15 and 16 in the first embodiment are integrally formed. The feature is that it is adopted and that it is fixed on the first support body 21 as it is without a lens barrel.

In this embodiment, L ₁ = 2.5 × 10 ^-3 m L ₂ = 5 × 10 ^-3 m L ₃ = 6.9 × 10 ^-3 m L ₄ = 1.3 × 10 ^-3 m α ₁ = 21.5 × 10 ^-6 1 / ° C α ₂ = 7.5 × 10 ^-6 1 / ° C α ₃ = 21.5 × 10 ^-6 1 / ° C α ₄ = 16.5 × 10 ^-6 1 / ° C δ ₁ = 2.2 × 10 ^-7 m / ° C = 0.22 μm / ° C γ ₀ = 0.2 nm / ° C γ ₁ = 1 μm / nm δ ₂ = 0.2 μm / ° C δ = 0 .02 μm / ° C. With such a structure, the semiconductor laser 11 and the block lens 41 are much simplified compared to the case of the first embodiment.
The element of the thermal change of the distance from the collimator lens section 12a is simplified by the absence of the lens barrel. Therefore, the design becomes easy.

[0053]

According to the main features of the present invention, when the laser is emitted from the laser generating part and the temperature rises, the supporting member thermally expands to increase the distance between the laser generating part and the collimator lens. , While the focal position of the collimator lens works to move forward with respect to the laser generator, the wavelength of the laser increases and the focal length of the collimator lens increases, so that the focal position of the collimator lens is the laser. It works so as to be shifted backward with respect to the generating part, and the difference between the amount of change in heat of the support member and the amount of change in the focal length of the collimator lens is within the allowable depth of focus of the collimator lens. Therefore, the relationship between the laser generator and the focal position of the collimator lens should be within the allowable depth of focus of the collimator lens due to any of the above thermal changes. Kept, it can be made constant imaging conditions of the laser, image quality by Atsushi Nobori is avoided as drops.

To fix one portion of the lens barrel of the collimator lens to the supporting surface of the supporting member by adhesion, a relief portion is formed in a portion adjacent to the supporting surface of the supporting member to separate from the collimating lens lens barrel. Even when using a low-viscosity adhesive, the adhesive will rotate to the contact area with the collimator lens barrel other than the supporting surface and fix the excess part of the collimator lens barrel to the support member. Since it is possible to prevent the flip-up and make the base point of the position change of the collimator lens due to the heat change of the lens barrel constant, it is possible to achieve high accuracy by an easy assembling work.

[Brief description of drawings]

FIG. 1 is a perspective view showing an overall structure of a laser light source device as a first embodiment to which the present invention is applied.

2 is a cross-sectional view of the apparatus of FIG. 1 on a horizontal plane.

3 is a cross-sectional view of the device of FIG. 1 on a vertical plane.

FIG. 4 is a perspective view showing a mounted state of a collimator lens of the apparatus of FIG.

FIG. 5 is a graph showing a relationship of a wavelength change with respect to a temperature change of a light beam.

FIG. 6 is a graph showing the relationship between changes in the focal length of the collimator lens and changes in the wavelength of the light beam.

FIG. 7 is a vertical cross-sectional view showing a laser light source device as a second embodiment of the present invention.

FIG. 8 is a plan view of the device of FIG. 5 Light Beam 11 Semiconductor Laser 12 Collimator Lens 12a Collimator Lens 13 Plano-Convex Lens 21 First Support 21a Escape 21b Support Surface 22 Second Support 24 Through Hole 25 Laser Base 26 Stepped Surface 27 Laser Holder 29 Lens barrel 31 Adhesive 41 Block lens

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Internal reference number FI Technical indication H04N 1/04 104 Z 7251-5C (72) Inventor Shoji Nishitani 1006 Kadoma, Kadoma, Osaka Prefecture Matsushita Denki Sangyo Co., Ltd.

Claims (2)

[Claims] 1. A laser light source device in which a laser generator and a collimator lens for collimating a laser from the laser generator are supported so as to maintain a predetermined distance relationship. A laser characterized in that the difference between the change amount of the distance and the change amount of the focal length of the collimator lens due to the change of the wavelength of the laser due to the heat change is within the allowable depth of focus of the collimator lens. Light source device. 2. A relief portion is formed in a portion of the support member adjacent to a support surface for fixing the collimator lens barrel to separate from the collimator lens barrel, and the one portion in the optical axis direction of the collimator lens barrel is supported by the support member. The laser light source device according to claim 1, wherein the laser light source device is fixed to the surface by adhesion.