JP2000028946A - Light source device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent irregular reflection of laser light on the inner peripheral surface of a window provided on a protective cap. SOLUTION: The inside end of an inner peripheral surface 27a of a window 27 is an end point A of the shape of the window 27, and its outside end is an end point B of the shape of the window 27, and ∠BAC formed by end points A and B and a point C determined on the inside surface of a protective cap 28 on the outside of the end point A with respect to the optical axis is set as a limited acute angle θA. In order to prevent laser light L emitted from a light emission point 26a from being made incident on the inner peripheral surface 27a, a condition θA<θT is satisfied where θT is ∠B'AC when the intersection between laser light L which is emitted from the light emission point 26a and comes into contact with the end point A and the outside surface of the protective cap 28 is denoted as B'. If this condition is satisfied, laser light L is neither made incident on the inner peripheral surface 27a nor irregularly reflected, and therefore, incidence of irregularly reflected laser light on a collimator lens 22 is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light source device for performing optical writing using laser light in an LBP, a digital copying machine, or the like.

[0002]

2. Description of the Related Art FIG. 8 shows a configuration of a scanning optical device for performing optical writing scanning on a photosensitive member or the like in a conventional LBP or the like. The light source device 2 including a lens and a laser drive circuit is fixed,
The collimated light emitted from the light source device 2 passes through the cylinder lens 3 and then enters the reflection surface of the polygon mirror 4. The polygon mirror 4 is rotated by a motor.

[0003] The collimated light deflected and scanned by the polygon mirror 4 passes through the scanning lens 5 and returns to the turning mirror 6.
Incident on a photoreceptor drum (not shown). In order to prevent the writing position from shifting, the BD mirror 7 is moved in the traveling direction of the collimated light transmitted through the end of the scanning lens 5.
Is provided, and the collimated light reflected by the BD mirror 7 is incident on the BD sensor 8, and the BD sensor 8 performs synchronization detection to adjust the writing position.

FIG. 9 shows a configuration diagram of the light source device 2. The light source device 2 includes a collimator lens 11 and a semiconductor laser output device 12. Semiconductor laser output device 12
Inside the laser chip 13 and the photodiode 14
And its periphery is protected by a protective cap 16 having a window 15 in front. The laser light L emitted from the light emitting point 13 a of the laser chip 13 passes through the window 15 and becomes the laser light Lc via the collimating lens 11. On the other hand, the back surface laser light emitted from the light emitting point 13b is detected by the photodiode 14, and plays a role of keeping the light amount by the laser chip 13 constant.

FIG. 10 is a cross-sectional view of the light source device 2. The collimator lens 11 is mounted on a lens barrel 17, and the semiconductor laser output device 12 is press-fitted and fixed to a holder 18 after optical axis alignment and focus adjustment. Have been. Also,
The lens barrel 17 and the holder 18 are fixed on the surface of the photosensitive drum so that the focus and the irradiation position of the laser beam Lc are correct.

A laser chip 13 attached to the semiconductor laser output device 12 is surrounded by a protective cap 16 having a window 15 for transmitting a laser beam L and a glass plate 19 attached inside the protective cap 16. Is covered and protected. However, the inner peripheral surface 15a of the window 15 forms a cylindrical surface parallel to the optical axis.

[0007]

However, in the above-mentioned conventional example, the laser beam L emitted from the light emitting point 13a may be irregularly reflected on the inner peripheral surface 15a of the window 15, thereby causing a flare and a printing quality. There are problems such as a cause of reduction.

An object of the present invention is to solve the above-mentioned problems,
An object of the present invention is to provide a light source device capable of preventing irregular reflection of laser light on an inner peripheral surface of a window of a protective cap.

[0009]

According to the present invention, there is provided a light source device comprising a semiconductor laser light source and a collimating lens for irradiating a photosensitive medium with light. The laser light transmitting window provided on the cap has an inner peripheral surface inclined with respect to an optical axis formed by the laser light emitting direction and the center of the collimating lens.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the embodiments shown in FIGS. FIG. 1 is a sectional view of a light source device 21 according to the first embodiment. Light source device 21
Is a collimating lens 22 and a semiconductor laser output device 23
It is composed of The collimating lens 22 is a lens barrel 24
The semiconductor laser output device 23 is press-fitted and fixed to the holder 25. The lens barrel 24 and the holder 25 are adhered so that the focus and the irradiation position of the laser beam Lc are correct on the surface of the photosensitive drum (not shown).

In the semiconductor laser output device 23,
Edge-emitting laser chip 2 that emits laser light L
The laser chip 26 is provided with a window 27.
And a glass plate 29 attached to the protective cap 28 covers and protects the periphery. Further, a photodiode 30 is provided behind the laser chip 26.

The laser light L emitted from the light emitting point 26a of the laser chip 26 is applied to a window 27, a collimating lens 22.
Through the laser beam Lc. The laser light emitted from the light emitting point 26b is detected by the photodiode 30, and is used for an APC operation for maintaining a constant light amount from the laser chip 26. This APC operation utilizes the fact that the laser light L and the backside laser light change substantially equivalently with respect to the laser drive current, and usually outside the effective area by the scanning laser light, immediately before the start of writing for each scanning or paper feeding. These light amount adjustments are performed during the page interval.

In this embodiment, the shape of the window 27 is expanded outward, the inner end of the inner peripheral surface 27a is defined as an end point A, and the outer end is defined as an end point B. When the point C is defined outside the end point A,
Let C be some limited acute angle θ _A.

Further, when ΔB′AC is θ _T when the intersection of the laser light L emitted from the light emitting point 26a and the outer surface of the protective cap 28 and the laser light L in contact with the end point A is defined as θT, the light emitting point 26a The laser light L emitted from the inner peripheral surface 27a
It is necessary to satisfy the following conditional expression in order to prevent irradiation. θ _A <θ _T … (1)

When this conditional expression (1) is satisfied, the inner peripheral surface 2
Since the laser light L does not enter the laser beam 7a and is not irregularly reflected, it is possible to suppress the irregularly reflected laser light from entering the collimating lens 22.

Further, it is necessary to make θ _A in the protective cap 28 an acute angle, but as long as conditional expression (1) is satisfied,
limit for the minimum value of theta _A are not, are readily fabricated in the form of window 27.

FIG. 2 shows a light source device 31 according to the second embodiment.
FIG. 3 is a partially enlarged view of a window 33 provided in a protective cap 32, and the same members as those in the first embodiment are denoted by the same reference numerals. The inner end of the inner peripheral surface 33a of the window 33 is defined as an end point A, and the outer end is defined as an end point B.
A point C is defined on the inner side surface of the sample 2 and a point D is defined on the outer side surface thereof, so that ∠BAC is an obtuse angle.

If the laser beam L emitted from the light emitting point 26a is reflected near the end point A and the reflected light Lg is incident on the laser chip 26 again, and ∠DBA is θ _P , the end point B of the window 33 is defined as the optical axis. End point B 'in the direction away from
Inner peripheral surface 33b of the ∠DB'A of changing was theta _B in
Reflected light Lh at the distance from the laser chip 26,
It does not enter the laser chip 26 again.

Further, by moving the reflection position of the laser light L from the end point A to the end point B, the path of the reflected light moves in a direction away from the laser chip 26, and therefore, the reflected light is reflected at any position on the inner peripheral surface 33a. Also, no reflected light enters the laser chip 26.

That is, in order to prevent the reflected light from re-entering the laser chip 26, the following conditional expression must be satisfied. θ _P <θ _B … (2)

FIGS. 4 and 5 are a cross-sectional view and a partially enlarged view of the optical device 41 when the shape of the window in the second embodiment is changed.保護 Protective cap 42 whose BAC is obtuse
, The shape of the window 43 is slightly widened, and the laser light L emitted from the light emitting point 26a is reflected near the end point B of the inner peripheral surface 43a of the window 43, and enters the collimator lens 22 as reflected light Li. ∠DBA in case θ _L
Then, the reflected light Lj on the inner peripheral surface 43 b when the end point A is changed to the end point A ′ in the direction away from the optical axis does not enter the collimator lens 22.

Further, when the reflection position of the laser light L moves from the end point B to the end point A, the path of the reflected light moves in a direction away from the collimating lens 22, so that the reflected light is reflected at any position on the inner peripheral surface 43a. Also, no reflected light enters the collimating lens 22.

That is, in order to prevent the reflected light from entering the collimating lens 22, it is necessary to satisfy the following conditional expression. θ _B <θ _L … (3)

Therefore, the light reflected on the inner peripheral surface of the protective cap 42 is reflected by the laser chip 26 and the collimating lens 2.
In order to prevent the light from being incident on 2, conditional expression (2)
It is necessary to satisfy the following conditional expression that satisfies (3). θ _P <θ _B <θ _L … (4)

In this embodiment, as compared with the first embodiment, the laser beam L has a certain angle with respect to the optical axis, and when the emitted laser beam L passes through the window, the angle at which the laser beam L spreads is limited. Only the main beam can be scanned.

FIG. 6 is a sectional view of a light source device 51 according to the third embodiment, and FIG. 7 is a partially enlarged view thereof. In this embodiment, the window 53 of the protective cap 52 is provided with two inner peripheral surfaces 53a and 53b. These inner peripheral surfaces 53a and 53b satisfy the conditional expressions of the first and second embodiments, respectively.

As in the first and second embodiments, an end point A, an end point B, a point C, and a point D are determined, respectively. Also, the inner peripheral surface 53
An intersection of a and 53b is defined as an end point E, and a point on a plane passing through the end point E and perpendicular to the optical axis is defined as F. At this time, the inner peripheral surface 53
If と FEA composed of a and the plane EF is θ _EA , and ∠FEB composed of the inner peripheral surface 53b and the plane EF is θ _EB , the inner peripheral surface 5
In order for 3a and 53b to satisfy the conditions of the first and second embodiments, respectively, the following conditional expressions are required. θ _EB > θ _T (5) θ _P <θ _EA <θ _L (6)

In this embodiment, two inner peripheral surfaces 53 are provided.
The irregular reflection of the laser beam L can be suppressed by a and 53b, and only the target main beam can be correctly scanned, and image defects due to flare can be prevented.

[0029]

As described above, in the light source device according to the present invention, by limiting the shape of the window of the protective cap provided in the semiconductor laser output device, the light reflected on the inner peripheral surface of the window is reduced by the laser chip and the laser chip. It is possible to prevent the light from entering the collimating lens.

[Brief description of the drawings]

FIG. 1 is a sectional view of a first embodiment.

FIG. 2 is a sectional view of a second embodiment.

FIG. 3 is a partially enlarged view of a window.

FIG. 4 is a sectional view of the second embodiment.

FIG. 5 is a partially enlarged view of a window.

FIG. 6 is a sectional view of a third embodiment.

FIG. 7 is a partially enlarged view of a window.

FIG. 8 is a configuration diagram of a conventional scanning optical device.

FIG. 9 is a configuration diagram of a conventional light source device.

FIG. 10 is a sectional view of a conventional example.

[Explanation of symbols]

 22 Collimating lens 26 Laser chip 27, 33, 43, 53 Window 28, 32, 42, 52 Protective cap 29 Glass plate

Claims (4)

[Claims] 1. A light source device comprising a semiconductor laser light source and a collimating lens for irradiating a photosensitive medium with light, wherein an inner peripheral surface of a laser light transmitting window provided on a cap of the semiconductor laser light source is directed to a laser light emitting direction. A light source device, wherein the light source device is tilted with respect to an optical axis formed by the light source and the center of the collimator lens. 2. An inner peripheral surface shape of a cap window of the semiconductor laser light source is inclined at an angle that widens with respect to a laser light emitting direction or an angle that narrows with respect to a laser light emitting direction.
The light source device according to claim 1, wherein the laser reflected light on the inner peripheral surface of the cap window has an angle that does not enter an effective range of the collimator lens. 3. A ridge formed on both sides of the cap window between the laser chip side end and the collimator lens side end of the inner peripheral surface of the cap window. The light source device according to claim 1, wherein the laser reflected light on the peripheral surface has an angle that does not enter the effective range of the collimator lens. 4. The light source device according to claim 3, wherein the light source device includes the semiconductor laser light source, the collimating lens, an optical deflector, and a scanning lens, and is mounted on a device that performs optical scanning writing on a photosensitive drum.