JPH0353215A - Exit optical device - Google Patents

Abstract

PURPOSE:To eliminate the variance of a size of an image forming spot diameter, while suppressing a light quantity loss of providing an opening corresponding to about half value width of an exit beam by a light source, and controlling the variance of a size of the spot diameter on an irradiated body, caused by the variance of an angle distribution of broadening of the exit beam by the light source. CONSTITUTION:On the light beam exit side of a collimator lens 2, an opening 14 is formed by vacuum vapor deposition, and as for the opening 14, shapes like a square slit, a round slot and an ellipse corresponding to within about half value width of a far field pattern (broadening angle distribution) of a semiconductor laser 1 are provided. Accordingly, while suppressing a light quantity loss, the variance of a size of the image forming spot diameter on the irradiates body caused by the variance of a broadening angle is controlled with accuracy of the opening 14. In such a way, the variance of a size of the image forming spot diameter is suppressed with a small light quantity loss.

Description

[Detailed Description of the Invention] [Industrial Application Field J] The present invention is applicable to laser beam collimator units and semiconductor lasers used in devices that record images by scanning a laser beam modulated by an image signal onto a recording medium. This article relates to an ejection optical device such as a pickup unit for optical discs using [Prior Art] In recent years, recording devices such as laser beam printers that record images by scanning laser beams have been widely used. A laser scanning device used in a conventional image recording device will be explained below with reference to FIG. In the schematic configuration diagram shown in Fig. 14. 41 is a semiconductor laser, 42 is a collimator lens, 43 is a polygon mirror which is a deflector, 44 is an imaging optical system, 45 is 2 [l! A photosensitive drum is a recording medium, and a beam from a semiconductor laser 4l modulated by an image signal is made into parallel light by a collimator lens 42, deflected by a deflector 43, and then directed onto a recording medium 45 by an imaging lens 44. The image is focused on and scanned. Here, III of the optical waveguide of the semiconductor laser 41
The structure is as shown in Figure 15, and the laser beam emission pattern has directionality (that is, the vertical distribution is longer than the horizontal distribution). Therefore, the emission pattern of the general-purpose semiconductor laser 4l spreads out in the shape of an ellipsoid, and the spread angle of the laser beam varies. Therefore, if such a semiconductor laser is used as a light source in a laser beam printer having the configuration shown in FIG. 14 without any modifications, the size of the imaged spot will also vary due to the variation in the spread angle of the light beam. Therefore, in order to prevent this, an aperture 48 for beam shaping is provided after the collimator lens 42. In the conventional configuration as described above, the aperture 48 has a lateral light intensity distribution (
It is common to use a circular aperture whose width is less than the half-width in the short axis direction of the ellipse. [Problems to be Solved by the Invention] However, in such a conventional configuration, as can be seen from FIG. As a result, the loss of light intensity of the light beam becomes considerable. This loss of light amount is particularly problematic in laser beam printers that require high-speed printing output. In other words, when the scanning speed of the light beam increases and the sensitivity of the photoreceptor drum is limited, it is necessary to increase the light intensity of the semiconductor laser, but the rated output value of a mass-produced semiconductor laser is 5 mW.
Therefore, there is a limit to this. Therefore, it is desirable to minimize the loss of light intensity of the beam from the semiconductor laser. On the other hand, if the aperture diameter of the circular aperture 48 is made larger than the diameter of the longitudinal distribution of the light beam (in the long axis direction of the ellipse) in order to reduce the loss of light quantity, the loss of light quantity can certainly be suppressed; In order to keep the beam spot diameter within a predetermined range, the variation in the spread angle of the lateral distribution of the light beam cannot be corrected by the aperture, so this variation must be strictly limited. As mentioned above, this is extremely difficult, and the purpose of providing an opening in the first place is halved. Furthermore, as shown in FIG. 17, the mounting angle of the semiconductor laser 41 is different from that of the barracks with respect to the main scanning direction of the light beam.
The diameter of the imaged spot is also tilted as shown in FIG. 17(a), and the thickness of the scanning line (indicated by d and acos θ) varies from product to product, which becomes a problem.

Juichi). An object of the present invention is to solve the above-mentioned problems by emitting light that eliminates variations in the size of the imaging spot due to variations in the spread angle of the light beam from the light source while suppressing the loss of light quantity. The goal is to provide equipment.

Another object of the present invention is to provide an injection optical device that can control the rotational phase of the injection beam. [A Thousand Steps to Solve the Three Problems] In order to achieve the above object, the present invention provides an injection optical device having a light source such as a semiconductor laser and an optical system that converts the beam from the light source into a parallel light beam. An aperture corresponding to approximately the half-width of the emitted beam is provided to control variations in the spot diameter on the irradiated object due to variations in the spread angle distribution of the emitted beam due to the light source. The opening can be provided in various places, such as directly on the collimator lens, in the lens barrel, or in the presser foot for fixing the collimator lens inside the mirror.

[Function] In the configuration of the present invention, variations in the spread angle distribution of the emitted beam are regulated by the aperture corresponding to approximately the half-width of the far field pattern (spread angle distribution) of a light source such as a semiconductor laser. In addition to suppressing the loss of light amount, it is possible to control the variation in the diameter of the imaged spot on the object to be irradiated with the accuracy of the aperture [Example] Fig. 1 shows the first example of the present invention. ．． In the schematic configuration diagram of this laser emitting device, l is a semiconductor laser, 2 is a collimator lens, 3 is a base that supports the flat conductor laser 1, 4 is a spring that fixes the semiconductor laser 1 to the base 3,
5 is a lens barrel that supports the collimator lens 2, and 6 is a lens barrel 5.
The holder 7 that supports the is a part of the scanning optical device. The spring 4 is fixed to the base 3 with a screw 10, and the positioning groove 1a of the semiconductor laser 1 engages with the claw 4a of the spring 4, thereby determining the phase of the laser. The phase of the fixed spring 4' is determined by a positioning pin 3a provided on the base 3. Since the collimator lens 2 and the semiconductor laser l require bin adjustment, the lens barrel 5 is movable in the optical axis direction (Z direction) inside the holder 6, and after adjustment, the lens barrel 5 is moved to the holder 6. On the other hand, s6a, which is fixed with adhesive, is a large hole for this adhesive. In addition, the collimator lens 2 and the semiconductor laser l require adjustment to align the optical axes with each other, and for this purpose the base 3 and holder 6 are movable within the xY plane. 3 and boulder 6 are fixed with screws 13. A vacuum Ml is provided on the light beam exit side of the collimator lens 2.
An opening l4 is formed by this. Since the aperture l4 must determine the phase with respect to the semiconductor laser 1, the shape of the collimator lens 2 is such that the ineffective area of the lens 2 is D.
It is cut into a letter shape. A D-shaped hole is also formed in the lens barrel 5 to fit with the D-shape of the collimator lens 2, and the phase is determined between the collimator lens 2 and the aperture 14 and the semiconductor laser. The phase between the two is determined. Furthermore, in order to fix the laser emitting device 20 to the scanning optical device 7, the base 3 and the holder 6 are provided with through holes 3b and 6, respectively.
6b is provided. These holes 3b. By passing the fixing screw l5 through 6b and screwing it into the scanning optical device 7,
A laser emitting device 20 is fixed to the scanning optical device 7. The positioning of the laser emitting device 20 is performed using the positioning bin l6.
This is done by fitting the hole 6c of the holder 6 and the hole 3C of the base 3. In the first embodiment of instant formation described above, the phases of the aperture l4 and the semiconductor laser l are determined by a collimator lens adjustment jig (not shown). That is, in order to fix the laser emitting device l to the A alignment jig of the collimator lens, the through hole 3b. - Pass the screw through 6b and fix it. Positioning is performed using a positioning bin provided on the adjustment jig of the collimator lens and the hole 6c of the holder 6.

As described above, since the phase of the semiconductor laser 1 has already been determined with respect to the holder 6, the phase of the laser 1 is determined with respect to the adjustment jig of the collimator lens. On the other hand, the phase of the collimator lens of the aperture l4 with respect to the adjustment jig is determined as follows. Focus adjustment of the collimator lens 2 is performed by moving the lens barrel 5 in the optical axis direction using an actuator of an adjustment jig.
By providing a protrusion that fits into the shape of the groove 5a of the lens barrel 5,
The phase of the collimator lens of the aperture l4 with respect to the adjustment jig is determined.

As described above, the phases of the semiconductor laser l and the aperture l4 are determined using the adjustment jig of the collimator lens. As shown in FIGS. 2(a), (b), and (C), the above-mentioned frontage l4 corresponds to the far field pattern (
It has a rectangular slit shape, a round oblong hole shape, and an elliptical shape that correspond to approximately half {di width of the spread angle distribution), thereby suppressing the loss of light amount and preventing condensation on the irradiated object due to the above-mentioned spread angle variation. The variation in the image spot diameter is due to the aperture 1.
It will be regulated with an accuracy of 4. In the above embodiment, the opening l4 was formed by vapor deposition, but it can also be formed by other methods as shown in FIGS. 3(a), (b), and (c). That is, in FIG. 3(a), the aperture l4 is formed by polishing the central part of the surface of the glass lens 2, leaving the outer surface as a bare surface. In this way, a collimator lens 2 with an open opening is formed. In No. 31E (b), when the collimator lens 2 is molded with resin, a textured finish is applied to the outside of the opening l4. In FIG. 3(C), by creating a member with an opening l4 by outsert molding, the opening l4
is formed. In the first and second embodiments described above, the aperture l4 and the collimator lens 2 are integrally formed, but in the third embodiment shown in FIG. 4, they are constructed separately. In FIG. 4, 23 indicates the collimator lens 2
It is a presser ring for fixing the collimator lens 2 to the abutment part (not shown) formed inside the lens barrel 5 by pressing the surface opposite to the spherical surface of the collimator lens 2. The collimator lens 2 is generally a spherical lens, and the aperture l4 side has a spherical shape. Therefore, if the aperture l4 is elliptical, the collimator lens 2 and the aperture l4 of the holding ring 23 If the apertures are brought into contact with each other, there will be a two-point contact and the fixation of the collimator lens 2 will become unstable. Therefore, in the case of an elliptical aperture, a circular/chamfered part 24 is formed around the aperture so that the collimator lens 2 can be fixed. The holding ring 23 can be fixed stably to the lens barrel 5 by machining screws on the outer diameter of the holding ring 23 and the inner diameter of the lens barrel 5. Alternatively, it may be fixed with adhesive.
In addition, the material is made of resin mold, and the lens barrel 5 is made of elastic material.
The presser ring 23 may also be fixed. In addition, in FIG. 4, 23a is a groove that engages with the attachment portion of the actuator of the aforementioned adjustment jig. Other points are the same as the first embodiment shown in FIG. Figure 5 shows a fourth embodiment of the laser injection device. The first method of aperture l4 affects the diameter of the imaged spot on the irradiated object and requires high dimensional accuracy. Furthermore, if the opening l4 has a non-circular shape such as an ellipse, advanced processing is required.

Therefore, in the fourth embodiment, the lens barrel is integrally molded with a resin mold. However, resin has a large coefficient of thermal expansion, and there is a high risk of the bottle becoming misaligned due to changes in the temperature environment surrounding the laser injection equipment. Therefore, in the fourth embodiment, only the part around the opening l4 is made of the resin molded member 27, and the outer periphery is made of the metal member 27.
8 is outsert molded. This results in more stable performance compared to forming the entire lens barrel with a resin mold. This resin molded member 27 may be fixed to the metal member 28 by adhesive, or may be fixed using elasticity. As a method of fixing the collimator lens 2 to the metal member 28, a holding ring method as shown in FIG. 4 may be used,
It can be easily fixed using instant adhesive or ultraviolet curing adhesive.

In this case, in order to prevent the adhesive from entering the functional parts of the collimator lens 2, it is preferable to provide an adhesive groove 28a in the metal member 28 constituting the lens barrel, as shown in FIG. The adhesive groove 28a may be provided on the collimator lens 2 side by providing a stepped portion in the collimator lens 2 as shown in FIG. Figure 8 shows a fifth embodiment of the laser injection device. In the fifth embodiment, an aperture 30 is formed in the cover glass of the semiconductor laser l. The light beam emitted from the semiconductor laser 1 is spread out in an elliptical cone shape, and the cover glass has an aperture 3 that corrects the spread of the light beam into a cone shape.
The beam is shaped by setting 0. opening 3
0 may be etched or deposited on the cover glass, or
Alternatively, it may be formed by a cap member. Figure 9 shows the sixth embodiment. In this example, the aperture l4
is formed on the holding ring 32 of the collimator lens 2. The degree of coaxiality between the aperture l4 and the collimator lens 2 affects the diameter of the imaged spot on the object to be illuminated, and high dimensional accuracy is required.
The coaxiality of the aperture l4 and the collimator lens 2 is ensured by fitting this guide portion 32a into a cylindrical six portion 33a formed on the inner diameter portion of the lens barrel body portion 33. Figure 10 shows the seventh embodiment. In this embodiment, since an elliptical opening is difficult to process, an opening l4 is formed in the press part 35 and finished. In this case, in order to ensure coaxiality between the press part 35 in which the opening 14 is formed and the collimator lens 2, a fixing part for attaching the collimator lens 2 and the press part 35 is formed on the lens barrel body 36 side. ．． Pressed part 3 with collimator lens 2 and aperture l4
5 may be adhesively fixed to the lens barrel, or may be held down by a holding ring 37.

Figure 11 shows the eighth embodiment. In this actual flow example, opening 1
4 is formed on the lens barrel 38, and a retaining ring 39 of the collimator lens 2 is incorporated on the light incident side. Thickness t of opening l4
It is desirable that the material be thin in order to prevent reflections on the inner wall. By the way, in laser beam printers etc., feeding unevenness tends to occur in the paper feeding direction (sub-scanning direction), so if the circular beam is used as is, scanning pitch unevenness will occur as shown in Figure 12. Therefore, as shown in FIG. 13, it is conceivable to make the imaging spot diameter in the paper feeding direction (sub-scanning direction) larger than the diameter in the main-scanning direction. This is a semiconductor laser
The far field pattern (spread angle distribution) and the direction of the aperture l4 are regulated, and at the imaging spot position, the imaging spot diameter in the paper feeding direction (sub-scanning direction) is made larger than the diameter in the main scanning direction. , which makes feeding unevenness that occurs in the paper feeding direction (sub-scanning direction) less noticeable. The above practical example has means for regulating the spread angle of the semiconductor laser l and the rotational direction of the aperture l4 with respect to the main scanning direction of the laser beam. That is, the means for determining the rotational phase of the elliptical beam emitted from the exit optical device with respect to the housing in which the device is attached is a collimator lens or a lens barrel of the collimator lens (as shown in FIG. 1).
a), or the holding ring of the mirror slip (groove 23 shown in Fig. 4).
(a, etc.), or a part of the opening of the lens barrel, and furthermore, a holder of the lens barrel (such as hole 6b in Figure 1), a semiconductor laser (such as 1a in Figure 1), or a semiconductor laser base ( hole 3b in Figure 1). [Effects of the Invention] As explained above, according to the present invention, the light beam output side of the collimator lens corresponds to within approximately the half width of the far field pattern (spread angle distribution) of a light source such as a semiconductor laser. By providing a highly accurate aperture (elliptical, long round, rectangular slit shape, etc.), variations in the diameter of the imaged spot due to variations in the spread angle distribution can be suppressed with minimal light loss. Also, the spread angle separation and the aperture direction relative to the main scanning direction. By regulating the inclination of the imaging spot 1, it is possible to obtain a spot diameter with little variation. Furthermore, by using an elliptical aperture, the diameter of the imaging spot in the paper feeding direction (sub-scanning direction) at the imaging position is made larger than the diameter in the main-scanning direction. This makes feeding unevenness that occurs in the paper feeding direction (sub-scanning direction) less noticeable.

[Brief explanation of drawings]

FIG. 1 is a schematic exploded view of the structure of an embodiment of the present invention, FIG. 2 is a diagram showing the form of the opening, FIGS. 3 to 11 are explanatory diagrams of other embodiments, and FIGS. 12 and 13 are A diagram explaining a method for making feeding unevenness in the paper feeding direction less noticeable. Figure 14 is a schematic explanatory diagram of a conventional example. Figure 15 is a diagram showing the spread angle distribution of a semiconductor laser. Figure 16 is a diagram showing the result of a conventional aperture. FIG. 17 is a diagram showing how the variation in the image spot diameter is suppressed, and is a diagram illustrating the inclination of the imaging spot. l... Semiconductor laser, 2... Collimator lens. 3...Base, 4...Fixing spring,
5, 28, 33. 36, 38... lens barrel, 6...
...Holder l4...Opening, 23, 32, 37,
39... Holder ring

Claims (1)

[Claims] 1. In an emission optical device having a light source and an optical system that converts the beam from the light source into a parallel light beam, an aperture corresponding to approximately the half width of the beam emitted by the light source is provided, and the beam emitted by the light source is An injection optical device that regulates variations in the spot diameter on the irradiated object due to variations in the spread angle distribution. 2. The exit optical device according to claim 1, wherein the aperture has a substantially elliptical shape. 3. The exit optical device according to claim 1, wherein the opening is in the shape of a round elongated hole. 4. The exit optical device according to claim 1, wherein the opening has a rectangular slit shape. 5. The ejection optical device according to claim 1, further comprising means for determining the rotational phase of the substantially elliptical beam emitted from the ejection optical device with respect to a housing to which the ejection optical device is mounted.