JP2001308439A - Light emitting module and its assemblying method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light emitting module where an interval between a condensing lens and a pin hole is strictly regulated and an irradiated laser beam is uniformly maintained to be thin for a long valid detection range. SOLUTION: The light emitting module is provided with a laser diode arranged on one end side of a light guide formed in a frame; the condensing lens which is arranged on the other end side of the light guide, converges the laser beam emitted from the laser diode, and forms the laser beam; and a pin hole board which is arranged close to the opposite side of the laser diode with respect to the condensing lens, and narrows the laser beam. In the condensing lens, the peripheral edge of the incident face side enlarges the other end side of the light guide and it abuts on a reference plane formed in the frame in a step. The pin hole board is fixed to the frame so that the other end side opening of the light guide is blocked. A collar for regulating the interval of the condensing lens and the pin hole board is inserted between them.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light-emitting module used for a laser sensor for detecting the presence or absence of ink droplets and the amount of ink droplets in an ink-jet printer, and more particularly, to a light-emitting module for a long detection range. The present invention relates to a light emitting module that can form a laser beam having a uniform diameter.

[0002]

2. Description of the Related Art Conventionally, as a laser sensor used for detecting ink droplets in an ink jet printer, for example, as shown in FIG. 5, a laser diode 1 and a laser beam B0 emitted from the laser diode 1 are shown. A light emitting module 100 having a condenser lens 20 for condensing the laser beam B1 to form a laser beam B1, a lens 202 for condensing an incident laser beam B3, and a laser beam B4 condensed by the lens 202. A laser sensor 300 having a light receiving module 200 having a light receiving element 201 is used. In the laser sensor 300, the ink droplet D is included in the laser beam B1.
And the change in the amount of light at that time is
By detecting at 01, the presence or absence of the ink droplets D or the number of the ink droplets D is detected.

The diameter of the ink droplet D is usually several tens of μm, and in order to accurately detect the diameter, the diameter of the laser beam when the ink droplet D crosses is determined by the diameter of the ink droplet D. It is desirable that the thickness be reduced to about 10 times or less. Therefore, the light emitting module 100
In FIG. 5, this is achieved by irradiating the laser beam B1 which has been narrowed by the condenser lens 20, as shown in FIG. The converged laser beam B1 converges once and then diverges again.
The lens 202 is provided in the light receiving module 200 in order to condense the light.

In the laser sensor 300, the ink droplet D is focused on the convergence point P at which the diameter of the laser beam B1 is minimized.
, And the diameter d of the laser beam B1 at the convergence point P is expressed as follows: where the numerical aperture of the condenser lens 20 is NA and the wavelength of the laser beam is λ.
It is obtained by the formula of 22λ / NA. Therefore, by increasing the numerical aperture NA of the lens, the diameter of the laser beam B1 can be reduced, and it is possible to cope with minute ink droplets D.

On the other hand, the effective detection range L0 of the narrowed laser beam B1 can be approximated by the equation of depth of focus = λ / (NA) ^2. If the diameter d of the laser beam B1 is reduced by this equation, It can be seen that the effective detection range L0 becomes shorter as the value becomes smaller. However, in an ink-jet printer, replacement of an ink cartridge (not shown) tends to cause a shift in an ink dropping position, so that it is necessary to extend the effective detection range L0. Would not be able to respond sufficiently.

[0006]

Therefore, the present inventors, as shown in FIG. 4, move the laser beam B1 condensed by the converging lens 2 from the converging point P to the laser beam B1.
It has been found that a narrow laser beam diameter can be maintained uniformly over a relatively long effective detection range L by irradiating a laser beam B2 formed by the aperture with a pinhole 31 provided at a position close to the laser beam B2 from a light emitting module. Was.
This is the laser beam B1 focused by the focusing lens 2.
Is determined by the diffraction effect while being narrowed down by the pinhole 31.

However, according to the present inventors, the distance S from the condenser lens 2 to the pinhole 31 and
When the relationship between the ink droplet D and the laser beam diameter at the position where the ink droplet D crosses the laser beam B2 was investigated,
In the vicinity of the interval Sw at which a desired laser beam diameter can be obtained, it was found that the change in the laser beam diameter with respect to the change in the interval S was very large. Therefore, to maintain a narrow laser beam diameter over a long effective detection range,
It is important to precisely set the interval Sw.

In view of the above, the present invention has been made under the above circumstances, and the distance between the condenser lens and the pinhole is strictly defined so that the length of the irradiated laser beam is long. It is an object of the present invention to provide a light emitting module that can be maintained thin and uniform over an effective detection range.

[0009]

DISCLOSURE OF THE INVENTION In order to solve the above problems, the present invention employs the following technical means.

That is, a light emitting module provided according to the first aspect of the present invention includes a laser diode disposed at one end of a light guide formed on a frame, and a laser diode disposed at the other end of the light guide. A condensing lens for condensing laser light emitted from the laser diode to form a laser beam; and a converging lens disposed on the opposite side of the condensing lens on the side opposite to the laser diode to narrow the laser beam. And a pinhole plate for the light-emitting module, wherein the condensing lens has a reference surface which is formed stepwise on the frame such that a peripheral portion on the incident surface side expands the other end of the light guide path. And the pinhole plate is fixed to the frame so as to close the opening at the other end of the light guide path. Between the Nhoru plate, it is characterized in that color for defining these intervals are interposed.

In the light emitting module provided by the first aspect of the present invention in which the above technical means are taken, the other end of the light guide path formed in the frame collects the laser light emitted from the laser diode. The condensing lens is positioned by abutting a reference surface formed on the frame, and the pinhole plate for narrowing the laser beam condensed by the condensing lens is positioned via a collar that defines an interval. With such a configuration, the distance between the condenser lens and the pinhole plate can be strictly defined by the collar. Therefore, the laser beam condensed by the condensing lens is determined by its diffraction action while being narrowed down and narrowed by a pinhole provided in the pinhole plate, and the diameter of the narrowed laser beam has a long effective detection length. It can be kept uniform over the range.

In a preferred embodiment, the collar has a ring shape made of a wire having a uniform cross section, and a part of the collar is cut out. It can be configured to be formed by slightly shifting in the thickness direction of the collar.

According to the embodiment to which such a configuration is applied, the notch abutting end formed in the collar interposes the collar between the condenser lens and the pinhole plate. At this time, the collar can be made elastic by compressing the notch abutting end in the thickness direction of the collar and pressing it so as to be flush. Accordingly, the condenser lens is fixed while being pressed against the reference surface, so that the distance between the condenser lens and the pinhole plate can be more strictly defined, and the position can be firmly fixed. .

In another preferred embodiment, the collar has a circular cross section.
Since the collar can support the condenser lens and the pinhole plate with a tangent line, the distance therebetween can be more strictly defined.

By forming the collar from phosphor bronze, it is possible to prevent excessive elasticity from acting on the pinhole plate and deforming the pinhole plate.

Further, as another preferred embodiment, the condensing lens may be formed of a resin material having chemical resistance and having the same transmittance as acrylic.

According to the embodiment to which such a configuration is applied, for example, when used for detecting ink droplets in an ink jet printer, the condenser lens is deformed even if minute ink droplets adhere. Alternatively, deterioration can be prevented.

In still another preferred embodiment, the condensing lens is an aspheric lens having a plane of incidence, and the plane is brought into contact with the reference plane, whereby the laser is formed. The inclination of the condenser lens with respect to the optical axis of light can be prevented, and the distance between the condenser lens and the pinhole can be more strictly defined. Further, since the reference surface can be a flat surface, the frame can be easily processed.

Further, as another preferred embodiment,
The pinhole plate may include a general portion having a predetermined thickness and a thin portion pressed in the thickness direction, and a pinhole may be formed through the thin portion.

According to the embodiment to which such a configuration is applied, the rigidity of the pinhole plate as a whole can be made sufficient to press the condenser lens against the reference surface via the collar, and The hole can be made appropriate by minimizing its axial length and eliminating unnecessary diffraction. Moreover, since the thin portion can be easily formed by press working, the manufacturing cost can be reduced.

In still another preferred embodiment, the pinhole plate may be formed of metal.

According to the embodiment to which such a configuration is applied, for example, when used for detecting ink droplets in an ink jet printer, the pinhole plate is deformed even if minute ink droplets adhere. Alternatively, deterioration can be prevented.

According to a second aspect of the present invention, there is provided a method of assembling a light emitting module, comprising: a laser diode disposed at one end of a light guide formed on a frame; and a laser diode disposed at the other end of the light guide. A condensing lens for condensing the laser light emitted from the laser diode to form a laser beam; and A method for assembling a light emitting module comprising a pinhole plate for narrowing down, wherein the peripheral edge of the incident surface side is brought into contact with a stepped reference surface so as to increase the diameter of the other end side of the light guide path. A step of incorporating the condenser lens into the other end of the light guide path, and contacting the collar for defining the distance between the condenser lens and the pinhole plate with the condenser lens. A step of location, placing the pinhole plate so as to close the other end opening of the light guide,
Fixing the pinhole plate to the periphery of the other end side opening of the light guide path while compressing the collar.

According to the method for assembling a light emitting module provided by the second aspect of the present invention in which the above technical means are employed, a light emitting module having the same effect as the light emitting module described in the first aspect is provided. Can be provided.

In a preferred embodiment, the step of fixing the pinhole plate is performed by thermocompression bonding or ultrasonic welding of the pinhole plate to the peripheral edge of the other end opening of the light guide path. be able to.

According to the embodiment to which such a configuration is applied, for example, when used for detecting ink droplets in an ink-jet printer, minute ink droplets are used in addition to the pinhole plate and the light guide path. Even if the pinhole plate adheres to the fixed portion of the end side opening and the peripheral portion, it is possible to prevent the pinhole plate from dropping or shifting. In addition, since the fixing method is not a method using an adhesive or the like, the fixing portion does not become distorted at the time of curing, and thus the position shift and deformation of the pinhole plate can be prevented.

According to another preferred embodiment, the step of arranging the pinhole plate includes a step of arranging a plurality of projections formed in the direction in which the laser beam travels from the peripheral portion of the other end opening of the light guide path. The projection is performed by fitting a projection into a through hole formed at a position corresponding to the projection of the pinhole plate, and the step of fixing the pinhole plate is performed by melting and expanding the projection by heat. The configuration can be performed.

According to the embodiment to which such a configuration is applied, if the protrusion is fitted into the through hole of the pinhole plate, the position of the pinhole is accurately defined.
A separate process for making the pinhole correspond to the optical axis of the condenser lens can be omitted, and the manufacturing efficiency can be improved. Further, the fixed portion between the pinhole plate and the peripheral portion of the opening at the other end of the light guide path can exhibit the same effect as the above-described effect when the pinhole plate is thermocompression-bonded or ultrasonically welded. it can.

Other features and advantages of the present invention will become more apparent from the following description of embodiments of the present invention.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be specifically described below with reference to the drawings.

FIG. 1 is an exploded perspective view showing an embodiment of a light emitting module according to the present invention, and FIG.
3 (a) and 3 (b) are enlarged views of the collar in FIG. 1, and FIG. 4 is a schematic view for explaining the operation of the light emitting module according to the present invention. . In the following, a description will be given of an example in which the light emitting module is used as a light emitting module used in a laser sensor for detecting ink droplets of an ink jet printer.
In these figures, the same reference numerals are given to members and elements equivalent to those shown in FIG. 5 showing a conventional example.

As shown in FIGS. 1 and 2, in the light emitting module A, a frame 5 has a laser diode 1 and a laser beam B0 emitted from the laser diode 1 (FIG. 4).
And a condensing lens 2 for condensing the laser beam B1 and forming a laser beam B1. And a pinhole plate 3. Also, between the condenser lens 2 and the pinhole plate 3,
A collar 4 for defining these intervals is provided.

In the present embodiment, the frame 5 is made of a hard plastic such as polycarbonate. The frame 5 has a plate-like base 51 and a plate-like base 51 as shown in FIGS. A hollow light guide path 52 penetrating from a base 51 to a columnar protrusion 60.
Are formed. A laser mounting portion 53 for fixing the laser diode 1 is provided at one end of the light guide path 52, that is, at the end of the light guide path 52 on the plate-like base 51 side.
The other end side is provided with a lens mounting portion 54 for fixing the condenser lens 2 and the pinhole plate 3.
And a pinhole plate mounting portion 55 for fixing the pinhole plate.

As shown in FIG. 2, the light guide path 52 is formed in a substantially cylindrical hollow shape so that the laser beam B0 travels. The light guide path 52 has an inner diameter slightly larger than an outer diameter of a later-described can seal portion 11 of the laser diode 1, and has a center axis perpendicular to the plate-shaped base 51. ing. Further, as shown in FIG. 2, the light guide path 52 is provided with a shielding rib 57 projecting from the inner wall toward the center of the cylinder, so that the laser light reflected on the inner wall can be prevented from traveling.

As shown in FIG.
In the present embodiment, a cylindrical step is formed on the back surface of the plate-like base 51 so as to increase the diameter of one end of the light guide path 52, and the inside diameter of the stem 12 of the laser diode 1 will be described later. The diameter is slightly larger than the outer diameter, and the center axis thereof is made to coincide with the center axis of the light guide path 52. Further, the laser mounting portion 53 has a laser reference surface 53a which is a plane perpendicular to the central axis of the light guide path 52. The laser diode 1 adjusts its laser light emission direction to the other end of the light guide path 52. , And is positioned by bringing the stem 12 into contact with the laser reference surface 53a.

As shown in FIGS. 1 and 2, in the present embodiment, the lens mounting portion 54 is formed in a cylindrical shape so as to increase the diameter of the other end of the light guide path 52. Are made equal to the outer diameter of the condenser lens 2, and the central axis thereof is made to coincide with the central axis of the light guide path 52. Further, the lens mounting portion 54 has a lens reference surface 54 a that is a plane perpendicular to the central axis of the light guide path 52, and the condenser lens 2 fits into the lens mounting portion 54 while its entrance surface is Positioning is performed by bringing the peripheral edge of the side 2a into contact with the lens reference surface 54a. Also,
Since the lens reference surface 54a is a flat surface, it can be easily formed when it is formed on the frame.

As shown in FIG. 1, a notch 54b may be provided in a part of the lens mounting portion 54 to facilitate the fitting of the condenser lens 2.

Since the lens reference surface 54a is formed so as to have a predetermined interval between the lens reference surface 54a and the laser reference surface 53a, the laser beam B0 (see FIG. Can be converged at the convergence point P.

As shown in FIGS. 1 and 2, in the present embodiment, the pinhole plate mounting portion 55 is
Are formed at positions close to the lens mounting portion 54 at a predetermined distance from the opening edge on the other end side of the lens, and three projections 56 projecting in the direction in which the laser beam is irradiated.
Is provided. These projections 56 are formed at positions corresponding to three through holes 35 described later provided in the pinhole plate 3, and by fitting these into the positions of the pinhole plate 3 in the rotation direction. Can be defined, and the position of a pinhole 31 described later formed in the pinhole plate 3 can be defined. The collar 4 is interposed between the pinhole plate 3 and the condenser lens 2, and the through holes 35 are fitted into the projections 56 of the pinhole plate mounting portion 55, respectively. The protrusions 56 are fixed by so-called heat staking which spreads by melting with heat.

The laser diode 1 preferably emits laser light having a wavelength of 800 nm or less, and in this embodiment, emits laser light having a wavelength of 655 nm.

As shown in FIG. 4, the light receiving module 200 includes, for example, a lens 202 for condensing the once diverged laser beam B3, and a light receiving element 201 provided at a converging portion of the condensed laser beam. And
As the light receiving element 201, for example, a photodiode or a phototransistor is used. Further, in order to detect the high-speed ink droplet D, the area of the light receiving element 201 of the light receiving module 200 needs to be reduced. This is because the larger the area of the light receiving element 201 is, the larger the capacitance is, and the lower the response is.

In this embodiment, the laser diode 1 has a stem 12 serving as a base thereof,
2 and a can seal portion 11 having a laser light emitting element therein, and leads 13... For electrically connecting the laser light emitting element protrude from the back surface of the stem 12. . As shown in FIG. 1, the can seal portion 11 is formed in a cylindrical shape, and the stem 12 is also formed in a cylindrical shape. The diameter of the stem 12 is larger than the diameter of the can seal portion 11. It is large and has a flange shape with respect to the can seal portion 11. The stem 12 has a plane perpendicular to the optical axis of the laser light emitted from the laser light emitting element, and this plane is brought into contact with the laser reference plane 53 a formed on the laser mounting part 53. Thereby, the optical axis of the laser light emitted from the laser diode 1 is
2 can be prevented from being inclined.

When the laser diode 1 is fixed, as shown in FIG.
Is inserted into the light guide path 52 so that the stem 1
2 is fitted to the laser mounting portion 53. At this time, since the outer diameter of the stem 12 is slightly smaller than the inner diameter of the laser mounting portion 53, the stem 12 surely comes into contact with the laser reference surface 53a of the laser mounting portion 53.
The mounting position and the mounting angle of the laser diode 1 can be defined.

The laser diode 1 is connected to the frame 5
After the wiring board 8 is mounted on the plate-shaped base 51 from the rear side, a circuit board is formed on the board base 51 in advance. At this time, as shown in FIG. The elastic sheet 7 formed of silicon rubber or the like and having holes through which the leads 13... Can be interposed to press the stem 12 against the laser reference surface 53a so that the position is not shifted. You can also.

Next, the wiring board 8 is screwed to the plate-like base 51 so as to press the elastic sheet 7.
Fix with such as. Also, by soldering these screws 81 to the wiring board 8, it is possible to prevent the elastic force of the elastic sheet 7 pressing the laser diode 1 from weakening.

Next, the leads 13 projecting through the through holes provided in the wiring board 8 are soldered 82
By doing so, the laser diode 1 is connected to the wiring board 8.
To be implemented.

The condensing lens 2 is a collimating lens for condensing the laser light emitted from the laser diode 1, and is disposed at the other end of the light guide path 52.
In the present embodiment, it is formed of a resin material having chemical resistance and having the same transmittance as acrylic. Thus, when the light emitting module A is used for detecting ink droplets in an ink jet printer, for example, even if minute ink droplets adhere to the condenser lens 2, the condenser lens 2 is not deformed or deteriorated. Can be prevented.

Further, as shown in FIG. 2, the condensing lens 2 may be an aspheric lens whose incident surface 2a, that is, the surface facing the laser diode 1 is a flat surface. Thus, by bringing the peripheral edge of the incident surface 2a into contact with the lens reference surface 54a of the lens mounting portion 54, the condenser lens 2 is positioned, and the central axis of the condenser lens 2 is adjusted to the laser light B0. Can be prevented from being inclined with respect to the optical axis. The condenser lens 2 has a lens reference surface 54a and the laser reference surface 5a.
Since the distance from the laser diode 3a is predetermined, the distance from the laser diode 1 is strictly defined. In addition, since the condensing lens 2 can be formed of resin as described above, the manufacturing cost can be suppressed despite the fact that it is an aspheric lens.

As shown in FIG. 2, the condenser lens 2 has a flange portion 22 formed around the lens portion 21 so that the collar 4 comes into contact with the flange portion 22. Can also. Also, this flange portion 22
It can also be used as a handling part when fitting the condenser lens 2 to the lens mounting part 54.

The outer shape of the condenser lens 2 including the flange portion 22 is equivalent to the shape of the lens mounting portion 54 (in this case, circular because the lens mounting portion 54 is cylindrical). Accordingly, it is possible to prevent the central axis from shifting due to parallel movement.

Incidentally, the outer shape of the condenser lens 2 and the lens mounting portion 54 can be formed in the same non-circular shape as shown in FIG. Since the position in the rotation direction about the optical axis of the beam is defined uniformly, even when distortion occurs when the condenser lens 2 is formed, the image formation state of the convergence point P varies from product to product. Can be prevented.

The collar 4 is a part for defining the distance between the condenser lens 2 and the pinhole 31. In this embodiment, the collar 4 is formed by forming a wire having a circular uniform cross section into a ring shape. The diameter of the ring is such that the collar 4 corresponds to the flange portion 22 of the condenser lens 2. By setting the diameter of the wire to a predetermined dimension, the collar 4 comes into contact with the condenser lens 2 and the pinhole 31 at a tangential line, and the predetermined interval therebetween can be strictly defined.

FIG. 3B shows the color 4.
As shown in FIG. 7, a part thereof is cut out, and the notch abutting ends 41... May be slightly shifted in the thickness direction of the collar 4 in a natural state.
When the collar 4 is interposed between the condensing lens 2 and the pinhole plate 3, the notch abutting end portions 41... This allows the collar 4 to have elasticity in the thickness direction. Due to this elastic force, the condenser lens 2 is pressed against the lens reference surface 54a, and the distance between the condenser lens 2 and the laser diode 1 can be more strictly defined.

The collar 4 is preferably made of phosphor bronze so as to have an elasticity that does not deform the pinhole plate 3.

The pinhole plate 3 is provided with the condenser lens 2.
The laser diode 1 is disposed close to and opposite to the laser diode 1, and in the present embodiment, is formed of stainless steel. This pinhole plate 3, as shown in FIG.
It is a plate-like body including a general portion 33 having a predetermined thickness, and a thin portion 32 formed by compressing a substantially central portion of the general portion 33 in the thickness direction. A pinhole 31 for narrowing the laser beam B1 condensed at the step is formed. This pinhole 31 is used for the pinhole plate 3
Is formed at a position corresponding to the optical axis of the laser beam B1 from the condenser lens 2 when is fixed.

In the pinhole plate 3, the general portion 33
By setting the thickness to a predetermined value, rigidity sufficient to press the condenser lens 2 against the lens reference surface 54a via the collar 4 can be provided to the entire pinhole plate 3. In the present embodiment, the diameter of the pinhole 31 is defined to be 0.56 mm ± 15 μm so that a desired narrow laser beam diameter can be obtained. Also,
Since the thin portion 32 in which the pinhole 31 is formed is compression-molded, the axial length of the pinhole 31 can be minimized, and unnecessary diffraction can be eliminated. Moreover, since the thin portion 32 can be easily formed by press working, the manufacturing cost can be reduced.

As shown in FIGS. 1 and 2, the pinhole plate 3 has a through hole 35 which penetrates the general portion 33 and is arranged at a position corresponding to the protrusion 56 of the frame 5. ... are formed. As described above, the pinhole plate mounting portion 5 is inserted into these through holes 35.
5 by fitting the protrusions 56, it is possible to define the position of the pinhole plate 3 in the rotational direction, and to define the position of the pinhole 31 formed in the pinhole plate 3. Therefore, the pinhole 31 is provided in the condenser lens 2.
Is accurately positioned so as to correspond to the optical axis.

The pinhole plate 3 is, as described above,
After the projections 56 are fitted into the through holes 35, the projections 56 are fixed to the opening edge on the other end side of the light guide path 52 by so-called heat staking which spreads the projections 56 by heat. . Since this fixing part is not fixed by adhesive etc., it does not distort at the time of curing,
The displacement of the pinhole 31 and the deformation of the pinhole plate 3 can be prevented. Further, when the issuing module A is used for detecting the ink droplets D in an ink jet printer, even if minute ink droplets adhere, the fixing portion is not deteriorated by a chemical change and the fixing force is not reduced. In addition, it is possible to prevent the pinhole plate 3 from falling off from the pinhole plate mounting portion 55.

Next, the condenser lens 2, the collar 4,
The method of attaching the pinhole plate 3 will be briefly described.

First, as shown in FIG. 2, the condensing lens 2 is set so that its incident surface 2a faces the laser diode 1, and the peripheral edge of the incident surface 2a is The light guide path 52 is mounted on the other end side so as to be in contact with the lens reference surface 54a. Incident surface 2
a and the lens reference surface 54a are flat surfaces, and since the lens reference surface 54a is perpendicular to the optical axis of the laser beam B0 emitted from the laser diode 1,
Is prevented from having its center axis inclined with respect to the optical axis of the laser beam B0. Further, since the lens reference surface 54a has a predetermined distance from the laser reference surface 54a, the distance between the condenser lens 2 and the laser diode 1 is strictly defined.

Next, the color 4 is transferred to the condenser lens 2.
Is arranged so as to contact the flange portion 22 of
The pinhole plate 3 is arranged so as to close the opening at the other end of the light guide path 52 so that the protrusions 56 of the pinhole plate mounting portion 55 are fitted into the through holes 35 of the pinhole plate 3. I do. At this time, the position of the pinhole 31 formed in the pinhole plate 3 is accurately defined by the fitting of the protrusions 56 and the through holes 35. It is possible to omit a separate operation corresponding to the above.

Then, the pinhole plate 3 is pressed so that the notched butting ends 41 of the collar 4 are pressed in the thickness direction of the collar 4 so as to be flush with each other. 56 are melted and spread by heat, that is, fixed by so-called heat staking. At this time, the distance between the pinhole plate 3 and the condenser lens 2 is strictly defined by the thickness (diameter in cross section) of the collar 4. In addition, color 4
Since an elastic force is generated in a direction for separating the pinhole plate 3 and the condenser lens from each other, the condenser lens 2
The lens reference surface 5 in which a peripheral portion of a is formed on the frame 5
4a. Thereby, the condenser lens 2
Not only is the distance from the laser diode 1 strictly defined, but its position is firmly fixed.

In this embodiment, the pinhole plate 3 is fixed by heat caulking the projections 56 formed on the pinhole plate mounting portion 55. It can also be fixed directly to the mounting portion 55 by thermocompression bonding or ultrasonic welding.
In this case, the protrusions 56 and the through holes 3 of the pinhole plate 3 are formed.
5 can be omitted, and the structure can be simplified. Further, similarly to the fixing method by heat caulking, even if minute ink droplets adhere to the fixed portion, it is possible to prevent the pinhole plate 3 from dropping or displacing.

Next, the operation of the laser sensor for detecting the ink droplets of the ink jet printer having the light receiving module having the above configuration will be briefly described.

As shown in FIG. 4, first, the laser beam B0 emitted from the laser diode 1 reaches the condenser lens 2 while diverging. At this time, the laser diode 1 and the condenser lens 2 are respectively connected to the stem 12 (see FIG. 2) of the laser diode 1 and the laser reference surface 53a of the laser mounting portion 53, and the incident surface 2a of the condenser lens 2. The distance between the lens mounting portion 54 and the lens reference surface 54a is strictly defined. Therefore, the laser beam B
0 reaches the condenser lens 2 while diverging at a predetermined angle.

Next, the laser beam B0 is applied to the condenser lens 2
The laser beam B1 condensed at the pinhole 31
Narrowed down by At this time, since the pinhole 31 is disposed at a position closer to the condenser lens 2 than the convergence point P when it is assumed that the pinhole 31 does not exist, the laser beam:
The narrow laser beam B2 focused by the pinhole 31
And is determined by the diffraction action. Therefore, the diameter of the laser beam B2 is maintained uniform over a relatively long range. At this time, a predetermined distance S is set between the condenser lens 2 and the pinhole 31 by the collar 4.
Since w is precisely defined, the laser beam B2 having a desired diameter can be maintained uniformly over a desired effective detection range L. The ink droplet D traverses the laser beam B2. As described above, since the laser beam B2 has a uniform small diameter over a relatively long effective detection range L, the ink droplet D drops. Even if the position shifts, it can cope.

Laser beam B3 passing through ink droplet D
Reach the light receiving module 200 in a state of being spread by the diverging action. This laser beam B3 is
By condensing at 02, a change in the amount of light when the ink droplet D traverses is detected by focusing on the light receiving element 201. Thus, the presence or absence of the ink droplets D and the number of the ink droplets D are detected. The light receiving element 201
Has a small area for accurate detection, but in the light emitting module A, since the optical axis of the laser beam B2 is prevented from being inclined, the laser beam 3 can be surely received by the light receiving element 201. Can be received.

Although the above-described light emitting module has been described as an example used for a laser sensor for detecting ink droplets of an ink jet printer, the present invention is not limited to this and can be used for various light emitting modules.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing an embodiment of a light emitting module according to the present invention.

FIG. 2 is a sectional view taken along the line II-II in FIG.

3A and 3B are enlarged views of the collar in FIG. 1, wherein FIG. 3A is a plan view and FIG. 3B is a front view.

FIG. 4 is a schematic diagram for explaining the operation of the light emitting module according to the present invention.

FIG. 5 is a schematic diagram showing an example of a laser sensor provided with a conventional light emitting module.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Laser diode 2 Condensing lens 3 Pinhole plate 4 Collar 31 Pinhole 32 Thin part 33 General part 41 Notch butting end part 50 Frame 52 Light guide path 54a Reference plane (lens reference plane) A light emitting module

Claims (12)

[Claims] A laser diode disposed at one end of a light guide path formed on a frame; and a laser beam disposed at the other end of the light guide path and condensing laser light emitted from the laser diode. A light-emitting module comprising: a condensing lens for forming a laser beam; and a pinhole plate for narrowing the laser beam, which is disposed close to the condensing lens on the side opposite to the laser diode. The condensing lens is brought into contact with a reference surface formed stepwise on the frame such that the peripheral portion on the incident surface side expands the other end of the light guide path, and the pinhole plate is The light guide path is fixed to the frame so as to close the other end side opening, and a collar for defining the distance between the condenser lens and the pinhole plate is provided between the condenser lens and the pinhole plate. Via Characterized in that it is, the light emitting module. 2. The collar has a ring shape formed of a wire having a uniform cross section, has a part cut out, and has a notch abutting end portion in a natural state in a thickness direction of the collar. The light emitting module according to claim 1, wherein the light emitting module is formed by slightly shifting the light emitting module. 3. The light emitting module according to claim 2, wherein the cross section is a circle. 4. The light emitting module according to claim 1, wherein said collar is formed of phosphor bronze. 5. The light emitting module according to claim 1, wherein said condenser lens is made of a resin material having chemical resistance and a transmittance equivalent to that of acrylic. 6. The light-emitting module according to claim 1, wherein said condensing lens is an aspheric lens having a plane incident surface. 7. The pinhole plate according to claim 1, wherein the pinhole plate includes a general portion having a predetermined thickness and a thin portion pressed in a thickness direction, and the pinhole is formed through the thin portion. The light emitting module according to any one of the above. 8. The light emitting module according to claim 1, wherein said pinhole plate is made of metal. 9. A laser diode disposed at one end of a light guide path formed in a frame, and a laser beam disposed at the other end of the light guide path and condensing laser light emitted from the laser diode. A method of assembling a light-emitting module comprising: a condenser lens for forming a laser beam; and a pinhole plate disposed on the opposite side of the condenser lens on the side opposite to the laser diode and for focusing the laser beam. Then, the condensing lens is incorporated at the other end of the light guide path such that the peripheral edge of the incident surface side abuts the reference surface formed stepwise so as to increase the diameter of the other end side of the light guide path. A step of arranging a collar for defining a distance between the condenser lens and the pinhole plate in contact with the condenser lens, and a step of closing the other end of the light guide path with the pin. Hall plate And a step of fixing the pinhole plate to a peripheral edge of the other end side opening of the light guide path while pressing the collar. 10. The step of fixing the pinhole plate,
The method for assembling a light emitting module according to claim 9, wherein the method is performed by thermocompression bonding the pinhole plate to the peripheral edge of the opening on the other end side of the light guide path. 11. The step of fixing the pinhole plate,
The method for assembling a light emitting module according to claim 9, wherein the method is performed by ultrasonically welding the pinhole plate to the peripheral portion of the opening on the other end side of the light guide path. 12. The step of disposing the pinhole plate,
A plurality of protrusions formed so as to protrude from the peripheral edge of the other end side opening of the light guide path in the direction in which the laser beam travels are fitted into through holes formed at positions corresponding to the protrusions of the pinhole plate. The method for assembling a light emitting module according to claim 9, wherein the step of fixing the pinhole plate is performed by melting and expanding the protrusion by heat.