JP3294972B2 - LED head and LED position adjustment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an LED head using an LED (light emitting diode) mounted on an electrophotographic printer or the like, and more particularly to a method for adjusting the position of an LED and a lens array in an LED head.

[0002]

2. Description of the Related Art Conventionally, an LED head used in an electrophotographic printer or the like has a lens array in which LEDs are arranged in a row on a substrate and opposed to this, for example, a number of refractive index distribution type lenses are arranged. We are trying to establish. The lenses have a columnar shape, and are arranged in two rows in a staggered manner. L
When assembling the ED head, it is necessary to match the arrangement position of the LEDs with the center line in the arrangement direction of the lens array within a certain allowable range. For this reason, conventionally, for example, a mounting portion serving as a reference position for mounting the lens array is provided, and is fixed with an adhesive.

[0003]

However, the conventional L
In the ED head, LE is set only by geometrical dimension setting.
Since D and the lens array are attached, the displacement between the LED arrangement position and the center line in the arrangement direction of the lens array may exceed the allowable range. When the arrangement position of the LED and the center line in the arrangement direction of the lens array are shifted, the shift increases the light amount unevenness of the lens.
The unevenness in the light amount of the head is increased, and the print results appear in shading. That is, there is a problem that the print quality is reduced.

[0004]

In order to solve the above problems, an LED head according to the present invention comprises a plurality of LEs opposed to a lens array in which refractive index distribution type lenses are arranged in a staggered manner.
In the LED head in which D is arranged in a line, the arrangement L
Move adjustment means for moving both ends of the arrayed LEDs in a direction orthogonal to the array direction so that the ED is located within a predetermined range in a direction orthogonal to the staggered array from the center line in the array direction of the lens array. It is characterized by having been provided.

Further, in the LED position adjusting method of the LED head according to the present invention, a plurality of LEDs are arranged in a line shape facing a lens array in which refractive index distribution type lenses are arranged in a staggered manner. What is claimed is: 1. An LED position adjusting method for an LED head, which adjusts a positional deviation between a center line of an array direction of a lens array and an arrayed LED in a direction orthogonal to the LED array, and moves both ends of the arrayed LED in a direction orthogonal to the array direction. means provided to the light emitting arrays LED, by measuring the amount of light passing through the lens array by the light quantity measuring means, arranged LED is given in a direction perpendicular to the staggered arrangement from the arrangement direction centerline of the lens array It is characterized in that the movement adjusting means is adjusted so as to be located within the range.

In addition to the light amount measuring means, the movement adjusting means may be adjusted by measuring the light intensity passing through the lens array by the light intensity measuring means.

[0007]

According to the present invention having the above structure, an arrayed LED is provided.
Moving adjustment means for moving both ends of the arrayed LEDs in a direction orthogonal to the array direction so that the lens is located within a predetermined range in a direction orthogonal to the staggered array from the center line in the array direction of the lens array. Accordingly, the arrayed LEDs can be positioned within a predetermined allowable range from the center line of the lens array in the direction orthogonal to the zigzag arrangement of the lens array. In addition, when performing position adjustment, the amount of light passing through the lens array by causing the LED to emit light is measured by a light amount measuring unit. By this measurement, the displacement between the LED and the lens array in the direction orthogonal to the zigzag arrangement of the lens array can be determined, and the movement adjusting means can be moved so that the displacement is minimized.

When the light intensity measuring means is used, the light intensity passing through the lens array is measured by the light intensity measuring means. By performing both the measurement and the measurement by the light amount measuring unit and moving the movement adjusting unit, it is possible to more accurately perform the position adjustment.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. Elements common to the drawings are assigned the same reference numerals. 1 and 2 are sectional views showing an LED head according to an embodiment of the present invention.

In both figures, a gradient index lens array 1 is supported by a lens holder 2. Lens holder 2
The lens array 1 is positioned by the positioning portion 2a and is fixedly adhered by an adhesive 3. A printed wiring board 4 is disposed below the lens array 1, and the printed wiring board 4 includes an LED array 5 and an LED array 5.
A driver 6 for driving the ED 5 is provided. LED
The array 5 is configured by linearly arranging a plurality of LEDs 5a as shown in FIG. The lens holder 2 and the substrate 4 are supported by a base 7. The substrate 4 is movable with respect to the base 7. Slots 8 are formed at both ends of the printed wiring board 4, and the projections 9 a, 10 a of the adjusting screws 9, 10 enter into the slots 8.

FIG. 3 is an enlarged view showing the adjusting screw, and FIG. 4 is a plan view showing the adjusting screw. As shown in both figures, the base 7
Is formed with a screw hole 11, into which the adjusting screw 9 is fitted. Projection 9 formed at the tip of adjustment screw 9
a is eccentric from the center of the adjusting screw 9. Therefore, by rotating the adjusting screw 9, the position of the protrusion 9a changes, and the printed wiring board 4 can be moved in the direction of the arrow in FIG. 4, that is, in the left and right direction in FIG.

FIG. 5 is a cutaway perspective view showing a position adjusting method according to the embodiment. In FIG. 1, a lens array 1 is provided with a plurality of gradient index lenses 1a in a two-row staggered pattern. Above the lens array 1, an image measurement camera 1
2 is installed. The image measurement camera 12 confirms the distribution of the amount of light passing through the lens array 1 by measuring the image when the LED array 5 emits light.

Next, a change in the distribution of the amount of light passing through the lens array 1 when the position of the LED array 5 deviates from the center line of the lens array 1 will be described. FIG. 6 is an explanatory diagram showing a light amount distribution at a correct position, and is an explanatory diagram showing a light amount distribution in a case where it deviates from FIG.

In FIG. 6, a constant dashed line indicated by A indicates a center line in the arrangement direction of the lens array 1, and LE
The D array 5 is arranged at a position (correct position) corresponding to the center line. In this case, the LED array 5
When the amount of light that passes through the lens array 1 is measured by emitting all the light, the amount of light shows a distribution changed at a pitch of D / 2 (D: lens diameter) as shown by a solid line. And the maximum value of the light quantity i
The difference between max and the minimum value imin is relatively small. Note that the distribution shown by the dotted line is a distribution shown when the corresponding lens 1a is used alone.

In FIG. 7, the LED array 5 is shifted from the center line A of the lens array 1 by Δy. If the lens diameter is about 0.9 mm, Δy is about 0.45 mm. In this case, the light amount distribution changes at the pitch of D, and the difference between the maximum value imax and the minimum value imin of the light amount becomes larger than that in the case of FIG. That is, when the LED array 5 is shifted from the center line A of the lens array 1 by Δy,
The deviation causes the density of the print density to be caused in the pitch unit of the lens 1a.

Then, while measuring the light quantity of the image when the LED array 5 emits light, the above-mentioned adjusting screws 8 and 9 are adjusted so that the LED array 5 and the lens array 1 have an appropriate positional relationship. The printed wiring board 5 is moved by turning the adjusting screws 8 and 9 so that the deviation amount Δy is | Δy | ≦
Adjust to a position that satisfies 0.2 mm. L at a position satisfying | Δy | ≦ 0.2 mm from the center line A of the lens array 1
If the ED array 5 is located, good print quality can be maintained.

In this embodiment, the distance between the camera 12 and the emission end face 1b (shown in FIG. 5) of the lens array 1 is
The distance is equal to the distance between the LED array 5 and the incident end face 1c (FIG. 5) of the lens array 1, and is set to the optimum focus position.

Usually, when the pitch of the amount of light passing through the lens array 1 is D / 2, the LED array 5 is at the optimum position. However, the tolerance of the lens 1a (for example, the tolerance of the lens diameter or the lens pitch). ), The pitch of the minimum light amount may be larger than D / 2. In such a case, the adjusting screws 8 and 9 are used to adjust the LED so that the light amount pitch changes from about D pitch to about D / 2 pitch.
The array 5 is moved, and stopped at the position of the LED array 5 during which the pitch of the light amount is minimized. In this case, the minimum pitch of the light amount is not necessarily about D / 2 pitch, but can be set to an optimum position in terms of print quality. That is, even when the lens 1a of the lens array 1 has a tolerance, the position of the LED array 5 can be set to an optimum position.

Next, another embodiment will be described. In another embodiment, a light intensity distribution measuring function is added to the above-described embodiment, and the position of the LED array is adjusted by measuring the light intensity distribution. Here, an MTF (Modulation Transfer Function: response function) is calculated from the light intensity distribution. FIG. 8 is an explanatory diagram showing a light intensity distribution. In the figure, assuming that MAX is the maximum value of the light intensity and MIN is the minimum value of the light intensity, the MTF is expressed by the following equation.

MTF = {(MAX−MIN) / (MAX + MIN)}
× 100 (%) The MTF is greatly influenced by the positional relationship between the LED array and the center line of the lens array, like the light amount. LE
If the position of the D array matches the position of the center line of the lens array, the light intensity distribution shows a sharp change as shown by the solid line in the figure, and the MTF increases. When the position of the LED array and the position of the center line of the lens array are shifted, the light intensity distribution becomes dull as indicated by the dotted line, and the MTF becomes smaller. When the displacement of the LED array is large, the unevenness of the light amount of the lens array 1 itself becomes large, and the MTF unevenness becomes large. Here, the light amount unevenness ΔE is expressed by the following equation.

ΔE = {(imax−imin) / iAVE} × 100 (%) Here, iAVE indicates an average of light amount values. MTF unevenness Δ
ε is represented by the following equation. Δε = ｛(εmax−εmin) / εAVE｝ × 100 (%) where εmax is the maximum value of MTF, εmin is the minimum value of MTF, and εAVE is the average value of MTF.

FIGS. 9, 10 and 11 are explanatory diagrams showing respective distributions of light quantity and MTF. FIG. 9 shows a case where the position of the LED array coincides with the position of the center line of the lens array, and a case where the distribution of the light amount and the MTF coincide at a D / 2 pitch. FIG. 10 shows a case where the position of the LED array is shifted from the center line of the lens array by Δy (about 0.45 mm) shown in FIG. 7, and a case where the distribution of the light quantity and the MTF coincide with each other at the D pitch. . FIG. 11 shows a case where the pitch of the light amount and the pitch of the MTF do not match.

When the pitches of the light quantity and the MTF distribution match each other as shown in FIGS.
Although the position adjustment of the array 5 can be performed only by measuring the light amount value as described in the above embodiment, if the pitch of the light amount and the pitch of the MTF do not match as shown in FIG. The position adjustment of the LED array 5 cannot be performed only by measurement. Possible causes of the mismatch between the light amount and the pitch of the MTF include the influence of the tolerance of the lens 1a of the lens array 1 and the influence of the assembly tolerance that does not occur from the geometric dimensions.

Since the influence of MTF unevenness is greater than that of light amount unevenness for determining the final print quality, FIG.
In such a case, the position of the LED array 5 is adjusted in the following procedure. First, the pitch of the light intensity is determined by measuring the light intensity value.
The position of the LED array 5 is adjusted so as to satisfy Δy | ≦ 0.2 mm. This adjustment is performed by rotating the adjustment screws 8 and 9 as in the above-described embodiment. Next, the pitch of the light amount is | Δy |
The light intensity distribution is measured within a range of 0.2 mm. This measurement is performed by the camera 12 shown in FIG. Then, the position of the LED array 5 is adjusted by the adjusting screws 8 and 9 so that the MTF pitch is minimized at about D / 2 pitch. Thus, the position of the LED array 5 with respect to the lens array 1 is set at a position where the best print quality is obtained.

As described above, according to the other embodiment, since the LED array is adjusted by the light intensity distribution measurement after the adjustment by the light intensity value measurement, not only the light intensity unevenness but also the MTF unevenness can be minimized. There is an effect that higher quality printing with excellent resolution and no density unevenness can be realized.

[0026]

As described above in detail, according to the present invention, the arrayed LEDs are arranged so as to be located within a predetermined range in the direction orthogonal to the staggered array from the center line in the array direction of the lens array. Is provided with a movement adjusting means for moving both ends of the lens array in a direction perpendicular to the arrangement direction, so that the array LEDs can be allowed from the center line of the lens array in the direction orthogonal to the staggered arrangement of the lens array. It can be located within the range. Therefore, it is possible to adjust the position of the array LEDs in a direction orthogonal to the staggered array with respect to the center line in the array direction of the lens array.
The position of the ED can be held accurately, and good print quality can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an LED head according to an embodiment.

FIG. 2 is a cross-sectional view illustrating an LED head according to an embodiment.

FIG. 3 is an enlarged view showing an adjusting screw.

FIG. 4 is a plan view showing an adjusting screw.

FIG. 5 is a cutaway perspective view showing a position adjusting method according to the embodiment.

FIG. 6 is an explanatory diagram showing a light amount distribution at a correct position.

FIG. 7 is an explanatory diagram showing a light amount distribution in the case of displacement.

FIG. 8 is an explanatory diagram showing a light intensity distribution.

FIG. 9 is an explanatory diagram showing a distribution of light amount and MTF.

FIG. 10 is an explanatory diagram showing a distribution of light amount and MTF.

FIG. 11 is an explanatory diagram showing a distribution of light amount and MTF.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Lens array 4 Printed wiring board 5 LED array 9, 10 Adjustment screw 12 Image measurement camera

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Minoru Teshima 4-11-22 Shibaura, Minato-ku, Tokyo Oki Data Co., Ltd. (56) References JP-A-4-93933 (JP, A) JP-A-5 −8442 (JP, A) JP-A-63-312171 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B41J 2/44 B41J 2/45 B41J 2/455

Claims (3)

(57) [Claims] 1. A LED head and the lens of the refractive index distribution type opposite to the lens array arranged in staggered arranging a plurality of LED in a line, said sequence LED from the array direction centerline of the lens array to lie within a predetermined range in the direction perpendicular to the staggered arrangement, LED head is characterized in that a movement adjustment means for moving the both end portions of the array LED in the direction orthogonal to the array direction. 2. A plurality of LEDs are arranged in a line in opposition to a lens array in which refractive index distribution type lenses are arranged in a staggered manner, and a center line in the arrangement direction of the lens array in a direction orthogonal to the staggered arrangement. An LED position adjustment method for an LED head that adjusts a positional deviation between the array LED and the array LED, comprising: a movement adjusting unit that moves both end portions of the array LED in a direction orthogonal to the array direction. , by measuring the amount of light passing through the lens array by the light amount measuring means, wherein said sequence LED from the array direction centerline of the lens array
An LED position adjusting method for an LED head, comprising: adjusting the movement adjusting means so as to be located within a predetermined range in a direction orthogonal to the staggered arrangement . 3. A plurality of LEDs are arranged in a line shape facing a lens array in which refractive index distribution type lenses are arranged in a staggered manner, and a center line in the arrangement direction of the lens array in a direction orthogonal to the staggered arrangement. An LED position adjustment method for an LED head that adjusts a positional deviation between the array LED and the array LED, comprising: a movement adjusting unit that moves both end portions of the array LED in a direction orthogonal to the array direction. By measuring the amount of light passing through the lens array by the light amount measuring means and measuring the light intensity passing through the lens array by the light intensity measuring means, the arrayed LEDs are staggered from the center line in the arrangement direction of the lens array. In the direction orthogonal to the array
Kicking LED position adjustment method of the LED head and adjusts the movement adjustment means to lie within a predetermined range.