JPH04336559A - Imaging element and optical print head - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

TECHNICAL FIELD The present invention relates to an imaging element and an optical print head, and more particularly, the present invention relates to a roof mirror lens array (hereinafter referred to as RMLA) as a 1-magnification imaging element used in copying machines, facsimile machines, printers, etc. , and a fixed scanning optical print head such as an LED array printer or a liquid crystal shutter array printer using an arrayed light source and RMLA.

0002

[Prior Art] Currently, solid-state scanning optical printheads that combine an arrayed light source and SLA (Selfox Lens Array) as a 1-magnification imaging element are used as optical writing heads for LED array printers, liquid crystal shutter array printers, etc. It has been put into practical use (commercialized). On the other hand, RMLA, which is also a same-magnification imaging element, is being put into practical use as an imaging element for reading scanners and the like. For example, JP-A-2-
The "imaging element" described in Publication No. 195337 is
In the through hole parallel to the optical axis formed in a pair of lens arrays,
By inserting a protrusion formed on the diaphragm plate, a pair of lens arrays can be easily arranged symmetrically with high precision. In addition, the "imaging element and image reading device" described in Japanese Patent Application Laid-Open No. 2-195321 reflects a light beam from an object surface toward a roof mirror, and also reflects the light beam twice from the roof mirror and returns it. An optical path separation mirror that reflects a light beam toward an image plane is provided, and a pair of lenses manufactured under the same conditions is disposed between the optical path separation mirror and the roof mirror, and the pair of lenses is aligned with the ridgeline of the roof mirror. They are arranged symmetrically with an axis perpendicular to the optical axis serving as an axis of rotational symmetry.

Optical printheads have also been developed that combine RMLAs with arrayed light sources such as LED arrays and "fluorescent tubes." For example, the "recording apparatus" described in Japanese Patent Application Laid-Open No. 58-223242 includes a recording medium, a scanning recording element that forms a light emitting pattern in the main scanning direction to record an information image on the recording medium, It is equipped with an imaging element that forms an image of the emitted light pattern as imaging light onto a recording medium. Furthermore, the "solid-state scanning optical head" described in Japanese Patent Application Laid-Open No. 2-111571 corrects periodic light intensity unevenness in the array direction due to the arrangement pitch of the imaging elements of the imaging element array. . Also, Utility Model Hei 1-169
"Self-scanning exposure device" described in Publication No. 257
The photoreceptor is exposed to light beams emitted from a large number of light emitting segments arranged in an array in the main scanning direction through a slit formed in a light shielding member for preventing flare.

As detailed in the above-mentioned publication, a "fluorescent tube" is an arrayed light source in which minute phosphor dots as light emitting segments are arranged in an array. The phosphor dots are formed by an appropriate method such as electrodeposition on a large number of strip-shaped segment electrodes (anodes) arranged in rows on a glass substrate. The pitch (P) of each phosphor dot in the array direction corresponds to the writing density, and is set to P~85 μm at 300 dpi, for example. Further, the size (Dx) of the phosphor dots in the array direction is Dx=0.6~
It is estimated to be about 0.9P. In other words, when the phosphor dots are arranged in the simplest one-row structure, in principle Dx≧
P, and a gap is required between each segment to maintain electrical independence (insulation). On the other hand, if the gap is too large, the area of the phosphor dots becomes small, which is disadvantageous in terms of light quantity. Note that the size (Dy) of the phosphor dots in the direction perpendicular to the array direction is usually set to be approximately equal to or slightly smaller than Dx.

Similarly, in other arrayed light sources such as LED arrays and liquid crystal shutter arrays, the relationship between the size (Dx) of the light emitting segments in the array direction and the pitch (P) of the light emitting segments is usually at least Dx <P, specifically, Dx=0.4 to 0.9P (Figure 10
(a)). As mentioned above, in an arrayed light source in which light-emitting segments are arranged in an array, the size of each light-emitting segment in the array direction is smaller than the pitch of the light-emitting segments. Periodic light emission intensity unevenness occurs according to the pitch of (FIG. 10(b)). Therefore, when the light generated from the arrayed light source is imaged on the image carrier by the same-magnification imaging element, unevenness in the amount of light occurs with the same period (FIG. 10(c)).

FIGS. 11, 12, and 13 show conventional RMLA
The basic configuration is shown below. 11 is a perspective view, FIG. 12 is a Y-Z sectional view, and FIG. 13 is an X-Z sectional view (X: array direction, Y, Z
(as shown in FIG. 11). In the figure, 31 is the object plane;
32 is an optical path separation mirror (provided if necessary), 33 is a light beam, 34 is a lens array, 35 is an individual lens, 36
3 is a roof mirror array, 37 is a roof mirror, 38 is a reflective surface, and 39 is an image surface. Note that in FIG. 13, the optical path separation mirror is omitted for convenience.

The roof mirror array 36 has a roof-shaped reflective surface Hi (i=
1,...,n; n is the number of lenses in the lens array) are formed in an array, and each roof-shaped reflective surface (roof mirror) Hi (i=1,...,n) is Two reflecting surfaces Fi and Gi (i=1,...,n) are formed facing each other at a right angle (θi=90°, i=1,...,n). Naturally, as shown in FIG. 13, the angles formed by the adjacent roof-shaped reflecting surfaces Fi-1, Gi (i=2,...,n) are also right angles, that is, θ'i=90°, i=2,... , n.

Light from a point P on the object plane 31 is reflected by the upper reflective surface 38 of the optical path separation mirror 32, passes through the lens array 34, and enters the roof-shaped reflective surface Hi of the roof mirror array 36. By being reflected once each on the two reflective surfaces Fi and Gi, the X-Z cross section (Fig. 13
), the light rays are made into parallel and opposite directions to the roof-shaped reflecting surface Hi, pass through the lens array 34 again, and are reflected by the lower reflecting surface 38 of the optical path splitting mirror 32. An image is formed on a point Q that is conjugate with the point P on the image plane 39. That is, RMLA is roof mirror array 36
It constitutes a reflexive optical system with symmetrical reflection surface.

[0009]

[Purpose] The present invention has been made in view of the above-mentioned circumstances, and is aimed at correcting periodic light intensity unevenness according to the pitch of light emitting segments when combined with an arrayed light source in which light emitting segments are arranged in an array. The object of this invention is to provide an optical print head that includes an imaging element, the arrayed light source, and the imaging element, and in which the periodic unevenness in light amount is corrected.

0010

[Structure] In order to achieve the above objects, the present invention provides (1)
In an imaging element having a lens array in which a large number of lenses are continuously formed in a linear shape, and a roof mirror array having a roof-shaped reflective surface disposed opposite to each lens constituting the lens array, the roof (2) The perpendicularity of each roof-shaped reflective surface of the mirror array is set to be shifted by a predetermined minute amount, or (2) an arrayed light source in which light-emitting segments are arranged in an array and a large number of lenses are arranged in a straight line. an optical print head comprising a lens array formed by a lens array, and an imaging element having a roof mirror array having a roof-shaped reflective surface disposed opposite to each lens constituting the lens array; The present invention is characterized in that the perpendicularity of each roof-shaped reflective surface of the roof mirror array is set to be shifted by a predetermined minute amount so as to correct periodic light intensity unevenness according to the arrangement pitch of the light emitting segments. Hereinafter, the present invention will be explained based on examples.

FIGS. 1(a) and 1(b) are configuration diagrams for explaining an embodiment of an imaging element according to the present invention. In the figures, 1 is an object plane, 2 is an image plane, and 3 is a lens array. , 4 is a roof mirror array. First, the angle formed by the two opposing reflective surfaces Fi, Gi (i=1,...,n) forming the roof-shaped reflective surface (roof mirror) Hi (i=1,...,n) is determined from the right angle. The effect when set by shifting by a predetermined minute amount Δθ will be explained in detail.

θi=90°+Δθ, θ′i=90°−Δθ(i=
1,...,n)...(1), as shown in FIG. 1, light emitted from point P, passed through lens array 3, and entered roof-shaped reflective surface Hi of roof mirror array 4 is reflected once each by the two reflective surfaces Fi and Gi, so that when it is incident on the X-Z cross section,
The light beam is shifted from parallel by Δθ (indicated by a broken line in the figure), and heads toward the lens array 3 again. At this time, the direction in which the light ray first enters Fi out of the two reflective surfaces and the light ray that first enters Gi is shifted from parallel, so the angle of the light ray heading toward the lens array 3 is different. The two differ by 4·Δθ. Therefore, when the light passes through the lens array 3 again and forms an image on the image plane, the positions of the two image forming points Q1 and Q2 will be shifted by Δd in the X direction (array direction).

The relationship between Δθ and Δd is determined by the focal length f of the lens array, the distance between the lens array and the roof mirror array 4, etc., but if Δθ is sufficiently small, approximately Δd~4·|Δθ|[radians ]・f or
Δd [μm] ~ 1.2・|
Δθ|[min]·f[mm] (2). For example, when f=10 [mm], the amount of deviation (Δθ) of the imaging point corresponding to the amount of deviation (Δθ) of 1 minute from the perpendicularity of the roof mirror
d) is approximately 12 μm. In this way, by shifting the perpendicularity of the roof mirror by Δθ, the image formation on the image plane can be made into a superimposed state of double images separated by Δd according to equation (2) in the array direction.

Note that the sign of Δθ can be either + or -, but it may be set to either one. In addition, although it is depicted in FIG. 1 as if only the i-th lens array and roof mirror contribute to image formation, in reality, multiple (2 to 3) lens arrays and roof mirrors contribute to image formation. Therefore, the image intensities at the two imaging points Q1 and Q2 of the point P are almost equal regardless of the position of the point P on the object plane in the X direction. Furthermore, even if the perpendicularity of the roof mirror shifts by a minute amount, it hardly affects the image formation state in the YZ cross section. That is, the imaging performance in the sub-scanning direction does not deteriorate. Further, an optical path separation mirror is provided as necessary.

Consider now the case where the light generated from the arrayed light source is imaged on the image plane (on the image carrier) by the above-mentioned imaging element. When Δd=0, as shown in FIG. 2(a), the light amount distribution in the array direction on the image carrier when one of the light emitting segments emits light is approximated by a Gaussian distribution, and the beam diameter w at this time is (defined by the cross-sectional shape at a position 1/e2 with respect to the peak of the intensity distribution having a Gaussian distribution) is shown in Fig. 2 (b) when w = P.
), when all the light-emitting segments (or several or more adjacent light-emitting segments) emit light, the light amount distribution on the image plane causes large light amount unevenness as shown in the figure. At this time, the light amount unevenness S is defined as the maximum value Ima of the light amount I.
x and the minimum value Imin, S≡1-Imin/Imax...(3) Furthermore, if the uniformity R of the light amount is defined as R≡Imin/Imax...(4), then S=0.73, R=0. It will be 27.

On the other hand, when the perpendicularity of the roof mirror is shifted by a predetermined minute amount Δθ according to equation (2) to set Δd=0.5P, and other configurations such as the lens array are the same, as shown in FIG. 3(a).
As shown in , the light amount distribution in the array direction on the image carrier when one of the light-emitting segments emits light is two Gaussian distributions separated in the array direction by Δd=0.5P corresponding to the double image. (respectively, w = P, indicated by the dotted line in the figure) (indicated by the solid line in the figure)
. Furthermore, as shown in Figure 3(b), when all the light-emitting segments (or several or more adjacent light-emitting segments) are emitted, the light intensity distribution on the image plane is extremely large as shown in the figure. It is uniform. At this time, S=
0.03, R=0.97, and the effect is clear. Here, only the case where w=P and Δd=0.05P was described, but in the following examples, the beam diameter w is
The effects when =0.6P, 0.8P, P, and 1.2P are shown.

Embodiment 1 will be explained based on FIGS. 4(a) and 4(b). Beam diameter: When w=1.2P, (Δd=0.2P~0.
6P, Δd=0 is for comparison) Figure (a) shows the light amount distribution in the array direction on the image plane when all the light emitting segments (or several or more mutually adjacent light emitting segments) are emitted. Figure (b) shows the light amount distribution in the array direction on the image plane when every other light emitting segment is made to emit light. Example 2 will be described based on FIGS. 5(a) and 5(b). Beam diameter: When w=P, (Δd=0.2P~0.6P,
(Δd=0 is for comparison) Figure (a) shows the light amount distribution in the array direction on the image plane when all the light emitting segments (or several or more mutually adjacent light emitting segments) are emitted. Figure (b) shows the light amount distribution in the array direction on the image plane when every other light emitting segment is made to emit light.

Embodiment 3 will be explained based on FIGS. 6(a) and 6(b). Beam diameter: When w=0.8P, (Δd=0.2P~0.
5P, Δd=0 is for comparison) Figure (a) shows the light amount distribution in the array direction on the image plane when all the light emitting segments (or several or more mutually adjacent light emitting segments) are emitted. Figure (b) shows the light amount distribution in the array direction on the image plane when every other light emitting segment is made to emit light. Example 4 will be described based on FIGS. 7(a) and 7(b). Beam diameter: When w=0.6P, (Δd=0.2P~0.
5P, Δd=0 is for comparison) Figure (a) shows the light amount distribution in the array direction on the image plane when all the light emitting segments (or several or more mutually adjacent light emitting segments) are emitted. Figure (b) shows the light amount distribution in the array direction on the image plane when every other light emitting segment is made to emit light.

The results of Examples 1 to 4 described above are shown in FIG. 8 (relationship between uniformity R of light amount and Δd/P). From the diagram (a) of each example and FIG. 8, at least 0.3P≦Δd
The effect at ≦0.5P is obvious, and 0<Δd<0
．． The unevenness of light amount can be corrected within the range of 6P. That is, in accordance with these values, an appropriate value of Δθ may be set using equation (2). Incidentally, the unevenness in light amount caused by image separation is noticeable only when w = 0.6P and Δd≧0.5P, but
There are no other problems. Further, in each example, when every other dot is emitted, the contrast is sufficiently ensured, and therefore, the necessary resolution is maintained.

FIG. 9 is a diagram showing a specific example of the structure of the optical print head of the present invention. In the figure, 11 is a fluorescent tube substrate, 12 is an image carrier, 13 is an optical print head, 14 is a fluorescent tube as an arrayed light source, 15 is a roof mirror lens array, and 15a is a roof mirror array, as described above. is set to . 15b is a lens array, 16 is a housing, 17 is a hole, 18 is an elastic member, 19 is a screw, 20 is a support plate, 21 is a mirror, 22 is a slit, 23
24 is a presser plate, 24 is a phosphor dot as a light emitting segment, and 25 is a face glass.

A fluorescent tube 14 is disposed on the support plate 20 of the optical writing head 13 via an elastic member 18 as necessary, and the support plate 20 is given a predetermined rigidity and the fluorescent tube 14 is The tube 14 is held by screws 19 so that the substrate 11 is sandwiched between the support plate 20 and the housing 16. A hole 17 is formed in the housing 16, and the light emitted from the phosphor 24 of the fluorescent tube 14 and transmitted through the face glass 25 is emitted upward through the hole 17, and is deflected by about 90 degrees by the mirror 21. It is reflected at an angle of , and enters the roof mirror lens array 15 . The light reflected and converged by the roof mirror lens array 15 passes through the transparent portion below the mirror 21 and is further irradiated onto the image carrier 12 through a slit 22 for preventing flare.

[0022]

[Effects] As is clear from the above description, the present invention has the following effects. (1) Effects on claim 1: A lens array in which a large number of lenses are continuously formed in a straight line, and a roof mirror array having a roof-shaped reflective surface arranged opposite to each lens constituting the lens array. In the imaging element having the above-mentioned roof mirror array, the perpendicularity of each roof-shaped reflecting surface of the roof mirror array is set to be shifted by a predetermined minute amount, so that the image formation on the image plane is caused by the superposition of double images separated by a minute amount in the array direction. It can be in a combined state. Therefore, when this imaging element is combined with an arrayed light source in which light emitting segments are arranged in an array, it is possible to correct periodic light intensity unevenness according to the pitch of the light emitting segments. (2) Effect on claim 2: an arrayed light source in which light emitting segments are arranged in an array, a lens array in which a large number of lenses are successively formed in a straight line, and a light source facing each lens constituting the lens array. In an optical print head comprising a roof mirror array having a roof-shaped reflective surface arranged and an imaging element having a roof-shaped reflective surface, the perpendicularity of each of the roof-shaped reflective surfaces of the roof mirror array is set to be shifted by a predetermined minute amount. Therefore, the imaging state of each light emitting segment on the image plane can be made into a superposition of two light beams separated by a predetermined minute distance in the array direction, and the arrayed light source can be formed while maintaining the necessary resolution. It is possible to realize an optical print head in which periodic light intensity unevenness according to the arrangement pitch of the light emitting segments is well corrected.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram for explaining one embodiment of an imaging element according to the present invention.

FIG. 2 is a diagram showing how light generated from an arrayed light source is imaged on an image plane by an imaging element.

FIG. 3 is a diagram showing the situation when the perpendicularity of the roof mirror is shifted by a predetermined minute amount.

FIG. 4 is a diagram for explaining Example 1.

FIG. 5 is a diagram for explaining Example 2.

FIG. 6 is a diagram for explaining Example 3.

FIG. 7 is a diagram for explaining Example 4.

FIG. 8 is a diagram showing the uniformity of light amount with respect to minute deviations in Examples 1 to 4.

FIG. 9 is a configuration diagram of an optical print head.

FIG. 10 is a diagram showing the pitch of light emitting segments, unevenness in light emission intensity, and unevenness in light amount.

FIG. 11 is a perspective view showing the configuration of a conventional RMLA.

FIG. 12 is a YZ cross-sectional view of FIG. 11.

FIG. 13 is a cross-sectional view taken along the X-Z line in FIG. 11.

[Explanation of symbols]

1... Object plane, 2... Image plane, 3... Lens array, 4... Roof mirror array.

Claims (2)

[Claims] 1. An imaging element comprising a lens array in which a large number of lenses are consecutively formed in a straight line, and a roof mirror array having a roof-shaped reflective surface arranged opposite to each lens constituting the lens array. An imaging element characterized in that the perpendicularity of each roof-shaped reflective surface of the roof mirror array is set to be shifted by a predetermined minute amount. 2. An arrayed light source in which light emitting segments are arranged in an array, a lens array in which a large number of lenses are continuously formed in a straight line, and a roof placed opposite to each lens constituting the lens array. In an optical print head comprising a roof mirror array having a patterned reflective surface and an imaging element having a shaped reflective surface, the roof mirror array is configured to correct periodic light intensity unevenness according to the arrangement pitch of the light emitting segments of the arrayed light source. An optical print head characterized in that the perpendicularity of each roof-shaped reflective surface is shifted by a predetermined minute amount.