JP5057836B2 - Manufacturing method of rod lens array - Google Patents

Description

  The present invention relates to an optical printer using, for example, an LED (light emitting diode), an OLED (organic light emitting diode), or the like that emits light from a plurality of light emitting elements and forms an image of the element on a photosensitive surface as a recording medium with high accuracy. The present invention relates to a method of manufacturing a rod lens array used as an imaging element in a head, and an optical printer head and an image forming apparatus having the rod lens array.

  2. Description of the Related Art Conventionally, a lens array is known as an erecting equal-magnification long imaging element array used in an LED printer or the like. Among such lens arrays, rod lens arrays are particularly widely used. Here, the rod lens array is one in which a plurality of rod lenses having a refractive index distribution in the radial direction are periodically arranged in a predetermined direction.

  FIG. 1 shows a rod lens array as described above. The rod lens is usually formed by giving ion exchange to a rod-shaped glass to have a refractive index distribution. Such a plurality of rod lenses are arranged in one or two stages in the vertical direction (hereinafter referred to as sub-scanning direction) in FIG. 1 and in the left-right direction (hereinafter referred to as main scanning direction) in FIG. ing. Each of these rod lenses has a function of forming an erecting equal-magnification image of an object at a position separated by a predetermined distance.

  The plurality of rod lenses are arranged with high density, and these are sandwiched between a pair of side plates. Further, an opaque resin is filled between the rod lenses. As a result, a rod lens array is manufactured.

  As shown in FIG. 2, an optical printer head is constituted by the rod lens array and the light emitting means, and the light emitting means (light emitting element array) composed of a plurality of light emitting elements emits light according to an image signal and emits a plurality of light beams. . These light beams are imaged by the rod lens array on the same point (imaging spot) on the surface of the photoconductor as a recording medium arranged on the opposite side of the light emitting means at an erecting equal magnification. Thus, for example, a latent image can be formed on the surface of the photoconductor of the optical printer. In such a rod lens array, since a large number of rod lenses are arranged, there has been a problem that the lens arrangement is often disturbed during the manufacturing process. The imaging point on the body was said to be almost undisturbed.

  On the other hand, in recent years, the accuracy of printers has increased, and high-resolution printers such as 600 dpi and 1200 dpi have come out. In order to improve the image quality of such a printer, means for electrically correcting the light quantity variation of the light emitting elements has begun to be introduced. This is because a plurality of light-emitting elements used in an optical printer head are not uniform in light-emitting characteristics, so that the amount of light emission is different for each light-emitting element, and density unevenness is considered to occur on the output image. is there.

  However, in the printer as described above, although the light amount correction is performed with high accuracy, density unevenness occurs on the output image, so that the image quality management cannot be performed accurately. The inventor considered that this density unevenness is not a problem due to the amount of light emission but an imaging performance problem caused by an arrangement error of the rod lens array used in the printer.

  For example, if there is a tilted part in the arrangement of rod lenses, the light beam will not be collected on a single point on the surface of the photoconductor, resulting in variations in the imaging spot. Not removed.

  The density unevenness referred to here refers to a strip-shaped density unevenness that is locally whitened or crushed black on the output image, and is hereinafter referred to as obi unevenness.

  On the other hand, the characteristic determination of the rod lens array by MTF has been established as a known technique, and according to Japanese Patent Laid-Open No. 2003-114305 and Japanese Patent Laid-Open No. 2002-27197, Although it is described that the Obimura can be suppressed by managing the maximum value and the minimum value of the MTF, as shown in FIG. 4, the present inventor cannot accurately manage the Obimura on the image by extracting the Obimura element by the MTF. Is experimentally obtained from the relationship between the rod lens array based on printing and the optical printer head.

MTF The (M odulation T ransfer F unciton) , the quality of the image, that is an index representing the resolution, which receives the image of the rectangular wave grating pattern in slit scan or a CCD sensor,, SLA response function from the light level This is a method for calculating MTF.

ＭＴＦが高い、つまり１００％に近い程、原画に忠実な像が形成されていることになる。

As the MTF is higher, that is, closer to 100%, an image faithful to the original image is formed.

  In addition, image quality evaluation as an optical printer head is performed by combining a light emitting element array, a rod lens array, and a photoconductor to assemble an apparatus, and then actually operating the apparatus to perform a photosensitive and developing process. Was evaluated. Therefore, whether or not there is ambiguity caused by the rod lens array can only be grasped after the assembly of the device, and if it is determined that the rod lens array is defective, the assembly of the device is performed using a non-defective product of the array. You need to do it again. For this reason, it takes a lot of time and labor to obtain one good product, which reduces the productivity of the device.

  The present invention focuses on such conventional problems, and an object of the present invention is to provide a rod lens array capable of obtaining a good image quality free from obi unevenness, an optical printer head using the same, and an image forming apparatus. .

Another object of the present invention is to provide a method of manufacturing a rod lens array that can evaluate obi unevenness caused by the rod lens array before assembling the apparatus and improve productivity.
JP 2003-114305 A JP 2002-27197 A

The rod lens array manufacturing method of the present invention is a rod lens array manufacturing method for forming an image of light emitted from a light source means having a light emitting element on a recording medium. The rod lens array is manufactured through the following steps (1) to (5). A lens array is manufactured. (1) Using a lens measuring device having a light source means and an imaging device positioned in pairs via the rod lens array, the three-dimensional intensity distribution of light from the light source means transmitted through the rod lens array is different. Measurement is sequentially performed at N (N is a natural number) optical imaging positions. (2) The cross-sectional area of the three-dimensional intensity distribution is obtained with a predetermined intensity threshold at each of the light imaging positions. (3) A cross-sectional area of the three-dimensional intensity distribution is calculated for each of the optical imaging positions and a group consisting of the optical imaging positions included in a section of 1.5 to 15.7 mm centering on the optical imaging position. A moving average value is calculated, and this is set as an ideal cross-sectional area P (k) (1 ≦ k ≦ N) (k is a natural number) . (4) The N light imaging positions are divided into M sections (M is a natural number) such that the section length is in a range of 0.51 to 1.89 mm, and the three-dimensional intensity distribution is divided in each section. The average cross-sectional area is calculated, and this is defined as the section cross-sectional area Q (l) (1 ≦ l ≦ M) (l is a natural number) . However, the section length of the M sections is shorter than the section length for calculating the moving average value in (3). (5) For each optical imaging position, R (k) = [Q (
l) -P (k)] / P (k) is calculated, and a rod lens array in which the value of R (k) is within a predetermined range is determined as a non-defective product. However, Q (l) is a section sectional area of a section to which the kth optical imaging position having the ideal sectional area P (k) belongs.

  According to the present invention, the Obimura element of each rod lens array can be extracted with high accuracy, and the productivity of the rod lens array can be improved.

  Further, according to the present invention, it is possible to provide an image forming apparatus free from ambiguity caused by the rod lens array by using the discriminated rod lens array in the optical printer head.

  Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a perspective view of an erecting equal-magnification imaging element array (rod lens array) used for an optical printer head, and FIG. 2 is an exploded perspective view of an optical printer head L according to an embodiment of the present invention. FIG. 3 is a front view showing a schematic configuration of an image forming apparatus in which the optical printer head L is mounted. This apparatus generally includes an optical printer head L and the photosensitive member P.

  According to the optical printer head L, a plurality of light emitting element array chips 2, a driver IC 4 and the like are mounted on the upper surface of the circuit board 1, and the rod that is the imaging optical system is formed on the light emitting surface of these light emitting element array chips 2. A lens array 5 is arranged. Each of these members is accommodated in a housing (not shown).

  The circuit board 1 is formed by adhering a large number of circuit wirings in a predetermined pattern on the upper surface of a rectangular base made of an electrically insulating material such as a glass cloth base epoxy resin, glass, ceramic, and the like. The individual light emitting element array chip 2 and the driver IC 4 are supported.

  The plurality of light emitting element array chips 2 mounted on the circuit board 1 are arranged in a line along the main scanning direction of the circuit board 1, and each upper surface has, for example, 600 dpi (dot per inch). The light-emitting elements 3 arranged in a straight line with a density and a large number of connection pads electrically connected to the light-emitting elements 3 are connected to the circuit on the circuit board 1 via bonding wires. Electrically connected to the wiring.

  The light-emitting element 3 is composed of, for example, a GaAlAs-based or GaAsP-based light-emitting element, and is configured by pn-junction of a p-type semiconductor and an n-type semiconductor. When power is applied, electrons are injected into the p-type semiconductor and holes are injected into the n-type semiconductor to recombine these carriers in the vicinity of the pn junction. By converting it into light, the light emitting element 3 emits light with a predetermined luminance.

  A predetermined energy is applied to the light emitting element 3 from the outside based on the image data, and the light emitting element emits light for a predetermined time corresponding to the image data.

  Further, the rod lens array 5 arranged on the light emitting element array chip 2 is for irradiating and imaging the light emitted from the light emitting element 3 onto the external photosensitive member P. There are many rod lens arrays 5 as the rod lens array 5. Rod lens array or the like in which rod-shaped lenses (for example, rod-shaped lenses having a lens diameter of 0.8 to 1.0 mm) are linearly arranged or staggered are used, and a lens holder (not shown) by an adhesive. Is fixed in place.

  The photosensitive member P is disposed on the light emitting element array chip 2 of the optical printer head L so as to be separated from the optical printer head L by a predetermined distance and substantially parallel to the optical printer head L.

  The photosensitive member P has a structure in which a photoconductive layer made of an inorganic semiconductor or an organic semiconductor such as amorphous silicon is attached to the outer surface of a cylindrical base made of aluminum or the like. When the photoconductive layer is irradiated with light from the optical printer head L, the specific resistance of the photoconductive layer is rapidly reduced to form a predetermined latent image on the photoconductive layer. The latent image formed on the photoreceptor P becomes a toner image through a development process, and a predetermined image is recorded by transferring and fixing the toner image on a recording sheet.

  Next, a method for manufacturing a rod lens array used for the optical printer head L having the above configuration will be described.

  Steps (1) to (6) are sequentially performed.

  Step (1): First, a three-dimensional intensity distribution of light in the rod lens array transmitted light of the light beam emitted from the light source means is measured at a substantially imaging position. For the measurement, a lens measuring device as shown in FIG. 5 may be used.

  As shown in FIG. 5, a pseudo light emitting element is formed by using an LED light source as a light source means of a measuring apparatus corresponding to a light emitting element of an optical printer head and arranging a light shielding plate provided with a slit. Moreover, the slit to be used shall be a shape according to a use regardless of circular shape and non-circular shape.

  The light from the LED light source is read by an imaging device located in a pair with the light source via a rod lens array disposed at a predetermined position. Further, the light source and the imaging device perform measurement at N positions with respect to a predetermined distance while moving in parallel with the rod lens array. N measurement locations correspond to positions where light emitted from each light emitting element of the optical printer head having N light emitting elements is irradiated to the photosensitive member. Therefore, the LED light source is moved so as to correspond to the arrangement position of each light emitting element of the optical printer head having N light emitting elements, and the light image formation position and the light emitting element arrangement position are the length of the rod lens array. Corresponding to the direction. For convenience, in the following, the N optical image forming positions may be referred to as light emitting elements Di (i = 1, 2,..., N). For example, a CCD is used as the imaging device, and the intensity distribution of light transmitted through the rod lens array by the imaging device is output as an electrical signal. This device has a mechanism in which the rod lens array is fixed and the light source and the imaging device move in pairs, but there is no problem with the mechanism in which the rod lens array moves in terms of workability and productivity. It is good to choose according to.

  The intensity distribution of the light thus obtained is a mountain shape having a peak value in the central region as shown in the three-dimensional perspective view shown in FIG. 6 as a part of the light emitted from the light emitting element spreads toward the periphery. Distribution.

  Step (2): Next, regarding each light emitting element Di (i = 1, 2,..., N), the cross-sectional area Si (i = 1, 2) at a predetermined intensity threshold in the above-described three-dimensional intensity distribution. , ..., N). The predetermined intensity threshold value for calculating the cross-sectional area is set on the basis of the exposure sensitivity of the target photosensitive member because a correlation with the exposure sensitivity of the photosensitive member is recognized.

  FIG. 7 shows the relationship between the EV curve, the spot potential distribution, and the three-dimensional intensity distribution of light on the photoreceptor of the light emitting element having a certain peak. The vertical axis of the EV curve (first quadrant in FIG. 7) indicates the charged potential on the surface of the photoconductor, and the horizontal axis indicates the exposure amount exposed to the photoconductor. The vertical axis of the three-dimensional light intensity distribution (second quadrant in FIG. 7) indicates the width of the light emitting region of the light emitting element, and the horizontal axis indicates the intensity of light emitted by the light emitting element. The intensity threshold value of the three-dimensional intensity distribution of light indicates the intensity of the light emitting element necessary for the charging potential of the photoconductor on the EV curve to be halved. The vertical axis of the spot potential distribution (fourth quadrant in FIG. 7) indicates the charging potential of the photoconductor, and the horizontal axis indicates the width of the light emitting region of the light emitting element. The toner threshold potential shown in the spot potential distribution is the surface potential of the photoconductor at which toner adhesion to the surface of the photoconductor starts, and roughly corresponds to a potential obtained by halving the charged potential of the photoconductor.

For example, when the half-exposure sensitivity of the photoconductor required to reduce the surface potential of the photoconductor to ½ is 2 to 10 cm ² / μJ, the intensity threshold value is 2 of the peak value for each light emitting element. It is desirable to select a range of intensity corresponding to -5%, or 2-5% of the average of the peak values.

A little more explanation about the intensity threshold is added. Among the three-dimensional intensity distribution of the light emitting element, the intensity direction can also be represented by a digital value, for example if the digital output is 8 bits, the strength is expressed by a range of 2 ^{0-2 8,} i.e. 0-255 Can do. Similarly, in the case of 10 bits, it can be expressed in the range of 2 ⁰ to 2 ¹⁰ , that is, ⁰ to 1023.

  In the example of 8-bit digital output, if the average value of peak values for each light emitting element is 200, the intensity corresponding to 2 to 5% of the average value of peak values is 4 to 10.

Step (3): Next, as shown in Equation 1, the average cross-sectional area of the intensity distribution of the group including h1 light emitting elements before and after the kth light emitting element Dk (1 ≦ k ≦ N), In other words, a moving average is calculated and is set as an ideal cross-sectional area P (k).

  This moving average process has a role of a low-pass filter, which can remove short-period variations from the ideal cross-sectional area P (k) of each light-emitting element. By appropriately selecting the value of h1, the ideal cross-sectional area P (k) becomes a curve having a gentle undulation.

  This curve is obtained by removing short-period variations sensitive to the human eye from the cross-sectional area of each light-emitting element measured as shown in FIG. 8 and having only long-period variations. By determining the Obimura element of the rod lens array based on the curve, the sense of unevenness in the output image is at a good level that cannot be recognized by human vision.

  The horizontal axis of FIG. 8 shows the arrangement of the light emitting elements measured for the three-dimensional intensity distribution of light, the vertical axis is the cross-sectional area value (arbitrary unit), and the curve A is the cross-sectional area Si of each light emitting element. Curve B is the result of moving average curve A (ideal cross-sectional area P (k)).

  According to this moving average, by changing the value of h1, it is possible to change the length of the section in which the moving average is performed and to select the period of variation to be removed. If this value is increased, variations in a wide period can be removed. However, if the value is increased too much, the ideal cross-sectional area P (k) becomes a flat straight line, so that the accuracy of extracting the Obimura element decreases.

  If the value h1 is reduced, the range of variation that can be removed is reduced. However, if the value h1 is too small, there is a short-cycle variation component that is recognized by human vision, and the effect as a low-pass filter is lost.

When this inventor experimented the relationship between the section length which performs a moving average calculation, h1 value, and Obimura, the result as shown in Table 1-Table 3 was obtained. In Table 1, when the diameter of each rod lens constituting the rod lens array is 0.9 mm and the arrangement density of the light emitting elements is 600 dpi, Table 2 shows the diameter of the rod lenses is 0.6 mm and the arrangement density of the light emitting elements is 600 dpi. Table 3 shows the results when the diameter of the rod lens is 0.6 mm and the arrangement density of the light emitting elements is 1200 dpi.

  In the same table, it is divided into five types, 、, ○, Δ, ×, XX, and 印 is a satisfactory level that cannot be discriminated by human eyes as to whether or not there is obscuration. ○ mark is a level that can be recognized that there is a slight ambimura depending on how the light is applied, △ mark is a level that can be recognized that there is a slight ambimura regardless of how the light is applied, X mark, XX As the mark becomes, the state that the obi-mura becomes remarkably worse is shown.

  According to Table 1 to Table 3, in the case of Table 1, the length of the section where the moving average calculation is performed falls within the range of 1.5 to 30 mm, and in the case of Table 2 and Table 3, the length falls within the range of 1.5 to 15.7 mm. It is good to choose as follows. Regarding the specific value of h1, in Table 1, the lower limit of h1 is 2h1 + 1 = 1.5 mm / 0.0423 mm (0.0423 mm indicates the interval between adjacent light emitting elements) = 35. Thus, h1 = 17. Further, the upper limit of h1 is 2h1 + 1 = 30 mm / 0.0423 mm = 709, and thus h1 = 354. In the case of Table 2, the lower limit of h1 is the same as that of Table 1. On the other hand, the upper limit of h1 is 2h1 + 1 = 15.7 mm / 0.0423 mm = 371, which results in h1 = 185. In the case of Table 3, since the arrangement density of the light emitting elements is doubled as compared with the cases of Table 1 and Table 2, the interval between the light emitting elements is ½. Therefore, the range of h1 is about twice that of Table 2, and the range of h1 is 35 to 371.

  When h1 light emitting elements do not exist before and after the light emitting element Dk (for example, in the case of a light emitting element near the end of the optical printer head), P (k) is not calculated and the object of the obi unevenness determination It is outside.

Step (4): When the light emitting element Di (i = 1, 2,..., N) is divided into M sections, and the average cross-sectional area of the intensity distribution in each section is Si, the following formula 2 is obtained. In this way, the average value of the cross-sectional areas composed of h2 light emitting elements, that is, the section average is calculated, and is set as the section cross-sectional area Q (l) (1 ≦ l ≦ M). Note that Q (l) has the same value for each light irradiation position belonging to the l-th section.

  This interval averaging process serves as a high frequency noise filter as shown in FIG. Thereby, a high frequency noise component can be removed from the cross-sectional area Si of each light emitting element.

  Here, the high-frequency noise component indicates a high-frequency variation of the intensity area Si at a level that does not contribute to printing, a variation caused by a dark current of the CCD camera, or the like.

  According to the section averaging process, by changing the value of h2, the length of the section to be averaged can be changed and the period of variation to be removed can be selected. If this value is increased, variations in a wide period can be removed. However, if the value is increased too much, the section cross-sectional area Q (l) becomes close to the reference value, so that the accuracy of extracting the Obimura element decreases.

  If h2 is reduced, the period of variation that can be removed is reduced, but if it is too small, the effect of the section averaging process itself, that is, the effect of removing high-frequency noise components is lost.

The inventor conducted experiments on the relationship between the interval length for calculating the interval averaging, the h2 value, and Obimura, and the results shown in Tables 4 to 6 were obtained. In Table 4, when the diameter of each rod lens constituting the rod lens array is 0.9 mm and the arrangement density of the light emitting elements is 600 dpi, Table 5 shows the diameter of the rod lenses is 0.6 mm and the arrangement density of the light emitting elements is 600 dpi. Table 6 shows the results when the diameter of the rod lens is 0.6 mm and the arrangement density of the light emitting elements is 1200 dpi.

  In the same table, it is divided into five types, 、, ○, Δ, ×, XX, and 印 is a satisfactory level that cannot be discriminated by human eyes as to whether or not there is obscuration. ○ mark is a level that can be recognized that there is a slight ambimura depending on how the light is applied, △ mark is a level that can be recognized that there is a slight ambimura regardless of how the light is applied, X mark, XX As the mark becomes, it shows a state where the ora becomes significantly worse.

  According to Tables 4 to 6, in the case of Table 4, the length of the section for performing the averaging calculation is 0.51 to 2.37 mm, and in the case of Table 5, the length of the section for performing the averaging calculation is 0. In the case of .51 to 2.3 mm and Table 6, selection may be made so that the length of the section for performing the averaging calculation falls within the range of 0.51 to 1.89 mm. Regarding the specific value of h2, in Table 4, the lower limit of h2 is h2 = 0.51 mm / 0.0423 mm = 12. The upper limit of h2 is h2 = 2.37 mm / 0.0423 mm = 56. In the case of Table 5, the lower limit of h2 is h2 = 12, and the upper limit is 2.3 mm / 0.0423 mm = 54. In the case of Table 6, the lower limit of h2 is h2 = 0.51 / 0 because the arrangement density of the light emitting elements is doubled and the interval between the light emitting elements is ½ compared to the cases of Table 4 and Table 5. .02115 = 24, and the upper limit of h2 is h2 = 1.89 / 0.02115 = 89.

  Step (5): Finally, Y, which is an Obimura index of the rod lens array, is calculated, and a non-defective rod lens array is determined based on the index. The rod lens array is completed through the above steps. The calculation method of the Obimura index is as follows.

  As shown in FIG. 10, Q (l) −P (k), which is the difference between the section cross-sectional area Q (l) obtained in the step (4) and the ideal cross-sectional area P (k) obtained in the step (3). ) Divided by the ideal cross-sectional area P (k), the maximum value or the minimum value Rk (k = 1, 2,..., N) is defined as the Obimura element Y of the rod lens array. As a result, it is possible to determine the level of obi unevenness caused by the rod lens array. Note that Q (l) is the section sectional area of the section to which the kth optical imaging position having the ideal sectional area P (k) belongs.

  This is because the inventor believes that Obimura occurs due to the presence of a local (partial) arrangement abnormality in the rod lens array, and therefore, the section sectional area Q (l) and the ideal sectional area P ( The larger the difference in k) is, the more noticeable Obimura becomes.

  When the inventor conducted an experiment on the relationship between the Obimura element Y in the lens inspection and the Obimura on the print, a result as shown in FIG. 11 was obtained.

  The horizontal axis in FIG. 11 represents a value obtained by taking the print output from the printer with a scanner and digitizing the difference in shading of the obi unevenness. The larger the value, the greater the difference in shade of Obimura. The vertical axis in FIG. 11 shows the result of the lens inspection based on the cross-sectional area in the three-dimensional intensity distribution of light, and the Obimura element Y is an absolute value for the value of the lens inspection. The numerical values in the figure indicate that the smaller the value is, the better the image quality is, and the larger the value is, the stronger the Obimura becomes.

  The present inventor has proposed an optical print head having a printing density of 600 dpi and an individual lens diameter of the rod lens array of 0.8 mm to 1.0 mm as a rod lens array capable of providing an excellent image quality without obscuration. As for Obimura element Y, it has been experimentally derived that ± 0.080 or less, preferably ± 0.065 or less. However, it is preferable to select optimum values for these values depending on the measuring machine and the image forming apparatus to be used.

  In addition, this invention is not limited to the above-mentioned form, A various change, improvement, etc. do not interfere in the range which does not deviate from the summary of this invention.

  (1) For example, in the above-described embodiment, an LED is used as a light source. However, instead of this, a light source means such as a lamp may be used.

  (2) In the above-described embodiment, the light source means using the LED light source and the slit is used. Instead, a light source means such as a point light source may be used as shown in FIG.

  (3) Further, the lighting method of the light source in the above embodiment is lighting one element at a time, but instead of this, as shown in FIG. The intensity distribution may be measured.

  (4) Further, as the lighting method of the light source in the above-described embodiment, the three-dimensional intensity distribution for all the elements was measured. Instead, as shown in FIG. 14, lighting is performed every other element or every two elements. Then, the three-dimensional intensity distribution may be measured.

  (5) Although the CCD camera is used for the measurement of the three-dimensional light intensity distribution in the above-described embodiment, other light quantity detection means such as a photodiode may be used instead.

  (6) In the above-described embodiment, the cross-sectional area of the three-dimensional intensity distribution of light is used for extracting Obimura, but the diameter (vertical or horizontal) may be used.

It is a perspective view of the rod lens array of the present invention. 2 is an exploded perspective view of an optical print head L. FIG. 1 is a front view illustrating a schematic configuration of an image forming apparatus. It is the figure which showed the correlation by the determination by MTF, and Obimura. It is the apparatus schematic for using for the characteristic evaluation of a rod lens array. It is a three-dimensional perspective view which shows the light emission intensity distribution of a light emitting element. It is a figure which shows the relationship between the EV curve in a photoreceptor, spot electric potential distribution, and the three-dimensional intensity distribution of light. It is a figure which shows the ideal cross-sectional area computed by performing the intensity | strength cross-sectional area of a light emitting element, and a moving average calculation. It is a figure which shows the area cross section calculated by performing the area averaging process. It is a figure which shows the calculation method which guides an Obimura element based on an ideal cross-sectional area and a section cross-sectional area. It is the figure which showed the correlation of the test result of a rod lens array, and Obimura. It is the figure which showed the example at the time of test | inspecting using a point light source as a light source unit. It is the figure which showed the example at the time of test | inspecting using a several light source as a light source unit. It is the figure which showed the example at the time of test | inspecting by turning on several light source units alternately.

Explanation of symbols

L ... Optical print head P ... Photoconductor 1 ... Circuit board 2 ... Light emitting element array chip 3 ... Light emitting element 4 ... Driver IC
5 ... Lens array

Claims (5)

In a method of manufacturing a rod lens array in which light emitted from light source means having a light emitting element is imaged on a recording medium, the rod lens is manufactured through the following steps (1) to (5) in sequence. Array manufacturing method.
(1) Using a lens measuring device having a light source means and an imaging device positioned in pairs via the rod lens array, the three-dimensional intensity distribution of light from the light source means transmitted through the rod lens array is different. Measurement is sequentially performed at N (N is a natural number) optical imaging positions.
(2) The cross-sectional area of the three-dimensional intensity distribution is obtained with a predetermined intensity threshold at each of the light imaging positions.
(3) A cross-sectional area of the three-dimensional intensity distribution with respect to a group consisting of each of the optical imaging positions and an optical imaging position included in a section of 1.5 to 15.7 mm centering on the optical imaging position. A moving average value is calculated, and this is set as an ideal cross-sectional area P (k) (1 ≦ k ≦ N) (k is a natural number).
(4) The N optical imaging positions are divided into M sections (M is a natural number) such that the section length is in the range of 0.51 to 1.89 mm, and the three-dimensional intensity distribution is related to each section. The average cross-sectional area is calculated, and this is defined as the section cross-sectional area Q (l) (2 ≦ l ≦ M) (l is a natural number). However, the section length of the M sections is shorter than the section length for calculating the moving average value in (3).
(5) R (k) = [Q (l) −P (k)] / P (k) is calculated for each of the light imaging positions, and the value of R (k) is within a predetermined range. Make the rod lens array non-defective. However, Q (l) is a section sectional area of a section to which the kth optical imaging position having the ideal sectional area P (k) belongs.   2. The method of manufacturing a rod lens array according to claim 1, wherein in the step (2), a predetermined intensity threshold value is determined based on the sensitivity of the photosensitive member.   The method of manufacturing a rod lens array according to claim 2, wherein the sensitivity of the photoconductor is half exposure sensitivity. 4. The rod lens array according to claim 3, wherein the half-exposure sensitivity is ² to 10 cm ² / μJ, and the intensity threshold is selected in a range of 2 to 5% of a peak value of a three-dimensional intensity distribution of each light emitting element. Method. The rod lens according to claim 3, wherein the half-exposure sensitivity is ² to 10 cm ² / μJ, and the intensity threshold is selected in a range of 2 to 5% of an average value of a peak value of a three-dimensional intensity distribution of each light emitting element. Array manufacturing method.

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