CN101403877B - Line head and image forming apparatus using the same - Google Patents

Abstract

The present invention provides a line head and an image forming apparatus using the line head, wherein light formed by arranging a plurality of light-emitting elements in columns is written in the positive lens system of the line head in a manner corresponding to each of a plurality of positive lens systems arranged in a matrix. The diameter of the lens system is as small as possible. A luminous body group comprising one or more light-emitting element rows in which a plurality of light-emitting elements are arranged in a row in the main scanning direction is arranged at least in a plurality of groups at intervals in the main scanning direction to form a luminous body array (1), and when the light is emitted The emitting side of the body array (1) is configured with a lens array configured in such a way that a positive lens system (5) is neatly arranged respectively corresponding to each illuminant group, and a writing surface (41) is configured on the imaging side of the lens array to form a lens array. Each positive lens system (5) of the array is composed of two lens groups (L1, L2) of positive refractive power, an aperture stop (11) is arranged therebetween, and the image side lens (L2) is approximately telecentric on the image side. ) and the width of the light-emitting element image group of the writing surface (41) along the main scanning direction satisfy conditional expressions (21), (24).

Description

Line head and image forming device using line head

technical field

The present invention relates to a line head and an image forming device using the line head, in particular to a line head using a microlens array to project light-emitting element columns on an irradiated surface to form imaging dot columns and an image forming device using the line head. the

Background technique

Currently, Patent Document 1 proposes a line head for optical writing as follows and a line head for optical reading by reversing its optical path: a plurality of LED array chips are arranged in the direction of the LED array, and each LED array is connected by a corresponding positive lens. The LED array of the chip is enlarged and projected on the photoreceptor, and the images of the light-emitting points at the ends of adjacent LED array chips on the photoreceptor are contiguously imaged at the same pitch as the image pitch of the light-emitting points of the same LED array chip. the

In addition to the arrangement in Patent Document 1, Patent Document 2 proposes to configure a positive lens with two lenses, and to deepen the depth of focus so that projected light becomes closer to parallel light. the

In addition, Patent Document 3 proposes an optical writing line head as follows, in which LED array chips are arranged in two rows at intervals, and their repeated phases are staggered by a half period, and each positive lens corresponds to each LED array chip, and two rows of positive lenses are arranged. A lens array, and make the image of the luminescent point array on the photoreceptor a column. the

Patent Document 1: JP-A-2-4546 Gazette

Patent Document 2: JP-A-6-344596 Gazette

Patent Document 3: Japanese Patent Laid-Open No. 6-278314

In these conventional technologies, when the angle of view of each positive lens increases, the decrease in the amount of light at the periphery also increases (shields) according to the cos4 multiplication law. In order to prevent the density unevenness of the printed image caused by this shading, it is necessary to set the light intensity of each pixel (light-emitting point image) on the image surface to be constant, but it is necessary to change the light intensity of the light source (light-emitting point) for each light-emitting point to correct Blackout. However, since the luminous intensity of the light source pixel (light-emitting point) has an influence on the lifetime characteristics, when the shading of the optical system increases, even if the light quantity is adjusted for each luminous point and a uniform image-plane light quantity is obtained initially, as time passes, There may also be unevenness in the amount of light at the pitch of the light-emitting points, resulting in unevenness in the characteristic density. the

In addition, when a plurality of light-emitting point arrays are arranged in parallel in the sub-scanning direction, if the lens diameter of the optical system increases, the width of the optical writing line head in the sub-scanning direction increases, making it difficult to miniaturize the image forming apparatus. the

Contents of the invention

The present invention is made in view of the problems of the prior art, and an object of the present invention is to provide an optical writing line head in which a plurality of light-emitting elements are arranged in columns corresponding to each lens system of a plurality of positive lens systems arranged in an array. Among them, by setting the lens diameter of each lens system as small as possible, the line head and the image forming apparatus using the line head can be miniaturized. the

Another object of the present invention is to prevent unevenness due to misalignment of the light-emitting point image even if the writing surface varies in the direction of the optical axis. the

To achieve the above object, the present invention provides a line head, characterized in that, has:

Positive lens system with two lenses of positive refractive power;

An image-side lens array formed by arranging a plurality of image-side lenses among the two lenses in the first direction and the second direction;

An object-side lens array formed by arranging a plurality of object-side lenses among the two lenses in the first direction and the second direction;

On the object side of the positive lens system, an illuminant array of a plurality of light-emitting elements is configured relative to the positive lens system of 1;

A diaphragm plate is disposed between the image side lens array and the object side lens array and forms an aperture stop in such a manner that it becomes telecentric or substantially telecentric on the image side. The chief ray in space is parallel to the optical axis, and becomes approximately telecentric on the image side, which means that the chief ray in the image space is within ±1° of the optical axis,

Assume that the number of columns of lenses disposed in the second direction in the image-side lens array is m, the interval between the effective areas of two adjacent image-side lenses in the first direction is α, and the positive lens The image-side aperture angle (half angle) of the positive lens system is θ _i , and the image on the image plane of a plurality of light-emitting elements of the positive lens system, that is, the width of the first direction of the images of the plurality of light-emitting elements (full Width) is W _i , the focal length of the image side lens is f ₂ , and the distance from the image side main surface of the image side lens to the image side is S _i , the following conditions are met:

f ₂ ≤(mW _i -α)/(2θ _i ) …(21)

W _i ≥2S _i θ _i /(m-1)+α/(m-1) …(24)

With this configuration, even if the position of the writing surface is shifted in the optical axis direction, the imaging point will not be misaligned, thereby preventing the deterioration of the formed image, and the diameter of the aperture stop can be set to be consistent with that of the lens array constituting the lens array. The effective diameter of the lens on the image side of the two lenses of each positive lens system is approximately the same or less than that, and the effective diameter of the lens on the object side can be set to be approximately the same as or less than the effective diameter of the lens on the image side. The positive lens systems are arranged in a matrix to avoid interference with adjacent positive lens systems. the

In this case, it is desirable that the width (full width) W _i of the plurality of light emitting element images in the first direction has the following conditions.

W _i ≥ 2S _i θ _i /(m—1)+α/(m—1) …(24)'

With such a configuration, in addition to the above-described operation and effect, the effective diameter of the image-side lens can be kept small. the

The present invention also provides a line head, characterized in that it has:

Positive lens system with two lenses of positive refractive power;

An image-side lens array formed by arranging a plurality of image-side lenses among the two lenses in the first direction and the second direction;

An object-side lens array formed by arranging a plurality of object-side lenses among the two lenses in the first direction and the second direction;

On the object side of the positive lens system, a luminous body array with a plurality of light-emitting elements is arranged relative to one of the positive lens systems;

A diaphragm plate for an aperture diaphragm disposed on the image side in a telecentric or substantially telecentric manner is formed between the image side lens array and the object side lens array,

The image-side lens is composed of a convex-flat lens whose surface on the image side is a plane,

The number of columns of lenses arranged in the second direction in the image-side lens array is set to m, the interval between the effective areas of two adjacent image-side lenses in the first direction is set to α, and The image-side aperture angle (half angle) of the positive lens system is set to _θi , and the images on the image plane of the plurality of light-emitting elements arranged with respect to one of the positive lens systems, that is, the first image of the plurality of light-emitting elements The width (full width) in the direction is set as W _i , the focal length of the image side lens is set as f ₂ , the distance from the image side plane of the image side lens to the image plane is set as d ₂ ′, and The images of the image planes of the plurality of light-emitting elements corresponding to one of the positive lenses, that is, the outermost rays of the light beams converged by the light-emitting element images at the ends of the plurality of light-emitting element images in the first direction, are incident on the When the distance between the point of the convex surface on the object side of the image side lens and the optical axis direction of the image side plane of the image side lens is e _t2 , and the refractive index of the image side lens is n ₂ , the following conditions are present :

f ₂ ≤(mW _i —α)/(2θ _i ) …(21)

W _i ≥2(d ₂ '+et ₂ /n ₂ )θ _i /(m—1)+α/(m—1) …(27)

With this configuration, even if the position of the writing surface is shifted in the optical axis direction, the imaging point will not be misaligned, thereby preventing the deterioration of the formed image, and the diameter of the aperture stop can be set to be consistent with that of the lens array constituting the lens array. The effective diameter of the lens on the image side of the two lenses of each positive lens system is approximately the same or less than that, and the effective diameter of the lens on the object side can be set to be approximately the same as or less than the effective diameter of the lens on the image side. The positive lens systems are arranged in a matrix to avoid interference with adjacent positive lens systems. the

In this case, it is desirable that the width (full width) W _i of the plurality of light emitting element images in the first direction has the following conditions.

W _i =2(d ₂ '+e _t2 /n ₂ )θ _i /(m—1)+α/(m—1)

With such a configuration, in addition to the above-described operation and effect, the effective diameter of the image-side lens can be kept small. the

As described above, it is preferable that the aperture plate is disposed on a front focal plane of the image side lens. the

With this configuration, each positive lens system of the lens array is telecentric on the image side, and even if the position of the writing surface is shifted in the optical axis direction, the imaging point does not misalign, and the deterioration of the formed image can be prevented. the

In addition, it is desirable that the aperture plate is disposed close to the object side lens. the

With this configuration, the diameter of the object side lens can be prevented from increasing. the

In addition, an image forming apparatus can be configured including a latent image carrier; a charging unit for charging the latent image carrier; the line head as described above; and a developing unit for developing the latent image carrier. the

With such a configuration, it is possible to configure an image forming apparatus such as a printer that is compact, has high resolution, and has little image degradation. the

Description of drawings

Fig. 1 is a perspective view of a part corresponding to a microlens of a line head according to an embodiment of the present invention;

Fig. 2 is a perspective view of a part corresponding to a microlens of a line head according to an embodiment of the present invention;

Fig. 3 is a perspective view of a part corresponding to a microlens of the line head of an embodiment of the present invention;

Fig. 4 is an explanatory diagram showing the corresponding relationship between an array of light emitters according to an embodiment of the present invention and a microlens whose optical magnification is negative;

Fig. 5 is an explanatory diagram showing an example of a storage table of a line buffer storing image data;

FIG. 6 is an explanatory diagram showing how imaging points obtained by forming light-emitting elements with odd numbers and even numbers in the same column in the main scanning direction;

Fig. 7 is a schematic explanatory diagram showing an example of an array of illuminants used as a line head;

Fig. 8 is an explanatory diagram showing the imaging position when the output light of each light-emitting element is used to irradiate the exposure surface of the image carrier through the microlens in the composition of Fig. 7;

FIG. 9 is an explanatory view showing the state of formation of imaging points in the sub-scanning direction in FIG. 8;

FIG. 10 is an explanatory diagram showing an example in which an imaging point is formed by reversing the main scanning direction of the image carrier when a plurality of microlenses are arranged;

11 is a schematic cross-sectional view showing the overall configuration of an embodiment of an image forming apparatus using the electrophotographic process of the present invention;

Figure 12 is a diagram for illustrating a light beam exiting from a light source and being taken into the aperture of the optical system;

Fig. 13 is a diagram representing the relationship between the image of the light-emitting element on the image plane, that is, the group of imaging points and the corresponding microlens;

Fig. 14 is a figure representing the definition of the symbol of each parameter;

Fig. 15 is a diagram for obtaining the conditions for making the diameter of the aperture stop substantially equal to the effective diameter of the second lens;

Fig. 16 is a diagram representing the range that the width of the image plane pixel group and the effective diameter of the second lens meet;

Fig. 17 is an optical path diagram for exploring the configuration of the first lens;

Fig. 18 is the figure that is used to discuss the situation that the second lens that constitutes microlens is formed by convex-flat wall thickness lens;

Figure 19 is an enlarged representation near the second lens of Figure 18;

Fig. 20 is a perspective view showing a part of the structure of an optical writing line head according to an embodiment of the present invention;

Figure 21 is a sectional view along the sub-scanning direction of Figure 20;

Fig. 22 is a plan view showing the configuration of the illuminant array and the microlens array in the situation of Fig. 20;

Figure 23 is a diagram representing the corresponding relationship between a microlens and the corresponding illuminant block;

Fig. 24 is a plan view of an aperture plate configured correspondingly to the illuminant block of the illuminant array;

Figure 25 is a diagram representing the aperture of the diaphragm plate relative to a luminous body block;

Fig. 26 is a diagram corresponding to Fig. 22 in which light-emitting elements are arranged in long columns in the main scanning direction and a part of them is controlled to emit light to form a light-emitting body block;

Figure 27 is a cross-sectional view along the main scanning direction when two microlens arrays form a microlens array;

Fig. 28 is a sectional view of the main scanning direction and the sub-scanning direction of the optical system corresponding to a microlens of embodiment 1;

Fig. 29 is a sectional view of the main scanning direction and the sub-scanning direction of the optical system corresponding to a microlens of embodiment 2;

Figure 30 is a sectional view of the main scanning direction and the sub-scanning direction of the optical system corresponding to a microlens of embodiment 3;

Figure 31 is a sectional view of the main scanning direction and the sub-scanning direction of the optical system corresponding to a microlens of embodiment 4;

32 is a cross-sectional view along the main scanning direction of an example in which a glare stop plate is arranged independently of the stop plate in the optical system of the optical writing line head of the present invention. the

Symbol Description

1 luminous body array; 2 light-emitting elements; 2' light-emitting elements related to the formation of imaging points; 2" non-light-emitting light-emitting elements; 3 light-emitting element columns; 3' continuous long column-like light-emitting element columns in the main scanning direction ; 4 illuminant block; 5 microlens; 6 microlens array; 8, 8a, 8b imaging point; 10 storage table; 11 aperture diaphragm; 20 glass substrate; 21 strip shell; 22 support hole; 23 back cover; 24 fixed metal parts; 25 positioning pins; 26 insertion holes; 27 sealing parts; 30 aperture plate; 31 aperture of aperture plate; 32 glare aperture plate; 33 aperture of glare aperture plate; Lens face; 41 photoreceptor (image carrier, image surface); 41 (K, C, M, Y) photoreceptor drum (image carrier); 42 (K, C, M, Y) charging device (corona charger) ; 44 (K, C, M, Y) developing device; 45 (K, C, M, Y) primary transfer roller; 50 intermediate transfer belt; 51 driving roller; 52 driven roller; 53 tension roller; 61 first A microlens array; 62 second microlens arrays; 66 secondary transfer rollers; 71 first pads; 72 second pads; 73 third pads; groups of 80 imaging points; 101, 101K, 101C, 101M , 101Y line head (light writing line head); a, b, c lens column; O-O' lens optical axis; L1 first lens; L2 second lens. 

Detailed ways

Before explaining the optical system of the line head of the present invention in detail, the arrangement and timing of light emitting elements thereof will be briefly described. the

FIG. 4 is an explanatory diagram showing the correspondence relationship between the luminous body array 1 and the microlens 5 with negative optical magnification according to one embodiment of the present invention. In the line head of this embodiment, one microlens 5 corresponds to two columns of light emitting elements. However, since the microlens 5 is an imaging element with a negative optical magnification (inverted imaging), the positions of the light emitting elements are reversed in the main scanning direction and the sub scanning direction. That is, in the structure of Fig. 1, even-numbered light-emitting elements (8, 6, 2, 4) are arranged on the upstream side (first row) of the moving direction of the image carrier, and odd-numbered light-emitting elements (8, 6, 2, 4) are arranged on the same downstream side (second row). Light emitting elements (7, 5, 3, 1). In addition, light-emitting elements with higher serial numbers are arranged on the head side in the main scanning direction. the

1 to 3 are perspective views of a portion corresponding to one microlens of the line head according to this embodiment. As shown in FIG. 2 , imaging points 8 a of image carrier 41 corresponding to odd-numbered light emitting elements 2 arranged on the downstream side of image carrier 41 are formed at positions reversed in the main scanning direction. R is the moving direction of the image carrier 41 . In addition, as shown in FIG. 3 , the imaging points 8 b of the image carrier 41 corresponding to the even-numbered light-emitting elements 2 arranged on the upstream side (first row) of the image carrier 41 are formed on the downstream side reversed in the sub-scanning direction. Location. However, in the main scanning direction, the positions of the imaging points from the front side correspond in the order of the numbers of the light emitting elements 1 to 8 . Therefore, it is found that in this example, imaging dots can be formed in the same row in the main scanning direction by adjusting the timing of forming imaging dots on the image carrier in the sub-scanning direction. the

FIG. 5 is an explanatory diagram showing an example of a memory table 10 of a line buffer storing image data. The storage table 10 in FIG. 5 stores the serial numbers of the light emitting elements in FIG. 4 in reverse in the main scanning direction. In Fig. 5, among the image data stored in the storage table 10 of the line buffer, the first image data (1, 3, 5, 7) corresponding to the light-emitting elements on the upstream side (first row) of the image carrier 41 are first read out. ) to make the light-emitting element emit light. Next, after T time, read out the second image data (2, 4, 6, 8) corresponding to the light-emitting elements on the downstream side (second column) of the image carrier 41 stored in the memory address, and make the light-emitting elements emit light. In this way, as shown by the position 8 in FIG. 6 , the imaging dots of the first column on the image carrier are formed in the same column as the imaging dots of the second column in the main scanning direction. the

Fig. 1 is a perspective view conceptually showing an example in which image data is read out and imaging dots are formed at the timing of Fig. 5 . As described with reference to FIG. 5 , the light-emitting elements on the upstream side (first row) of the image carrier 41 are first illuminated to form imaging dots on the image carrier 41 . Next, after a predetermined timing T has elapsed, the odd-numbered light-emitting elements on the downstream side (second column) of the image carrier 41 emit light to form imaging dots on the image carrier. At this time, the imaging points of the odd-numbered light-emitting elements are not at the position 8a described in FIG. 2 , but are formed at the position 8 in the same row in the main scanning direction as shown in FIG. 6 . the

Fig. 7 is a schematic explanatory diagram showing an example of a luminous body array used as a line head. In FIG. 7 , on the luminous body array 1 , a plurality of light-emitting element rows 3 formed by arranging a plurality of light-emitting elements 2 in the main scanning direction are arranged along the sub-scanning direction to form luminous body blocks 4 (see FIG. 4 ). In the example of FIG. 7 , the luminous body block 4 has two light-emitting element rows 3 in which four light-emitting elements 2 are arranged in the main scanning direction in the sub-scanning direction (see FIG. 4 ). There are multiple illuminant blocks 4 arranged on the illuminant array 1 , and each illuminant block 4 is arranged correspondingly to the microlens 5 . the

A plurality of microlenses 5 are provided in the main scanning direction and the subscanning direction of the illuminant array 1 to form a microlens array (MLA) 6 . The MLA 6 is arranged at a head position shifted in the sub-scanning direction in the main-scanning direction. Such an arrangement of MLAs 6 corresponds to the case where the light emitting elements are arranged in a zigzag pattern in the light emitting body array 1 . In the example of FIG. 7 , the MLAs 6 are arranged in three rows in the sub-scanning direction. For convenience of explanation, the unit blocks 4 corresponding to the positions of the three rows of MLAs 6 in the sub-scanning direction are divided into group A, group B, and group C. the

As mentioned above, when a plurality of light-emitting elements 2 are arranged in the microlens 5 whose optical magnification is negative, and the lenses are arranged in multiple rows in the sub-scanning direction, a row of imaging points arranged side by side in the main scanning direction of the image carrier 41 is formed. , and image data control such as the following is required. (1) Reversal of the sub-scanning direction; (2) Reversal of the main scanning direction; (3) Light-emitting timing adjustment of multiple rows of light-emitting elements in the lens; (4) Light-emitting timing adjustment of light-emitting elements between groups. the

FIG. 8 is an explanatory diagram illustrating an imaging position when the light output from each light emitting element 2 irradiates the exposure surface of the image carrier through the microlens 5 in the configuration of FIG. 7 . In FIG. 8 , as explained in FIG. 7 , unit blocks 4 divided into groups A, B, and C are arranged in the luminous body array 1 . Divide the light-emitting element columns of the unit blocks 4 of the group A, group B, and group C into the upstream side (first column) and the downstream side (second column) of the image carrier 41, and assign even-numbered light emitting elements to the first column. For elements, assign odd-numbered light-emitting elements to the second column. the

In group A, as described in FIGS. 1 to 3 , by operating each light emitting element 2 , image forming dots are formed on the image carrier 41 at positions where the main scanning direction and the sub scanning direction are reversed. In this way, imaging dots are formed on the image carrier 41 in the order of 1 to 8 in the same column in the main scanning direction. Next, the image carrier 41 is moved for a predetermined time in the sub-scanning direction, and the processing of group B is similarly executed. In addition, by moving the image carrier 41 in the sub-scanning direction for a predetermined time, the processing of group C is executed, and imaging dots based on the input image data are formed in the same column in the main-scanning direction in the order of 1 to 24 . . . the

FIG. 9 is an explanatory diagram showing a state of formation of imaging dots in the sub-scanning direction in FIG. 8 . S is the moving speed of the image carrier 41, d1 is the distance between the first column of group A and the second column of light-emitting elements, d2 is the distance between the second column of light-emitting elements of group A and the second column of light-emitting elements of group B, d3 is The interval between the second row of light-emitting elements of group B and the second row of light-emitting elements of group C, T1 is the time from the second row of light-emitting elements of group A to the first row of light-emitting elements, and T2 is the second row of group A The time when the imaging position of the light-emitting elements in the column moves to the imaging position of the second column of light-emitting elements in group B, T3 is the time when the imaging position of the second column of light-emitting elements in group A moves to the imaging position of the second column of light-emitting elements in group C . the

T1 can be obtained as follows. T2 and T3 can be similarly obtained by replacing d1 with d2 and d3. the

T1＝|(d1×β)/S|

Here, each parameter is as follows. the

D1: Distance in the sub-scanning direction of the light-emitting element

S: The moving speed of the imaging surface (image carrier)

β: lens magnification

In FIG. 9 , the light emitting elements in the second column of group B are made to emit light after the time T2 elapses when the light emitting elements in the second column of group A emit light. Furthermore, after the time T3 elapses from T2, the light emitting elements in the second row of the group C are made to emit light. The light-emitting elements in the first column of each group emit light after the time T1 elapses after the light-emitting elements in the second column emit light. By performing such a process, as shown in FIG. 8 , the imaging points of the luminous bodies arranged two-dimensionally in the luminous body array 1 can be formed in a row on the image carrier. FIG. 10 is an explanatory view showing an example in which the image forming dot is reversed and formed in the main scanning direction of the image carrier when a plurality of microlenses 5 are arranged. the

An image forming apparatus can be configured using the line head as described above. In this one embodiment, use four line heads to expose on four photoreceptors, form four-color images simultaneously, and the serial type color printer (image formation) that transfers on an endless intermediate transfer belt (intermediate transfer medium) device) can use the line head as above. 11 is a longitudinal sectional side view showing an example of a serial image storage device using an organic EL element as a light-emitting element. This image forming apparatus is a device in which four line heads 101K, 101C, 101M, and 101Y of the same configuration are respectively arranged at exposure positions of four photoreceptor drums (image carriers) 41K, 41C, 41M, and 41Y of the same configuration. A serial image forming apparatus is configured. the

As shown in FIG. 11 , the image forming apparatus is provided with a driving roller 51, a driven roller 51, and a tension roller 53, and is equipped with a motor that is suspended under tension by the tension roller 53 and is circularly driven in the direction of the arrow in the figure (counterclockwise direction). An intermediate transfer belt (intermediate transfer medium) 50 . Photoreceptors 41K, 41C, 41M, and 41Y having photosensitive layers are arranged on the outer peripheral surfaces of four image carriers arranged at predetermined intervals with respect to the intermediate transfer belt 50 . the

K, C, M, and Y attached to the symbols above represent black, cyan, magenta, and yellow, respectively, and represent photoreceptors for black, cyan, magenta, and yellow, respectively. The same applies to other components. The photoreceptors 41K, 41C, 41M, and 41Y are driven to rotate in the direction of the arrows in the figure (clockwise) in synchronization with the drive of the intermediate transfer belt 50 . Around each photoreceptor 41 (K, C, M, Y), there are respectively provided charging devices (corona chargers) 42 (K . The line heads 101 (K, C, M, Y) of the present invention as described above. the

In addition, there are developing devices 44 (K, C, M, Y) for applying toner as a developer to an electrostatic latent image formed by the line head 101 (K, C, M, Y) to form a visible image (toner image). M, Y); the primary transfer device as the transfer device that sequentially transfers the toner images developed by the developing device 44 (K, C, M, Y) to the intermediate transfer belt 50 as the primary transfer object. roller 45 (K, C, M, Y); cleaning device 46 (K, C, M, Y). the

Here, each line head 101 (K, C, M, Y) is arranged along the generatrix of the photoreceptor drum 41 (K, C, M, Y) according to the array direction of the line heads 101 (K, C, M, Y). . Furthermore, the peak wavelength of the light emission energy of each line head 101 (K, C, M, Y) and the peak sensitivity wavelength of the photoreceptor 41 (K, C, M, Y) are set substantially constant. the

The developing devices 44 (K, C, M, Y) use, for example, a non-magnetic one-component toner as a developer, and the one-component developer is conveyed from a supply roller to a developing roller, and adhered to the surface of the developing roller is regulated by a restricting plate. The film thickness of the developer is deposited according to the potential level of the photoreceptor 41 (K, C, M, Y) by bringing the developing roller into contact with the photoreceptor 41 (K, C, M, Y) and pressing it. The developer is thereby developed as a toner image. the

The toner images of the respective colors of black, cyan, magenta, and yellow formed by such four-color monochromatic toner image forming positions pass through the primary transfer rollers 45 (K, C, M, Y) The printing biases are first transferred onto the intermediate transfer belt 50 in sequence, and the toner images that are sequentially superimposed on the intermediate transfer belt 50 to become a full-color toner image are secondarily transferred on the secondary transfer roller 66 to paper or the like for recording. The medium P passes through the fixing roller pair 61' as a fixing part, thereby fixing on the recording medium P, and is discharged to the discharge tray 68 formed on the upper part of the device by the discharge roller 62'. the

In addition, in FIG. 11 , 63 is a paper feed cassette for stacking and holding a plurality of recording media P, 64 is a pick-up roller for feeding the recording medium P one by one from the paper feed cassette 63 , and 65 is a paper feeder for specifying the direction of the recording medium P to the secondary rotation. A pair of gate rollers for supply timing of the secondary transfer portion of the printing roller 66 , 66 is a secondary transfer roller as a secondary transfer device forming a secondary transfer portion between the intermediate transfer belt 50 , and 67 is A cleaning plate as a cleaning device for removing toner remaining on the surface of the intermediate transfer belt 50 after the secondary transfer. the

Moreover, this invention relates to the optical system of the above line head (optical writing line head). the

First, the image-side aperture angle when given the light source luminosity of the light-emitting element 2 , the sensitivity characteristics of the image carrier 41 , the resolution of the image device, and the light transmission efficiency of the microlens 5 will be considered. the

Taking each light emitting element 2 as a light source 2, the distance between the light source 2 and the microlens 5 is sufficiently small, and the light source 2 is considered as an equal point light source. That is, the light source luminosity is expressed as follows. the

I＝Io(＝constant)

As shown in FIG. 12, when dF is the light beam emitted from the small area dA of the light emitting part of the light source (pixel) 2 and taken into the aperture of the optical system (microlens) 5, and the solid angle of the light source side of dF is Ω _o ,

dF＝∫IdΩ＝I _o Ω _o

Here, when the angle formed by the generatrix of the outer peripheral surface of the conical dF behind the light source 2 and the central ray is θ _o ,

Ω _o ＝2π{1—cos(θ _o )}＝4π{sin(θ _o /2)} ² …(3)

When substituting it into formula (2),

dF＝4πI _o {sin(θ _o /2)} ² …(4)

Assuming that the radius of the light source 2 is R _o , the light beam taken into the optical system per 1 dot (one light emitting element 2) is F _o ,

F _o =∫dFdA

＝4π ² I _o R _o ² {sin(θ _o /2)} ² …(5)

When the light beam Fi of every 1 point (imaging point 8 fixed with a light-emitting element 2) of the image plane (image carrier) 41 is set at the light transmittance of the optical system (microlens) 5 is η _lens ,

F _i =η _lens F _o ... (6)

When the lateral magnification of the optical system (microlens) 5 is assumed to be β, the beam focusing angle θ _i of the image plane and the spot diameter R _i of the image plane are,

θ _i ＝θ _o /|β| …(7)

R _i ＝|β|R _o ... (8)

In addition, when examining the paraxial,

sin(θ _o /2)=θ _o /2...(9)

If formulas (5), (7), (8), and (9) are substituted into formula (6) for arrangement, then

F _i ＝4π ² η _lens I _o (R _i /|β|) ² ·(|β|θ _i /2) ² ＝π ² η _lens I _o R _i ² θ _i ² …(10)

When it is solved for θ _i ,

θ _i ＝{F _i /(π ² η _lens I _o R _i ² )} ^0.5 …(11)

F _i is the amount of light on the image plane determined by the sensitivity characteristics of the image carrier 41, I _o is the luminosity of the light source (light emitting element) 2, R _i is the image plane point diameter determined by the resolution of the image forming device, and η _lens is determined by The number of lens surfaces and the value determined by the material of the microlens 5 are individually determined parameters.

Equation (11) indicates that the image-side aperture angle (half angle) θ _i is determined when Fi, I _o , R _i , and η _lens are determined.

However, in the present invention, as the microlens 5 constituting the microlens array 6, it is based on the premise that a lens system composed of two positive lenses arranged coaxially is configured, and the aperture stop is positioned between the two positive lenses. The front focus position of the positive lens L2 on the image side (photoreceptor (image surface) 41 side) is premised that the telecentricity is arranged on the image side. In this way, by configuring the microlens 5 with two positive lenses, the degree of freedom in aberration correction and the like is improved. In addition, by constituting the telecentricity on the image side, the image surface, that is, the surface of the photoreceptor (image surface) 41 is front and rear in the lens optical axis direction due to the vibration of the photoreceptor, etc. The position deviation of the imaging points corresponding to the element 2 does not occur, and the uneven spacing between the imaging points relative to the scanning lines drawn in the sub-scanning direction (the uneven spacing of the imaging points in the main scanning direction) does not occur. the

In addition, in the present invention, in order to reduce the diameter of the microlens 5, it is necessary to suppress the required effective diameter of each lens to be small. When the image side aperture angle (half angle) θ _i is determined by formula (11), in the optical system of the image side far point, when the second lens L2 (image side positive lens) in the two positive lenses forming the microlens 5 is determined ) to the distance of the image plane 41, the width of the main scanning direction of the image plane pixel group, although the necessary effective diameter of the second lens is determined, these two parameters cannot be set freely, and according to the interference of the microlens 5 and the photoreceptor 41 , and constraints such as interference with adjacent microlenses arranged in an array. When the diameter of the second lens is determined, at first, making the diameter of the aperture stop equal to or smaller than the diameter of the second lens is a condition for preventing the diameter of the microlens 5 from increasing. The diameter of the aperture stop is the same or smaller.

Next, the condition that the diameter of the aperture stop constituting each microlens 5 is equal to or smaller than the effective diameter of the second lens will be considered, and then the condition for keeping the effective diameter of the second lens small will be considered. the

Here, use is defined. Fig. 13 shows the image of the light-emitting element 2 on the image surface (image carrier) 41, that is, the group of imaging points 8 (corresponding to the image of the illuminant block 4) 80, and the relationship between the microlens 5 corresponding to the group 80 of each imaging point 8 diagram. In the case of this figure, in the microlens array 6 having the microlens 5 as a constituent element, the lens columns a, b, and c formed by arranging a plurality of microlenses 5 in the main scanning direction are arranged side by side in the sub scanning direction. The number m of is three. In this case, the rows A, B, and C of the luminous body blocks in which the plurality of luminous body blocks 4 are arranged in the main scanning direction are also provided in three corresponding columns. Moreover, the repetition interval phase of the main scanning direction of the lens columns a, b, c of the microlens 5 and the columns A, B, and C of the luminous body block is one m/m of the columns of the adjacent lens columns and luminous body blocks, In the case of this example, they are only arranged with a one-third offset from each other. the

The group 80 of imaging points 8 is the image plane pixel group, and the group of light emitting elements 2 in the corresponding luminous body block 4 is the light source pixel group. As shown in FIG. 13 , the image plane pixel group 80 in the main scanning direction The width is Wi, and in addition, the width of the main scanning direction of the light source pixel group is W0, the inner side of the effective diameter of the second lens L2 of the image side in the two positive lenses that constitute the microlens 5, that is, the effective area and the main scanning The distance between the effective regions of other lenses adjacent to each other is α (in FIG. ). the

Based on the paraxial formula before and after the second lens L2, the condition that the diameter of the aperture stop 11 is equal to or smaller than the effective diameter of the second lens L2 is obtained. the

Before the investigation, as shown in Fig. 14, each symbol of each parameter is defined. That is, the angle θ measured from the optical axis OO' is positive when it is rotated to the right, the image height h or above measured from the optical axis OO' is positive, and the distance on the optical axis OO' is measured in the left direction The right (direction of light travel) is positive, the subscript "in" after the symbol refers to the parameters on the object side, and the subscript "out" after the symbol refers to the parameters on the image side. the

First, referring to Fig. 15, when considering that the effective diameter of the lens is the maximum light passing height on the lens, since the diameter of the aperture stop 11 is approximately the same as the effective diameter of the second lens L2, as long as the end pixels of the pixel group 80 on the image plane form an image Among the light beams, the light rays farthest from the optical axis on the incident surface of the second lens L2 may be substantially parallel to the optical axis. On this condition, a paraxial type is established for the second lens L2 front and back. Suppose the angle formed by the incident light of the second lens L2 and the optical axis OO' is θ _2in , the angle formed by the outgoing light of the second lens L2 and the optical axis OO' is θ _2out , and the light on the second lens L2 When the passing height is h ₂ and the focal length of the second lens is f ₂ ,

θ _2out ＝θ _2in +h ₂ /f ₂ …(12)

Since the lens system (microlens) 5 is telecentric on the image side (aperture stop 11 is located on the front focal plane of the second lens L2) and converges at the image side aperture angle (half angle) θ _i , so θ _2out =θ _i , therefore,

θ _i ＝θ _2in +h ₂ /f ₂ ...(13)

Here, the incident ray is parallel to the optical axis OO′, so θ _2in =0. In addition, since the lens passing height of the outermost ray is the effective diameter (radius) of the lens, when the effective diameter of the second lens L2 is _D2 , the formula (13) is,

θ _i =0+(D ₂ /2)/f ₂ ...(14)

When it is solved for _f2 ,

f ₂ ＝D ₂ /(2θ _i ) …(15)

Equation (15) is a conditional expression that the incident light to the second lens L2 is parallel to the optical axis O-O', that is, a condition that the diameter of the aperture stop 11 is equal to the effective diameter of the second lens L2. the

When f ₂ is smaller than the right side of the formula (15), the angle θ _2in formed with the optical axis of the incident ray from the formula (13) to the second lens L2 is negative. It means that the diameter of the aperture stop 11 becomes smaller as the light rays travel away from the optical axis OO'. Therefore, the following formula is obtained as a condition that the diameter of the aperture stop 11 is substantially equal to or smaller than the effective diameter of the second lens L2.

f ₂ ≤ D ₂ /(2θ _i ) …(16)

Taking the distance from the main surface of the rear side of the second lens L2 to the image plane 41 as S _i , the width (full width) of the image plane pixel group 80 on the image plane 41 is W _i , the lens in the main scanning direction of the microlens array 6 The number of parallel rows in the sub-scanning direction is m, and the effective diameter of the second lens L2 is D ₂ . After the lens row is formed, the range in which _Wi can be obtained is obtained, and the necessary effective diameter of the second lens L2 is suppressed to be small. Conditions are inspected.

The inter-lens distance in the lens row is expressed as (mW _i ) (FIG. 13), but if it is smaller than the effective diameter of the second lens L2, the lens array (lens row) is not arranged, therefore,

mW _i ≥ D ₂ …(17)

In the manufacture of the lens row, clearance may be required for the effective diameters of the adjacent lenses 5 within the lens row. As the clearance, when α (positive number) (Fig. 13) is added to formula (15),

mW _i ≥ D ₂ +α...(18)

When formula (16) and formula (18) are solved for D ₂ respectively,

2θ _i f ₂ ≤ D ₂ ...(19)

D ₂ ≤mW _i —α…(20)

When formula (19) and formula (20) are connected via D ₂ and f ₂ is arranged,

f ₂ ≤(mW _i —α)/(2θ _i )…(21)

Next, the effective diameter _D2 of the second lens is investigated. The effective radius of the lens must be larger than the height of light beams focused on the end face pixels of the image face pixel group 80 on the lens. Since it is the far point on the image side,

D ₂ /2≥2≥W _i /2+S _i θ _i …(22)

Multiply both sides of formula (22) by 2,

D ₂ ≥W _i +2S _i θ _i …(23)

The formula (23) and the previously derived formula (20) are plotted as the horizontal axis W _i and the vertical axis D ₂ ,

As shown in FIG. 16 , the oblique line range in FIG. 16 satisfies the two equations. the

When obtaining the intersection point of the two straight lines in Fig. 16 represented by equation (20) and equation (23), and obtaining the range of W _I corresponding to the hatched portion,

W _i ≥ 2S _i θ _i /(m—1)+α/(m—1)…(23)

Equation (24) is a condition for arranging the second lenses L2 in a row, and if it is not satisfied, the effective ranges of adjacent conditions interfere with each other. the

By determining the focal length _f2 of the second lens according to the formula (21) while satisfying the formula (24), the diameter of the aperture stop 11 and the upper limit value of the effective diameter _D2 of the second lens determined by the formula (20) can be made approximately the same or less.

Regarding the configuration of the first lens L1, the optical path diagram from FIG. 17 shows that as the distance between the first lens L1 and the aperture stop 11 increases, the effective diameter of the first lens L1 increases compared to the diameter of the aperture stop 11. Therefore, It is sufficient to arrange the distance from the aperture stop 11 to the first lens L1 so that the effective diameter of the first lens L1 is not larger than the effective diameter of the second lens L2. Nearby, the difference between the effective diameter of the first lens L1 and the diameter of the aperture stop 11 can be suppressed to be small, and the diameter of the first lens L1 can be prevented from increasing. the

Once the arrangement of the first lens L1 is determined, the focal length of the first lens L1 and the distance from the light source surface (luminous body array, object surface) are determined intentionally so that the magnification β of the optical system (microlens) 5 becomes a desired value. 1 to the distance of the first lens L1. the

In addition, it is shown from FIG. 16 that to reduce the effective area D ₂ of the second lens as much as possible, it is only necessary to reduce the pixel group width W _i of the image plane. The effective diameter _D2 of the second lens can be suppressed to be small by setting W _i within the range of Equation (24) to the minimum value satisfying Equation (20) with respect to _D2 obtained from the real ray trace. Ideally, when W _i is determined by the equation (24) connected by an equal sign, the effective diameter D ₂ of the second lens is the smallest.

W _i =2S _i θ _i /(m—1)+α/(m—1)...(24)'

Next, as shown in FIG. 18, when the second lens L2 constituting the microlens 5 is formed by a convex-flat thick-walled lens, focusing on the light passing through the outermost diameter of the second lens L2, the reduction of the diameter of the aperture stop 11, the first A condition of the effective diameter of lens L1 is investigated. the

As shown in FIG. 19 , the outermost ray passage height h ₂ of the light beam converged on the end pixels of the image plane pixel group 80 is represented by the following formula with a refractive index of 1 in air.

h ₂ ＝W _i /2+d ₂ 'θ _i +e _t2 θ _a

＝W _i /2+d ₂ 'θ _i +e _t2 θ _b /n ₂

＝W _i /2+d ₂ 'θ _i +e _t2 θ _i /n ₂

＝W _i /2+(d ₂ '+e _t2 /n ₂ )θ _i ...(25)

Here, d ₂ ′ is the distance from the plane on the image side of the second lens L2 to the image plane 41, and e _t2 is the outermost ray of the light beam focused on the end pixel of the image plane pixel group 80 incident on the second lens L2 The distance between the point on the convex surface on the object side and the optical axis OO' direction of the plane on the image side of the second lens L2 (thickness of the effective diameter of the second lens), n ₂ is the refractive index of the second lens L2, θ _a and θ _b are the respective incident angles and refraction angles of the outermost light rays to the image-side plane of the second lens L2 ( FIG. 19 ).

D ₂ ≥2h ₂ to

D ₂ ≥W _i +2(d ₂ '+e _t2 /n ₂ )θ _i …(26)

Comparing the formula (26) with the formula (23), it is found that S _I corresponds to (d ₂ ′+e _t2 /n ₂ ). When using it in formula (24) and rearranging,

W _i ≥ 2(d ₂ ′+e _t2 /n ₂ )θ _i /(m-1)+α/(m-1) ... (27).

When the second lens L2 is a convex-flat thick-walled lens, the conditions for making the diameter of the aperture stop 11 substantially the same as or greater than the effective diameter _D2 of the second lens are given by formula (21), formula (27) give. In addition, by arranging the first lens L1 and the aperture stop 11 close to each other, the effective diameter of the first lens L1 is suppressed to be small.

Ideally, the second lens effective diameter D ₂ can be minimized by giving the image plane pixel group width W _i by the sub-equation of the equation (27) connected by an equal sign.

W _i ＝2(d ₂ '+e _t2 /n ₂ )θ _i /(m-1)+α/(m-1) ...(27)'

In addition, in the above description, the lens system 5 composed of the two positive lenses L1 and L2 is based on the premise that the focal length and focal position in the main scanning direction and the sub scanning direction are axisymmetric lens system, but it constitutes a microlens array The lens system 5 of 6 is composed of an anamorphic optical system, and a structure in which the focal length and magnification are different in the main scanning direction and the sub scanning direction may be used. In this case, the aperture stop 11 may be arranged at the front focal position of the positive lens L2 so as to be telecentric on the image side in the main scanning direction (main scanning section). In this case, values of the main scanning direction cross section are used for the focal length f ₂ of the second lens L2, the distance S _i from the rear main surface of the second lens L2 to the image plane 41, and the like.

In addition, in the present invention, image-side telecentricity means not limited to making the aperture stop 11 located at the front focus position of the second lens L2 among the two positive lenses L1 and L2 constituting the microlens 5, and making the incident light on the image plane In the case where the chief ray of each pixel in the image plane pixel group 80 of 41 is completely parallel to the optical axis OO', it also includes the fact that the chief ray of the light-emitting element image incident on the end of the main scanning direction is located within ± of the optical axis OO'. Within 1° (approximately telecentric on the image side). the

Next, an example of a remote optical writing line head to which the above-mentioned present invention is applied will be described. the

FIG. 20 is a perspective view showing part of the structure of the line head of the optical write head according to this embodiment, and FIG. 21 is a cross-sectional view along the sub-scanning direction. In addition, FIG. 22 is a plan view showing the arrangement of the luminous body array and the microlens array in this case. In addition, FIG. 23 is a diagram showing the correspondence relationship between one microlens and the corresponding luminous body block. the

In this embodiment, as in the case of FIG. 4 and FIG. 7 , four light-emitting element rows 3 in which four light-emitting elements 2 made of organic EL elements are arranged in the main scanning direction are formed in two rows in the sub-scanning direction to make one. The illuminant block 4 is arranged in multiples in the main scanning direction and the sub-scanning direction to form the illuminant array 1, and the illuminant block 4 is arranged in a zigzag shape in the sub-scanning direction staggered from the front position of the main scanning direction. In the example of FIG. 20 , the luminous body blocks 4 are arranged in three rows in the sub-scanning direction. This luminous body array 1 is formed on the back surface of the glass substrate 20 and is driven by a driving circuit formed on the same back surface of the glass substrate 20 . In addition, the organic EL element (light emitting element 2 ) on the back surface of the glass substrate 20 is sealed with a sealing member 27 . the

The glass substrate 20 is inserted into the support hole 22 provided in the elongated case 21 , covers the back cover 23 , and is fixed by the fixing metal fitting 24 . Insert the positioning pins 25 provided at both ends of the elongated housing 21 into the positioning holes of the main body of the image forming apparatus opposite, and simultaneously screw the fixing screws into the image forming device through the screw insertion holes 26 provided at both ends of the elongated housing 21. The screw holes of the device main body are fixed, whereby the optical writing line head 101 is fixed at a predetermined position. the

In addition, on the surface of the glass substrate 20 of the housing 21, through the first spacer 71, the center of each illuminant block 4 of the illuminant array 1 and the positive lens L1 are arranged in an aligned manner, and the positive lens L1 is used as a constituent element. The first microlens array 61, and the aperture 31 (Fig. plate 30, and then fix the second microlens array 62 with the positive lens L2 as a constituent element in such a way that the center of each luminous body block 4 of the luminous body array 1 and the positive lens L2 are aligned through the third spacer 73 thereon. . the

In this way, the lens array of the microlens 5 projecting the light emitting element row of each luminous body block 4 is constituted by a combination of the first microlens array 61 and the second microlens array 62 . the

And, based on the present invention, the aperture plate 30 is arranged at the object side (front side) focus position of the positive lens L2 constituting the second microlens array 62 to coincide with each other, and the positive lens L2 is set to satisfy the formula (21). The focal length is f ₂ , and the width (full width) W _i of the image of the illuminant block 4 on the photoreceptor (image surface) 41 along the main scanning direction is set so as to satisfy the formula (24). The aperture plate 30 is shown in detail in FIGS. 24 and 25 . 24 is a plan view of the aperture plate 30 arranged corresponding to the illuminant block 4 of the illuminant array 1 , and FIG. 25 is a view showing the aperture 31 of the aperture plate 30 relative to one illuminant block 4 . On the diaphragm plate 30, the respective centers (optical axes) of the microlenses 5 constituted by the positive lens L1 and the positive lens L2 and the center of the illuminant block 4 are arranged to be provided with apertures 31. In this embodiment, each aperture The shape of 31 is circular, but may be an aperture shape such as an ellipse or a rectangle that limits at least the aperture in the main scanning direction.

In the above embodiments, the light writing line head 101 configured to utilize the so-called bottom emission of the light emitted by the outermost light-emitting element 21 on the surface of the glass substrate 20 using the organic EL element disposed on the back surface of the glass substrate 20, but It is also possible to use an EL element and an LED in which the light emitting element 2 is arranged on the surface side of the substrate. the

However, in the above description, as shown in FIG. 7 and FIG. 22, the luminous body array 1 forms a luminous body formed by arranging a plurality of light-emitting element columns 3 in the sub-scanning direction in one or more rows in the sub-scanning direction. block 4, and set the microlens 5 corresponding to each illuminant block 4. However, the light-emitting elements 2 are arranged in long rows continuously at fine intervals in the main scanning direction, and only the light-emitting element groups corresponding to the light-emitting body blocks 4 therein are controlled to emit light. The illuminant elements between the groups are controlled so that they do not emit light, thereby constituting the illuminant blocks 4 similar to those in FIGS. 7 and 22 . FIG. 26 shows a diagram corresponding to FIG. 22 in this case. That is, the outermost luminous body array 1 arranges the light-emitting elements in the main scanning direction as long column-shaped light-emitting element rows 3' continuous at fine equal intervals, and the microlenses 5 passing through them are only aligned with the imaging points 8. Light emission control is performed for the group of light emitting elements 2' (indicated by ○) related to the formation of the light emitting element 2', and light emission control is not performed for the group of light emitting elements 2" (indicated by ●) existing between the groups of light emitting elements 2'. It can be configured in the above manner Each illuminant block 4. In the case of Fig. 26, three columns of microlenses 5 are arranged in the main scanning direction, and two columns of light-emitting element columns 3' are formed in the sub-scanning direction in a manner corresponding to each column of the microlenses 5, and the The light-emitting elements 2 in the two light-emitting element rows 3' are arranged in a zigzag shape, so that only four light-emitting elements 2' in each light-emitting element row 3' emit light, and the eight light-emitting elements 2 between the four light-emitting elements 2' "Control in a way that doesn't shine. the

In addition, the microlenses 61 and 61 used in the optical writing line head 101 of the present invention can be used regardless of the conventionally known structure. A plan view along the main scanning direction when the lenses L1 and L2 are coaxially aligned and combined to form an array of microlenses 5 . In this example, the microlens arrays 61, 62 are aligned on one surface (object side) of the glass substrate 34, and the lens surfaces 35 made of transparent lenses are integrally molded to form the microlenses L1, L2. In this case, by making the surface on the image side of the second microlens array 62 flat, for example, when the microlens array is used as a line head of an image forming apparatus, even if the toner of the developer is scattered and the valve is covered in the microlens array It can also be easily cleaned on a flat surface, improving cleanliness. the

Next, specific numerical examples of the optical system used in the above-mentioned examples are shown as examples 1 to 4.

28 (a), (b) are cross-sectional views of the main scanning direction and the sub-scanning direction of the optical system corresponding to one microlens 5 of Embodiment 1, and are examples as follows: The glass substrate is arranged, and the microlens 5 is made into a synthetic lens system composed of a biconvex positive lens L1 and a biconvex positive lens L2, and an aperture plate 30 is arranged at the object side (front side) focal point of the biconvex positive lens L2. The telecentricity is set on the image side, the focal length _f of the second lens L2 satisfies the formula (21), the image plane pixel group width _Wi satisfies the formula (24), and the effective diameter D of the second lens _L2 is lower than the formula (20 ), the diameter of the aperture 31 of the diaphragm plate 30 is suppressed to be smaller than the effective diameter _D2 of the second lens L2.

The numerical data of this embodiment are shown below, from the illuminant block 4 side toward the photoreceptor (image surface) 41 side in order, r ₁ , r ₂ ... are the curvature radii (mm) of each optical surface, d ₁ , d ₂ ... is the interval (mm) between each optical surface, n _d1 , n _d2 ... are the refractive indices of the d-line of each transparent medium, and υ _d1 , υ _d2 ... are the A multiples of each transparent medium. In addition, r ₁ , r ₂ ... also represent optical surfaces, optical surface r ₁ is the illuminant block (object surface) 4, optical surfaces r ₂ , r ₃ are the object-side surface and the image-side surface of the biconvex positive lens L1 , the optical surface r ₄ is the aperture 31 of the diaphragm plate 30, the optical surfaces r ₅ and r ₆ are the object side surface and the image side surface of the biconvex positive lens L2, and the optical surface r ₇ is the photoreceptor (image surface) 41 .

29 (a), (b) are cross-sectional views of the main scanning direction and the sub-scanning direction of the optical system corresponding to one microlens 5 of Embodiment 2, and are examples as follows: The glass substrate is arranged, and the microlens 5 is made into a synthetic lens system composed of a biconvex positive lens L1 and a biconvex positive lens L2, and an aperture plate 30 is arranged at the object side (front side) focal point of the biconvex positive lens L2. The telecentricity is set on the image side, the focal length _f of the second lens L2 satisfies the formula (21), the image plane pixel group width _Wi satisfies the formula (24), and the effective diameter D of the second lens _L2 is lower than the formula (20 ), the diameter of the aperture 31 of the diaphragm plate 30 is suppressed to be smaller than the effective diameter _D2 of the second lens L2.

In this embodiment 2, after the aperture plate 30 is set as the same as that of embodiment 1, after making the double convex positive lens L1 close to the aperture plate 30, the light magnification is adjusted in the same way as that of the embodiment 1. The curvature of the incident surface, the exit surface, and the distance from the light-emitting element 2 of the illuminant block 4 to the incident surface of the biconvex positive lens L1. Compared with Example 1, the effective diameter of the first adjustment L1 is closer to the diameter of the diaphragm aperture 31 and is smaller than the effective diameter of the second adjustment L2. the

The numerical data of this embodiment are shown below, from the illuminant block 4 side toward the photoreceptor (image surface) 41 side in order, r ₁ , r ₂ ... are the curvature radii (mm) of each optical surface, d ₁ , d ₂ ... is the interval (mm) between each optical surface, n _d1 , n _d2 ... are the refractive indices of the d-line of each transparent medium, and υ _d1 , υ _d2 ... are the A multiples of each transparent medium. In addition, r ₁ , r ₂ ... also represent optical surfaces, optical surface r ₁ is the illuminant block (object surface) 4, optical surfaces r ₂ , r ₃ are the object-side surface and the image-side surface of the biconvex positive lens L1 , the optical surface r ₄ is the aperture 31 of the diaphragm plate 30, the optical surfaces r ₅ and r ₆ are the object side surface and the image side surface of the biconvex positive lens L2, and the optical surface r ₇ is the photoreceptor (image surface) 41 .

30 (a), (b) are cross-sectional views in the main scanning direction and the sub-scanning direction of the optical system corresponding to one microlens 5 of Embodiment 3, and are examples as follows: The glass substrate is arranged, and the microlens 5 is made into a synthetic lens system composed of a biconvex positive lens L1 and a biconvex positive lens L2, and an aperture plate 30 is arranged at the object side (front side) focal point of the biconvex positive lens L2. The telecentricity is set on the image side, the focal length _f of the second lens L2 satisfies the formula (21), the image plane pixel group width _Wi satisfies the formula (24), and the effective diameter D of the second lens _L2 is lower than the formula (20 ), the diameter of the aperture 31 of the diaphragm plate 30 is suppressed to be smaller than the effective diameter _D2 of the second lens L2.

In this embodiment 3, in the same optical system as that of embodiment 2, the value of the overall width W _i of the following pixel groups will be determined by formula (24)', compared with embodiment 2, the effective diameter of the second adjustment L2 is suppressed for small.

The numerical data of this embodiment are shown below, from the illuminant block 4 side toward the photoreceptor (image surface) 41 side in order, r ₁ , r ₂ ... are the curvature radii (mm) of each optical surface, d ₁ , d ₂ ... is the interval (mm) between each optical surface, n _d1 , n _d2 ... are the refractive indices of the d-line of each transparent medium, and υ _d1 , υ _d2 ... are the A multiples of each transparent medium. In addition, r ₁ , r ₂ ... also represent optical surfaces, optical surface r ₁ is the illuminant block (object surface) 4, optical surfaces r ₂ , r ₃ are the object-side surface and the image-side surface of the biconvex positive lens L1 , the optical surface r ₄ is the aperture 31 of the diaphragm plate 30, the optical surfaces r ₅ and r ₆ are the object side surface and the image side surface of the biconvex positive lens L2, and the optical surface r ₇ is the photoreceptor (image surface) 41 .

31 (a), (b) are cross-sectional views of the main scanning direction and the sub-scanning direction of the optical system corresponding to one microlens 5 of Embodiment 4, and are examples as follows: The glass substrate is arranged, and the microlens 5 is made into a synthetic lens system composed of a biconvex positive lens L1 and a biconvex positive lens L2, and an aperture plate 30 is arranged at the object side (front side) focal point of the biconvex positive lens L2. The telecentricity is set on the image side, the focal length _f of the second lens L2 satisfies the formula (21), the image plane pixel group width _Wi satisfies the formula (24), and the effective diameter D of the second lens _L2 is lower than the formula (20 ), the diameter of the aperture 31 of the diaphragm plate 30 is suppressed to be smaller than the effective diameter _D2 of the second lens L2.

As in this embodiment, by using both the first positive lens L1 and the second positive lens L2 as convex plane lenses, the lens formation surface formed as the microlenses 61 and 62 is only one-sided, which has the advantage of being easy to manufacture. the

In addition, by making the surface on the image side of the second positive lens L2 flat, the entire surface on the image side of the second microlens array 62 constituting the lens array of the microlens 5 can be made flat, for example, as a line head of an image forming apparatus. When the microlens array is used, even if the toner of the developer scatters and adheres to the surface of the microlens array, it can be easily cleaned and the cleanability is improved. the

The numerical data of this embodiment are shown below, from the illuminant block 4 side toward the photoreceptor (image surface) 41 side in order, r ₁ , r ₂ ... are the curvature radii (mm) of each optical surface, d ₁ , d ₂ ... is the interval (mm) between each optical surface, n _d1 , n _d2 ... are the refractive indices of the d-line of each transparent medium, and υ _d1 , υ _d2 ... are the A multiples of each transparent medium. In addition, r ₁ , r ₂ ... also represent optical surfaces, optical surface r ₁ is the illuminant block (object surface) 4, optical surfaces r ₂ , r ₃ are the object-side surface and the image-side surface of convex plano positive lens L1, The optical surface r ₄ is the aperture 31 of the diaphragm plate 30 , the optical surfaces r ₅ and r ₆ are the object-side and image-side surfaces of the convex-planar positive lens L2 , and the optical surface r ₇ is the photoreceptor (image surface) 41 . In addition, the object-side surfaces r ₂ and r ₅ of the convex and planar positive lens L1 and the convex planar positive lens L2 are both aspheric surfaces, and when the distance from the optical axis is set as r as the aspheric surface shape, it is given by

Cr ² /[1+√{1—(1+K)c ² r ² }]+Ar ⁴ +Br ⁶ means. Among them, c is the curvature on the optical axis (1/r), K is the Konic coefficient, A is the fourth-order aspheric coefficient, and B is the sixth-order aspheric coefficient. In the following numerical data, K ₂ and K ₅ are the Konic coefficients of the object-side surface r ₂ of the convex-planar positive lens L1 and the object-side surface r ₅ of the convex-planar positive lens L2 respectively, and A ₂ and A ₅ are the convex-planar positive lens The quartic aspheric coefficients of the surface r ₂ on the object side of the lens L1 and the surface r ₅ on the object side of the convex plano positive lens L2, B ₂ and B ₅ are the object side surface r ₂ of the convex plano positive lens L1 and the convex plano positive lens Sixth order aspheric coefficient of surface r ₅ on the object side of L2.

Example 1

r ₁ = ∞ (object plane) d ₁ = 3.4265 r ₂ = 1.8293 d ₂ = 0.4000n _d1 = 1.5168 υ _d1 = 64.2 r ₃ = -2.6200d ₃ = 0.5000 r ₄ = ∞ (aperture) d ₄ = 1.5000

r ₅ =0.9310 d ₅ =0.4000 n _d2 =1.5168 υ _d2 =64.2 r ₆ =—6.1348d ₆ =0.8000 r ₇ =∞ (image plane)

Use wavelength 632.5nm

Image side aperture angle (half angle) θ _i 0.1745rad(10deg)

Number of lens columns m 3

The interval α between the effective areas of the second lens is 0.1 mm or more

The distance S _i from the main surface on the image side of the second lens to the image surface is 1.0337mm

Horizontal magnification β —0.5

Full width of light source pixel group W _o 0.700mm

Full width W _i of image plane pixel group 0.350mm

(When substituting into formula (24), W _i ≥0.2304mm)

Second lens focal length f ₂ 1.6mm

(When substituting into formula (24), f ₂ ≤2.722mm)

The effective diameter of the first lens (twice the maximum ray passing height on the lens for real ray tracing) D ₁ 0.778mm

Aperture stop diameter 0.547mm

The effective diameter of the second lens (twice the height of the maximum light passing through the lens on the real ray tracing lens) D ₂ 0.708mm

(When substituting into formula (24), D ₂ ≤0.950mm)

Example 2

r ₁ =∞ (object plane) d ₁ =2.9909 r ₂ =7.3392 d ₂ =0.4000n _d1 =1.5168 υ _d1 =64.2 r ₃ =—1.1571 d ₃ =0.1000 r ₄ =∞ (aperture) d ₄ =1.5000

r ₅ =0.9310 d ₅ =0.4000 n _d2 =1.5168 υ _d2 =64.2 r ₆ =—6.1348d ₆ =0.8000 r ₇ =∞ (image plane)

Use wavelength 632.5nm

Image side aperture angle (half angle) θ _i 0.1745rad(10deg)

Number of lens columns m 3

The interval α between the effective areas of the second lens is 0.1 mm or more

The distance S _i from the main surface on the image side of the second lens to the image surface is 1.0337mm

Horizontal magnification β — 0.5

Full width of light source pixel group W _o 0.700mm

Full width W _i of image plane pixel group 0.350mm

(When substituting into formula (24), W _i ≥0.2304mm)

Second lens focal length f ₂ 1.6mm

(When substituting into formula (24), f ₂ ≤2.722mm)

The effective diameter of the first lens (twice the height of the maximum light passing through the lens on the real ray tracing lens) D ₁ 0.609mm

Aperture stop diameter 0.542mm

The effective diameter of the second lens (twice the height of the maximum light passing through the lens on the real ray tracing lens) D ₂ 0.709mm

(When substituting into formula (24), D ₂ ≤0.95mm)

Example 3

r ₁ =∞ (object plane) d ₁ =2.9909 r ₂ =7.3392 d ₂ =0.4000n _d1 =1.5168 υ _d1 =64.2 r ₃ =—1.1571 d ₃ =0.1000 r ₄ =∞ (aperture) d ₄ =1.5000

r ₅ =0.9310 d ₅ =0.4000 n _d2 =1.5168 υ _d2 =64.2 r ₆ =—6.1348d ₆ =0.8000 r ₇ =∞ (image plane)

Use wavelength 632.5nm

Image side aperture angle (half angle) θ _i 0.1745rad (10deg)

Number of lens columns m 3

The interval between the effective areas of the second lens α is 0.1mm or more

The distance S _i from the main surface on the image side of the second lens to the image surface is 1.0337mm

Horizontal magnification β —0.5

Full width of light source pixel group W _o 0.700mm

Full width W _i of image plane pixel group 0.350mm

(When substituting into formula (24), W _i ≥0.2304mm)

Second lens focal length f ₂ 1.6mm

(When substituting into formula (24), f ₂ ≤2.722mm)

The effective diameter of the first lens (twice the height of the maximum light passing through the lens on the real ray tracing lens) D ₁ 0.580mm

Aperture stop diameter 0.542mm

The effective diameter of the second lens (twice the maximum light passing height on the lens of real ray tracing) D ₂ 0.590mm

(When substituting into formula (24), D ₂ ≤0.95mm)

Example 4

r ₁ =∞(object plane) d ₁ =2.8070 r ₂ =1.1819 d ₂ =1.1000n _d1 =1.5168 υ _d1 =64.2

K ₂ =—1.1448

A ₂ =—0.0204

B ₂ =0.0292

r ₃ =∞ d ₃ =0.0500

r ₄ =∞(aperture) d ₄ =1.7254

r ₅ ＝0.9272 (aspheric surface) d ₅ ＝1.1000 n _d2 ＝1.5168 υ _d2 ＝64.2

K ₅ =—0.0680

A ₅ =—0.1373

B ₅ =—0.1947

r ₆ =∞ d ₆ =0.8000

r ₇ =∞ (image plane)

Use wavelength 632.5nm

Image side aperture angle (half angle) θ _i 0.2364 rad(13.54deg)

Number of lens columns m 3

The interval between the effective area of the second lens α 0.1mm

Distance d ₂ ' from the main surface on the image side of the second lens to the image surface 0.8mm

Thickness of the second lens effective diameter part e _t2 0.93800mm

Second lens refractive index n ₂ 1.5151

Horizontal magnification β — 0.666

Full width of light source pixel group W _O 0.600mm

Image surface pixel group full width W _i 0.400mm

(When substituting into formula (27), W _i ≥0.385mm)

Second lens focal length f ₂ 1.8mm

(When substituting into formula (21), f ₂ ≤2.326mm)

The effective diameter of the first lens (twice the height of the maximum light passing through the lens on the real ray tracing lens) D ₁ 1.074mm

Aperture stop diameter 0.435mm

The effective diameter of the second lens (twice the height of the maximum light passing through the lens on the real ray tracing lens) D ₂ 1.087mm

(When substituting into formula (20), D ₂ ≤1.100mm)

But, based on the optical system of the optical writing line head of the present invention above, in order to prevent the light from the illuminant block 4 from entering the specific microlens 5 of the microlens array from entering the optical path of the adjacent microlens 5, glare occurs In some cases, preferably one or more glare diaphragm plates are disposed between the illuminant array 1 and the diaphragm plate 30 . FIG. 32 shows a cross-sectional view along an example of the main scanning direction in this case. In this case, six glare diaphragm plates 32 are arranged parallel to the diaphragm plate 30 at intervals, and each glare diaphragm plate 32 has an aperture 33 corresponding to the aperture 31 of the diaphragm plate 30 . The intended aperture stop in the present invention refers to the aperture 31 of the stop plate 30 , not the aperture 33 of such a glare stop plate 32 . the

The line head of the present invention and the image forming apparatus using the line head have been described above based on their principles and examples, but the present invention is not limited to these examples, and various modifications are possible.

Claims (8)

1. wardrobe is characterized in that having:

Positive lens system, it has the lens of two positive refracting powers;

Picture side lens arra, its by in described two lens as the side lens first direction and a plurality of the forming of second direction configuration;

The object side lens arra, it disposes a plurality of forming by the object side lens in described two lens at described first direction and described second direction;

Luminous body array, it is to have disposed a plurality of light-emitting components at the object side that described positive lens is with respect to a described positive lens; With

Aperture plate, it is configured between described picture side lens arra and the described object side lens arra, forming aperture diaphragm becoming the mode heart far away or the heart roughly far away as side,

Become as side the heart far away be meant at the image space chief ray parallel with optical axis, become as side roughly the heart far away be meant the image space chief ray be positioned at optical axis ± 1 ° in,

With described as the side lens arra be made as m at the columns of the lens of described second direction configuration, be made as α at two described intervals that described first direction adjoins each other in the effective coverage as the side lens, described positive lens system be θ as the lateral aperture angle _i, a plurality of light-emitting components of being disposed with respect to described positive lens system image planes on picture be that the width at described first direction of a plurality of light-emitting component pictures is made as W _i, described focal length as the side lens is made as f ₂, be made as S as the side interarea to described distance as the side lens from described as side _iThe time, have following condition:

f ₂≤(mW _i-α)/(2θ _i) …(21)

W _i≥2S _iθ _i/(m-1)+α/(m-1) …(24)

And described aperture angle is a half-angle, and described width is a full duration.

2. wardrobe as claimed in claim 1 is characterized in that, the width W at described first direction of described a plurality of light-emitting component pictures _iHave following condition:

W _i＝2S _iθ _i/(m-1)+α/(m-1) …(24)’。

3. wardrobe is characterized in that having:

Positive lens system, it has the lens of two positive refracting powers;

Picture side lens arra, its by in described two lens as the side lens first direction and a plurality of the forming of second direction configuration;

The object side lens arra, it disposes a plurality of forming by the object side lens in described two lens at described first direction and described second direction;

Luminous body array, it is to have disposed a plurality of light-emitting components at the object side that described positive lens is with respect to a described positive lens; With

Aperture plate, it is configured between described picture side lens arra and the described object side lens arra, forming aperture diaphragm becoming the mode heart far away or the heart roughly far away as side,

Become as side the heart far away be meant at the image space chief ray parallel with optical axis, become as side roughly the heart far away be meant the image space chief ray be positioned at optical axis ± 1 ° in,

Described picture side lens are that the protruding plano lens on plane constitutes by the face as side,

Be made as m, will be made as α, be made as θ as the lateral aperture angle in described interval as the columns of side lens arra described at the lens of described second direction configuration two that described first direction adjoins each other with what described positive lens was in the effective coverage as the side lens _i, a plurality of light-emitting components that will be disposed with respect to described positive lens system image planes on picture be that the width at described first direction of a plurality of light-emitting component pictures is made as W _i, described focal length as the side lens is made as f ₂, will be made as d as side plane to the distance of image planes as the side lens from described ₂', will be that the outermost light at the light beam of the light-emitting component picture institute pack of the end of described first direction of a plurality of light-emitting component pictures, point and the described distance as the optical axis direction on the plane of side as the side lens that incides the convex surface of described object side as the side lens are made as e with the picture of the image planes of a plurality of light-emitting components of described positive lens system corresponding configuration _T2, be n with the refractive index of described picture side lens ₂The time, have following condition:

f ₂≤(mW _i-α)/(2θ _i) …(21)

W _i≥2(d ₂’+e _t2/n ₂)θ _i/(m-1)+α/(m-1) …(27)，

And described aperture angle is a half-angle, and described width is a full duration.

4. wardrobe as claimed in claim 3 is characterized in that, the width W of the described first direction of described a plurality of light-emitting component pictures _iHave following condition:

W _i＝2(d ₂’+e _t2/n ₂)θ _i/(m-1)+α/(m-1)。

5. as each described wardrobe in the claim 1～4, it is characterized in that described aperture plate is disposed at the front side focus face of described picture side lens.

6. as each described wardrobe in the claim 1～4, it is characterized in that described aperture plate disposes near described object side lens.

7. wardrobe as claimed in claim 5 is characterized in that, described aperture plate disposes near described object side lens.

8. image processing system is characterized in that having:

Latent image carrier;

The electro-mechanical part that described latent image carrier is charged;

Each described wardrobe in the claim 1～7; With

Development section with described latent image carrier development.

Images