JP2004276621A - Optical apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical apparatus suitable for a high-resolution optical printhead. <P>SOLUTION: The optical printhead is provided with: light emitting elements 3 which are constituted such that a plurality of light emitting parts 35 are divided into a plurality of groups, and a plurality of common electrodes 37a and 37b connected to the light emitting parts 35 for each group and a plurality of individual electrodes 38 connected to the light emitting parts 35 belonging to different groups are provided; and drive circuits to drive the light emitting elements. In the drive circuit, a driving IC 4 for driving, in which a first drive part to select the plurality of individual electrodes 38 and a second drive part to select the plurality of common electrodes are integrally arranged, is provided corresponding to each light emitting element 3. Wiring 5 to connect both parts is arranged between the light emitting element and the driving IC 4. The wiring 5 comprises a direct connection structure by a wire bonding wire. The driving IC 4 is treated in the same way as a conventional static driving IC through this constitution. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to an optical device useful as a light source such as an optical printer.

  As shown in Patent Document 1, a light emitting element (array) used in a conventional optical print head is provided with individual electrodes on the element surface side in a one-to-one correspondence with a plurality of light emitting parts, and common to each light emitting part. Since the electrodes are provided on the back side of the device, time-division driving cannot be performed in one device. Since it is not possible to perform time-division driving, it is necessary to provide the same number of individual electrodes as the number of light-emitting portions. There was a problem that connection became difficult.

  In order to solve such a problem, Patent Document 2 proposes a light-emitting element that can be driven in a time-division manner. That is, the plurality of light emitting units on the light emitting element are divided into M (2 to 3) groups, M common electrodes are provided so as to be connected to the light emitting units of each group, and M light emitting units belonging to different groups are provided. A light-emitting element including M × N light-emitting portions by providing N connected individual electrodes has been proposed. According to this light emitting element, the number of individual electrodes can be reduced to 1 / M of the conventional one by selecting the M common electrodes in a time-division manner, so that the connection with the driving IC is facilitated. Can be.

  FIG. 7 shows an example of a circuit configuration assumed based on a conventional dynamic driving method when a time-division driving-compatible light emitting element as proposed in the above publication is used. Here, each light emitting element 100 divides a plurality of light emitting portions provided on the surface thereof into two groups, connects two common electrodes to the plurality of light emitting portions belonging to each group, and belongs to separate groups. It is assumed that individual electrodes are connected to one set of light emitting units, and each individual electrode is arranged on one side of the light emitting element. The light emitting element 100 is connected to the driving IC 200 having the same number of terminals as the number of individual electrodes by wire bonding in a one-to-one manner, and has two selection ICs 300 for selecting the common electrode. It is connected via a ground line 400.

According to the circuit configuration as shown in the figure, the large current flowing through the two ground lines 400 connected to the respective common electrodes of the L light emitting elements 100 is controlled by one common electrode selection IC 300. The IC needs to have a relatively large structure capable of withstanding a very large current, and there is a problem that the structure becomes large. Further, if the number of the light emitting elements 100 is changed, the current flowing through the ground line 400 also changes. Therefore, it is necessary to change the structure of the common electrode selecting IC 300 according to the number of the light emitting elements 100. Problems such as lack of versatility of the IC occur.
Japanese Utility Model Publication No. 6-48887 JP-A-6-163980

  An object of the present invention is to provide an optical device suitable for a high-resolution optical printer head. Another object is to provide an optical device that enables low-density arrangement of individual electrodes and improves workability of wiring the individual electrodes. Another object is to prevent an increase in the size of the structure. Another object is to increase the versatility of the driving IC. Another object is to provide an optical device that can be manufactured using a manufacturing process of a conventional static type optical printer head.

  The optical device of the present invention divides the plurality of light emitting units into a plurality of groups, and provides a plurality of common electrodes connected to the light emitting units of each group and a plurality of individual electrodes connected to the light emitting units belonging to different groups. A driving circuit for driving the light emitting element, the driving circuit comprising: a first driving unit for selecting the plurality of individual electrodes; and a second driving unit for selecting the plurality of common electrodes. An optical device provided with a driving IC integrally provided with a portion corresponding to the light emitting element, wherein between the light emitting element and the driving IC, between the individual electrode and the first driving section, and Wiring for connecting between the common electrode and the second driver is provided, and the wiring has a direct connection structure using a wire bond line.

  The driving IC is characterized in that a terminal for selecting the plurality of individual electrodes and a terminal for selecting the plurality of common electrodes are arranged on one side.

According to the present invention, by using the light emitting element corresponding to the time-division driving in the element, the low density arrangement of the individual electrodes of the light emitting element, that is, the long pitch arrangement of the individual electrodes is enabled, and the workability of wiring to the individual electrodes is improved. Can be enhanced. As a result, even if the light emitting units are arranged at a high density, wiring becomes easy, and an optical device suitable for a high-resolution optical printer head can be provided.

  Further, a wiring is provided between the light emitting element and the driving IC to connect the individual electrode and the first driving unit and between the common electrode and the second driving unit. Since a direct connection structure using a wire bond line is used, it is possible to provide an optical device that can be manufactured by using a manufacturing process of a conventional static optical printer head.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, the structure of the optical print head 1 will be described with reference to FIGS.

  The optical print head 1 has a plurality of, for example, L = 38 light emitting elements 3 arranged in a line on an insulating substrate 2, and a drive for driving the light emitting elements 3 adjacent to one side of the light emitting elements 3. The ICs 4 are arranged in a line in one-to-one correspondence with the light emitting elements 3. In this example, the driving ICs 4 are arranged on one side of the light emitting element 3. However, when the driving ICs 4 are arranged on both sides of the light emitting element 3, the light emitting element 3 and the driving IC 4 have a one-to-two correspondence. Just arrange them. A wiring 5 is provided between the light emitting element 3 and the driving IC 4 to connect them. As the wiring 5, a direct connection structure using a wire bond line such as a gold wire or an indirect connection structure using a wire bond line with a relay pattern interposed therebetween can be used. A structure in which connection is made using an agent can also be used.

  A plurality of signal and power supply wiring patterns 6 are formed on the substrate 2 so as to extend in the arrangement direction of the light emitting elements 3. The wiring 7 similar to the wiring 5 is provided between the driving IC 4 and the wiring pattern 6. The driving IC 4, the wirings 5, 7, the wiring pattern 6, and the like constitute a driving circuit for driving the light emitting element 3, and the circuit configuration of the optical print head 1 including these components is, for example, a circuit as shown in FIG. It is represented by a block diagram.

Next, the structure of the light emitting element 3 will be described with reference to FIGS. FIG. 3A is a plan view of a main part of the light emitting element 3, and FIG. 3B is a cross-sectional view taken along an arrow in FIG. In the following description and drawings, reference numerals a, b, c, and d attached to the figure numbers distinguish the groups. In the figure, reference numeral 30 denotes a p-type or insulating substrate having a total length of about 10 mm and a width of about 2 mm, and is preferably made of a semiconductor material or the like selected from Si, GaAs on Si, GaAs and the like. On the substrate 30, a plurality of contact layers 31 (31a, 31b) such as n-type GaAs which are long in the width direction of the substrate 30 are formed in the length direction of the substrate 30. On each contact layer 31 located on one side of the substrate 30, an n-type semiconductor layer 32 (32a, 32b) such as n-type GaAlAs and a p-type semiconductor layer 33 (33a, 33b) such as p-type GaAlAs are provided. Are stacked, and a contact layer 34 (34a, 34b) of p-type GaAs or the like is further stacked thereon. By the PN junction of the n-type semiconductor layer 32 and the p-type semiconductor layer 33, a plurality of, for example, 192 light-emitting portions 35 (35a, 35b) are formed. The light emitting sections 35 are arranged in one row in the length direction of the substrate 30. However, the light emitting sections 35 may be arranged in a staggered manner as described later, or may be arranged in two or more rows as described in the above-mentioned publication. You can also. Then, an insulating layer 36 such as Si ₃ N ₄ or SiO ₂ is formed on the surface of the contact layer 34 except for a part of the contact layer 31 located near the other side of the substrate 30. A plurality of common electrodes 37 (37a, 37b) and a plurality of individual electrodes 38 are formed.

  The number of the common electrodes 37 is set according to the number of groups in the case where the plurality of light emitting units 35 are divided into a plurality of groups (M groups). Here, 192 light emitting units 35 are alternately set as the first group. Since the case where the light-emitting unit is divided into two groups, such as the light-emitting unit 35a belonging to the second group and the light-emitting unit 35b belonging to the second group, is illustrated, two common electrodes 37a and 37b are provided corresponding to M = 2. Then, the contact layer 31a connected to the light emitting unit 35a belonging to the first group is connected to the first common electrode 37a so that each group can be selected by the common electrodes 37a and 37b, and the light emission belonging to the second group is performed. The contact layer 31b connected to the portion 35b is connected to the second common electrode 37b. The connection between the common electrode 37 and the contact layer 31 is performed via a selection hole 39 provided in the insulating layer 36.

  The individual electrode 38 is provided so as to connect the light emitting units 35a and 35b belonging to different groups, and in this example, to connect the contact layers 34 of two adjacent light emitting units 35. The wide portion of the individual electrode 38 functions as a pad region for wire bonding. N individual electrodes 38 are provided in a line along the length direction of the substrate 30, and in this example, 96 individual electrodes 38 are provided. The total number of the light-emitting portions 35 on the light-emitting element 3 is represented by M × N, and is 192 in this example. Here, the arrangement pitch of the individual electrodes 38 can be set to M times the arrangement pitch of the light-emitting portions 35, in this example, twice, so that the wiring workability when performing wire bond connection to the individual electrodes 38 is improved. Can be enhanced. Since the number of the light emitting elements 3 is L (38), the number of the light emitting sections 35 in the entire head 1 is L × M × N = 38 × 2 × 96 = 7296.

  In the light emitting element 3 configured as described above, by selecting one of the common electrodes 37a and 37b, the light emitting unit 35 belonging to any one of the plurality of groups can be selected and selected. The lighting state of the plurality of light emitting units 35 belonging to the group can be selected according to the energization state of the individual electrode 38. For example, when one common electrode 37a is selected, the current flows through the individual electrode 38, the contact layer 34a, the p-type semiconductor layer 33a, the n-type semiconductor layer 32a, the contact layer 31a, and the one common electrode 37a. As a result, the light emitting section 35a emits light. When the other common electrode 37b is selected, a current flows through the individual electrode 38, the contact layer 34b, the p-type semiconductor layer 33b, the n-type semiconductor layer 32b, the contact layer 31b, and the other common electrode 37b, and light is emitted by the current at that time. The portion 35b emits light.

  Next, the driving IC 4 will be described with reference to FIG. FIG. 4 shows an internal circuit configuration of one driving IC 4. The fundamental difference from the conventional static IC is that in addition to the first drive unit 41 for selecting individual electrodes, a second drive unit 42 for selecting the common electrode 37 of the light emitting element 3 is incorporated. In addition, it is possible to perform a time-division driving in the element. The details will be described below. The driving IC 4 includes a plurality of individual electrode selecting terminals DO1 to DO96 and a corresponding first driving unit 41 for selecting individual electrodes, similarly to the conventional static IC. The first drive section 41 is based on a shift register (96 bits) 43 for taking in a serial signal from the input terminal SI of the lighting signal in accordance with the clock signal CLOCK1, and an exclusive OR output of the selection signal SEL and the load signal LOAD1. Latch circuit 44 for taking in the parallel output signal of shift register 43, AND gate circuit 45 for selectively outputting each output of latch circuit 44 by strobe signal STB, and power supply from constant current circuit 46, A current driving circuit 47 for supplying desired electric power to each of the plurality of individual electrode selecting terminals DO1 to DO96 based on a signal from the AND gate circuit 45;

  In addition, a second drive unit 42 for selecting a common electrode and common electrode terminals CDO1 and CDO2 for selecting a common electrode are provided for performing in-element time-division driving. The second drive unit 42 includes a selection circuit 48 set to operate in synchronization with an operation timing of the first drive unit 41, for example, a timing of latching a signal to the latch circuit 44, and an output of the selection circuit 48. And the common electrode terminals CDO1 and CDO2 are alternately connected to one power supply potential, for example, the ground potential (Vss) in synchronization with the timing at which the signal is latched in the latch circuit 44. Make up.

  Each of the driving ICs 4 is composed of the same IC having the above-described circuit configuration. As shown in FIG. 1, on one side of the upper surface, the plurality of individual electrode selecting terminals DO1 to DO96 are provided. The common electrode selection terminals CDO1 and CDO2 are arranged, and various signal terminals and power supply terminals are arranged near the other side of the upper surface. The driving ICs 4 are arranged in a line in the same direction as the arrangement direction of the light emitting elements 3 at a predetermined interval from the corresponding light emitting elements 3 as shown in FIG.

  As shown in this figure, the wiring between the individual electrode 38 of the light emitting element 3 and the individual electrode terminal DO of the driving IC 4 is arranged in the direction orthogonal to the arrangement direction of the light emitting element 3 as in the case of the conventional static method. However, the driving IC 4 is provided with the common electrode selection terminals CDO1 and CDO2, and the common electrode wiring 5CDO connected thereto is also different from the individual electrode wiring 5DO. That is, they are arranged in the same direction. Here, considering a case where all the light emitting units 35 belonging to one group are turned on and a current of 4 mA flows through one light emitting unit, the current flowing through the common electrode 37 connected to the group is 4 mA × 96 = about 384 mA, and a general wire bond wire having an allowable current of about 1 A can be used as a wiring to the common electrode 37. In this example, two wire bond lines are used as the wirings 5CDO for the common electrode selection terminals CDO1 and CDO2, respectively, to provide a margin.

  By doing so, wiring using a wiring device compatible with the conventional static method can be performed, and efficient operation of the assembling device can be performed.

  When the light emitting element 3 is configured so that any one of the common electrodes 37 is located on the opposite side of the individual electrode 38 with respect to the light emitting section 35, the wiring 5 from the driving IC 4 to the common electrode 37 is connected to the light emitting section. If the light-emitting unit 35 is disposed so as to pass over the light-emitting unit 35, there is a possibility that the light-emitting unit 35 may be blocked. In such a case, in order to prevent this, an auxiliary wiring pattern passing under the light emitting element 3 is formed on the surface of the substrate 2, and a common electrode wiring from the driving IC 4 is connected to one end of the auxiliary wiring pattern. Then, the wiring from the driving IC 4 to the common electrode 37 is formed by connecting the wiring for the common electrode to the light emitting element 3 to the other end of the auxiliary wiring pattern and performing wiring such as wire bonding via the auxiliary wiring pattern. 5 may be configured so as not to block the light of the light emitting unit 35.

  FIG. 2 shows a circuit block diagram of the optical print head 1. Each of the driving ICs 4 is connected in parallel to a wiring pattern 6 having various signal lines and power supply lines, and supplies a lighting serial signal to the next driving IC 4. Is connected to the signal input terminal SI of the next adjacent driving IC 4. Each of the driving ICs 4 sequentially receives the serial input signal transmitted in synchronization with the clock signal, and is controlled by another timing signal to connect the first common electrode 37 a to the corresponding light emitting element 3. Selectively perform lighting control of the plurality of light emitting units 35a belonging to the first group, and subsequently select the second common electrode 37b to perform lighting control of the plurality of light emitting units 35b belonging to the second group. Thus, time-division driving in the light emitting element 3 is performed. As a result of such time-division driving in the light emitting elements 3 being performed simultaneously by all the light emitting elements 3, the light emitting sections 35a belonging to the first group among all the light emitting sections 35 of the optical print head 1 are simultaneously turned on. Then, the light emitting units 35b belonging to the second group are simultaneously turned on.

  As described above, each light emitting element 3 is configured to support the time division driving in the element, each driving IC 4 includes the second driving unit 42 for performing the time division driving, and the light emission corresponding to each driving IC 4 is performed. Since the element 3 is configured to perform time-division driving, the maximum load applied to the driving unit 42 is determined based on the number of the light emitting units 35 belonging to one group of the corresponding light emitting elements 3. As a result, as compared with the case where a dedicated IC for time division driving (for selecting a common electrode) is used to perform time division driving for all the light emitting elements as in the conventional dynamic driving method, the time division driving method is used. The load applied to the circuit can be significantly reduced. The second driving section 42 of the driving IC 4 can be formed by a small circuit capable of controlling a small current, and the driving IC 4 is formed in the same shape as the conventional static type IC. Therefore, the overall circuit configuration can be reduced in size.

  Furthermore, since the light emitting elements 3 corresponding to the driving ICs 4 are driven in a time-division manner, the number of the light emitting elements 3 can be increased or decreased according to the change in the length of the optical print head 1. The number of driving ICs 4 can be easily increased / decreased in accordance with the increase / decrease of the number 3, thereby contributing to simplification of circuit design. In other words, by using a method similar to the conventional dynamic driving method, it is possible to avoid the problem of an increase in the size of a dedicated IC expected when a dedicated IC for selecting a common terminal is used and a change in the design of the dedicated IC corresponding to an increase or decrease in the number of elements. be able to.

  In the above-described embodiment, the light emitting elements 3 in which the plurality of light emitting units 35 are arranged in one row are driven in a time-division manner. In order to prevent this, a light emitting portion 35a belonging to the first group and a light emitting portion 35b belonging to the second group are arranged in the arrangement direction (print line direction) of the light emitting portions 35 as shown in FIG. May be arranged at a predetermined distance d with respect to a direction orthogonal to. The distance d is determined in consideration of the structure of the head, the number of rotations of the photosensitive drum, and the like so that the step is eliminated and one run becomes a straight line when one line is printed by turning on all the light emitting units. It is determined in advance by calculation.

  In the above embodiment, the driving ICs 4 are arranged on one side of the light emitting element 3. However, the driving ICs 4 may be arranged on both sides of the light emitting element 3. In this case, a part of the element having the same basic structure as that of the light emitting element 3 shown in FIG. 1 is changed in accordance with the arrangement of both sides of the driving IC 4, and the light emitting element 3 as shown in FIG. Can be. That is, the light emitting unit 35 is divided into four groups (in the order of the first group 35a, the second group 35b, the third group 35c, the fourth group 35d, the first group 35a,... Two common electrodes 37a and 37b for selecting the light emitting units 35a and 35b belonging to the first and second groups are arranged on one side of the light emitting element 3, and the light emitting units belonging to the first and second groups are arranged. An individual electrode 38A connected to 35a and 35b is arranged on the same side as the common electrodes 37a and 37b, and two common electrodes 37c and 37d for selecting the light emitting units 35c and 35d belonging to the third and fourth groups are provided. In addition to being arranged on the other side of the light emitting element 3, the individual electrodes 38B connected to the light emitting units 35c and 35d belonging to the third and fourth groups may be arranged on the same side as the common electrode. With this configuration, when the respective pitches of the individual electrodes 38A and 38B are set to be the same as in the case shown in FIG. 1, the arrangement density of the light emitting portions 35 of the light emitting element 3 is two times smaller than that in the case shown in FIG. The resolution can be set twice as high, and the resolution of the optical printer head can be increased.

  The present invention provides an optical print in which a combination structure of one light emitting element and one or more ICs for driving the same is used as one unit, and a plurality of such structural units are arranged in the same direction as the arrangement direction of the light emitting units. Suitable for heads. The present invention can be applied to other applications such as an optical print head having the one structural unit as a basic structure and an optical device similar thereto.

  The optical device of the present invention can be applied to an optical print head.

FIG. 3A is a plan view of a main part of an optical print head including the optical device of the present invention, and FIG. FIG. 3 is a circuit block diagram of the optical print head. FIG. 2A is a plan view of a main part of a light emitting element constituting the optical device of the present invention, and FIG. FIG. 3 is a circuit block diagram of a driving IC constituting the optical device of the present invention. FIG. 9 is a plan view of a main part showing another configuration example of the light emitting element that constitutes the optical device of the present invention. FIG. 9 is a plan view of a main part showing another configuration example of the light emitting element that constitutes the optical device of the present invention. FIG. 9 is a circuit block diagram showing a conventional example.

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 1 Optical print head 3 Light emitting element 30 Substrate 31 Contact layer 32 N-type semiconductor layer 33 P-type semiconductor layer 34 Contact layer 35 Light emitting part 37 Common electrode 38 Individual electrode 4 Driving IC
41 First drive unit 42 Second drive unit 43 Shift register 44 Latch circuit 47 Current drive circuit 48 Select circuit 49 Common drive circuit 5 Wiring 6 Wiring pattern 7 Wiring DO1 Individual electrode selecting terminal DO96 Individual electrode selecting terminal CDO1 For common electrode Terminal CDO2 common power

Claims (2)

  While dividing the plurality of light emitting units into a plurality of groups, a plurality of common electrodes connected to the light emitting units of each group, and a plurality of individual electrodes connected to the light emitting units belonging to different groups, a light emitting element configured by providing, A driving circuit for driving the light-emitting element, wherein the driving circuit integrally includes a first driving unit for selecting the plurality of individual electrodes and a second driving unit for selecting the plurality of common electrodes. An optical device provided for the light emitting element corresponding to the light emitting element, between the light emitting element and the driving IC, between the individual electrode and the first drive unit, and between the common electrode and the second An optical device, wherein wiring for connecting between driving units is provided, and the wiring has a direct connection structure using a wire bond line.   2. The optical device according to claim 1, wherein the driving IC has a terminal for selecting the plurality of individual electrodes and a terminal for selecting the plurality of common electrodes arranged on one side. 3. apparatus.

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