JP2010153151A - Led planar lighting system - Google Patents

Led planar lighting system Download PDF

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JP2010153151A
JP2010153151A JP2008328925A JP2008328925A JP2010153151A JP 2010153151 A JP2010153151 A JP 2010153151A JP 2008328925 A JP2008328925 A JP 2008328925A JP 2008328925 A JP2008328925 A JP 2008328925A JP 2010153151 A JP2010153151 A JP 2010153151A
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JP5011272B2 (en
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Yukio Nomura
幸男 野村
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Kyoto Denkiki Co Ltd
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Abstract

<P>PROBLEM TO BE SOLVED: To reduce noise resulting from lighting driving, in an LED planar lighting system having a large number of two-dimensionally disposed LEDs. <P>SOLUTION: The two-dimensionally disposed LEDs are divided into a region A and a region B to lightingly drive the LEDs for each region by PWM drive signals having different patterns. The LEDs in the region A are lightingly driven by the PWM drive signal (b) in which the position of a rising edge is fixed and a pulse width wa is controlled, and the LEDs in the region B are lightingly driven by the PWM drive signal (c) in which the position of a falling edge is fixed and a pulse width wb is controlled. Thereby, since timing for ON action or OFF action of transistors in a driving circuit shifts, switching noise disperses, and the peak of a noise level falls. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

本発明は、多数のＬＥＤ（発光ダイオード）を二次元的に配設してなるＬＥＤ面状照明装置に関し、特に、平板状の対象物を略均一に照明し、その透過光や反射光により対象物を検査する用途に好適なＬＥＤ面状照明装置に関する。   The present invention relates to an LED planar illumination device in which a large number of LEDs (light emitting diodes) are two-dimensionally arranged, and in particular, illuminates a flat object substantially uniformly and applies the transmitted light and reflected light to the object. The present invention relates to an LED planar illumination device suitable for use in inspecting an object.

大形の液晶パネルなどの欠陥を製造ラインで検査するために、例えば特許文献１に開示されているような検査装置が利用されている。この検査装置は、平行配置された複数本の冷陰極管などの線状光源と、それら線状光源から発せられる光を面状に変換するための光学シートとを含む検査用バックライト装置（検査用照明装置）を備えている。   In order to inspect defects such as a large liquid crystal panel on a production line, an inspection apparatus as disclosed in Patent Document 1, for example, is used. This inspection apparatus includes an inspection backlight device (inspection) including linear light sources such as a plurality of cold-cathode tubes arranged in parallel and an optical sheet for converting light emitted from the linear light sources into a planar shape. Lighting device).

近年、こうした検査用照明装置にもより一層の照度の均一性、高寿命化、低消費電力化などが要求されている。一方、ＬＥＤの性能向上、特に高輝度化は最近、非常に進展しており、照明用光源として高輝度ＬＥＤが使用されるようになってきている。こうした流れの中で、上記のような検査用照明装置にもＬＥＤが使用されるようになってきている。   In recent years, even such illumination devices for inspection are required to have even more illuminance uniformity, longer life, and lower power consumption. On the other hand, the performance improvement of LEDs, in particular, the increase in brightness has been greatly progressed recently, and high-brightness LEDs have come to be used as illumination light sources. In such a flow, LEDs have come to be used also in the above-described inspection illumination device.

上記のような平面状の照明装置を構成する場合、多数の高輝度ＬＥＤを二次元的に配設し、各ＬＥＤをＰＷＭ（パルス幅変調）駆動することで輝度を調整することが考えられる。ところが、光源部を大型化するためにＬＥＤの数を増やすほど、ＰＷＭ駆動信号を生成する回路でのスイッチングノイズが大きくなり、不要輻射による外部機器への悪影響が問題となる。特に、検査用照明装置の場合、上記のようなノイズが対象物を撮影する撮像機器や画像処理回路などの誤動作の原因となると、適切な検査ができなくなり、不良品の見逃し或いは正常品の誤判定といった大きな問題を引き起こすおそれがある。   In the case of configuring the planar illumination device as described above, it is conceivable to adjust the luminance by arranging a large number of high-brightness LEDs two-dimensionally and driving each LED by PWM (pulse width modulation). However, as the number of LEDs is increased in order to increase the size of the light source unit, switching noise in a circuit that generates a PWM drive signal increases, and adverse effects on external devices due to unnecessary radiation become a problem. In particular, in the case of an inspection lighting device, if the noise described above causes a malfunction of an imaging device or an image processing circuit for photographing an object, an appropriate inspection cannot be performed, and a defective product is overlooked or a normal product is mistaken. There is a risk of causing serious problems such as judgment.

特開２００７−２５１３２号公報JP 2007-25132 A

本発明は上記課題に鑑みて成されたものであり、多数のＬＥＤを利用したＬＥＤ面状照明装置におけるノイズを低減することを主たる目的としている。   The present invention has been made in view of the above problems, and has as its main purpose to reduce noise in an LED planar illumination device using a large number of LEDs.

上記課題を解決するために成された本発明は、複数のＬＥＤが二次元的に配設された面状光源部と、前記複数のＬＥＤをＰＷＭ（パルス幅変調）駆動するＬＥＤ駆動部と、を具備するＬＥＤ面状照明装置において、
前記ＬＥＤ駆動部は、立ち上がりエッジ位置及び立ち下がりエッジ位置がともに相違する少なくとも２以上の異なるパターンのＰＷＭ駆動信号を生成し、前記光源部において複数に分割された各領域に含まれるＬＥＤ毎に、前記異なるパターンのＰＷＭ駆動信号により点灯駆動することを特徴としている。 The present invention made to solve the above problems includes a planar light source unit in which a plurality of LEDs are two-dimensionally arranged, an LED driving unit that drives the plurality of LEDs by PWM (pulse width modulation), In the LED planar illumination device comprising:
The LED drive unit generates at least two different patterns of PWM drive signals having different rising edge positions and falling edge positions, and for each LED included in each of the regions divided into a plurality in the light source unit, It is characterized in that lighting driving is performed by the PWM drive signals of different patterns.

本発明に係るＬＥＤ面状照明装置では、ＬＥＤ駆動部が複数の異なるパターンのＰＷＭ駆動信号によりＬＥＤを点灯駆動することにより、光源部に含まれるＬＥＤへの駆動電流の供給期間（つまり点灯期間）を時間的に分散させることができる。これにより、ＬＥＤ駆動部に含まれるトランジスタなどの回路素子のオン・オフ動作に伴って発生するスイッチングノイズが分散化され、ノイズレベルのピーク値が減少する。   In the LED planar illumination device according to the present invention, the LED driving unit drives the LED to light by a plurality of different patterns of PWM drive signals, thereby supplying a driving current to the LEDs included in the light source unit (that is, a lighting period). Can be dispersed in time. As a result, switching noise generated in accordance with the on / off operation of circuit elements such as transistors included in the LED driving unit is dispersed, and the peak value of the noise level is reduced.

また、ＬＥＤへの駆動電流の供給期間が分散化されることで、電流を供給する電源の稼働率も或る程度平均化される。それにより、リップル電流が減少するため、電源を構成する回路素子へのストレスが減り、故障が起こりにくくなって信頼性の向上にもつながる。   In addition, since the supply period of the drive current to the LEDs is dispersed, the operating rate of the power supply that supplies the current is also averaged to some extent. As a result, the ripple current is reduced, so that the stress on the circuit elements constituting the power source is reduced, failure is less likely to occur, and reliability is improved.

本発明に係るＬＥＤ面状照明装置の好ましい一態様として、Ｎ（Ｎは２以上）種の異なるパターンは、各ＰＷＭ駆動信号のデューティ比が（１００／Ｎ）％未満であるときにパルス幅が重ならないパターンとするとよい。   As a preferable aspect of the LED planar illumination device according to the present invention, N (N is 2 or more) different patterns have a pulse width when the duty ratio of each PWM drive signal is less than (100 / N)%. A pattern that does not overlap is good.

具体的には例えば、前記ＰＷＭ駆動信号として互いに異なるパターンの第１及び第２のＰＷＭ駆動信号を含み、第１のＰＷＭ駆動信号の立ち上がりエッジ位置と第２のＰＷＭ駆動信号の立ち下がりエッジ位置とが一致し、第１のＰＷＭ駆動信号はパルス幅に応じて立ち下がりエッジ位置が変移し、第２のＰＷＭ駆動信号はパルス幅に応じて立ち上がりエッジ位置が変移する構成とすることができる。   Specifically, for example, the PWM drive signal includes first and second PWM drive signals having different patterns, and the rising edge position of the first PWM drive signal and the falling edge position of the second PWM drive signal are And the falling edge position of the first PWM drive signal changes according to the pulse width, and the rising edge position of the second PWM drive signal changes according to the pulse width.

この構成によれば、ＬＥＤへの駆動電流の供給期間を適切に分散することができるので、ノイズ低減や電源の稼働率の平均化にも有利である。また、第１のＰＷＭ駆動信号が立ち上がる際に第２のＰＷＭ駆動信号は立ち下がるため、それらＰＷＭ駆動信号を生成するためのトランジスタなどの回路素子のオン・オフ動作に伴うノイズを低減する効果が期待できる。   According to this configuration, the supply period of the drive current to the LEDs can be appropriately distributed, which is advantageous for noise reduction and averaging of the power supply operation rate. In addition, since the second PWM drive signal falls when the first PWM drive signal rises, there is an effect of reducing noise associated with on / off operations of circuit elements such as transistors for generating the PWM drive signal. I can expect.

なお、光源部における上記複数の領域は適宜に設定することができるが、例えばＬＥＤの１ライン毎に異なる領域となるようにするとよい。   In addition, although the said some area | region in a light source part can be set suitably, it is good to make it become a different area | region for every line of LED, for example.

本発明に係るＬＥＤ面状照明装置によれば、動作に伴うノイズレベルが下がるので、不要輻射による外部機器への悪影響などを防止することができる。それにより、本面状照明装置を検査装置に組み込む場合に、検査装置本体の回路の誤動作などを防止し、良好な検査を遂行することができる。また、本発明に係るＬＥＤ面状照明装置によれば、電源を構成する回路素子へのストレスが低減されるため、故障が起こりにくくなり、長寿命化による信頼性の向上が図れる。   According to the LED planar illumination device according to the present invention, the noise level associated with the operation is lowered, so that it is possible to prevent adverse effects on external devices due to unnecessary radiation. As a result, when the planar illumination device is incorporated into an inspection device, it is possible to prevent malfunction of the circuit of the inspection device body and perform a good inspection. In addition, according to the LED planar illumination device according to the present invention, since stress on the circuit elements constituting the power source is reduced, failure is unlikely to occur, and reliability can be improved by extending the life.

本発明に係るＬＥＤ面状照明装置の一実施例を図面を参照して説明する。図４は本実施例のＬＥＤ面状照明装置の一使用形態である検査装置の概略図である。   An embodiment of an LED planar illumination device according to the present invention will be described with reference to the drawings. FIG. 4 is a schematic view of an inspection apparatus which is one usage pattern of the LED planar illumination device of this embodiment.

図４において、本実施例の面状照明装置は多数のＬＥＤが平面的に配列された（図４はこれを横から見た状態である）面状光源部１と各ＬＥＤを点灯駆動するＬＥＤ点灯装置２とから成る。面状光源部１は単位時間当たりの光エネルギーが略一定であり、また平面的な照射面（図４では上面）の輝度が略均一となっている。この面状光源部１と撮像装置４との間に液晶パネル等の検査対象物３が配設される。撮像装置４は面状光源部１によって背面側から照らされる検査対象物３を撮影し、画像処理装置５は撮影された画像を処理することで検査対象物３の微細な欠陥の有無を識別する。   In FIG. 4, the planar illumination device of this embodiment has a planar light source unit 1 in which a number of LEDs are arranged in a plane (FIG. 4 is a side view thereof) and LEDs that drive and drive each LED. And the lighting device 2. In the planar light source unit 1, the light energy per unit time is substantially constant, and the luminance of the planar irradiation surface (upper surface in FIG. 4) is substantially uniform. An inspection object 3 such as a liquid crystal panel is disposed between the planar light source unit 1 and the imaging device 4. The imaging device 4 images the inspection object 3 illuminated from the back side by the planar light source unit 1, and the image processing device 5 processes the captured image to identify the presence or absence of minute defects in the inspection object 3. .

図３は面状光源部１の平面図である。１枚の基板１２には同一種類の高輝度白色ＬＥＤ１１が格子状に配列され、この基板１２が平面的に２０枚並べられることで面状光源部１は構成されている。この例では、ＬＥＤ１１の１ライン毎に互いに異なる領域Ａ及び領域Ｂが設定されており、領域Ａに含まれるＬＥＤ１１と領域Ｂに含まれるＬＥＤ１１とは互いに異なるパターンのＰＷＭ駆動信号により点灯駆動されるようになっている。   FIG. 3 is a plan view of the planar light source unit 1. The same type of high-intensity white LEDs 11 are arranged in a grid pattern on one substrate 12, and the planar light source unit 1 is configured by arranging 20 substrates 12 in a plane. In this example, different areas A and B are set for each line of the LED 11, and the LEDs 11 included in the area A and the LEDs 11 included in the area B are driven to be lit by PWM drive signals having different patterns. It is like that.

図１は本実施例のＬＥＤ面状照明装置におけるＬＥＤ点灯装置２の概略構成図、図２はＬＥＤ点灯装置２の動作を説明するためのタイムチャートである。   FIG. 1 is a schematic configuration diagram of the LED lighting device 2 in the LED planar lighting device of this embodiment, and FIG. 2 is a time chart for explaining the operation of the LED lighting device 2.

このＬＥＤ点灯装置２は、ＣＰＵ、ＲＯＭ、ＲＡＭなどを含むマイクロコンピュータによりその機能が達成されるＰＷＭ駆動部２１と、ＰＷＭ駆動部２１から与えられる駆動信号に応じて駆動電流をＬＥＤ１１に供給する駆動回路２６Ａ、２６Ｂと、を含む。ＰＷＭ駆動部２１からは、互いに異なるパターンのＰＷＭ駆動信号が出力され、駆動回路２６Ａは上述した領域Ａに含まれるＬＥＤ１１に駆動電流を供給し、駆動回路２６Ｂは上述した領域Ｂに含まれるＬＥＤ１１に駆動電流を供給する。ＰＷＭ駆動部２１はマイクロコンピュータにより達成される機能ブロックとして、基準パルス生成部２２、駆動パルスＡ生成部２３、駆動パルスＢ生成部２４、パルス幅制御部２５、を備える。   The LED lighting device 2 has a PWM drive unit 21 whose function is achieved by a microcomputer including a CPU, a ROM, a RAM, and the like, and a drive that supplies a drive current to the LED 11 in accordance with a drive signal supplied from the PWM drive unit 21. Circuits 26A and 26B. The PWM drive unit 21 outputs PWM drive signals having different patterns, the drive circuit 26A supplies drive current to the LEDs 11 included in the region A described above, and the drive circuit 26B applies to the LEDs 11 included in the region B described above. Supply drive current. The PWM drive unit 21 includes a reference pulse generation unit 22, a drive pulse A generation unit 23, a drive pulse B generation unit 24, and a pulse width control unit 25 as functional blocks achieved by a microcomputer.

図２により、ＬＥＤ点灯装置２の動作を説明する。
基準パルス生成部２２は、例えば水晶発振器などにより発生される所定周波数の基準クロックを計数する１／ｎ分周カウンタを含む。このカウンタの出力値は、図２（ａ）に示すように０からｎまで順にインクリメントされ、ｎに達すると０にリセットされる。したがって、基準パルス生成部２２の出力は図２（ａ）に示すように三角波パルス信号である。この三角波パルス信号のサイクルは例えば８０[kHz]とすることができる。 The operation of the LED lighting device 2 will be described with reference to FIG.
The reference pulse generation unit 22 includes a 1 / n frequency division counter that counts a reference clock having a predetermined frequency generated by, for example, a crystal oscillator. The output value of this counter is incremented sequentially from 0 to n as shown in FIG. 2A, and reset to 0 when n is reached. Therefore, the output of the reference pulse generator 22 is a triangular wave pulse signal as shown in FIG. The cycle of this triangular wave pulse signal can be set to 80 [kHz], for example.

上記三角波パルス信号が駆動パルスＡ生成部２３と駆動パルスＢ生成部２４とに入力される。駆動パルスＡ生成部２３は、三角波パルス信号がカウンタ値＝０で立ち上がり、カウンタ値がｐ（ｐ≦ｎ）に達すると立ち下がる矩形波パルス信号を第１のＰＷＭ駆動信号として生成する（図２（ｂ）参照）。一方、駆動パルスＢ生成部２４は、三角波パルス信号のカウンタ値がｑ（＝ｎ−ｐ）に達すると立ち上がり、カウンタ値が０になるときに立ち下がる矩形波パルス信号を第２のＰＷＭ駆動信号として生成する（図２（ｃ）参照）。つまり、第１のＰＷＭ駆動信号の立ち上がりエッジと第２のＰＷＭ駆動信号の立ち下がりエッジとは一致している。   The triangular wave pulse signal is input to the drive pulse A generator 23 and the drive pulse B generator 24. The drive pulse A generation unit 23 generates, as the first PWM drive signal, a rectangular wave pulse signal that rises when the triangular wave pulse signal has a counter value = 0 and falls when the counter value reaches p (p ≦ n) (FIG. 2). (See (b)). On the other hand, the drive pulse B generation unit 24 converts the square wave pulse signal that rises when the counter value of the triangular wave pulse signal reaches q (= n−p) and falls when the counter value becomes 0 to the second PWM drive signal. (See FIG. 2C). That is, the rising edge of the first PWM drive signal is coincident with the falling edge of the second PWM drive signal.

パルス幅制御部２５は外部から指示される光量設定値に応じて、ｐ値を駆動パルスＡ生成部２３へ指示し、ｑ値を駆動パルスＢ生成部２４へ指示する。光量を増加する場合には、ｐ値を増加する一方、ｑ値を減少させる。これにより、駆動パルスＡ生成部２３で生成される第１のＰＷＭ駆動信号のパルス幅ｗａ、及び、駆動パルスＢ生成部２４で生成される第２のＰＷＭ駆動信号のパルス幅ｗｂ（＝ｗａ）は広がる。第１のＰＷＭ駆動信号は立ち上がりエッジの位置が固定され、第２のＰＷＭ駆動信号は立ち下がりエッジの位置が固定されているから、両ＰＷＭ駆動信号のデューティ比が５０％未満であるときにはパルス幅ｗａ、ｗｂは重ならない。   The pulse width control unit 25 instructs the drive pulse A generation unit 23 on the p value and instructs the drive pulse B generation unit 24 on the q value according to the light amount setting value specified from the outside. When increasing the amount of light, the p value is increased while the q value is decreased. As a result, the pulse width wa of the first PWM drive signal generated by the drive pulse A generator 23 and the pulse width wb (= wa) of the second PWM drive signal generated by the drive pulse B generator 24. Spreads. Since the first PWM drive signal has a fixed rising edge position and the second PWM drive signal has a fixed falling edge position, when the duty ratio of both PWM drive signals is less than 50%, the pulse width wa and wb do not overlap.

即ち、両ＰＷＭ駆動信号のデューティ比が５０％未満であるとき、領域Ａに含まれるＬＥＤ１１と領域Ｂに含まれるＬＥＤ１１とは交互に点灯することになる。ＰＷＭ点灯駆動の１サイクルは撮像装置４による１フレームの撮像サイクルに比べて十分に短いので、全てのＬＥＤがパルス幅ｗａの同一のＰＷＭ駆動信号により点灯駆動される場合と同じ輝度となる。   That is, when the duty ratio of both PWM drive signals is less than 50%, the LEDs 11 included in the region A and the LEDs 11 included in the region B are alternately lit. Since one cycle of the PWM lighting drive is sufficiently shorter than the one-frame imaging cycle by the imaging device 4, all the LEDs have the same luminance as when the LEDs are driven to light by the same PWM driving signal having the pulse width wa.

駆動回路２６Ａ、２６ＢにはＰＷＭ駆動信号によりオン・オフされるトランジスタ等が含まれ、そのオン・オフ動作に際してスイッチングノイズが発生する。本実施例のＬＥＤ面状照明装置では、駆動回路２６Ａに供給されるＰＷＭ駆動信号と駆動回路２６Ｂに供給されるＰＷＭ駆動信号とでは立ち上がりエッジ位置及び立ち下がりエッジ位置が相違するので、駆動回路２６Ａに含まれるトランジスタと駆動回路２６Ｂに含まれるトランジスタとが同時にオフ→オン動作又はオン→オフ動作することはなく、そのタイミングは時間的にずれる。そのため、スイッチングノイズは時間的に分散され、ノイズレベルのピーク値は下がる。   The drive circuits 26A and 26B include transistors and the like that are turned on / off by a PWM drive signal, and switching noise is generated during the on / off operation. In the LED planar illumination device of this embodiment, the rising edge position and the falling edge position are different between the PWM drive signal supplied to the drive circuit 26A and the PWM drive signal supplied to the drive circuit 26B. And the transistor included in the drive circuit 26B are not simultaneously turned off → on or turned on → off, and their timings are shifted in time. Therefore, switching noise is temporally dispersed, and the peak value of the noise level is lowered.

また、両ＰＷＭ駆動信号のデューティ比が５０％未満であるとき、駆動回路２６Ａに含まれるトランジスタと駆動回路２６Ｂに含まれるトランジスタとは同時にオン状態とならない。そのため、駆動電流を供給する電源の稼働率が平均化され、電源電流のリップル電流が減少する。それにより、電源の回路素子に対するストレスが軽減される。   When the duty ratio of both PWM drive signals is less than 50%, the transistors included in the drive circuit 26A and the transistors included in the drive circuit 26B are not turned on at the same time. Therefore, the operation rate of the power supply that supplies the drive current is averaged, and the ripple current of the power supply current is reduced. This reduces stress on the circuit elements of the power supply.

なお、上記実施例は本発明の一例に過ぎず、本発明の趣旨の範囲で適宜変形や修正、追加を加えても本願の特許請求の範囲に包含されることは明らかである。   It should be noted that the above embodiment is merely an example of the present invention, and it is obvious that modifications, corrections, and additions as appropriate within the scope of the present invention are included in the claims of the present application.

例えば上記実施例は、全てのＬＥＤを領域Ａ、Ｂの２つに分けているが、３以上に分けてそれぞれ異なるパターンのＰＷＭ駆動信号により点灯駆動してもよい。また、ＰＷＭ駆動信号の生成方法は上記記載のものに限らない。   For example, in the above embodiment, all the LEDs are divided into two areas A and B, but they may be lit and driven by three or more different PWM drive signals. Further, the method for generating the PWM drive signal is not limited to that described above.

本発明の一実施例によるＬＥＤ面状照明装置における点灯駆動装置の概略構成図。The schematic block diagram of the lighting drive device in the LED planar illumination device by one Example of this invention. 図１の点灯駆動装置の動作説明のタイムチャート。The time chart of operation | movement description of the lighting drive device of FIG. 本実施例のＬＥＤ面状照明装置における面状光源部の平面図。The top view of the planar light source part in the LED planar illuminating device of a present Example. 本実施例のＬＥＤ面状照明装置の一使用形態である検査装置の概略図。Schematic of the inspection apparatus which is one usage pattern of the LED planar illumination apparatus of a present Example.

符号の説明Explanation of symbols

１…面状光源部
１１…ＬＥＤ
１２…基板
２…ＬＥＤ点灯装置
２１…ＰＷＭ駆動部
２２…基準パルス生成部
２３…駆動パルスＡ生成部
２４…駆動パルスＢ生成部
２５…パルス幅制御部
２６Ａ、２６Ｂ…駆動回路
３…検査対象物
４…撮像装置
５…画像処理装置 DESCRIPTION OF SYMBOLS 1 ... Planar light source part 11 ... LED
DESCRIPTION OF SYMBOLS 12 ... Board | substrate 2 ... LED lighting device 21 ... PWM drive part 22 ... Reference pulse production | generation part 23 ... Drive pulse A production | generation part 24 ... Drive pulse B production | generation part 25 ... Pulse width control part 26A, 26B ... Drive circuit 3 ... Test object 4 ... Imaging device 5 ... Image processing device

Claims (3)

複数のＬＥＤが二次元的に配設された面状光源部と、前記複数のＬＥＤをＰＷＭ（パルス幅変調）駆動するＬＥＤ駆動部と、を具備するＬＥＤ面状照明装置において、
前記ＬＥＤ駆動部は、立ち上がりエッジ位置及び立ち下がりエッジ位置がともに相違する少なくとも２以上の異なるパターンのＰＷＭ駆動信号を生成し、前記光源部において複数に分割された各領域に含まれるＬＥＤ毎に、前記異なるパターンのＰＷＭ駆動信号により点灯駆動することを特徴とするＬＥＤ面状照明装置。 In an LED planar illumination device comprising: a planar light source unit in which a plurality of LEDs are arranged two-dimensionally; and an LED driving unit that drives the plurality of LEDs by PWM (pulse width modulation).
The LED drive unit generates at least two different patterns of PWM drive signals having different rising edge positions and falling edge positions, and for each LED included in each of the regions divided into a plurality in the light source unit, An LED planar illumination device that is lit and driven by the PWM drive signals having different patterns. 請求項１に記載のＬＥＤ面状照明装置であって、
Ｎ（Ｎは２以上）種の異なるパターンは、各ＰＷＭ駆動信号のデューティ比が（１００／Ｎ）％未満であるときにパルス幅が重ならないパターンであることを特徴とするＬＥＤ面状照明装置。 The LED planar illumination device according to claim 1,
The N (N is 2 or more) types of different patterns are patterns in which the pulse widths do not overlap when the duty ratio of each PWM drive signal is less than (100 / N)%. . 請求項２に記載のＬＥＤ面状照明装置であって、
前記ＰＷＭ駆動信号として互いに異なるパターンの第１及び第２のＰＷＭ駆動信号を含み、第１のＰＷＭ駆動信号の立ち上がりエッジ位置と第２のＰＷＭ駆動信号の立ち下がりエッジ位置とが一致し、第１のＰＷＭ駆動信号はパルス幅に応じて立ち下がりエッジ位置が変移し、第２のＰＷＭ駆動信号はパルス幅に応じて立ち上がりエッジ位置が変移するものであることを特徴とするＬＥＤ面状照明装置。 The LED planar illumination device according to claim 2,
The PWM drive signal includes first and second PWM drive signals having different patterns, and the rising edge position of the first PWM drive signal coincides with the falling edge position of the second PWM drive signal. The LED planar illumination device is characterized in that the falling edge position of the PWM drive signal changes according to the pulse width, and the rising edge position changes according to the pulse width of the second PWM drive signal.
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