JP6501719B2 - Information processing apparatus and manufacturing method - Google Patents

Description

  The present invention relates to an information processing apparatus and a method of manufacturing the same, and more particularly, to an information processing apparatus having an ultrasonic oscillator, an ultrasonic receiver and an amplifier, and a method of manufacturing the same.

  An information processing apparatus such as a scanner which conveys an original and reads an image of the conveyed original has a function of detecting whether or not double feeding has occurred in which a plurality of originals are overlapped and conveyed. In general, an information processing apparatus such as a scanner includes an ultrasonic oscillator that outputs ultrasonic waves, and an ultrasonic wave receiver that outputs a signal according to the received ultrasonic waves, and the ultrasonic wave receiver operates when an original is conveyed. Double feed is detected based on the output signal.

  On the other hand, in recent years, the spread of wireless devices has spread, and radio waves having frequencies in the gigahertz band are made to fly in environments where information processing apparatuses are used. It is required that each information processing apparatus does not malfunction even if noise from such radio waves is induced. In particular, in the radiated radio frequency electromagnetic field immunity test of IEC (International Electrotechnical Commission) 61000-4-3, it is required not to malfunction for noise of 1 GHz or more and 5 GHz or less.

  There is disclosed an acoustic sensor that functions as a magnetic shield by surrounding various components such as a base and a sensor unit with a housing such as aluminum or stainless steel (see Patent Document 1).

JP, 2015-61310, A

  In an information processing apparatus such as a scanner, it is required not to malfunction with respect to noise having a frequency of 1 GHz or more and 5 GHz or less while suppressing an increase in apparatus size.

  An object of the present invention is to provide an information processing apparatus and a manufacturing method capable of preventing malfunctioning against noise having a frequency of 1 GHz or more and 5 GHz or less while suppressing an increase in apparatus size.

  An information processing apparatus according to one aspect of the present invention includes an ultrasonic oscillator that outputs an ultrasonic wave, and an ultrasonic wave receiver that is disposed on a substrate opposite to the ultrasonic wave oscillator and outputs a signal according to the received ultrasonic wave. And an amplifier disposed on the substrate for amplifying the signal output from the ultrasonic receiver, and a rectangular parallelepiped onboard shield disposed on the substrate so as to cover the amplifier and formed of metal. The height of the on-board shield is greater than the height at which the resonance frequency of the circuit including the amplifier covered with the on-board shield varies depending on the height is 5 GHz and smaller than the height of the ultrasonic receiver.

  According to one aspect of the present invention, there is provided a manufacturing method comprising: an ultrasonic oscillator for outputting an ultrasonic wave; an ultrasonic wave receiver for outputting a signal according to the received ultrasonic wave; and an amplifier for amplifying a signal output from the ultrasonic wave receiver. And an ultrasonic receiver is disposed on the substrate so as to face the ultrasonic oscillator, an amplifier is disposed on the substrate, and a rectangular parallelepiped shape formed of metal is provided. The height of the on-board shield is set so that the resonant frequency of the circuit covered by the on-board shield, which varies with the height, is greater than that at 5 GHz and smaller than the height of the ultrasonic receiver. Place the onboard shield on the board to cover the.

  According to the present invention, the information processing apparatus can not malfunction with respect to noise having a frequency of 1 GHz or more and 5 GHz or less while suppressing an increase in apparatus size.

FIG. 1 is a perspective view showing a document conveyance device 100 according to an embodiment. FIG. 6 is a diagram for explaining a conveyance path inside the document conveyance device 100. FIG. 2 is a perspective view showing an ultrasonic amplification circuit 130. FIG. 7 is a cross-sectional view of the ultrasonic amplification circuit 130 taken along line A-A ′. It is a table showing an experimental result. FIG. 2 is a block diagram showing a schematic configuration of a document conveyance device 100. It is a flowchart for demonstrating a manufacturing process.

  Hereinafter, a document conveyance device according to one aspect of the present invention will be described with reference to the drawings. However, it should be noted that the technical scope of the present invention is not limited to those embodiments, but extends to the invention described in the claims and the equivalents thereof.

  FIG. 1 is a perspective view showing an original conveying apparatus 100 according to the embodiment, which is configured as an image scanner.

  The document conveying apparatus 100 is an example of an information processing apparatus, and includes a lower case 101, an upper case 102, a document table 103, a discharge table 105, operation buttons 106, and the like.

  The upper housing 102 is disposed at a position covering the upper surface of the document conveying apparatus 100, and is engaged with the lower housing 101 by a hinge so as to be openable and closable at the time of cleaning of the document conveying apparatus 100 when the document is broken. There is.

  The document table 103 is engaged with the lower housing 101 so as to place a document. The document table 103 is provided with side guides 104 a and 104 b movable in the direction orthogonal to the document conveyance direction. Hereinafter, the side guides 104 a and 104 b may be collectively referred to as a side guide 104.

  The discharge tray 105 is engaged with the lower housing 101 by a hinge so as to be rotatable in the direction indicated by the arrow A1, and holds the discharged document in the open state as shown in FIG. Is possible.

  The operation button 106 is disposed on the surface of the upper housing 102, and when pressed, generates and outputs an operation detection signal.

  FIG. 2 is a view for explaining a conveyance path inside the document conveyance device 100. As shown in FIG.

  The conveyance path in the document conveyance device 100 includes a first document detection sensor 111, feeding rollers 112a and 112b, brake rollers 113a and 113b, a second document detection sensor 114, an ultrasonic oscillator 115a, an ultrasonic wave receiver 115b, and an ultrasonic wave. The amplification circuit 130, the first conveyance rollers 116a and 116b, the first driven rollers 117a and 117b, the third document detection sensor 118, the first imaging device 119a, the second imaging device 119b, the second conveyance rollers 120a and 120b, and the second follower It has rollers 121a and 121b and the like.

  Hereinafter, the feed rollers 112 a and 112 b may be collectively referred to as a feed roller 112. Also, the brake rollers 113a and 113b may be collectively referred to as a brake roller 113. In addition, the first conveying rollers 116a and 116b may be collectively referred to as a first conveying roller 116. Also, the first driven rollers 117a and 117b may be collectively referred to as a first driven roller 117. In addition, the second conveyance rollers 120a and 120b may be collectively referred to as a second conveyance roller 120. Also, the second driven rollers 121a and 121b may be collectively referred to as a second driven roller 121.

  The upper surface of the lower housing 101 forms a lower guide 107a of the document conveyance path, and the lower surface of the upper housing 102 forms an upper guide 107b of the document conveyance path. In FIG. 2, an arrow A2 indicates the transport direction of the document. Hereinafter, the upstream refers to the upstream of the document transport direction A2, and the downstream refers to the downstream of the document transport direction A2.

  The first document detection sensor 111 has a contact detection sensor disposed upstream of the feed roller 112 and the brake roller 113, and detects whether a document is placed on the document table 103. The first document detection sensor 111 generates and outputs a first document detection signal in which the signal value changes depending on whether the document is placed on the document table 103 or not.

  The second document detection sensor 114 has a contact detection sensor disposed on the downstream side of the feeding roller 112 and the brake roller 113 and on the upstream side of the first conveyance roller 116 and the first driven roller 117. To detect the presence or absence of The second document detection sensor 114 generates and outputs a second document detection signal in which the signal value changes depending on whether the document exists at the position or not.

  The ultrasonic oscillator 115a and the ultrasonic receiver 115b are disposed in the vicinity of the document conveyance path so as to face each other across the conveyance path. The ultrasonic oscillator 115a outputs an ultrasonic wave. Meanwhile, the ultrasonic wave receiver 115b receives an ultrasonic wave oscillated by the ultrasonic wave generator 115a and having passed through the document, and generates an ultrasonic wave signal which is an electric signal according to the received ultrasonic wave, and the ultrasonic wave amplification circuit 130 is generated. Output to This ultrasonic signal is used to detect double feed of the document. Hereinafter, the ultrasonic generator 115a and the ultrasonic receiver 115b may be collectively referred to as an ultrasonic sensor 115.

  The ultrasound amplification circuit 130 receives the ultrasound signal output from the ultrasound receiver 115 b, amplifies the received ultrasound signal, and outputs the amplified ultrasound signal. The ultrasound receiver 115 b and the ultrasound amplification circuit 130 are disposed on the substrate 131.

  The third document detection sensor 118 has a contact detection sensor disposed downstream of the first conveyance roller 116 and the first driven roller 117 and upstream of the first imaging device 119a and the second imaging device 119b. It detects whether the document exists at the position. The third document detection sensor 118 generates and outputs a third document detection signal in which the signal value changes depending on whether the document exists at the position or not.

  The first imaging device 119 a includes an imaging sensor of a reduction optical system type including an imaging element by a CCD (Charge Coupled Device) linearly arranged in the main scanning direction. The image sensor reads the back side of the document to generate and output an analog image signal. Similarly, the second imaging device 119 b includes an imaging sensor of a reduction optical system type provided with an imaging element by a CCD linearly arranged in the main scanning direction. The image sensor reads the surface of the document to generate and output an analog image signal. Alternatively, only one of the first imaging device 119a and the second imaging device 119b may be disposed, and only one side of the document may be read. Also, instead of the CCD, a CIS (Contact Image Sensor) of an equal magnification optical system type provided with an imaging device by a Complementary Metal Oxide Semiconductor (CMOS) can be used. Hereinafter, the first imaging device 119a and the second imaging device 119b may be collectively referred to as an imaging device 119.

  The document placed on the document table 103 is conveyed between the lower guide 107a and the upper guide 107b in the document conveyance direction A2 by the feed roller 112 rotating in the direction of the arrow A3 in FIG. . The brake roller 113 rotates in the direction of the arrow A4 in FIG. 2 at the time of document conveyance. When a plurality of documents are placed on the document table 103 by the functions of the feeding roller 112 and the brake roller 113, among the documents placed on the document table 103, only the documents in contact with the feeding roller 112 Are separated. As a result, the transport of the originals other than the separated originals is restricted (preventing double feed). The feed roller 112 and the brake roller 113 function as a document separation unit.

  The document is fed between the first conveying roller 116 and the first driven roller 117 while being guided by the lower guide 107 a and the upper guide 107 b. The document is sent between the first imaging device 119a and the second imaging device 119b by the rotation of the first conveyance roller 116 in the direction of the arrow A5 in FIG. The document read by the imaging device 119 is discharged onto the discharge table 105 by the second conveyance roller 120 rotating in the direction of arrow A6 in FIG.

  FIG. 3A is a perspective view showing the ultrasonic amplification circuit 130. As shown in FIG. 3B is a cross-sectional view of the ultrasonic amplification circuit 130 taken along line A-A '.

  As shown in FIGS. 3A and 3B, the ultrasonic amplification circuit 130 has components such as a semiconductor package 132 and is disposed on a substrate 131. Although not shown for ease of explanation, the ultrasonic amplification circuit 130 further includes circuit components such as a resistor, a capacitor, and a coil.

  Further, an on-board shield 134 is disposed on the substrate 131 so as to cover the semiconductor package 132. The on-board shield 134 is formed of a metal such as aluminum and has a rectangular parallelepiped shape. The ultrasonic wave receiver 115 b is disposed outside the onboard shield 134.

  The semiconductor package 132 includes a semiconductor chip 133 that constitutes an amplifier. The semiconductor package 132 is formed of resin and covers the semiconductor chip 133. As the semiconductor chip 133, for example, an application specific integrated circuit (ASIC) is used. Note that, as the semiconductor chip 133, a digital signal processor (DSP), a large scale integration (LSI), a field-programming gate array (FPGA), or the like may be used.

  A wiring pattern 136 for connecting the semiconductor chip 133 and the ultrasonic wave receiver 115 b is connected to the input terminal 135 of the semiconductor chip 133. A capacitor is further connected to the branch point 137 of the wiring pattern 136. The capacitor is connected to the ultrasonic receiver 115 b and the input terminal 135 and functions as a noise filter.

  The height d [m] of the onboard shield 134 will be described below. The height of the on-board shield 134 means the distance from the inner size of the on-board shield 134, ie, the upper surface of the substrate 131, to the lower surface of the on-board shield 134 in the plane horizontal to the substrate 131. Do.

  When noise due to radio waves generated from a wireless device present around the document transport apparatus 100 is induced to the wiring pattern 136 outside the onboard shield 134, the noise generates a current and flows into the onboard shield 134. When the frequency of the current matches the resonance frequency of the ultrasonic amplification circuit 130 covered by the onboard shield 134, a very large current is generated in the ultrasonic amplification circuit 130. The generated current flows inside the semiconductor chip 133 through the input terminal 135, and is detected and demodulated at the PN junction of the semiconductor chip 133. For example, when the noise is an AM (Amplitude Modulation) modulation wave of 1 kHz, the current due to the noise is detected at the PN junction of the semiconductor chip 133 and is demodulated to a 1 kHz signal. As a result, the amplifier of the semiconductor chip 133 may malfunction, the ultrasonic signal may be amplified to an abnormal value, and a double feed detection error may occur.

  In order to prevent such an error, the resonance frequency of the ultrasonic amplification circuit 130 covered by the on-board shield 134 is not included in the range of 1 GHz or more and 5 GHz or less, which is a use band of a commonly used wireless device. Is desirable. On the other hand, the resonance frequency of the ultrasonic amplification circuit 130 covered by the onboard shield 134 changes in accordance with the height d of the onboard shield 134. Therefore, the height d of the onboard shield 134 is determined so that the resonance frequency of the ultrasonic amplification circuit 130 covered by the onboard shield 134 is not included in the range of 1 GHz or more and 5 GHz or less.

ここで、Ｔ、Ｗ及びＭは、半導体チップ１３３の入力端子１３５と、分岐点１３７に接続されてノイズフィルタとして機能するコンデンサの間の配線パターンの厚さ、幅及び長さ［ｃｍ］である。 In the wiring pattern 136 in the space covered by the on-board shield 134, the inductance R [H] is in the range R1 between the input terminal 135 of the semiconductor chip 133 and the capacitor connected to the branch point 137 and functioning as a noise filter. ] Occurs. The inductance L is calculated by the following equation (1). For the equation (1), "3.2.2.3 Ground Straps" in "NOISE REDUCTION TECHNIQUES IN ELECTRONIC SYSTEMS" (HENRY W. OTT) is referred to.

Here, T, W and M are the thickness, width and length [cm] of the wiring pattern between the input terminal 135 of the semiconductor chip 133 and the capacitor connected to the branch point 137 and functioning as a noise filter. .

ここで、Ｃ₁は、半導体チップ１３３の上面から、半導体パッケージ１３２の上面までの範囲Ｒ３に発生する静電容量［Ｆ］である。Ｃ₂は、半導体パッケージ１３２の上面から、オンボードシールド１３４の、基板１３１に対して水平な面の下面までの範囲Ｒ４に発生する静電容量［Ｆ］である。 On the other hand, the capacitance C [F] is in the range R2 from the upper surface of the semiconductor chip 133 in the space covered by the onboard shield 134 to the lower surface of the surface of the onboard shield 134 parallel to the substrate 131. Occurs. The capacitance C is calculated by the following equation (2).

Here, C ₁ from the upper surface of the semiconductor chip 133 is a capacitance generated in a range R3 to the top surface of the semiconductor package 132 [F]. C ₂ from the upper surface of the semiconductor package 132, the on-board shield 134, the capacitance [F] generated in a range R4 to the lower surface of the horizontal plane with respect to the substrate 131.

ここで、Ｓ及びｄ₁は半導体チップ１３３の面積［ｍ²］及び高さ［ｍ］であり、ｄ₂は半導体パッケージ１３２の高さ［ｍ］であり、ε₁は半導体パッケージ１３２内の樹脂の誘電率である。 The capacitance C ₁ is calculated by the following equation (3). For Formula (3), “15.1 Formula (15-4)” in “NOISE REDUCTION TECHNIQUES IN ELECTRONIC SYSTEMS” (HENRY W. OTT) is referred to.

Here, S and d ₁ are the area [m ² ] and height [m] of the semiconductor chip 133, d ₂ is the height [m] of the semiconductor package 132, and ε ₁ is the resin in the semiconductor package 132. Dielectric constant of

ここで、ε₀は真空の誘電率である。 The capacitance C ₂ is calculated by the following equation (4). For Formula (4), “15.1 Formula (15-4)” in “NOISE REDUCTION TECHNIQUES IN ELECTRONIC SYSTEMS” (HENRY W. OTT) is referred to.

Here, ε ₀ is the dielectric constant of vacuum.

The resonance frequency f ₀ [Hz] of the ultrasonic amplification circuit 130 covered by the onboard shield 134 is calculated by the following equation (5) using the inductance L and the capacitance C. For equation (5), "4.3.1 equation (4-26)" in "NOISE REDUCTION TECHNIQUES IN ELECTRONIC SYSTEMS" (HENRY W. OTT) is referred to.

Thus, the resonance frequency f ₀ changes according to the height d of the onboard shield 134. The height d of the onboard shield 134 is calculated by the following equation (6) by modifying the equations (1) to (5).

As shown in equation (6), as the height d of the onboard shield 134 is increased, the resonance frequency of the ultrasonic amplification circuit 130 covered by the onboard shield 134 is increased, and the height d is decreased. The resonant frequency f ₀ becomes smaller. As described above, it is desirable that the resonance frequency of the ultrasonic amplification circuit 130 covered by the onboard shield 134 is not included in the range of 1 GHz or more and 5 GHz or less. If it is attempted to make the height d of the onboard shield 134 smaller than the height at which the resonance frequency f ₀ becomes 1 GHz, the onboard shield 134 becomes lower than the semiconductor package 132. Therefore, the height d of the on-board shield 134 is determined so as to be larger than the height at which the resonance frequency f ₀ of the ultrasonic amplification circuit 130 becomes 5 GHz. The height d of the onboard shield 134 is determined to satisfy the following equation (7).

For example, when each parameter is as follows, the height d of the onboard shield 134 is determined to be larger than 1.2 mm.
・ Thickness T of the wiring pattern = 30 μm, width W = 0.8 mm, length M = 5.0 mm
・ Area S of the semiconductor chip 133 = 22 mm ² , height d ₁ = 0.6 mm
The height d ₂ of the semiconductor package 132 = 0.9 mm, the dielectric constant ε _{1 of the} resin = 1.2

  On the other hand, if the height d of the on-board shield 134 is too large, the device size of the document conveyance device 100 is increased. Therefore, the height d of the onboard shield 134 is set to be smaller than the height (for example, 20 mm) of the ultrasonic wave receiver.

  Hereinafter, the lengths of the sides a and b of the surface of the onboard shield 134 which is horizontal to the substrate 131 will be described. The length of each side of the on-board shield 134 in a plane horizontal to the substrate 131 is the inner dimension of the on-board shield 134, that is, the surfaces of the on-board shield 134 orthogonal to the substrate 131 and facing each other. Shall mean the distance between

  In a space surrounded by a metal wall, resonance occurs at a specific frequency. Hereinafter, the space surrounded by the metal wall may be referred to as a cavity, the resonance emitted from the cavity may be referred to as a cavity resonance, and the frequency at which the cavity resonance occurs may be referred to as a cavity resonance frequency. When cavity resonance occurs in the space surrounded by the onboard shield 134, an electromagnetic field (noise) is generated in the onboard shield 134. As a result, the amplifier of the semiconductor chip 133 may malfunction, the ultrasonic signal may be amplified to an abnormal value, and a double feed detection error may occur.

  Therefore, like the resonance frequency of the ultrasonic amplification circuit 130, the cavity resonance frequency at which the cavity resonance occurs in the space surrounded by the on-board shield 134 is 1 GHz or more and 5 GHz or less, which is a use band of commonly used wireless devices. It is desirable not to be included in the scope of On the other hand, the cavity resonant frequency changes in accordance with the sides a, b and d of the onboard shield 134. Therefore, the sides a, b and d of the onboard shield 134 are determined so that the cavity resonant frequency is not included in the range of 1 GHz or more and 5 GHz or less.

ここで、（ｓ、ｔ、ｕ）はそれぞれ０以上の整数の組合せであり、整数ｓ、ｔ、ｕの内、０となり得るパラメータは一つだけである。 The cavity resonance frequency F [MHz] at which the cavity resonance occurs in the space surrounded by the on-board shield 134 is expressed by the following equation (8). For the equation (8), “6.17 CAVITY RESONANCE” of “NOISE REDUCTION TECHNIQUES IN ELECTRONIC SYSTEMS” (HENRY W. OTT) is referred to.

Here, (s, t, u) are combinations of integers of 0 or more, and among the integers s, t and u, only one parameter can be 0.

  As shown in equation (8), as the sides a, b and d of the onboard shield 134 are reduced, the cavity resonant frequency F in the onboard shield 134 is increased, and the sides a, b and d are increased. The cavity resonant frequency F decreases as As described above, it is desirable that the cavity resonant frequency F in the on-board shield 134 is not included in the range of 1 GHz or more and 5 GHz or less.

The cavity resonance frequency F is (s, t, u) because the height d is the smallest of the sides a, b, d of the on-board shield 134 in consideration of the stability of the on-board shield 134. Is the smallest when (1, 1, 0). On the other hand, since (s, t, u) is a combination of integers of 0 or more, the maximum value of the cavity resonant frequency F can not be defined. Therefore, the sides a and b of the on-board shield 134 in the plane horizontal to the substrate 131 are set to be smaller than the length at which the cavity resonance frequency F by the on-board shield 134 is 5 GHz. Each side a, b is determined to satisfy the following equation (9).

  FIG. 4 shows that double feeding is correctly detected when a document is transported while applying radio waves (noise) having a frequency of 5 GHz to the document transport apparatus 100 using onboard shields 134 of various sizes. It is a table | surface which shows the experimental result which experimented whether it was or not.

The parameters of the document conveyance device 100 used in the experiment of FIG. 4 are as follows.
・ Thickness T of the wiring pattern = 30 μm, width W = 0.8 mm, length M = 5.0 mm
・ Area S of the semiconductor chip 133 = 22 mm ² , height d ₁ = 0.6 mm
The height d ₂ of the semiconductor package 132 = 0.9 mm, the dielectric constant ε _{1 of the} resin = 1.2

  When the height d of the onboard shield 134 is 1.2 [mm], as shown by Nos. 1 to 4 in FIG. 4, the resonance frequency is 5.0 [GHz] and is applied to the document conveyance device 100. Also, resonance due to 5 GHz noise occurred, and false detection of double feed occurred.

  Also, as shown by the numbers 4, 8, 12 and 16 in FIG. 4, when the side a of the on-board shield 134 is 40.5 mm and b is 44.5 mm, cavity resonance occurs. The frequency is 5.0 [GHz]. In this case, a cavity resonance occurred due to the noise of 5 GHz applied to the document conveyance device 100, and a false detection of double feeding occurred.

  On the other hand, as shown by the numbers 5-7, 9-11 and 13-15, the height d is 1.3 mm or more, the side a is 38.0 mm, and the side b is 42. In the case of 0 [mm], the resonant frequency and the cavity resonant frequency become larger than 5.0 [GHz]. In this case, resonance and cavity resonance due to the 5 GHz noise applied to the document feeder 100 did not occur, and false detection of double feeding did not occur. According to these experimental results, the height d of the on-board shield 134 is made larger than 1.2 [mm], the side a is made smaller than 40.5 [mm], and the side b is made smaller than 44.5 [mm] Was found to be desirable.

  FIG. 5 is a block diagram showing a schematic configuration of the document conveyance device 100. As shown in FIG.

  In addition to the configuration described above, the document feeder 100 further includes a first image A / D converter 140a, a second image A / D converter 140b, an amplifier 141, a peak hold circuit 142, a driving device 146, an interface device 147, and storage. It further includes an apparatus 150, a CPU (central processing unit) 160, and the like.

  The first image A / D converter 140 a analog-digital converts the analog image signal output from the first imaging device 119 a to generate digital image data, and outputs the digital image data to the CPU 160. Similarly, the second image A / D converter 140 b analog-digital converts the analog image signal output from the second imaging device 119 b to generate digital image data, and outputs the digital image data to the CPU 160. Hereinafter, these digital image data are referred to as a read image.

  The amplifier 141 is constituted by the semiconductor chip 133 included in the ultrasonic amplification circuit 130, amplifies the ultrasonic signal received from the ultrasonic wave receiver 115b, and outputs the amplified ultrasonic signal to the peak hold circuit 142. The amplifier 141 includes a front amplification unit 143, a filter 144, a rear amplification unit 145, and the like.

  The pre-amplification unit 143 amplifies the ultrasonic signal output from the ultrasonic sensor 115 and outputs the amplified ultrasonic signal to the filter 144. The amplification factor of the pre-amplification unit 143 can be changed by the CPU 160 and is set by the CPU 160.

  The filter 144 applies a band pass filter for passing a signal of a predetermined frequency band to the signal output from the front amplification unit 143, and outputs the signal to the rear amplification unit 145. The pass frequency band which the band pass filter passes can be changed by the CPU 160 and set by the CPU 160.

  The rear amplification unit 145 amplifies the signal output from the filter 144 and outputs the amplified signal to the peak hold circuit 142. The amplification factor by the rear amplification unit 145 can be changed by the CPU 160, and is set by the CPU 160.

  The peak hold circuit 142 generates a second ultrasonic signal obtained by peak-holding the signal output from the rear amplification unit 145, and outputs the second ultrasonic signal to the CPU 160. The peak hold circuit 142 generates the second ultrasonic signal by holding the local maximum value of the signal output from the rear amplification unit 145 for a certain hold period.

  In the present embodiment, of the ultrasonic wave receiver 115 b, the amplifier 141 and the peak hold circuit 142, only the amplifier 141 is covered by the on-board shield 134.

  The driving device 146 includes one or more motors, and rotates the feeding roller 112, the brake roller 113, the first conveying roller 116, and the second conveying roller 120 according to a control signal from the CPU 160 to convey the document. Do.

  The interface device 147 has an interface circuit conforming to a serial bus such as USB, for example, and is electrically connected to a computer (for example, a personal computer, a portable information terminal, etc., not shown) to transmit and receive read images and various information. . Further, instead of the interface device 147, a communication unit having an antenna for transmitting and receiving a wireless signal and a wireless communication interface device for transmitting and receiving a signal through a wireless communication channel in accordance with a predetermined communication protocol may be used. The predetermined communication protocol is, for example, a wireless LAN (Local Area Network).

  The storage device 150 includes a memory device such as a random access memory (RAM) or a read only memory (ROM), a fixed disk device such as a hard disk, or a portable storage device such as a flexible disk or an optical disk. In addition, the storage device 150 stores a computer program, a database, a table, and the like used for various processes of the document conveyance device 100. The computer program may be installed in the storage device 150 from a computer readable portable recording medium using a known setup program or the like. The portable recording medium is, for example, a CD-ROM (compact disk read only memory), a DVD-ROM (digital versatile disk read only memory) or the like. Further, the storage device 150 stores a read image.

  The CPU 160 operates based on a program stored in advance in the storage device 150. A DSP, an LSI, an ASIC, an FPGA, or the like may be used instead of the CPU 160.

  The CPU 160 includes an operation button 106, a first document detection sensor 111, a second document detection sensor 114, a third document detection sensor 118, a first imaging device 119a, a second imaging device 119b, a first image A / D converter 140a, It is connected to the second image A / D converter 140b, the amplifier 141, the peak hold circuit 142, the drive device 146, the interface device 147, the storage device 150 and the like, and controls these units.

  The CPU 160 performs drive control of the drive device 146, document reading control of the imaging device 119, and the like, acquires an image obtained by reading a document from the imaging device 119, and transmits the image to a computer (not shown) via the interface device 147. The CPU 160 also receives the second ultrasonic signal from the peak hold circuit 142, and detects double feed of the document using the received second ultrasonic signal. The CPU 160 determines that double feeding does not occur if the second ultrasonic signal received at the time of document conveyance is equal to or greater than the threshold, and determines that double feeding occurs if the second ultrasonic signal is less than the threshold. Do.

  FIG. 6 is a flowchart for explaining the manufacturing process of the document conveyance device 100. Hereinafter, the manufacturing process of the document conveyance device 100 will be described with reference to the flowchart shown in FIG.

  First, the ultrasonic wave receiver 115b is disposed on the substrate 131 so as to face the ultrasonic wave generator 115a (step S101). Next, the ultrasonic amplification circuit 130 including the semiconductor chip 133 constituting the amplifier 141 is disposed on the substrate 131 (step S102). Next, the height of the on-board shield 134 is set so as to be larger than the height at which the resonance frequency of the ultrasonic amplification circuit 130 is 5 GHz and smaller than the height of the ultrasonic wave receiver 115 b. Next, each side of the on-board shield 134 in a plane horizontal to the substrate 131 is set to be smaller than the length at which the cavity resonance frequency in the ultrasonic amplification circuit 130 is 5 GHz (step S103). Next, the on-board shield 134 is disposed on the substrate 131 so as to cover the amplifier 141 (step S104).

  As described above in detail, the document conveying apparatus 100 can not malfunction with respect to noise having a frequency of 1 GHz or more and 5 GHz or less while suppressing an increase in the apparatus size.

  Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments. For example, the information processing apparatus may be not an image scanner but an original conveying apparatus such as a facsimile, an inkjet printer, a laser printer, or a multifunction peripheral (MFP). The information processing apparatus may be an apparatus other than the document transport apparatus as long as the apparatus has an ultrasonic oscillator, an ultrasonic receiver, and an amplifier.

DESCRIPTION OF SYMBOLS 100 Document conveying apparatus 115a Ultrasonic oscillator 115b Ultrasonic receiver 130 Ultrasonic amplifier circuit 131 Substrate 132 Semiconductor package 133 Semiconductor chip 134 On-board shield 141 Amplifier 143 Pre-amplification part 144 Filter 145 A post-amplification part

Claims (7)

An ultrasonic generator that outputs ultrasonic waves;
An ultrasonic receiver disposed on the substrate so as to face the ultrasonic oscillator and outputting a signal according to the received ultrasonic wave;
An amplifier disposed on the substrate for amplifying a signal output from the ultrasonic receiver;
A rectangular parallelepiped on-board shield formed of metal and disposed on the substrate so as to cover the amplifier;
The height of the on-board shield is greater than the height at which the resonance frequency of the circuit including the amplifier covered by the on-board shield changes according to the height is 5 GHz, and the height of the ultrasonic receiver Less than
An information processing apparatus characterized by   The information processing apparatus according to claim 1, wherein the height of the on-board shield is larger than 1.2 mm and smaller than 20 mm. The amplifier is
A first amplification unit configured to amplify a signal output from the ultrasonic wave receiver;
A filter for passing a signal of a specific frequency band among the signals output from the first amplification unit;
The information processing apparatus according to claim 1, further comprising: a second amplification unit configured to amplify a signal output from the filter. The height d of the on-board shield satisfies the following formula:

Here, f ₀ is a value of resonance frequency and is 5 GHz,
T, W and M are the thickness, width and length of the wiring pattern between the input terminal of the semiconductor chip constituting the amplifier and the capacitor connected to the input terminal,
S and d ₁ are the area and height of the semiconductor chip,
d ₂ is the height of the semiconductor package covering the semiconductor chip;
ε ₁ is the dielectric constant of the resin in the semiconductor package,
ε ₀ is the dielectric constant of vacuum,
The information processing apparatus according to any one of claims 1 to 3.   5. Each side of a plane horizontal to the substrate of the on-board shield is smaller than a length such that a cavity resonance frequency at which a cavity resonance occurs in the space surrounded by the on-board shield is 5 GHz. The information processing apparatus according to any one of the above. Each side a, b of the plane horizontal to the substrate of the on-board shield satisfies the following equation:

Here, F is a value of the cavity resonant frequency and is 5 GHz.
The information processing apparatus according to claim 5. Method of manufacturing information processing apparatus having an ultrasonic oscillator for outputting ultrasonic waves, an ultrasonic wave receiver for outputting a signal according to received ultrasonic waves, and an amplifier for amplifying a signal output from the ultrasonic wave receiver And
Placing the ultrasound receiver on a substrate to face the ultrasound generator;
Placing the amplifier on the substrate;
The height of the rectangular parallelepiped onboard shield formed of metal is greater than the height at which the resonance frequency of the circuit covered by the onboard shield changes according to the height is 5 GHz, and the ultrasonic receiver Set to be smaller than the height of the
Placing the on-board shield on the substrate so as to cover the amplifier;
A manufacturing method characterized by

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