JPH0811111B2 - Electronic endoscope system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to an electronic endoscope apparatus provided with a means for changing image quality determining factors according to the type of solid-state image pickup element and screen enlargement / reduction processing.

[Prior Art] In recent years, an imaging device using a solid-state imaging device such as a CCD as an imaging means is widely used.

Further, also in an endoscope, a solid-state image sensor such as a CCD is provided as an image pickup unit at the tip of the insertion section to generate a drive signal for driving the solid-state image sensor and to obtain a subject obtained from the solid-state image sensor. An electronic endoscope apparatus has been proposed in which a screen is displayed on a monitor via a signal processing device that converts a signal into a television signal and the subject image displayed on the monitor is observed.

In an endoscope using the above-mentioned solid-state image sensor, as disclosed in, for example, Japanese Patent Laid-Open No. 61-179129, an endoscope having different characteristics peculiar to the solid-state image sensor is used as a single signal processing device and monitor. Is used in common, and for that purpose, a storage means for various condition information such as the type of endoscope, white balance, angle of view of the solid-state image sensor, sensitivity of the solid-state image sensor, etc. is provided, and the connector on the endoscope body side is signaled. By connecting to the connector receiver on the processing device side, the reading device of the signal processing device reads various condition information, and the information (hereinafter referred to as scope ID) is transmitted to the corresponding control unit to automatically perform various conditions. It is designed to be set.

In addition, it has been proposed that the signal processing device has functions such as enlarged display and child screen output, and devises have been made to improve the observation effect.

[Problems to be Solved by the Invention] Therefore, when the frequency of the drive signal is changed according to the type of the solid-state image pickup device, the upper limit of the band of the video signal naturally changes. Also, when signal processing such as screen enlargement processing and child screen processing is performed, the upper limit of the signal band changes. Therefore, if the image quality determining factors (enhancing frequency, enhancing level, coring level, LPF characteristics, contrast, etc.) are not changed despite the change in the upper limit of the signal band, a sufficient observation effect can be obtained with the image on the monitor. There may be cases where it is not possible. For example, if the upper limit of the band when displaying the standard angle of view is 3 MHz and the enhance frequency is set to 2 MHz, the observation effect can be improved, but the enlargement processing is performed without changing the enhance frequency to increase the band. If the upper limit of is 1.5MHz, no sufficient effect can be obtained. Also, when the type of CCD is changed and the frequency of the drive signal is lowered, the aliasing signal appears strongly unless the cutoff frequency of the LPF before A / D conversion is lowered.

The present invention has been made in view of the above points, and an electronic device that always displays an image with an optimum observation effect even when the upper limit of the band of the video signal changes depending on the type of the solid-state imaging device or the function of the signal processing device. An object is to provide a portable endoscope apparatus.

[Means and Actions for Solving Problems] According to the present invention, the frequency or drive system of the drive signal of the solid-state image sensor is changed according to the discrimination information of the type of the solid-state image sensor sent to the signal processing device, and the monitor display. Corresponding to changes in the upper limit of the signal band associated with functions such as interpolation processing, image enlargement processing, and small screen processing to make the angle of view equal regardless of the type of solid-state image sensor And changing means are provided. Accordingly, even when the solid-state image sensor is different, or even when the image is enlarged or reduced, the image quality deciding factor is set to a desired value corresponding to these, so that an image with a high observation effect can be obtained. There is.

EXAMPLES The present invention will be specifically described below with reference to the drawings.

1 to 15 relate to one embodiment of the present invention.
FIG. 1 is a block diagram of an electronic endoscope apparatus according to one embodiment, and FIG.
FIG. 3 is a schematic perspective view showing the entire apparatus of the embodiment, FIG. 3 is a perspective view showing the types of solid-state image pickup elements used in one embodiment, FIG. 4 is a configuration diagram of a CCD drive circuit, and FIG. 5 is a configuration of an LPF circuit. 6 and 6 are schematic diagrams of frequency characteristics of the LPF circuit, FIG. 7 is a block diagram of the digital signal processing circuit, FIG. 8 is a schematic diagram of frequency characteristics of the digital signal processing circuit, and FIG. 9 is contour correction. Circuit configuration diagram, FIGS. 10 and 11 are operation explanatory diagrams of the contour correction circuit, FIG. 12 is a schematic diagram of frequency characteristics of the contour correction circuit, and FIG.
Figures 14, 14 and 15 are diagrams for explaining the operation of the non-linear circuit.

As shown in FIG. 2, an electronic endoscope apparatus 1 according to one embodiment is an electronic endoscope (hereinafter referred to as an electronic scope) 2A and a fiberscope 2B with a TV camera 3 attached thereto. 2C, a signal processing device 4 for performing signal processing of these scopes 2A, 2C, a light source device 5 for supplying illumination light to both scopes 2A, 2C, and a display connected to the signal processing device 4 by a cable not shown. Monitor 6 for use.

Both of the scopes 2A, 2C (or 2B) have an elongated insertion portion 7, and an operation portion 8 is connected to the rear end of the insertion portion 7. In addition, a light guide 9 for transmitting illumination light is inserted into each insertion portion 7, and the light guide 9 is a universal cord extended from the operation portion 8 in the electronic scope 2A.
It is inserted through 11 and the incident end reaches the light guide connector 12. Further, in the fiberscope 2B, the light guide cable 13 extended from the operation portion 8 is inserted, and the incident end of the light guide 9 reaches the light guide connector 14.

The light guide connectors 12 and 14 can be connected to the connector receiver 15 of the light source device 5, as shown by the alternate long and short dash line, and the illumination light is supplied by the connection. The illumination light supplied to the light guide connectors 12 and 14 is transmitted and emitted from the emission end face arranged on the distal end side of the insertion portion 7 to the subject side through the light distribution lens.

The subject illuminated by the illumination light is imaged on its focal plane by the objective lens 17 attached to the tip of the insertion section 7. In the electronic scope 2A, the CCD 18 is arranged on the focal plane, and in the fiberscope 2B, the incident end surface of the image guide 19 is arranged.

The CCD 18 is connected to a signal transmission cable, and the signal connector 21 is attached to the cable inserted through the universal cord 11 so that it can be connected to the signal connector receiver 22 of the signal processing device 4. On the other hand, in the fiberscope 2B, the optical image is transmitted to the eyepiece 23 by the image guide 19, and the TV camera 3 mounted on the eyepiece 23 causes the CCD 2 to pass through the imaging lens in the TV camera 3.
It can be focused on 4. CCD in this TV camera 3
24 is connected to the cable in the signal cord 26, and the signal connector 27 attached to the tip of this cable can be connected to the signal connector receiver 22 of the signal processing device 4.

Used in the electronic scope 2A and TV camera 3
As the CCD 18, 24, depending on the type of the electronic scope 2A or the TV camera 3, for example, FIG. 3 (a), (b), (c)
There are various types as shown in. That is, in FIG. 3A, C of the imaging surface 28a having a large number of pixels (a large angle of view)
CD18a (or 24a) is shown, (b) shows the CCD18b (or 24b) of the imaging surface 28b with a small number of pixels (small angle of view), and (c) shows the shape of the imaging surface 28c. (A),
CCD 18c (or 24c) different from the square shown in (b) is shown.

FIG. 1 shows the configuration of an electronic endoscope apparatus of one embodiment which is compatible with scopes 2A and 2C having CCDs having different numbers of pixels or different shapes of the image pickup surface as shown in FIG.

Electronic scope 2A (or scope 2C) is a signal connector
When connected to the signal processing device 4 via the signal connector receiver 21 (27) and the signal connector receiver 22, the scope discrimination circuit 29 becomes an electronic scope.
Scope ID31 installed in 2A (2C) (CCD18,24 is the third
The type (a), (b), (c) of the drawings) is detected and transmitted to the controller 32. The controller 32 receives this and selects and presets various circuits. In the following, the description will be centered on an example in which the CCDs 18 and 24 are of the type shown in FIG.

When the controller 32 detects via the scope discrimination circuit 29 that the electronic scope is of the CCD 18a, 24a (hereinafter 24a is not specifically described) type, the controller 32 causes the CC
The D drive circuit 33 is selected so that it can drive a CCD of type (a). The drive circuit 33 is, for example, a CCD18i as shown in FIG.
Drive circuits 33a, 33b, 33c for driving (i = a, b, c) at 20MHz, 10MHz, 4MHz, respectively, and a switch SW1 for selecting them.
In the case of (a) type CCD 18a (having a large number of pixels), a 20 MHz drive circuit 53a is selected by a drive circuit selection signal from the controller 32 and drives this CCD 18a.

The output signal from the CCD 18a is amplified by the preamplifier 41 and input to the sample hold circuit 42. The sample and hold circuit 42 receives timing pulses by the controller 32 to match the output driven by 20 MHz. The output of the sample hold circuit 42 is input to the LPF circuit 43.

The LPF circuit 43 has a plurality of LPFs, as shown in FIG.
Switch SW2 to select LPF43a, 43b, 43c and LPF43i
Composed of. As shown in FIG. 6, the frequency characteristic of each LPF 43i is set so that its cutoff frequency is equal to or lower than the Nyquist frequency of the CCD output signal. Therefore, 20
For the output signal driven by MHz, the switch SW2 is switched by the LPF selection signal from the controller 32, and the LPF 43a having the cutoff frequency of 10 MHz is selected. The output of the LPF circuit 43 is input to the contour correction circuit 44.

The output of the contour correction circuit 44 is input to the γ correction circuit 47 via the AGC circuit 45 and the white balance circuit 46. In the γ correction circuit 47, in addition to the correction by the preset value, the operation panel 48
It is possible to manually change the γ curve and switch the contrast by sending the signal from the controller 32 to the controller 32 via the CPU 49. The output of the γ correction circuit 47 is input to the LPF circuit 51. The LPF circuit 51 is configured similarly to the LPF circuit 43 (see FIG. 5), and is installed as an anti-aliasing filter (filter for eliminating aliasing noise) before A / D conversion. The frequency characteristic of the LPF circuit 51 is also controller 32
The cutoff frequency is 10MHz or less for the output signal driven by 20MHz. L
The output of the PF circuit 51 is A / D converted by the A / D converter 52. The clock applied to the A / D converter 52 is selected by the controller 32, and about 20MHz for the output signal driven by 20MHz.
A / D conversion will be performed with the clock. The signal digitally converted by the A / D converter 52 is temporarily stored in the memory 53 and then read out. The functions of the memory 53 are a time base collector, image freeze, and the like.

The output of the memory 53 is input to the digital signal processing circuit 54. As shown in FIG. 7, the digital signal processing circuit 54 has a magnifying display function for magnifying, for example, 1.5 times, 2 times, and 3 times, and the first, second, and third magnifying circuits 54 having different magnifying powers, respectively.
Switches SW3, SW4 for switching a, 54b, 54c and signal line
It is composed of The input signal is expanded by the expansion circuit 54 so as to be expanded on the time axis. That is, when a mountain-shaped signal as shown on the left side of FIG.
The signal waveform is enlarged on the time axis by i and becomes the signal waveform shown on the right side of FIG. Therefore, the band of the output signal changes as shown in FIG.

That is, the band of the input signal changes to the signal band divided by the expansion rate according to the expansion rate of the expansion circuit 54i.

The output of the digital signal processing circuit 54 is the D / A converter 55.
Is D / A converted by and input to the LPF circuit 56. The LPF circuit 56 has the same configuration as the LPF circuit 43, and the frequency characteristics can be switched by the controller 32. However, each of the cutoff frequencies of the internal components of the LPF circuit 56 is determined by the combination of the CCD drive frequency and the frequency characteristic of the expansion circuit 54i of the digital signal processing circuit 54. The output of the LPF circuit 56 is input to the contour correction circuit 57.

The contour correction circuit 57, as shown in FIG.
60, a switch 61 for selecting this delay amount, a second delay means 62, a switch 63 for selecting this delay amount, and an adder
64, 65, 66, amplifiers 67, 68, and a non-linear circuit 69. The input signal and the signals delayed by the first and second delay means 60 and 62 are added by the adder 64. Thereafter, the signal is multiplied by −1/2 in the amplifier 67 and added to the signal delayed by the first delay means 60 in the adder 65 to obtain a signal having a waveform as shown in FIG. 9A, which is multiplied by α in the amplifier 68. It The amplification rate α can be arbitrarily set by an emphasis level setting signal from the controller 32. The output of the amplifier 68 is added to the output of the delay means 60 by an adder 66 via a non-linear circuit 69 which will be described in detail later, and becomes the output of the contour correction circuit 57. Here, the output of the first delay means 60 having a short delay time is connected to the a terminal of the switch 61, and the outputs having a long delay time are connected to the b, c, d, and e terminals. The same applies to the output of the second delay means 62, and the delay time of the second delay means 62 connected to a ', b', c ', d', e'of the switch 63 is a. , b, c,
Same as d and e. Therefore, when the switch 61 selects a, the switch 63 selects a '. switch
61 and 63 can be switched by a delay amount setting signal from the controller 32. Figure 10 shows the difference in output signal depending on the amount of delay. Compared to the signal shown in FIG. 10 (A), FIG. 10 (B) shows a case where the delay amount is medium. When the upper limit of the signal band becomes low, the delay amount is increased to increase the delay amount.
When the emphasis frequency is set low as shown in FIG. 10C and the upper limit of the signal band becomes high, the emphasis frequency can be set high as shown in FIG. 10D by reducing the delay amount.
Therefore, the frequency characteristics of the signal processing system are changed to B, C, and D in FIG. 12 (c) by changing the emphasis frequency to B, C, and D in FIG. 12 (a) according to the upper limit of the signal band. Can be like D. As a result, the image has no unnaturalness and the observation effect can be enhanced. (Here, B, C and D correspond to B, C and D in FIG. 10.) Next, regarding the amplifier 68, a differential signal as shown in FIG. The contour emphasis level can be adjusted by setting to. Fig. 11 shows the difference in the output signal depending on the magnitude of the emphasis level. 11th
With respect to the signal of FIG. 7A, FIG. 7B shows the case where the emphasis level is medium, FIG. 8C shows the case where the emphasis level is increased, and FIG. This is an example when the emphasis level is weakened. In the present invention, the strength of this emphasis level is also switched according to the signal band. The factors that change the signal band are the change of the driving frequency of the CCD and the image enlargement processing as described above. However, when the image enlargement processing is performed, image blurring occurs as an interpolation effect. In this case, it is preferable to increase the contour enhancement level for contour correction. Therefore, when the signal band becomes low due to the image enlargement processing, not only the contour emphasis frequency is lowered, but also the contour emphasis level is correspondingly strengthened. Figure 12 (b)
Shows the frequency characteristic of the contour correction circuit in this case. E in the figure shows the case where the emphasis frequency is made low and the emphasis level is made strong, and F in the figure shows the case where the emphasis frequency is high and the emphasis level is weak. Incidentally, B'corresponds to B'in FIG. Also, by changing the emphasis frequency as described above,
As shown by F'in FIG. 12 (d), the frequency component higher than the limit of the signal band-limited by the LPF is not emphasized. In addition, the observation effect can be enhanced by deliberately changing the emphasis frequency by inputting from the operation panel 48 to obtain the frequency characteristic as shown by G'in FIG. 12 (d).

As described above, the output of the amplifier 68 is input to the adder 66 via the non-linear circuit 69. Next, the non-linear circuit 69 will be described. The nonlinear circuit 69 has an output characteristic as shown in FIG. 13 (a). Therefore, low level signals can be suppressed as shown in FIG. By providing this circuit at the position shown in FIG. 9, it is possible to suppress low-level edge enhancement components that are generated by noise components included in the input signal, and reduce the roughness of the screen. . FIG. 15 is an explanatory diagram of the operation. Noise components (shown by diagonal lines) in the contour correction circuit 57 as shown in FIG.
It is assumed that there is a signal input including. Then the nonlinear circuit
The input of 69 becomes a signal as shown in FIG. 15 (b), which also includes an emphasis component for the noise component. A low level signal of this signal is suppressed by the input / output characteristics of the non-linear circuit 69 as shown in FIG. 15 (c), and is shaped into a signal as shown in FIG. 15 (d). Therefore, the output obtained by adding the original signal and the emphasized signal in the adder 66 is as shown in FIG. 15 (e), and the emphasized signal for the noise component is suppressed. Furthermore, since the enhancement level can be changed even by using the non-linear circuit 69, a description will be added. By changing the slope of the linear portion of the input / output characteristic shown in FIG. 13 (a) as shown by the dotted line in FIG. 13 (b), the operation of the amplifier circuit 68 can also be performed. Also,
The suppression level may be changed as shown in FIG. Therefore, instead of changing the amplification factor of the amplifier 68 in response to the change in the upper limit of the signal band, it is possible to change the emphasis level by changing the characteristics of the nonlinear circuit 69 as described above. Further, the non-linear circuit 69 may be composed of a large number of broken lines.

The output of the contour correction circuit 57 reaches the monitor 6 via a buffer (not shown) and can be observed as an image.

The outline correction circuit 57 has the same basic configuration as the outline correction circuit 44 provided in the preceding stage, and the operation thereof is also the same.

For convenience of explanation in the above description, the drive frequency of the CCD drive circuit 33 and the LPF (43a of the components of the LPF circuits 43, 51, 56
However, the values are not limited to the above-described frequency characteristics and the enlargement ratio of the image enlargement processing circuit 54, but these values may be set arbitrarily. Also, the controller 32
The number of components switched by is not limited to three types, and the number of components is arbitrary.

The present invention can be applied to both a color filter built-in type in which a color filter such as a mosaic color filter is provided on the front surface of a CCD as a color image pickup means and a frame sequential type in which no color filter is provided.

Further, the present invention is not limited to the case of performing the enlargement signal processing, but can be applied to the case of performing the reduction signal processing as well as the case of superimposing and displaying the child screen on the parent screen.

[Effects of the Invention] As described above, according to the present invention, even when a signal processing system in which the upper limit of the signal band for changing the driving frequency of the CCD and image enlarging processing is changed, A means is provided to change the image quality determining factor in response to changes in the upper limit of the signal band, so even when various signal processing is performed on various CCD outputs, the optimum environmental condition is always maintained for that signal. Gives a good quality image.

[Brief description of drawings]

1 to 15 relate to one embodiment of the present invention, FIG. 1 is a configuration diagram of an electronic endoscope apparatus of one embodiment, and FIG. 2 is a schematic perspective view showing the entire apparatus of one embodiment. FIG. 3 is a perspective view showing the types of solid-state image sensor used in one embodiment, and FIG.
CCD drive circuit configuration diagram, FIG. 5 is LPF circuit configuration diagram, 6th
FIG. 7 is a characteristic diagram showing the outline of the frequency characteristic of the LPF circuit, FIG. 7 is a configuration diagram of the digital signal processing circuit, and FIG. 8 is a characteristic diagram showing the outline of the frequency characteristic of the digital signal processing circuit.
The figure is a block diagram of the contour correction circuit, FIGS. 10 and 11 are explanatory diagrams of the operation of the contour correction circuit, and FIG. 12 is a characteristic diagram showing the outline of the frequency characteristic of the contour correction circuit, FIGS. 13 and 14. And FIG. 15 is an operation explanatory view of the non-linear circuit. 1 ... Electronic endoscope device, 2A ... Electronic scope 2B ... Fiberscope 2C ... Fiberscope with external camera 3 ... TV camera, 4 ... Signal processing device 5 ... Light source device, 6 ... Monitor 18, 24 …… CCD, 33 …… CCD drive circuit 42 …… Digital signal processing circuit 43,51,56 …… LPF (low pass filter) 44,57 …… Contour correction circuit

Front page continuation (72) Inventor Katsuyuki Saito 2-43-2 Hatagaya, Shibuya-ku, Tokyo Olympus Optical Co., Ltd. (72) Inventor Masahiko Sasaki 2-43-2 Hatagaya, Shibuya-ku, Tokyo Olympus Optics Kogyo Co., Ltd. (72) Inventor Masahide Kanno 2-43-2 Hatagaya, Shibuya-ku, Tokyo Olympus Optical Co., Ltd. (72) Inventor Jun Hasegawa 2-43-2 Hatagaya, Shibuya-ku, Tokyo Olympus Optics Kogyo Co., Ltd. (72) Inventor Katsuyoshi Sasakawa 2-43-2 Hatagaya, Shibuya-ku, Tokyo Olympus Optical Co., Ltd. (56) Reference JP-A-221135 (JP, A)

Claims (1)

[Claims] 1. An electronic endoscope apparatus having an image pickup means using a solid-state image pickup element and a signal processing system for converting a signal read from the solid-state image pickup element into a predetermined video signal, wherein the image pickup means outputs the signal. A / D conversion means for converting the captured image signal into a digital signal, memory means for storing the captured image signal digitally converted by the A / D conversion means, and interpolation for the captured image signal stored in the memory means. Enlarging processing means for enlarging processing, enlarging rate setting means for changing the amount of interpolation in the enlarging processing means to set an enlarging rate, and a contour for receiving an output signal of the enlarging processing means and performing edge enhancing processing on the output signal. An electronic expression comprising: a correction unit; and a contour correction control unit that sets an emphasis frequency and an emphasis amount in the contour correction unit corresponding to the enlargement ratio set by the enlargement ratio setting unit. Endoscopic device.