JP2008211780A - Imaging apparatus and information code reading apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image pick-up device and an information code-reading device configured to simplify their optical system and to reduce their costs while suppressing fluctuations of resin lenses and deterioration of lens performances caused by its expansion. <P>SOLUTION: An optical system 210 is comprised of a second lens 212 made of resin and the other lenses made of glass lens. The power of the resin lens is small in comparison with that of the glass lens, wherein each power is set to be small in comparison with that of the optical system 210. A lens frame constructing member 300 is comprised independently of a lens holding unit 310 and an image pick-up element holding unit 320, the lens holding unit 310 and the image pick-up element holding unit 320 are fixed by an intermediate member 330, and fixing positions of the lens holding unit 310 and the image pick-up element holding unit 320 can be adjusted by the intermediate member 330. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an imaging apparatus and an information code reading apparatus using an imaging element and including an optical system.

In response to the digitization of information, which has been rapidly developing in recent years, the response in the video field is also remarkable.
In particular, as symbolized by a digital camera, a CCD (Charge Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor) sensor, which is a solid-state image sensor, is used in most cases instead of a conventional film.

  As described above, an imaging lens device using a CCD or CMOS sensor as an imaging element is for taking an image of a subject optically by an optical system and extracting it as an electrical signal by the imaging element. In addition to a digital still camera, It is used in video cameras, digital video units, personal computers, mobile phones, personal digital assistants (PDAs), image inspection devices, industrial cameras for automatic control, and the like.

FIG. 24 is a diagram schematically illustrating a configuration and a light flux state of a general imaging lens device.
The imaging lens device 1 includes an optical system 2 and an imaging element 3 such as a CCD or CMOS sensor.
In the optical system, the object side lenses 21 and 22, the diaphragm 23, and the imaging lens 24 are sequentially arranged from the object side (OBJS) toward the image sensor 3 side.

In the imaging lens device 1, as shown in FIG. 24, the best focus surface is matched with the imaging element surface.
25A to 25C show spot images on the light receiving surface of the imaging element 3 of the imaging lens device 1.

In addition, imaging devices have been proposed in which light beams are regularly dispersed by a phase plate and restored by digital processing to enable imaging with a deep depth of field (for example, Non-Patent Documents 1 and 2 and Patent Documents). 1-5).
In addition, an automatic exposure control system for a digital camera that performs filter processing using a transfer function has been proposed (see, for example, Patent Document 6).

In addition, in an apparatus having an image input function such as a CCD or CMOS, it is often very useful to read a close still image such as a barcode together with a desired image such as a landscape.
For barcode reading, for example, as a first example, a technique for focusing by auto-focusing that extends a lens, and as a second example as a depth expansion technique, the depth of field is expanded by, for example, reducing the F value in a camera. Some have fixed focus.
Furthermore, a method for increasing the in-focus field is disclosed in Patent Document 8, for example.

“Wavefront Coding; jointly optimized optical and digital imaging systems”, Edward R. Dowski, Jr., Robert H. Cormack, Scott D. Sarama. “Wavefront Coding; A modern method of achieving high performance and / or low cost imaging systems”, Edward R. Dowski, Jr., Gregory E. Johnson. USP 6,021,005 USP 6,642,504 USP 6,525,302 USP 6,069,738 JP 2003-235794 A JP 2004-153497 A JP 2004-37733 A JP 2002-27047 A

In the imaging devices proposed in the above-mentioned documents, all of them are based on the assumption that the PSF (Point-Spread-Function) when the above-described phase plate is inserted into a normal optical system is constant, When the PSF changes, it is extremely difficult to realize an image with a deep depth of field by convolution using a subsequent kernel.
Therefore, apart from a single-focus lens, a zoom system, an AF system, or the like has a great problem in adopting due to the high accuracy of the optical design and the associated cost increase.
In other words, in the conventional imaging apparatus, proper convolution calculation cannot be performed, and astigmatism and coma that cause a shift of a spot (SPOT) image at the time of wide or tele (Tele). Therefore, an optical design that eliminates various aberrations such as zoom chromatic aberration is required.
However, the optical design that eliminates these aberrations increases the difficulty of optical design, causing problems such as an increase in design man-hours, an increase in cost, and an increase in the size of the lens.

In the above technique, a desired depth of field can be obtained at room temperature, but the back focus (at the image sensor side surface of the final lens arranged closest to the image sensor side) can be obtained at high and low temperatures. The interval between the image sensors changes, and the focus position changes.
Furthermore, if the resin lens has a strong power, the performance change due to the temperature change is remarkably high, and sufficient image quality cannot be obtained even if the restoration process is performed.
Furthermore, if the linear expansion of the resin lens and the lens holding portion is different, the lens may be rattled or cracked due to the difference in the expansion coefficient associated with the temperature change.

  The present invention can simplify the optical system and can reduce the cost, and also can suppress the fluctuation of the resin lens, can suppress the deterioration of the lens performance due to the expansion, and can reduce the noise of an appropriate image quality. It is an object of the present invention to provide an image pickup apparatus and an information code reading apparatus that can obtain a restored image that is less influenced by the above.

  An imaging apparatus according to a first aspect of the present invention includes a fixed-focus optical system including glass and resin lenses, an imaging element that captures a subject image that has passed through the optical system, the optical system, and the imaging element. A lens frame structure section that holds the lens frame structure section, and the lens frame structure section includes a lens holding section that holds each lens of the optical system, and an image sensor holding section that holds the image sensor. The holding unit and the image sensor holding unit can be fixed at a plurality of locations.

  Preferably, the back focus at room temperature is not changed, and the back focus is longer than that at normal temperature due to the temperature condition in which the lens unit including the optical system, the imaging element, and the lens frame structure is used. Can be selected and fixed from the plurality of positions on the imaging element side, and when the back focus is shorter than that at room temperature, the object side can be selected.

  Preferably, when the sum of the powers of the resin lenses included in the optical system is negative and the back focus is shorter than normal temperature and short, the object side is selected and fixed from the plurality of fixed locations, and the back focus is When the temperature is lower than normal temperature and long, the image sensor side is selected from the plurality of fixing points and fixed.

  Preferably, when the sum of the powers of the resin lenses included in the optical system is positive and the back focus is longer than normal temperature, the image pickup device side is selected and fixed from the plurality of fixed locations, and the back focus is selected. When the temperature is lower than normal temperature and short, the object side is selected from the plurality of fixing points and fixed.

  Preferably, the lens frame structure portion includes an intermediate member capable of fixing the lens holding portion at one end side and fixing the imaging element holding portion at the other end side, and the lens holding portion and the imaging element holding portion. The fixing position can be adjusted by the intermediate member.

  Preferably, the power of the optical system is set so that the power of the resin lens is smaller than the power of the glass lens, and the power of the resin lens is smaller than the power of the optical system.

  Preferably, the subject dispersion image picked up by the image pickup device is an image in which a focus is not achieved on the image pickup device and a light beam and a blur portion having a deep depth are formed, and is distributed from the subject dispersion image signal from the image pickup device. An image processing unit for generating an image signal having no image.

  Preferably, the optical system includes at least an object-side first lens and a second lens disposed closer to the imaging element than the first lens, and the first lens is formed of a glass lens, and the second lens The lens is formed of a resin lens.

  Preferably, in the optical system, a first lens, a second lens, a third lens, and a fourth lens are arranged in this order from the object side, and the first lens is formed of a glass lens, and the second, second lenses Among the third and fourth lenses, at least the second lens is formed of a resin lens.

  Preferably, the optical system has a light wavefront modulation function, and when the light wavefront modulation function has the optical axis of the optical system as a z-axis and two axes orthogonal to each other as x and y, the phase is as follows: It is expressed by an expression.

  According to a second aspect of the present invention, there is provided an imaging device according to the first aspect, an information code decoder that decodes an image signal of an information code that has been imaged and processed by the imaging device, and the imaging device. An information code reading device comprising: an information code decoding unit that decodes an image signal of an information code that has been imaged and processed; and a data transmission unit that transmits the decoded data to an external data processing device.

According to the present invention, the optical system can be simplified, the cost can be reduced, the fluctuation of the resin lens can be suppressed, the deterioration of the lens performance due to the expansion can be suppressed, and an appropriate There is an advantage that it is possible to obtain a restored image with less influence of noise on the image quality.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is an external view showing an example of an information code reading apparatus according to an embodiment of the present invention.
2A to 2C are diagrams illustrating examples of information codes.
FIG. 3 is a block diagram illustrating a configuration example of an imaging apparatus applied to the information code reading apparatus of FIG.

As shown in FIG. 1, the information code reader 100 according to the present embodiment has a main body 110 connected to a processing device such as an electronic register (not shown) via a cable 111, for example, a reflectance printed on a reading object 120. It is a device that can read the information code 121 such as a different symbol or code.
As an information code to be read, for example, a one-dimensional bar code 122 such as a JAN code as shown in FIG. 2A, a stack-type CODE 49 as shown in FIGS. 2B and 2C, Alternatively, a two-dimensional barcode 123 such as a matrix type QR code can be used.

In the information code reading apparatus 100 according to the present embodiment, an illumination light source (not shown) and an imaging apparatus 200 as shown in FIG.
As will be described in detail later, the imaging apparatus 200 applies a light wavefront modulation element to the optical system, regularly disperses the light beam by the light wavefront modulation element, and restores the image by digital processing to capture an image with a deep depth of field. The system adopts a wavefront aberration control optical system or a depth expansion optical system (DEOS: Optical System) that makes possible a one-dimensional barcode such as a JAN code and a two-dimensional barcode such as a QR code. An information code such as a bar code can be accurately read with high accuracy.

As shown in FIG. 3, the imaging device 200 of the information code reader 100 includes an optical system 210, an imaging device 220, an analog front end unit (AFE) 230, an image processing device 240, a camera signal processing unit 250, and an image display memory 260. , An image monitoring device 270, an operation unit 280, and a control device 290.
The image signal of the information code imaged and processed by the imaging device 200 is decoded by an information code decoding unit (not shown), and the decoded data is transmitted from the data transmission unit (not shown) via the cable 111 or wireless communication. Is transmitted to a data processing device such as an electronic register (not shown).

FIG. 4 is a diagram showing a basic configuration of the imaging lens unit forming the optical system according to the present embodiment.
The optical system 210 </ b> A supplies an image obtained by capturing the subject object OBJ to the image sensor 220. The optical system 210 </ b> A includes a first lens 211, a second lens 212, a diaphragm 213, a third lens 214, and a fourth lens 215.
In the optical system 210A, a first lens 211, a second lens 212, a diaphragm 213, a third lens 214, and a fourth lens 215 are arranged in this order from the object side.
In the optical system 210A of the present embodiment, the third lens 214 and the fourth lens 215 are connected. That is, the lens unit of the optical system 210A of the present embodiment is configured to include a cemented lens.

The optical system 210 according to the present embodiment is configured as an optical system corresponding to a temperature change.
The first lens 211, the third lens 214, and the fourth lens 215 on the side in contact with the object are made of glass, and the second lens 212 is made of resin.
And the linear expansion is large compared to glass, and even if the usage environment extends from low temperature to high temperature by controlling the power of the resin lens that reacts sensitively to temperature changes, sufficient performance can be ensured, Further, the depth extension optical system is configured to be able to reduce the temperature change of the depth of field.

More specifically, the first lens 211, the third lens 214, and the fourth lens 215 are made of glass, the second lens 212 is made of resin, and the power of the resin lens is smaller than the power of the glass lens. In addition, the power is set to be smaller than the power of the optical system 210A.
Furthermore, in the optical system 210A, it is desirable that the linear expansion coefficient of the portion (holder) 210a that holds the lens is set to be smaller than that of the resin lens.

In the optical system 210A of this embodiment, instead of providing the light wavefront modulation element separately from the lens, for example, the second lens 212 has the function.
A central portion around the optical axis of the surface on the imaging surface side of the second lens 212 is formed in a concave shape with a predetermined curvature. With this shape, the second lens 212 functions as a light wavefront modulation element. Have.

FIG. 5 is a defocus diagram of an analog spot image in which the resin lens has a strong negative power.
FIG. 6 is a defocus diagram of an analog spot image in which the resin lens has a strong positive power.
FIG. 7 is a defocus diagram of an analog spot image in which the power of the resin lens is suppressed as in the optical system of the present embodiment.

As shown in FIGS. 5 and 6, analog spot images with a strong negative or positive power of the resin lens are different at normal temperature, high temperature side, and low temperature side, and sufficient performance cannot be ensured.
On the other hand, in the optical system 210A of the present embodiment, each power is set so that the power of the resin lens is smaller than the power of the glass lens and smaller than the power of the optical system 210A. As shown in FIG. 7, even if the usage environment extends from low temperature to high temperature, sufficient performance can be ensured, and further, the temperature change of the depth of field can be reduced in the depth extension optical system. .

  In the optical system 210A, the aspherical shape of the lens is positive in the direction from the object side to the image surface side, k is a conical coefficient, A, B, C, and D are aspherical coefficients, and r is a central radius of curvature. Is expressed by the following equation. h represents the height of the light beam, and c represents the reciprocal of the central radius of curvature. Where Z is the depth from the tangent plane to the surface vertex, A is the fourth-order aspheric coefficient, B is the sixth-order aspheric coefficient, C is the eighth-order aspheric coefficient, and D is the tenth-order aspheric coefficient. Each aspheric coefficient is shown.

また、α、βは位相面係数であり、ｘ、ｙは図４に示す方向である。

Α and β are phase plane coefficients, and x and y are directions shown in FIG.

  By adopting the above configuration, a target imaging lens can be realized.

Further, as shown in FIG. 4, in the imaging lens unit 210A of the present embodiment, the center curvature radius of the object side surface 1 of the first lens 211 is R1, and the center curvature radius of the image surface side 2 of the first lens 211 is R2. And the center radius of curvature of the object side surface 3 of the second lens 212 is R3, the center radius of curvature of the image side surface 4 of the second lens 212 is R4, the aperture is 213, and the center of the object side surface 5 of the third lens 214 is The curvature radius is R5, the central curvature radius of the image surface side surface 6 of the third lens 214 is R6, the central curvature radius of the image surface side surface 7 of the fourth lens 215 is R7, and the fourth curvature of the cover glass 221 of the imaging unit 220 is fourth. The center curvature radius of the surface 8 on the lens 215 side is set to R8, and the center curvature radius of the surface 9 on the image sensor 222 side of the cover glass 221 is set to R9. The center curvature radii R8 and R9 of the both surfaces 8 and 9 of the cover glass 221 are zero.
The refractive index of the first lens 211 is n1, the dispersion value is ν1, and the refractive index of the second lens 212 is n2.
The dispersion value is ν2, the refractive index of the third lens 214 is n3, the dispersion value is ν3, the refractive index of the fourth lens 215 is n4, and the dispersion value is ν4.

In the imaging element 220, a glass parallel plane plate (cover glass) 221 and an imaging surface 222 of an imaging element such as a CCD or CMOS sensor are arranged in this order from the fourth lens 215 side.
Light from the subject OBJ via the imaging optical system 210 is imaged on the imaging surface 222 of the imaging element 220.
Note that the subject dispersion image picked up by the image pickup device 220 is an image in which a deep light beam and a blurred portion are formed without being focused on the image pickup device 220.
And in this embodiment, it is comprised so that the resolution of the distance between two objects can be complemented by adding a filter process in the image processing apparatus 240. FIG.
The optical system 210 will be described in detail later.

The image sensor 220 forms an image captured by the optical system 210, and outputs the primary image information of the image formation as the primary image signal FIM of the electrical signal to the image processing device 240 via the analog front end unit 230. And a CMOS sensor.
In FIG. 3, the imaging element 220 is described as a CCD as an example.

The analog front end unit 230 includes a timing generator 231 and an analog / digital (A / D) converter 232.
The timing generator 231 generates the drive timing of the CCD of the image sensor 220, and the A / D converter 232 converts an analog signal input from the CCD into a digital signal and outputs it to the image processing device 240.

An image processing apparatus (two-dimensional convolution means) 240 constituting a part of the signal processing unit inputs a digital signal of a captured image coming from the previous AFE 230, performs two-dimensional convolution processing, and performs subsequent camera signal processing. Part (DSP) 250.
Filter processing is performed on the optical transfer function (OTF) according to the exposure information of the image processing device 240 and the control device 290. Note that aperture information is included as exposure information.
The image processing device 240 performs a filtering process so as to improve the response of the optical transfer function (OTF) to a plurality of images by the image sensor 220 and eliminate the change of the optical transfer function (OTF) according to the object distance. It has a function of performing (for example, convolution filter processing) and obtains a deep depth of field while depending on a plurality of object distances. Further, the image processing apparatus 240 has a function of performing noise reduction filtering in the first step.
The image processing device 240 has a function of performing processing for improving the contrast by performing filter processing on the optical transfer function (OTF).
The processing of the image processing device 240 will be described in further detail later.

  The camera signal processing unit (DSP) 250 performs processing such as color interpolation, white balance, YCbCr conversion processing, compression, and filing, and stores the data in the memory 260 and displays the image on the image monitoring device 270.

  The control device 290 performs exposure control and has operation inputs from the operation unit 280 and the like, determines the operation of the entire system in accordance with those inputs, and controls the AFE 230, the image processing device 240, the DSP 250, the aperture 213, and the like. It governs mediation control for the entire system.

  Further, in the so-called lens frame structure units 300 and 300A in this embodiment, basically, as shown in FIGS. 8, 9, and 10, a lens holding unit 310 and an image sensor holding unit 320 are separately configured. The lens holding unit 310 and the image sensor holding unit 320 are fixed by an intermediate member 330, and the lens holding unit 310 and the image sensor holding unit 320 are configured to be adjusted by the intermediate member 330. Yes. By controlling the fixed position, it is possible to control the back focus position shift and ensure sufficient performance even if the usage environment ranges from low temperature to high temperature. Further, the DEOS (Depth Extension Optical System) is configured so that the temperature change of the depth of field can be reduced.

The lens holding unit 310 is formed, for example, in a cylindrical shape, and holds, in order from the object side, a first holding unit 311 that holds the first lens 211, a second holding unit 312 that holds the second lens 212, and a third lens 214. A third holding portion 313 and a fourth holding portion 314 for holding the fourth lens 215 are formed.
The object side from the axial center of the outer side of the lens holding portion 310 is fixed to one end portion of the intermediate member 330 by, for example, an adhesive 340.
The lens holding part 310 is made of, for example, resin.

The image sensor holding unit 320 is formed in a cylindrical shape having an outer diameter larger than the outer diameter of the lens holding unit 310, the central part is opened in the axial direction, and the image sensor 220 is fixed to the bottom surface side (first surface side) 321. Has been.
In addition, one end 335 of the intermediate member 330 is fixed to the upper surface side (object side surface) 322 of the image sensor holding unit 320 with an adhesive or the like.
The image sensor holding unit 320 is made of, for example, resin.

The intermediate member 330 is formed in a cylindrical shape having an inner diameter larger than the outer diameter of the lens holding portion 310, and the side wall 331 includes a plurality of (three in the present embodiment) through holes at predetermined intervals in the axial direction. Fixed portions 332 to 334 are formed. A plurality of the fixing portions 332 to 334 are formed at predetermined intervals on the circumference.
Further, a flange 335 is formed at the other end of the intermediate member 330 so as to extend inward, and an outer surface (bottom surface) of the flange 335 is in contact with the upper surface side 322 of the image sensor holding unit 320. Is fixed.
The intermediate member 330 is formed of, for example, resin or metal, such as aluminum (Al).

  As described above, in the lens frame structure units 300 and 300A of the present embodiment, the image sensor holding unit 320 and the lens holding unit 310 are fixed, the optical system has a fixed focus, and the back focus at normal temperature is not changed. In addition, by changing the fixed positions of the lens holding unit 310 and the image sensor holding unit 320, a mechanism can be provided that can reduce fluctuations in the back focus position due to temperature changes without having a drive mechanism.

  In the present embodiment, when the sum of the powers of the resin lenses included in the optical system 210 is negative, the distance between the imaging element 220 side of the fourth lens 215 that is the final lens and the imaging element 220 is higher than room temperature. It is configured to be shorter at high temperatures and longer at low temperatures.

In the present embodiment, when the sum of the powers of the resin lenses included in the optical system 210 is positive, the distance between the imaging element 220 side surface of the fourth lens 215 that is the final lens and the imaging element is higher than room temperature. It is configured to become longer and shorter at low temperatures.

  As described above, in this embodiment, the power of the resin lens is suppressed at the time of lens design to suppress the variation of the resin lens due to temperature, and the lens holding unit 310 and the image sensor holding unit 320 are separate. In addition, the lens holding unit 310 and the image sensor holding unit 320 fixed by the intermediate member 330 are made variable so that performance deterioration of back focus fluctuation due to temperature is suppressed.

  Here, a temperature-considering design in which the fixing positions of the image sensor holding unit 320 and the lens holding unit 310 are changed will be described.

For example, as shown in FIG. 8, the lens frame structure 300 and 300 </ b> A can be adjusted at three positions, and the lens is designed in the temperature range from room temperature to a certain temperature at the position <2> (fixing portion 333). Assume that the performance can be secured. Even if the temperature becomes high, the distance between the lens final surface, that is, the surface of the fourth lens 215 and the image sensor surface is appropriately shortened with reference to the fixed position. However, when the lens becomes a positive lens with a strong sum of the powers of the resin lenses, the back extends as a lens frame at a high temperature, and the positive power of the lens becomes weak, resulting in a long back focus. In that case, as shown in FIG. 9, it is preferable to fix to the position of <3> (fixing part 334).
If it is fixed at the position <3>, the distance between the lens final surface and the surface to the image sensor is not canceled out.
Conversely, at low temperatures, the back contracts as a lens frame, and as a lens, positive power increases and short back focus is achieved. In that case, as shown in FIG. 9, it is preferable to fix to the position of <1> (fixing part 332).

When the lens becomes a negative lens with a strong sum of the powers of the resin lenses, the back extends as a lens frame at a high temperature, and the negative power weakens as the lens, resulting in a short back focus.
In that case, as shown in FIG. 10, it is preferable to fix to the position of <1> (fixing part 332). If it is fixed at the position <1>, the distance between the surface of the fourth lens 215, which is the final lens surface, and the surface to the image sensor 220 can be offset and further shortened.
Conversely, at low temperatures, the back contracts as a lens frame, and as a lens, the negative power increases, resulting in a long back focus. In that case, as shown in FIG. 10, it is preferable to fix to the position of <3> (fixing part 334).

In the configuration of FIG. 8, the resin of the lens holding part 310 is assumed to be, for example, PCGF20 (linear expansion coefficient 0.000065). With respect to the lens holding portion 310, for example, it is preferable to control the linear expansion coefficient by adding glass to a resin and to change the fixing position.

In the present embodiment, it is possible to use a fixing method using an adhesive that cures when irradiated with ultraviolet rays, and it is also possible to use a fixing method using a screw.
When using a fixing method using an adhesive, the lens holding part (barrel) can be fixed freely (for example, after adjusting in a non-parallel direction to the optical axis), and a fixing method using screws is used. Can suppress the influence of aging conversion that may occur when an adhesive is used.

Examples 1 and 2 according to specific numerical values of the imaging lens unit 210A are shown below.
In each of the first and second embodiments, the lenses 211, 212, 214, and 215 that constitute each lens group of the imaging lens unit 210A and the cover glass 221 that constitutes the imaging element 220 are shown in FIG. Surface numbers as shown are given.

(Example 1)
Tables 1 and 2 show the numerical values of Example 1. Each numerical value in the example corresponds to the imaging lens unit 210A in FIG. Table 1 shows the diaphragm, lens, radius of curvature (R: mm), interval (D: mm), refractive index (N), and dispersion value (corresponding to each surface number of the imaging lens in Example 1. v).

  Table 2 shows aspherical coefficients of predetermined surfaces of the first lens 211, the second lens 212, the third lens 214, and the fourth lens 215 including the first aspherical surface in Example 1. In Table 2, k is a conic constant, A is a fourth-order aspheric coefficient, B is a sixth-order aspheric coefficient, C is an eighth-order aspheric coefficient, and D is a tenth-order aspheric coefficient. Represents. Α and β are phase plane coefficients, and x and y are directions shown in FIG.

(Example 2)
Tables 3 and 4 show the numerical values of Example 2. Each numerical value in the example corresponds to the imaging lens unit 110B in FIG. Table 3 shows the diaphragm, the lens, the radius of curvature (R: mm), the interval (D: mm), the refractive index (N), and the dispersion value (corresponding to each surface number of the imaging lens in Example 2. v).

  Table 4 shows aspheric coefficients of predetermined surfaces of the first lens 211, the second lens 212, the third lens 214, and the fourth lens 215 including the aspheric surface in Example 2. In Table 4, k is a conic constant, A is a fourth-order aspheric coefficient, B is a sixth-order aspheric coefficient, C is an eighth-order aspheric coefficient, and D is a tenth-order aspheric coefficient. Represents. Α and β are phase plane coefficients, and x and y are directions shown in FIG.

  Tables 5 and 6 show examples of refractive index fluctuations depending on the linear expansion coefficient.

This shows that when the temperature changes, the refractive index variation of the resin is much larger than that of glass.
From the above, when the second lens 212 is made of resin, the second lens power of the second embodiment is suppressed even when the refractive index fluctuation due to temperature occurs, so that the fluctuation of the back focus position due to temperature can be reduced. .

  In this embodiment, as shown in Examples 1 and 2, it is possible to realize an imaging lens unit with excellent imaging performance.

  Hereinafter, the configuration and function of the optical system and the image processing apparatus according to the present embodiment will be specifically described.

Next, filter processing of the image processing apparatus 240 will be described.
In the present embodiment, the optical lens regularly disperses the light beam converged by the optical system 210. By inserting this phase plate, an image that does not fit anywhere on the image sensor 220 is realized.
In other words, the optical system 210 forms a deep luminous flux (which plays a central role in image formation) and a flare (blurred portion).
As described above, means for restoring the regularly dispersed image to a focused image without moving the optical system 210 by digital processing is a wavefront aberration control optical system system or a depth extension optical system system (DEOS). : Depth Expansion Optical
This processing is performed in the image processing apparatus 240.

Here, the basic principle of DEOS will be described.
As shown in FIG. 12, when the subject image f enters the DEOS optical system H, a g image is generated.
This is expressed by the following equation.

(Equation 3)
g = H * f
However, * represents convolution.

  In order to obtain the subject from the generated image, the following processing is required.

(Equation 4)
f = H-1 * g

Here, the kernel size and calculation coefficient regarding H will be described.
Let the zoom positions be ZPn, ZPn-1,. In addition, each H function is defined as Hn, Hn-1,.
Since each spot image is different, each H function is as follows.

The difference in the number of rows and / or the number of columns in this matrix is the kernel size, and each number is the operation coefficient.
Here, each H function may be stored in a memory, and the PSF is set as a function of the object distance, and is calculated based on the object distance. By calculating the H function, an optimum object distance is obtained. It may be possible to set so as to create a filter. Alternatively, the H function may be directly obtained from the object distance using the H function as a function of the object distance.

  In this embodiment, as shown in FIG. 3, an image from the optical system 210 is received by the image sensor 220 and input to the image processing device 240 when the aperture is opened, and a conversion coefficient corresponding to the optical system is acquired. The image signal having no dispersion is generated from the dispersion image signal from the image sensor 220 with the acquired conversion coefficient.

  In the present embodiment, DEOS can be employed to obtain high-definition image quality, and the optical system can be simplified and the cost can be reduced.

  FIG. 13 shows the shape of the wavefront aberration expressed by the following equation, where the optical axis of the optical system including the light wavefront modulation element of this embodiment is the z axis and two axes orthogonal to each other are x and y.

In the range where the wavefront aberration is 0.5λ or less, the phase change is small, and the OTF is the same as that of a normal optical system. Therefore, the mounting position is adjusted by narrowing down until the wavefront aberration is about 0.5λ.
FIG. 14 shows the shape of the wavefront aberration and the range of 0.5λ or less by a bold line.
However, λ uses, for example, wavelengths in the visible light region and the infrared region.

  The shape shown in FIG. 13 is an example, and the phase of the light wavefront modulation element is represented by the following equation when the optical axis of the optical system is the z axis and the two axes orthogonal to each other are x and y. Anything is applicable.

  As described above, the image processing apparatus 240 receives the primary image FIM from the image sensor 220 and performs a process of extending the depth of field by a convolution process using a filter to form a high-definition final image FNLIM. .

  The configuration and processing of the image processing apparatus 240 will be described.

  As illustrated in FIG. 3, the image processing apparatus 240 includes a raw (RAW) buffer memory 241, a convolution calculator 242, a kernel data storage ROM 243 as a storage unit, and a convolution control unit 244.

  The convolution control unit 244 controls the convolution process on / off, the screen size, the replacement of kernel data, and the like, and is controlled by the control device 290.

The kernel data storage ROM 243 stores kernel data for convolution calculated from the point image intensity distribution (PSF) of each optical system prepared in advance as shown in FIG. 15, FIG. 16, or FIG. The exposure information determined at the time of setting the exposure is acquired by the control device 290, and the kernel data is selected and controlled through the convolution control unit 244.
The exposure information includes aperture information.

  In the example of FIG. 15, the kernel data A is data corresponding to the optical magnification (× 1.5), the kernel data B is data corresponding to the optical magnification (× 5), and the kernel data C is data corresponding to the optical magnification (× 10).

  In the example of FIG. 16, the kernel data A is data corresponding to the F number (2.8) as aperture information, and the kernel data B is data corresponding to the F number (4). The F number (2.8) and F number (4) are outside the range of 0.5λ described above.

  In the example of FIG. 17, the kernel data A is data corresponding to the object distance information of 100 mm, the kernel data B is data corresponding to the object distance of 500 mm, and the kernel data C is data corresponding to the object distance of 4 m.

FIG. 18 is a flowchart of a switching process based on exposure information (including aperture information) of the control device 290.
First, exposure information (RP) is detected and supplied to the convolution control unit 244 (ST101).
In the convolution control unit 244, the kernel size and numerical performance coefficient are set in the register from the exposure information RP (ST102).
The image data captured by the image sensor 220 and input to the two-dimensional convolution operation unit 242 via the AFE 230 is subjected to a convolution operation based on the data stored in the register, and is calculated and converted. The transferred data is transferred to the camera signal processing unit 250 (ST103).

  A more specific example of the signal processing unit and kernel data storage ROM of the image processing apparatus 240 will be described below.

FIG. 19 is a diagram illustrating a first configuration example of the signal processing unit and the kernel data storage ROM. For simplification, AFE and the like are omitted.
The example of FIG. 19 is a block diagram when a filter kernel corresponding to exposure information is prepared in advance.

  Exposure information determined at the time of exposure setting is acquired, and kernel data is selected and controlled through the convolution control unit 244. The two-dimensional convolution operation unit 242 performs convolution processing using kernel data.

FIG. 20 is a diagram illustrating a second configuration example of the signal processing unit and the kernel data storage ROM. For simplification, AFE and the like are omitted.
The example of FIG. 20 is a block diagram in the case where a noise reduction filter processing step is provided at the beginning of the signal processing unit, and noise reduction filter processing ST1 corresponding to exposure information is prepared in advance as filter kernel data.

Exposure information determined at the time of exposure setting is acquired, and kernel data is selected and controlled through the convolution control unit 244.
In the two-dimensional convolution operation unit 242, after applying the noise reduction filter ST1, the color space is converted by the color conversion process ST2, and then the convolution process ST3 is performed using the kernel data.
The noise process ST4 is performed again, and the original color space is restored by the color conversion process ST5. The color conversion process includes, for example, YCbCr conversion, but other conversions may be used.
Note that the second noise processing ST4 can be omitted.

FIG. 21 is a diagram illustrating a third configuration example of the signal processing unit and the kernel data storage ROM. For simplification, AFE and the like are omitted.
The example of FIG. 21 is a block diagram when an OTF restoration filter corresponding to exposure information is prepared in advance.

Exposure information determined at the time of exposure setting is acquired, and kernel data is selected and controlled through the convolution control unit 244.
The two-dimensional convolution operation unit 242 performs the convolution process ST13 using the OTF restoration filter after the noise reduction process ST11 and the color conversion process ST12.
Noise processing ST14 is performed again, and the original color space is restored by color conversion processing ST15. The color conversion process includes, for example, YCbCr conversion, but other conversions may be used.
Note that only one of the noise reduction processes ST11 and ST14 may be performed.

FIG. 22 is a diagram illustrating a fourth configuration example of the signal processing unit and the kernel data storage ROM. For simplification, AFE and the like are omitted.
The example of FIG. 22 is a block diagram in the case where a noise reduction filter process step is included and a noise reduction filter corresponding to exposure information is prepared in advance as filter kernel data.
Note that the second noise processing ST4 can be omitted.
Exposure information determined at the time of exposure setting is acquired, and kernel data is selected and controlled through the convolution control unit 244.
In the two-dimensional convolution operation unit 242, after performing the noise reduction filter process ST21, the color space is converted by the color conversion process ST22, and then the convolution process ST23 is performed using the kernel data.
The noise process ST24 corresponding to the exposure information is performed again, and the original color space is restored by the color conversion process ST25. The color conversion process includes, for example, YCbCr conversion, but other conversions may be used.
The noise reduction process ST21 can be omitted.

  The example in which the two-dimensional convolution calculation unit 242 performs the filtering process according to only the exposure information has been described above. For example, the calculation coefficient suitable for combining subject distance information, zoom information, or shooting mode information and exposure information. Can be extracted or calculated.

  FIG. 23 is a diagram illustrating a configuration example of an image processing apparatus that combines subject distance information and exposure information.

  As shown in FIG. 23, the image processing apparatus 400 includes a convolution apparatus 401, a kernel / numerical calculation coefficient storage register 402, and an image processing calculation processor 403.

In this image processing apparatus 400, the image processing arithmetic processor 403 that obtains the information about the approximate distance of the object distance of the subject read from the object approximate distance information detection apparatus 500 and the exposure information, performs an appropriate calculation on the object separation position. The kernel size and its calculation coefficient used in the above are stored in the kernel and numerical calculation coefficient storage register 402, and an appropriate calculation is performed by the convolution device 401 that calculates using the value to restore the image.
In this example, the distance to the main subject is detected by the object approximate distance information detection device 500 including the distance detection sensor, and different image correction processing is performed according to the detected distance.

The above image processing is performed by convolution calculation. To realize this, for example, one type of convolution calculation coefficient is stored in common, and a correction coefficient is stored in advance according to the focal length, The correction coefficient is used to correct the calculation coefficient, and an appropriate convolution calculation can be performed using the corrected calculation coefficient.
In addition to this configuration, the following configuration can be employed.

  The kernel size and the convolution calculation coefficient itself are stored in advance according to the focal length, the convolution calculation is performed using the stored kernel size and calculation coefficient, and the calculation coefficient according to the focal length is stored in advance as a function. In addition, it is possible to employ a configuration in which a calculation coefficient is obtained from this function based on the focal length and a convolution calculation is performed using the calculated calculation coefficient.

  When associated with the configuration of FIG. 23, the following configuration can be adopted.

At least two or more conversion coefficients corresponding to the aberration caused by the resin lens corresponding to the phase plate are stored in advance in the register 402 as the conversion coefficient storage means according to the subject distance. The image processing arithmetic processor 403 functions as a coefficient selection unit that selects a conversion coefficient according to the distance from the register 402 to the subject based on information generated by the object approximate distance information detection device 500 serving as a subject distance information generation unit. .
Then, the convolution device 401 as the conversion unit converts the image signal using the conversion coefficient selected by the image processing arithmetic processor 403 as the coefficient selection unit.

Alternatively, as described above, the image processing calculation processor 403 as the conversion coefficient calculation unit calculates the conversion coefficient based on the information generated by the object approximate distance information detection device 500 as the subject distance information generation unit, and stores it in the register 402. Store.
Then, the convolution device 401 as the conversion unit converts the image signal by the conversion coefficient obtained by the image processing calculation processor 403 as the conversion coefficient calculation unit and stored in the register 402.

Alternatively, at least one correction value corresponding to the zoom position or zoom amount of the zoom optical system 210 is stored in advance in the register 402 serving as a correction value storage unit. This correction value includes the kernel size of the subject aberration image.
Then, based on the distance information generated by the object approximate distance information detection device 500 serving as the subject distance information generating unit, the image processing arithmetic processor 403 serving as the correction value selecting unit transmits information from the register 402 serving as the correction value storing unit to the subject. Select a correction value according to the distance.
The convolution device 401 as the conversion unit performs image processing based on the conversion coefficient obtained from the register 402 as the second conversion coefficient storage unit and the correction value selected by the image processing arithmetic processor 403 as the correction value selection unit. Perform signal conversion.

As described above, according to the present embodiment, the optical system 210 and the image sensor 220 that form a primary image, and the image processing device 240 that forms the primary image into a high-definition final image, include the optical system. 210 includes a first lens 211, a second lens 212, a diaphragm 213, a third lens 214, and a fourth lens 215. The first lens 211, the third lens 214, and the fourth lens 215 are made of glass. The second lens 212 is made of resin, and the power of the resin lens is set to be smaller than the power of the glass lens and smaller than the power of the optical system 210. Even if the temperature extends from high to low, sufficient performance can be ensured, and the depth-of-field temperature change can be mitigated in the depth expansion optical system. . In the present embodiment, the case where only the second lens 212 is a resin lens has been described. However, one or more of the second to fourth lenses are resin lenses, and the power of each resin lens is a glass lens. The same effect can be obtained if the total power of the resin lens is made smaller than the power of the optical system.
Although the number of lenses other than the four lenses in the present embodiment may be used, the first lens 211 (the lens on the object side) may come into contact with an object or outside air, so that scratches and corrosion can be prevented. For this purpose, a glass lens is preferable. Furthermore, since the fourth lens (the lens on the imaging element side) is also a glass lens, the resin lens is sealed in the glass lens and the lens barrel, so that the environmental resistance effect can be improved.

  In the lens frame structure units 300 and 300A in the present embodiment, the lens holding unit 310 and the image sensor holding unit 320 are configured separately, and the lens holding unit 310 and the image sensor holding unit 320 are interposed by the intermediate member 330. The fixed position of the lens holding unit 310 and the image sensor holding unit 320 can be adjusted by the intermediate member 330. By controlling this fixed position, the back focus position shift is controlled and the usage environment is focused on low temperature to high temperature. Sufficient performance can be secured even if it meets various needs. Furthermore, in DEOS (depth extension optical system), the temperature change of the depth of field can be reduced.

Also, by making the kernel size used in the convolution calculation and the coefficient used in the numerical calculation variable, knowing from the input of the operation unit 280, etc., and making the appropriate kernel size and the above-described coefficients correspond, the magnification and defocus range There is an advantage that the lens can be designed without worrying about the image and that the image can be restored by convolution with high accuracy.
Further, there is an advantage that a natural image can be obtained without requiring an optical lens that is difficult, expensive, and large in size, and without driving the lens.
The imaging apparatus 200 according to the present embodiment can be used in a DEOS optical system in consideration of the small size, light weight, and cost of consumer devices such as digital cameras and camcorders.
Further, the configuration of the optical system 210 can be simplified, manufacturing becomes easy, and cost reduction can be achieved.

By the way, when a CCD or CMOS sensor is used as an image sensor, there is a resolution limit determined by the pixel pitch, and if the resolution of the optical system exceeds the limit resolution, a phenomenon such as aliasing occurs, which adversely affects the final image. It is a well-known fact that
In order to improve image quality, it is desirable to increase the contrast as much as possible, but this requires a high-performance lens system.

However, as described above, aliasing occurs when a CCD or CMOS sensor is used as an image sensor.
Currently, in order to avoid the occurrence of aliasing, the imaging lens apparatus uses a low-pass filter made of a uniaxial crystal system to avoid the occurrence of aliasing.
The use of a low-pass filter in this way is correct in principle, but the low-pass filter itself is made of crystal, so it is expensive and difficult to manage. Moreover, there is a disadvantage that the use of the optical system makes the optical system more complicated.

As described above, in order to form a high-definition image, the optical system must be complicated in the conventional imaging lens apparatus in spite of the demand for higher-definition image due to the trend of the times. . If it is complicated, manufacturing becomes difficult, and if an expensive low-pass filter is used, the cost increases.
However, according to this embodiment, the occurrence of aliasing can be avoided without using a low-pass filter, and high-definition image quality can be obtained.

  Also, the kernel data storage ROMs in FIGS. 15, 16, and 17 are not necessarily used for the values of optical magnification, F number, the size of each kernel, and the object distance. Also, the number of kernel data to be prepared is not limited to three.

1 is an external view showing an example of an information code reading device according to an embodiment of the present invention. It is a figure which shows an example of an information code. It is a block which shows the structural example of the imaging device applied to the information code reader of FIG. It is a figure which shows the basic composition of the imaging lens unit which forms the optical system which concerns on this embodiment. FIG. 4 is a defocus diagram of an analog spot image in which a resin lens has a strong negative power. FIG. 6 is a defocus diagram of an analog spot image in which a resin lens has a strong positive power. It is a defocus diagram of an analog spot image in which the power of a resin lens is suppressed as in the optical system of the present embodiment. It is a figure which shows the structural example of the lens-frame structure part which concerns on this embodiment. It is FIG. 1 for demonstrating the fixing method of the lens-frame structure part which concerns on this embodiment. It is FIG. 2 for demonstrating the fixing method of the lens-frame structure part which concerns on this embodiment. 6 is a diagram illustrating a basic configuration of an imaging lens unit according to Embodiment 2. FIG. It is a figure for demonstrating the principle of DEOS. It is a figure which shows the shape of the wavefront aberration represented by a type | formula, when the optical axis of the optical system containing the optical wavefront modulation element of this embodiment is set to az axis, and two mutually orthogonal axes are set to x and y. It is the figure which represented the shape of the wavefront aberration and the range below 0.5 (lambda) with the thick line. It is a figure which shows an example (optical magnification) of the storage data of kernel data ROM. It is a figure which shows the other example (F number) of the storage data of kernel data ROM. It is a figure which shows the other example (F number) of the storage data of kernel data ROM. It is a flowchart which shows the outline | summary of the optical system setting process of an exposure control apparatus. It is a figure which shows the 1st structural example about a signal processing part and a kernel data storage ROM. It is a figure which shows the 2nd structural example about a signal processing part and a kernel data storage ROM. It is a figure which shows the 3rd structural example about a signal processing part and kernel data storage ROM. It is a figure which shows the 4th structural example about a signal processing part and kernel data storage ROM. It is a figure which shows the structural example of the image processing apparatus which combines subject distance information and exposure information. It is a figure which shows typically the structure and light beam state of a general imaging lens apparatus. FIG. 25A is a diagram showing a spot image on the light receiving surface of the imaging element of the imaging lens device of FIG. 24, where FIG. 24A shows a case where the focal point is shifted by 0.2 mm (Defocus = 0.2 mm), and FIG. In the case (Best focus), (C) is a diagram showing each spot image when the focal point is shifted by -0.2 mm (Defocus = -0.2 mm).

Explanation of symbols

  DESCRIPTION OF SYMBOLS 200 ... Imaging device, 210 ... Optical system, 211 ... 1st lens, 212 ... 2nd lens, 213 ... Aperture, 214 ... 3rd lens, 215 ... 4th Lens ... 220 ... Image sensor 230 ... Analog front end unit (AFE) 240 ... Image processing device 250 ... Camera signal processing unit 280 ... Operation unit 290 ... Control Device, 242 ... Convolution calculator, 243 ... Kernel data ROM, 244 ... Convolution control unit, 300 ... Lens frame structure unit, 310 ... Lens holding unit, 320 ... Imaging Element holding part, 330... Intermediate member, 332 to 334.

Claims (11)

A fixed-focus optical system including glass and resin lenses;
An image sensor that images a subject image that has passed through the optical system;
A lens frame structure section for holding the optical system and the imaging device;
The lens frame structure is
A lens holding unit for holding each lens of the optical system;
An image sensor holding unit for holding the image sensor,
An imaging apparatus capable of selecting and fixing the lens holding unit and the imaging element holding unit from a plurality of positions having different positions in the optical axis direction. If the back focus is longer than the normal temperature due to the temperature condition in which the lens unit composed of the optical system, the image sensor, and the lens frame structure is used without changing the back focus at normal temperature, the image sensor side The imaging apparatus according to claim 1, wherein when the back focus is shorter than normal temperature, the object side can be selected and fixed from the plurality of positions. If the sum of the powers of the resin lenses included in the optical system is negative and the back focus is short at a temperature higher than normal temperature, the object side is selected and fixed from the plurality of fixing points, and the back focus is lower than normal temperature. The imaging device according to claim 1, wherein when the length is long, the imaging device side is selected and fixed from the plurality of fixing points. When the sum of the power of the resin lenses included in the optical system is positive and the back focus is longer than normal temperature, the image sensor side is selected and fixed from the plurality of fixed locations, and the back focus is lower than normal temperature. The imaging apparatus according to claim 1, wherein if the distance is short, the object side is selected from the plurality of fixing points and fixed. The lens frame structure is
One end side fixes the lens holding portion, and the other end side has an intermediate member capable of fixing the image sensor holding portion,
The imaging apparatus according to claim 1, wherein a fixed position between the lens holding unit and the imaging element holding unit can be adjusted by the intermediate member. The optical system is
The imaging device according to any one of claims 1 to 5, wherein the power of the resin lens is set smaller than the power of the glass lens, and the power of the resin lens is set lower than the power of the optical system. . The subject dispersion image picked up by the image pickup device is an image that is not focused on the image pickup device and has a deep light flux and a blurred portion, and an image signal that is less dispersed than the subject dispersion image signal from the image pickup device. The imaging device according to claim 1, further comprising: an image processing unit that generates The optical system is
A first lens on the object side;
Including at least a second lens disposed closer to the image sensor than the first lens;
The imaging device according to claim 1, wherein the first lens is formed of a glass lens, and the second lens is formed of a resin lens. The optical system is from the object side,
The first lens, the second lens, the third lens, and the fourth lens are sequentially arranged,
The imaging device according to any one of claims 1 to 8, wherein the first lens is formed of a glass lens, and at least the second lens of the second, third, and fourth lenses is formed of a resin lens. The optical system has a light wavefront modulation function, and when the light wavefront modulation function has the optical axis of the optical system as a z-axis and two axes orthogonal to each other as x and y, the phase is expressed by the following equation. The imaging apparatus according to any one of claims 1 to 9.

An imaging device according to claim 1;
An information code decoder unit for decoding an image signal of an information code imaged and processed by the imaging device;
An information code decoding unit for decoding an image signal of an information code imaged and processed by the imaging device;
A data transmission unit that transmits the decoded data to an external data processing device.

Images