Patent ID: 12216301

DETAILED DESCRIPTION

The following detailed description refers to the accompanying drawings that show, by way of illustration, specific details and aspects in which the present disclosure may be practiced. These aspects are described in sufficient detail to enable those skilled in the art to practice the present disclosure. Various aspects are provided for devices, and various aspects are provided for methods. It will be understood that the basic properties of the devices also hold for the methods and vice versa. Other aspects may be utilized and structural, and logical changes may be made without departing from the scope of the present disclosure. The various aspects are not necessarily mutually exclusive, as some aspects can be combined with one or more other aspects to form new aspects.

The present disclosure relates to apparatuses and methods for inspection of embedded features.

A present apparatus may include a light source configured to emit light to a translucent material and an embedded feature disposed in the translucent material, a first linear polarizer configured to linearly polarize the emitted light, based on a first orientation of an optical axis of the first linear polarizer, and a second linear polarizer configured to filter the light that is reflected from the translucent material, from the light that is reflected from the embedded feature and the translucent material, based on a second orientation of an optical axis of the second linear polarizer. The apparatus further includes a sensor configured to receive the light reflected from the embedded feature, from which the light reflected from the translucent material is filtered, and capture an image of the embedded feature and the translucent material, based on the received light.

In another aspect, a method pursuant to the present disclosure may include emitting, by a light source, light to a translucent material and an embedded feature disposed in the translucent material, linearly polarizing, by a first linear polarizer, the emitted light, based on a first orientation of an optical axis of the first linear polarizer, and filtering, by a second linear polarizer, the light that is reflected from the translucent material, from the light that is reflected from the embedded feature and the translucent material, based on a second orientation of an optical axis of the second linear polarizer. The method further includes receiving, by a sensor, the light reflected from the embedded feature, from which the light reflected from the translucent material is filtered, and capturing, by the sensor, an image of the embedded feature and the translucent material, based on the received light.

In yet another aspect, an apparatus may include emitting means for emitting light to a translucent material and an embedded feature disposed in the translucent material, first filtering means for linearly polarizing the emitted light, based on a first orientation of an optical axis of the first filtering means, and second filtering means for filtering the light that is reflected from the translucent material, from the light that is reflected from the embedded feature and the translucent material, based on a second orientation of an optical axis of the second linear polarizer. The apparatus further includes capturing means for receiving the light reflected from the embedded feature, from which the light reflected from the translucent material is filtered, and capturing an image of the embedded feature and the translucent material, based on the received light.

The above-detailed aspects may significantly increase contrast in an image of a semiconductor device by transmitting light in an NIR spectrum (e.g., having a wavelength in a range from about 700 nanometers (nm) to 1700 nanometers) through a translucent material, e.g., an organic substrate included in the semiconductor device, and by filtering scattered light using partially-crossed linear polarizers. Further, measurement and/or detection uncertainties may be greatly improved by considering machine design (sensor orientation) to leverage a full potential of machine vision libraries (subpixeling algorithms). These aspects may improve inspection and measurement of dimensional properties of one or more embedded features included in the semiconductor device, which may allow process control on EMIB, ODI and hybrid bonding products.

FIG.1is a diagram of an apparatus100for inspecting embedded features, according to aspects of the present disclosure.

Referring toFIG.1, the apparatus100is an NIR polariscope including a light source110, a waveguide120, focusing optics130, linear polarizers140, a fold mirror150, a beam splitter160, an objective170, a reflecting layer180and a sensor190.

A polariscope is a device that uses two linear polarizers (one on each end of an optical path) to filter out specific types of light. Here, the apparatus100receives and evaluates a light beam path after it is reflected from a semiconductor device.

The light source110generates and emit light rays111to the waveguide120. The emitted light rays111may be NIR light rays, e.g., having a wavelength in a range from about 700 nm to about 1700 nm. In an embodiment, the emitted light rays111have a wavelength of about 1100 nm. Advantageously, the NIR light rays may penetrate deep into the semiconductor device (e.g., an organic material) with little scattering, yet be reflective off at least one feature that is embedded deep in the semiconductor device, which will be further discussed with respect toFIGS.2A,2B,3A and3B.

The waveguide120guides the emitted light rays111to a first one of the focusing optics130.

The first one of the focusing optics130focuses the guided light rays111onto a first one of the linear polarizers140. The focusing optics130may include any type of, e.g., lens and curved mirrors.

The first one of the linear polarizers140may linearly polarize the focused light rays111, based on a first orientation of an optical axis of the first one of the linear polarizers140. The first orientation of the first one of the linear polarizers140may be tunable by a user of the apparatus100, to improve contrast in an image of the semiconductor device, which will be further described with respect toFIG.4.

The fold mirror150reflects the linearly-polarized light rays111to the beam splitter160.

The beam splitter160splits the reflected light rays111into first light rays111A and second light rays111B. The first light rays111A are directed toward the objective170, and the second light rays111B are directed in a same direction as that of the reflected light rays111.

The objective170gathers and focuses the first light rays111A in a light beam shape112A, and transmits the first light rays111A to a semiconductor device113. The light beam shape112A may be very structured.

In an example, the semiconductor device113may include an organic material114(a substrate) disposed on the reflecting layer180, a semiconductor die115embedded in the organic material114, metal layers116(e.g., gold layers) disposed on the semiconductor die115, nonhomogeneous material117disposed in the organic material114, and at least one embedded feature118embedded in the organic material114. The organic material114may include an ABF or a DAF, and be translucent or semi-transparent. The semiconductor die115may be formed of silicon. The nonhomogeneous material117may be formed of any material that comes from production and strengthening of the organic material114, such material including, e.g., fibers and/or balls of material bonded in a resin. The at least one embedded feature118may include a fiducial for aligning semiconductor die115in the organic material114, and may be in any shape, e.g., circular, rectangular or square.

The transmitted first light rays111A may include light rays111C and111D. The light ray111C may be incident on a portion or piece of the nonhomogeneous material117, and may be split into multiple light rays that are incident on the at least one embedded feature118. The light ray111D may be incident on the reflecting layer180.

The reflecting layer180holds the semiconductor device113, and may reflect light rays incident on the reflecting layer180, e.g., the light ray111D. In examples, the reflecting layer180may include a semiconductor manufacturing stage or a bare silicon wafer.

A light ray111E corresponding to the light ray111D may be reflected off the reflecting layer180, and light rays111F and111G corresponding to the multiple light rays into which the light ray111C is split may be reflected off the at least one embedded feature118. The light ray111G may be incident on a portion or piece of the nonhomogeneous material117, and may be split into multiple light rays.

The objective170gathers and focuses the light rays111E and111F and the multiple light rays into which the light ray111G is split, in a light beam shape112B, and transmits these light rays as light rays111H to the beam splitter160. The light beam shape112B may be broader than the light beam shape112A, which would decrease a contrast or an ability to resolve features in an image of the semiconductor device113without further processing.

The beam splitter160allows the light rays111H to pass through the beam splitter160to the second one of the linear polarizers140.

The second one of the linear polarizers140may filter the light rays111H, based on a second orientation of an optical axis of the second one of the linear polarizers140. The light rays111H may be filtered by filtering and maintaining a polarization of specular reflection from a top surface of the organic material114, while allowing through and altering a polarization of diffusive reflection from the embedded feature118. The light rays that are filtered may include scattered light and extraneous reflected light from the semiconductor device113. The second orientation of the second one of the linear polarizers140may be tunable by the user of the apparatus100, to improve contrast in the image of the semiconductor device113, which will be further described with respect toFIG.4.

A second one of the focusing optics130focuses the filtered light rays111H onto the sensor190.

The sensor190receives the focused light rays111H, and captures the image of the semiconductor device113, using the received light rays111H. The user may use the captured image of the semiconductor device113to analyze the semiconductor device113, namely, the at least one embedded feature118therein. The sensor190may be positioned or oriented at different angles with respect to the at least one embedded feature118, to improve pixilation of the image of the semiconductor device113, which will be further described with respect toFIG.5.

FIG.2Ais an image of a semiconductor die210and an ABF220that are captured using an optical microscope.FIG.2Bis a graph of grey values along a line230on the ABF220ofFIG.2A.

Referring toFIGS.2A and2B, on the line230, a pixel position240is on the ABF220, a pixel position250is on an embedded feature270, and a pixel position260is on the ABF220. Starting from the pixel position240on the ABF220, the grey values are high until around the pixel position250on the embedded feature270, at which the grey values are low. The grey values become high again when the line230is on the ABF220again, until the pixel position260on the ABF220. The semiconductor die210is shown in black.

FIG.3Ais an image of a semiconductor die310and an ABF320that are captured using the apparatus ofFIG.1.FIG.3Bis a graph of grey values along a line330on the ABF320ofFIG.3A.

Referring toFIGS.3A and3B, on the line330, a pixel position340is on the ABF320, a pixel position350is on an embedded feature370, and a pixel position360is on the ABF320. Starting from the pixel position340on the ABF320, the grey values are low until around the pixel position350on the embedded feature370, at which the grey values are high. The grey values become low again when the line330is on the ABF320again, until the pixel position360on the ABF320. The semiconductor die310is shown in dark grey instead of black, and metal layers380(e.g., gold layers) disposed on the semiconductor die310are shown in darker grey.

Referring toFIGS.2A-3B, because the apparatus100uses NIR light having a longer wavelength than light that is used in the optical microscope, there is less scattered light, and the embedded feature370ofFIG.3Ais imaged with sharper, more contrasting edges than the embedded feature270ofFIG.2A. This is further demonstrated inFIG.3Bby sharper transitions between the grey values of the ABF320and the grey values of the embedded feature370, in comparison toFIG.2B. Also, the ABF320is optically most transparent within an NIR light band.

Additionally, because the apparatus100uses the linear polarizers140, light reflected from a top surface of an ABF is suppressed or filtered, while a large portion of light reflected from an embedded feature is allowed therethrough, increasing contrast between surface types, e.g., the ABF and the embedded feature within the ABF. This results in more consistent grey values within each embedded feature (e.g., a higher signal-to-noise ratio), like the grey values of the embedded feature370ofFIGS.3A and3B, in comparison to the grey values of the embedded feature270ofFIGS.2A and2B. Also, the metal layers380may be seen in the image ofFIG.3A, but a metal layer cannot be seen in the image ofFIG.2A.

FIG.4are images of semiconductor dies410,420and430and ABFs440,450and460that are captured using NIR polariscopes including linear polarizers that are uncrossed, partially crossed and fully crossed, respectively, according to aspects of the present disclosure.

Referring to portion (a) ofFIG.4, the image is captured using the NIR polariscope including the linear polarizers that are uncrossed or having the same orientation. That is, a difference of orientations of the linear polarizers is zero, specular reflection from a top surface of the ABF440is mainly unfiltered, and diffusive reflection from an embedded feature470is partially filtered. Polarized light that is presented by a first linear polarizer to a semiconductor device is returned unchanged and therefore unblocked by a second linear polarizer prior to imaging. In an image of a polariscope, a pixel intensity is a function of captured light, so brighter pixels means a polarization of the light was somehow altered by the semiconductor device, e.g., scattering, birefringent material, etc. Thus, in the image of portion (a), while the semiconductor die410and metal layers (e.g., gold layers) therein may be seen, it may be difficult to see the ABF440and the embedded feature470therein. The embedded feature470in the ABF440is washed out in relative pixel variation by excellent contrast in the metal layers.

Referring to portion (b) ofFIG.4, the image is captured using the NIR polariscope including the linear polarizers that are partially crossed. That is, a second linear polarizer included in a beam path of light rays reflected off a semiconductor device is rotated to be 70 degrees different than a first linear polarizer included in a beam path of light rays from a light source. Thus, in the image, the semiconductor die420and metal layers (e.g., gold layers) therein may still be seen, and the ABF450and an embedded feature480therein may be seen with sharper, more contrasting edges. Thus, the linear polarizers may be tuned to be partially crossed to capture an optimized image in which all features of the semiconductor device may be seen clearly with sufficient sharpness and contrast. This allows measurement of dimensional properties of the embedded feature480, the ABF450and the semiconductor die420.

Referring to portion (c) ofFIG.4, the image is captured using the NIR polariscope including the linear polarizers that are fully crossed. That is, a second linear polarizer included in a beam path of light rays reflected off a semiconductor device is rotated to be 90 degrees different than a first linear polarizer included in a beam path of light rays from a light source. As a result, most or all polarized light that is presented by the first linear polarizer to the semiconductor device is returned blocked or filtered out by the second linear polarizer. Thus, in the image, while the ABF460and an embedded feature490therein may be seen with sharper, more contrasting edges, it may be difficult to see the semiconductor die430and metal layers (e.g., gold layers) therein. All or most light from the metal layers is blocked, and contrast suffers in features of the semiconductor die430.

Referring again toFIG.1, light is scattered as it travels through the nonhomogeneous material117included in the organic material114. The linear polarizers140aid in rejecting this scattered light. This is why sharpness and contrast of an embedded feature included in an ABF increases as a difference angle between linear polarizers increases toward 90 degrees, as shown in portions (a)-(c) ofFIG.4. Further, reflections off a primary surface of the semiconductor device113are increasingly rejected as a difference angle between the linear polarizers140increases toward 90 degrees. This is why less light is received from a semiconductor die as the difference angle between the linear polarizers increases toward 90 degrees, as shown in portions (a)-(c) ofFIG.4.

Accordingly, the angles of the linear polarizers140may be tuned by the user of the apparatus100to compromise between high image contrast of the semiconductor die115and high image contrast of the at least one embedded feature118included in the organic material114. In an example, a difference angle between the linear polarizers140of 10-20 degrees may provide a good compromise to see both the semiconductor die115and the at least one embedded feature118. The difference angle between the linear polarizers140may be determined and optimized based on a design of each semiconductor device.

FIG.5are images of ABFs510and520and embedded features530and540therein that are captured using NIR polariscopes including NIR sensors disposed at different angles with respect to the embedded features530and540, according to aspects of the present disclosure.

In a semiconductor device, square-type or rectangular-type fiducials may be used instead of traditional circular-type fiducials. This may affect accuracy of placing a semiconductor die into an organic material for the semiconductor device. Referring toFIG.5, the same rectangular-type fiducial or embedded feature is imaged in two different orientations.

Referring to portion (a) ofFIG.5, the image is captured using the NIR polariscope including the NIR sensor disposed at a first angle with respect to the embedded feature530. In detail, edges (e.g., leftmost and/or rightmost) of pixels of the NIR sensor may be aligned with corresponding edges (e.g., leftmost and/or rightmost) of the embedded feature530so that the first angle between the edges of the pixels and the corresponding edges of the embedded feature530may be approximately zero degrees. The embedded feature530appears highly pixelated. Most consequential, because a pixel resolution of the embedded feature530is not very high, a pixel size may be comparable to a size of the embedded feature530, and thus subpixeling algorithms cannot be fully performed on the image. This limits analysis of semiconductor die placement in the ABF510to discrete intervals of pixel distances.

Referring to portion (b) ofFIG.5, the image is captured using the NIR polariscope including the NIR sensor disposed at a second angle with respect to the embedded feature540. In detail, edges (e.g., leftmost and/or rightmost) of pixels of the NIR sensor may be misaligned or placed apart from corresponding edges (e.g., leftmost and/or rightmost) of the embedded feature540so that the second angle between the edges of the pixels and the corresponding edges of the embedded feature530may be 45 degrees. The embedded feature540appears less pixelated than the embedded feature530of portion (a). Thus, subpixeling algorithms can be fully performed on the image because the edges of the misaligned embedded feature540occupy more of the pixels than the corresponding edges of the aligned embedded feature530. The additional occupied pixels provide more datapoints for the subpixeling algorithms, namely, edge detection calculation.

Referring again toFIG.1, in an example, the sensor190may adjust its own position or orientation (e.g., angle) with respect to the semiconductor device113, namely, the at least one embedded feature118. In another example, the reflecting layer180may adjust a position or an orientation (e.g., angle) of the semiconductor device114(e.g., the at least one embedded feature118) with respect to the sensor190. In both examples, an angle between edges of pixels of the sensor190and corresponding edges of the at least one embedded feature118may be adjusted to be closer to 45 degrees.

FIG.6is a flow diagram of a method600of inspecting embedded features, according to aspects of the present disclosure.

Referring toFIG.6, in operation610, the method600includes emitting, by a light source, light to a translucent material and an embedded feature disposed in the translucent material.

In operation620, the method600includes linearly polarizing, by a first linear polarizer, the emitted light, based on a first orientation of an optical axis of the first linear polarizer.

In operation630, the method600includes filtering, by a second linear polarizer, the light that is reflected from the translucent material, from the light that is reflected from the embedded feature and the translucent material, based on a second orientation of an optical axis of the second linear polarizer. The difference between the first orientation of the first linear polarizer and the second orientation of the second linear polarizer may be in a range from 10 degrees to 20 degrees. The first orientation of the first linear polarizer and the second orientation of the second linear polarizer may further be tunable based on the captured image of the embedded feature and the translucent material.

In operation640, the method600includes receiving, by a sensor, the light reflected from the embedded feature, from which the light reflected from the translucent material is filtered.

In operation650, the method600includes capturing, by the sensor, an image of the embedded feature and the translucent material, based on the received light.

The method600may further include adjusting, by the sensor, an orientation of the sensor with respect to the embedded feature so that an angle between edges of pixels of the sensor and corresponding edges of the embedded feature is about 45 degrees.

The method600may further include adjusting, by a reflecting layer, an orientation of the embedded feature with respect to the sensor so that an angle between edges of pixels of the sensor and corresponding edges of the embedded feature is about 45 degrees.

The methods and sequence of steps presented above are intended to be examples for inspecting embedded features, according to the present disclosure. It will be apparent to those ordinary skilled practitioners that the foregoing process operations may be modified without departing from the spirit of the present disclosure.

FIG.7Ais a diagram of the apparatus100for inspecting embedded features, using an angular distribution of light, according to aspects of the present disclosure.FIG.7Bare images of semiconductor dies715,720and725and ABFs730,735and740that are captured using the angular distribution of light ofFIG.7A.

In a dark illumination case, a specular reflection of light that is emitted from an imaging system may reflect mainly off a top surface of materials and not towards a sensor of the imaging system. Meanwhile, a refractive beam of the light may penetrate deeper into the materials and diffusively reflect from an embedded feature due to its rough surface. A large portion of this reflected light may be detected by a sensor.

Thus, referring toFIGS.1and7A, to capture an image with good contrast between the metal layers116disposed on the semiconductor die115and the embedded feature118and good contrast between the organic material114and the embedded feature118, the apparatus100may emit oblique light rays705towards the embedded feature118, while emitting normal light rays710towards another feature disposed adjacent a top surface of the semiconductor device113, e.g., the metal layers116. That is, the apparatus100may emit an angular distribution of light towards the semiconductor device113, based on materials included in the semiconductor device113. The oblique light rays705may be reflected off the embedded feature118at oblique and normal angles, and the normal light rays710may be reflected off the metal layers116at normal angles.

Because the apparatus100emits the angular distribution of light towards the semiconductor device113, the apparatus100may receive adequate light that is reflected from both the metal layers116and the embedded feature118, namely, more light reflected from the embedded feature118, in comparison to the prior art. Thus, an image with good contrast between the metal layers116and the embedded feature118and good contrast between the organic material114and the embedded feature118may be captured.

For example, referring toFIG.7B, portion (a) shows the image of the semiconductor die715and the ABF730captured using the angular distribution of light having a wavelength of about 630 nm, portion (b) shows the image of the semiconductor die720and the ABF735captured using the angular distribution of light having a wavelength of about 860 nm, and portion (c) shows the image of the semiconductor die725and the ABF740captured using the angular distribution of light having a wavelength of about 940 nm. In each of the three images, there is good contrast between fiducials745,750or755disposed on a respective one of the semiconductor dies715,720and725and fiducials760,765or770embedded in a respective one of the ABFs730,735and740, and good contrast between the fiducials760,765or770and the respective one of the ABFs730,735and740. The images further show that the above contrasts increase as the wavelengths used to capture the images increase.

To more readily understand and put into practical effect the present apparatuses and methods, particular aspects will now be described by way of examples. For the sake of brevity, duplicate descriptions of features and properties may be omitted.

EXAMPLES

Example 1 provides an apparatus including a light source configured to emit light to a translucent material and an embedded feature disposed in the translucent material, a first linear polarizer configured to linearly polarize the emitted light, based on a first orientation of an optical axis of the first linear polarizer, and a second linear polarizer configured to filter the light that is reflected from the translucent material, from the light that is reflected from the embedded feature and the translucent material, based on a second orientation of an optical axis of the second linear polarizer. The apparatus further includes a sensor configured to receive the light reflected from the embedded feature, from which the light reflected from the translucent material is filtered, and capture an image of the embedded feature and the translucent material, based on the received light.

Example 2 may include the apparatus of example 1 and/or any other example disclosed herein, for which the apparatus may be configured to emit oblique light rays, among the emitted light, towards the embedded feature

Example 3 may include the apparatus of example 2 and/or any other example disclosed herein, for which the apparatus may be further configured to emit normal light rays, among the emitted light, towards another feature disposed adjacent a top surface of the translucent material

Example 4 may include the apparatus of example 1 and/or any other example disclosed herein, for which a difference between the first orientation of the first linear polarizer and the second orientation of the second linear polarizer may be greater than 0 degrees and less than 90 degrees.

Example 5 may include the apparatus of example 4 and/or any other example disclosed herein, for which the difference between the first orientation of the first linear polarizer and the second orientation of the second linear polarizer may be in a range from 10 degrees to 20 degrees.

Example 6 may include the apparatus of example 1 and/or any other example disclosed herein, for which the first orientation of the first linear polarizer and the second orientation of the second linear polarizer may be tunable based on the captured image of the embedded feature and the translucent material.

Example 7 may include the apparatus of example 1 and/or any other example disclosed herein, for which the sensor may be further configured to adjust an orientation of the sensor with respect to the embedded feature so that an angle between edges of pixels of the sensor and corresponding edges of the embedded feature is greater than 0 degrees.

Example 8 may include the apparatus of example 7 and/or any other example disclosed herein, for which the angle between the edges of the pixels of the sensor and the corresponding edges of the embedded feature may be about 45 degrees.

Example 9 may include the apparatus of example 1 and/or any other example disclosed herein, further including a reflecting layer on which the translucent material is disposed, and configured to adjust an orientation of the embedded feature with respect to the sensor so that an angle between edges of pixels of the sensor and corresponding edges of the embedded feature is greater than 0 degrees.

Example 10 may include the apparatus of example 9 and/or any other example disclosed herein, for which the angle between the edges of the pixels of the sensor and the corresponding edges of the embedded feature may be about 45 degrees.

Example 11 provides a method including emitting, by a light source, light to a translucent material and an embedded feature disposed in the translucent material, linearly polarizing, by a first linear polarizer, the emitted light, based on a first orientation of an optical axis of the first linear polarizer, and filtering, by a second linear polarizer, the light that is reflected from the translucent material, from the light that is reflected from the embedded feature and the translucent material, based on a second orientation of an optical axis of the second linear polarizer. The method further includes receiving, by a sensor, the light reflected from the embedded feature, from which the light reflected from the translucent material is filtered, and capturing, by the sensor, an image of the embedded feature and the translucent material, based on the received light.

Example 12 may include the method of example 11 and/or any other example disclosed herein, further including emitting oblique light rays, among the emitted light, towards the embedded feature

Example 13 may include the method of example 12 and/or any other example disclosed herein, further including emitting normal light rays, among the emitted light, towards another feature disposed adjacent a top surface of the translucent material

Example 14 may include the method of example 11 and/or any other example disclosed herein, for which the difference between the first orientation of the first linear polarizer and the second orientation of the second linear polarizer may be in a range from 10 degrees to 20 degrees.

Example 15 may include the method of example 11 and/or any other example disclosed herein, for which the first orientation of the first linear polarizer and the second orientation of the second linear polarizer may be tunable based on the captured image of the embedded feature and the translucent material.

Example 16 may include the method of example 11 and/or any other example disclosed herein, further including adjusting, by the sensor, an orientation of the sensor with respect to the embedded feature so that an angle between edges of pixels of the sensor and corresponding edges of the embedded feature is about 45 degrees.

Example 17 may include the method of example 11 and/or any other example disclosed herein, further including adjusting, by a reflecting layer, an orientation of the embedded feature with respect to the sensor so that an angle between edges of pixels of the sensor and corresponding edges of the embedded feature is about 45 degrees.

Example 18 provides an apparatus including emitting means for emitting light to a translucent material and an embedded feature disposed in the translucent material, first filtering means for linearly polarizing the emitted light, based on a first orientation of an optical axis of the first filtering means, and second filtering means for filtering the light that is reflected from the translucent material, from the light that is reflected from the embedded feature and the translucent material, based on a second orientation of an optical axis of the second linear polarizer. The apparatus further includes capturing means for receiving the light that is reflected from the embedded feature, from which the light reflected from the translucent material is filtered, and capturing an image of the embedded feature and the translucent material, based on the received light.

Example 19 may include the apparatus of example 18 and/or any other example disclosed herein, for which the difference between the first orientation of the first filtering means and the second orientation of the second filtering means may be in a range from 10 degrees to 20 degrees.

Example 20 may include the apparatus of example 18 and/or any other example disclosed herein, for which the capturing means may be further for adjusting an orientation of the capturing means with respect to the embedded feature so that an angle between edges of pixels of the capturing means and corresponding edges of the embedded feature is about 45 degrees. The apparatus may further include adjusting means for adjusting an orientation of the embedded feature with respect to the capturing means so that the angle between the edges of the pixels of the capturing means and the corresponding edges of the embedded feature is about 45 degrees.

It will be understood that any property described herein for a specific device may also hold for any device described herein. It will also be understood that any property described herein for a specific method may hold for any of the methods described herein. Furthermore, it will be understood that for any device or method described herein, not necessarily all the components or operations described will be enclosed in the device or method, but only some (but not all) components or operations may be enclosed.

The term “comprising” shall be understood to have a broad meaning similar to the term “including” and will be understood to imply the inclusion of a stated integer or operation or group of integers or operations but not the exclusion of any other integer or operation or group of integers or operations. This definition also applies to variations on the term “comprising” such as “comprise” and “comprises”.

The term “coupled” (or “connected”) herein may be understood as electrically coupled or as mechanically coupled, e.g., attached or fixed or attached, or just in contact without any fixation, and it will be understood that both direct coupling or indirect coupling (in other words: coupling without direct contact) may be provided.

While the present disclosure has been particularly shown and described with reference to specific aspects, it should be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the present disclosure as defined by the appended claims. The scope of the present disclosure is thus indicated by the appended claims and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced.